Friday, May 24, 2013

Dumbbell Chest & Shoulder Training Shoot Out: New EMG Data from Experienced and Novice Female Lifters

Does a woman's pectoralis react the same way to dumbbell bench, incline and shoulder presses as the one of their male training partners? Does it make a difference whether you are a novice or an advanced trainee? What about light vs. heavy weights - any effect on the activation patterns of pectoralis, delts, trapezius & co? Learn the answers to these & other questions in today's SuppVersity article (photo bodybuilding.com)
The SuppVersity EMG Series is still one of the the most popular article series, here at the SuppVersity and that despite the fact that I guess most of you will already know the results by heart. Therefore I am happy to present you some additional data from a recently conducted study from the Biodynamics and Human Performance Center at the Armstrong Atlantic State University in Abercorn. The study that was published in the Journal of Sports Medicine a couple of days ago is - according to the authors - the first to investigate, whether the previously observed differences in muscular activation patterns in response to modified trunk inclination angle on muscle activation using barbells and Smith machines in men would occur in women, as well.

Another distinctive feature of the experimental protocol, Joshua Luczak, Andy Bosak, and Bryan L. Riemann devised is the use of both experienced and novice trainees and the separate analysis of the eccentric and concentric potion of the dumbbell bench press, incline bench press and shoulder press.

Who? What? How?

The researchers recruited 24 healthy college-aged (mean age 22.5 years) recreational female athletes as subjects and divided them into two groups, twelve per group, based on their experience with upper body weight training.
"One group was identified as experienced resistance trained exercisers by regularly participating in upper body resistance exercise at least 1–3 times per week for the last six months. The second group was comprised of novice resistance trained females who did not regularly participate in upper body resistance training exercises but instead were physically active in cardiovascular exercise at least 1–3 times per week." (Lukczak. 2013)
Within the 2-way repeated measures design of the study the exercise protocols were administered in a
between-subjects counterbalanced order, to ...
"[...] measure muscle activity in the anterior deltoid, pectoralis major (clavicular and sternal portions), and upper trapezius muscles by way of surface  electromyography data collection during flat bench (0° trunk inclination), incline bench (45°), and shoulder (85°) presses and then compare the muscle activation data between the novice and experienced groups as well as between the different exercises during the concentric and eccentric phases." (Lukczak. 2013)
After being familiarized with the correct execution of the exercises, the participants completed one set of five repetitions of each of the exercises with pretty light (4.5 kg) dumbbells. The order of the exercises was completed according to the counterbalanced protocol that each subject was assigned. Initiation of each set of repetitions was self-initiated and three minutes of rest were given between sets.
Figure 1: Normalized EMG activity for all subjects (no inter-group differences measured) during the dumbbell bench, inlcine and shoulder press (Lukczak. 2013)
Due to the use of the light weights I had to normalize the EMG data on a per muscle base before plotting it in figure 1. What you are seeing here are thus not the absolute values, but the EMG activity expressed relative to the mean activation pattern for a given muscle group on the concentric / eccentric potion of the exercise.... hah? I guess, I better give you an example:
  • the absolute EMG value for the upper trapezius activity during the concentric phase of the bench, the incline and the shoulder press were 103.5, 374.0 and 1,164.7, respectively
It goes without saying that plotting these values would have made it very difficult to read the diagram, so I calculated the mean of these three values and plotted the ratio of the actually measured EMG value to this very mean - got it?

But didn't we know most of that already?

What we knew already: According to the study the SuppVersity EMG Series is based on, the best exercises for the pectoralis major using standard equipment are:
  1. BB Bench Press
  2. Cable Cross*
  3. DB Bench Press
  4. Pec Deck
  5. DB Flys
  6. DB Pullovers
* the cable cross exercise should be performed actually crossing one's arms low before your body (learn more)
Basically the way the data is displayed does not really change anything about what it's telling you and that's more or less what both previous studies and bro-science have told you as well:
"The results of this study largely confirm previous research related to performing these exercises with barbells. Specifically, the bench and incline presses produced the greatest activation for the two portions of the pectoralis major muscle, while the shoulder press elicited the greatest activation for the anterior deltoid and upper trapezius muscles." (Lukczak. 2013)
Moroever, the hypothesis that the activation patterns of novice and advanced trainees would differ was not confirmed. When the form is picture perfect and the weight light enough to keep this picture perfect form over the whole set, the activation patterns are identical. In that, it's actually important to point out that the same results have been observed in previous studies using different weights (in % of 1RM) for rookies and pros (Lagally. 2004; Schick. 2010) - so this is not a consequence of using "too little weight", guys ;-)

Ah, and lastly, the observed increased activation of the muscle during the concentric phase of pressing movements are likely related to the light weights, used in the study at hand, which did, as the scientists point out, not require "for as much stabilization of the weight during the descent" compared to what is required during the completion of the same exercise with higher weights.This hypothesis is supported by previous studies by Goodman et al. (2008) and Uribe et al. (2010), in which the subjects had to bench close to their 1RM or with still submaximal  but heavy weights and where no differences in the activation patterns between the eccentric and concentric phase were observed.



Bottom line: I am sorry to say that, but the study at hand does not really bring anything new to the table. You want more shoulder involvement? Increase the angle! ... ah, and don't forget that the eccentric potion of the exercise has it's merits as well - specifically, when you are using practically relevant loads in the 70% 1-RM range. Now get back to the gym and rock the weights!

References:
  • Goodman CA, Pearce AJ, Nicholes CJ, Gatt BM, Fairweather IH. No difference in 1RM strength and muscle activation during the barbell chest press on a stable and unstable surface. J Strength Cond Res. 2008 Jan;22(1):88-94.
  • Lagally KM, McCaw ST, Young GT, Medema HC, Thomas DQ. Ratings of perceived exertion and muscle activity during the bench press exercise in recreational and novice lifters. J Strength Cond Res. 2004 May;18(2):359-64.
  • Luczak L, Bosak A, Riemann BL. Shoulder Muscle Activation of Novice and Resistance Trained Women during Variations of Dumbbell Press Exercises. Journal of Sports Medicine. 2013; article ID 612650.
  • Schick EE, Coburn JW, Brown LE, Judelson DA, Khamoui AV, Tran TT, Uribe BP. A comparison of muscle activation between a Smith machine and free weight bench press. J Strength Cond Res. 2010 Mar;24(3):779-84.
  • Uribe BP, Coburn JW, Brown LE, Judelson DA, Khamoui AV, Nguyen D. Muscle activation when performing the chest press and shoulder press on a stable bench vs. a Swiss ball. J Strength Cond Res. 2010 Apr;24(4):1028-33.