Background

High-Intensity Interval Training (HIIT) imposes unique physiological demands: rapid metabolic fluctuations, mechanical stress, elevated muscle damage markers (CK, TNF-α), and maximal Type II fiber recruitment. Recovery requires both contractile protein synthesis (mTOR-dependent) and satellite cell-mediated repair. Current peptide research evaluates these pathways in isolation.

Key Findings from Literature Synthesis

Collagen Peptides (Hydroxyprolyl-glycine / Hyp-Gly):

• 15g post-exercise significantly upregulates the PI3K/Akt/mTOR signaling pathway vs. placebo in human trials (Oertzen-Hagemann et al., 2022)
• 12-week concurrent training protocols show no adverse effects
• WADA-compliant dietary supplement

Pea Oligopeptides:

• Elevate circulating IGF-1 and p-AMPK expression in preclinical models
• Downregulate myostatin (a potent muscle growth inhibitor)
• Promote Type II (fast-twitch) fiber growth — the primary fibers recruited during HIIT (Li et al., 2022)

Whey Protein Hydrolysate:

• Attenuates CK and TNF-α within 48h post-exercise in human trials
• Accelerates force recovery

Humanin (Mitochondrial-Derived Peptide):

• Significantly elevated in plasma and muscle following HIIT (Woodhead et al., 2020)
• Cytoprotective "mitokine" coordinating metabolic stress response
• Exogenous dosing not yet standardized

The Hypothesis

In recreationally trained adults performing 8 weeks of HIIT, co-supplementation with collagen peptides (15g) + pea oligopeptides (20g) post-exercise will produce significantly greater gains in lean muscle mass, Type II fiber cross-sectional area, and satellite cell accretion compared to either peptide alone or placebo.

Rationale: Collagen peptides activate mTOR-dependent protein synthesis while pea peptides independently enhance IGF-1 signaling and satellite cell proliferation. HIIT uniquely demands both pathways simultaneously, yet no studies have combined these complementary mechanisms.

Proposed Experimental Design

• n=80 recreationally trained adults (18-40y, VO₂max 40-55 mL/kg/min)
• 4 groups: collagen only (15g), pea only (20g), combination (15g + 20g), isocaloric placebo
• Protocol: 4×4min at 90-95% HRmax, 3x/week, 8 weeks
• Primary endpoints: DEXA lean mass, vastus lateralis Type II fiber CSA (biopsy)
• Secondary endpoints: Pax7⁺ satellite cell density, serum IGF-1, myostatin, p-mTOR^Ser2448
• Statistics: Mixed-effects ANOVA with group×time interaction (n=20/group, α=0.05, β=0.20, d=0.6)

Key Gap

Existing research exclusively examines single-peptide interventions in resistance training contexts. The dual requirement for myofibrillar synthesis AND stem cell-mediated repair during HIIT recovery is unexplored with combination strategies.

References

• Woodhead et al. (2020). High-intensity interval exercise increases humanin. PeerJ.
• Oertzen-Hagemann et al. (2022). Supplementation of Specific Collagen Peptides Following High-Load Resistance Exercise. Frontiers in Physiology.
• Li et al. (2022). Pea Peptide Supplementation in Conjunction With Resistance Exercise Training. PMC.

Research conducted via BIOS Deep Research platform.