Summary Statement

The lower-ab myth is addressed through a comprehensive review of all 13 available electromyography and ultrasonography studies that measure upper and lower abdominal activity. While a few highly specific conditions can increase relative activation of the upper fibers, the evidence conclusively demonstrates that the rectus abdominis primarily functions as a single, continuous unit. No exercise, device, or movement has been shown to regionally isolate or selectively target the lower rectus abdominis.

Quick Summary

• The Muscle Contracts as a Unit: 10 of 13 electromyography (EMG) and ultrasonography studies demonstrate that the rectus abdominis activates uniformly as a single, continuous unit across a comprehensive range of core exercises.
• No "Lower Ab" Dominance: Only 3 or 13 studies provide some evidence that the upper rectus abdominis may exhibit more EMG activity during specific conditions. However, the inverse is never true. No exercise, device, or condition preferentially recruits or regionally isolates the lower rectus abdominis.
• The Physics Issue: The rectus abdominis runs vertically from the pelvis to the rib cage and must contract as a single unit to produce movement. If the lower fibers contracted while the upper fibers remained relaxed, they would simply stretch the upper fibers without creating any actual movement of the spine or pelvis.
• Spot Reduction is a Myth: Isolating the lower rectus abdominis, even if physiologically possible, would not yield localized fat loss. Fat reduction is a systemic process dictated by a caloric deficit, not by exercising a muscle to selectively burn the adipose tissue stored directly over it.

Caption: Lower ab burn is a feeling not a fact... the entire rectus abdominis is firing.

The Research is Clear

Research on upper and lower rectus abdominis activation is clear: the rectus abdominis functions as a single, continuous unit. Across 13 electromyography and ultrasonography studies analyzing a wide range of core exercises, from traditional crunches and leg raises to stability ball movements and portable abdominal devices, the evidence consistently demonstrates uniform activation from upper to lower portions. While a small handful of highly specific movements, such as fatiguing isometric curl-ups or isolated pelvic undulations, can occasionally result in greater relative activation of the upper rectus abdominis, the inverse is never true. Based on all of the available research, there is simply no exercise, device, or condition that has been shown to preferentially recruit or regionally isolate the lower rectus abdominis.

Physics, Anatomy, and Clinical Proof

Although the rectus abdominis is segmentally innervated, the biomechanics of the human body require that it contract as a single functional unit to produce movement against resistance. The muscle spans vertically from the pubic symphysis to the xiphoid process and the costal cartilages. If the inferior (lower) portion of the rectus abdominis were to contract while the superior (upper) portion remained relaxed or contracted at a significantly lower intensity, the pulling force of the lower fibers would simply stretch and lengthen the upper fibers. The overall length of the muscle from end to end would remain unchanged, meaning no actual movement of the ribcage, pelvis, or spine would occur. This would be similar to trying to pull a heavy object with a rope, but attempting to move it while applying tension to only half the rope in your hand, with the other half attached to the object remaining completely slack; the object would never move. This biomechanical reality is clinically observable in a neurological finding known as Beevor's sign. In patients with specific mid-thoracic spinal cord injuries, where the lower rectus abdominis becomes paralyzed but the upper remains innervated, attempting a sit-up causes the active upper fibers to pull against the paralyzed lower fibers. The lower fibers merely stretch, causing the umbilicus (belly button) to migrate upward toward the head, but the patient cannot move their trunk or flex their spine because the muscle can no longer generate force from end to end.

Why Would You Want To? (The Spot Reduction Myth)

Furthermore, even if an exercise could magically isolate the lower rectus abdominis, it would still fail to produce the aesthetic results most individuals seek. The obsession with targeting the "lower abs" is almost universally driven by the goal of losing subcutaneous fat over the lower abdomen, which relies entirely on the physiological impossibility of "spot reduction." Exercising a specific muscle does not preferentially burn the fat stored directly over that muscle. Fat loss occurs as a systematic process, drawing from all of the body's fat stores, and is achieved through a sustained caloric deficit, rather than through strenuous exercise (which relies more heavily on glucose metabolism). Therefore, trying to find the perfect "lower ab" exercise to achieve a flat stomach is an inherently flawed and inefficient strategy. Instead, fitness and rehabilitation professionals should prioritize compound, high-intensity, and integrated core training to maximize overall caloric expenditure and build functional, total-body strength. Note that individuals who can "see" their lower abs don't have different lower abs; they just have lower overall body fat. Think to yourself, have you personally ever seen someone with visible lower abs who was "soft" everywhere else? No, of course not.

