Energy Balance and Muscular Power Alterations Following Repeated 4Hour Exercise Dives
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Divers often perform repeated dives with taxing activity using various underwater breathing apparatuses (UBA), which may increase total energy expenditure (TEE) and alter energy balance (EB) and physical ability. However, data is lacking regarding metabolic and muscular responses to repeated diving. We tested the hypotheses that repeated diving induces negative EB and decreases muscular force, but these decrements would not be affected by UBA. 16 military divers participated in 3 4hr dives (31 2 C) at 1.3 ata, with 20hr surface intervals, while wearing a MK25 (n=8, age: 33.8 4.4 yr) UBA with 100% oxygen or MK20 (n=8, age: 36.0 4.7 yr) with air. During dives, subjects alternated 30 min rest and cycling exercise at 60% HRmax. EB was calculated as TEE energy intake (EI). TEE was measured via doubly labeled water (DLW; 48 atom % 2H2O and 812 atom % 18O). Urine samples were taken before each dive, and for 4 days after diving to assess differences in EB diving and nondiving (control) days. EI was assessed via food logs. EB, TEE, and EI were normalized to body weight. Before and after each dive, peak force (PF) and rate of power development (RPD) were measured on a force plate during 3 countermovement jumps (3J) and while hopping in place for 10 sec (Hop). EB and muscular power were analyzed with mixed model ANOVAs (UBA: MK25 vs MK20, Diving: Dive Day (DD) vs Control Day (CD), Dive: Pre vs Post Dive, Repeated Diving: Dive 1, 2, 3). There was no effect of UBA on EB during dive days (MK25: 12.8 8.9 kcal/kg; MK20: 8.4 6.2 kcal/kg); but, EB did increase during diving (p < 0.01, DD: 13.0 7.6 kcal/kg; CD: 6.7 10.4 kcal/kg). There was no effect of UBA on TEE (p = 0.16, MK25: 37.6 5.6 kcal/kg, MK20: 42.3 2.5 kcal/kg) during dive days; but, TEE (p < 0.01) increased on dive days compared to control (DD: 39.6 5.2 kcal/kg; CD: 31.2 7.0 kcal/kg). There was no effect of UBA or diving on EI. 3JRPD (p < 0.01) and HopRPD increased (p < 0.01) with repeated diving (3JRPD D1: 11.7 3.9 kW/s vs. D2: 13.0 4.0 kW/s, p > 0.05; D1 vs. D3: 13.7 3.9 kW/s, p < 0.01; D2 vs. D3, p > 0.05; HopRPD D1: 37.4 21.6 kW/s vs. D2: 46.1 29.0 kW/s, p = 0.02; D1 vs. D3: 49.9 27.1 kW/s, p < 0.01; D2 vs. D3, p > 0.05). There was a group effect for 3JPF (p = 0.02) and 3JRPD (p < 0.01) with higher PF (MK25: 1948 205 N; MK20: 1655 223 N) and RPD (MK25: 15.2 3.5 kW/s; MK20: 10.4 2.9 kW/s) in MK25, but no other effects. Repeated 4hr exercise dives induce negative EB due to higher TEE, independent of UBA. RPD increased after repeated diving; however, further research is needed to determine mechanisms.
