Vitamin D is lipophilic and accumulates substantially in adipose tissue. Even without supplementation, the amount of vitamin D in the adipose of a typical adult is equivalent to several months of the daily reference nutrient intake (RNI). Paradoxically, despite the large amounts of vitamin D located in adipose tissue, individuals with obesity are often vitamin D deficient according to consensus measures of vitamin D status (serum 25‐hydroxyvitamin D concentrations). Thus, it appears that vitamin D can become ‘trapped’ in adipose tissue, potentially due to insufficient lipolytic stimulation and/or due to tissue dysfunction/adaptation resulting from adipose expansion. Emerging evidence suggests that exercise may mobilise vitamin D from adipose (even in the absence of weight loss). If exercise helps to mobilise vitamin D from adipose tissue, then this could have important ramifications for practitioners and policymakers regarding the management of low circulating levels of vitamin D, as well as chronically low levels of physical activity, obesity and associated health conditions. This perspective led us to design a study to examine the impact of exercise on vitamin D status, vitamin D turnover and adipose tissue vitamin D content (the VitaDEx project). The VitaDEx project will determine whether increasing physical activity (via exercise) represents a potentially useful strategy to mobilise vitamin D from adipose tissue.

Loss of muscle mass and strength are seemingly accepted as part of the ageing process, despite ultimately leading to the loss of independence. Resistance exercise is considered to be primary defence against loss of muscle function in older age, but it typically requires access to exercise equipment often in a gym environment. This pilot study aimed at examining the effect of a 28-day, unsupervised home-based exercise intervention on indices of leg strength and muscle size in healthy older adults. Twenty participants were randomly assigned to either maintain their habitual physical activity levels (Control; n=10; age, 74 (5) years; body mass, 26.3 (3.5) kg/m2) or undertake “exercise snacks” twice daily (ES; n=10; age, 70 (4) years; body mass, 25.0 (3.4) kg/m2). Both groups consumed 150 g of yogurt at their breakfast meal for the duration of the intervention. Sixty-second sit-to-stand score improved by 31% in ES, with no change in Control (p < 0.01). Large effect sizes were observed for the difference in change scores between the groups for interpolated maximum leg pressing power (6% increase in ES) and thigh muscle cross-sectional area (2% increase in ES). The present pilot data suggest that exercise snacking might be a promising strategy to improve leg muscle function and size in older adults and that further investigation into zero-cost exercise strategies that allow high frequency of training is warranted.

The purpose of this study was to examine the feasibility and acceptability of remotely delivered, home-based exercise programs on physical function and well-being in self-isolating older adults during the COVID-19 pandemic. In a four-arm randomized controlled trial, 63 participants (aged 65 years and older) were allocated to one of three home-based daily (2 × 10-min) exercise interventions (exercise snacking, tai chi snacking, and combination) or control (UK National Health Service Web pages). Functional assessments were conducted via video call at baseline and 4-week follow-up. A web-based survey assessed the acceptability of each exercise program and secondary psychological/well-being outcomes. Ecological momentary assessment data, collected in Weeks 1 and 4, explored feeling states as antecedents and consequences of exercise. All intervention groups saw increased physical function at follow-up and displayed good adherence with exercise snacking considered the most acceptable program. Multilevel models revealed reciprocal associations between feelings of energy and exercise engagement. Further studies are needed with larger, more diverse demographic samples.

Skeletal muscle mass is in a constant state of turnover, and atrophy is the result of a shift in the balance of muscle protein synthesis and breakdown resulting in net muscle protein loss. Total disuse of skeletal muscle quickly leads to muscle atrophy and loss of strength, and this has been repeatedly demonstrated in studies employing bed rest and lower limb immobilisation methodologies in young healthy participants. Fewer studies have focused on older participants (>65 years of age), but those that have provide evidence that advancing age brings increased vulnerability to rapid and marked loss of muscle size and strength during period of total muscle unloading. Increased systemic inflammation and reduced protein synthetic responses to protein feeding and muscle contraction might influence the severity of muscle protein loss during periods of total unloading compared with younger individuals. Less extreme reductions in muscle loading (e.g., 2 weeks of reducing daily ambulation to <1500 steps/day) have also been shown to result in decreases in muscle mass. This step-reduction model may be more relevant than total bed rest or limb immobilisation for examining real-world scenarios that present a physiological challenge to the maintenance of skeletal muscle mass in older individuals.

