Skeletal muscle capillarization is a determining factor in gas and metabolite exchange, while its impairments may contribute to the development of sarcopenia. Studies on the potential of resistance training (RT) to induce angiogenesis in older muscles have been inconclusive, and effects of sequential endurance training (ET) and RT on capillarization are unknown. Healthy older men (66.5 ± 3.8 years) were engaged in either 12 weeks of habitual course observation (HC) followed by 12 weeks of RT (n = 8), or 12 weeks of high-intensity interval training (HIIT) followed by 12 weeks of RT (n = 9). At baseline, following 12 and 24 weeks, m. vastus lateralis biopsies were obtained. (Immuno-)histochemistry was used to assess indices of muscle fiber capillarization, muscle fiber morphology and succinate dehydrogenase (SDH) activity. Single periods of RT and HIIT resulted in similar improvements in capillarization and SDH activity. During RT following HIIT, improved capillarization and SDH activity, as well as muscle fiber morphology remained unchanged. The applied RT and HIIT protocols were thus similarly effective in enhancing capillarization and oxidative enzyme activity and RT effectively preserved HIIT-induced adaptations of these parameters. Hence, both, RT and HIIT, are valid training modalities for older men to improve skeletal muscle vascularization.Aging is associated with reduced cardiorespiratory fitness 1,2 and impaired responsiveness of skeletal muscle tissue to anabolic stimuli 3-5 . Skeletal muscle capillarization can affect both cardiorespiratory fitness and muscle anabolism. Enhanced capillarization ameliorates gas and metabolite exchange between blood and muscle tissue, resulting in improved peak oxygen uptake (  VO peak 2 ) and oxidative capacity 6,7 . Likewise, it has been proposed, that increased blood flow to muscles is required to support muscle fiber hypertrophy and satellite cell activation in older adults by facilitating the delivery of nutrients, cytokines and growth factors 8,9 . Furthermore, a recent study by Prior et al. 10 revealed that sarcopenic older adults have lower values for capillarization indices when compared to non-sarcopenic controls. Taken together, emerging evidence suggests that a decline in capillarization with increasing age might contribute to the development of sarcopenia and functional impairments in older adults.Endurance-type training (ET) is considered the method of choice for improving capillarization in skeletal muscle and inducing the associated local and systemic health-related benefits. While ET has consistently been demonstrated to stimulate angiogenesis and to substantially increase skeletal muscle capillarization and  VO peak 2 in older adults 6,7,11 , data on the potential of resistance training (RT) to effectively induce angiogenesis in aged muscle has been inconclusive. Some studies reported an increase in capillarization following 9-24 weeks of

Background Single repetition, contraction-phase specific and total time-under-tension (TUT) are crucial mechano-biological descriptors associated with distinct morphological, molecular and metabolic muscular adaptations in response to exercise, rehabilitation and/or fighting sarcopenia. However, to date, no simple, reliable and valid method has been developed to measure these descriptors. Objective In this study we aimed to test whether accelerometer data obtained from a standard smartphone placed on the weight stack can be used to extract single repetition, contraction-phase specific and total TUT. Methods Twenty-two participants performed two sets of ten repetitions of their 60% one repetition maximum with a self-paced velocity on nine commonly used resistance exercise machines. Two identical smartphones were attached on the resistance exercise weight stacks and recorded all user-exerted accelerations. An algorithm extracted the number of repetitions, single repetition, contraction-phase specific and total TUT. All exercises were videorecorded. The TUT determined from the algorithmically-derived mechano-biological descriptors was compared with the video recordings that served as the gold standard. The agreement between the methods was examined using Limits of Agreement (LoA). The association was calculated using the Pearson correlation coefficients and interrater reliability was determined using the intraclass correlation coefficient (ICC 2.1). Results The error rate of the algorithmic detection of single repetitions derived from two smartphones accelerometers was 0.16%. Comparing algorithmically-derived, contraction-phase

