Aging and the Skeletal Muscle Angiogenic Response to Exercise in Women

Exercise training alters skeletal muscle microvascular endothelial cell properties in recent postmenopausal females

The present study examined and compared the impact of exercise training on redox and molecular properties of human microvascular endothelial cells derived from skeletal muscle biopsies from sedentary recent (RPF, ≤ 5 years as postmenopausal) and late (LPF, ≥ 10 years as postmenopausal) postmenopausal females. Resting skeletal muscle biopsies were obtained before and after 8 weeks of intense aerobic exercise training for isolation of microvascular endothelial cells and determination of skeletal muscle angiogenic proteins and capillarisation. The microvascular endothelial cells were analysed for mitochondrial respiration and production of reactive oxygen species (ROS), glycolysis and proteins related to vascular function, redox balance and oestrogen receptors. Exercise training led to a reduced endothelial cell ROS formation (∼50%; P = 0.009 and P = 0.020 for intact and permeabilized cells (state 3), respectively) in RPF only, with no effect on endothelial mitochondrial capacity in either group. Basal endothelial cell lactate formation was higher (7%; P = 0.028), indicating increased glycolysis, after compared to before the exercise training period in RPF only. Baseline endothelial G protein-coupled oestrogen receptor (P = 0.028) and muscle capillarisation (P = 0.028) was lower in LPF than in RPF. Muscle vascular endothelial growth factor protein was higher (32%; P = 0.002) following exercise training in LPF only. Exercise training did not influence endothelial cell proliferation or skeletal muscle capillarisation in either group, but the CD31 level in the muscle tissue, indicating endothelial cell content, was higher (>50%; P < 0.05) in both groups. In conclusion, 8 weeks of intense aerobic exercise training reduces ROS formation and enhances glycolysis in microvascular endothelial cells from RPF but does not induce skeletal muscle angiogenesis. KEY POINTS: Late postmenopausal females have been reported to achieve limited vascular adaptations to exercise training. There is a paucity of data on the effect of exercise training on isolated skeletal muscle microvascular endothelial cells (MMECs). In this study the formation of reactive oxygen species in MMECs was reduced and glycolysis increased after 8 weeks of aerobic exercise training in recent but not late postmenopausal females. Late postmenopausal females had lower levels of G protein-coupled oestrogen receptor in MMECs and lower skeletal muscle capillary density at baseline. Eight weeks of intense exercise training altered MMEC properties but did not induce skeletal muscle angiogenesis in postmenopausal females.

A high-resolution view of the heterogeneous aging endothelium

Vascular endothelial cell (EC) aging has a strong impact on tissue perfusion and overall cardiovascular health. While studies confined to the investigation of aging-associated vascular readouts in one or a few tissues have already drastically expanded our understanding of EC aging, single-cell omics and other high-resolution profiling technologies have started to illuminate the intricate molecular changes underlying endothelial aging across diverse tissues and vascular beds at scale. In this review, we provide an overview of recent insights into the heterogeneous adaptations of the aging vascular endothelium. We address critical questions regarding tissue-specific and universal responses of the endothelium to the aging process, EC turnover dynamics throughout lifespan, and the differential susceptibility of ECs to acquiring aging-associated traits. In doing so, we underscore the transformative potential of single-cell approaches in advancing our comprehension of endothelial aging, essential to foster the development of future innovative therapeutic strategies for aging-associated vascular conditions.

Peripheral limitations for performance: Muscle capillarization

Sufficient delivery of oxygen and metabolic substrates, together with removal of waste products, are key elements of muscle performance. Capillaries are the primary site for this exchange in skeletal muscle and the degree of muscle capillarization affects diffusion conditions by influencing mean transit time, capillary surface area and diffusion distance. Muscle capillarization may thus represent a limiting factor for performance. Exercise training increases the number of capillaries per muscle fiber by about 10%-20% within a few weeks in untrained subjects, whereas capillary growth progresses more slowly in well-trained endurance athletes. Studies show that capillaries are tortuous, situated along and across the length of the fibers with an arrangement related to muscle fascicles. Although direct data is lacking, it is possible that years of training not only enhances capillary density but also optimizes the positioning of capillaries, to further improve the diffusion conditions. Muscle capillarization has been shown to increase oxygen extraction during exercise in humans, but direct evidence for a causal link between increased muscle capillarization and performance is scarce. This review covers current knowledge on the implications of muscle capillarization for oxygen and glucose uptake as well as performance. A brief overview of the process of capillary growth and of physical factors, inherent to exercise, which promote angiogenesis, provides the foundation for a discussion on how different training modalities may influence muscle capillary growth. Finally, we identify three areas for future research on the role of capillarization for exercise performance.

Cyclooxygenase inhibition does not blunt thermal hyperemia in skeletal muscle of humans

Acute heat exposure increases skeletal muscle blood flow in humans. However, the mechanisms mediating this hyperemic response remain unknown. The cyclooxygenase pathway is active in skeletal muscle, is heat sensitive, and contributes to cutaneous thermal hyperemia in young healthy humans. Therefore, the purpose of this study was to test the hypothesis that cyclooxygenase inhibition would attenuate blood flow in the vastus lateralis muscle during localized heating. Twelve participants (6 women) were studied on two separate occasions: 1) time control (i.e., no ibuprofen); and 2) ingestion of 800 mg ibuprofen, a nonselective cyclooxygenase inhibitor. Experiments were randomized, counter-balanced, and separated by at least 10 days. Pulsed short-wave diathermy was used to induce unilateral deep heating of the vastus lateralis for 90 min, whereas the contralateral leg served as a thermoneutral control. Microdialysis was utilized to bypass the cutaneous circulation and directly measure local blood flow in the vastus lateralis muscle of each leg via the ethanol washout technique. Heat exposure increased muscle temperature and local blood flow (both P < 0.01 vs. baseline). However, the thermal hyperemic response did not differ between control and ibuprofen conditions (P ≥ 0.2). Muscle temperature slightly decreased for the thermoneutral leg (P < 0.01 vs. baseline), yet local blood flow remained relatively unchanged across time for control and ibuprofen conditions (both P ≥ 0.7). Taken together, our data suggest that inhibition of cyclooxygenase-derived vasodilator prostanoids does not blunt thermal hyperemia in skeletal muscle of young healthy humans.NEW & NOTEWORTHY Acute heat exposure increases skeletal muscle blood flow in humans. However, the mechanisms mediating this hyperemic response remain unknown. Using a pharmacological approach combined with microdialysis, we found that thermal hyperemia in the vastus lateralis muscle was well maintained despite the successful inhibition of cyclooxygenase. Our results suggest that cyclooxygenase-derived vasodilator prostanoids do not contribute to thermal hyperemia in skeletal muscle of young healthy humans.

