IGF-1 (Insulin-like Growth Factor 1)
Growth Factor Anabolism Recovery
IGF-1 is a peptide hormone/growth factor. It mediates part of the effects of growth hormone, and—together with protein and insulin—supports muscle protein synthesis (MPS), recovery and nutrient partitioning. Effects emerge systemically across training, energy availability, sleep and stress management—not in isolation.
Definition and System Context
Briefly Explained IGF-1 influences muscular and connective tissue adaptations, supports glycogen replenishment and works with amino acids in MPS. Progress remains system-driven: train within MEV and MRV, guided by RIR and RPE, with adequate energy and consistent sleep.
- Signal, not a shortcut: IGF-1 is one piece—growth is still driven by training and protein.
- Axis context: Consider alongside growth hormone and insulin; counter-regulation includes cortisol.
- Hardgainer angle: High NEAT plus low intake slows progress—regardless of any “IGF-1 boost”.
Measurement and Application
Single IGF-1 readings explain little by themselves. For athletes, trends in performance, recovery, bodyweight, sleep and daily activity matter most. Context beats snapshots.
- Training & glycogen: Adequate carbohydrates support session quality and SRA-aligned progression (SRA).
- Protein synergy: Sufficient protein per meal; hit the leucine threshold; keep MPB in check.
- Track trends: Weekly averages for weight, NEAT, sleep duration/quality and performance.
Guidelines for Growth (Guardrails)
- Energy availability: Define a lean surplus; fine-tune via Rate of Gain.
- Carb placement: Pre/post training for performance/recovery—daily totals matter more than any single “magic source”.
- Protein distribution: 3–5 meals with adequate protein; consider TEF.
- Sleep & stress: Consistent sleep (Myth #6) and solid stress management (cortisol) improve systemic response.
Practice – 14-Day Orientation
- Day 0: Determine BMR/TDEE, set your protein target, define training blocks and a consistent sleep window.
- Daily: Track morning weight, steps (NEAT), training intensity (RIR) and sleep (duration/quality). Use weekly averages.
- Pre/Post: Carb-focused meals around training to refill glycogen; distribute protein to sustain MPS.
- Day 14: If Rate of Gain is flat or fatigue rises: recalibrate volume, TDEE, surplus and NEAT together.
Common Misconceptions
- “More IGF-1 = automatically more muscle.” Within normal ranges, training, energy and protein dominate outcomes. See Myth #4 and Hypertrophy.
- “You must use high-GI post workout.” Timing can help, but daily totals and context matter more. See Myth #3 and SRA.
- “Sleep is secondary.” Sleep governs recovery, GH/IGF-1 axis and training quality. See Myth #6.
“Five to six hours of sleep are enough for muscle growth”
Too narrow: sleep stabilizes recovery, GH/IGF-1 axis and daytime energy, strongly affecting training quality and appetite regulation. Detailed in Myth #6.
Studies and Evidence (PubMed)
If you want to dive deeper into IGF-1 and muscle hypertrophy, here is a small selection of studies on PubMed:
- Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms – J Clin Invest, 1995
- Viral mediated expression of insulin-like growth factor I blocks the aging-related loss of skeletal muscle function – PNAS, 1998
Note: These papers are primarily written for professionals and do not replace medical advice.