One day, while doing squats in the gym, my bodybuilder friend approached me to give me some advice. “Jason,” she interrupted, “if you want to target the inside of your quads, use a wide stance and point your toes out like a duck. If you want to target the outside of your quads, use a narrow stance and point your toes in like a pigeon.” I decided to give it a try since, after all, bodybuilders should know how to target different muscles. But I also started to wonder, how do you know if changing body position really changes the focus of the exercise? The only way to really know which muscles are used is to measure their electrical activity with an electromyogram (EMG), the skeletal muscle equivalent of an electrocardiogram for your heart. Well, guess what? Scientists have done just that. And some of what they have found may surprise you. Let’s take a look at how different body positions during some common exercises affect muscle activity.
Leg Extensions and Squats
Leg position affects quadriceps activity during leg extensions, but it does not have the same effect during squats. Comparing three different leg positions (medially rotated, laterally rotated and neutral) during a set of eight reps of leg extensions, a study published in Journal of Strength and Conditioning Research found that medially rotating the legs by pointing the toes in targets the vastus lateralis and vastus medialis muscles, while laterally rotating the legs by pointing the toes out increases rectus femoris activity.
For squats, research has shown there is no effect of leg position, stance width or squat depth on quadriceps activity. A study published in Journal of Strength and Conditioning Research found that changing leg position by pointing the toes in, out or straight has no effect on quadriceps activity (I guess my bodybuilder friend was wrong). A study published in Medicine and Science in Sports and Exercise found that stance width also does not affect quadriceps activity but does influence adductor longus and gluteus maximus activity, with a wide stance (140 percent of shoulder width) eliciting greater muscle activity than a shoulder width or narrow stance (75 percent of shoulder width). Comparing partial, parallel and full squat depths, another study published in Journal of Strength and Conditioning Research found that the gluteus maximus but not the vastus lateralis, vastus medialis or biceps femoris, becomes more active as squat depth increases.
So if you want your clients to target their quads, all leg positions, stance widths and squat depths are equally effective. If you want your clients to target their gluteus maximus and adductor longus muscles, tell them to use a wide stance and squat until their thighs are past being parallel to the floor.
Lat Pull Downs and Seated Rows
A study published in Journal of Strength and Conditioning Research found that a wide grip during lat pull downs increases latissimus dorsi and triceps activity and a close grip increases pectoralis major and posterior deltoid activity. In contrast, a study published in Dynamic Medicine found that a wide grip does not increase latissimus dorsi activity, nor does a close grip (with palms facing in) preferentially activate the biceps, which is commonly believed.
To target the upper back muscles, seated rows seem to be better than lat pull downs. A study published in Dynamic Medicine found that the trapezius, rhomboids and latissimus dorsi are all more active during seated rows compared to lat pull downs. Also, the common recommendation of retracting the scapula by squeezing them together has no effect on muscle activity. So tell your clients to stick with seated rows for their upper back workouts.
Bench Press and Push Ups
Thought of as a chest and triceps exercise, the bench press is also great for your clients’ deltoids. A study published in Journal of Strength and Conditioning Research found that the triceps and anterior head of the deltoid are the most active muscles during the bench press (compared to the pectoralis major and biceps). Considering all four muscles together, the researchers found that the widest grip tested (190 percent of shoulder width) elicits greater muscle activity than narrower grips (shoulder width and 130 percent of shoulder width). For the best overall training stimulus, tell your clients to use a grip that is almost double their shoulder width.
While push ups may seem like a similar exercise as a bench press, there seems to be differences when isolating specific muscles. Research has shown that for both exercises, the triceps are more active with a narrow hand position, but the pectoralis major is more active with a narrow hand position only for push ups. For the bench press, the pectoralis major is more active with a wide grip. Moving from a wide to a narrow grip for the bench press moves the emphasis from the pectoralis major to the triceps. A study published in Dynamic Medicine also found that rectus abdominis (but not external obliques) activity is greater when doing push ups with hands (but not the feet) on a stability ball compared to on a bench.
With all the abdominal training devices on the market, how do your clients know which is best for their abs? The answer is: none of them. Comparing abdominal muscle activity between commercial abdominal devices and traditional crunches (lifting the shoulders and torso a few inches off the ground), a study published in Journal of Strength and Conditioning Research found that the Ab-ONE is the only commercial device that elicits a higher rectus abdominis activity than a traditional crunch. The study also found that crunches are better than the Ab Scissor, Ab Swing, 6-Second Abs and Torso Track and are equal to the Perfect Abs Roller. External obliques activity during crunches is higher than for the Perfect Abs Roller and is similar to the other devices. Other studies have also shown that traditional crunches are just as effective or better than abdominal devices. So tell your clients to save their money and stick with old fashioned crunches.
When your clients do crunches, tell them to lay on an unstable surface. One study published in Physical Therapy (using six-second isometric contractions) and another published in Journal of Strength and Conditioning Research (using two second dynamic contractions) found that the rectus abdominis and external obliques are more active while doing crunches on a stability ball with feet on the floor compared to when lying on a stable surface.
While crunches on unstable surfaces may be better for your clients’ abs, don’t assume that other exercises on the stability ball are better for your clients’ core muscles. One study published in Dynamic Medicine found no difference in rectus abdominis, external and internal obliques, and erector spinae activity between upper body exercises (bench press, biceps curls, lateral raises, shoulder press and triceps extensions) performed while sitting on a bench or stability ball, and another study published in Journal of Strength and Conditioning Research found that only a bench press performed on a stability ball, but not a shoulder press, elicits greater rectus abdominis and erector spinae activity.
