Abstract
PurposeThe aim of the study was to provide an evaluation of the oxygen transport, exchange and storage capacity of elite breath-hold divers (EBHD) compared with non-divers (ND).MethodsTwenty-one healthy males’ (11 EBHD; 10 ND) resting splenic volumes were assessed by ultrasound and venous blood drawn for full blood count analysis. Percutaneous skeletal muscle biopsies were obtained from the m. vastus lateralis to measure capillarisation, and fibre type-specific localisation and distribution of myoglobin and mitochondrial content using quantitative immunofluorescence microscopy.ResultsSplenic volume was not different between groups. Reticulocytes, red blood cells and haemoglobin concentrations were higher (+ 24%, p < 0.05; + 9%, p < 0.05; + 3%, p < 0.05; respectively) and mean cell volume was lower (− 6.5%, p < 0.05) in the EBHD compared with ND. Haematocrit was not different between groups. Capillary density was greater (+ 19%; p < 0.05) in the EBHD. The diffusion distance (R95) was lower in type I versus type II fibres for both groups (EBHD, p < 0.01; ND, p < 0.001), with a lower R95 for type I fibres in the EBHD versus ND (− 13%, p < 0.05). Myoglobin content was higher in type I than type II fibres in EBHD (+ 27%; p < 0.01) and higher in the type I fibres of EBHD than ND (+ 27%; p < 0.05). No fibre type differences in myoglobin content were observed in ND. Mitochondrial content was higher in type I than type II fibres in EBHD (+ 35%; p < 0.05), with no fibre type differences in ND or between groups.ConclusionsIn conclusion, EBDH demonstrate enhanced oxygen storage in both blood and skeletal muscle and a more efficient oxygen exchange capacity between blood and skeletal muscle versus ND.
Highlights
Breath-hold diving is a competitive sport where maximal breath-hold time, or depth and distance swum underwater with a single breath is judged
The primary findings were that elite breath-hold divers (EBHD); (1) combined a splenic volume that was not different to ND with a greater red blood cell and haemoglobin concentration; (2) had a greater capillarity and improved R95 of skeletal muscle which supplied; (3) a greater type I fibre myoglobin content and a mitochondrial content that was not different to ND
These findings confirm our hypothesis that EBHD have a greater oxygen reserve and a more efficient oxygen exchange capacity between blood and skeletal muscle and that this may, at least in part, contribute to the greater breath-holding capacities reported in this population
Summary
Breath-hold diving is a competitive sport where maximal breath-hold time, or depth and distance swum underwater with a single breath is judged. Bae et al (2003) demonstrated that female Ama breath-hold divers have a higher skeletal muscle capillary density, a lower oxygen diffusion distance and a smaller muscle fibre cross-sectional area compared with a matched non-diving (ND) group. EBHD have less frequent daily apnoeic activities (< 30 repetitions) than the Ama breath-hold divers, but perform repetitively longer apnoeas (> ~ 120 s) and attain deeper dives (> ~ 30 m) in temperatures ranging between 10 °C–28 °C. Whether these fundamental differences may stimulate skeletal muscle angiogenesis in EBHD skeletal muscles remains to be determined
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