Effect of Intensive Interval Training during Unloading on Muscle Deoxygenation Kinetics

Abstract

The present study investigated the effects of intensive interval training during 20-day of unloading on local muscle oxygenation kinetics evaluated by near infrared spectroscopy technique (NIRS). Eleven adult men completed 20-day unloading and were divided into two groups; the control (CON) group and training (TR) group. The TR group engaged in exercise training sessions that consisted of one-legged submaximal cycle exercise using the unloaded leg at 60∼80% of V˙O₂ with intermittent rest periods, 25 min/day every other day. All subjects performed isometric knee extension exercise at 50% of their maximum voluntary contraction force before and after unloading. NIRS Δ[deoxy-Hb/Mb] signal was recorded from m. vastus lateralis and was fitted to an exponential equation in order to determine the kinetics parameters. The time constant (τ) of the % Δ[deoxy-Hb/Mb] was unchanged in the TR group, while it significantly increased in the CON group after unloading (pre, 5.0±1.0; post, 7.4±1.0 s). It is concluded that 20-day unloading increased the τ, suggesting deterioration of capacity for oxidative phosphorylation and oxygen utilization in a skeletal muscle. Additionally, the preservation of τ in the TR group suggested that intensive interval training could have an impact on the maintenance of muscle oxidative metabolism during unloading.

Key words

microgravity - muscle oxidative metabolism - NIRS - countermeasure - endurance training

References

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