Type II Muscle Fiber Capillarization Is an Important Determinant of Post-Exercise Microvascular Perfusion in Older Adults

INTRODUCTION

Microvascular perfusion is essential for post-exercise skeletal muscle recovery to ensure adequate delivery of nutrients and growth factors. This study assessed the relationship between various indices of muscle fiber capillarization and microvascular perfusion assessed by contrast-enhanced ultrasound (CEUS) at rest and during recovery from a bout of resistance exercise in older adults.

METHODS

Sixteen older adults (72 ± 6 y, 5/11 male/female) participated in an experimental test day during which a muscle biopsy was collected from the vastus lateralis and microvascular perfusion was determined by CEUS at rest and at 10 and 40 min following a bout of resistance exercise. Immunohistochemistry was performed on muscle tissue samples to determine various indices of both mixed and fiber-type-specific muscle fiber capillarization.

RESULTS

Microvascular blood volume at t = 10 min was higher compared with rest and t = 40 min (27.2 ± 4.7 vs. 3.9 ± 4.0 and 7.0 ± 4.9 AU, respectively, both p < 0.001). Microvascular blood volume at t = 40 min was higher compared with rest (p < 0.001). No associations were observed between different indices of mixed muscle fiber capillarization and microvascular blood volume at rest and following exercise. A moderate (r = 0.59, p < 0.05) and strong (r = 0.81, p < 0.001) correlation was observed between type II muscle fiber capillary-to-fiber ratio and the microvascular blood volume increase from rest to t = 10 and t = 40 min, respectively. In addition, type II muscle fiber capillary contacts and capillary-to-fiber perimeter exchange index were strongly correlated with the microvascular blood volume increase from rest to t = 40 min (r = 0.66, p < 0.01 and r = 0.64, p < 0.01, respectively).

CONCLUSION

Resistance exercise strongly increases microvascular blood volume for at least 40 min after exercise cessation in older adults. This resistance exercise-induced increase in microvascular blood volume is strongly associated with type II muscle fiber capillarization in older adults.

Tissue Perfusion and Diffusion and Cellular Respiration: Transport and Utilization of Oxygen

This article provides an overview of the journey of inspired oxygen after its uptake across the alveolar-capillary interface, and the interplay among tissue perfusion, diffusion, and cellular respiration in the transport and utilization of oxygen. The critical interactions between oxygen and its facilitative carriers (hemoglobin in red blood cells and myoglobin in muscle cells), and with other respiratory and vasoactive molecules (carbon dioxide, nitric oxide, and carbon monoxide), are emphasized to illustrate how this versatile system dynamically optimizes regional convective transport and diffusive gas exchange. The rates of reciprocal gas exchange in the lung and the periphery must be well-matched and sufficient for meeting the range of energy demands from rest to maximal stress but not excessive as to become toxic. The mobile red blood cells play a vital role in matching tissue perfusion and gas exchange by dynamically regulating the controlled uptake of oxygen and communicating regional metabolic signals across different organs. Intracellular oxygen diffusion and facilitation via myoglobin into the mitochondria, and utilization via electron transport chain and oxidative phosphorylation, are summarized. Physiological and pathophysiological adaptations are briefly described. Dysfunction of any component across this integrated system affects all other components and elicits corresponding structural and functional adaptation aimed at matching the capacities across the entire system and restoring equilibrium under normal and pathological conditions.

Effects of the Foam Massage Roller on VEGF-A and FGF-2 Blood Levels in Young Men

BACKGROUND/AIM

Angiogenesis induced in muscles or massaged tissue is thought to support their regeneration and performance. Therefore, different methods that could promote angiogenesis are investigated. The aim of this study was to examine whether the use of the foam roller massager for lower limb muscles affects VEGF-A and FGF-2 levels in young men.

MATERIALS AND METHODS

The study group included 60 healthy young men attending Military University of Land Forces, Wroclaw, Poland. The participants were randomly divided into two groups. The experimental group included 40 individuals who performed self-massage of the lower limbs using a foam roller. The control group comprised 20 individuals who did not perform massage. Massage was applied to lower limb muscles four times a week for seven weeks. Blood was collected before the experiment and after weeks 1, 3, 5, and 7. ELISA was used to determine changes in VEGF-A and FGF-2 levels in blood serum.

RESULTS

The results of the study demonstrated a significant increase in VEGF-A serum levels in the group of individuals who underwent massage each week compared to VEGF-A concentrations before the experiment. The increase in VEGF-A levels in the experimental group was observed throughout the experiment compared to the control group. No significant changes in serum FGF-2 levels were found.

CONCLUSION

The use of a foam massage roller increased VEGF-A serum levels, which may indicate stimulation of angiogenesis.

Targeting aging with the healthy skeletal system: The endocrine role of bone

Aging is an inevitable biological process, and longevity may be related to bone health. Maintaining strong bone health can extend one's lifespan, but the exact mechanism is unclear. Bone and extraosseous organs, including the heart and brain, have complex and precise communication mechanisms. In addition to its load bearing capacity, the skeletal system secretes cytokines, which play a role in bone regulation of extraosseous organs. FGF23, OCN, and LCN2 are three representative bone-derived cytokines involved in energy metabolism, endocrine homeostasis and systemic chronic inflammation levels. Today, advanced research methods provide new understandings of bone as a crucial endocrine organ. For example, gene editing technology enables bone-specific conditional gene knockout models, which allows the study of bone-derived cytokines to be more precise. We systematically evaluated the various effects of bone-derived cytokines on extraosseous organs and their possible antiaging mechanism. Targeting aging with the current knowledge of the healthy skeletal system is a potential therapeutic strategy. Therefore, we present a comprehensive review that summarizes the current knowledge and provides insights for futures studies.

Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia

BACKGROUND

Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ([Formula: see text]O_2peak). We aimed to detect the contribution of cardiac output to ([Formula: see text]) and arteriovenous oxygen difference [Formula: see text] to [Formula: see text] from rest to peak exercise in patients with FM.

METHODS

Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. [Formula: see text] (impedance cardiography) was monitored. [Formula: see text] was calculated using Fick's equation. Linear regression slopes for oxygen cost (∆[Formula: see text]O₂/∆work rate) and [Formula: see text] to [Formula: see text]O₂ (∆[Formula: see text]/∆[Formula: see text]O₂) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range].

RESULTS

[Formula: see text]O_2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min^-1∙kg^-1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min^-1∙kg FFM^-1, P < 0.001). [Formula: see text] and C(a-v)O₂ were similar between groups at submaximal work rates, but peak [Formula: see text] (14.17 [13.34-16.03] vs. 16.06 [15.24-16.99] L∙min^-1, P = 0.005) and C(a-v)O₂ (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O₂∙100 mL blood^-1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆[Formula: see text]O₂/∆work rate (11.1 vs. 10.8 mL∙min^-1∙W^-1, P = 0.248) or ∆[Formula: see text]/∆[Formula: see text]O₂ (6.58 vs. 5.75, P = 0.122) slopes.

