Preliminary results of VO2max and arterial O2 saturation at sea level versus 610m

Gore, C.J., Hahn, A.G., Campbell, D.P., Bellenger, S., Lawton, E., Watson, D.B., Emonson, D. L. Wood, R.J., Scroop, G.S., Norton, K.I., Ly, S. 'Preliminary results of VO2max and arterial O2 saturation at sea level versus 610m', Proceedings of the National Annual Scientific Conference in Sports Medicine, 1994.

Athletes completing VO2max tests at Canberra have commented for several years that the scores they achieve are consistently lower than those obtained in their home states which are located at sea level. It is possible that the mild altitude of Canberra (610m) may adversely effect the performance of elite endurance athletes. One mechanism which might contribute to lower scores is arterial oxygen desaturation which has been observed at sea level for over 10 years (Dempsey et at, 1984; Powers and Williams, 1987) in elite athletes with VOmax exceeding approximately 4.5 l.min-1. Desaturation might therefore be further limiting at mild altitude in highly trained athletes. However this hypothesis is not consistent with the text books which suggest that performance is not compromised until an altitude of approximately 1500 – 2000m. The aim of this study was to measure VO2 at sea level compared with 610 m and to investigate the mechanisms which might contribute to any observed differences.

Twenty men were studied in a double-blind, counterbalanced study of cycle ergometer VO2max tests conducted in a hypobaric chamber at RAAF Base Williams. The chamber was 6.1 m long by 2.4 m in diameter and had a refresh rate of 2,265 l.min-1. Each subject completed 2 tests within 24-48 hours. Conditions in the chamber were selected to approximate the lowest barometric pressure that might be encountered at sea level (745 mmHg) and at Canberra 695 mmHg).

The results of this study indicate that VO2max of elite cyclists was significantly reduced at 610 m compared with sea level and this may be partially due to increased arterial oxygen desaturation. Athletes attempting to qualify for national team selection at 610 m altitude may presently be at a serious disadvantage and all aerobic performance tests, for comparative or selection purposes need to be conducted at a standard barometric pressure.

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