By Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, H/FS
The muscles that comprise the AOS are the global movers of the anterior trunk and the adductors. This subsystem plays a significant role in stabilizing the thoracic and lumbar spine, sacroiliac joint (SIJ), pubic symphysis and hip, as well as transferring force between lower and upper extremities. The AOS plays an active role in all pushing and rotational movement patterns (especially turning in), multi-segmental flexion, and eccentrically decelerating spinal extension and rotation, as well as hip extension, abduction and external rotation (knees bow in and excessive forward lean). The AOS is the functional antagonist of the Posterior Oblique Subsystems (POS).
The rectus sheath envelopes the rectus abdominis anteriorly and posteriorly. From costal cartilage to the the arcuate line (the level of the umbilicus), the anteriorsheath is comprised of a continuation of the external oblique fascia while the posterior sheath is comprised of a continuation of the internal oblique and transverse abdominis fascia (1). Below the level of the arcuate line the posterior sheath does not continue, and the fascia of the internal obliques, external obliques and transverse abdominis continue anterior to the rectus abdominis. The fusion of the layers of the abdominal fascia below the arcuate line, may serve as a fascial connection between the anterior abdominal fascia of the AOS, and the middle and posterior layers of abdominal fascia of the Intrinsic Stabilization Subsystem (ISS).
The fascial layers of the abdomen converge at the linea alba, where they continue into identical fascial sheaths on the opposite side. The linea alba, running vertically between the two rectus abdominis muscles, is a thickening created by the union of the transverse fibers of the fascial sheaths from either side (2). The transverse inscriptions that run horizontally through the rectus abdominis are also continuations of the oblique fascia (3). In addition, fascia from the sternal fibers of the pectoralis major and the fascia of the serratus anterior invests in the fascia of the external obliques (and sometimes rectus abdominis)(1, 4-7). These findings expand the original description of the AOS as described by Vleeming et al. (1) to include two powerful upper extremity muscles.rectus abdominis, pyramidalis, external obliques, internal obliques, and transverse abdominis activity (recruitment of the AOS and ISS) (2), and may increase quadratus lumborum and psoas activity (7-9). This increase in muscle activity will also increase tension of the abdominal fascia, transverse inscriptions and linea alba. Studies show that force imparted by a trunk muscle will be transmitted between all layers of abdominal fascial network (10, 11). This may imply that muscle recruitment and/or fascial tension may signal an increase in the other. Studies on the amount any muscle can displace a layer of abdominal fascia are not available as they are for the thoracolumbar fascia (TLF) (10); however, Vleeming makes the following analogy (6) – The abdominal fascia features muscles encased in a fascial network, much like the TLF. The paired rectus abdominis muscles are encased in the fascia of investing muscles (transverse abdominis, internal obliques and external obliques). Tension in these muscles increases tension in the abdominal fascia like the latissimus dorsi and gluteus maximus increases tension in the TLF.
Only one study could be located that may imply the efficacy of a technique directed at the abdominal fascia. In this study, deep, slow pressure resulted in a decrease in muscle activity (5). Admittedly, this is not a common or comfortable technique to apply to the abdomen. If manual pressure is applied, a tangential force is recommended to reduce discomfort. No studies could be located that investigated instrument assisted soft tissue mobilization (IASTM) on the abdominal region, but based on the idea that For example, the glide of facet joint in the spine during spinal flexion and extension, or the posterior glide of the humeral head that must accompany anterior roll to maintain congruence with glenoid fossa during shoulder horizontal adduction.">shear
For example, the glide of facet joint in the spine during spinal flexion and extension, or the posterior glide of the humeral head that must accompany anterior roll to maintain congruence with glenoid fossa during shoulder horizontal adduction.">shearbetween layers may be reduced as a result of dysfunction, careful application in practice may be warranted, especially where the layers converge at the semilunar lines and lateral
The rectus abdominis may enhance rigidity or aid in transferring force between left and right sides of the abdominal fascia; however, the relationship between the rectus abdominis and the abdominal fascia has not been well-researched. The proximity and continuity of the rectus abdominis tendon, and the tendon of the adductor longus may be the most significant link between the trunk muscles and adductor muscles that comprise the AOS.
