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Biceps Femoris Audio

The biceps femoris is the two-headed, lateral hamstring muscle within the posterior compartment of the thigh. It is the prime mover of knee flexion and also contributes to hip extension. 

Biceps Femoris

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Human Movement Specialist

Lateral: Biceps Femoris (short head and long head)

Introduction to Hamstring (and Adductor) Muscle Anatomy:

Biceps Femoris Self-administered Pin and Stretch

Static Manual Release of the Biceps Femoris

Feelings of biceps femoris muscle pain, tightness, and weakness are not uncommon. Generally, these feelings are the result of hip, sacroiliac joint, or lower extremity issues that should be addressed with an integrated program. For example, often, the feeling of "biceps femoris tightness" is correlated with 

 and gluteus maximus strengthening techniques (e.g., 

This course describes the anatomy and integrated function of the biceps femoris muscle group (a.k.a. the hamstrings, lateral hamstrings, leg biceps, posterior thigh muscles, etc.). This muscle includes two heads, the long head crosses the hip and knee, and the short head crosses only the knee. Both heads are located within the posterior fascial compartment of the thigh, between the lateral and medial intermuscular septa, abutting the lateral intermuscular septum. Research suggests the biceps femoris only accounts for about 3.9% of the total muscle mass of the thigh and is composed primarily of type I muscle fibers.

Both heads perform similar functions at the knee joint, but only the long head crosses the hip joint. Both heads of the biceps femoris are considered the prime mover during knee flexion and tibial external rotation, and the long head of the biceps femoris is a synergist during hip extension and hip external rotation. This course also describes the role of the biceps femoris on knee joint, hip joint, and sacroiliac joint (SIJ) arthrokinematics, fascial integration (sacrotuberous ligament), subsystem integration, and postural dysfunction. For example, the long head of the biceps femoris is part of the 

, which may increase tension in the sacrotuberous ligament, increasing the stiffness of the SIJ (restricting nutation). If the biceps femoris and DLS are over-active, this could excessively increase SIJ stiffness, contributing to an 

, and postural dysfunction (e.g. movement impairment) of the 

Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) must be aware of the 

 function of the biceps femoris for the detailed analysis of human movement, and the development of sophisticated exercise programs and therapeutic (rehabilitation) interventions. For example, altered activity and length of the biceps femoris may contribute to hip pain, hamstring injury, hamstring muscle strain, hip joint impingement, low back pain, knee valgus, knee varus, and knee pain. Altered biceps femoris activity may also result in a relative reduction in gluteus maximus and gluteus medius activity, resulting in a significant decrease in lower body speed, agility, and strength, and a reduction in the effectiveness of resistance training routines intended to improve lower body strength and hypertrophy (bodybuilding). Deeper knowledge of biceps femoris anatomy is essential for optimal assessment, intervention selection, and building a repertoire of biceps femoris-specific techniques.

This course also provides detailed descriptions of etymology, attachments, innervations, joint actions, location, palpation, integrated actions, arthrokinematics, fascial integration, subsystem integration, postural dysfunction, assessment, clinical implications, and interventions.

Asymmetrical Weight Shift Left (no improvement with Heel Rise Modification)

Biceps Femoris Self-administered Static Release

Piriformis Self-administered Static Release

Adductor Magnus Self-administered Dynamic Release

Right Biceps Femoris Static Manual Release

Right Adductor Magnus Static Manual Release

Cadaver dissection of the biceps femoris originating from the biceps femoris originates from the sacrotuberous ligament

 Course Summary: Biceps Femoris

 Biceps Femoris Course Study Guide Cover

Course Study Guide: Biceps Femoris

Course Summary Webinar: Functional Anatomy of the Biceps Femoris

 1630s (adj.), from Latin biceps “having two parts,” literally “two-headed,” from “double” (see 

) + -ceps comb. form of caput “head” (see 

). As a noun meaning “biceps muscle,” from 1640s, so-called for its structure. Despite the -s, it is singular, and classicists insist there is no such word as bicep. (

 1560s, from Latin femur “thigh, the upper part of the thigh,” which is of unknown origin. (

Cross-section of thigh: Including the biceps femoris long head and short head

Cross-section of the Thigh (Note the Biceps Femoris at the bottom of the picture) - http://upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Thigh_cross_section.svg/660px-Thigh_cross_section.svg.png

Etymology of Terms Related to Biceps Femoris

The proximal attachment is located on the distal portion of the sacrotuberous ligament and the posterior portion of the ischial tuberosity.

This muscle shares a common tendon with the semitendinosus (1,2).

The distal attachment of both the long head and short head of the biceps femoris share a common tendon that inserts on the lateral side of the head of the fibula, lateral condyle of the tibia, and deep fascia on the lateral side of the lower leg (1,3).

This muscle is innervated by the tibial nerve, which arises from a branch of the sciatic nerve via the sacral plexus, originating from nerve roots S1, S2, and sometimes L5 or S3 (1,4).

The proximal attachment is located on the lateral lip of the linea aspera, proximal 2/3 of the supracondylar line (with the middle portion of the 

This muscle is innervated by the fibular nerve (also known as the peroneal nerve), which arises from a branch of the sciatic nerve via the sacral plexus, originating from nerve roots L5 – S2 (1,4).

Biceps Femoris Relative Size and Muscle Fiber Type:

The biceps femoris is a fairly small muscle, contributing approximately 3.8% of the total muscle mass of the muscles crossing the thigh. In comparison, the quadriceps muscles contribute approximately 21% (5).

 One study demonstrated that the biceps femoris muscle was composed of a much larger percentage of type I muscle fibers than type II muscle fibers (6).

The attachment and location of the biceps femoris

Attachments, Innervations, Size, and Fiber Type of the Biceps Femoris

The long head of the biceps femoris originates from a tendon shared with the semitendinosus, that invests in the ischial tuberosity, with fibers extending to the sacrotuberous and sacrospinous ligaments. Further, the origin of the long head of the biceps femoris, as well as the semitendinosus and semimembranosus, are enveloped by the fascia lata (deep fascia of the thigh). This fascial sheath arises from the ischial tuberosity, deep to the large 

 muscle, and envelops the thigh. Frequently, a superior bursa is present separating the tendon of the biceps femoris and semitendinosus from the deeper semimembranosus tendon.

 lies deep to the proximal half of the biceps femoris (from a posterior view). Most often the sciatic nerve arises between the piriformis and gemellus superior, deep to the gluteus maximus, and courses deep to the lateral aspect of the biceps femoris and superficial to the adductor magnus for the proximal half of the thigh. Near the middle of the length of the thigh, the sciatic nerve crosses medially, coursing between the semimembranosus and biceps femoris for the distal half of the thigh, until reaching the popliteal vessels at the posterior aspect of the knee and splitting into tibial and fibular branches.

