Strength: What Does the Science Suggest?

I remember when I saw Ronnie Coleman’s training DVD “Cost of Redemption.” I highly recommend purchasing this DVD if you haven’t. It features Ronnie’s workouts including 160-pound dumbbell shoulder presses, 800-pound squats, 2,250+ -pound leg presses, 495-pound bench presses, 75-pound alternate curls and more!
Here is what’s really interesting: Ronnie sure as hell does not train like the bodybuilders in those other DVDs, and yet he was a 310-pound mass monster. He trained incredibly heavy, yet he was not following the traditional principle of 60-second rest periods for muscle mass.

In “Blood and Guts,” Dorian would rest sometimes up to five minutes after squats. After spending some time with Branch and talking to Brian Dobson at Metroflex Gym in Arlington, TX about how Ronnie trained, they trained very hard but often took anywhere from three- to five-minute rest periods. All of these champions certainly don’t train with the traditional bodybuilding routine that uses moderate weight with short rest periods (60 seconds or less), yet all of these guys are built like brick shithouses!

So if short rest periods— as preached for so many years— are the way to muscle growth, then why the fuck are these guys so big? In a recent issue of the journal Sports Medicine, there was a review of 35 studies examining acute responses and chronic adaptations, with rest interval length as the experimental variable. By tweaking your rest interval duration and your training routine, you can make some serious gains in strength and size.

The existing research demonstrates that altering the rest periods between sets can cause both acute and chronic adaptations in the endocrine and nervous system.5-7 By getting stronger, you will gradually be able to use heavier weights, which will allow for greater tension on a muscle and more muscle growth. One of the more intriguing studies regarding resistance exercise and rest duration involved college football players. One group rested one minute between sets, while the other group rested three minutes between sets. The group that rested three minutes was able to complete 10 repetitions between sets, while the ‘one-minute group’ was not able to complete the required 10 reps.8 This suggests that resting longer will allow you to handle a greater workload during a workout. I am sure you are saying, ‘Well… no shit!’ Let’s examine some of the research studies examining the role of rest period duration on the amount of weight you can handle in a training session.

Researchers compared 30-second and one- and two-minute rest intervals to the number of repetitions completed for the squat and bench press over 5 sets, with a constant 15 RM load. Significant declines in the number of repetitions occurred between the first and the fifth sets, irrespective of the rest interval. For both exercises, the two-minute rest interval resulted in significantly greater repetitions versus the 30-second rest interval. These results suggest that when short rest intervals are utilized to develop muscular endurance, the intensity (i.e., load) may need to be progressively lowered over subsequent sets to sustain repetitions within the range conducive to the training goal. Future research should establish the extent to which the resistance should be lowered between sets in order to sustain repetitions for muscular endurance training.9 So if bodybuilders are not looking to build endurance in the off-season, why use short rest periods?

If you are wondering what influences muscle recuperation between sets for maintaining power, it mostly points to phosphocreatine (PCr) levels in muscle. Physiological levels of PCr take four minutes to recover.10 If you start a set when PCr levels have not recovered, then hydrogen ions or lactic acid builds up in the muscle, and muscle strength is reduced. So remember, if you want full creatine reserves for your next lift, you need at least four minutes of rest between sets!

It is well-established that a reduction in pH, which causes large increases in lactic acid, reduces muscle strength.11 From a time perspective, using short rest periods allows for greater volume at the cost of using lighter weights. You may be able to significantly enhance muscle hypertrophy by spending more time in the gym, by using longer rest periods to spur new increases in muscle growth— as you would be able to place more tension on the muscle by using heavier weights, yet resting longer between sets so you can keep using the heavier poundages.

A study examined the effect of rest period duration on squat performance using one-, three-, and five-minute rest periods. Seventy-five percent of the group using one-minute rest periods completed the full second set; whereas 88 percent of the three-minute rest group completed the second set and 94 percent of the five-minute rest group completed the second set.12 I often change my rest period duration throughout the week, if I am rushed for time. Those one-minute minute rest periods are great for getting in and out of the gym, but on Saturday if I have a little bit more time, and I extend my rest duration to three to five minutes. This means I am in the gym longer, but I am able to complete more reps with a heavier weight— which results in more tension overload on that day.

Do Acute Increases In Anabolic Hormones Affect Muscle Hypertrophy?

Back in the ’90s, everyone trained with 60-second rest periods because it was overwhelmingly clear that short rest periods increased GH and testosterone.1-3 As years went by, only a few studies have been able to validate that short rest periods increase muscle hypertrophy. Remember, the acute anabolic hormone response doesn’t last long before returning to baseline again.

When I was in graduate school, my graduate advisor, Dr. Bammon, opened my eyes to intramuscular growth factors being the key for muscle growth. In this month’s Journal of Applied Physiology, another study came out, suggesting that short rest periods do not increase muscle hypertrophy. They had men train in either a low-exercise training condition or a high-exercise training condition. The way the researchers designed the study was brilliant!

The experimenters assigned men in the low-hormone condition (LH) to single-arm curls only, while in the high-hormone condition (HH), the contralateral arm performed the same arm-curl exercise followed immediately by a bout of leg-resistance exercises designed to elicit large increases in circulating hormones. Participants consumed 18 grams of whey protein immediately before exercise, and 18 grams at 90 minutes after absence and presence of elevated hormone concentrations, as well as to reduce variability in nutrition surrounding the exercise bout. Blood samples were taken immediately after the end of each trial.

