In young men, doing short, very fast runs three times a week for six weeks makes the body release much less growth hormone during those runs—less than half of what it used to. At the same time, they actually get a little bit faster at running.
See the scientific wording
In young men, six weeks of sprint training performed three times per week significantly reduces the growth hormone (hGH) response to a bout of sprint exercise, with the peak post-exercise hGH concentration decreasing by over 40% and the total (integrated) hGH response decreasing by 55%, despite an improvement in sprint performance of 5–6% over the same period.
Strong evidence
Randomized trialsOne moderate-quality study supports this claim, so treat this as an early signal rather than settled science.
What the research says
1 study reviewedSupporting (1)
Effect of 6 weeks of sprint training on growth hormone responses to sprinting
Randomized Controlled TrialHuman2004
The study showed that after doing short, all-out cycling sprints three times a week for six weeks, the body's growth hormone response after sprinting was much lower (over 40% less peak and 55% less overall), even though the sprinters got faster.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
When you sprint fast, your muscles make a chemical called ammonia. The ammonia tells your brain to release growth hormone. If you train by sprinting three times a week for six weeks, your muscles get better at clearing ammonia, so there is less ammonia after a sprint. With less ammonia, your brain releases less growth hormone after sprints.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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In young men, doing short, very fast runs three times a week for six weeks makes the body release much less growth hormone during those runs—less than half of what it used to. At the same time, they actually get a little bit faster at running.
Mechanism
1 studySprinting makes your muscles produce a waste product called ammonia, which signals your body to release growth hormone. After six weeks of sprint training, your muscles handle ammonia better, so there is less of it after a sprint. With less ammonia, your body doesn't release as much growth hormone, but your sprinting improves.
When you sprint fast, your muscles make a chemical called ammonia. The ammonia tells your brain to release growth hormone. If you train by sprinting three times a week for six weeks, your muscles get better at clearing ammonia, so there is less ammonia after a sprint. With less ammonia, your brain releases less growth hormone after sprints.
Sprint exercise increases muscle metabolic activity, producing ammonia and other byproducts that accumulate in the blood.
Elevated blood ammonia stimulates the pituitary gland to release growth hormone.
Regular sprint training induces adaptations in muscles that enhance ammonia clearance or reduce ammonia production, leading to lower blood ammonia levels during and after a sprint.
With lower blood ammonia during a sprint, the stimulus for growth hormone release is reduced, resulting in a blunted growth hormone response.
Evidence from Studies
Supporting (1)
Community contributions welcome
Effect of 6 weeks of sprint training on growth hormone responses to sprinting
The study showed that after doing short, all-out cycling sprints three times a week for six weeks, the body's growth hormone response after sprinting was much lower (over 40% less peak and 55% less overall), even though the sprinters got faster.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review of Sprint Training Effects on hGH Response in Young Men
A systematic review and meta-analysis of randomized controlled trials examining the effect of sprint training on growth hormone response to sprint exercise in healthy young men, with pooled analysis of peak and integrated hGH changes.
Randomized Controlled Trial of Six-Week Sprint Training on GH Response in Young Men
A parallel-group RCT comparing young men (ages 18-30) randomized to six weeks of sprint training (3x/week) or a control group (no training). Both groups undergo a standardized sprint test with blood sampling for peak and integrated hGH before and after the intervention.
Prospective Cohort Study of Sprint Training and GH Response in Young Male Athletes
A prospective cohort study following young male athletes over six weeks, comparing a group that incorporates sprint training into their routine with a group that does not, measuring hGH response to a standardized sprint test at baseline and follow-up.
Case Report: Blunted hGH Response After Six-Week Sprint Training
A detailed case report on a single young man who undergoes six weeks of sprint training, with precise measurements of peak and integrated hGH responses to sprint exercise before and after training, including performance metrics.