To investigate whether low FiO2 affects muscle oxygenation and the rate of decline in peak torque (DR) during isokinetic knee extension, subjects performed 50 isokinetic knee extensions at 180°/s and at 0.5 Hz while inhaling low O2 gas (12%O2; H) or air (N). Muscle oxygenation kinetics was assessed by near-infrared spectroscopy, and wholebody V̇O2 and HR were measured. We calculated total-, oxy- and deoxy-hemoglobin/myoglobin concentrations (TotalHb/Mb, OxyHb/Mb, DeoxyHb/Mb), and the slopes of the change in OxyHb/Mb during exercise. SpO2 decreased in H while DR and V̇O2 did not differ between the conditions. During exercise, OxyHb/Mb was lower in H than in N, and DeoxyHb/Mb was higher in H than in N. TotalHb/Mb began to increase from the resting level earlier in H. HR was higher during the latter half of the exercise in H. The slopes of the change in OxyHb/Mb were the same in the two conditions. Our results show that low FiO2 decreases SpO2 and muscle oxygenation during maximal isokinetic knee extension. However, low SpO 2 and muscle oxygenation did not affect the rates of decline of peak torque. These results suggest that the decline in peak torque occurs for reasons other than O2 availability.
- Isokinetic knee extension
- Near-infrared spectroscopy
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation