Key Points of Why Post Workout Hormones Aren’t the Key to Muscle Growth
- Post-workout hormones have long been thought to play a significant role in building muscle, but this new research shows their impact is minimal.
- Local muscle factors, like mechanical tension and progressive overload, are the real drivers of muscle growth, not hormonal surges.
- Females achieve comparable strength and hypertrophy results as males, debunking the myth of testosterone-dependent superiority in muscle gains.
Are Acute Increases in Post Exercise Hormones such as GH and Testosterone the key to Building Muscle?
For decades, the fitness world has been built on the idea that post-workout hormones are the key to unlocking muscle growth. Trainers and gym-goers have emphasized the importance of short rest periods and specific exercises to spike testosterone and growth hormone (GH), believing this to be the secret sauce of hypertrophy. The hormone hypothesis posits that acute elevations in anabolic hormones such as testosterone, growth hormone (GH), and insulin-like growth factor 1 (IGF-1) following resistance training are directly responsible for muscle growth.1
However, a groundbreaking study by Van Every et al. (2024), published in Exercise and Sport Science Reviews, challenges this notion.2 The research reveals that these acute hormonal surges after exercise do little to promote long-term muscle growth. Instead, sustainable progress comes from focusing on training principles like progressive overload and recovery.
Adding New Insights from Research on Post Exercise Hormones
The acute rise in post workout hormones like testosterone, GH, and IGF-1 has long been thought to play a pivotal role in stimulating muscle protein synthesis and hypertrophy. However, studies show that acute hormonal spikes are not necessary for these outcomes. Muscle protein synthesis occurs when the rate of synthesis exceeds muscle breakdown, a process primarily driven by the mechanical and metabolic demands of resistance training.3 While hormones may play a role in stimulating muscle protein synthesis, they are not the sole determinants of muscle growth. For example, Motsinger et al. demonstrated that the presence of anabolic hormones alone does not guarantee increased protein synthesis rates in muscle cells, indicating that nutritional status and other factors are equally important.4
Males and Females Make Similar Gains in Muscle Mass Despite Females Having Less Testosterone
Interestingly, research involving male and female subjects demonstrated that neither acute post workout increases in anabolic hormones nor muscle anabolic signaling were linked to long-term hypertrophic adaptations.5,6 For example, West and Phillips observed no correlation between post exercise hormone levels and muscle growth, even in high-volume training scenarios.7
The disparity in testosterone levels between males and females, often highlighted as a limiting factor for females, is also not a barrier to muscle growth. Despite males producing 4–9 mg of testosterone daily (equivalent to systemic concentrations of 290–1000 ng/dL), females achieve similar relative gains in strength and muscle mass.8 This reinforces the idea that local muscle factors, not hormones, are the key drivers of hypertrophy.
Debunking Post Workout Hormones Role in Building Muscle
The review dismantled long-held beliefs about post-workout hormones and hypertrophy:
- Acute increases in post exercise hormones like testosterone, GH, and IGF-1 lasted only minutes to hours and did not correlate with muscle growth.
- Both groups experienced similar muscle size and strength increases, regardless of rest duration or post exercise hormone spikes.
- Despite significantly lower testosterone levels, females achieved comparable relative increases in strength and hypertrophy, challenging the testosterone-centric view of muscle building.
One study cited by the authors demonstrated that hypertrophy occurred exclusively in the trained limb, with no systemic hormonal changes required for muscle growth.6 Other research showed no difference in muscle protein synthesis rates between high-hormone and low-hormone exercise conditions.9
What Really Drives Muscle Growth?
The research concludes that post-workout hormones are not the primary drivers of hypertrophy. Instead, muscle growth depends on three critical local factors:
Mechanical Tension: Think of this as the “workload” placed on your muscles during exercises. This tension activates pathways like mTOR, which triggers protein synthesis.10
Progressive Overload: Gradually increasing the weight, reps, or intensity ensures your muscles continue to adapt and grow.
