Training the Abdominals: Traditional Plank versus Suspension Planks

Since the abdominal muscles are at the center of the body, it makes sense that they would be the primary stabilizers in typical movement patterns. Taking that logic a step further, it would also be reasonable to assume that performing an exercise under inherently unstable conditions should lead to additional activation of the abdominals. So if we were to do the plank exercise on the floor, we’d expect X activation, and if we do it suspended from a TRX device, we could expect X+ activation. One step further, and we would expect that the more instability we add to the suspension training, the more abdominal activation we’d achieve. But that’s one step too far.

When subjects were measured for abdominal activation in the plank versus a TRX arms-suspended plank, the suspended version forced the abdominals to work harder. But when the feet were additionally suspended (and presumably this looks something like a skydiving marionette), there was no additional activation in the abs. Also, it bears mention that unstable surface training (lower body), has actually been shown to inhibit gains in athletic performance (Wanna know why? Hint: name a sport where the surface is unstable…), while the same is likely not true about unstable upper body training. So these results aren’t completely surprising, even if we follow the logic that could suggest an alternative.

Here’s the abstract:

Effect of Using a Suspension Training System on Muscle Activation During the Performance of a Front Plank Exercise

Byrne, Jeannette M.; Bishop, Nicole S.; Caines, Andrew M.; Crane, Kalynn A.; Feaver, Ashley M.; Pearcey, Gregory E.P.

Abstract: Byrne, JM, Bishop, NS, Caines, AM, Crane, KA, Feaver, AM, and Pearcey, GEP. Effect of using a suspension training system on muscle activation during the performance of a front plank exercise.

J Strength Cond Res 28(11): 3049–3055, 2014—

The objective of the study was to examine the effect of suspension training on muscle activation during performance of variations of the plank exercise. Twenty-one participants took part. All individuals completed 2 repetitions each of 4 different plank exercises that consisted of a floor based plank, or planks with arms suspended, feet suspended, or feet and arms suspended using a TRX Suspension System. During plank performance, muscle activation was recorded from rectus abdominis, external oblique, rectus femoris, and serratus anterior (SA) muscles using electromyography. All planks were performed for a total of 3 seconds. Resulting muscle activation data were amplitude normalized, and root mean square activation was then determined over the full 3 second duration of the exercise. A significant main effect of plank type was found for all muscles. Post hoc analysis and effect size examination indicated that abdominal muscle activation was higher in all suspended conditions compared to the floor based plank. The highest level of abdominal muscle activation occurred in the arms suspended and arms/feet suspended conditions, which did not differ from one another. Rectus femoris activation was greatest during the arms suspended condition, whereas SA activity peaked during normal and feet suspended planks. These results indicate that suspension training as performed in this study seems to be an effective means of increasing muscle activation during the plank exercise. Contrary to expectations, the additional instability created by suspending both the arms and feet did not result in any additional abdominal muscle activation. These findings have implications in prescription and progression of core muscle training programs.