PurposeThis study aimed to investigate the effect of intensity and duration of continuous and interval exercise training on capillarization in skeletal muscle of healthy adults.MethodsPubMed and Web of Science were searched from inception to June 2021. Eligibility criteria for studies were endurance exercise training >2 wk in healthy adults, and the capillary to fiber ratio (C:F) and/or capillary density (CD) reported. Meta-analyses were performed, and subsequent subgroup analyses were conducted by the characteristics of participants and training scheme.ResultsFifty-seven trials from 38 studies were included (10%/90%, athletic/sedentary). C:F was measured in 391 subjects from 47 trials, whereas CD was measured in 428 subjects from 50 trials. Exercise training increased C:F (mean difference, 0.33 (95% confidence interval, 0.30–0.37)) with low heterogeneity (I2 = 45.08%) and CD (mean difference, 49.8 (36.9–62.6) capillaries per millimeter squared) with moderate heterogeneity (I2 = 68.82%). Compared with low-intensity training (<50% of maximal oxygen consumption (V̇O2max)), 21% higher relative change in C:F was observed after continuous moderate-intensity training (50%–80% of V̇O2max) and 54% higher change after interval training with high intensity (80%–100% of V̇O2max) in sedentary subjects. The magnitude of capillary growth was not dependent on training intervention duration. In already trained subjects, no additional increase in capillarization was observed with various types of training.ConclusionsIn sedentary subjects, continuous moderate-intensity training and interval training with high intensity lead to increases in capillarization, whereas low-intensity training has less effect. Within the time frame studied, no effect on capillarization was established regarding training duration in sedentary subjects. The meta-analysis highlights the need for further studies in athlete groups to discern if increased capillarization can be obtained, and if so, which combination is optimal (time vs intensity).

Purpose: This study aimed to evaluate the influence of lifelong regular physical activity on skeletal muscle capillarization in women. Methods: Postmenopausal women, 61±4 yr old, were divided according to self-reported physical activity level over the past 20 yrs: sedentary (SED; n = 14), moderately active (MOD; n = 12), and very active (VERY; n = 15). Leg blood flow (LBF) was determined by ultrasound Doppler, and blood samples were drawn from the femoral artery and vein for calculation of leg oxygen uptake (LVO 2 ) at rest and during one-legged knee extensor exercise. A skeletal muscle biopsy was obtained from the vastus lateralis and analyzed for capillarization and vascular endothelial growth factor (VEGF) and mitochondrial OXPHOS proteins. Platelets were isolated from venous blood and analyzed for VEGF content and effect on endothelial cell proliferation. Results: The exercise-induced rise in LBF and LVO 2 was faster (P = 0.008) in VERY compared with SED and MOD. Steady-state LBF and LVO 2 were lower (P < 0.04) in MOD and VERY compared with SED. Capillary-fiber ratio and capillary density were greater (P < 0.03) in VERY (1.65 ± 0.48 and 409.3 ± 57.5) compared with MOD (1.30 ± 0.19 and 365.0 ± 40.2) and SED (1.30 ± 0.30 and 356.2 ± 66.3). Skeletal muscle VEGF and OXPHOS complexes I, II, and V were ~1.6-fold and ~1.25-fold (P < 0.01) higher, respectively, in VERY compared with SED. Platelets from all groups induced an approximately nine-fold (P < 0.001) increase in endothelial cell proliferation. Conclusion: A very active lifestyle is associated with superior skeletal muscle exercise hemodynamics and greater potential for oxygen extraction concurrent with a higher skeletal muscle capillarization and mitochondrial capacity.

In this meta-analysis, the aims were to examine the effects of resistance training with and without blood flow restriction on vascular function. Five databases were searched up to June 2020 for papers about resistance training with blood flow restriction influence on vascular function. The quality of each identified study was evaluated. Effect sizes were estimated in terms of the standardized mean difference. A subgroup analysis was conducted according to participants’ age, training duration, and cuff pressure. The results of six studies on arterial compliance and five on vascular function were highly homogenous regarding responses to resistance training with or without blood flow restriction. Resistance training with blood flow restriction had a more positive effect for regulating arterial compliance than resistance training without blood flow restriction, but not for vascular function. Resistance training with blood flow restriction leads to a more positive effect on vascular function than resistance training when training for no longer than four weeks.

No abstract