Researchers found that including legs at the end of the arm workout increased GH, IGF-1 and testosterone as expected, but there was no increase in strength or muscle hypertrophy in the high-hormone group, as opposed to the low-hormone group. They did also not find out changes in protein synthesis, despite the marked increases in acute anabolic hormones.

These data suggest that exercise-induced hormone elevations do not stimulate muscle protein synthesis and are not necessary for hypertrophy.13 The researchers concluded the same thing professor Bammon told me— local mechanisms (intramuscular IGF-1, myostatin, androgen receptor, etc.) are of far greater relevance in regulating muscle protein accretion occurring with resistance training, and that acute changes in hormones, such as GH, IGF-1 and testosterone do not predict or in any way reflect a capacity for hypertrophy.

I have no doubt that using short rest periods is useful for burning fat as you approach the upcoming contest and may be helpful for stripping that last bit of fat off, but I don’t see how incorporating short rest periods year-round could be helpful.

Throwing the weights on the bar can lead to some use of muscle fibers that can’t be recruited during lighter-weight exercises. In exercise physiology there is the ‘Size Principle’ which states that while smaller motor units that typically innervate the less-fatigable type I muscle fibers are activated with low-effort activities (e.g., lower percentages of 1 RM), larger motor units that primarily innervate the greater force-generating type II fibers are recruited with higher-effort activities (e.g., higher percentage of 1 RM or with fatigue) and more importantly, type II fibers— which generally exhibit a greater hypertrophic response than type I fibers.

With this basic fact, realize that when you lift lighter, all the type I fibers are activated first, then the type II fibers are activated as the muscle fibers tire out. When you lift heavier, the muscle fibers begin to immediately utilize type II fibers for activation. Vascular occlusion accelerates local metabolically-induced fatigue and hastens the recruitment of type II muscle fibers to maintain work output, which has been demonstrated to elicit an increase in muscle protein synthesis.

In conclusion, if you’re not changing your rest period length, you may be missing out on some gains in both strength and size. Using shorter rest periods might be advantageous when competitions are coming closer so you can enhance GH secretion for fat loss, but the research can validate that short rest periods are useful for adding muscle mass and size.

It’s important to change up your routine, which means your rest period length as well. Try spending some time using longer rest periods and see if you can’t get some added size out of it. The review paper cited in the introduction mentioned that when training for muscular strength with loads less than 90 percent of 1 RM (up to 50 percent) for multiple sets, three- to five-minute rest intervals are necessary to maintain the number of repetitions performed per set within the prescribed zone— without great reductions in training intensity.4 The acute expression of muscular power was best maintained when including three- or five-minute rest intervals versus one-minute rest intervals between sets.

By: Robbie Durand


1. Kraemer WJ. Endocrine Responses to Resistance Exercise. In: Essentials of Strength and Conditioning, edited by Baechle TR and Earle RW. Champaign, IL: Human Kinetics, 373 2000, p. 91-114.

2. Kraemer WJ and Ratamess NA. Hormonal responses and adaptations to resistance exercise and training. Sports Med, 35: 339-361, 2005.

3. McCall GE, Byrnes WC, Fleck SJ, Dickinson A and Kraemer WJ. Acute and chronic hormonal responses to resistance training designed to promote muscle hypertrophy. Can J Appl Physiol, 24: 96-107, 1999.

4. Fujita S, Abe T, Drummond MJ, Cadenas JG, Dreyer HC, Sato Y, Volpi E & Rasmussen BB (2007a). Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol, 103, 903-9.

5. Kraemer WJ, Noble BJ, Clark MJ, et al. Physiologic responses to heavy-resistance exercise with very short rest periods. Int J Sports Med, 1987; 8: 247-52

6. Kraemer WJ, Marchitelli L, Gordon SE, et al. Hormonal and growth factor responses to heavy resistance exercise protocols. J Appl Physiol, 1990; 69: 1442-50

7. Kraemer WJ, Fleck SJ, Dziados JE, et al. Changes in hormonal concentrations after different heavy resistance exercise protocols in women. J Appl Physiol, 1993; 75: 594-604.

8. Kraemer WJ. A series of studies: the physiological basis for strength training in American football: fact over philosophy. J Strength Cond Res, 1997; 11: 131-42.

9. Willardson JM, Burkett LN. The effect of rest interval length on the sustainability of squat and bench press repetitions. J Strength Cond Res, 2006; 20: 400-3.

10. Harris RC, Edwards RH, Hultman E, et al. The time course of phosphorylcreatine resynthesis during recovery of the quadriceps muscle in man. Pflugers Arch, 1976; 28: 137-42.

11. Larson GD, Potteiger JA. A comparison of three different rest intervals between multiple squat bouts. J Strength Cond Res, 1997; 11: 115-8.

12. Matuszak ME, Fry AC, Weiss LW, et al. Effect of rest interval length on repeated 1 repetition maximum back squats. J Strength Cond Res, 2003; 17: 634-7.

West DW, Burd NA, Tang JE, Moore DR, Staples AW, Holwerda AM, Baker SK,

13. Phillips SM. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. J Appl Physiol, 2009 Nov 12.

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