Hormones like testosterone and GH are more like background music—they create a supportive environment but do not directly stimulate growth. Even females with 10–20 times lower testosterone levels than males achieve equivalent relative hypertrophy when training programs are matched. 11
Practical Applications: Don’t Worry About Post-Exercise Hormones! Training Smarter, Not Harder
How can you apply these findings to your training? Here are five practical takeaways:
- Progressive overload remains the cornerstone of hypertrophy. Gradually challenge your muscles with heavier weights or more reps.
- Short rest periods may spike hormones but do not improve hypertrophy outcomes. Rest based on your recovery needs and workout intensity.
- Sustainable progress comes from sticking to a structured training program. Forget chasing fleeting hormonal surges.
- Proper nutrition, sleep, and stress management are more impactful than worrying about post-workout hormones.
- Females don’t need to adjust their workouts to align with hormonal phases or worry about testosterone levels. The playing field is level when training intensity and recovery are optimized.
Conclusion
The study by Van Every et al. provides compelling evidence that post-workout hormones are not the secret to muscle growth. Instead, hypertrophy is driven by factors like mechanical tension, progressive overload, and metabolic stress. Both men and women can achieve outstanding results without relying on hormonal peaks. You can maximize your muscle-building potential by focusing on consistent effort, proper recovery, and scientifically proven training methods.
References
1 Schöenfeld, B. J. Postexercise Hypertrophic Adaptations. The Journal of Strength and Conditioning Research 27, 1720-1730 (2013). https://doi.org/10.1519/jsc.0b013e31828ddd53
2 Van Every, D. W., D’Souza, A. C. & Phillips, S. M. Hormones, Hypertrophy, and Hype: An Evidence-Guided Primer on Endogenous Endocrine Influences on Exercise-Induced Muscle Hypertrophy. Exerc Sport Sci Rev 52, 117-125 (2024). https://doi.org/10.1249/jes.0000000000000346
3 Joanisse, S. et al. Recent advances in understanding resistance exercise training-induced skeletal muscle hypertrophy in humans. F1000Res 9 (2020). https://doi.org/10.12688/f1000research.21588.1
4 Motsinger, L. A. et al. Understanding the Effects of Trenbolone Acetate, Polyamine Precursors, and Polyamines on Proliferation, Protein Synthesis Rates, and the Abundance of Genes Involved in Myoblast Growth, Polyamine Biosynthesis, and Protein Synthesis in Murine Myoblasts. Biology 12, 446 (2023). https://doi.org/10.3390/biology12030446
5 Morton, R. W. et al. Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. J Appl Physiol (1985) 121, 129-138 (2016). https://doi.org/10.1152/japplphysiol.00154.2016
6 Wilkinson, S. B., Tarnopolsky, M. A., Grant, E. J., Correia, C. E. & Phillips, S. M. Hypertrophy with unilateral resistance exercise occurs without increases in endogenous anabolic hormone concentration. Eur J Appl Physiol 98, 546-555 (2006). https://doi.org/10.1007/s00421-006-0300-z
7 West, D. W. & Phillips, S. M. Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. Eur J Appl Physiol 112, 2693-2702 (2012). https://doi.org/10.1007/s00421-011-2246-z
References
8 Roberts, B. M., Nuckols, G. & Krieger, J. W. Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis. J Strength Cond Res 34, 1448-1460 (2020). https://doi.org/10.1519/jsc.0000000000003521
9 West, D. W. et al. Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men. J Physiol 587, 5239-5247 (2009). https://doi.org/10.1113/jphysiol.2009.177220
10 West, D. W. et al. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. J Appl Physiol (1985) 108, 60-67 (2010). https://doi.org/10.1152/japplphysiol.01147.2009
11 D’Souza, A. C. et al. Menstrual cycle hormones and oral contraceptives: a multimethod systems physiology-based review of their impact on key aspects of female physiology. J Appl Physiol (1985) 135, 1284-1299 (2023). https://doi.org/10.1152/japplphysiol.00346.2023
