Energy Balance and Muscular Power Alterations Following Repeated 4‐Hour Exercise Dives

Abstract

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 4‐hr dives (31 ± 2 °C) at 1.3 ata, with 20‐hr 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; 4‐8 atom % 2H2O and 8‐12 atom % 18O). Urine samples were taken before each dive, and for 4 days after diving to assess differences in EB diving and non‐diving (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. 3J‐RPD (p < 0.01) and Hop‐RPD increased (p < 0.01) with repeated diving (3J‐RPD – 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; Hop‐RPD – 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 3J‐PF (p = 0.02) and 3J‐RPD (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 4‐hr 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.