Near the middle of the length of the thigh, the short head of the biceps femoris arises from the lateral lip of the linea aspera, deep to the long head of the biceps femoris, coursing between the long head of the biceps femoris and adductor magnus. This leaves only a small portion of the adductor magnus abutting the medial aspect of the long head of the biceps femoris for the distal half of the thigh. The majority of the medial aspect of the short head of the biceps femoris abuts the semimembranosus and the smaller semitendinosus, and the lateral aspect abuts the lateral intermuscular septum and vastus lateralis.

The distal end of both heads of the biceps femoris invest in a common tendon. This complex tendon invests in several structures at the lateral aspect of the knee joint, discussed below under "Fascial Integration." Further, this tendon is considered the superior/lateral border of the popliteal fossa, coursing over the origin of the lateral gastrocnemius, plantaris muscle, and the popliteus, as it courses to its primary insertion on the fibular head.

A cross-section of the leg highlighting muscles, nerves, arteries, and veins of the thigh

Cross Section of Thigh - https://bedahunmuh.files.wordpress.com/2010/05/thigh-serial-cross-section.jpg

Where Is The Biceps Femoris Located

Ask your partner to assume a prone position.

Palpating the biceps femoris may be easier if the posterior thigh is exposed (e.g. partner pulls their pant leg up to their gluteal fold). This is not mandatory; however, it may aid in visualizing muscle contractions and the borders of structures that are involved in the palpation.

It is likely easiest to identify the biceps femoris by starting with the muscle's insertion (distal attachment at the knee). The large hamstring tendons create the medial and lateral walls of the popliteal fossa of the knee (the depression of the posterior knee). To aid in visualizing these tendons have your partner flex their knee and raise their lower leg off the table. The biceps femoris tendon is the lateral tendon, comprising the lateral wall of the popliteal fossa. Once you have identified the lateral hamstring tendon you can follow this tendon proximally to palpate the belly of the biceps femoris (the lateral hamstring).

Along the medial border of the biceps femoris, it may be differentiated from the semitendinosus and semimembranosus (medial hamstrings) by initiating a biceps femoris contraction with knee flexion and tibial external rotation (foot turn out). Note, that the semitendinosus and semimembranosus will perform tibial internal rotation (foot turn-in). Along the lateral border of the biceps femoris, it may be differentiated from the vastus lateralis by initiating a biceps femoris contraction, or by initiating a vastus lateralis contraction with knee extension. 

Once you have identified the biceps femoris (lateral hamstring) and the semitendinosus and semimembranosus (medial hamstring), you can course your fingers proximally, in the “valley” between these muscles. You will note that the valley becomes more shallow from distal to proximal, as the semitendinosus tendon joins the tendon of the long head of the biceps femoris. If you follow this tendon proximally, it will course underneath the gluteus maximus and up to the ischial tuberosity (the origin of the biceps femoris).

Popliteal Fossa

Palpating the Biceps Femoris

This muscle will perform extension and may contribute to external rotation of the hip

This muscle will perform flexion and tibial external rotation of the knee

This muscle will perform a posterior tilt of the pelvis

This muscle will perform counternutation (extension) via the sacrotuberous ligament in conjunction with a posterior tilt of the pelvis.

 This muscle will perform flexion and tibial external rotation

Special Note: Although the short head of the biceps femoris does not cross the hip, this muscle may contribute to femoral (hip) internal rotation (relative to tibial external rotation) in a closed chain (e.g. leg press or squat).

Both heads of the biceps femoris may contribute to femoral internal rotation, tibial external rotation, and approximation (compression) of the lateral compartment of the knee; which results in deflection of the knee inward ("functional valgus") during closed chain activities. This is a bit of a paradox, as the long head may contribute to external rotation of the femur and bowing-out of the knees during closed chain activities ("functional varus").

Should the long head and the short head of the biceps femoris be treated as two different muscles despite sharing a common tendon?

Could the separate neural innervation imply that the two heads are recruited as part of separate muscular synergies?

Short head of the biceps femoris depicted in orange.

Integrated Function of the Biceps Femoris

A posterior hip dissection notating the continuity of the biceps femoris and sacrotuberious ligament

Arthrokinematics

Joint Actions of the Biceps Femoris

Our understanding of fascia has benefited from an exponential increase in research over the past two decades. This includes more research on its traditional functions as a passive medium that supports, protects, and encapsulates tissues (29), and its capacity to store elastic energy for explosive activity (30,31). This also includes exciting new research that implicates fascia as a medium of communication. Levangin, H. hypothesized that this may occur via electrical, cellular, and/or mechanical signals (32). Histological studies have shown this tissue to be densely innervated by free 

 endings, as well as by Pacinian corpuscles and Ruffini endings (32,33). This inspires consideration of fascia as a sensory organ with a strong link to motion and neuromuscular reflex. Further, Stecco et al. have demonstrated that deep fascia is arranged in layers that may 

 over one another (33). This finding is likely more responsible for inspiring various fascia-specific interventions and is most often referred to when describing fascia’s role in “interpreting” 

Fascia as a Passive Tissue (Traditional Functions):

Fascia as an Active Medium of Communication

 endings, Pacinian corpuscles, and Ruffini endings

May transmit the force of multiple muscles to aid in joint stabilization

Fibroblasts may play a role in increasing 

Image of the fascial system of the body connecting muscles

The fascial network between fascicles of a muscle – http://www.selfcare4rsi.com/images/fascia.jpg

 The long head of the biceps femoris, along with the piriformis, adductor magnus, semitendinosus, semimembranosus, obturator internus, and multifidus invest in the sacrotuberous ligament. Research has demonstrated that contraction of these muscles may increase 

 of the sacrotuberous ligament, which may contribute to 

 and increased stiffness of the sacroiliac joint (SIJ), and resist sacral 

 (7-11, 34). Tom Myers notes a continuity between the fascia of the sacrotuberous ligament, 

 in his hypothesized "Superficial Back Line" (35), Vleeming et al. notes the relationship between the sacrotuberous ligament, 

 in his "Deep Longitudinal Subsystem" (36), and the Brookbush Institute expands on Vleeming et al. by adding the piriformis and 

 head of the adductor magnus to this subsystem in the course 

Muscle attachments on the femur

The origin of the short head of the biceps femoris and a large portion of the insertion of the 

 have neighboring attachments on the linea aspera of the femur. Additionally, the insertion of the adductor brevis and adductor longus, and the origin of the vastus muscles invest around the attachments of the adductor magnus and short head of the biceps femoris. It may be interesting to research the fascial continuity between these structures, how the contraction of one or more muscles may affect creep and fascial stiffness, and how the contraction of one or more muscles changing facial creep and stiffness may affect the activity or force output of other muscles in the group. Additional research may highlight a neural relationship between the biceps femoris and adductor magnus, as the majority of the adductors are innervated by the obturator nerve, but the adductor magnus and biceps femoris are innervated by the fibular nerve (arising from the sciatic nerve).Tom Myers notes a continuity between the fascia of the short head of the biceps femoris and a large portion of the insertion of the 

in his hypothesized "posterior spiral line" (35). And, the Brookbush Institute adds the adductor magnus to the 

, expanding on Vleeming et al.'s original DLS which already included the biceps femoris (36).

