It's a popular question: "what are the best rest periods for muscle growth?"
Most gym goers have an opinion on this.
Everyone wants to know how to gain muscle, and the best way to get there.
And whilst there's a lot of misinformation in regards to this topic spread frequently, the currently available scientific data sheds some light on what choices we should be making.
THE RESEARCH
Studies show that SHORTER rest periods (approx 30-60 seconds) lead to an increase in growth hormone and testosterone (1,2,3).
Perfect! So it looks as if shorter rest periods are the way forward for muscle growth, right?
WRONG!
Furthermore to the above link, other research (4) into leg training has found a 45 fold increase in testosterone between subjects, yet all were still able to increase muscle growth at the same rate.
To quote Daniel West, the lead author of the study from the Department of Kinsiology at McMaster University in Cananda:
“A popular mindset for weightlifters is that increased levels of hormones after exercise play a key role in building muscle, that is simply not the case........while testosterone is definitely anabolic and promotes muscle growth in men and women at high doses, such as those used during steroid abuse, our findings show that naturally occurring levels of testosterone do not influence the rate of muscle protein synthesis.”
Adding further to the myth of growth hormone - and although it has been found to grow muscle in the elderly when it is injected (5), the same benefits aren't seen in healthy adults, who obviously aren't deficient in the hormone.
To quote from one (7) paper:
"In healthy adults, neither growth hormone nor IGF-1 has or enhances the hypertrophic effects of exercise."
Furthermore, because I know so many people will find this hard to believe, another study (8) was done into 16 men, from the ages of 21-34 who were put into a strength training and growth hormone group - or a strength training and placebo group.
And what were the results?
There was an increase in fat free mass, but on muscle mass? There was NO increase.
To quote the researchers:
"In the young men studied, resistance exercise with or without GROWTH HORMONE resulted in similar increments in muscle size, strength, and muscle protein synthesis, indicating that 1) the larger increase in FAT FREE MASS with GROWTH HORMONE treatment was probably due to an increase in lean tissue other than skeletal muscle and 2) resistance training supplemented with GROWTH HORMONE did not further enhance muscle anabolism and function.”
So if INJECTIONS of growth hormone aren't benefiting young men, then times between sets to increase it, certainly won't make magic in your muscle cells either!
So the idea of having SHORTER rest periods to increase these hormones and your muscles gains, is simply not a scientfically good one.
SO WHAT ABOUT LONGER REST PERIODS?
According to a recent study published in the Journal of Strength and Conditioning Research, resting 2-3 minutes between sets as opposed to just one minute, will yield superior muscle gains in UNTRAINED subjects, who in this case trained for a period of ten weeks.
It's accepted that the longer rest time allows for one's ATP to resynthesise adequetly, and for optimal strength to return so maximum intensity can be put into the next set.
To determine who made the biggest gains, the scientists measured the participants arm size BEFORE and AFTER the study.
The group who rested a minute boasted a 5% increase to their arm size, while those who rested 2 and a half minutes between sets, had a 12% increase!
So the 2-3 minute rest period seems to be the superior option when it comes to untrained subjects.
TRAINED SUBJECTS
Another study (9) looked at muscle growth in a 6 month period of 13 recreationally resistance trained males.
In one 3 month period, the subjects rested for 2 minutes, and in another 3 month period, they rested 5.
The training involved leg presses and squats, and both periods were matched for volume (important, which we will get too later).
Significant increases in the quadriceps muscle cross-sectional area (4%) were seen over the 6-months - but both 3-month training periods yielded similar gains in muscle mass.
Although it wasn't a super low rest period (30 seconds or a minute), this study suggests that in trained subjects, if volume is kept the same, then rest periods can be either 2 minutes or 5, with identical muscle hypertrophy achieved!
THE 30 SECOND REST PERIODS
Another study (10) examined 30 second rest periods and 2 minute rest periods, into 20 young recreationally-trained subjects, who under went squat and bench press training.
In the first 2 weeks, the men performed 3 sets of 10 – 12RM with 2-minute rests.
In the next 6 weeks of training, they performed 4 sets of 8 – 10RM.
The constant-rest group rested 2-minutes between sets, while the decreasing-rest group rested with gradually shorter rests periods - 2 minutes decreasing to 30 seconds, over the 6 weeks of training.
WHAT THEY FOUND
There were no large differences in muscle growth between the two training groups. So gradually decreasing rest periods doesn't seem to be that detrimental.
