Tuesday, September 8, 2015

Four Ways to Turn Your AM Push-Up Routine into a Full-Body Workout: Wobble Board, Stability Disc, Fitness Dome, and TRX Suspension Trainer Under Scientific Scrutiny

Based only on the study at hand, the TRX system does not seem to be significantly superior to the three other systems. In conjunction w/ previous research, discussed in the light-blue info box and the bottom line, though, it appears to be the best, certainly most versatile device.
Ok, the push up is already a full body movement, but as a recent unsponsored study from the University of Valencia shows, the muscle activation during push-ups performed under stable and unstable conditions varies significantly. So significantly, in fact, that certain muscle groups, such as the serratus aneterior, may be hammered twice as heavy when you use the "right" instability devices... and the best thing: None of the devices Borreani et al. tested will overrun the budget of a well-equipped homegym.

With that being said, let's take an initial look at the contestants. There's the classic push-up (not shown in Figure 1, because it requires no extra-device, but the floor), the (A) wobble board, the (B) stability disc, the (C) fitness dome, and the (D) TRX Suspension Trainer.
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The study participants were young fit male university students (n = 30; age: 23 ± 1.13 years; height: 178.87 ± 8.21 cm; body mass: 78.01 ± 8.5 kg; body fat percentage: 11.48 ± 3.18%; and biacromial (shoulder) width: 42.22 ± 12.81 cm) who voluntarily participated in this study. With a minimum of 1 year of resistance training experience, performing at least two sessions/wk at moderate to vigorous intensity, none of them was a rookie - an advantage of that makes the results of the study more relevant to the average gymrat.
Figure 1:  The unstable devices used in the present study: (A) wobble board, (B) stability disc, (C) fitness dome,
and (D) TRX Suspension Trainer which will obviously hang from the ceiling  (Borreani. 2015).
Each participant took part in two types of sessions: (1) familiarization and (2) experimental sessions, both at the same time in the morning. The first session occurred 48-72 hours before the data collection in the experimental session. Several restrictions were imposed on the volunteers: no food, drinks, or stimulants (e.g., caffeine) to be consumed 3-4 hours before the sessions and no physical activity more intense than daily activities 12 hours before the exercises. They were instructed to sleep >8 hours the night before data collection.
  • The familiarization session familiarized the participants with the push-up exercise, unstable devices, movement amplitude, body positioning, and the cadence of movement that would later be used during data collection. Participants practiced the exercises one to three times each.
  • The actual protocol started with the application of the EMG electrodes on the subjects' anterior deltoid (DELT), serratus anterior (SERRA), rectus femoris (FEM), and lumbar multifidus (LUMB), on the dominant side of the body.

    After the subjects were all wired up (in the literal sense), they started the push-ups in an extended arm (up) position with forearms and wrists pronated and feet at the biacromial (shoulder) width. In the down position, the forearm and wrists were kept pronated, whereas the elbow was flexed at ~90 and the shoulder was abducted at ~45 . The hip and spine were maintained neutral during all repetitions; this was verified using a laser device during the execution of the repetitions (Black & Decker, series LZR6TP9). Furthermore, each participant used a standardized grip at biacromial width (based on the distance in centimeters between the tips of the right and left third digits).

    Each participant performed five consecutive repetitions under all conditions. A 2-second rate for descent and ascent of an individual push-up cycle was maintained by a 30-Hz metronome (Ableton Live 6, Ableton AG, Berlin, Germany) to standardize the speed of movement. Visual feedback was given to the participants in order to maintain the range of movement and hand distance during the data collection.
If you've read  the summary carefully you will be astonished that the "pecs", i.e. the pectoralis major wasn't attached to an electrode, as well. From a practical perspective, that's unquestionably a downside of the study at hand. From a mere science perspective, though, it is only logical, because the scientists were interested in the co-activators, not the primary mover (see box below for the answer to the question that you may be asking yourselves, now ;-).
Science knows better than bros: The narrow push up activates both, triceps and pecs best (Cogley. 2005).
What about the pecs than? As previously explained, the pectoralis was not the main research interest of Borreani et al. From previous studies, we know however that doing narrow(er) push-ups will increase the activity of both triceps and biceps (Cogley. 2005 | see Figure on the left). Based on the lack of effect of the instability devices on "front delt" activity and the proven lack of influence of creating an instability by doing push ups on / with a Swiss Ball in various forms (Lehman. 2006) on pectoralis activity, it would be prudent to assume similar i.e. no effects on pecs activity with any of the instability devices in this study.

