Tendon vibration attenuates superficial venous vessel response of the resting limb during static arm exercise

BACKGROUND: The superficial vein of the resting limb constricts sympathetically during exercise. Central command is the one of the neural mechanisms that controls the cardiovascular response to exercise. However, it is not clear whether central command contributes to venous vessel response during exercise. Tendon vibration during static elbow flexion causes primary muscle spindle afferents, such that a lower central command is required to achieve a given force without altering muscle force. The purpose of this study was therefore to investigate whether a reduction in central command during static exercise with tendon vibration influences the superficial venous vessel response in the resting limb. METHODS: Eleven subjects performed static elbow flexion at 35% of maximal voluntary contraction with (EX + VIB) and without (EX) vibration of the biceps brachii tendon. The heart rate, mean arterial pressure, and rating of perceived exertion (RPE) in overall and exercising muscle were measured. The cross-sectional area (CSA(vein)) and blood velocity of the basilic vein in the resting upper arm were assessed by ultrasound, and blood flow (BF(vein)) was calculated using both variables. RESULTS: Muscle tension during exercise was similar between EX and EX + VIB. However, RPEs at EX + VIB were lower than those at EX (P <0.05). Increases in heart rate and mean arterial pressure during exercise at EX + VIB were also lower than those at EX (P <0.05). CSA(vein) in the resting limb at EX decreased during exercise from baseline (P <0.05), but CSA(vein) at EX + VIB did not change during exercise. CSA(vein) during exercise at EX was smaller than that at EX + VIB (P <0.05). However, BF(vein) did not change during the protocol under either condition. The decreases in circulatory response and RPEs during EX + VIB, despite identical muscle tension, showed that activation of central command was less during EX + VIB than during EX. Abolishment of the decrease in CSA(vein) during exercise at EX + VIB may thus have been caused by a lower level of central command at EX + VIB rather than EX. CONCLUSION: Diminished central command induced by tendon vibration may attenuate the superficial venous vessel response of the resting limb during sustained static arm exercise.