The rectus abdominis is a strong lumbar flexor, also contributing to posterior tilting of the pelvis, and the sacral counter-nutation linked to lumbar flexion (13-15). This muscle may be active during axial rotation and lateral stabilization of the spine (16); however, it is doubtful that this recruitment contributes to rotation and/or side-bending force vectors. It is more likely this activity is a co-contraction with the lumbar erectors to aid in bracing (stabilization of) the lumbar spine (17). This bracing function should not be confused with the type of stabilization demonstrated by the Intrinsic stabilization Subsystem (ISS), which is anticipatory, bilateral, non-direction dependent, and noted even during low intensity tasks. Recruitment of the rectus abdominis is direction specific and related to larger loads (18).
The activity of the rectus abdominis (as well as the external obliques) relative to low back pain and LPHCD is complex. Sway back postures may result in an increase or decrease in activity (19, 20), low back pain may result in decreased rectus abdominis activity during rotation (21), but increased reliance when fatigued (22), low back pain patients generally are weaker in trunk flexion than extension (23); however, they recruit the rectus abdominis more during stair climbing (24), and chronic low back pain patients typically cannot differentiate between transverse abdominis and rectus abdominis activation during the abdominal drawing in maneuver (ADIM) (25). This pattern of simultaneously "more and less" may suggest that the rectus abdominis is compensating for inhibition of primary stabilizers (ISS); a concept referred to as synergistic dominance. Generally, over-active synergists demonstrate an increase in activity due to inhibition of other primary musculature, but less strength due to an increase in length and disruption of optimal length/tension relationship.
Note: The pyramidalis lies between the right and left rectus abdominis, within the anterior rectus sheath at the linea alba. Although it is mentioned in this article, it is only mentioned in an attempt to be comprehensive. This muscle does not play a role in intervention selection or practical application, as it only serves to increase tension in the linea alba, and is absent in 17 - 25% of individuals (26).
The anterior layer of the abdominal fascia is a continuation of the external oblique fascia, which passes superficial to the rectus abdominis, and invests in, or is continuous with the fascia from the contralateral side at the linea alba (27). The external obliques are likely the prime movers for trunk rotation and lateral flexion (16, 28-30), and are active during flexion and forceful expiration (30-32). The recruitment of the external obliques varies significantly from the other muscles of the lateral abdominal wall. The external obliques contribute to contra-lateral rotation of the spine, and do not demonstrate the "bilateral co-activation" often noted in the internal obliques and transverse abdominis during static or dynamic rotation of the trunk (16, 33). Although the external obliques may also contribute to stabilization, they do so in a direction dependent manner (ex. unilaterally active during eccentric deceleration of rotation) (34), and in response to larger loads (bracing) (17). Further, the external obliques are also more active during a posterior pelvic tilt than during the abdominal drawing-in maneuver (ADIM) (35). In fact, their activity is not necessary to increase intra-abdominal pressure (36), which may be attributed to a lack of attachment to the thoracolumbar fascia (37). In short, the external oblique should likely be categorized as a global mover with the rectus abdominis and as a muscles the AOS, where as the internal obliques and transverse abdominis behave like stabilizers and other muscles of the Intrinsic stabilization Subsystem (ISS).
The behavior of the external obliques relative to LPHCD and low back pain resembles that of the rectus abdominis; however, the alterations in activity are easier to predict. Studies show that low back pain and fatigue increase reliance on the external obliques, relative to a decrease in internal obliques and transverse abdominis activity and in some cases rectus abdominis activity (22 - 25, 38). Like the rectus abdominis, the external obliques exhibit less activity in sway standing (19), may be more active (bilaterally) to stabilize the spine (bracing) during functional tasks in those with low back pain, and are more active during exercises requiring more stability (ex. bridges on ball) (19, 39, 40). This behavior implies that in those exhibiting dysfunction, the external obliques become synergistically dominant for an inhibited transverse abdominis and internal obliques; behavior that is most often attributed to muscles that have adopted maladaptive behvior of long and over-active. This behavior and categorization is the same as the rectus abdominis.