PURPOSE: It is a widely accepted premise in the scientific community and by athletes alike, that adding resistance exercise to a regular regimen of endurance training increases endurance performance in endurance-trained men. However, critical power (CP), capillarization, and myofiber size remain unaffected by this addition. Therefore, we tested whether the superimposition of resistance exercise with whole-body vibration and vascular occlusion (vibroX) would improve these variables in endurance-trained males relative to resistance exercise alone. METHODS: Twenty-one young, endurance-trained males were randomly assigned either to a vibroX (n = 11) or resistance (n = 10) training group. Both groups trained in a progressive mode twice a week for 8 weeks. Pre and post training, histochemical muscle characteristics, thigh muscle size, endurance and strength parameters were determined. RESULTS: vibroX increased CP (P = 0.001), overall capillary-to-fiber ratio (P = 0.001) and thigh lean mass (P < 0.001), while these parameters were unaffected by resistance training. The gain in CP by vibroX was positively correlated with the gain in capillarization (R (2) = 0.605, P = 0.008), and the gain in thigh lean mass was paralleled by increases in MyHC-1 and MyHC-2 fiber cross-sectional areas and strength. Maximum voluntary torque and the finite work capacity above CP (W') increased significantly only following resistance training. CONCLUSIONS: We achieved a proof of concept by demonstrating that modification of resistance exercise by superimposing side-alternating whole-body vibration and sustained vascular occlusion induced further improvements in CP, capillarization and hypertrophy, all of which were not observed with resistance training alone. Purpose: It is a widely-accepted premise in the scientific community and by athletes alike, 2 that adding resistance exercise to a regular regimen of endurance training increases 3 endurance performance in endurance-trained men. However, critical power (CP), 4 capillarization, and myofiber size remain unaffected by this addition. Therefore, we tested 5 whether the superimposition of resistance exercise with whole-body vibration and vascular 6 occlusion (vibroX) would improve these variables in endurance-trained males relative to 7 resistance exercise alone. Methods: Twenty-one young, endurance-trained males were 8 randomly assigned either to a vibroX (n = 11) or resistance (n = 10) training group. Both 9 groups trained in a progressive mode twice a week for 8 weeks. Pre and post training, 10 histochemical muscle characteristics, thigh muscle size, endurance and strength parameters 11 were determined. Results: vibroX increased CP (P = 0.001), overall capillary-to-fiber ratio 12 (P = 0.001) and thigh lean mass (P < 0.001), while these parameters were unaffected by 13 resistance training. The gain in CP by vibroX was positively correlated with the gain in 14 capillarization (R 2 = 0.605, P = 0.008), and the gain in thigh lean mass was paralleled by 15 increases in MyHC-1 and MyHC...

Skeletal muscle is one of the most important tissues of the human body. It comprises up to 40% of the body mass and is crucial to survival. Hence, the maintenance of skeletal muscle mass and strength is pivotal. It is well-established that resistance exercise provides a potent anabolic stimulus to increase muscle mass and strength in men and women of all ages. Resistance exercise consists of mechano-biological descriptors, such as load, muscle action, number of repetitions, repetition duration, number of sets, rest interval between sets, frequency, volitional muscular failure, and range of motion, which can be manipulated. Herein, we discuss the evidence-based contribution of these mechano-biological descriptors to muscle mass and strength.

New Findings r What is the central question of this study?Acute skeletal muscle satellite cell (SC) activation is associated with skeletal muscle hypertrophy. Although the quantity of SCs has been reported to increase following a single bout of resistance exercise, data on muscle fibre type-specific SC quantity and/or activation status after a single bout of vibration is presently lacking. r What is the main finding and its importance?By determining SCs from muscle biopsies of the vastus lateralis using immunohistochemistry, we conclude that modification of vibration exercise by superimposition of occlusion induced activation and differentiation of SCs in young men, which had not been observed with whole-body vibration or blood flow restriction alone.We tested the hypothesis that whole-body vibration (WBV) is insufficient to expand satellite cell numbers 24 h postexercise, whereas WBV in combination with blood flow restriction (BFR) is sufficient. Twenty-five young men were randomly assigned to one of the following three groups: WBV, BFR exercise or WBVBFR. Satellite cell numbers were determined from muscle biopsies of the vastus lateralis muscle using immunohistochemistry. Satellite cell quantity and frequency (+99.4%, P = 0.012 and +77.1%, P = 0.010, respectively) increased only in the WBVBFR group. Similar results were obtained for the quantity and frequency of myogenin-positive myonuclei (+139.0%, P < 0.001 and +148.4%, P < 0.001, respectively). We conclude that modification of WBV by superimposition of BFR induced activation and differentiation of satellite cells in young men, which had not been observed with WBV or BFR alone. These data suggest that WBVBFR might represent a novel viable anabolic stimulus.