TY - JOUR
T1 - Relationship between muscle oxygenation kinetics and the rate of decline in peak torque during isokinetic knee extension in acute hypoxia and normoxia
AU - Kawahara, Yoyoi
AU - Salto, Y.
AU - Kashimura, K.
AU - Muraoka, I.
PY - 2008/5/1
Y1 - 2008/5/1
N2 - 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.
AB - 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.
KW - Hypoxia
KW - Isokinetic knee extension
KW - Near-infrared spectroscopy
KW - Oxygenation
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U2 - 10.1055/s-2007-965567
DO - 10.1055/s-2007-965567
M3 - Article
C2 - 17879886
AN - SCOPUS:43949088858
VL - 29
SP - 379
EP - 383
JO - International Journal of Sports Medicine
JF - International Journal of Sports Medicine
SN - 0172-4622
IS - 5
ER -