The Effect of Static Stretching Duration on Muscle Blood Volume and Oxygenation

Matsuo, H, Kubota, M, Shimada, S, Kitade, I, Matsumura, M, Nonoyama, T, Koie, Y, Naruse, H, Takahashi, A, Oki, H, Kokubo, Y, and Matsumine, A. The effect of static stretching duration on muscle blood volume and oxygenation. J Strength Cond Res XX(X): 000-000, 2020-Muscle blood volume increases due to stretching; however, the minimum duration of stretching to sustainably increase the muscle blood volume after stretching has not yet been elucidated. This study examined whether the duration of static stretching influenced the muscle blood volume and oxygenation. Ten healthy male subjects participated in this controlled laboratory study. Static stretching of the gastrocnemius muscle was performed for 5 durations (20 seconds, and 1, 2, 5, and 10 minutes). Changes in both the total-Hb (DeltatHb), as an index of blood volume, and tissue oxygenation index (DeltaTOI) from baseline were determined using near-infrared spectroscopy. Both the DeltatHb and DeltaTOI decreased during stretching and increased after stretching. The minimum value of DeltatHb during stretching did not differ in each of the 5 durations, but minimum DeltaTOI progressively decreased with longer durations of stretching. The peak value of DeltatHb after stretching increased with longer durations of stretching. The value of DeltatHb at 5 minutes after the end of stretching increased with more than 2 minutes of stretching compared with 20 seconds of stretching, although the value of DeltatHb did not significantly differ between the 2, 5, and 10 minutes' durations. These findings suggest that a longer duration of stretching elicits a decrease in muscle oxygenation during stretching, and an increase in both the muscle blood volume and oxygenation after stretching. The results indicated that the minimum duration of stretching to sustain an increase in the muscle blood volume after stretching is 2 minutes.