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

Effect of Acute Dietary Nitrate Supplementation on the Venous Vascular Response to Static Exercise in Healthy Young Adults

The purpose of this study was to test the hypothesis that acute intake of inorganic nitrate (NO3−) via supplementation would attenuate the venoconstriction and pressor response to exercise. Sixteen healthy young adults were assigned in a randomized crossover design to receive beetroot juice (BRJ) or an NO3−-depleted control beverage (prune juice: CON). Two hours after consuming the allocated beverage, participants rested in the supine position. Following the baseline period of 4 min, static handgrip exercise of the left hand was performed at 30% of the maximal voluntary contraction for 2 min. Mean arterial pressure (MAP) and heart rate (HR) were measured. Changes in venous volume in the right forearm and right calf were also measured using venous occlusion plethysmography while cuffs on the upper arm and thigh were inflated constantly to 30−40 mmHg. The plasma NO3− concentration was elevated with BRJ intake (p < 0.05). Exercise increased MAP and HR and decreased venous volume in the forearm and calf, but there were no differences between CON and BRJ. Thus, these findings suggest that acute BRJ intake does not alter the sympathetic venoconstriction in the non-exercising limbs and MAP response to exercise in healthy young adults, despite the enhanced activity of nitric oxide.

Compliance in the deep and superficial conduit veins of the nonexercising arm is unaffected by short-term exercise

The effects of short-term dynamic and static exercise on compliance (CPL) in a single conduit vein in the nonexercising limb are not fully understood, although prolonged cycling exercise was found to produce a significant reduction of CPL in the veins. In this study, we investigated the cross-sectional area (CSA) and CPL in the brachial (deep) and basilic (superficial) veins of the nonexercising arm in 14 participants who performed a 5-min cycling exercise at 35% and 70% of peak oxygen uptake (study 1) and in 11 participants who performed a 2-min static handgrip exercise at 30% of maximal voluntary contraction (study 2). The CSA in the deep and superficial veins at rest and during the final minute of exercise was measured by high-resolution ultrasonography during a short-duration cuff deflation protocol. The CPL in each vein was calculated as the numerical derivative of the cuff pressure and CSA curve. During short-term dynamic and static exercise, there was no change in CPL in either vein, but there was a decrease in CSA in both veins. The simultaneous findings of unchanged CPL and decreased CSA suggest that CPL during short-term exercise are independently controlled by the mechanisms responsible for exercise-induced sympathoexcitation in both single veins. Thus, short-term exercise does not alter CPL in both conduit superficial and deep veins in nonexercising upper arm.

Central command increases muscular oxygenation of the non-exercising arm at the early period of voluntary one-armed cranking

This study aimed to examine whether central command increases oxygenation in non‐contracting arm muscles during contralateral one‐armed cranking and whether the oxygenation response caused by central command differs among skeletal muscles of the non‐exercising upper limb. In 13 male subjects, the relative changes in oxygenated‐hemoglobin concentration (Oxy‐Hb) of the non‐contracting arm muscles [the anterior deltoid, triceps brachii, biceps brachii, and extensor carpi radialis (ECR)] were measured during voluntary one‐armed cranking (intensity, 35–40% of maximal voluntary effort) and mental imagery of the one‐armed exercise for 1 min. Voluntary one‐armed cranking increased (P < 0.05) the Oxy‐Hb of the triceps, biceps, and ECR muscles to the same extent (15 ± 4% of the baseline level, 17 ± 5%, and 16 ± 4%, respectively). The greatest increase in the Oxy‐Hb was observed in the deltoid muscle. Intravenous injection of atropine (10–15 μg/kg) and/or propranolol (0.1 mg/kg) revealed that the increased Oxy‐Hb of the arm muscles consisted of the rapid atropine‐sensitive and delayed propranolol‐sensitive components. Mental imagery of the exercise increased the Oxy‐Hb of the arm muscles. Motor‐driven passive one‐armed cranking had little influence on the Oxy‐Hb of the arm muscles. It is likely that central command plays a role in the initial increase in oxygenation in the non‐contracting arm muscles via sympathetic cholinergic vasodilatation at the early period of one‐armed cranking. The centrally induced increase in oxygenation may not be different among the distal arm muscles but may augment in the deltoid muscle.

Decreased compliance in the deep and superficial conduit veins of the upper arm during prolonged cycling exercise

We examined whether there is a difference in compliance between the deep and superficial conduit veins of the upper arm in response to prolonged exercise. Eight young men performed cycling exercise at 60% of peak oxygen uptake until rectal temperature had been increased by 1.1°C for 38–48 min. The cross‐sectional area (CSA) of the brachial (deep) and basilic (superficial) veins was assessed by ultrasound during a cuff deflation protocol. Compliance (CPL) was calculated as the numerical derivative of the cuff pressure and CSA curve. During prolonged exercise, CPL in both conduit veins was similarly decreased when compared with pre‐exercise values; however, the CSA decreased in the deep vein but increased in the superficial vein. In addition, passive heating caused an analogous change in CSA and CPL of superficial vein when compared with prolonged exercise, but did not change CSA and CPL of deep vein. Cold pressor test induced the decreased CSA of deep and superficial veins without the alteration of CPL of both veins. These results suggest that CPL in the deep and superficial conduit veins adjusts to prolonged exercise via different mechanisms.

Superficial venous vascular response of the resting limb during static exercise and postexercise muscle ischemia

Superficial venous vascular response to exercise is mediated sympathetically, although the mechanism is not fully understood. We examined whether sympathetic activation via muscle metaboreflex plays a role in the control of a superficial vein in the contralateral resting limb during exercise. The experimental condition involved selective stimulation of muscle metaboreceptors: 12 subjects performed static handgrip exercises at 45% maximal voluntary contraction for 1.5 min followed by a recovery period with arterial occlusion of the exercise arm (OCCL). For the control condition (CONT), the same exercise protocol was performed except that the recovery period occurred without arterial occlusion. Heart rate (HR) and mean arterial blood pressure (MAP) were measured. The cross-sectional area of the basilic superficial vein (CSAvein) and blood velocity (Vvein) in the resting upper arm were measured by ultrasound while the cuff on resting upper arm was inflated constantly to a subdiastolic pressure of 50 mm Hg. Basilic vein blood flow (BFvein) was calculated as CSAvein × Vvein. During exercise under both OCCL and CONT, HR and MAP increased (p < 0.05), while CSAvein decreased (p < 0.05). During recovery under OCCL, HR returned to baseline, but the exercise-induced increase in MAP and decrease in CSAvein were maintained (p < 0.05). During recovery under CONT, HR, MAP, and CSAvein returned to baseline. BFvein did not change during exercise or recovery under either condition. These results suggest that sympathoexcitation via muscle metaboreflex may be one of the factors responsible for exercise-induced constriction of the superficial veins per se in the resting limb.