CONCLUSIONS

Both [Formula: see text] and C(a-v)O₂ contribute to lower [Formula: see text]O_2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03300635. Registered 3 October 2017-Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635 .

Exercise-induced angiogenesis is attenuated by captopril but maintained under perindopril treatment in hypertensive rats

Angiogenesis is an important exercise-induced response to improve blood flow and decrease vascular resistance in spontaneously hypertensive rats (SHR), but some antihypertensive drugs attenuate this effect. This study compared the effects of captopril and perindopril on exercise-induced cardiac and skeletal muscle angiogenesis. Forty-eight Wistar rats and 48 SHR underwent 60 days of aerobic training or were kept sedentary. During the last 45 days, rats were treated with captopril, perindopril or water (Control). Blood pressure (BP) measurements were taken and histological samples from the tibialis anterior (TA) and left ventricle (LV) muscles were analyzed for capillary density (CD) and vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2) and endothelial nitric oxide synthase (eNOS) protein level. Exercise increased vessel density in Wistar rats due to higher VEGFR-2 (+17%) and eNOS (+31%) protein level. Captopril and perindopril attenuated exercise-induced angiogenesis in Wistar rats, but the attenuation was small in the perindopril group, and this response was mediated by higher eNOS levels in the Per group compared to the Cap group. Exercise increased myocardial CD in Wistar rats in all groups and treatment did not attenuate it. Both exercise and pharmacological treatment reduced BP of SHR similarly. Rarefaction was found in TA of SHR compared to Wistar, due to lower levels of VEGF (-26%) and eNOS (-27%) and treatment did not avoid this response. Exercise prevented these reductions in control SHR. While rats treated with perindopril showed angiogenesis in the TA muscle after training, those rats treated with captopril showed attenuated angiogenesis (-18%). This response was also mediated by lower eNOS levels in Cap group compared with Per and control group. Myocardial CD was reduced in all sedentary hypertensive compared with Wistar and training restored the number of vessels compared with sedentary SHR. In conclusion, taken into account only the aspect of vessel growth, since both pharmacological treatments reduced BP in SHR, the result of the present study suggests that perindopril could be a drug of choice over captopril for hypertensive practitioners of aerobic physical exercises, especially considering that it does not attenuate angiogenesis induced by aerobic physical training in skeletal and cardiac muscles.

Pelvic floor muscle rehabilitation for genitourinary syndrome of menopause: why, how and when?

Genitourinary syndrome of menopause (GSM) is caused by chronic deprivation of estrogen and other sex steroids during the postmenopausal period, which leads to changes in the vulvovaginal tissues. These changes cause bothersome symptoms, such as vaginal dryness, pruritus, dyspareunia, increased daytime urinary frequency, urgency and urinary incontinence, which have considerable negative effects on women's quality of life and sexual function. Recent studies have investigated a novel treatment approach for GSM. Pelvic floor muscle (PFM) rehabilitation, a low-cost conservative management with no side-effects, has been studied alone or in combination with other treatment modalities to reduce the signs and symptoms of GSM. The aim of this article is to discuss why PFM rehabilitation could be useful for women with GSM, how it may help improve signs and symptoms of GSM and when this treatment should be recommended.

Exercise-induced skeletal muscle angiogenesis: impact of age, sex, angiocrines and cellular mediators

Exercise-induced skeletal muscle angiogenesis is a well-known physiological adaptation that occurs in humans in response to exercise training and can lead to endurance performance benefits, as well as improvements in cardiovascular and skeletal tissue health. An increase in capillary density in skeletal muscle improves diffusive oxygen exchange and waste extraction, and thus greater fatigue resistance, which has application to athletes but also to the general population. Exercise-induced angiogenesis can significantly contribute to improvements in cardiovascular and metabolic health, such as the increase in muscle glucose uptake, important for the prevention of diabetes. Recently, our understanding of the mechanisms by which angiogenesis occurs with exercise has grown substantially. This review will detail the biochemical, cellular and biomechanical signals for exercise-induced skeletal muscle angiogenesis, including recent work on extracellular vesicles and circulating angiogenic cells. In addition, the influence of age, sex, exercise intensity/duration, as well as recent observations with the use of blood flow restricted exercise, will also be discussed in detail. This review will provide academics and practitioners with mechanistic and applied evidence for optimising training interventions to promote physical performance through manipulating capillarisation in skeletal muscle.

The impact of aging and physical training on angiogenesis in the musculoskeletal system

Angiogenesis is the physiological process of capillary growth. It is strictly regulated by the balanced activity of agents that promote the formation of capillaries (pro-angiogenic factors) on the one hand and inhibit their growth on the other hand (anti-angiogenic factors). Capillary rarefaction and insufficient angiogenesis are some of the main causes that limit blood flow during aging, whereas physical training is a potent non-pharmacological method to intensify capillary growth in the musculoskeletal system. The main purpose of this study is to present the current state of knowledge concerning the key signalling molecules implicated in the regulation of skeletal muscle and bone angiogenesis during aging and physical training.

Acute heat exposure improves microvascular function in skeletal muscle of aged adults

Acute heat exposure improves microvascular function in aged adults as assessed using reactive hyperemia. The cutaneous and skeletal muscle microcirculations are thought to contribute to this response, but this has never been confirmed due to the methodological challenges associated with differentiating blood flow between these vascular beds. We hypothesized that acute hot water immersion would improve endothelial-dependent, but not endothelial-independent vasodilation in the microcirculation of the vastus lateralis muscle in healthy aged adults. Participants (70 ± 5 yr) were immersed for 60 min in thermoneutral (36°C) or hot (40°C) water. Ninety minutes following immersion, skeletal muscle microdialysis was used to bypass the cutaneous circulation and directly assess endothelial-dependent and endothelial-independent vasodilation by measuring the local hyperemic response to graded infusions of acetylcholine (ACh, 27.5 and 55.0 mM) and sodium nitroprusside (SNP, 21 and 42 mM), respectively. The hyperemic response to 27.5 mM ACh did not differ between thermal conditions (P = 0.9). However, the hyperemic response to 55.0 mM ACh was increased with prior hot water immersion (thermoneutral immersion, 43.9 ± 23.2 mL/min/100 g vs. hot water immersion, 66.5 ± 25.5 mL/min/100 g; P < 0.01). Similarly, the hyperemic response to 21 mM SNP did not differ between thermal conditions (P = 0.3) but was increased following hot water immersion with the infusion of 42 mM SNP (thermoneutral immersion, 48.8 ± 25.6 mL/min/100 g vs. hot water immersion, 90.7 ± 53.5 mL/min/100 g; P < 0.01). These data suggest that acute heat exposure improves microvascular function in skeletal muscle of aged humans.NEW & NOTEWORTHY Acute heat exposure improves microvascular function in aged adults as assessed using reactive hyperemia. The cutaneous and skeletal muscle microcirculations are thought to contribute to this response, but this has never been confirmed due to the methodological challenges associated with differentiating blood flow between these vascular beds. Using the microdialysis technique to bypass the cutaneous circulation, we demonstrated that heat exposure improves endothelial-dependent and endothelial-independent vasodilation in the microcirculation of skeletal muscle in aged humans.