At least for the TRX system which is by any means the device that makes the most significant difference in how you perform the exercise, though, the muscle activity of the pectoralis major has been shown to increase. In the corresponding 2013 study by Snarr, the increase varies largely from one participant to the other, but reaches a stat. sign. plus 16% on average (Snarr. 2013a).
With that being said let's take a look at the results, of which I'd hope that you'd still agree that they're really interesting:
Figure 2: Muscle activity during regular floor pushup and push-up using the instability devices; all data expressed relative to respective values in the floor push-up trial; non-sign. effects were observed only for the delts (Borreani. 2015).
As you can see, there were no significant differences for the DELT muscle between the regular push-up an the device assisted push-up conditions. However, statistically significant differences were found among the different conditions for ...
Figure 3: Some orientation for those of you that don't know the muscle names: (1) anterior deltoids, (2) serratus anterior, (3) rectus femoris (4) lumbar multifidus
  • the serratus anterior, where all exercises being at least 2.9x more effective than the regular push-up
  • the rectus femoris, where the TRX Suspension System really excels, while the Stability Disc and Fitness Dome offer only minor advantages
  • the lumbar multifidus, where the all devices triggered an increase in muscle activation, yet only the difference for the TRX Suspension System reached statistical significance
If we go by the statistical standards, Borreani et al. are thus right to say that "not all unstable devices enhance muscle activation compared to traditional push-ups" (ibid. 2015). If we take a look at the relative mean activation patterns, though. All devices have some advantages.
Push ups in a TRX Suspension System are at least as effective as the classic crunch for the rectus abdomins aka the "abs" (Snarr. 2013b). In a previous study, Snarr et al. have also observed increased EMG activity in the pectoralis major (chest / pecs). Evidence I already discussed in the previous light blue box.
So what's the best device, then? I guess that's difficult to say, because "best" relative, in this case: While you and your trainer will have to decide which muscles are worth getting some extra attention, I personally would probably use the TRX System. It is the only device that leads to statistical significant increases in muscle activity in all, but the most common synergist of the pectoralis, the front delts, and makes the classic push up an even better core stability exercise. In fact, a previous study by Snarr et al. (2013b) shows that it is more than on par with the crunch when it comes to rectus abdominis (abs) activity. In conjunction w/ the previously discussed evidence that it increases pecs activity by 16% (see blue box), that's quite convincing for me, although it takes some time until you master the TRX system.

And what about the other devices? Well if you look at the data, the only good reason to use Wobble Board and Fitness Dome excel is the increased serratus activity, for which I'd rather do the good old dumbbell pullovers across a bench (you can also use a water crate in the home gym ;-). Pullovers may not "widen the chest", as some bodybuilders say, but they will create the illusion of doing just that by making the serratus grow (see muscle position in figure 3). Ah,... and the word "illusion" brings me to the last message of the bottom line: The mere fact that the EMG activity increases by X% does not mean that the muscle size and strength gains will increase by the same amount - it just increases the chance that both will increase  | Comment on Facebook!
  • Borreani, Sebastien, et al. "Muscle activation during push-ups performed under stable and unstable conditions." Journal of Exercise Science & Fitness (2015).
  • Cogley, Robert M., et al. "Comparison of muscle activation using various hand positions during the push-up exercise." The Journal of Strength & Conditioning Research 19.3 (2005): 628-633.
  • Lehman, Gregory J., et al. "Shoulder muscle EMG activity during push up variations on and off a Swiss ball." Dynamic Medicine 5.1 (2006): 7.
  • Snarr, Ronald L., and Michael R. Esco. "Electromyographic comparison of traditional and suspension push-ups." Journal of human kinetics 39.1 (2013a): 75-83.
  • Snarr, Ronald L., et al. "Electromyographic activity of rectus abdominis during a suspension push-up compared to traditional exercises." Age (yrs) 25.3.91 (2013b): 22-33.