Key points• Passive leg movement is associated with a ∼3-fold increase in blood flow to the leg, but the underlying mechanisms remain unknown.• Passive leg movement increased venous levels of metabolites of nitric oxide (NO) in young subjects, whereas they remained unaltered in the muscle interstitial space. Inhibition of NO synthesis lowered the vasodilatory response to passive leg movement by ∼90%.• The increase in leg blood flow was lower in elderly subjects compared to young subjects and leg blood flow did not increase when passive leg movement was performed by elderly with peripheral artery disease.• The results suggest that the hyperaemia induced by passive leg movement is NO dependent.The hyperaemic response to passive leg movement and to ACh was also assessed in elderly subjects and patients with peripheral artery disease.Abstract Passive leg movement is associated with a ∼3-fold increase in blood flow to the leg but the underlying mechanisms remain unknown. The objective of the present study was to examine the role of nitric oxide (NO) for the hyperaemia observed during passive leg movement. Leg haemodynamics and metabolites of NO production (nitrite and nitrate; NOx) were measured in plasma and muscle interstitial fluid at rest and during passive leg movement with and without inhibition of NO formation in healthy young males. The hyperaemic response to passive leg movement and to ACh was also assessed in elderly subjects and patients with peripheral artery disease. Passive leg movement (60 r.p.m.) increased leg blood flow from 0.3 ± 0.1 to 0.9 ± 0.1 litre min −1 at 20 s and 0.5 ± 0.1 litre min −1 at 3 min (P < 0.05). Mean arterial pressure remained unchanged during the trial. When passive leg movement was performed during inhibition of NO formation (N G -mono-methyl-L-arginine; 29-52 mg min −1 ), leg blood flow and vascular conductance were increased after 20 s (P < 0.05) and then returned to baseline levels, despite an increase in arterial pressure (P < 0.05). Passive leg movement increased the femoral venous NOx levels from 35 ± 5 at baseline to 62 ± 11 μmol l −1 during passive leg movement (P < 0.05), whereas muscle interstitial NOx levels remained unchanged. The hyperaemic response to passive leg movement were correlated with the vasodilatation induced by ACh (r 2 = 0.704, P < 0.001) and with age (r 2 = 0.612, P < 0.001). Leg blood flow did not increase during passive leg movement in individuals with peripheral arterial disease. These results suggest that the hypaeremia induced by passive leg movement is NO dependent and that the source of NO is likely to be the endothelium. Passive leg movement could therefore be used as a non-invasive tool to evaluate NO dependent endothelial function of the lower limb.

Peripheral arterial disease (PAD) is caused by atherosclerosis and is associated with microcirculatory impairments in skeletal muscle. The present study evaluated the angiogenic response to exercise and passive movement in skeletal muscle of PAD patients compared with healthy control subjects. Twenty-one PAD patients and 17 aged control subjects were randomly assigned to either a passive movement or an active exercise study. Interstitial fluid microdialysate and tissue samples were obtained from the thigh skeletal muscle. Muscle dialysate vascular endothelial growth factor (VEGF) levels were modestly increased in response to either passive movement or active exercise in both subject groups. The basal muscle dialysate level of the angiostatic factor thrombospondin-1 protein was markedly higher (P < 0.05) in PAD patients compared with the control subjects, whereas soluble VEGF receptor-1 dialysate levels were similar in the two groups. The basal VEGF protein content in the muscle tissue samples was ∼27% lower (P < 0.05) in the PAD patients compared with the control subjects. Analysis of mRNA expression for a range of angiogenic and angiostatic factors revealed a modest change with active exercise and passive movement in both groups, except for an increase (P < 0.05) in the ratio of angiopoietin-2 to angiopoietin-1 mRNA in the PAD group with both interventions. PAD patients and aged individuals showed a similar limited angiogenic response to active exercise and passive movement. The limited increase in muscle extracellular VEGF combined with an elevated basal level of thrombospondin-1 in muscle extracellular fluid of PAD patients may restrict capillary growth in these patients.