The biceps femoris muscle attachments on the pelvis, femur, and fibula

Note the two potential communicating facial lines of the Biceps Femoris (long head and short head) - http://www.drdooleynoted.com/wp-content/uploads/2015/04/IMG_3258.jpg

Fascial Network of the Lateral Thigh and Knee 

– The iliotibial band and lateral intermuscular septum invest in a complicated fascial network at the lateral knee:

The biceps femoris, tensor fascia lata (TFL), and vastus lateralis (VL) invest in these fascial structures, potentially resulting in a complex myofascial synergy. Research has yet to investigate this potential myofascial synergy; however, the biceps femoris and TFL increase tension in these fascial structures while contributing to tibial external rotation (feet turn out) and functional valgus (knees bow in). Further, this synergy may contribute to external rotation force and posterior glide of the proximal fibular head which may have a significant effect on ankle mechanics. Note, that this is due to the posterior glide of the proximal fibula head resulting in the anterior glide of the distal fibula head, which may reduce ankle mobility. Clinically, it seems common to identify trigger points in the biceps femoris and TFL in individuals exhibiting these signs, while simultaneously identifying trigger points in the VL. Admittedly, the high prevalence of these trigger points (37) would not explain VL release techniques resulting in improvement in excessive tibial external rotation or knee valgus, since the VL cannot directly contribute to tibial external rotation. However, these outcomes could be explained by over-activity of the VL increasing tension in this complex lateral thigh and knee fascial structure. Further research is needed to determine whether there is a myofascial relationship between these structures and whether loss of extensibility or an increase in tension is correlated with altered lower extremity motion. Tom Myers notes a fascial continuity between the TFL, vastus lateralis, and fibular head, and also includes the biceps femoris within the hypothesized "spiral line" (35), and the Brookbush Institute includes this "lateral thigh and knee myofascial synergy" in the systematic review and course "Predictive Model of 

Note, individuals with diagnoses such as iliotibial band syndrome (ITBS), or patellofemoral pain syndrome (PFPS) will attain some relief of symptoms following "foam rolling of the iliotibial band," but fascial structures cannot develop trigger points (this is a muscular phenomenon), suggesting they are targeting VL trigger points.

Long head and short head of the biceps femoris via the ischial tuberosity

Long head and short head of biceps femoris via http://www.rvuanatomy.com/uploads/1/3/4/5/13457421/pf3b_animated.gif

Deep longitudinal subsystem including the sacrotuberous ligament, biceps femoris, and fibularis longus

Core Subsystem Integration and the Biceps Femoris

Fascial Integration and the Biceps Femoris

Biceps femoris EMG activity is likely to be higher during leg curls when compared to hip extension exercises, higher during hip extension dominant exercises (e.g. deadlifts) when compared to triple-extension exercises (e.g. squats), higher during hip extension exercises when the knee is closer to full extension when compared to the knee in a flexed position, and higher when lower extremity strength exercises include hip or tibia external rotation forces. Unstable environments may increase biceps femoris EMG activity during lunges, but not squats, and only if a similar load is lifted. Additionally, biceps femoris EMG activity likely increases with an increase in intensity or eccentric load during lower body power exercise (e.g. depth jumps increase EMG activity more than box jumps).

Exercises in Order of Biceps Femoris EMG Activity (Most to Least):

 A forward lean during gait, whether occurring during "natural" walking or cued postures, results in a significant increase in hip and ankle moments, and a significant increase in biceps femoris and gastrocnemius EMG activity.

Comparing Knee, Hip, and Lumbar Motion Exercises:

 Hamstring EMG activity is likely to be higher during leg curls than during hip extension exercises, higher during hip extension dominant exercises (e.g. deadlifts) than triple-extension exercises (e.g. leg press), and may be higher during hip extension exercises when the knee is closer to full extension (e.g. Roman chair back extensions compared to seated back extensions, or Romanian deadlifts compared to good mornings). Further, an increase in semitendinosus EMG activity relative to biceps femoris EMG activity may be exhibited during prone leg curls, prone leg curls with hip internal rotation, and good mornings, and a relative increase in biceps femoris activity may be exhibited during straight leg hip extension, 45° incline back extensions, and unilateral hip extension. Note, the author suspects these changes in the relative amount of biceps femoris and medial hamstring EMG activity are related to tibia and/or hip rotation forces.

Biceps femoris EMG activity during a bridge or hip thrust can be reduced by decreasing the knee angle, pressing through the heel with the ankle dorsiflexed, and/or supporting the torso via the upper back (when compared to supporting the torso via the low back).

Comparing Hip Thrusts, Squats, and Deadlifts: 

Biceps femoris EMG activity is higher during barbell deadlifts than hex bar deadlifts, hip thrusts, or squats. Additionally, gluteus maximus EMG activity is likely to be higher during hip thrusts than squats or deadlifts, and vastus lateralis EMG activity is likely to be higher during hip thrusts, squats, or hex bar deadlifts than straight bar deadlifts.

Research suggests that the EMG activity of the gluteus maximus and biceps femoris may be similar when squats and rear-foot elevated lunges are compared with a load pre-determined by a relatively heavy rep max (e.g. > 4-RM loads); however, a trend is implied that EMG activity will be higher during rear-foot elevated lunges (a.k.a. Bulgarian split squats). Quadriceps-to-hamstring EMG activity ratio is likely to be higher during squats when compared to lunges. Research also suggests that unstable surfaces added to a squat may not change EMG activity; however, unstable surfaces added to a rear-foot elevated lunge may increase or decrease EMG activity. During rear-foot elevated lunges, the addition of an unstable surface with a similar load will increase EMG activity; however, if the load is decreased to add an unstable surface, EMG activity may decrease. Finally, when accommodating unstable surfaces, men are likely to exhibit a larger increase in hamstring EMG activity, and women are likely to exhibit a larger increase in quadriceps activity.

 Biceps femoris and gluteus maximus EMG activity may be higher during squats when compared to leg press, and higher with a wider stance when compared to a narrow stance; however, squat depth (and potentially load) are unlikely to alter biceps femoris EMG activity. Note, the combination of squatting deep (below parallel) and heavier loads (85% of 1-RM or more) may increase gluteus maximus and gastrocnemius EMG activity.

Biceps femoris EMG activity likely increases with an increase in intensity or eccentric load during lower body power exercise (e.g. depth jumps increase EMG activity more than box jumps).

