Diving pattern of Tsushima male breath-hold divers (Katsugi).

The present study was undertaken to investigate the diving pattern, buoyancy-mass relationship, and some respiratory functions in professional male breath-hold divers in Tsushima Island, Japan. These divers always wear neoprene wet suits and use fins and 4-kg counterweights. They usually dive to 3-10 m depths. The rate of descent was 1.12 m/s for deeper dives (greater than 10 m), which is nearly twofold greater than that of Korean female divers also wearing wet suits and fins. However, the rate of ascent (0.8 m/s) was comparable to that of Korean women divers. On a typical summer day, they spend nearly 4 h in the water and perform 175 dives. The average dive and surface time were 39 and 42 s, respectively. The total bottom time was estimated to be 67 min/d, nearly twice that of Korean women divers. These divers do not adjust the counterweight and all are using a 4-kg weight. Nevertheless, the buoyancy-mass relationship revealed that they maintain the same degree of positive buoyancy (approximately 10% above the neutral level) at surface as do Korean women divers who adjust counterweights. The vital capacity was significantly greater in the diver than in the control (P less than 0.05), which was largely due to the greater expiratory reserve volume in the diver. The end-tidal O2 and CO2 pressures of the diver resting in air were not different from those of the control. These results indicate that, while the basic diving pattern is similar in both male and female breath-hold divers, the overall efficiency of diving (in terms of the rate of descent and the bottom time) appears to be superior in male divers.