HGH - some studies
Here’s a breakdown of scientific studies involving growth hormone (GH) and athletics/bodybuilding, along with simplified explanations for each:
1. GH in Experienced Weight Lifters (Short-Term Study)
Published Results: In a 14-day study, experienced male weight lifters received subcutaneous GH (40 µg/kg per day). Their IGF-I levels rose notably (from ~224 to 589 ng/mL), but muscle protein synthesis didn’t increase, nor did whole-body protein breakdown decrease .
Put simply: Despite hormonal increases, short-term GH use didn’t translate into improved muscle-building metabolism in trained lifters.
2. GH & Performance in Recreational Athletes
Study: Over 8 weeks, recreational athletes received GH, testosterone (T), both, or a placebo.
Findings: GH alone reduced fat mass, increased lean mass (mostly extracellular water), and improved sprint capacity modestly—around a 3.9% boost overall, and about 8.3% when paired with testosterone in men .Simplified: GH can help reduce body fat and slightly enhance sprint performance, especially when combined with testosterone—but other performance markers remained unchanged.
3. GH Administration in Resistance-Trained Men (Biochemical Markers)
Study: Men engaged in resistance training, then were given daily GH (0.1 IU/kg) for two weeks versus placebo. Researchers measured IGF-I and collagen markers post-exercise .
Interpretation: This research explored how GH affects biochemical markers related to muscle growth and tissue remodeling—not necessarily performance or strength gains.4. GH and Energy Metabolism in Healthy Men
Design: In a two-week trial, healthy men received 6 IU/day of GH, with 24-hour metabolic measurements.
Results:24-hour energy expenditure increased by 4.4%.Fat oxidation rose by 29%.A lower respiratory quotient (indicating more fat-burning relative to carbs) was observed during fasting .
Plainly: GH can boost calorie burning and shift metabolism toward fat utilization—key for body composition—but this doesn’t necessarily mean more muscle.
5. GH & Muscle Strength in Healthy Adults
Meta‐Observation: In healthy individuals (particularly older or GH-deficient adults), GH increases lean mass and strength over time. However, in those with normal GH levels, adding GH to resistance training did not enhance strength outcomes .
In summary: GH can aid muscle growth in deficiency states, but not necessarily boost performance in healthy, training individuals.
6. Circadian Effects, Sleep, & Muscle Anabolism
Zebrafish Model: Muscle growth happens more during the day—even without activity or feeding—due to the biological clock organizing protein synthesis, while muscle breakdown increases at night .
Though not human-specific, these findings highlight how timing and the circadian rhythm can influence muscle-building processes.
While these are not scientific studies, they reflect popular theories:
“Shortly after going to sleep our growth hormone spikes causing enhanced muscle growth…”
“For fat burning it would be good to take fasted in the morning or right after your workout… Recovery in general … right before bed.”
These align with the notion that sleep-related GH release is often targeted via nighttime or pre-sleep protocols by bodybuilders.
Quick Summary Table
Study / Context
Results (Bodybuilding-Related)
Short-term GH in lifters
No impact on muscle protein synthesis or breakdown, despite IGF-I increase
8-week trial (GH ± T)
Reduced fat, modest sprint gain, lean mass increase via water retention with GH + T
GH in resistance-trained men
Changes in biomarkers (IGF-I, collagen), not strength outcomes
Metabolic effects in healthy
Boosted energy expenditure and fat oxidation, more fat-burning overall
GH in healthy vs. deficient
Improved muscle/strength in deficient individuals, but no added benefit in healthy subjects
Circadian muscle growth
Daytime favors growth, nighttime favors breakdown, independent of feeding/activity
Community insights
Emphasis on nighttime GH release and timing relevance
Bottom Line for Bodybuilders
GH is not a shortcut to muscle gains—especially for trained, GH-sufficient individuals.
It may help with fat loss and lean mass (via fluid retention), and offers slight improvements in sprint/power, particularly when combined with testosterone.Leveraging timing (e.g., nighttime dosing) can align with natural GH release, though direct benefits for muscle growth aren’t clearly proven in robust studies.Enhancing GH spikes naturally via sleep, fasting, or exercise timing might be more practical and safer than exogenous use.