Study on the limitation for detecting anaerobic threshold by respiratory frequency. Under the condition of exercise-entrained breathing is minimized / 体力科学

ABSTRACT

Under the condition that entrainment between breathing rate and exercise rhythm was minimized. The limitation for deciding anaerobic threshold (AT) by respiratory frequency (f) was studied. Ten healthy subjects (5 male and 5 female) have volunteered to take part in two incremental cycle exercises (male 30 watt/2 min, 50 rpm ; female 20 watt/2 min, 50 rpm) . The subjects were either sedentary or active and performed tests under two different condi-tions. The different conditions are explained below.<BR>1) Condition M Use a metronome to maintain pedalling frequency so entrainment would easily occur.<BR>2) Condition S Use a tachometer to maintain pedalling frequency so entrainment would not easily occur.<BR>Oxygen uptake (VO<SUB>2</SUB>) at AT were determined by two different methods. The first method was to detect the point of non-linear increase in minute ventilation (VE) and carbon dioxide output (VCO<SUB>2</SUB>) and then to increase detection in the ventilatory equivalent for O<SUB>2</SUB> (VE/VO<SUB>2</SUB>) without increasing the ventilatory equivalent for CO<SUB>2</SUB> (VE/VCO<SUB>2</SUB>) (AT-V) . The second method was to detect inflection in f by multisegment linear regression (AT-CF) . There were no significant differences between AT-V (condition M 26.0±6.2, condition S 26.4±6.0 m<I>l</I>/kg/ min) and AT-CF (condition M 31.6±10.2, condition S 24.7±10.0 m<I>l</I>/kg/min) . A significant positive correlation between AT-V and AT-CF was observed in condition S (r=0.850, p< 0.05), but not in condition M (r=0.563, p>0.05) . The error between AT-V and AT-CF had individual variations. An error within±5% was observed in only 4 out of 10 subjects. These results suggested that even though the ability to detect AT using f is superior in condition S, f is an inadequate indicator for the AT, though the exercise entrained breathing is minimized.