The abdominal fascia runs with some continuity from abdomen, through pubic symphysis, into the tendons of the anterior adductors. The strongest fascial relationship likely exists between the tendons of the rectus abdominis and the tendons of the adductor longus muscles. The continuity between the rectus abdominis and the adductor longus can then be expanded upon by location to the tendons of the rest of the anterior adductors. The tendon of the pectineus abuts the lateral side of the rectus abdominis tendon, and the attachments of the gracilis and adductor brevis abut the tendon of the adductor longus inferiorly and laterally.
A few publications support a relationship that includes the sacroiliac joint, pubic symphysis, anterior abdominal activity and adductor activity (1, 42-45). The most direct support in the research to date can be found in a study by Snijders et al.. This study demonstrated that crossing the legs decreased the activity of the internal obliques (45). It is hypothesized that crossing the legs altered adductor activity and force imparted on the pubis, resulting in a reduction in activity by the internal obliques to equalize force on the pubis. Another study worth mentioning investigated altered muscle activity in individuals exhibiting signs of sacroiliac joint pain. In this study, sacroiliac joint dysfunction was correlated with adductor activity that remained unchanged (along with TFL, biceps femoris), which is a relative increase when compared to internal oblique, lumbar multifidus, and gluteus maximus activity that decreased or fired later (42). Although these studies are not direct evidence of a myofascial synergy that includes the abdominal fascia, the studies imply a relationship between the muscles and joints that comprise the AOS.
Over-activity of the adductors has been correlated with functional knee valgus (46-48), hinting at this muscle groups common maladaptive behavior. As mentioned above, individuals with sacroiliac joint dysfunction demonstrated a relative increase in adductor activity during functional tasks (49). Although it may not be a direct indicator of relative changes in length, the adductors (and adductor tendons) are commonly associated with tendonitis and groin pain (50-52), of these muscles the adductor longus seems to be the most often affected (53). Although more research is needed, current evidence suggests these muscles are commonly over-active, and observations in clinic would suggest that this muscle has a propensity to adaptively shorten and restrict mobility.
The most superficial fibers of the sternal head of the pectoralis major invest in the fascia of the external obliques and sometimes the rectus abdominis (4, 54). This inspires consideration of the pectoralis major (and serratus anterior discussed below) as part of the AOS, and the AOS as the primary synergy responsible for generating force during some of the most powerful activities in sports (e.g. throwing a baseball, swing a golf club, chop patterns, lineman pushing, etc.).
Research has demonstrated that the pectoralis major contributes to horizontal adduction and internal rotation, as well as extension and adduction from an arm elevated position (55-58). This includes activities, such as the tennis forehand and serve, the concentric phases of golf swing or baseball pitch, swimming and dumbbell pull-overs (59-64). Several studies have compared dumbbell press, bench press and chest flye variations. Incline press, flat and decline press result in varied recruitment of pectoralis major fibers, with lower fibers (sternal head) being recruited more during a decline press; the clavicular head seems to be recruited similarly at all angles (65-67). Flyes resulted in a shorter recruitment period than pressing movements (68). Unstable environments often result in similar recruitment of the pectoralis major with less external load; however, most studies do not demonstrate that the addition of instability to an exercise increases pectoralis major recruitment (other muscles are often recruited more) (69, 71 -74).
The pectoralis major behaves like a prime mover; that is, it is recruited for the concentric phase of large powerful movements, following the recruitment of smaller stabilizers. In a study by David et al. it was demonstrated that the pectoralis major fired after recruitment of the rotator cuff muscles and the biceps brachii during internal and external rotation, and in a study by Saeterbakken et al. instability during a chest press did not increase pectoralis major activity, but did increase biceps brachii activity (75, 76). In a study by Wang et al. the pectoralis major was more active during concentric internal rotation than eccentric external rotation, and a study by Kronberg et al. demonstrated that the pectoralis major is not active and does not aid in shoulder stabilization during flexion (77, 78). An interesting study by Hirashima et al. demonstrated that overhead throwing followed a proximal to distal recruitment pattern; that is, although the rotator cuff and biceps brachii may fire prior to the pectoralis major, the pectoralis major fires prior to elbow extensors and wrist flexors (79). This study also demonstrated synergy between the external obliques, serratus anterior, and pectoralis major.
