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Very little is known about the energy needs of young athletes. Recent studies using the doubly labeled water method have shown that the recommended dietary allowances for energy may be too high for normally active children and adolescents living in affluent societies. No studies of energy balance in young athletes have been published. Self-report dietary records of young athletes indicate that energy, carbohydrate, and select micronutrient intakes of certain athletic groups and individual athletes may be marginal or inadequate. Potential consequences of inadequate energy and nutrient intakes in young athletes include poor bone health, fatigue, limited recovery from injuries, menstrual dysfunction in female athletes, and poor performance. Studies of energy balance and nutrient status in young athletes are needed to better understand the nutritional needs of this group.

There is limited evidence examining the association between physical activity (PA), sedentary time (ST), frailty, and factors influencing PA behaviors in migrant older women from ethnically diverse backgrounds. The aims of this mixed-methods study were to: 1) examine PA levels and ST across frailty status; 2) identify any differences in PA/ST between ethnic and religious groups; and 3) qualitatively explore factors influencing PA among older (≥60 years) migrant women (n = 60). PA/ST were assessed using accelerometry and frailty status using the frailty phenotype. Key factors influencing PA were explored via semi-structured interviews (n = 36) and analyzed using thematic analysis. Participants were highly sedentary irrespective of frailty status. Moderate-to-vigorous-physical activity (MVPA) was independently associated with frailty. Participants spent 69% of waking time in ST, with only 15% meeting current weekly PA recommendations. Health-related and socio-cultural factors were reported as common barriers to achieving PA recommendations. Maintaining independence, preventing physical decline and depression were key factors promoting PA. Understanding the challenges and needs of this population can help to inform strategies to promote PA and thus optimize physical function.

Studies examining the effects of diet (D) and diet-plus-exercise (DE) programs on resting metabolic rate (RMR) report equivocal results. The purpose of this study was to use meta-analysis to determine if exercise prevents the decrease in RMR observed with dieting. Results from the 22 studies included in this analysis revealed that the majority of studies used female subjects ages 31-45 years, who were fed a relatively low-fat, high-carbohydrate diet of less than 5,023 kJ · day¹. The predominant prescribed exercise was aerobic in nature, 31-60 min in duration, performed 4-5 days per week, and of moderate intensity (51-70% of ${\text{VO}}_{2\max }$ ). Contrary to what is reported in narrative reviews, RMR decreased significantly with both D and DE programs, and the drop with D was significantly greater than that with DE. In conclusion, the addition of exercise to dietary restriction appears to prevent some of the decrease in RMR observed in premenopausal women.

An activity deficit hypothesis was posited that children with movement difficulties are less physically active during recess than age- and gender-matched controls without movement difficulties. Criteria used in identifying children with movement difficulties were (a) a score of at least 4 on the Test of Motor Impairment, (b) regular physical education student, and (c) age 80 to 109 months. An observational study was conducted over a 2-month period in recess settings with 52 subjects. Findings revealed that during recess time, children with movement difficulties were vigorously active less often, played less often with large playground equipment, were not observable for significantly more time, and spent less time in positive social interactions with others of their own gender. Accordingly, it was concluded that the data support the activity deficit hypothesis.

The relationship of objectively measured sedentary time (ST), frequency of breaks in ST, and lower extremity function (LEF) was investigated in a diverse sample aged ≥ 70 years (n = 217). Physical activity (PA) was assessed by accelerometry deriving moderate-vigorous PA (MVPA) minutes per registered hour (MVPA min · hr⁻¹), registered ST (ST min · hr⁻¹), and breaks in ST min · hr⁻¹ (breaks · hr⁻¹). LEF was assessed by the Short Physical Performance Battery. Univariate associations with overall LEF were MVPA (r = .523), ST (r = −.499), and breaks (r = .389). Adjusted linear regression including MVPA min · hr⁻¹, ST min · hr⁻¹, and breaks · hr⁻¹ explained 41.5% of LEF variance. Each additional break · hr⁻¹ was associated with 0.58 point increase in LEF. Breaks and MVPA had strongest independent associations with LEF. Promoting regular breaks might be useful in maintaining or increasing LEF and later life independence. This novel finding is important for the design of effective lifestyle interventions targeting older adults.

The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical activity (BASAL). This was followed by a 7-day exercise period of volume-matched, LF (10 × 10 repetitions at 70% one-repetition maximum, once per week) or HF (2 × 10 repetitions at ∼70% one-repetition maximum, five times per week) resistance exercise training. The participants had one leg randomly allocated to LF and the other to HF. Skeletal muscle biopsies and daily saliva samples were collected to determine myofibrillar protein synthesis rates using ²H₂O, with intracellular signaling determined using Western blotting. The myofibrillar protein synthesis rates did not differ between the LF (1.46 ± 0.26%/day) and HF (1.48 ± 0.33%/day) conditions over the 7-day exercise training period (p > .05). There were no significant differences between the LF and HF conditions over the first 2 days (1.45 ± 0.41%/day vs. 1.25 ± 0.46%/day) or last 5 days (1.47 ± 0.30%/day vs. 1.50 ± 0.41%/day) of the exercise training period (p > .05). Daily myofibrillar protein synthesis rates were not different from BASAL at any time point during LF or HF (p > .05). The phosphorylation status and total protein content of selected proteins implicated in skeletal muscle ribosomal biogenesis were not different between conditions (p > .05). Under the conditions of the present study, resistance exercise training frequency did not modulate daily myofibrillar protein synthesis rates in young men.