Key result
Passive calf stretching with 10- and 20-second relaxation periods reduces arterial stiffness versus non-stretched legs.
Why the study?
It was unclear whether the relaxation period during intermittent static stretching affects elevated shear rate and arterial stiffness reduction, needed to optimize stretching protocols.
Does the duration of relaxation periods during passive intermittent static stretching affect the reduction of arterial stiffness in healthy young men?
Does the duration of relaxation periods during passive intermittent static stretching affect the reduction of arterial stiffness in healthy young men?
Intermittent static stretching with 10- to 20-second relaxation periods effectively reduces peripheral arterial stiffness, likely driven by transient increases in shear rate during reperfusion.
Hypothesis-generating for optimal stretching intervals to reduce arterial stiffness; requires confirmation before any clinical consideration.
To clarify whether the relaxation period during stretching affects the degree of elevated shear rate and the degree of reduction of arterial stiffness, we examined relaxation duration to build an adequate stretching protocol. In Experiment 1, the changes in cardiac output, the shear rate in the posterior tibial artery, and blood volume in the calf muscle were measured during recovery (0-60 s) from a single bout of one-legged passive calf stretching in 12 healthy young men. In Experiment 2, the effects of different relaxation periods (5-, 10-, 20-, and 60-s) of passive one-legged intermittent calf stretching (30-s × 6 sets) on the femoral-ankle pulse wave velocity (faPWV) as an index of peripheral arterial stiffness were identified in 17 healthy young men. As a result, the stretched leg's shear rate significantly increased from 0 to 10th s after stretching. The muscle blood volume in the stretched leg significantly reduced during stretching, and then significantly increased during the recovery period after stretching; however, cardiac output remained unchanged during stretching and recovery. Additionally, the reduction in faPWV from the pre-stretching value in the stretched leg was significantly larger in the protocol with 10-s and 20-s relaxation periods than that in the non-stretched leg, but this did not differ in the 5-s and 60-s relaxation periods. These findings suggest that the relaxation periods of intermittent static stretching that cause a high transient increase in shear rate (via reperfusion after microvascular compression by the stretched calf muscles) are effective to reduce arterial stiffness.
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Higaki et al. (2021) studied Healthy (n=29). Passive intermittent static calf stretching vs. Non-stretched leg was evaluated on Femoral-ankle pulse wave velocity (faPWV) and shear rate. Passive intermittent static calf stretching with 10-s and 20-s relaxation periods significantly reduced arterial stiffness compared to the non-stretched leg, unlike 5-s and 60-s periods.
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