Better Core Exercises:

• Bridge and Progressions
• Plank Exercise and Side Plank Exercise Progressions
• Wood Chop Exercise and Progressions
• Transverse Abdominis (TVA) Activation: Quadruped Exercise and Progressions

Caption: Great lower abs result from great core work overall and low body fat.

Research Review:

Thirteen studies compared upper and lower rectus abdominis electromyography (EMG) activity or muscle thickness during various core exercises and movements. Ten of these studies (five providing direct evidence and five providing indirect evidence) demonstrated that the rectus abdominis primarily activates as a single, continuous unit. The remaining three studies demonstrated that specific conditions (e.g., traditional crunches, fatiguing isometric curl-ups, and belly dancing) resulted in significantly greater activation of the upper rectus abdominis; however, no study demonstrated that any exercise or condition led to a relative increase in lower rectus abdominis activity.

• Statistically Similar, Direct Evidence: Five (of thirteen) studies providing direct evidence, where the upper and lower rectus abdominis were measured simultaneously via electromyography (EMG) or ultrasound to directly compare responses during the exact same tasks, demonstrated that these segments exhibited statistically similar activation levels and muscle thickness ratios across a comprehensive range of core exercises. Specifically, the upper and lower rectus abdominis exhibited statistically similar responses during stable and labile surface curl-ups, reverse curl-ups, leg lowering, straight leg raises at varying angles, abdominal muscle lifts, oblique crunches, and both unassisted and device-assisted crunches. Furthermore, these findings remained consistent even when strictly controlling for spine curvature, posture, and muscle length. In summary, this direct evidence strongly indicates that the rectus abdominis primarily activates as a single, continuous unit, and that varying exercise selections, portable abdominal devices, or the addition of instability do not elicit regional isolation of the upper or lower fibers.
• Statistically Similar, Indirect Evidence: Five studies (of thirteen) providing indirect evidence, where researchers observed that the upper and lower segments exhibited similar relative increases and decreases in electromyographic (EMG) activity across varying exercises, thereby implying a lack of regional isolation without necessarily running direct statistical comparisons between the two fibers, demonstrated that the rectus abdominis activates as a single continuous unit. Specifically, the upper and lower rectus abdominis exhibited similar parallel activation patterns during traditional crunches, bent-knee sit-ups, military-style curl-ups, reverse curls, Swiss ball exercises (e.g., roll-outs and pikes), and numerous portable abdominal devices (including the Torso Track, AB-DOer, Ab Roller Plus, and Perfect Abs). Furthermore, increasing the intensity of the movement, such as adding a pelvic tilt during a reverse curl or utilizing higher resistance settings on portable equipment, uniformly increased global muscle activation rather than shifting regional activation. In summary, this indirect evidence is congruent with the direct evidence that various unassisted core exercises, equipment variations, and intensity adjustments do not elicit regional isolation of the upper or lower rectus abdominis.
• Statistically Different Activation Levels: Three (of thirteen) studies demonstrated that the upper rectus abdominis, and not the lower rectus abdominis, exhibited significantly different activation levels and fatigue indices during certain activities. The upper and lower rectus abdominis exhibited statistically similar EMG activity during a majority of dance and curl-up activities, isometric leg raises, basic jackknives, and upright planar activities (including anterior-posterior translations, medial-lateral translations, transverse rotations, and horizontal circles) where the thorax moved while the pelvis remained still. However, specific tasks, such as traditional crunches, fatiguing isometric curl-ups, belly-roll abdominal undulations (e.g., belly-dancing movements), and planar activities requiring the pelvis to move while the thorax remained still, resulted in significantly higher activation, altered timing, or higher fatigue indices of the upper rectus abdominis. In summary, a relatively small number of specific conditions can result in differentiation of the upper and lower rectus abdominis; however, this results in increased upper rectus abdominis activity, and there appears to be no condition that results in a relative increase in lower abdominal activity.

