Friday, August 15, 2014

Significant Strength Gains With All-Out Single-Set Full Body Pre-Exhaustion Training - Advantage Over Regular 'Multi - Joint Exercise First' Workouts is Yet Non-Significant

Does it really make sense to pre-exhaust the pectoralis major on cable crosses before you bench to increase your strength and size gains?
You will probably have heard about pre-exhaustion and the idea that doing isolation before compound exercises could help increase the strain on the target muscle over the classic "compound exercise first" training.

In fact, pre-exhaustion training (PreEx) is often recommended for advanced trainees to break plateaus (Darden 2004; Baechle. 2008); and that in spite of the fact that evidence that would support its efficacy from chronic resistance training studies is scarce / non-existent. Reason enough for James Peter Fisher and his colleagues from the Southampton Solent University, Discover Strength and the Manchester Metropolitan University to "determine the effects of a 12-week PreEx training intervention upon muscular strength and body composition." (Fisher. 2014).
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To this ends, the scientists randomized their 39 participants with at least 6 months resistance training experience and no medical condition to one of the following three training groups:
  • PE: Classic pre-exhaustion with isolation before compound exercise and no rest in-between
  • PER: Same as PE, but with 60s rest periods in-between
  • Control: Same exercises as in PE, but with compound exercise first
Training was performed 2 times per week (with at least 48 h between sessions) for 12 weeks. Each exercise was performed for 1 set per training session at a 2:4 repetition duration until momentary muscular failure.
Table 1: Overview of the exercises in the pre-exhaustion and classic training groups (Fisher. 2014)
Once participants were able to perform more than 12 repetitions before achieving MMF, load was increased by 5%. The PE group performed isolation exercises followed by compound exercises with as little rest as logistically possible (assessed prior to the study to be ≤5 s between exercises based upon their placement in the facility). The PE group rested 120 s between finishing each compound exercise and beginning the next isolation exercise (i.e., between chest press and leg extension, and between leg press and pull-over). They then rested 60 s between pull-down, abdominal flexion, and lumbar extension exercises.

Figure 1: Mean strength changes and 95% confidence intervals for each group and exercise (Fisher. 2014)
The PER group performed the same exercises in the same order but rested 60 s between each exercise, removing the PreEx method whilst maintaining the same overall rest duration and exercise order.

The CON group performed the same exercises in the following order, prioritizing compound exercises: chest press, leg press, pull-down, pec-fly, leg extension, pull-over, abdominal flexion, and lumbar extension. They rested 60 s between each exercise and performed a similar training as 90%+ of the trainees.

As the data in Figure 1 shows, there were no statistical significant effects of the training modalities on the strength gains on chest press, leg press and pull-down. What is interesting, though, is the slightly higher strength gain in the pre-exhaust + rest group (PER | light grey), which would suggest that pre-exhaustion, albeit with adequate rest between the "exhaustion" exercise and the subsequent compound exercise can help trainees with adequate training experience (here >6 months) bust through plateaus.
Keep in mind - Change triggers gains! One thing we must not forget, though, is that any change in your training regimen can provide an important new growth stimulus. In view of the fact that most trainees train according to the classic regimen, the increased strength gains in the CON vs. PER group may in fact have been the result of a general change in training style which does not necessarily have to be related to the pre-exhaustion technique.
A brief glance at the corresponding changes in body composition are yet less exciting. Despite the (non-significantly) higher strength gains in the pre-exhaustion + rest (PER) group, their body composition did not benefit from the change in training style.
Figure 2: Changes in body composition 95% confidence intervals min vs. max (Fisher. 2014)
I deliberately plotted the minimal and maximal values of the 95% confidence intervals in Figure 2 instead of the mean values or effect sizes, because the large difference between the former gives you a much better idea of the highly individual effects of the three training regimen. It should be obvious that the results of the study hand don't allow for a definitive definitive statement like "pre-exhaustion is better" or "... is worse than classic" training to build muscle / lose fat / build strength.
The influence of rest times has recently been reviewed by Menno Henselmans and Brad J. Schoenfeld who conclude that "The relationship between the rest interval-mediated effect on immune system response, muscle damage, metabolic stress, or energy production capacity and muscle hypertrophy is still ambiguous and largely theoretical. In conclusion, the literature does not support the hypothesis that training for muscle hypertrophy requires shorter rest intervals than training for strength development or that predetermined rest intervals are preferable to auto- regulated rest periods in this regard." (Henselmans. 2014)
Bottom line: I would understand if you were disappointed... so was I. The Fisher study does after all not provide a definitive answer to the question, whether the initially referenced recommendation to "pre-exhaust" to bust a plateau is solid or belongs to the realm of scientifically unwarrantable broscience. The only definite result is after all that "considerable improvements in strength are possible in trained participants when performing single set per exercise full-body RT to MMF [momentary muscular failure]" (Fisher. 2014).

The central message may thus be that strength increases are possible in a far more time-efficient manner than it would be the case for anyone who follows the recommendations of the American College of Sports Medicine (Ratamess et al. 2009) which suggest larger volumes of exercise, heavier loads (and accordingly lower repetition ranges), and large interset/inter-exercise rest intervals for trained participants. Whether this is best achieved doing pre-exhaustion with or without rest intervals and whether and in which way the results would differ for someone training on a three-way split program with a higher volume will yet still have to be elucidated | Comment on Facebook!
  • Baechle, T.R., and Earle, R.W. 2008. Essentials of Strength Training and Conditioning. 3rd Ed. Human Kinetics Publishing Company, Champaign, Ill., USA.
  • Darden, E. 2004. The New High Intensity Training. Rodale, USA.
  • Fisher, James Peter, et al. "The effects of pre-exhaustion, exercise order, and rest intervals in a full-body resistance training intervention." Applied Physiology, Nutrition, and Metabolism 39.999 (2014): 1-6.
  • Henselmans, Menno, and Brad J. Schoenfeld. "The Effect of Inter-Set Rest Intervals on Resistance Exercise-Induced Muscle Hypertrophy." Sports Medicine (2014): 1-9.
  • Ratamess, N.A., Brent, A.A., Evetoch, T.K., et al. "Progression models in resistance Training for Healthy Adults." Med. Sci. Sports. Exerc. 41, 3 (2009): 687–708.