The pectoralis major does appear to be one of the few muscles that adopts the maladaptive behavior of short/under-active in those exhibiting dysfunction, supporting the notion of "prime mover inhibition." In two studies that compared pectoralis major activity in those exhibiting signs shoulder dysfunction, the pectoralis major demonstrated less activity (64, 80). However, a study on patients with major rotator cuff tears demonstrated increased pectoralis major activity during flexion, and that activity returned to normal when pain decreased following subacromial injection (70). Although these may be viewed as contradictory findings, it may also imply a role reversal from concentric force producer to eccentric stabilizer. Further, this may be normal activity for an inhibited prime mover; more research is needed. Relative to exercise, the pectoralis major may exhibit more activity than the serratus anterior during pushing motions in those exhibiting scapular winging; however, this activity may be reversed with band resisted abduction during serratus anterior exercise (81, 82).
The superficial fascia of the serratus anterior runs continuous with the fascia of the external obliques, which is continuous with the anterior abdominal fascia (1). This fascial relationship may imply that this important stabilizer and mover of the scapula is part of the AOS, and that the AOS is a synergy responsible for generating power in many explosive upper and lower body sporting activities, e.g. throwing a baseball, swinging a golf club, pushing a defender, etc. (as mentioned under "Pectoralis Major"). An interesting study by Hirashima et al. demonstrated that overhead throwing followed a proximal to distal recruitment pattern that started with contralateral then ipsilateral external obliques, then serratus anterior, then pectoralis major followed by elbow extensors (79). Additional stabilizing muscles were also recruited, but the sequence demonstrated in this study may be the best example of loading and recruiting the AOS during a functional activity.
The serratus anterior is a protractor, upward rotator and posterior tipper. Studies show that the serratus anterior is highly active in the trailing arm of forward swing and throughout back swing during golf (83, 84), works in synchronization with the pectoralis major during a windmill style softball pitch (85) and pushing motions that include protraction (86, 87), and works in syncrhonization with the upper trapezius during the tennis serve (88). These studies suggest that the serratus anterior acts like a prime mover, and in conjunction with other prime movers. However, the serratus anterior is also highly active during all 3 tennis strokes (89), is active continually during all phases of the freestyle stroke during swimming (90, 91), and is active throughout all upper body PNF patterns (92). This continuous activity, regardless of direction of motion, suggests a role in scapular stabilization. These findings suggest that the serratus anterior likely functions as both prime mover and stabilizer of the scapula (along with the trapezius muscles).
The serratus anterior has a propensity toward under-activity in those exhibiting dysfunction. Several studies demonstrate that anterior shoulder pain and/or impingement is correlated with a decrease in serratus anterior activity, including altered timing and decoupling from syncrhonization with the lower trapezius (64, 93-95). A similar decrease is noted in those diagnosed with anterior shoulder instability (96, 97). Both cervical dysfunction and forward head posture also decrease serratus anterior activity (98 - 102), and even lateral epicondylitis has been correlated with scapular dyskinesis (103). This propensity toward under-activity may be a precursor to shoulder dysfunction, as two studies demonstrate that a fatiguing shoulder raise protocol results in scapular dyskinesis and altered activity (103, 104). Could it be that reinforcement of this "fatigue/compensatory pattern" during repetitive daily tasks, causes a shift toward this pattern over time? The under-activity of the serratus anterior is also coupled with an increase in length. Several studies have noted that shoulder dysfunction results in excessive downward rotation, anterior tipping and internal rotation of the scapula, that is, during functional tasks that rely on elevation of the arm, those exhibiting dysfunction exhibit inadequate upward rotation, posterior tipping and maintenance of the scapula against the ribcage (104 - 109).