Effects of different types of exercise training on angiogenic responses in the left ventricular muscle of aged rats

BACKGROUND

We evaluated angiogenic responses in the left ventricular muscle and aerobic capacity according to exercise type (aerobic, resistance, combined) in aged rats.

METHODS

In total, 24 male Sprague-Dawley rats (100 weeks old) were used. To investigate the effect of regular training, the rats were divided into non-exercise (NE), aerobic exercise (AE), resistance exercise (RE), and combined exercise (CE) groups (six rats per group). Regular training tailored to each exercise type was performed for 8 weeks (five times a week, 1 h per day). After 8 weeks of training, aerobic capacity was evaluated by a treadmill running test. Left ventricular muscle tissue was collected and the protein levels of angiogenesis indicators (eNOS, HIF-1α, PGC-1α, VEGF, FLK-1, Ang-1, Ang-2) were analyzed by Western blotting. Capillaries were observed by immunohistochemical staining for CD31.

RESULTS

Body weight, heart weight, and heart/body weight ratio showed no difference among the groups. The AE and CE groups showed higher treadmill running capacity than the NE and RE groups. The eNOS, VEGF, HIF-1α, PGC-1α, and Ang-2 protein levels were significantly higher in the AE than NE group. The PGC-1α and FLK-1 protein levels were significantly higher in the RE than NE group. In addition, in the CE group, the eNOS, FLK-1, and PGC-1α protein levels were significantly higher than in the NE group. Expression of CD31 in cardiac tissue was higher in the AE and CE groups than in the other groups.

CONCLUSIONS

Taken together, the results suggest that regular exercise training, irrespective of exercise type, might improve cardiovascular function by inducing angiogenic responses in the aged myocardium; however, AE may be the most effective.

Endurance training-induced increase in muscle oxidative capacity without loss of muscle mass in younger and older resistance-trained men

While concurrent training is regularly used in older populations, the inverse relationship between fibre size and oxidative capacity suggests that endurance training in resistance-trained individuals may result in some loss of resistance training-induced gains in muscle mass, which may be more pronounced in older people. We investigated the impact of superimposed endurance training in younger (28.5 ± 4.8 years; n = 8) and older (67.5 ± 5.5 years; n = 7) highly resistance-trained men. Participants underwent a 10-week endurance cycling training programme consisting of five 6-min intervals at 75% max heart rate (HRmax) separated by 4-min intervals at 90% HRmax. The anatomical cross-sectional area (ACSA) of the thigh muscles, as determined with MRI, was 24% smaller in older compared to younger participants (p < 0.001). Although maximal oxygen consumption (VO₂max) was also lower in the older group (p < 0.001), VO₂max per kg body mass did not differ significantly between younger and older participants. Histological analyses of biopsies of the m. vastus lateralis showed that endurance training induced an increase in succinate dehydrogenase activity in both younger and older participants (p ≤ 0.043), and an increase in the number of capillaries around type I fibres (p = 0.017). The superimposed endurance training did not induce a significant decrease in thigh ACSA, fibre cross-sectional area, or knee extensor maximum voluntary isometric force. These observations indicate that adding endurance training to resistance training can lead to positive endurance-related adaptations without negative consequences for muscle size and strength in older and younger resistance-trained people.

Menopausal transition does not influence skeletal muscle capillary growth in response to cycle training in women

The influence of the menopausal transition, with a consequent loss of estrogen, on capillary growth in response to exercise training remains unknown. In the present study, we evaluated the effect of a period of intense endurance training on skeletal muscle angiogenesis in late premenopausal and recent postmenopausal women with an age difference of <4 yr. Skeletal muscle biopsies were obtained from the thigh muscle before and after 12 wk of intense aerobic cycle training and analyzed for capillarization, fiber-type distribution, and content of vascular endothelial growth factor (VEGF). At baseline, there was no difference in capillary per fiber ratio (C:F; 1.41 ± 0.22 vs. 1.40 ± 0.30), capillary density (CD; 305 ± 61 vs. 336 ± 52 mm²), muscle fiber area (MFA; 4,889 ± 1,868 vs. 4,195 ± 749), or distribution of muscle fiber type I (47.3% ± 10.1% vs. 49.3% ± 15.1%), between the pre- and postmenopausal women, respectively. There was a main effect of training on the C:F ratio (+9.2% and +12.1%, for the pre- and postmenopausal women, respectively) and the CD (+6.9% and +8.9%, for the pre- and postmenopausal women, respectively). MFA and fiber-type distribution were unaltered by training. Skeletal muscle VEGF protein content was similar between groups at baseline, and there was a main effect of training (+21.1% and +27.2%, for the pre- and postmenopausal women, respectively). In conclusion, the loss of estrogen per se at menopause does not influence the capillary growth response to intense aerobic exercise training.NEW & NOTEWORTHY We evaluated the effect of 12 wk of intense aerobic exercise training on skeletal muscle angiogenesis in late pre- and recent postmenopausal women, with <4 yr of age difference. There was a main effect of training on capillary per fiber ratio, capillary density, and muscle VEGF protein content, with no difference between groups. It is concluded that the loss of estrogen per se at menopause does not influence the capillary growth response to intense aerobic training.

Effects of exercise training with weight loss on skeletal muscle expression of angiogenic factors in overweight and obese older men

Low skeletal muscle capillarization is associated with impaired glucose tolerance (IGT); however, aerobic exercise training with weight loss (AEX + WL) increases skeletal muscle capillarization and improves glucose tolerance in adults with IGT. Given that the expression of angiogenic growth factors mediates skeletal muscle capillarization, we sought to determine whether angiogenic growth factor levels are associated with low capillarization in those with IGT versus normal glucose tolerance (NGT) or to the benefits of AEX + WL in both groups. Sixteen overweight or obese men 50-75 yr of age completed 6 mo of AEX + WL with oral glucose tolerance tests and vastus lateralis muscle biopsies for measurement of muscle vascular endothelial growth factor (VEGF), placental growth factor (PlGF), soluble fms-like tyrosine kinase receptor-1 (sFlt-1), and basic fibroblast growth factor (bFGF). At baseline, all growth factor levels were numerically lower in IGT than NGT, but these did not reach statistical significance (P = 0.06-0.33). Following AEX + WL, aerobic capacity [maximal oxygen consumption (V̇o2max)] increased by 16%, whereas body weight and 120-min postprandial glucose levels decreased by 10% and 15%, respectively (P ≤ 0.001 for all). There was a main effect of AEX + WL to increase VEGF (0.095 ± 0.016 vs. 0.114 ± 0.018 ng/µg, P < 0.05), PlGF (0.004 ± 0.001 vs. 0.005 ± 0.001 ng/µg, P < 0.05), and sFlt-1 (0.216 ± 0.029 vs. 0.264 ± 0.036 ng/µg, P < 0.01), with overall increases driven by the IGT group. These results suggest that 6 mo of AEX + WL increases skeletal muscle angiogenic growth factor levels in obese older adults with IGT and NGT, which may contribute to our previous findings that AEX + WL increases capillarization to improve glucose tolerance in those with IGT.NEW & NOTEWORTHY Skeletal muscle capillarization is lower in adults with impaired glucose tolerance than normal controls. This may, in part, be attributable to differential expression of angiogenic growth factors in skeletal muscle. Using a 6-mo aerobic exercise intervention with ∼10% body weight loss (AEX + WL), we show that the expression of angiogenic growth factors tends to be lower in adults with impaired glucose tolerance compared with normal controls and that AEX + WL increased expression of angiogenic growth factors in all participants.