Studies have compared muscle activity, including activity of the biceps femoris, during gait with forward and backward leans. Preece et al. compared 20 young males and females (age: 26 + 7 years) with no history of back or lower limb pain during a walking assessment. Participants were instructed to walk along a 6-meter walkway at a self-selected pace, 5 trials/posture, with 4 walking postures (self-selected neutral, 5° backward lean, 5° forward lean, and 10° forward lean). Outcome measures included hip and knee kinematics, co-contraction activity profiles of the quadriceps, hamstrings, and calf muscles, and EMG activity of the vastus lateralis, vastus medialis, biceps femoris, semitendinosus, medial gastrocnemius, and lateral gastrocnemius. The findings demonstrated that the 5° and 10° forward lean postures resulted in an increase in hip and ankle moments when compared to the neutral and 5° backward lean walking positions. The 5° and 10° forward lean postures also resulted in a significant increase in EMG activity of the biceps femoris, semitendinosus, and gastrocnemius, and an increase in the co-contraction of the vastus medialis and medial gastrocnemius, vastus medialis and semitendinosus, and vastus lateralis and biceps femoris when compared to the neutral and 5° backward lean walking positions (38). Alghamdi et al. compared 35 healthy adult men and women (age: 28 + 12 years), 18 with a forward lean (trunk flexion) and 17 with a backward lean. "Leans" were determined based on the participant's "natural" walking posture. The forward lean group exhibited an average of 4.8° of trunk flexion (range 3.3° to 7.1°), and the backward lean group exhibited an average of 0.2° of trunk extension (range 1.5° to −3.7°). 6 participants were assessed as having "no lean" and were discarded from the study. All participants performed barefoot walking for 7 trials of 6 meters at a self-selected pace. Outcome measures included hip and ankle moments and EMG activity of the vastus lateralis, vastus medialis, biceps femoris, semitendinosus, medial gastrocnemius, and lateral gastrocnemius. The findings demonstrated the forward lean group exhibited significantly larger hip extensor moments, a 33% increase in EMG activity of the biceps femoris, and a 45% increase in EMG activity of the lateral gastrocnemius (39). These studies demonstrate that foward lean during gait, whether occurring during "natural" walking or cued postures, results in a significant increase in hip and ankle moments, and a significant increase in biceps femoris and gastrocnemius EMG activity.

Comparing Knee, Hip, and Lumbar Motion Exercises

Several studies compared the EMG activity of various muscles during variations of knee, hip, and lumbar motion strength training exercises. Stein et al. compared 15 healthy men (age: 27.0 + 6.4 years) with at least 1 year of resistance-training experience, and no illness or injury that would impede the performance of lower body strength exercise. All participants performed 3 resistance training exercises (unilateral leg press, leg extensions, and cable kickbacks), left leg only, for 2 reps, 80% 1 RM loads, a slow (2.5:0:2.5) tempo, and a moderate (2 min) rest between each exercise. Outcome measures included EMG activity of the gluteus maximus, biceps femoris, vastus lateralis, vastus medialis, and rectus femoris. The findings demonstrated that the gluteus maximus and vastus lateralis exhibited the most, and similar EMG activity during leg press and cable kickbacks. Additionally, biceps femoris EMG activity was highest during cable kickbacks, and rectus femoris EMG activity was highest during leg extensions (40). Lim compared 32 healthy males and females (age: 20.8 + 1.3 years) with no history of hip or knee injury or surgery. All participants performed prone knee flexion and supine straight-leg hip extension with neutral hip rotation. Participants were then randomly assigned to a group performing supine straight-leg hip extensions with hip internal rotation or hip external rotation. Outcome measures included hip extension force, knee flexion force, and EMG activity of the biceps femoris. The findings demonstrated that hip extension force was similar for neutral, internally rotated, and externally rotated hip positions during the supine straight-leg hip extension. Prone leg curls exhibited higher hamstring EMG activity than all variations of the straight-leg hip extensions, and hip internal rotation resulted in an increase in semitendinosus EMG activity when compared to biceps femoris EMG activity (41). Anderson et al. compared 15 resistance-trained females (age: 22 + 1 year) with no history of lower extremity injury during 3 exercises. All participants performed Roman chair back extensions, seated machine back extensions, and Romanian deadlifts for 3 reps, 6-RM loads, using a controlled tempo, with long (4 min) rest between each exercise. Outcome measures included EMG activity of the erector spinae, gluteus maximus, and biceps femoris. The findings demonstrated that erector spinae EMG activity was similar for all 3 exercises, gluteus maximus EMG activity was higher for Romanian deadlifts and Roman chair back extensions when compared to seated back extensions, and biceps femoris EMG activity was higher for Roman chair back extensions when compared to Romanian deadlifts and least for seated back extensions (42). Hegyi et al. compared 19 young male amateur athletes (age: 26.1 + 3.2 years) with no history of lower extremity injury, lower back injury, musculoskeletal disorders, or cardiovascular disorders. All participants performed 9 hamstring exercises in random order, including unilateral Romanian deadlifts, good mornings, single-leg cable kickbacks, single-leg bent-knee hip bridges, straight-leg hip bridges, single-leg back extensions at 45° incline, prone leg curls, and cable slider leg curls for 1 set, 6 reps, 12-RM loads, a slow (2:0:2) tempo, and long (4 min) rest between sets. Outcome measures included EMG activity of the long head of the biceps femoris and semitendinosus. The findings demonstrated a relative increase in biceps femoris EMG activity compared to semitendinosus EMG activity during concentric and eccentric phases of a single-leg back extension at 45° incline and unilateral hip extension. A relative increase in semitendinosus EMG activity compared to biceps femoris EMG activity was exhibited during the eccentric phase of a good morning, and during the concentric phase of a prone leg curl. The largest increase in hamstring EMG activity (both biceps femoris and semitendinosus) occurred during the straight‐knee hip bridge, upright hip extension, and leg curls (43). In summary, hamstring EMG activity is likely to be higher during leg curls than during hip extension exercises, higher during hip extension dominant exercises (e.g. deadlifts) than triple-extension exercises (e.g. leg press), and may be higher during hip extension exercises when the knee is closer to full extension (e.g. Roman chair back extensions compared to seated back extensions, or Romanian deadlifts compared to good mornings). Further, an increase in semitendinosus EMG activity relative to biceps femoris EMG activity may be exhibited during prone leg curls, prone leg curls with hip internal rotation, and good mornings, and a relative increase in biceps femoris activity may be exhibited during straight leg hip extension, 45° incline back extensions, and unilateral hip extension. Note, the author suspects these changes in the relative amount of biceps femoris and medial hamstring EMG activity are related to tibia and/or hip rotation forces.