A variety of interventions affecting the serratus anterior have been researched. Pressing motions, including pressing with "a plus" (protraction), and pressing that requires more or less stability have been well-researched. The largest issue with pressing motions is that many variations of pushing also increase upper trapezius and pectoralis minor activity which may reinforce compensatory patterns discussed above. Wall push-ups, push-ups with a plus, and feet-up push-ups significantly increase upper trapezius activity and punch-ups increase pectoralis minor activity (110 - 113). Unstable pushing motions may be effective for a variety goals; however, it is unlikely that stability progressions will result in a relative increase serratus anterior activity. Bench press actually had a better ratio of serratus anterior to upper trapezius activity than stable and unstable push-ups variations (114). Two studies comparing push-ups to push-ups on a stability ball showed no increase in EMG activity (115, 116), and bench press was shown to increase serratus anterior activity better than either variation (114). Additionally, those exhibiting scapular dyskinesis had less serratus anterior activity and more upper trapezius and pectoralis major activity during pushing, even when a stability ball was added to push-ups (81, 119). The hypothesis that stability training would preferentially recruit the serratus anterior is likely flawed because it does not consider how other muscles may participate in stabilization of the shoulder girdle; however, this does not diminish the use of stability training. Studies have demonstrated that instability increases the activity of other musculature including the anterior deltoid, pectoralis major, trapezius and core musculature (69, 71, 114, 116). The increase in activity of multiple muscles may aid in enhancing inter-muscular coordination, and integration of the AOS, once relative activity has been addressed with release and activation techniques. Interesting note, although unstable environments do not consistently increase serratus anterior EMG, oscillations/vibration training does (117, 118). More systematic experimentation and research is needed to develop easy ways to implement vibration training.
An alternative technique to pressing is scaption (elevation/abduction in the scapular plane). Several studies comparing various "rehabilitation exercises" and motions of the arm showed scaption to create the highest serratus anterior EMG activity (120-128). Further, unlike pressing motions that also increase activity of commonly over-active muscles (upper trapezius and pectoralis minor), scaption pairs the serratus anterior with the commonly under-active lower trapezius (120-126). Scaption should likely be performed through the largest available range (without compensation or pain), as exercise that results in the most upward rotation resulted in the largest increase in serratus anterior activity (128). Additional variations including prone scaption, scaption in quadruped position and wall slides may also be beneficial, but consideration should be given to patient ability and recruitment of additional musculature (123-124).
As mentioned above, those exhibiting scapular dyskinesis had less serratus anterior activity and more upper trapezius and pectoralis major activity during pushing type exercise (81, 119). Further, a study by Lucas et al. demonstrated that addressing latent trigger points in muscles of the scapula, aided in normalizing muscle recruitment patterns, including increased serratus anterior activity (129). This may imply that release techniques for typically over-active muscles, and targeted intervention for the serratus anterior should precede multi-joint movement patterns.
Research implies a relationship that includes the sacroiliac joint, pubic symphysis, anterior abdominal activity and adductor activity (1, 42-45). The most direct support of this relationship is a study by Snijders et al. demonstrating that crossing the legs decreases activity of the internal obliques (45). Another study by Hungerford et al. demonstrated sacroiliac joint dysfunction resulted in a relative increase in adductor, TFL, biceps femoris activity compared to internal oblique, lumbar multifidus, and gluteus maximus activity that decreased or fired later (42). Although this research does not directly investigate the role of the AOS in stabilization of the pelvis and lumbar spine, it implies a relationship between the structures involved that may be explained by its role as a stabilizer.
It may be hypothesized that the AOS is the counter to the Posterior Oblique Subsystem (POS). That is, the AOS aids in bracing and control of the pubic symphysis, pelvis and the lumbar spine from the front, and the POS aids in bracing and control of the SIJ, pelvis and lumbar spine from the back. Note, the term "bracing" is used rather than stabilization, as the AOS and POS are recruited during higher intensity activities to "brace" the lumber spine. "Drawing in" and Intrinsic Stabilization Subsystem (ISS) recruitment should be sufficient for low level activities, and should be synergistic with the AOS and POS during higher intensity activities. This is as analgous to the "size principle" of motor unit recruitment. When load is greater than the capacity of the ISS, the AOS and POS are generally recruited in a direction specific manner to resist additional load. Several studies have demonstrated that the rectus abdominis and external obliques are recruited more in those with low back pain (guarding and ISS impairment), and during higher intensity activity (17, 19, 22, 24, 25, 34, 39, 40).
