DOES LESS REST BETWEEN SETS INCREASE TESTOSTERONE LEVELS?

SHORT REST PERIODS AND METABOLIC STRESS WORKOUTS REDUCE TRAINING VOLUME

Volume (sets x reps x weight) is a better driver of muscle growth than short rest periods.[3] When researchers used various rest periods and determined their effect on volume, short rest periods resulted in the shortest workout volume. Subjects performed the bench press in the 5–10 rep range. The rest intervals were: 30 seconds, 1 minute, 2 minutes, 3 minutes, and 5 minutes. The largest reductions in performance occurred with very short rest (<1 min), and performance was maintained during the first 3-4 sets when 3- and 5-min rest intervals were used.[4] This suggests that longer rest periods enable a larger work volume during exercise. Longer rest periods between sets reduce fatigue and enable you to regenerate more ATP (i.e., the body’s energy currency) for high-intensity exercise.

DOES WORKOUT OUT INCREASE TESTOSTERONE LEVELS MORE WITH HEAVIER WEIGHT?

A vast majority of the studies suggest that acute increases in anabolic hormones have no impact on muscle growth. Professor Stuart Phillips has led the charge in debunking the role of acute anabolic hormones and muscle growth. In a 2016 study, subjects trained with either a heavy weight, low repetitions (~75%-90% of a 1RM), or high repetitions (~30–50% of a 1RM). Despite an acute increase in anabolic hormones, there was no correlation between acute anabolic hormones and muscle growth; both groups increased muscle mass similarly.[5] One exciting finding from this study was that local androgen receptor concentration was correlated with increased muscle mass, suggesting that rather than systemic hormones (i.e., testosterone, GH), androgen receptor concentration are more important for muscle growth.

DOES WORKING OUT LEGS INCREASE TESTOSTERONE LEVELS?

The current research suggests that acute anabolic hormones play a lesser role in muscle growth than previously thought. Subjects were trained with either arm curls (low anabolic hormone exposure) or arm curls plus leg press and leg extension/leg curl at ∼90% of 10 RM (high anabolic hormone levels). It has been well documented that large multi-joint exercises like the leg press produce greater anabolic hormones than smaller joint exercises like the bicep curls. If acute anabolic hormones led to muscle growth, the arms training with leg training that resulted in greater anabolic hormone exposure should have resulted in greater muscle growth.

Despite arms plus legs workouts producing large increases in GH, testosterone, and IGF-1 levels, they found no differences in the arm size exercised under low or high anabolic hormone conditions after 15 weeks of training.[6] Based on the sum collection of all the studies, the acute anabolic hormone rise from exercise has a minor effect on muscle growth.[7]

METABOLIC STRESS, MUSCLE GROWTH, AND TESTOSTERONE

Research indicates that testosterone levels might not be the sole determinant of muscle growth. A study revealed that after 12 weeks of resistance training, there wasn’t a direct link between changes in testosterone and muscle fiber growth.[8] Notably, women, who generally have lower testosterone levels than men, can still achieve significant muscle growth through resistance training.[9]

Additionally, if the short-term spikes in Growth Hormone (GH) played a pivotal role in muscle growth, one might assume that morning workouts, when the body’s natural GH levels are at their peak, would be more effective. However, findings don’t support this theory. Despite higher GH levels in the morning, there’s no evidence suggesting morning training is more beneficial for muscle growth than afternoon sessions.[10]

In essence, the immediate anabolic effects of testosterone and GH might not be as crucial as once believed. Instead, applying tension to the muscle seems to be a more critical factor for muscle growth.

WHAT TO DO WHILE YOU ARE RESTING BETWEEN SETS TO SQUEEZE OUT MORE MUSCLE GROWTH

Training Tip: Instead of just sitting idle between sets, consider squeezing the muscle or performing an isometric contraction during your rest period. This can potentially enhance muscle growth, especially after compound movements. Bodybuilders often practice posing routines, which are essentially isometric poses, for hours before a show. These routines are not only challenging but can also be exhausting. Some even believe that these poses aid in muscle building. Supporting this belief, a 2014 study by Maeo et al. found that subjects who squeezed their biceps and triceps simultaneously without any weights for four seconds over 12 weeks experienced a 4% muscle growth in these areas without using any external resistance.[11]

STUDIES ON FLEXING BETWEEN SETS

Research suggests that isometric contractions, or squeezing the muscle hard, can promote muscle growth when combined with resistance exercises. In a study, participants who incorporated these contractions between sets observed more muscle growth in their legs. However, areas like the biceps and triceps didn’t show the same results compared to those who simply rested.[12] These participants performed a five-second isometric contraction or flexed after each set. Adding this to your rest period might boost muscle growth. Another technique is to shake the muscles for 30 seconds between exercises, which some believe enhances strength.[13] Incorporating muscle-flexing during rest periods could offer additional muscle growth benefits.