Two studies compared the EMG activity of contributing muscles during variations of "Glute Bridges" or "Hip Thrusts". Contreras et al. compared 13 healthy resistance-trained females (age: 28.9 + 5.1 years) with the ability to hip thrust a 10-RM load of 87.4 + 19.3 kg. All participants performed 3 variations of a hip thrust, including the barbell hip thrust (bench on upper back), banded hip thrust, and American hip thrust (bench on lower back), for 1 set, 10 reps, 10-RM load, and a long (5 min) rest between variations. Outcome measures included EMG activity of the gluteus maximus, biceps femoris, and vastus lateralis. The findings demonstrated that gluteus maximus, biceps femoris, and vastus lateralis EMG activity were similar during the barbell and American hip thrust. Gluteus maximus EMG activity was significantly lower during banded hip thrusts, and biceps femoris activity was highest during American hip thrusts (44). Lehecka et al. compared 28 healthy males and females (age: 23.43 + 2.28 years) with no history of low back or lower extremity pain. All participants performed 5 variations of a single-leg bridge exercise, including a single-leg hip bridge with the knee flexed to 90° and the foot flat with the contralateral leg extended, a single-leg hip bridge with the knee flexed to 135° and the ankle in full dorsiflexion with the contralateral knee relaxed in flexion and femur held vertically, a single-leg hip bridge with the knee flexed to 135° and foot flat with the contralateral knee extended, a single-leg hip bridge with the knee flexed to 90° and foot flat with the contralateral knee relaxed in flexion and femur held vertically, and a single-leg hip bridge with the knee flexed to 90° and ankle in full dorsiflexion with the contralateral knee relaxed in flexion and femur held vertically. Each variation was performed for 8 reps with a moderate tempo (to a metronome set at 60 bpm). Outcome measures included EMG activity of the gluteus maximus, gluteus medius, rectus femoris, and biceps femoris. The findings demonstrated that biceps femoris EMG activity was the lowest during the single-leg hip bridge with the knee flexed to 135° and the foot dorsiflexed. Further, the findings demonstrated that biceps femoris EMG activity was lower during variations with the knee flexed to 135° when compared to 90°, and with the foot dorsiflexed when compared to the foot flat on the table. Gluteus maximus and gluteus medius EMG activity was highest during the single-leg hip bridge variation with the knee flexed to 135°, the foot flat on the table, and the contralateral knee extended (45). These studies suggest that biceps femoris EMG activity during a bridge or hip thrust can be reduced by decreasing the knee angle, pressing through the heel with the ankle dorsiflexed, and/or supporting the torso via the upper back (when compared to supporting the torso via the low back).

Comparing Hip Thrusts, Squats, and Deadlifts

Additional studies have compared EMG activity during hip thrusts, squats, and deadlifts. Andersen et al. compared 13 healthy men (age: 20-25 years) with 4.5 + 1.9 years of strength training experience. All participants performed straight bar deadlifts, hex bar deadlifts, and hip thrusts for 1-3 sets, 1 rep/set, 1-RM loads, with long (3 - 5 min) rest between exercises. Outcome measures included 1-RM strength and EMG activity of the gluteus maximus, biceps femoris, and erector spinae. The findings demonstrated that 1RM loads were significantly heavier during hip thrusts when compared to straight bar deadlifts and hex bar deadlifts. Further, the findings demonstrated erector spinae EMG activity was similar during the 3 exercises, gluteus maximus EMG activity was highest during the hip thrusts, and biceps femoris EMG activity was highest during the straight bar deadlifts (46). Contreras et al. compared 13 healthy females (age: 28.9 + 5.11 years) with at least 3 years of resistance training experience, and no musculoskeletal or neuromuscular injuries, pain, or illness. All participants performed back squats and hip thrusts in randomized order for 1 set, 10 reps, 10-RM loads, and long (5-min) rest between exercises. This was followed by a 10-min rest and a 3-sec isometric hold in the bottom position of the squat and the top position of a hip thrust (in randomized order with 5-min rest between exercises). The back squats were performed to parallel (tops of thighs parallel to the floor) feet slightly wider than shoulder-width apart, and toes pointed forward (or slightly outward). The barbell hip thrusts were performed with the back approximately 16 inches high, feet slightly wider than shoulder-width apart, and toes forward (or slightly outward). Outcome measures included electromyographic (EMG) activity of the gluteus maximus, biceps femoris, and vastus lateralis. The findings demonstrated that EMG activity of the vastus lateralis was similar during the barbell hip thrust and back squat; however, gluteus maximus and biceps femoris EMG activity was significantly higher during dynamic and isometric barbell hip thrusts (47). Camara et al. compared 30 resistance-trained men (age: 19 - 27 years) with a 1-RM barbell deadlift load of at least 1.5x their body weight. All participants performed barbell deadlifts and hex bar deadlifts in randomized order, 2 sets/exercise, 1 set of 3 reps with 65% 1-RM load, and 1 set of 3 reps at 85% of 1-RM, maximum velocity (MaxV) concentric tempo, moderate (3 min) rest between sets, and long (5 min) rest between exercises. Outcome measures included deadlift 1-RM strength and EMG activity of the biceps femoris, vastus lateralis, and erector spinae (longissimus). The findings demonstrated that 1-RM loads were similar for both deadlift variations. Vastus lateralis EMG activity was significantly higher during the concentric and eccentric phases of the hex bar deadlift, biceps femoris EMG activity was higher during the concentric phase of the barbell deadlift, and erector spinae EMG activity was higher during the eccentric phase of the barbell deadlift (48). These studies suggest that biceps femoris EMG activity is higher during barbell deadlifts than hex bar deadlifts, hip thrusts, or squats. Additionally, gluteus maximus EMG activity is likely to be higher during hip thrusts than squats or deadlifts, and vastus lateralis EMG activity is likely to be higher during hip thrusts, squats, or hex bar deadlifts than straight bar deadlifts.

