ABSTRACT
The purpose of this study was to investigate the effect of constant endurance cycling exercise below Ventilatory Threshold (VT), under different pedal rate/torque regulations (PTR), on muscle oxygenation, as well as cardio-respiratory function and energy metabolism. Eight healthy male adults participated in the study for three tests. The first test was to examine the maximum oxygen uptake (VO<sub>2</sub>max) using a ramp loading measurement of 60 rpm, 20 watt/min ; and an individual 80%VT load was obtained. The second and third tests (random) were to measure heart rate (HR), blood pressure (MAP), expired gas and NIRS data before, during and after 30 min 80%VT constant cycling exercise with low pedal rate/high torque (LPHT : 32 rpm, 23.3±6.0Nm) or high pedal rate/low torque (HPLT : 79rpm, 9.4±2.4Nm). As a result, HPLT showed higher values in HR (p<0.001), MAP (p<0.001), VO<sub>2</sub> (p<0.001), VCO<sub>2</sub> (p<0.001) and RER (p<0.05), than LPHT ; but LPHT showed a higher fat consumption rate than HPLT (p<0.05). Significant PTR effect were recognized for the parameters of the tissue hemoglobin index (THI) (p<0.001) and oxygenation hemoglobin (ΔO<sub>2</sub>Hb) (p<0.01) ; and both indicated higher values for HPLT than LPHT ; but LPHT showed insignificantly (p=0.066) higher de-oxygenation hemoglobin (ΔHHb) than HPLT. Moreover, the significant time effects of THI and ΔO<sub>2</sub>Hb were also recognized. In conclusion, this study indicated that during constant cycling exercise below VT, HPLT might result in greater muscle blood volume, higher muscle oxygenation concentration and higher HR and VO<sub>2</sub> compared with LPHT. These results suggest that, HPLT might be effective in alleviating the working load on lower limbs, as well as promoting muscle oxygenation, cardiorespiratory function (systemic oxygen supply) and energy metabolism. Therefore, HPLT constant cycling exercise below VT could be used in a rehabilitation program as a beneficial exercise for elderly people with decreasing muscle strength in their lower limbs.