Practical Conclusion: Fitness and rehabilitation professionals should abandon the concept of isolating the lower rectus abdominis. The current body of evidence conclusively demonstrates that the rectus abdominis functions as a single, continuous unit across a wide range of traditional, device-assisted, and stability-based core exercises, including leg raises and reverse crunches, which have historically been believed to target the "lower abs." While a limited number of specific movements (e.g., traditional crunches, fatiguing isometric curl-ups, and isolated pelvic movements) result in significantly higher activation of the upper rectus abdominis, no exercise or condition selectively targets or increases relative activation of the lower rectus abdominis. Therefore, professionals should select core exercises based on global abdominal activation, functional integration, and patient tolerance, rather than attempting to regionally isolate the lower abdominal fibers.

Caption: No lower ab work; leg raises recruit the entire rectus abdominis.

Annotated Bibliography: The Lower Ab Myth

Statistically Similar: Direct Evidence

Comparing Abdominal Response During Curl-ups on Stable and Labile Surfaces: Grenier et al. compared 8 healthy males (age: 23.3 ± 4.3 years) with no history of acute or chronic low back injury or prolonged back pain. All participants performed a stable surface curl-up protocol, a labile ball and feet on the floor protocol, a labile ball and feet on a bench protocol, and a wobble board protocol during 1 session. The stable surface curl-up protocol included an isometric traditional curl-up on a padded bench (with the feet flat, and knees and hips flexed) for 1 set/exercise, 1 rep/set, and a 6-second hold. The labile ball and feet on the floor protocol included an isometric curl-up with the torso supported on a 70 cm gym ball (with feet flat on the floor) for 1 set/exercise, 1 rep/set, and a 6-second hold. The labile ball and feet on a bench protocol included an isometric curl-up with the torso supported on a 70 cm gym ball and feet resting on a bench (at the same height as the ball) for 1 set/exercise, 1 rep/set, and a 6-second hold. The wobble board protocol included an isometric curl-up with the torso supported on a round wobble board (with feet flat on the floor) for 1 set/exercise, 1 rep/set, and a 6-second hold. All protocols were performed with a moderate (2 min) rest between exercises. Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, and external oblique. The findings demonstrated that EMG activity of the upper and lower rectus abdominis and external oblique was significantly higher during all labile surface protocols when compared to the stable surface protocol. Further, the external oblique exhibited the largest increases in EMG activity among the abdominal muscles tested. Additionally, EMG activity of the upper rectus abdominis and lower rectus abdominis was statistically similar during all protocols.

• Grenier, S. G., Vera-Garcia, F. J., & McGill, S. M. (2000). Abdominal response during curl-ups on both stable and labile surfaces. Physical Therapy, 80(6), 564-569.

Comparing Upper and Lower Rectus Abdominis Activation During Core Exercises:

Clark et al. compared 8 healthy adult males and females. All participants performed a curl-up protocol, Sissel ball curl-up protocol, Ab Trainer curl-up protocol, leg lowering protocol, Sissel ball roll-out protocol, and reverse curl-up protocol in random order during 1 session. All protocols included a 2-second concentric contraction. Outcome measures included surface EMG activity of the upper rectus abdominis and lower rectus abdominis. The findings demonstrated that EMG activity of the upper and lower rectus abdominis was statistically similar during all protocols. Further, EMG activity of the upper and lower rectus abdominis was significantly higher during the Sissel ball curl-up protocol when compared to all other protocols. Additionally, EMG activity of the upper and lower rectus abdominis was significantly higher during the curl-up and Ab Trainer curl-up protocols when compared to the reverse curl-up, leg lowering, and Sissel ball roll-out protocols. Finally, EMG activity of the upper and lower rectus abdominis was statistically similar during the curl-up and Ab Trainer curl-up protocols.

• Clark, K. M., Holt, L. E., & Sinyard, J. (2003). Electromyographic comparison of the upper and lower rectus abdominis during abdominal exercises. The Journal of Strength and Conditioning Research, 17(3), 475-483.

Comparing Upper and Lower Rectus Abdominis Activation During Selected Trunk Exercises: Lehman et al. compared 11 healthy athletic participants from a university population with low subcutaneous fat. All participants performed an isometric curl-up protocol, an abdominal muscle lift protocol, a leg raise protocol, and a restricted leg raise protocol during 1 session. All protocols were performed while controlling for spine curvature, posture, and range of motion to ensure consistent muscle lengths across exercises. Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, and external oblique. The findings demonstrated that EMG activity of the upper and lower rectus abdominis was statistically similar within and between all protocols. However, EMG activity of the external oblique exhibited significant differences between the exercise protocols.

• Lehman, G. J., & McGill, S. M. (2001). Quantification of the differences in electromyographic activity magnitude between the upper and lower portions of the rectus abdominis muscle during selected trunk exercises. Physical Therapy, 81(5), 1096-1101.

Comparing Muscle Activity During Sit-ups With and Without Abdominal Exercise Devices:

Whiting et al. compared 19 healthy males and females. All participants performed unassisted abdominal exercise protocols (basic crunch with arms crossed, basic crunch with arms down, oblique crunch, and reverse crunch) and device-assisted protocols (utilizing 4 different exercise devices) during 1 session. (Sets, reps, tempo, and rest between exercises not reported). Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, rectus femoris, and sternocleidomastoid during the concentric and eccentric phases. The findings demonstrated that EMG activity of the upper rectus abdominis, lower rectus abdominis, and external oblique was statistically similar during the unassisted exercise protocols when compared to the device-assisted protocols. Additionally, the upper rectus abdominis and lower rectus abdominis exhibited similar relative increases and decreases in EMG activity across all protocols. These findings further demonstrate that the rectus abdominis activates as a single unit, and that neither unassisted crunches nor portable devices elicit regional isolation of the upper or lower fibers.

• Whiting, W. C., Rugg, S., Coleman, A., & Vincent, W. J. (1999). Muscle activity during sit-ups using abdominal exercise devices. The Journal of Strength and Conditioning Research, 13(4), 339-345.

Comparing Upper and Lower Rectus Abdominis Activation Using Ultrasonography: Kim et al. compared 30 healthy males and females (age: 30.26 ± 1.99 years) from a hospital staff population with no history of back pain or spinal disorders (e.g., spinal stenosis, disk disease, or spine fracture). All participants performed a curl-up protocol (in a hook-lying position with 90° knee flexion) and a straight leg raise protocol evaluated at 30°, 60°, and 90° angles during 1 session (sets, reps, tempo, and rest not reported). Outcome measures included muscle thickness ratio (measured via ultrasonography) of the upper rectus abdominis, lower rectus abdominis, external oblique, internal oblique, and transversus abdominis. The findings demonstrated that the muscle thickness ratio of the upper rectus abdominis and lower rectus abdominis was statistically similar during the curl-up and straight leg raise protocols across all measured angles. These findings further demonstrate that neither exercise selectively strengthens the rectus abdominis based on location.

• Kim, H. D., Jeon, D. M., Bae, H. W., Kim, J. G., Han, N., & Eom, M. J. (2015). Changes in activation of abdominal muscles at selected angles during trunk exercise by using ultrasonography. Annals of Rehabilitation Medicine, 39(6), 950-956.

Statistically Similar: Indirect Evidence

Electromyographic Analysis of Abdominal Muscle Activity Using Portable Abdominal Exercise Devices and a Traditional Crunch: Sternlicht et al. compared 33 healthy males and females (age: 27.3 ± 10.7 years) with sufficiently low subcutaneous adipose tissue. All participants performed a traditional crunch protocol, an AB-DOer protocol, a Torso Track protocol (at low and high tension settings), an Ab Roller Plus protocol, a seated Perfect Abs protocol (with low, medium, and high resistance bands), and a supine Perfect Abs protocol (with low, medium, and high resistance bands) in random order, during 1 session. All protocols included 1 set/exercise, 8-10 reps/set, and a moderate (1.5:0:1.5) tempo (rest between exercises not reported). Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, and rectus femoris. The findings demonstrated that EMG activity of the upper and lower rectus abdominis was significantly higher during the Perfect Abs supine (medium and high resistance) protocols, followed by the Ab Roller Plus, Torso Track (high tension), Perfect Abs seated (medium and high resistance), Perfect Abs supine (low resistance), and traditional crunch protocols (which were statistically similar), and lowest during the AB-DOer, Torso Track (low tension), and Perfect Abs seated (low resistance) protocols. Further, EMG activity of the external oblique was significantly higher during the Torso Track (high tension), Perfect Abs seated (high resistance), and Perfect Abs supine (medium and high resistance) protocols, followed by the traditional crunch protocol (and all other statistically similar protocols), and lowest during the AB-DOer protocol. EMG activity of the rectus femoris was minimal during all protocols. Additionally, the upper rectus abdominis and lower rectus abdominis exhibited similar relative increases and decreases in EMG activity across all protocols. These findings likely imply that none of the portable devices or variations elicited regional isolation of the rectus abdominis.