Comparing Squats to Lunges and Bulgarian Split Squats

There are a relatively large number of studies that compare the EMG activity of various muscles during variations of squats, lunges, and Bulgarian split squats (a.k.a. rear foot elevated lunge). Muyor et al. compared 20 physically active men and women (age: 24 + 5.55 years) with a minimum of 6 months of lower body strength training experience, and no musculoskeletal injuries. Participants performed 3 lower body exercises including barbell lateral step-ups, barbell forward lunges, and barbell single-leg squats for 1 set, 5 reps, 60% of 5-RM loads, at a slow (2:0:2) tempo, with long (3-5 min) rest between exercises. Outcome measures included EMG activity of the biceps femoris, gluteus medius, gluteus maximus, vastus lateralis, vastus medialis, and rectus femoris muscles. The findings demonstrated that all assessed muscles, during all exercises, exhibited higher EMG activity during the concentric phase than the eccentric phase. Further, the single-leg squat resulted in significantly higher EMG activity for all muscles tested when compared to the lateral lunge and forward lunge, except for a larger increase in rectus femoris EMG activity during the forward lunge (49). Jones et al. compared 10 male (age: 21.0+ 0.8 years) college athletes (football, track and field) with a minimum of 1 year of formal collegiate strength and conditioning experience and had been medically cleard for intercollegiate athletic participation. All participants completed 5 testing sessions comparing bilateral back squats and Bulgarian split squats with a 10-RM load, to a depth of 90° of knee flexion, with a slow (3:0:2) tempo, and 5 min rest between trials. Outcome measures included post-exercise serum concentrations of testosterone, and EMG activity of the vastus lateralis, biceps femoris, gluteus maximus, and erector spinae. The findings demonstrated that both exercises resulted in similar EMG activity for all muscles, and following 4 sets of 10 reps, post-exercise serum concentrations of testosterone were similar at 0, 5, 10, 15, and 30 min postexercise (50). McCurdy et al. compared 11 female Division I soccer, softball, and track & field athletes (age: 20.62 + 1.03 years) with no history of anterior cruciate ligament injury, lower extremity muscle strain, knee pain, or current ankle, hip, or back injury. All participants performed a barbell squat and barbell rear foot elevated lunge, for 3 sets (2 warm-up sets and 1 testing set), 1 rep for the testing set, 3-RM loads, with 3 - 5 minutes rest between each set. Outcome measures included average quadriceps-to-hamstring EMG activity ratio and peak EMG activity of the gluteus medius, rectus femoris, and biceps femoris. The findings demonstrated that gluteus medius and biceps femoris EMG activity was significantly higher during the rear foot elevated lunge, rectus femoris EMG activity was significantly higher during barbell squats, and quadricep-to-hamstring EMG ratio was higher during barbell squats (51). Another study by McCurdy et al. compared 18 young adult females (age: 20.92 ± 1.1 years) with previous resistance training experience (1-5 years), not currently participating in sport or resistance training, and without current or previous lower extremity injury that would limit maximum performance on the exercises included in the study. Participants performed bilateral back squats, stiff-legged deadlifts, and Bulgarian split squats for 1 set, of 3 reps, with an 8-RM load during deadlifts, and 3-RM loads during squat variations, with 3-4 minutes rest between trials. Outcome measures included EMG activity of the gluteus maximus and hamstrings. The findings demonstrated that EMG activity of the gluteus maximus was higher than the hamstring for all exercises. EMG activity of the gluteus maximus was highest for the Bulgarian split squats and similar for back squats and straight-leg deadlifts. EMG activity for the hamstrings was highest for the Bulgarian split squat, followed by straight-leg deadlifts, and least for back squats (52). Andersen et al. compared 15 resistance-trained males performing squats and rear-foot elevated lunges on stable and unstable surfaces with a 6-RM load. The outcome measures included EMG activity of the external obliques, rectus abdominis, erector spinae, vasti muscles, rectus femoris, and biceps femoris. The findings demonstrated vasti and rectus abdominis muscle EMG activity was similar for all variations, and the addition of an unstable surface resulted in an average of a 7-10% decrease in load. External obliques and biceps femoris EMG activity was higher, but rectus femoris EMG activity was lower for Bulgarian split squats, when compared to squats. Further, erector spinae and biceps femoris EMG activity was lower when an unstable surface was added to Bulgarian split squats (potentially as a result from reduced load) (53). Last, Youdas et al. compared 30 healthy males and females (age: 22 - 31 years) recruited from a physical therapy graduate program with no knee, hip, or ankle pathology. All participants performed a bodyweight single-leg squat and a bodyweight single-leg squat on an unstable surface for 1 set of 1 rep, using a slow (5:0:5) tempo, with short (1 min) rest between each exercise. Outcome measures included EMG activity of the hamstrings and quadriceps muscles. The findings demonstrated that biceps femoris EMG activity was higher when a single-leg squat was performed on an unstable surface, women exhibited an average of 14% more quadriceps EMG activity (p < 0.04) on a stable surface, and men exhibited an average of 18% more hamstring EMG activity than women on an unstable surface (54). In summary, these studies suggest that the EMG activity of the gluteus maximus and biceps femoris may be similar when squats and rear-foot elevated lunges are compared with a load pre-determined by a relatively heavy rep max (e.g. > 4-RM loads); however, a trend is implied that EMG activity will be higher during rear-foot elevated lunges (a.k.a. Bulgarian split squats). Quadriceps-to-hamstring EMG activity ratio is likely to be higher during squats when compared to lunges. Research also suggests that unstable surfaces added to a squat may not change EMG activity; however, unstable surfaces added to a rear-foot elevated lunge may increase or decrease EMG activity. During rear-foot elevated lunges, the addition of an unstable surface with a similar load will increase EMG activity; however, if the load is decreased to add an unstable surface EMG activity may decrease. Finally, when accommodating unstable surfaces, men are likely to exhibit a larger increase in hamstring EMG activity, and women are likely to exhibit a larger increase in quadriceps activity.

Several studies demonstrate that variations in squat depth, foot position, and load have a significant effect on EMG activity. Escamilla et al. compared 10 healthy resistance-trained men (age: 29.6 + 6.5 years) during squats with 4 different foot positions (4 total squat variations), and leg presses with the same 4 foot positions and 2 different plate positions (8 total leg press variations). The 4 foot positions included a narrow stance with feet parallel, a narrow stance with feet at 30°, a wide stance with feet parallel, and a wide stance with feet at 30°. Participants completed 1 set of each variation, for 4 reps, with 12-RM loads, a controlled (1:1:1) tempo, and long (3-4 min) rest between variations. Outcome measures included knee and lower extremity force, and EMG activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, and gastrocnemius. The findings demonstrated that more force was generated at the knee, and EMG activity was higher for the biceps femoris, vasti muscles, and rectus femoris during all squat variations when compared to all leg press variations. Biceps femoris EMG activity was significantly higher during wide stance leg press when compared to narrow stance leg press, and gastrocnemius EMG activity was higher during narrow stance squats when compared to wide stance squats (55). Contreras et al. compared 13 resistance-trained females (age: 28.9 + 5.1 years) without a history of musculoskeletal or neuromuscular injuries. All participants performed front squats, parallel squats, and below parallel squats (deep squats), for 1 set, 10 reps, 10-RM loads, and long (5 min) rest between sets. Outcome measures included EMG activity of the upper and lower gluteus maximus, biceps femoris, and vastus lateralis. The findings demonstrated the front squats, parallel squats, and below parallel squats (deep squats) resulted in similar EMG activity of the gluteus maximus, biceps femoris, and vastus lateralis (56). Gorsuch et al. compared 10 male (age: 19.2 + 0.4 years) and 10 female (age: 19.9 + 0.4 years) Division I cross country runners with at least 4 years of resistance training experience. All participants performed partial range squats to 45° of knee flexion and parallel squats to 90° of knee flexion for 1 set, of 6 reps, 10-RM loads, a moderate (1:0:1) tempo for partial squats, and a slow (2:0:2) tempo for parallel squats, with long (5 min) rest between variations. The findings demonstrated that 10-RM loads were higher for partial range squats, EMG activity of the biceps femoris and gastrocnemius was similar for both depths, and EMG activity of the rectus femoris and erector spinae was higher for 90° of knee flexion squats (57). Last, Flores et al. compared 14 healthy recreationally trained females (age: 25.3 + 6.4 years) with 4.0 + 2.88 years of squatting experience. All participants performed squats at 3 depths (ROM) including above parallel, parallel, and below parallel, and with 3 different loads including bodyweight, 50% of 1-RM, and 85% of 1-RM loads, for 1 set/protocol (9 sets/total), at a controlled tempo. Outcome measures included EMG activity of the gluteus maximus, biceps femoris, vastus lateralis, and lateral gastrocnemius. The findings demonstrated that the EMG activity of the biceps femoris and vastus lateralis were similar (differences were not statistically significant) at all loads and depths. The EMG activity of the gluteus maximus was highest during above parallel and parallel depths with heavier loads. And, the EMG activity of the lateral gastrocnemius increased with depth at heavier loads (58). These studies suggest biceps femoris and gluteus maximus EMG activity may be higher during squats when compared to leg press, and higher with a wider stance when compared to a narrow stance; however, squat depth (and potentially load) are unlikely to alter biceps femoris EMG activity. Note, the combination of squatting deep (below parallel) and heavier loads (85% of 1-RM or more) may increase gluteus maximus and gastrocnemius EMG activity.

