Hot-water immersion does not increase post-prandial muscle protein synthesis rates during recovery from resistance-type exercise in healthy, young males.

PURPOSE: To assess the impact of post-exercise hot-water immersion on post-prandial myofibrillar protein synthesis rates during recovery from a single bout of resistance-type exercise in healthy, young males. METHODS: Twelve healthy, male adults (age: 23+/-1 y) performed a single bout of resistance-type exercise followed by 20 min of water immersion of both legs. One leg was immersed in hot water (46 degrees C: HWI) while the other leg was immersed in thermoneutral water (30 degrees C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-(13)C]-phenylalanine and L-[1-(13)C]-leucine labelled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[ring-(2)H5]-phenylalanine and L-[1-(13)C]-leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5 h recovery period. RESULTS: Muscle temperature immediately after water immersion was higher in the HWI compared to the CON leg (37.5+/-0.1 vs 35.2+/-0.2 degrees C; P<0.001). Incorporation of dietary protein-derived L-[1-(13)C]-phenylalanine into myofibrillar protein did not differ between the HWI and CON leg during the 5h recovery period (0.025+/-0.003 vs 0.024+/-0.002 MPE; P=0.953). Post-exercise myofibrillar protein synthesis rates did not differ between the HWI and CON leg based upon L-[1-(13)C]-leucine (0.050+/-0.005 vs 0.049+/-0.002%.h(-1); P=0.815) and L-[ring-(2)H5]-phenylalanine (0.048+/-0.002 vs 0.047+/-0.003%.h(-1); P=0.877), respectively. CONCLUSIONS: Hot-water immersion during recovery from resistance-type exercise does not increase the post-prandial rise in myofibrillar protein synthesis rates. In addition, post-exercise hot-water immersion does not increase the capacity of the muscle to incorporate dietary protein-derived amino acids in muscle tissue protein during subsequent recovery.