The AOS may play an important "protective" role, as this subsystem can decelerate rotation and extension of the lumbar and thoracic spine. Further, the AOS is involved in eccentric deceleration of an anterior pelvic tilt, especially during standing and pushing motions (133-135). Lumbar extension, rotation and an anterior pelvic tilt, have been hypothesized to lead to facet joint and posterior disk compression, and have been correlated with low back pain (130-132).
The ability to contribute to eccentric deceleration of shoulder elevation and external rotation, scapular retraction, spine rotation and extension, and hip extension make the AOS the subsystem "loaded" during the "loading phase" of a throw or swing. This may be the best example of loading a myofascial synergy for recoil and optimal power production.
The study by Hirashima et al. (mentioned above) demonstrated proximal to distal recruitment of the AOS during overhead throwing; that is, contralateral then ipsilateral external obliques, followed by serratus anterior, then shoulder stabilizers, and finally pectoralis major and elbow extensors (79). Further, the joint actions described during this motion are a return from the eccentric function of the AOS described above. The majority of this pattern may also seen during pushing a defender, a tennis serve, a volleyball spike, and the butterfly stroke in swimming. The concentric function of this subsystem may imply it is one of the most important to sports performance.
The AOS could be viewed as a system prone to synergistic dominance. In the Brookbush Institute's predictive models of Upper Body Dysfunction (UBD), Lumbo Pelvic Hip Complex Dysfunction (LPHCD), Sacroiliac Joint Dysfunction (SIJD), and Lower Extremity dysfunction (LED) this sub-system is over-active and long. Commonly, the over-activity is paired with under-activity of the Posterior Oblique Subsystem (POS) and may be compensatory for under-activity of the Intrinsic Stabilization Subsystem (ISS). Evidence of AOS dominance may result in knees bow-in, excessive forward lean or arms fall during an Overhead Squat Assessment, and/or an excessive kyphosis, spinal flexion, or an excessive forward lean during an Overhead Squat Assessment with Modification. Dominance of the AOS (and under-activity of the POS) is generally most dramatic in those individuals exhibiting UBD and LED.
Based on available research on individual muscles, the Brookbush Institute's (BI's) predictive models of postural dysfunction, and observations in practice, this subsystem is categorized as "long/over-active". As subsystems are synergies, dynamic multi-segmental postural assessment is recommended for determining compensatory activity, strengthening/activation of individual muscles within the system is avoided, but integrated exercise may be appropriate. The BI uses the research and theory of subsystems as a means of refining core and integrated exercise selection. Note, the BI's Corrective-Template addresses individual structures prior to addressing subsystems to reduce relative flexibility, synergistic dominance and compensatory patterns.
Signs of AOS over-activity is based on the research, concentric function and motor behavior described above, and signs are considered relative to the BI's preferred dynamic postural assessment, the Overhead Squat Assessment (OHSA). Specifically, the AOS contributes concentrically to multi-segmental flexion, as well as hip flexion, adduction and internal rotation implying excessive forward lean and knees bow in are signs of over-activity. Because of the role the AOS plays in core stability and motion an excessive lordosis (anterior pelvic tilt) is a sign of dysfunction; however, this is a sign of increased length that may be addressed with integrated strengthening exercise. The inclusion of the commonly under-active pectoralis major and serratus anterior implies that AOS dysfunction may also contribute to the signs shoulders elevate and arms fall. The role of the AOS in Upper Body Dysfunction (UBD) is complex, leading to a peculiar sign during the Overhead Squat Assessment with Modification. When the hands are placed on the hips (arms down), the lack of support from a lengthened POS exaggerates AOS dominance, leading to an excessive kyphosis, spinal flexion, or an excessive forward lean during re-assessment. Although the exaggerated forward lean looks like Lumbo Pelvic Hip Complex Dysfunction (LPHCD), practice would suggest it is a sign of UBD. In summary, the signs knees bow in, excessive forward lean, excessive lordosis, shoulders elevate, arms fall and Forward Lean during an Overhead Squat Assessment with Modification may imply AOS over-activity.