One study was located investigating EMG activity of the biceps femoris during jumping with 3 different eccentric loads. Padulo et al. compared 12 elite-level female volleyball players (age: 24.7 + 3.9 years) with no musculoskeletal or neurological conditions. All participants performed 3 successful trials (2 min rest between exercises) of depth jumps, counter-movement jumps, and squat jumps. The depth jump was performed from a 45cm step and participants landed with both legs in knee flexion at 90°; the counter-movement jump was performed by quickly dropping into knee and hip flexion and immediately jumping as high as possible; and the squat jump was performed starting in a semi-squat position with the knee in 90° and participants were asked to jump using only knee extension. The findings demonstrated that biceps femoris EMG activity was highest during depth jumps, followed by squat jumps, and the least EMG activity was exhibited during the counter-movement jump (59). This study implies that biceps femoris EMG activity likely increases with an increase in intensity or eccentric load during lower body power exercise (e.g. depth jumps increase EMG activity more than box jumps).

Electromyographic (EMG) Research: Contribution of the Biceps Femoris to Exercise and Motion

Knee valgus while landing from a single-leg hop or during an 

, as well as a history of low back pain, sacroiliac joint (SIJ) pain, knee pain, or hamstring injury, are correlated with similar changes in biceps femoris EMG activity. These changes include significantly earlier onset and a relative increase in EMG activity. Additionally, altered biceps femoris EMG activity may be correlated with a delay in the onset of EMG activity of the internal obliques, multifidus, and gluteus maximus.

 resulting in an increase in biceps femoris EMG activity, including earlier onset, higher peak, and higher average EMG activity, implies this muscle should be categorized as over-active. The increase in length noted in those exhibiting an anterior pelvic tilt, excessive forward lean, and/or knee valgus, implies this muscle should also be categorized as long. However, the decrease in length noted in those exhibiting a posterior pelvic tilt, inadequate forward lean, knee varus, tibial external rotation, an asymmetrical weight shift, or increase SIJ stiffness implies this muscle may be categorized as short. These findings suggest that biceps femoris-specific techniques should include 

, that lengthening (e.g. stretching) techniques should be avoided when assessed as long, lengthening (e.g. stretching) techniques may be integrated when assessed as short, and techniques should be avoided that may increase activity (e.g. isolated strengthening).

Low Back and Sacroiliac Joint (SIJ) Pain: 

Low back and SIJ pain result in an earlier onset of biceps femoris electromyographic (EMG) activity during walking and marching, and potentially a delay in the onset of internal obliques, multifidus, and gluteus maximus EMG activity, especially on the symptomatic side.

Patellofemoral Pain Syndrome (PFPS) or Hamstring Injury:

 Patellofemoral pain syndrome and/or hamstring injury result in significantly earlier and higher biceps femoris EMG activity. These studies highlight this altered recruitment during single-leg stance, landing, and pre-activation phases during single-leg hops, even when kinematics are relatively normal.

 These studies demonstrate that knee valgus during single-leg hop landing or the eccentric phase of an 

 is correlated with significantly higher EMG activity of the biceps femoris, adductor magnus, and vastus lateralis.

Studies investigating low back pain, sacroiliac joint (SIJ) pain, and EMG activity suggest altered recruitment of various muscles. Vogt et al. compared 32 males, 17 with low back pain (age: 36.3 + 2.1 years) and 16 with no history of low back pain (age: 33.7 + 3.1 years) while performing treadmill walking, for 20 total strides, at a self-selected walking pace. Outcome measures included hip joint range of motion (ROM), stride times, and EMG activity of the biceps femoris, erector spinae, and gluteus maximus. The findings demonstrated the group with low back pain exhibited shorter stride times, a reduction in hip extension ROM, prolonged EMG activity of the gluteus maximus and erector spinae, and significantly earlier onset of EMG activity of the biceps femoris (60). Hungerford et al. compared 28 men, 14 with clinically diagnosed sacroiliac joint (SIJ) pain (age: 24 - 47 years) and 14 with no history of low back pain, lumbar or pelvic anomalies, and negative (normal) results on straight leg raise and stork tests during hip flexion in standing (age: 22 - 50). Participants performed 5 trials of hip flexion to 90° on the left and right legs (stork test/marching in place). Outcome measures included EMG activity of the adductor longus, biceps femoris, tensor fascia latae (TFL), gluteus medius, gluteus maximus, lumbar multifidus, and internal obliques. The findings demonstrated that the no low back pain group, prior to the initiation of hip flexion, exhibited an increase in EMG activity of the internal oblique and multifidus. After the initiation of motion, EMG activity increased for the gluteus maximus, gluteus medius, TFL, adductor longus, and biceps femoris. Conversely, the group with clinically diagnosed sacroiliac joint (SIJ) pain exhibited a delay in the increase in EMG activity of the internal oblique, multifidus, and gluteus maximus, and an earlier onset of the increase in EMG activity of the biceps femoris. Additionally, this group exhibited a larger delay in the EMG activity of the internal oblique, multifidus, and gluteus maximus on the symptomatic side when compared to the asymptomatic side (61). These studies demonstrate that low back and SIJ pain result in an earlier onset of biceps femoris electromyographic (EMG) activity during walking and marching, and potentially a delay in the onset of internal oblique, multifidus, and gluteus maximus EMG activity, especially on the symptomatic side.

