Acute Passive Stretching-induced Decrease In Joint And Arterial Stiffness: Does A Correlation Exist?

An acute bout of passive stretching could decrease both joint passive stiffness and arterial stiffness of the stretched muscle, via neural and/or mechanical mechanisms caused by alternating phases of tissue elongation and relaxation. However, whether these responses to passive stretching may be correlated is still unknown. PURPOSE: To verify whether the decrease in joint passive stiffness is correlated with the reduction in arterial stiffness induced by passive stretching and to assess possible responsible mechanisms. METHODS: The joint passive stiffness of the plantar flexor muscles (slope of the passive tension/ankle angle curve) and the popliteal artery stiffness (via tonometry approach and subsequent pulse-wave velocity calculation) were determined in 30 healthy men (age: 24 ± 2 years, stature: 1.78 ± 0.07 m, body mass: 77 ± 6 kg) before and after an acute bout of passive stretching of the plantar flexor muscles [5x(45-s stretch and 15-s rest)]. Popliteal artery blood flow and central hemodynamic variables were calculated during stretching administration. RESULTS: After passive stretching, joint and popliteal artery stiffness decreased by 24% (P < 0.001) and 6% (P = 0.01), respectively. Popliteal artery blood flow increased during the last two elongations (P = 0.005). No changes in central hemodynamics occurred. No correlation between the stretch-induced decrease in joint and arterial stiffness was found (R = -0.146, P > 0.05). CONCLUSIONS: The lack of correlation suggests that passive lengthening triggers different mechanisms responsible for mechanical properties alterations in joint and arterial stiffness.