The influence of acute hypoxic exposure on isokinetic muscle force production.

To investigated whether an acute hypoxic stimulus affects muscle strength development assessed by isokinetic dynamometry during maximal knee extension. A total of 15 healthy young men participated in this study (61.9 ± 6.1 kg; 1.72 ± 0.08 m; 20.9 ± 2.6 years). We evaluated knee extension and flexion isokinetic dynamometer performance in normoxic and hypoxic conditions. The analyzed parameters, for concentric contraction, were peak torque and total work measured at 1.05 and 5.23 rad/s; and fatigue index measured at 5.23 rad/s. During isokinetic testing, heart rate and oxygen saturation (SpO2) were monitored. Hypoxic conditions (3,600 m) were simulated, via a mixing chamber, with the dilution being constantly controlled by a PO2 probe. Test reproducibility results (test-retest) for all isokinetic knee parameters were classified as moderate to almost perfect (ICC = 0.694 to 0.932). SpO2 was 88.4 ± 3.4% in the hypoxic condition and 97.1 ± 0.7% in the normoxic condition (p = 0.000, effect size = 0.87). Heart rate was not significantly different between normoxic and hypoxic conditions at the end of the test. There were no significant differences in isokinetic variables evaluated for the extensor and flexor muscles at concentric contraction between the normoxic and hypoxic conditions. Our findings indicate that reduced arterial oxygenation per se has no effect on the muscular isokinetic strength of the knee extensors.