Patellofemoral Pain Syndrome (PFPS) or Hamstring Injury

Two additional studies have investigated EMG activity following a diagnosis of PFPS or hamstring injury. Kalytczak et al. compared 28 female participants (age: 18-35 years), 14 with PFPS, and 14 healthy participants with no history of knee pain. All participants performed 3 consecutive single-leg hops for distance. Outcome measures included peak knee and hip flexion kinematics and EMG activity of the gluteus maximus, gluteus medius, biceps femoris, and vastus lateralis, during the landing and pre-activation phase (prior to the second jump). The findings demonstrated both groups exhibited similar knee and hip kinematics and similar gluteus maximus and gluteus medius EMG activity; however, the PFPS group exhibited significantly higher EMG activity of the biceps femoris and vastus lateralis during the landing and pre-activation phase (62). Sole et al. compared 36 male collegiate athletes, 17 with diagnosed hamstring injuries (age: 24.8±5.2 years), and a control group of 19 with no history of lower leg injuries (age: 22.6 ± 5.0 years), during a marching task. Participants were instructed to lift the left or right leg into 90° hip and knee flexion as fast as possible, in response to a different color light for each leg, then hold the position for at least 30 sec, and then slowly lower the leg. The outcome measures included reaction time and EMG activity (average activity and onset timing) of the gluteus maximus, gluteus medius, vastus lateralis, vastus medialis, rectus femoris, semitendinosus, and biceps femoris. The findings demonstrated that both groups exhibited similar reaction times to the light stimulus, similar EMG activity of the glute and quadriceps muscles, and similar EMG activity of the hamstrings when comparing the uninjured legs of the control group and uninjured side of the hamstring injury group. However, a statistically significant difference was demonstrated by the hamstring injury group, when the previously injured side was the stance leg, including earlier onset and higher average EMG activity of the biceps femoris and semitendinosus (63). These studies demonstrate that PFPS and/or hamstring injury result in significantly earlier and higher biceps femoris EMG activity. These studies highlight this altered recruitment during single-leg stance and landing and pre-activation phases during single-leg hops, even when kinematics are relatively normal.

Two studies have demonstrated that knee valgus results in similar changes in EMG activity as exhibited by individuals with low back, SIJ, or knee dysfunction. Palmieri-Smith et al. compared 21 recreationally active males and females (male age: 23.6 

 5.2 years), with no history of knee surgery, knee pain, or lower extremity injury 6 months prior to the study, during single-leg hopping. Participants performed a 1-meter single-leg forward hop to balance on the ipsilateral leg for five trials. Outcome measures included peak valgus knee angles and EMG activity during the hopping and landing of the vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, and gluteus medius. The findings demonstrated that female participants who landed with higher peak knee valgus angles exhibited higher peak EMG activity of the vastus lateralis and biceps femoris, and lower peak EMG activity of the vastus medialis (64). Dinis et al. compared 22 recreationally active females (age: 18 - 25 years) with no history of lower extremity injury for at least 6 months, assigned to a group that maintained neutral knee alignment or a group that exhibited 

 (OHSA). All participants performed a bodyweight overhead squat with feet shoulder-width apart, toes pointing straight, arms extended overhead, and a depth of 80 degrees of knee flexion, for 1 set of 10 reps, with a slow (2:1:2) tempo. Outcome measures included knee and ankle kinematics and EMG activity of the gluteus maximus, gluteus medius, tensor fascia latae, adductor magnus, biceps femoris, rectus femoris, vastus lateralis, vastus medialis, fibularis longus, gastrocnemius, soleus, and tibialis anterior. The findings demonstrated that during the OHSA the medial knee displacement group exhibited more knee internal rotation, knee valgus, and ankle eversion. Further, both groups exhibited similar EMG activity during the concentric phase of the OHSA, but the medial knee displacement group exhibited significantly higher EMG activity of the adductor magnus, biceps femoris, vastus lateralis, and vastus medialis during the eccentric phase of the overhead squat (65). These studies demonstrate that knee valgus during single-leg hop landing or the eccentric phase of an 

 is correlated with significantly higher EMG activity of the biceps femoris, adductor magnus, and vastus lateralis. Note, that these studies conflict, demonstrating an increase or decrease in the EMG activity of the vastus medialis; however, they are congruent regarding the relative increase in biceps femoris activity.

Electromyographic (EMG) Research: Change in Biceps Femoris Activity with Dysfunction and Pain

 Evidence of a variety of dysfunctions resulting in an increase in biceps femoris EMG activity, including earlier onset, higher peak, and higher average EMG activity, implies this muscle should be categorized as over-active (37 -40, 66). The increase in length noted in those exhibiting an anterior pelvic tilt, excessive forward lean, and/or knee valgus, implies this muscle should also be categorized as long. However, the decrease in length noted in those exhibiting a posterior pelvic tilt, inadequate forward lean, knee varus, tibial external rotation, an asymmetrical weight shift, or increased SIJ stiffness implies this muscle may be categorized as short. These findings suggest that biceps femoris-specific techniques should include release techniques, that lengthening (e.g. stretching) techniques should be avoided when assessed as long, lengthening (e.g. stretching) techniques may be integrated when assessed as short, and techniques should be avoided that may increase activity (e.g. isolated strengthening).

Biceps Femoris

Related Courses:

Course Summary: Biceps Femoris

Course Study Guide: Biceps Femoris

Course Summary Webinar: Functional Anatomy of the Biceps Femoris

Etymology of Terms Related to Biceps Femoris

Attachments, Innervations, Size, and Fiber Type of the Biceps Femoris

Where Is The Biceps Femoris Located

Palpating the Biceps Femoris

Joint Actions of the Biceps Femoris
2 Sub Sections

Fascial Integration and the Biceps Femoris
1 Sub Section

Electromyographic (EMG) Research: Contribution of the Biceps Femoris to Exercise and Motion

Electromyographic (EMG) Research: Change in Biceps Femoris Activity with Dysfunction and Pain

Movement Impairment and the Biceps Femoris
1 Sub Section

Exercises and Techniques for the Biceps Femoris
6 Sub Sections

Additional Materials: Stop Stretching Your Hamstrings!

Sample Intervention

Bibliography

Related Courses:

Comments

Guest

Biceps Femoris

Related Courses:

Course Summary: Biceps Femoris

Course Study Guide: Biceps Femoris

Course Summary Webinar: Functional Anatomy of the Biceps Femoris

Etymology of Terms Related to Biceps Femoris

Attachments, Innervations, Size, and Fiber Type of the Biceps Femoris

Where Is The Biceps Femoris Located

Palpating the Biceps Femoris

Joint Actions of the Biceps Femoris2 Sub Sections

Fascial Integration and the Biceps Femoris1 Sub Section

Electromyographic (EMG) Research: Contribution of the Biceps Femoris to Exercise and Motion

Electromyographic (EMG) Research: Change in Biceps Femoris Activity with Dysfunction and Pain

Movement Impairment and the Biceps Femoris1 Sub Section

Exercises and Techniques for the Biceps Femoris6 Sub Sections

Additional Materials: Stop Stretching Your Hamstrings!

Sample Intervention

Bibliography

Related Courses:

Comments

Guest

Joint Actions of the Biceps Femoris
2 Sub Sections

Fascial Integration and the Biceps Femoris
1 Sub Section

Movement Impairment and the Biceps Femoris
1 Sub Section

Exercises and Techniques for the Biceps Femoris
6 Sub Sections