This being said - the group who gradually rested less to the 30 second period - did lose strength at the end of the study.
So if you're a power lifter, obviously reducing rest periods is NOT the way forward.
FURTHER RESEARCH
Another study (11) into 12 untrained subjects looked to examine a 1 minute rest period and a 2.5 minute rest period, in the context of squats and bench presses.
But here, unlike in the above study (9) - volume WAS NOT matched.
The researchers observed that arm cross-sectional area increased more with long rest periods (7.2%) than with the shorter rest periods (2.9%) - but they did not notice any significant differences in respect of leg size.
CONCLUSION
Training to increase hormones in the hope of more muscle growth - will not being you any noticable results.
However, hormones aside, there's not a whole lot of research out there in order to make a definite conclusion into rest periods and muscle growth, whilst disregarding volume.
However, one thing seems to be relatively clear - if you want to reduce your rest periods, make sure you don't reduce volume as well, by beginning another set when you're not ready to perform effectively. It's clear that this can be negative for muscle growth.
It seems a rest period of 90 seconds to 120 seconds is a safe bet, to ensure muscle hypertrophy isn't hindered.
There's no question more research is needed, but gradually reducing rest periods down to 30 seconds [as evident in reference (10)] doesn't seem to be detrimental to muscle growth.
So stick to the 90-120 rest period, and if you want to drop as low as 30 seconds, do so gradually, to ensure "dem gainsz" are not sacrificed and your muscle and fitness goals stay well on track.
"STAY FIT, STAY FLEXED!"
FURTHER READING ON FIT'N'FLEXED: THE BEST REP RANGE FOR MUSCLE GROWTH
REFERENCES
(1) Kraemer, W. J., Marchitelli, L., Gordon, S. E., Harman, E., Dziados, J. E., Mello, R., Frykman, P., McCurry, D., & Fleck, S. J. (1990). Hormonal and growth factor responses to heavy resistance exercise protocols. Journal of Applied Physiology, 1442-1450.
(2) Kraemer, W. J., Gordon, S.E., Fleck, S. J., Marchitelli, L. J., Mello, R., Dziados, J.E., Friedl, K., Harman, E., Maresh, C., & Fry, A.C. (1991). Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. International Journal of Sports Medicine, 228-325.
(3) Smilios, I., Pilianidis, T., Karamouzis, M., & Tokmakidis, S. P. (2003). Hormonal responses after varied resistance exercise protocols. Medicine & Science in Sports & Exercise, 644-654. Retrieved March 4, 2007, from Ovid database.
(4) West DWD, Phillips SM. Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. European Journal of Applied Physiology. July 2012, Volume 112, Isue 7, pp 2693-2702.
(5) Liu H, et al. Systemic review: The safety and efficacy of growth hormone in the healthy elderly. Annals of Internal Medicine. 2007;146:104.
(6) Welle S, Thornton C, Statt M, McHenry B. Growth hormone increases muscle mass and strength but does not rejuvenate myofibrillar protein synthesis in healthy subjects over 60 years old. J CLin Endocrinol Metab. 1996 sep;81(9):3239-43.
(7) Velloso CP. Regulation of muscle mass by growth hormone and IGF-1. Br J Pharmacol. June 2008;154(3):557-568.
(8) Yarasheski KE, Campbell JA, Smith K, Rennie MJ, Holloszy JO, Bier DM. Effect of growth hormone and resistance exercise on muscle growth in young men. Am J Physiol. 1992 Mar;262(3 Pt 1):E261-7.
(9) Ahtiainen JP, Pakarinen A, Alen M, Kraemer WJ, Hakkinen K. Short vs. long rest period between the sets in hypertrophic resistance training: influence on muscle strength, size, and hormonal adaptations in trained men. J Strength Cond Res. 2005 Aug;19(3):572-82.
(10) De Souza TP Jr, Fleck SJ, Simao R, Dubas JP, Pereira B, de Brito Pacheco EM, da Silva AC, de Oliveira PR. Comparison between constant and decreasing rest intervals: influence on maximal strength and hypertrophy. J Strength Cond Res. 2010 Jul;24(7):1843-50. doi: 10.1519/JSC.0b013e3181ddae4a.
(11) Buresh R, Berg K, French J. The effect of resistive exercise rest interval on hormonal response, strength, and hypertrophy with training. J Strength Cond Res. 2009 Jan;23(1):62-71. doi: 10.1519/JSC.0b013e318185f14a.
Author
Dayne Hudson