A High Activity Level Is Required for Augmented Muscle Capillarization in Older Women

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 (LVO2) 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 LVO2 was faster (P = 0.008) in VERY compared with SED and MOD. Steady-state LBF and LVO2 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.

The impact of the 24-h movement spectrum on vascular remodeling in older men and women: a review

Aging is associated with increased risk of cardiovascular and cerebrovascular events, which are preceded by early, negative remodeling of the vasculature. Low physical activity is a well-established risk factor associated with the incidence and development of disease. However, recent physical activity literature indicates the importance of considering the 24-h movement spectrum. Therefore, the purpose of this review was to examine the impact of the 24-h movement spectrum, specifically physical activity (aerobic and resistance training), sedentary behavior, and sleep, on cardiovascular and cerebrovascular outcomes in older adults, with a focus on recent evidence (<10 yr) and sex-based considerations. The review identifies that both aerobic training and being physically active (compared with sedentary) are associated with improvements in endothelial function, arterial stiffness, and cerebrovascular function. Additionally, there is evidence of sex-based differences in endothelial function: a blunted improvement in aerobic training in postmenopausal women compared with men. While minimal research has been conducted in older adults, resistance training does not appear to influence arterial stiffness. Poor sleep quantity or quality are associated with both impaired endothelial function and increased arterial stiffness. Finally, the review highlights mechanistic pathways involved in the regulation of vascular and cerebrovascular function, specifically the balance between pro- and antiatherogenic factors, which mediate the relationship between the 24-h movement spectrum and vascular outcomes. Finally, this review proposes future research directions: examining the role of duration and intensity of training, combining aerobic and resistance training, and exploration of sex-based differences in cardiovascular and cerebrovascular outcomes.

Muscle fiber capillarization is associated with various indices of skeletal muscle mass in healthy, older men

INTRODUCTION

Muscle fiber capillarization plays a fundamental role in the regulation of skeletal muscle mass maintenance. However, it remains unclear to what extent capillarization is related to various other skeletal muscle characteristics. In this study we determined whether muscle fiber capillarization is independently associated with measures of skeletal muscle mass, both on a whole-body and cellular level, and post-absorptive muscle protein synthesis rates in healthy older men.

METHODS

Forty-six healthy older (70 ± 4 y) men participated in a trial during which basal muscle protein synthesis rates were assessed using stable isotope tracer methodology. Blood and muscle biopsy samples were collected to assess post-absorptive muscle protein synthesis rates over a 3-hour period. Immunohistochemistry was performed to determine various indices of muscle fiber capillarization, size, type distribution, and myonuclear content/domain size. Dual energy x-ray absorptiometry scans were performed to determine whole-body and appendicular lean tissue mass.

RESULTS

Capillary-to-fiber ratio (C/Fi) and perimeter exchange (CFPE) index correlated with whole-body lean tissue mass (r = 0.43, P < 0.01 and r = 0.25, P < 0.10, respectively), appendicular lean tissue mass (r = 0.52, P < 0.001 and r = 0.37, P < 0.05, respectively) as well as appendicular lean tissue mass divided by body mass index (r = 0.65, P < 0.001 and r = 0.62, P < 0.001, respectively). Muscle fiber size correlated with C/Fi (r = 0.45, P < 0.01), but not with CFPE index. No associations were observed between different indices of muscle fiber capillarization and post-absorptive muscle protein synthesis rates in healthy, older men.

CONCLUSION

The present study provides further evidence that muscle fiber capillarization may be a critical factor in the regulation of skeletal muscle maintenance in healthy older men.

Early time course of change in angiogenic proteins in human skeletal muscle and vascular cells with endurance training

Angiogenic, mitochondrial, and related transcriptional proteins were assessed in human skeletal muscle and isolated vascular cells during the early phase of endurance training. Thigh muscle biopsies were obtained in healthy young subjects, after one acute bout (n = 9) and after 3, 5, 7, and 14 days (n = 9) of cycle ergometer training. Whole muscle homogenates were analyzed for angiogenic, mitochondrial, and regulatory mRNA and protein levels. Angiogenic proteins were determined in muscle-derived endothelial cells and pericytes sorted by fluorescence-activated cell sorting. Acute exercise induced an increase in whole muscle mRNA of peroxisome proliferator-activated receptor gamma coactivator 1α (4.5-fold; P = .002) and vascular endothelial growth factor (VEGF) (2.4-fold; P = .001) at 2 hours post. After 14 days of training, there was an increase in CD31 protein (63%; P = .010) in whole muscle indicating capillary growth. There was also an increase in muscle VEGF receptor 2 (VEGFR2) (1.5-fold; P = .013), in OXPHOS proteins (complex I, II, IV, V; 1.4- to 1.9-fold; P < .05) after 14 days of training and an increase in estrogen-related receptorα protein (1.5-fold; P = .039) at 14 days compared to 5 days of training. Both endothelial cells and pericytes expressed VEGF and other angiogenic factors at the protein level but with a distinctively lower expression of VEGFR2 and thrombospondin-1 (TSP-1) in pericytes. The findings illustrate that initiation of capillary and mitochondrial adaptations occurs within 14 days of training and suggest that sustained changes in angiogenic proteins including VEGF and TSP-1 are moderate in whole muscle and vascular cells.

