Abstract
Purpose: This study examined the effects of repeated long-duration water immersions (WI)s at 1.35 atmospheres absolute (ATA) on neuromuscular endurance performance. We hypothesized that, following 5 days of consecutive, resting, long-duration WIs, neuromuscular endurance performance would decrease.Methods: Fifteen well-trained, male subjects completed five consecutive 6-h resting WIs with 18-h surface intervals during the dive week while breathing compressed air at 1.35 ATA. Skeletal muscle endurance performance was assessed before and after each WI, and 24 and 72 h after the final WI. Muscular endurance assessments included 40% maximum handgrip endurance (MHE) and 50-repetition maximal isokinetic knee extensions. Near infrared spectroscopy was used to measure muscle oxidative capacity of the vastus lateralis and localized muscle tissue oxygenation of the vastus lateralis and flexor carpi radialis. Simultaneously, brachioradialis neuromuscular activation was measured by surface electromyography.Results: A 24.9% increase (p = 0.04) in the muscle oxidative capacity rate constant (k) occurred on WI 4 compared to baseline. No changes occurred in 40% MHE time to exhaustion or rate of fatigue or total work performed for the 50-repetition maximal isokinetic knee extension. The first quartile of deoxygenated hemoglobin concentration showed a 6 and 35% increase on WIs 3 and 5 (p = 0.026) with second quartile increases of 9 and 32% on WIs 3 and 5 (p = 0.049) during the 40% MHE testing when compared to WI 1.Conclusion: Our specific WI protocol resulted in no change to muscular endurance and oxygen kinetics in load bearing and non-load bearing muscles.
Highlights
Water immersion, complete submersion of the body in water, alters physiological function during and after water egress (Florian et al, 2013a,b, 2014; Myers et al, 2017)
No main effects were observed in total Deoxygenated hemoglobin (HHb) or with all tissue saturation index (TSI) metrics as shown in Table 3 as compared to water immersion (WI) 1
One aspect is for certain, the data from this study suggest five consecutive long-duration WIs may not be enough exposure time in a microgravity environment to cause a decrease to forearm flexor endurance performance
Summary
Complete submersion of the body in water, alters physiological function during and after water egress (Florian et al, 2013a,b, 2014; Myers et al, 2017). Human models that used 7-day dry immersion methodology, such as Koryak (1999, 2002), demonstrated decrements in action potential duration by 18.8%, and amplitude by 14.6%, during skeletal muscle maximal voluntary contractions. These changes were accompanied by a 33% reduction in maximal voluntary contraction force and a 2.8% decrease in surface area. De Boer et al (2008), showed an 8% decrease in VL thickness and no change to biceps brachii thickness after 5 weeks of bed rest These analog studies simulate the changes in neuromuscular strength seen in long-term exposure to microgravity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