KEY POINTS

• Acute anabolic hormones (GH and testosterone) do not impact muscle growth based on current research.
  

  REFERENCES

  1.  Juha P. Ahtiainen et al., “Short vs. Long Rest Period between the Sets in Hypertrophic Resistance Training: Influence on Muscle Strength, Size, and Hormonal Adaptations in Trained Men,” Journal of Strength and Conditioning Research 19, no. 3 (August 2005): 572–82.

  2. S. Dobs et al., “Pharmacokinetics, Efficacy, and Safety of a Permeation-Enhanced Testosterone Transdermal System in Comparison with Bi-Weekly Injections of Testosterone Enanthate for the Treatment of Hypogonadal Men,” The Journal of Clinical Endocrinology and Metabolism 84, no. 10 (October 1999): 3469–78.

  3. Baz-Valle, E., Balsalobre-Fernández, C., Alix-Fages, C., & Santos-Concejero, J. (2022). A Systematic Review of The Effects of Different Resistance Training Volumes on Muscle Hypertrophy. Journal of human kinetics, 81, 199–210.

  4. Robert W. Morton et al., “Neither Load nor Systemic Hormones Determine Resistance Training-Mediated Hypertrophy or Strength Gains in Resistance-Trained Young Men,” Journal of Applied Physiology 121, no. 1 (July 1, 2016): 129–38.

  5. Daniel W. D. West et al., “Elevations in Ostensibly Anabolic Hormones with Resistance Exercise Enhance Neither Training-Induced Muscle Hypertrophy nor Strength of the Elbow Flexors,” Journal of Applied Physiology 108, no. 1 (January 2010): 60–67.

  6. E. Todd Schroeder et al., “Are Acute Post–Resistance Exercise Increases in Testosterone, Growth Hormone, and IGF-1 Necessary to Stimulate Skeletal Muscle Anabolism and Hypertrophy?,” Medicine & Science in Sports & Exercise 45, no. 11 (November 2013): 2044–51.

  7. G. E. McCall et al., “Acute and Chronic Hormonal Responses to Resistance Training Designed to Promote Muscle Hypertrophy,” Canadian Journal of Applied Physiology = Revue Canadienne de Physiologie Appliquee 24, no. 1 (February 1999): 96–107.

REFERENCES

8. Monica J. Hubal et al., “Variability in Muscle Size and Strength Gain after Unilateral Resistance Training.,” Medicine and Science in Sports and Exercise 37, no. 6 (June 2005): 964–72.

9. Jozo Grgic et al., “The Effects of Time of Day-Specific Resistance Training on Adaptations in Skeletal Muscle Hypertrophy and Muscle Strength: A Systematic Review and Meta-Analysis,” Chronobiology International 36, no. 4 (April 2019): 449–60.

10.  Nicholas A. Ratamess et al., “The Effect of Rest Interval Length on Metabolic Responses to the Bench Press Exercise.,” European Journal of Applied Physiology 100, no. 1 (May 2007): 1–17.

11.  Sumiaki Maeo et al., “Neuromuscular Adaptations Following 12-Week Maximal Voluntary Co-Contraction Training,” European Journal of Applied Physiology 114, no. 4 (April 1, 2014): 663–73.

12.  Brad J. Schoenfeld et al., “To Flex or Rest: Does Adding No-Load Isometric Actions to the Inter-Set Rest Period in Resistance Training Enhance Muscular Adaptations? A Randomized-Controlled Trial,” Frontiers in Physiology 10 (2020): 1571.

13.  Brendan L. Pinto and Stuart M. McGill, “Voluntary Muscle Relaxation Can Mitigate Fatigue and Improve Countermovement Jump Performance,” Journal of Strength and Conditioning Research 34, no. 6 (June 2020): 1525–29.