• Sternlicht, E., & Rugg, S. (2003). Electromyographic analysis of abdominal muscle activity using portable abdominal exercise devices and a traditional crunch. The Journal of Strength and Conditioning Research, 17(3), 463-468.

Comparing Upper and Lower Rectus Abdominis Activation Using Portable Devices: Sternlicht et al. compared 46 healthy males and females. All participants performed a traditional crunch protocol, an Ab-ONE protocol, a Perfect Abs Roller protocol, an Ab Scissor protocol, an Ab Swing protocol, a 6SecondAbs protocol, and a Torso Track protocol in random order, during 1 session. The portable device protocols utilizing variable resistance were tested at their highest resistance setting (sets, reps, tempo, and rest not reported). Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, and external oblique. The findings demonstrated that EMG activity of the upper and lower rectus abdominis was significantly higher during the Ab-ONE protocol, followed by the traditional crunch and Perfect Abs Roller protocols (which were statistically similar), and lowest during the Ab Scissor, Ab Swing, 6SecondAbs, and Torso Track protocols. Additionally, the upper rectus abdominis and lower rectus abdominis exhibited similar relative increases and decreases in EMG activity across all protocols. These findings further demonstrate that these portable devices neither isolate nor alter the regional activation of the rectus abdominis.

• Sternlicht, E., Rugg, S. G., Bernstein, M. D., & Armstrong, S. D. (2005). Electromyographical analysis and comparison of selected abdominal training devices with a traditional crunch. The Journal of Strength and Conditioning Research, 19(1), 157-162.

Comparing Abdominal Activation During Military Sit-Ups and Curl-Ups: Burden et al. compared 23 male and female British Army personnel (age not reported). All participants performed a British Army-style sit-up protocol and 4 curl-up variation protocols (with and without restrained feet) during 1 session. All protocols were performed continuously for 2 minutes/exercise, evaluated at the start, middle, and end of the exercise period (sets, reps, load, rest, and tempo not reported). Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, internal oblique, transversus abdominis, and rectus femoris. The findings demonstrated that EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, internal oblique, and transversus abdominis was highest during the curl-up with arms crossed and feet restrained protocol. Additionally, the upper rectus abdominis and lower rectus abdominis exhibited similar relative increases and decreases in EMG activity across all protocols. These findings further demonstrate that the rectus abdominis functions as a single continuous unit regardless of the exercise variation performed.

• Burden, A. M., & Redmond, C. G. (2013). Abdominal and hip flexor muscle activity during 2 minutes of sit-ups and curl-ups. The Journal of Strength and Conditioning Research, 27(8), 2119-2128.

Core Muscle Activation During Swiss Ball and Traditional Abdominal Exercises: Escamilla et al. compared 18 healthy males and females. All participants performed traditional abdominal exercise protocols (including the crunch and bent-knee sit-up) and Swiss ball exercise protocols (including the roll-out, pike, knee-up, skier, right and left hip extension, decline push-up, and right sitting march) during 1 session. (Sets, reps, tempo, and rest between exercises not reported). Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, internal oblique, latissimus dorsi, lumbar paraspinals, and rectus femoris. The findings demonstrated that EMG activity of the upper and lower rectus abdominis was highest during the Swiss ball roll-out and pike protocols. Further, EMG activity of the upper and lower rectus abdominis was statistically similar during the crunch protocol when compared to the bent-knee sit-up protocol. Additionally, the upper rectus abdominis and lower rectus abdominis exhibited similar relative increases and decreases in EMG activity across all exercise variations.

• Escamilla, R. F., Lewis, C., Bell, D., Bramblet, G., Darnell, J., Fink, C., ... & Andrews, J. R. (2010). Core muscle activation during Swiss ball and traditional abdominal exercises. Journal of Orthopaedic & Sports Physical Therapy, 40(5), 265-276.

Electromyographic Comparison of the Upper and Lower Rectus Abdominis During Abdominal Exercises: Sperandei et al. compared 20 healthy young adults. All participants performed a curl exercise protocol (moving the superior body portion toward the inferior portion) and a reverse curl exercise protocol (moving the inferior body portion toward the superior portion) during 1 session. Outcome measures included surface EMG activity of the upper rectus abdominis and lower rectus abdominis. The findings demonstrated that EMG activity of the upper rectus abdominis and lower rectus abdominis was statistically similar during the curl exercise protocol when compared to the reverse exercise protocol. However, the reverse exercise protocol with a pelvic tilt resulted in higher EMG activity for both the upper and lower rectus abdominis portions, illustrating that increased exercise intensity increases global muscle activation rather than shifting regional activation.