Pelvic floor muscle training: mechanisms of action for the improvement of genitourinary syndrome of menopause

Objective: This study aims to investigate the mechanism of action of pelvic floor muscle training (PFMT) for the improvement of the signs and symptoms of genitourinary syndrome of menopause (GSM) in postmenopausal women with GSM and urinary incontinence (UI).Methods: Twenty-nine women were included in the secondary analysis of a single-arm feasibility study. Using color Doppler ultrasound, the peak systolic velocity, time-averaged maximum velocity, and pulsatility index of the internal pudendal and dorsal clitoral arteries were measured at rest and after a pelvic floor muscle (PFM) contraction task. PFM function was assessed by dynamometry, and vulvovaginal tissue elasticity was measured using the Vaginal Atrophy Index.Results: PFMT significantly improved blood flow parameters in both arteries (p < 0.05) and significantly increased the speed of PFM relaxation after a contraction (p = 0.003). After the intervention, a marginally significant decrease in PFM tone was observed, as well as an increase in PFM strength (p = 0.060 and p = 0.051, respectively). Finally, improvements in skin elasticity and introitus width were observed as measured by the Vaginal Atrophy Index (p < 0.007).Conclusion: Our findings suggest that PFMT improves blood flow in vulvovaginal tissues, PFM relaxation capacity, and vulvovaginal tissue elasticity in postmenopausal women with GSM and UI.

Impaired skeletal muscle performance as a consequence of random functional capillary rarefaction can be restored with overload-dependent angiogenesis

KEY POINTS

Loss of skeletal muscle capillaries is thought to contribute to a reduction in exercise tolerance, but the relative contribution of a compromised microcirculation with disease, in isolation of co-morbidities, to impaired muscle function is unknown. We therefore developed a novel method to randomly occlude capillaries in the rat hindlimb to mimic the capillary rarefaction observed in many conditions. We demonstrate that muscle fatigue resistance is closely coupled with functional microvascular density, independent of arterial blood flow, while disturbance of the microcirculation leads to long-term impairment of muscle function if left untreated. Mechanical stretch due to muscle overload causes a restoration of fatigue resistance via angiogenic remodelling. These observations highlight the importance of a healthy microcirculation and suggest that restoring impaired microvascular supply, regardless of disease co-morbidities, will assist recovery of exercise tolerance in a variety of conditions that limit quality of life.

ABSTRACT

To what extent microvascular rarefaction contributes to impaired skeletal muscle function remains unknown. Our understanding of whether pathological changes in the microcirculation can be reversed remains limited by a lack of basic physiological data in otherwise healthy tissue. The principal objectives here were to: (1) quantify the effect of random microvascular rarefaction on limb perfusion and muscle performance, and (2) determine if these changes could be reversed. We developed a novel protocol in rats whereby microspheres injected into the femoral artery allowed a unilateral reduction in functional capillary density in the extensor digitorum longus (EDL), and assessed acute and chronic effects on muscle function. Simultaneous bilateral EDL force and hindlimb blood flow measurements were made during electrical stimulation. Following functional capillary rarefaction there was an acute microsphere dose-dependent reduction in muscle fatigue resistance (P < 0.001), despite preserved femoral artery perfusion. Histological analysis of EDL samples taken from injected animals confirmed a positive correlation between the proportion of functional capillaries and fatigue resistance (P = 0.002). Such impaired performance persisted for at least 2 weeks (P = 0.016). Concomitant mechanical overload improved both perfused capillary density and fatigue resistance (P<0.05), confirming that the capacity for muscle remodelling was retained following chronic distributed ischaemia, and that the impact of capillary rarefaction could be alleviated. These results demonstrate that loss of functional capillaries is detrimental to muscle function, even in otherwise healthy tissue, independent of arterial perfusion. Restoration of muscle performance following a mechanical overload stimulus indicates that angiogenic treatments to alleviate microvascular rarefaction may be key to restoring exercise tolerance.

Multivesicular body and exosome pathway responses to acute exercise

NEW FINDINGS

What is the central question of this study? What is the impact of acute aerobic and aerobic + resistance (concurrent) exercise on the regulation of multivesicular body formation in human skeletal muscle? What is the main finding and its importance? Gene expression for proteins associated with multivesicular body biogenesis was increased in response to concurrent exercise, and gene expression of microRNA processing (genetic information) was increased in response to aerobic and concurrent exercise. A greater understanding of the processing of multivesicular bodies in response to acute exercise may lead to novel treatments focused on intercellular communication pathways.

ABSTRACT

Regular aerobic exercise (AEx) and resistance exercise (REx) promote many beneficial adaptations. Skeletal muscle participates in intercellular communication in part through the release of myokines and extracellular vesicles including exosomes (EXOs), the latter containing mRNA, microRNA (miRNA), lipids and proteins. Exercise-induced regulation of skeletal muscle multivesicular body (MVB) biogenesis leading to EXO formation and release is poorly understood. We hypothesized that acute exercise would increase skeletal muscle MVB biogenesis and EXO release pathways with a greater response to aerobic + resistance exercise (A+REx) than to AEx alone. Twelve sedentary, healthy male subjects exercised on a cycle ergometer for 45 min (AEx) followed by single leg, knee extensor, resistance exercise (A+REx). Vastus lateralis biopsies were obtained at rest and 1 h post-exercise. Key components of the MVB biogenesis, EXO biogenesis and release, and miRNA processing pathways were analysed. Clathrin and Alix mRNA (MVB biogenesis) were increased by A+REx, while DICER and exportin mRNA (miRNA processing) were increased by AEx and A+REx. There were positive relationships between MVBs and miRNA processing genes following both AEx and A+REx consistent with coordinated regulation of these interrelated processes (Alix mRNA increased with Drosha, exportin and Dicer mRNA). Acute exercise increases the regulation of components of MVB and EXO pathways as well as miRNA processing components. A greater understanding of the production and packaging of skeletal muscle MVBs, EXOs and mature miRNA could lead to novel treatments focused on intercellular communication.

Reversal of age-associated frailty by controlled physical exercise: The pre-clinical and clinical evidences

Demographic aging is one of the most serious challenges facing our society. Although we live longer, we do not live better because it is considered that approximately 16–20% of our life is spent in late-life morbidity. Older people have the greatest risk of developing frailty increasing the risk of presenting various adverse health events such as low quality of life, disability, hospitalization and even death. Frail men and women over 65 years old have lower muscle quality and muscle mass and higher percentage of body fat than non-frail people of the same age. In this review we will address the main physiological changes in the muscular and nervous system associated to aging. More specifically we will review the changes in muscle mass, quality, and strength relating them with the decrease in capillarization and muscular oxidative capacity as well as with the alterations in protein synthesis in the muscle with aging. The last section of the manuscript will be devoted to the animal models of frailty and the indexes developed to measure frailty in these models. We will finally address the importance of exercise training as an intervention to delay or even reverse frailty.