As mentioned above, the external obliques and rectus abdominis have a propensity to become over-active, but are long in those exhibiting signs of LPHCD. The attributes long/over-active are often a sign of synergistic dominance; it is recommended that muscles in this category are addressed by reducing postural dysfunction to optimize length/tension. Research supports this recommendation - in several studies, bridges and exercises that focused on posterior tilting immediately improved trunk flexor strength and improved recruitment patterns during gait (139-143). Due to the categorization of long/over-active and these research findings the BI recommends avoiding specific strengthening exercises for the external obliques and rectus abdominis while dysfunction persists. Instead, focus on bridges, and chop progressions which may aid in improve posture, optimize length/tension and improve synergy between the AOS and POS.
The BI suggests ending sessions with multi-joint exercise/activities (integrated exercise) to reinforce new motor patterns. The BI refines "integrated exercise" selection with research and theory on subsystems. As mentioned above, over-activity of the adductors has been correlated with knees bow in (62-63, 66). Further it may be implied by function and research that the external obliques and rectus abdominis are over-active in those exhibiting dysfunction (19, 22, 24, 25, 38 - 40), contributing to an excessive forward lean. Based on this research the BI categorizes the AOS as over-active. The Brookbush Institute addresses this issue with “release and avoid.” That is, the muscle and fascial structures that can be released are addressed, and exercises that place emphasis on the AOS are avoided until movement quality improves (example, avoid planks, crunches, leg raises, etc.).
Alternatively, in an anterior pelvic tilt the external obliques and rectus abdominis are long, which creates a puzzling combination of both short and long muscles in the AOS and over-activity through-out. In this case the Brookbush Institute has found chop patterns (integrating anterior abdominal muscles and glute complex activity), and AOS integrationfollowed immediately by POS integration very helpful. Generally the result of this progression is from an anterior pelvic tilt to an excessive forward lean, followed by improvement of the excessive forward lean with POS integration.
Fascia's response to specific intervention is complex. Responses may include strain hardening with repetitive or constant tension, enhanced shear and a reduction in cross-bridging between fascial layers, changes in both muscle tone and fibroblast mediated pre-tension (with sustained pressure), and/or altered transmission of force of multiple muscles acting to stabilize a joint (136-138). As mentioned above, one study implied deep, slow pressure to the abdominal region resulted in a decrease in muscle activity (5). This may be an example of a manual technique altering fibroblast mediated pre-tension, but more research is needed to support or refute this claim. If manual pressure is applied a tangential force is recommended to reduce discomfort. No studies could be located that investigated IASTM on the abdominal region, but based on the idea that shear between layers may be reduced as a result of dysfunction, careful application in practice may be warranted, especially where the layers converge at the semilunar lines. Careful re-assessment is recommended (as recommended with all techniques) to determine the efficacy on an individual basis.
|Intrinsic Stabilization Subsystem (ISS)||Under-active||Transverse Abdominis (TVA) Activation||N/A|
|Anterior Oblique Subsystem (AOS)||Over-active|
Avoid: planks, crunches, resisted hip flexion
|Legs with Push|
|Posterior Oblique Subsystem (POS)||Under-active||Chop Progression and Bridge Progression||Legs with Pull|
|Deep Longitudinal Subsystem (DLS)||Over-active||Avoid: leg curls, lumbar extensions||Avoid: straight-leg deadlifts, kettle bell windmills, Nordic curls|
Up Chop Pattern:
Dynamic Chop Pattern:
Anterior Oblique Subsystem Integration (Step Up to Chest Press):
Anterior Oblique Subsystem Integration Progression (Dynamic Lunge to Press):
Anterior Oblique Subsystem Power (Med Ball Smash):
Anterior Oblique Subsystem Power (Sled Push):
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© 2017 Brent Brookbush">posture, 52, 15-21.
© 2018 Brent Brookbush
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