Post-Exercise Cooling Lowers Skeletal Muscle Microvascular Perfusion and Blunts Amino Acid Incorporation into Muscle Tissue in Active Young Adults.

Abstract

PURPOSE Cold-water immersion lowers muscle protein synthesis rates during post-exercise recovery. Whether this effect can be explained by lower muscle microvascular perfusion and a subsequent decline in post-prandial amino acid incorporation into muscle tissue following cooling is currently unknown. METHODS Twelve young males (24 ± 4 y) performed a single resistance exercise session followed by water immersion for 20 min with one leg immersed in cold water (8 °C: COLD) and the contralateral leg in thermoneutral water (30 °C: CON). After immersion, a beverage was ingested containing 20 g free amino acids, 0.25 g L-[ring-13C6]-phenylalanine, and 45 g carbohydrates. Microvascular perfusion of the vastus lateralis muscle was assessed for both legs using contrast-enhanced ultrasound at rest, immediately following exercise and water immersion, and at t = 60 and t = 180 min following beverage ingestion. A muscle biopsy sample (vastus lateralis) was collected from both legs (t = 240 min) to determine amino acid tracer incorporation. RESULTS Microvascular blood volume was significantly lower in the COLD vs CON leg immediately following water immersion (1.24 ± 0.82 vs 3.13 ± 1.64 video intensity, respectively, P < 0.001) and remained lower at t = 60 and t = 180 min following beverage ingestion (0.90 ± 0.84 vs 1.53 ± 0.98, and 2.10 ± 2.53 vs 2.77 ± 2.81 video intensity, respectively, both P < 0.05). Exogenous amino acid incorporation into muscle protein was lower in the COLD vs CON leg (0.011 ± 0.004 vs 0.016 ± 0.005 mole percent excess, respectively, P < 0.001). The difference in post-prandial amino acid incorporation into muscle protein between the COLD and CON leg was strongly associated with the difference in microvascular blood volume between the two legs during recovery (r = 0.65, P < 0.05). CONCLUSIONS Cold-water immersion during post-exercise recovery greatly reduces muscle microvascular perfusion and blunts post-prandial amino acid incorporation in muscle.