• Sperandei, S., de Barros, M. A. P., & Sartorato, R. (2009). Electromyographic comparison of the upper and lower rectus abdominis during abdominal exercises. The Journal of Strength and Conditioning Research, 23(7), 2167-2172.

Statistically Different: Direct Evidence

Comparing Upper and Lower Rectus Abdominis Activation During Low-Intensity and Fatiguing Tasks: Marchetti et al. compared 11 healthy adult males (age: 24 ± 3 years) for a low-intensity experiment and 10 healthy adult males (age: 26 ± 8 years) for a fatiguing experiment, with no history of neurological or musculoskeletal disease and previous experience with abdominal exercising. During the low-intensity experiment, participants performed an isometric curl-up (supine trunk raise) protocol and an isometric leg raise (supine bent leg raise) protocol. Both low-intensity protocols were performed at a force level that recruited only a few motor units, guided by visual biofeedback. During the fatiguing experiment, participants performed isometric curl-up and leg raise protocols. Both fatiguing protocols required participants to maintain a specific isometric force level to induce fatigue. Outcome measures included surface EMG activity and median frequency (fatigue index) of the upper rectus abdominis and lower rectus abdominis. The findings demonstrated that during the low-intensity protocols, EMG activity from the upper and lower rectus abdominis was highly correlated, indicating that the signals were statistically similar across both the curl-up and leg raise protocols. However, the ratio of upper to lower rectus abdominis EMG activity was significantly higher during the low-intensity curl-up protocol when compared to the low-intensity leg raise protocol. During the fatiguing protocols, the upper rectus abdominis exhibited a significantly higher fatigue index during the curl-up protocol when compared to the lower rectus abdominis.

• Marchetti, P. H., Kohn, A. F., & Duarte, M. (2011). Selective activation of the rectus abdominis muscle during low-intensity and fatiguing tasks. Journal of Sports Science & Medicine, 10(2), 322-327.

Neuromuscular Independence of Abdominal Wall Muscles as Demonstrated by Middle-Eastern Style Dancers: Moreside et al. compared 9 female middle-eastern dancers. All participants performed 30 dance, planar, and curl-up activities. Outcome measures included surface EMG activity of the upper rectus abdominis, lower rectus abdominis, external oblique, and internal oblique. The findings demonstrated that EMG activity of the upper rectus abdominis and lower rectus abdominis exhibited significantly different activation timing during 3 specific "belly-roll" conditions involving low levels of muscle activation and no external torque. Further, EMG activity of the upper and lower rectus abdominis exhibited significantly different activation levels during 8 conditions requiring pelvis movements with minimal thorax motion. However, EMG activity of the upper and lower rectus abdominis was statistically similar during all other activities. Additionally, EMG activity of the external oblique and internal oblique aligned temporally with the lower rectus abdominis during the belly-roll conditions.

• Moreside, J. M., Vera-Garcia, F. J., & McGill, S. M. (2008). Neuromuscular independence of abdominal wall muscles as demonstrated by middle-eastern style dancers. Journal of Electromyography and Kinesiology, 18(4), 527-537. https://doi.org/10.1016/j.jelekin.2007.01.003Cited by: 41

Statistically Different: Indirect Evidence

Comparing Rectus Abdominis Activation During a Traditional Crunch and Jackknife Exercise: Nelson et al. compared 22 healthy males and females (age: 20.5 ± 1.5 years) from a university population. All participants performed a traditional crunch protocol and a basic jackknife protocol (using the Ab Lounge device) during 1 session (sets, reps, tempo, and rest not reported). Outcome measures included surface EMG activity of the upper rectus abdominis and lower rectus abdominis. The findings demonstrated that EMG activity of the upper rectus abdominis was significantly higher during the traditional crunch protocol when compared to the basic jackknife protocol. Further, EMG activity of the lower rectus abdominis was statistically similar during both protocols.

• Nelson, G. A., Bent-Forsythe, D. A., & Roopchand-Martin, S. C. (2012). Electromyographic activity of the rectus abdominis during a traditional crunch and the basic jackknife exercise with the Ab Lounge. The Journal of Strength and Conditioning Research, 26(6), 1584-1588.