Postexercise cooling impairs muscle protein synthesis rates in recreational athletes.
Level 2 - randomized trial
Individual controlled within-subject (contralateral limb) trial in humans
PubMed 31788800 · doi:10.1113/JP278996
What was done
Twelve healthy young males (age 21 ± 2 years) completed a single resistance-type exercise session followed by 20 minutes of leg water immersion, with one leg placed in cold water (8°C; CWI) and the other in thermoneutral water (30°C; CON). Participants then consumed 20 g of intrinsically labeled (l-[1-13C]-phenylalanine and l-[1-13C]-leucine) milk protein with 45 g carbohydrates. Primed continuous infusions of l-[ring-2H5]-phenylalanine and l-[1-13C]-leucine with serial blood and muscle biopsy sampling were used to measure acute postprandial myofibrillar protein synthesis (MPS) rates and dietary amino acid incorporation over a 5-hour recovery period. In addition, deuterated water (2H2O) dosing with saliva, blood, and biopsy collections was used to measure daily MPS rates across 2 weeks of resistance training.
What was found
Incorporation of dietary protein-derived l-[1-13C]-phenylalanine into myofibrillar protein was significantly lower in the CWI leg compared to CON (0.016 ± 0.006 vs. 0.021 ± 0.007 MPE; P = 0.016). Acute postexercise MPS rates were significantly lower in CWI versus CON assessed by l-[1-13C]-leucine (0.058 ± 0.011 vs. 0.072 ± 0.017 %·h⁻¹; P = 0.024) and l-[ring-2H5]-phenylalanine (0.042 ± 0.009 vs. 0.053 ± 0.013 %·h⁻¹; P = 0.025). Prolonged daily MPS rates over 2 weeks of training were also significantly lower in CWI compared to CON (1.48 ± 0.17 vs. 1.67 ± 0.36 %·day⁻¹; P = 0.042).
Why it matters
Postexercise cold-water immersion attenuates the incorporation of dietary amino acids into muscle and blunts both acute and cumulative myofibrillar protein synthesis. Athletes and individuals aiming to maximize muscle hypertrophy or conditioning should avoid routine cold-water immersion immediately following resistance training.
Limits
The sample size was small (n = 12) and restricted exclusively to young recreational male athletes, limiting generalizability to females, older populations, or elite competitors. The study assessed fractional synthetic rates over 2 weeks rather than direct long-term morphological or functional outcomes such as muscle cross-sectional area, strength gains, or athletic performance.
Cited by
- supports Cold exposure can blunt adaptations to exercise.