Probably the most confusing aspect of abdominal training is the issue of the “upper” and “lower” abs. However, muscles cannot contract with only part of their lengths. The six-pack look your clients dream of is not six separate muscles or three pairs of muscles. It’s all one muscle, with tendon inscriptions separating each “section.” The popular belief that certain exercises can target upper and lower portions of the rectus abdominis is not fully supported by research. One study published in Journal of Strength and Conditioning Research found no difference in upper and lower rectus abdominis activity between different exercises, with upper body exercises (traditional crunch, crunch on stability ball and ab trainer-assisted crunch) eliciting greater muscle activity than lower body exercises (reverse crunch, leg lowering), and another study published in Physical Therapy found no difference in upper and lower rectus abdominis activity between a traditional crunch and straight leg raises. Another study published in Journal of Strength and Conditioning Research found that a traditional crunch, twist crunch (twisting to one side while lifting torso), reverse crunch (raising legs and buttocks instead of torso) and V-sit (raising both torso and legs to create a “V” shape) all produce similar levels of upper rectus abdominis activity. This study also found that the lower rectus abdominis is more active during the reverse crunch and V-sit, as are the external obliques, contrary to the popular belief that twisting movements target the obliques. While a couple of other studies have shown differences in activation between upper and lower portions of the rectus abdominis, they did not express the EMG signal as a percentage of the muscle’s maximum activity, which precludes valid comparisons between the two portions of the muscle.
Next time you train your clients in the gym, use these research findings to help you decide which positions and grips are best. Not only will your clients maximize their time in the gym, you won’t get interrupted during your workouts!
- Behm, D.G., Leonard, A.M., Young, W.B., Bonsey, W.A., and MacKinnon, S.N. (2005). Trunk muscle electromyographic activity with unstable and unilateral exercises. Journal of Strength and Conditioning Research 19(1):193-201.
- Boyden, G., Kingman, J., and Dyson, R. (2000). A comparison of quadriceps electromyographic activity with the position of the foot during the parallel squat. Journal of Strength and Conditioning Research. 14(4):379-382.
- Caterisano, A., Moss, R.F., Pellinger, T.K., Woodruff, K., Lewis, V.C., Booth, W., and Khadra, T. (2002). The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. Journal of Strength and Conditioning Research. 16(3):428-432.
- Clark, K.M., Holt, L.E., and Sinyard, J. (2003). Electromyographic comparison of the upper and lower rectus abdominis during abdominal exercises. Journal of Strength and Conditioning Research. 17(3):475-483.
- Clemons, J.M. and Aaron, C. (1997). Effect of grip width on the myoelectric activity of the prime movers in the bench press. Journal of Strength and Conditioning Research. 11(2):82-87.
- Cogley, R.M., Archambault, T.A., Fibeger, J.F., Koverman, M.M., Youdas, J.W., and Hollman, J.H. (2005). Comparison of muscle activation using various hand positions during the push-up exercise. Journal of Strength and Conditioning Research. 19(3):628-633.
- Lehman, G.J. (2005). The influence of grip width and forearm pronation/supination on upper-body myoelectric activity during the flat bench press. Journal of Strength and Conditioning Research. 19(3):587-591.
- Lehman, G.J., Buchan, D.D., Lundy, A., Myers, N., and Nalborczyk, A. (2004). Variations in muscle activation levels during traditional latissimus dorsi weight training exercises: An experimental study. Dynamic Medicine. 3(1):4.
- Lehman, G.J., Gordon, T., Langley, J., Pemrose, P., and Tregaskis, S. (2005). Replacing a Swiss ball for an exercise bench causes variable changes in trunk muscle activity during upper limb strength exercises. Dynamic Medicine. 4:6.
- Lehman, G.J., Macmillan, B., MacIntyre, I., Chivers, M., and Fluter, M. (2006). Shoulder muscle EMG activity during push up variations on and off a Swiss ball. Dynamic Medicine. 5:7.
- Lehman, G.J. and 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.
- McCaw, S.T. and Melrose, D.R. (1999). Stance width and bar load effects on leg muscle activity during the parallel squat. Medicine and Science in Sports and Exercise. 31(3):428-436.
- Signorile, J.F., Zink, A.J., and Szwed, S.P. (2002). A comparative electromyographical investigation of muscle utilization patterns using various hand positions during the lat pull-down. Journal of Strength and Conditioning Research. 16(4):539-546.
- Sternlicht, E., Rugg, S.G., Bernstein, M.D., and Armstrong, S.D. (2005). Electromyographical analysis and comparison of selected abdominal training devices with a traditional crunch. Journal of Strength and Conditioning Research. 19(1):157-162.
- Stoutenberg, M., Pluchino, A.P., Ma, F., Hoctor, J.E., and Signorile, J.F. (2005). The impact of foot position on electromyographical activity of the superficial quadriceps muscles during leg extension. Journal of Strength and Conditioning Research. 19(4):931-938.
- Vera-Garcia, F.J., Grenier, S.G., and McGill, S.M. (2000). Abdominal muscle response during curl-ups on both stable and labile surfaces. Physical Therapy. 80(6):564-569.
- Willett, G.M., Hyde, J.E., Uhrlaub, M.B., Wendel, C.A., and Karst, G.M. (2001). Relative activity of abdominal muscles during commonly prescribed strengthening exercises. Journal of Strength and Conditioning Research. 15(4):480-485.