Ageing impacts phenotypic flexibility in an air-acclimated amphibious fish

The ability to tolerate environmental change may decline as fishes age. We tested the hypothesis that ageing influences the scope for phenotypic flexibility in the mangrove rivulus (Kryptolebias marmoratus), an amphibious fish that transitions between two vastly different environments, water and land. We found that older fish (4-6 years old) exhibited marked signs of ageing; older fish were reproductively senescent, had reduced fin regenerative capacity and body condition, and exhibited atrophy of both oxidative and glycolytic muscle fibers relative to younger adult fish (1-2 years old). However, age did not affect routine O₂ consumption. We then acclimated adult fish (1-6 years) to water (control) or air for 10 days to assess the scope for phenotypic flexibility in response to terrestrial exposure. In support of our hypothesis, we found that older air-acclimated fish had a diminished scope for gill remodeling relative to younger fish. We also found that older fish exhibited poorer terrestrial locomotor performance relative to younger adult fish, particularly when acclimated to air. Our results indicate that ageing diminishes skeletal muscle integrity and locomotor performance of amphibious fishes, and may, therefore, impair terrestrial foraging ability, predator avoidance, or dispersal across the terrestrial environment. Remarkably, older fish voluntarily left water to a similar degree as younger fish despite the age-related deterioration of traits important for terrestrial life.

Low skeletal muscle capillarization limits muscle adaptation to resistance exercise training in older adults

OBJECTIVES

Adequate muscle perfusion supports the transport of nutrients, oxygen and hormones into muscle fibers. Aging is associated with a substantial decrease in skeletal muscle capillarization, fiber size and oxidative capacity, which may be improved with regular physical activity. The aim of this study was to investigate the relationship between muscle capillarization and indices of muscle hypertrophy (i.e. lean mass; fiber cross sectional area (CSA)) in older adults before and after 12 weeks of progressive resistance exercise training (RET).

DESIGN

Interventional study SETTING AND PARTICIPANTS: 19 subjects (10 male and 9 female; 71.1 ± 4.3 years; 27.6 ± 3.2 BMI) were enrolled in the study and performed a whole body RET program for 12 weeks. Subjects where then retrospectively divided into a LOW or HIGH group, based on their pre-RET capillary-to-fiber perimeter exchange index (CFPE). Physical activity level, indices of capillarization (capillaries-to-fiber ratio, C:Fi; CFPE index and capillary-to-fiber interface, LC-PF index), muscle hypertrophy, muscle protein turnover and mitochondrial function were assessed before and after RET.

RESULTS

Basal capillarization (C:Fi; CFPE and LP-CF index) correlates with daily physical activity level (C:Fi, r = 0.57, p = 0.019; CFPE index, r = 0.55, p = 0.024; LC-PF index, r = 0.56, p = 0.022) and CFPE and LC-PF indices were also positively associated with oxidative capacity (respectively r = 0.45, p = 0.06; r = 0.67, p = 0.004). Following RET, subjects in the HIGH group underwent hypertrophy with significant improvements in muscle protein synthesis and muscle fiber CSA (p < 0.05). However, RET did not promote muscle hypertrophy in the LOW group, but RET significantly increased muscle capillary density (p < 0.05).

CONCLUSION/IMPLICATIONS

Muscle fiber capillarization before starting an exercise training program may be predictive of the muscle hypertrophic response to RET in older adults. Increases in muscle fiber size following RET appear to be blunted when muscle capillarization is low, suggesting that an adequate initial capillarization is critical to achieve a meaningful degree of muscle adaptation to RET.

The role of the microcirculation in muscle function and plasticity

It is widely acknowledged that maintenance of muscle, size, strength and endurance is necessary for quality of life and the role that skeletal muscle microcirculation plays in muscle health is becoming increasingly clear. Here we discuss the role that skeletal muscle microcirculation plays in muscle function and plasticity. Besides the density of the capillary network, also the distribution of capillaries is crucial for adequate muscle oxygenation. While capillaries are important for oxygen delivery, the capillary supply to a fibre is related to fibre size rather than oxidative capacity. This link between fibre size and capillary supply is also reflected by the similar time course of hypertrophy and angiogenesis, and the cross-talk between capillaries and satellite cells. A dense vascular network may in fact be more important for a swift repair of muscle damage than the abundance of satellite cells and a lower capillary density may also attenuate the hypertrophic response. Capillary rarefaction does not only occur during ageing, but also during conditions as chronic heart failure, where endothelial apoptosis has been reported to precede muscle atrophy. It has been suggested that capillary rarefaction precedes sarcopenia. If so, stimulation of angiogenesis by for instance endurance training before a hypertrophic stimulus may enhance the hypertrophic response. The microcirculation may thus well be a little-explored target to improve muscle function and the success of rehabilitation programmes during ageing and chronic diseases.

Moderate-intensity aerobic exercise improves skeletal muscle quality in older adults

Sarcopenia, age-associated involuntary loss of muscle and strength, can progress to clinically relevant functional decline. Resistance exercise attenuates muscle and strength loss but may not be feasible for some older adults. Aerobic exercise training (AET) improves cardiopulmonary health; however, effects on protein turnover, muscle mass, and strength are less clear. We aimed to determine whether AET improves basal myofibrillar protein synthesis (MPS) and capillarization, promoting hypertrophy and strength. We hypothesized that AET improves strength with increased MPS and capillarization. Older adults were randomized to non-exercise (NON; n = 11, 71.4 ± 4.18 years) or exercise (EX; n = 12, 73.7 ± 4.05 years). EX completed 24 weeks of AET (walking 3×/week, 45 minutes, 70% heart rate reserve); NON remained sedentary. A stable isotope tracer was infused. MPS and capillarization were analyzed from vastus lateralis muscle biopsies. Strength was measured via isokinetic dynamometry. Lean mass was determined with dual-energy X-ray absorptiometry. Basal MPS increased in EX (+50.7%, P = 0.01) along with capillary density (+66.4%, P = 0.03), peak oxygen consumption (+15.8%, P = 0.01), quadriceps strength (+15.1%, P = 0.01), and muscle quality (peak torque divided by leg lean mass, +15.5%, P = 0.01). Lean mass did not change (P > 0.05). AET increases muscle protein turnover and capillarization in older adults, improving muscle quality.

The Microvasculature and Skeletal Muscle Health in Aging

Aging and aging-related declines in physical activity are associated with physical and metabolic impairments. Skeletal muscle capillarization is reduced in sedentary older adults, may contribute to impairments in skeletal muscle, and is modifiable by exercise training. This article examines the hypothesis that preservation of skeletal muscle capillarization is essential to maintain metabolism, fitness, and function with aging.

Angiogenesis: focusing on the effects of exercise in aging and cancer

[Purpose]

Although it is known that exercise induces angiogenesis, a clear mechanism has remained elusive due to various experimental limitations. This review presents the current status of angiogenesis-related experiments and future directions of experimentation in relation to exercise, aging, and cancer.

[Methods]

We conducted a PubMed search of the available literature to identify reported exercise related changes of angiogenic factors obtained in vitro using C2C12 cells and endothelial cells, and in vivo using animal experiments and in clinical studies.

[Results]

Exercise induced angiogenesis under normal conditions. Aging decreased angiogenic factors and increased during exercise. On the other hand, in cancer, the results indicate that angiogenic factors tend to increase in general, and that the effects of exercise need to be studied more. The exact mechanism remains unclear.

