|Up your strength /check! Up your power /check! Up your muscle gains in the long term /likely!|
Now things are getting a little complicated, because contrary to a classic clustering regimen, where you would add weight to the bar, do say 8 reps, take 10 breaths and rep out the other two, the intra-set rest (IRS) period protocol in the Oliver study employed a tightly controlled and not an "ad hoc" variety of "clustering". Contrary to the control group who performed a regular 4x10 routine, the IRS group broke their 4 sets of 10 with 120s rest between sets up to eight sets of five with only 60s of rest in-between the exercises (see table 1 for more details)
|Table 1: Overview over the workout program (adapted based on Oliver 2013)|
Remember: This is not "clustering"! When you "cluster" your training volume will increase, the IRS protocol, on the other hand, is standardized in a way that the total workload will (and in in the study at hand did) remain the same.The participants of the study had all been doing upper + lower body resistance training for at least 2 years and were thus familiar with the basics of strength training, before the study they received nutritional counseling which is probably the reason that all of them increased their protein intake significantly (ca. +50g to ~190-200g/day; no inter-group difference).
The same goes for the changes in muscle fiber and body composition. All subjects experience an increase in MHC-IIa fibers (glycolytic) and gained lean mass continuously. Unfortunately, they also gained body fat, so that the body fat % (DEXA measured) did not change at all.
The power and strength advantage
What did however react to the modified rest times were the changes in strength and power on all the major lifts. According to Oliver, et al.
Similar differences were observed on the power output strength, where the group difference at both 8 weeks (ISR, 151.0±74.0 W; STD, 97.5±60.9 W; p = 0.084) and 12 weeks (ISR, 282.1±104.1 W; STD, 204.9±70.2 W; p = 0.063) approached significance with subjects in ISR showing a greater increase. Interestingly, the advantage became even more obvious, when the changes for normalized for the subjects' body weight (from p = 0.084 to p = 0.016 and p = 0.063 to p = 0.038 after 8 and 12 weeks, respectively - that means what may be at best a trend on an absolute level is a statistically significant advantage if you take the muscle mass into account, as well)
"Only subjects in ISR experienced an increase [in 1RM bench press & squats] at 4, 8 and 12 weeks. This corresponded to greater increases at 4 (ISR, 6.6±6.6 kg; STD, -1.4±6.2 kg; p= 0.012), 8 (ISR, 9.9±6.8 kg; STD, 2.9±5.8 kg, p = 0.016) and 12 (ISR, 15.1±8.3 kg; STD, 9.1±3.7 kg; p = 0.051) weeks.
Table 2: Effect size and qual. inferences on intergroup difference; (t)rivial, s - (s)mall, (m)edium., (l)arge (Oilver. 2013).
[...] Again, only ISR increased at 4, 8 and 12 weeks. Greater percent increase from baseline was observed in ISR at 4 and 8 weeks (p = 0.017 and 0.034, respectively), with 12 weeks approaching significance (p = 0.082)." (Oliver. 2013)
Bottom line: It sure looks as if IRS would in fact be a viable training strategy for anyone training for muscle hypertrophy, strength and power. Neither the workload, nor the workout time changes and still the results improve. And I can hardly phrase it better than Oliver et al. did:
What? Oh, yes... I will tell you if the researchers ever conduct this study. To be honest, I am yet pretty sure that this is not going to happen. After all, the results won't be patentable and since we are dealing with healthy people (worse athletes!) the governments of the Western Obesity Belt are more likely to burn a few additional millions to find new pharmacological methods to prolong the misery of the increasingly obese majority of their citizens - I mean, who would vote for them if they told people that we already had the solution to the obesity epidemic, but it was not available in convenient pill form?
"Based on these results, it could be suggested the incorporation of ISR in the hypertrophic phase of a traditional or non-traditional periodized training program would allow for greater improvements in strength and power.
Suggested read: "Training for Size & Strength: Does Rest Matter? Study Finds 7-9% Greater Increase in Muscle Size With Decreasing Rest Periods." (read more)
Whether these improvements would result in greater gains in strength and power output over an entire mesocycle is unknown, but hypothetically entering the strength and power phases of a training mesocycle at higher performance ability (strength and power) would allow a continued improvement above that achieved during traditional training models." (Oliver. 2013)
- Oliver JM, Jagim AR, Sanchez AC, Mardock MA, Kelly KA, Meredith HJ, Smith GL, Greenwood M, Parker JL, Riechman SE, Fluckey JD, Crouse SF, Kreider RB. Greater Gains In Strength And Power With Intra-Set Rest Intervals In Hypertrophic Training. J Strength Cond Res. 2013 Jun 3. [Epub ahead of print]