Physical activity is considered crucial in attenuating losses in strength and power associated with ageing. However, in well-functioning, active older adults the relationship between habitual physical activity and muscle function is surprisingly unclear. Leg press velocity, force, and power, were compared between 50 older and 30 younger healthy individuals, and associations with habitual physical activity explored. An incremental power test was performed on a pneumatic leg press, with theoretical maximum velocity, force, and power calculated. Vastus lateralis muscle thickness was measured by ultrasound, and participants wore a combined accelerometer and heart rate monitor for 6-days of free-living. Older individuals produced lower absolute maximum velocity, force, and power, than younger individuals. When accounting for smaller muscle size, older individual’s maximum force and power remained markedly lower. Both groups were active, however using age specific thresholds for classifying physical activity, the older individuals engaged in twice the amount of moderate-to-vigorous physical activity in comparison to the younger individuals. There were no associations between any characteristics of muscle function and physical activity. These data support that the ability to generate force and power deteriorates with age, however habitual physical activity levels do not explain inter-individual differences in muscle function in active older individuals.

The aim of this study was to determine the effect of aging on power generation and joint coordination during a leg press, in order to increase understanding of how functional movements are affected during the aging process. 44 older and 24 younger adults performed eight sub-maximal power repetitions on a seated leg press dynamometer. Peak power and velocity (at 40% maximum resistance) were measured along with the coordination (coupling angle) of the lower limb joints using the vector coding technique. The younger adults produced significantly greater peak power than the older adults (mean ± SD; 762 W ± 245 vs 361 W ± 162, p < 0.01) and at higher peak velocities (mean ± SD; 1.37 m/s ± 0.05 vs 1.00 m/s ± 0.06, p < 0.01). The older adults produced less consistent values of peak power than younger adults, evidenced by a higher coefficient of variation (mean ± SD; 7.6% ± 5.2 vs 5.0% ± 3.0, p < 0.01), however, there was significantly less variability in the coupling angles displayed by the older adults compared to the younger adults (mean ± SD; 2.0° ± 1.1 vs 3.5° ± 2.7, p < 0.01 (ankle-knee); 1.7° ± 0.6 vs 4.1° ± 3.0, p < 0.01 (knee-hip)). The results of this study demonstrate that older adults display higher outcome variability but lower variability in technique (coordination). The more rigid movement strategies displayed by the older adults potentially reflects an increased risk of overuse injury due to repetitive demands on the same structures, or the reduced ability to respond to unexpected situations due to a lack of flexibility in joint control.

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BackgroundMuscles get smaller and weaker as we age and become more vulnerable to atrophy when physical activity is reduced or removed. This research is designed to investigate the potentially protective effects of two separate exercise strategies against loss in skeletal muscle function and size, and other key indices of health, following 14 days of reduced physical activity in older men.MethodsThree groups of 10 older men (aged 65–80 years) will undertake 2 weeks of reduced activity by decreasing daily steps from more than 3500 to less than 1500 (using pedometers to record step count). Two of the three groups will then undertake additional exercise interventions, either: 4 weeks of progressive resistance training prior to the step-reduction intervention (PT-group), or home-based ‘exercise snacking’ three times per day during the step-reduction intervention (ES-group). The third group undertaking only the step-reduction intervention (control) will provide a comparison against which to assess the effectiveness of the protective exercise strategies. Pre and post step-reduction assessments of muscle function, standing balance, anthropometry and muscle architecture will be taken. Pre and post step-reduction in postprandial metabolic control, resting systemic inflammation, adipose inflammation, oxidative stress, immune function, sleep quality, dietary habits, and quality of life will be measured. The stress response to exercise, and signalling protein and gene expression for muscle protein synthesis and breakdown following an acute bout of exercise will also be assessed pre and post step-reduction. Rates of muscle protein synthesis and adipose triglyceride turnover during the step-reduction intervention will be measured using stable isotope methodology. All participants will then undertake 2 weeks of supervised resistance training with the aim of regaining any deficit from baseline in muscle function and size.DiscussionThis study aims to identify exercise strategies that could be implemented to protect against loss of muscle power during 2 weeks of reduced activity in older men, and to improve understanding of the way in which a short-term reduction in physical activity impacts upon muscle function and health.Trial registrationClinicalTrials.gov: NCT02495727 (Initial registration: 25 June 2015)