[Conclusion]

The effect of exercise on angiogenesis appears positive. Both resistance and aerobic exercise have positive effects, but many evidences suggest that the effects are more pronounced with aerobic exercise. Further research on the precise mechanism(s) is necessary. It is expected that these studies will include models of aging and cancer.

The Effect of Nordic Walking Training Combined with Vitamin D Supplementation on Postural Control and Muscle Strength in Elderly People-A Randomized Controlled Trial

Nordic Walking (NW) and Vitamin D concentration (Vit D) alone have been shown to contribute to the health and performance of elderly people. However, the interaction between these two factors has yet to be explored. In this study 42 women over 60 years of age (69.02 ± 5.56 years) were recruited and divided in two NW groups: a high-intensity interval training group (HI-NW) and a moderate-intensity continuous training group (MI-NW). Individuals from each group completed a 12-week NW training program (3 times a week/2 hours) combined with randomized Vitamin D supplementation (HD = high dose: 4000 IU/day or LD = low dose: 800 IU/day). Body composition, postural control, muscle strength and Vitamin D serum concentration were measured twice; before and after the intervention. To investigate the interaction between supplementation and training a mixed-design analysis of variance (ANOVA) was performed. The HI-NW group, regardless of supplementation dose, increased their Vit D and elbow torque performance. On the other hand, in the MI-NW group the same Vit D outcome was seen only with HD supplementation and was also associated with increased leg muscle mass. In conclusion, beneficial effects of both HI-NW and MI-NW training regimes were seen. The impact of the dose supplementation on Vit D and body composition was related to the type of NW training.

Daily muscle stretching enhances blood flow, endothelial function, capillarity, vascular volume and connectivity in aged skeletal muscle

KEY POINTS

In aged rats, daily muscle stretching increases blood flow to skeletal muscle during exercise. Daily muscle stretching enhanced endothelium-dependent vasodilatation of skeletal muscle resistance arterioles of aged rats. Angiogenic markers and capillarity increased in response to daily stretching in muscles of aged rats. Muscle stretching performed with a splint could provide a feasible means of improving muscle blood flow and function in elderly patients who cannot perform regular aerobic exercise.

ABSTRACT

Mechanical stretch stimuli alter the morphology and function of cultured endothelial cells; however, little is known about the effects of daily muscle stretching on adaptations of endothelial function and muscle blood flow. The present study aimed to determine the effects of daily muscle stretching on endothelium-dependent vasodilatation and muscle blood flow in aged rats. The lower hindlimb muscles of aged Fischer rats were passively stretched by placing an ankle dorsiflexion splint for 30 min day^-1 , 5 days week^-1 , for 4 weeks. Blood flow to the stretched limb and the non-stretched contralateral limb was determined at rest and during treadmill exercise. Endothelium-dependent/independent vasodilatation was evaluated in soleus muscle arterioles. Levels of hypoxia-induced factor-1α, vascular endothelial growth factor A and neuronal nitric oxide synthase were determined in soleus muscle fibres. Levels of endothelial nitric oxide synthase and superoxide dismutase were determined in soleus muscle arterioles, and microvascular volume and capillarity were evaluated by microcomputed tomography and lectin staining, respectively. During exercise, blood flow to plantar flexor muscles was significantly higher in the stretched limb. Endothelium-dependent vasodilatation was enhanced in arterioles from the soleus muscle from the stretched limb. Microvascular volume, number of capillaries per muscle fibre, and levels of hypoxia-induced factor-1α, vascular endothelial growth factor and endothelial nitric oxide synthase were significantly higher in the stretched limb. These results indicate that daily passive stretching of muscle enhances endothelium-dependent vasodilatation and induces angiogenesis. These microvascular adaptations may contribute to increased muscle blood flow during exercise in muscles that have undergone daily passive stretch.

The Necessity of Active Muscle Metabolism for Healthy Aging: Muscular Activity Throughout the Entire Day

There is more need for "a movement-movement" than ever before. The percentage of seniors in our population is rising exponentially. Sedentary lifestyles throughout the lifespan have become the norm, including inactive youth and a sedentary workforce. Preventable chronic diseases caused by sedentary living have both lowered the quality of life for those directly affected or their families, and have created an unsustainable economic dilemma. In this article, we explain that whether it is a sedentary student, worker, or retiree, the most neglected but essential facts are as follows. By far, the most potent and rapid way to raise the rate of healthy metabolic and cardiovascular processes is through the immediate benefits of muscle contractions. Working muscle demands more energy and fuel than any other tissue in the body, but during inactivity the metabolic rate of muscle is relatively low. Depending on the type of contraction, muscle type, and other factors, the local fuel requirements within the working muscle can help to manage metabolic risks through a variety of processes, such as blood glucose utilization, uptake of unhealthy blood triglycerides, and increased blood flow. Given the large amount of time that people spend inactive each day, there is an enormous opportunity to raise the bar in optimizing health throughout the entire lifespan. Developed correctly, safe and low effort muscular activity can be performed for relatively long periods of time each day by the elderly and all segments of the population to optimize health and well being during aging.

Exercise intensity modulates the appearance of circulating microvesicles with proangiogenic potential upon endothelial cells

The effect of endurance exercise on circulating microvesicle dynamics and their impact on surrounding endothelial cells is unclear. Here we tested the hypothesis that exercise intensity modulates the time course of platelet (PMV) and endothelial-derived (EMV) microvesicle appearance in the circulation through hemodynamic and biochemical-related mechanisms, and that microvesicles formed during exercise would stimulate endothelial angiogenesis in vitro. Nine healthy young men had venous blood samples taken before, during, and throughout the recovery period after 1 h of moderate [46 ± 2% maximal oxygen uptake (V̇o_2max)] or heavy (67 ± 2% V̇o_2max) intensity semirecumbent cycling and a time-matched resting control trial. In vitro experiments were performed by incubating endothelial cells with rest and exercise-derived microvesicles to examine their effects on cell angiogenic capacities. PMVs (CD41⁺) increased from baseline only during heavy exercise (from 21 ± 1 × 10³ to 55 ± 8 × 10³ and 48 ± 6 × 10³ PMV/μl at 30 and 60 min, respectively; P < 0.05), returning to baseline early in postexercise recovery (P > 0.05), whereas EMVs (CD62E⁺) were unchanged (P > 0.05). PMVs were related to brachial artery shear rate (r² = 0.43) and plasma norepinephrine concentrations (r² = 0.21) during exercise (P < 0.05). Exercise-derived microvesicles enhanced endothelial proliferation, migration, and tubule formation compared with rest microvesicles (P < 0.05). These results demonstrate substantial increases in circulating PMVs during heavy exercise and that exercise-derived microvesicles stimulate human endothelial cells by enhancing angiogenesis and proliferation. This involvement of microvesicles may be considered a novel mechanism through which exercise mediates vascular healing and adaptation.