Evaluation of Fitness Level by the Oxygen Uptake Efficiency Slope After a Short-Term Intermittent Endurance Training

Abstract

Several indicators are used as indices of cardiorespiratory reserve. Among them, oxygen uptake (V·O₂) at peak and ventilatory threshold (VAT) levels are the most common used. In the present study, endurance training was used to evaluate and compare the usefulness of a new index, the Oxygen Uptake Efficiency Slope (OUES) as an alternative to the previous ones. Fifteen physical education student women participated in the study (8 as a trained group [T: age (mean ± SD) 21.9 ± 3.3 y, height 165.1 ± 5.5 cm, weight 60.4 ± 3.3 kg] and 7 as a control group [C: age 21.7 ± 1.9 y, height 165.4 ± 7.2 cm, weight 59.6 ± 8.6 kg]). Before and after 6 weeks of the Square-Wave Endurance Exercise Test (SWEET) training program or daily activities, they performed an incremental test (30 W/3 min) on a cycle ergometer to determined V·O₂, power output and parameters associated with breathing efficiency (the respiratory equivalents, and the ventilatory dead space to tidal volume ratio [Vd/Vt]) at peak- and VAT-levels. The slope of the relationship between ventilation and carbon dioxide production was also calculated. OUES, derived from the logarithmic relationship between V·O₂ and minute ventilation (V·_E), was determined at 75 % (OUES75), 90 % (OUES90) and 100 % (OUES100) of exercise duration. After endurance training in T, V·O₂ and power output were significantly improved at peak- and VAT-levels while all breathing efficiency indices remained unchanged. No changes were observed in C after 6 weeks. Despite significant correlation between OUES values and V·O₂ at peak- and VAT-levels, OUES75, OUES90 and OUES100 did not significantly change after endurance training. While V·O₂ and power output at peak- and VAT-levels increased in all T, training-induced changes in OUES appeared more variable. We concluded that OUES was not sufficiently sensitive to highlight improvement of cardiorespiratory reserve after endurance training whereas V·O₂ at peak and VAT levels did.

Key words

SWEET training - peak oxygen uptake - ventilatory anaerobic threshold - healthy subject - cycle ergometer

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