Consecutive, Long-Duration Hyperoxic Immersions Effect on Skeletal Muscle Performance in Well Trained, Male Divers

Abstract

PURPOSE: The primary objective of this study was to investigate how resting, long-duration hyperoxic water immersions (WI)s at 1.35 atmospheres absolute (ATA) effected neuromuscular strength performance. We hypothesized that following five consecutive days of hyperoxic WIs, neuromuscular strength performance would be diminished post-WI and remain reduced longer than 72-hrs post-WI. METHODS: Thirteen (n=13), active male divers [31.3 ± 1.7 (24-43) yrs., mean ± SEM] completed five consecutive 6-hour resting WIs with 18-hour surface intervals while breathing 100% O2 (n=13) at 1.35 ATA. Skeletal muscle performance assessments occurred immediately before and after each WI, and 24 and 72 hours after the final WI. Performance assessments included maximum voluntary isometric contraction (MVIC) and maximal isokinetic (IK) knee extensions and elbow flexions, and maximum handgrip strength (MHG). We measured neuromuscular activation of the quadriceps, biceps brachii, and brachioradialis via surface electromyography (sEMG). RESULTS: MHG declined by 7.8% (p<0.001) by WI 5 with performance returning to baseline by 24-hr post-WI. Brachioradialis neuromuscular activation increased by 42% (p<0.001) on WI 5. MVIC knee extension performance dropped by 4% (p=0.001) on WI 3 with an 11% overall decrease in quadriceps neuromuscular activation. Maximal IK knee extension dropped by 3.3% (p=0.008) on WI 5 with 9.3% (p=0.014) drop in overall quadriceps activation dropped by 7% (p=0.013) during the same period. MVIC elbow flexion performance declined by 5.1% (p<0.001) with an 18% decline in neuromuscular activation by WI 5 but returned to baseline by 72-hr post-WI. Maximal IK elbow flexion performance dropped by 8.6% (p<0.001) on WI 5 with a continual decline in biceps brachii neuromuscular activation by 24% (p<0.001) on WI 5. CONCLUSION: The decreases in neuromuscular activation and strength performance coinciding with the non-load bearing muscles affected more than the load-bearing muscles. Yet, the brachioradialis had increases in neuromuscular activation with decreases in performance. These types of hyperoxic WIs caused significant changes to neuromuscular performance after three days of WI with recovery varying with each measured variable with some decrements lasting until the 72-hr post-WI recovery period.