Post-exercise Cooling Impairs Muscle Protein Synthesis Rates In Healthy Young Males

Abstract

Protein ingestion and cooling are strategies employed by athletes to improve post-exercise recovery and, as such, to facilitate muscle reconditioning following exercise. However, whether post-exercise cooling affects postprandial protein handling and subsequent muscle protein synthesis rates during recovery from exercise has not been studied. PURPOSE: This study assessed the impact of post-exercise cooling on acute postprandial (hourly) and prolonged (daily) myofibrillar protein synthesis rates during recovery from resistance-type exercise over a 2-week period. METHODS: Twelve healthy, male adults (age: 21±1 y) performed a single session of resistance-type exercise followed by water immersion of both legs for 20 min. One leg was immersed in cold water (8°C: CWI) while the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine labelled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[ring-2H5]-phenylalanine and L-[1-13C]-leucine infusions were applied, with frequent collection of blood samples and muscle biopsies to assess myofibrillar protein synthesis rates in vivo over a 5-h recovery period. In addition, deuterated water (2H2O) was ingested with the collection of saliva, blood and muscle biopsies over 2 weeks to assess the effects of post-exercise cooling with protein intake on myofibrillar protein synthesis rates during more prolonged resistance-type exercise training. RESULTS: Incorporation of dietary protein-derived L-[1-13C]-phenylalanine into myofibrillar protein was significantly lower in CWI compared to CON (0.016±0.002 vs 0.021±0.002 MPE; P=0.016). Post-exercise myofibrillar protein synthesis rates were lower in CWI compared to CON based upon L-[1-13C]-leucine (0.058±0.003 vs 0.072±0.005%·h-1, respectively; P=0.024) and L-[ring-2H5]-phenylalanine (0.042±0.003 vs 0.053±0.004%·h-1, respectively; P=0.025). Daily myofibrillar protein synthesis rates assessed over 2 weeks were significantly lower in CWI when compared to CON (1.48±0.05 vs 1.67±0.11%·d-1, respectively; P=0.042). CONCLUSION: Cold-water immersion during recovery from resistance-type exercise impairs myofibrillar protein synthesis rates.