(PAD). Impaired limb blood flow is a major casual factor of lower exercise tolerance in PAD but cannot entirely explain it. We hypothesized that IC is associated with structural changes of the capillary-mitochondria interface that could contribute to the reduction of exercise tolerance in IC patients. Capillary and mitochondrial morphometry were performed after light and transmission electron microscopy using vastus lateralis muscle biopsies of 14 IC patients and 10 age-matched controls, and peak power output (PPO) was determined for all participants using an incremental single-leg kneeextension protocol. Capillary density was lower (411 Ϯ 90 mm Ϫ2 vs. 506 Ϯ 95 mm Ϫ2 ; P Յ 0.05) in the biopsies of the IC patients than in those of the controls. The basement membrane (BM) around capillaries was thicker (543 Ϯ 82 nm vs. 423 Ϯ 97 nm; P Յ 0.01) and the volume density of mitochondria was lower (3.51 Ϯ 0.56% vs. 4.60 Ϯ 0.74%; P Յ 0.01) in the IC patients than the controls. In the IC patients, a higher proportion of capillaries appeared with collapsed slit-like lumen and/or swollen endothelium. PPO was lower (18.5 Ϯ 9.9 W vs. 33.5 Ϯ 9.4 W; P Յ 0.01) in the IC patients than the controls. We suggest that several structural alterations in skeletal muscle, either collectively or separately, contribute to the reduction of exercise tolerance in IC patients. capillary; morphometry; peripheral arterial disease; skeletal muscle; transmission electron microscopy PERIPHERAL ARTERIAL DISEASE (PAD) is an atherosclerotic disease characterized by stenosis or occlusion of the conduit arteries of the lower limbs (20,36). Risk factors associated with PAD include advancing age, cigarette smoking, diabetes mellitus, arterial hypertension, and disturbances in lipid metabolism (12). While many PAD patients are asymptomatic, the arterial narrowing leads to ischemia and hypoxia of the supplied tissues and in severe cases, this manifests as critical limb ischemia (CLI), usually requiring surgical interventions. Intermittent claudication (IC), which is typically described as a cramp-like muscle pain during exercise, is the most commonly reported symptom of PAD and is usually the first noted symptom of the disease.Patients with IC have limited muscular strength and endurance capacities (35), reduced cardiorespiratory fitness (V O 2 peak ), and demonstrate reduced oxygen uptake kinetics at the onset of exercise (6). They also exhibit a significantly reduced tolerance for physical activities such as walking and cycling (2, 13). This reduction in exercise tolerance leads to functional impairments that are similar to those observed in patients with heart failure (31) and contributes to their impaired mobility, reduced quality of life, and elevated risk for the development of cardiovascular complications (17).Impaired limb blood flow is commonly assumed to be the main casual factor of the reduction in exercise tolerance in PAD but cannot entirely explain it. For example, restoration of blood flow capacity with percutaneous endovascular revascularizat...

Background: Peripheral arterial disease (PAD) is characterised by impaired leg blood flow, which

Aging is often associated with reduced leg blood flow, increased arterial stiffness, and endothelial dysfunction, all of which are related to declining nitric oxide (NO) bioavailability. Flow mediated dilatation (FMD) and passive leg movement (PLM) hyperaemia are two techniques used to measure NO-dependent vascular function. We hypothesised that acute dietary nitrate (NO3−) supplementation would improve NO bioavailability, leg FMD, and PLM hyperaemia. Fifteen healthy older men (69 ± 4 years) attended two experiment sessions and consumed either 140 mL of concentrated beetroot juice (800 mg NO3−) or placebo (NO3−-depleted beetroot juice) in a randomised, double blind, cross-over design study. Plasma nitrite (NO2−) and NO3−, blood pressure (BP), augmentation index (AIx75), pulse wave velocity (PWV), FMD of the superficial femoral artery, and PLM hyperaemia were measured immediately before and 2.5 h after consuming NO3− and placebo. Placebo had no effect but NO3− led to an 8.6-fold increase in plasma NO2−, which was accompanied by an increase in FMD (NO3−: +1.18 ± 0.94% vs. placebo: 0.23 ± 1.13%, p = 0.002), and a reduction in AIx75 (NO3−: −8.7 ± 11.6% vs. placebo: −4.6 ± 5.5%, p = 0.027). PLM hyperaemia, BP, and PWV were unchanged during both trials. This study showed that a dose of dietary NO3− improved NO bioavailability and enhanced endothelial function as measured by femoral artery FMD. These findings provide insight into the specific central and peripheral vascular responses to dietary NO3− supplementation in older adults.