Longer Rest Periods Compromise Adaptational Response in Resistance Training Older Men in 12 Week Study

Best-agers listen up: If you want to make progress, socialize after your workouts and stick to rest periods in the 60-90s range.

Best-agers, listen up! If you are the kind of person who likes to chat for four minutes between his / her sets you are not just wasting time. You are also making your workouts less effective. While there is little evidence that there are major differences between rest times of 60s and 90s, a recent study from the Division of Biokinesiology and Physical Therapy at the Clinical Exercise Research Center of the University of Southern California is not the first study to suggest that resting longer than maximally 120s is going to compromise the changes in body composition, muscular performance, and functional performance that occur in response to resistance training.

I have to admit, with a mean age of 70.3 years, the 22 male volunteers of said study don't qualify as the "classic" gymrat. On the other hand, you will probably have heard the argument that aging muscle cannot sustain the same extent of high intensity hammering that's highly productive in younger folks against.
Against that background, it's actually all the more surprising that the 11 men in the 60s rest period groups of this recent 4 weeks resistance training study saw significantly greater increase in lean muscle mass, bench press & leg press 1RM max, performance on the pull-down and several parameters of functional performance (not shown in Figure 1).

Figure 1: Changes in body composition and strength after 8 and 12 weeks; expressed relative to the values that were measured after the 4-week pre-training phase that was identical for both groups (Villanueva. 2014)

Except from the rest times, the periodized strength training regimen was 100% identical for both groups. This means that all 22 study subjects performed the same progressive total body resistance training program which was preluded by a 4-week familiarization protocol that was 100% identical for both groups:

• Training frequency: 3 days/week for the 4-week training cycle
• Sets / reps: 2 to 4 sets with 15 to 8 repetitions (set number increased, rep number decreased over time)
• Exercise number: Four to six exercises per workout

Only after the subjects had completed the first four weeks of training they were paired based on the similarity of their flat bench machine chest press 1-RM and randomly placed into one of the two groups: The SS = short (60s) and the SL = long (240s) rest group. As the scientists say they chose

"this strength outcome measure, because previous work from our lab has indicated there is relatively less variability among study participants with chest press 1-RM val ues, versus leg press 1-RM values, and, therefore, it would allow us to more easily randomize and create two treatment groups that are similar in (upper body maximum) strength.

In the following 8-week 'actual' study period the subjects were subjected to a progressive total-body resistance training program emphasizing development of upper and lower body strength.

• Training frequency: 3 days/week for 8 weeks by both groups (SS and SL)
• Sets / reps: sets ranged from 2 to 3, repetitions from 6 to 4
• Exercise number: 4–6 exercises

During this active study period, the only difference in program design between the two strength RT groups in was the rest interval length utilized between sets: 60 s (SS group) versus 4 min (SL group).

"Throughout the entire resistance training program, all sets were performed maximally for the assigned number of repetitions and with proper lifting technique, and loads were adjusted in accordance with recovery and performance, across the repeated sets progression.

Furthermore, it is important to note that study participants were never expected to perform sets to absolute muscular failure; given an appropriate loading progression, with alterations in set/repetition schemes throughout and across microcycles (i.e., a series of 3 training sessions), the repetition maximum assignments allowed for successful completion of the assigned number of repetitions at the load(s) prescribed, across multiple sets, and with minimal need for assistance/'spotting'" (Villanueva. 2014.)

Now this certainly sounds as if the protocol was realistic. But there is one major difference that puts a question mark behind the results of the study: usually regimen with long and short rest times differ significantly in the number of sets and the number of reps. Thus it is possible that future studies using different protocols for both groups would yield different results.
References:

• Buresh, Robert, Kris Berg, and Jeffrey French. "The effect of resistive exercise rest interval on hormonal response, strength, and hypertrophy with training." The Journal of Strength & Conditioning Research 23.1 (2009): 62-71.
• de Salles, Belmiro Freitas, et al. "Rest interval between sets in strength training." Sports Medicine 39.9 (2009): 765-777.
• Villanueva, Matthew G., Christianne Joy Lane, and E. Todd Schroeder. "Short rest interval lengths between sets optimally enhance body composition and performance with 8 weeks of strength resistance training in older men." European journal of applied physiology (2014): 1-14.
• Willardson, Jeffrey M., and Lee N. Burkett. "The effect of different rest intervals between sets on volume components and strength gains." The Journal of Strength & Conditioning Research 22.1 (2008): 146-152.
• Yang, Yifan, et al. "Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men." British Journal of Nutrition 108.10 (2012): 1780-1788.