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Background: The stimulation of muscle protein synthesis (MPS) by dietary protein is reduced with age. We hypothesized that twice-daily milk consumption would increase daily rates of MPS in older women relative to a nondairy milk alternative and that MPS would be enhanced by increased physical activity (PA).Methods: Twenty-two older women were randomly assigned to 1 of 3 experimental groups: whole milk (WM; n = 7, 69 ± 3 y), skim milk (SM; n = 7, 68 ± 3 y), or an almond beverage (AB; n = 8, 63 ± 3 y). From days 1 to 3, participants consumed a standardized diet (0.8 g protein⋅kg-1 ⋅d-1) and performed their habitual PA (Phase 1, Baseline). From days 4 to 6, participants continued to perform habitual PA, but consumed an intervention diet consisting of the standardized diet plus twice-daily beverages (250 mL each) of either WM, SM, or AB (Phase 2, Diet Intervention). Finally, from days 7 to 9, the intervention diet was consumed, and PA via daily steps was increased to ∼150% of habitual daily steps (Phase 3, Intervention Diet + PA). Deuterated water was ingested throughout the study, and muscle biopsies were taken on days 1, 4, 7, and 10 to measure MPS.Results: Daily MPS rates were not differentially affected by the addition of WM, SM, or AB to a standardized diet. There was, however, a significant effect of study phase such that, when collapsed across conditions, MPS was significantly increased from Phase 1 to Phase 2 (+0.133%⋅d-1; 95% CI: 0.035-0.231; P < 0.01) and further increased from Phase 2 to Phase 3 (+0.156%⋅d-1; 95% CI: 0.063-0.250; P < 0.01).Conclusions: Increasing PA through walking was sufficient to increase daily MPS rates in older women, irrespective of whether dietary protein intake is increased beyond the recommended intake of 0.8 g⋅kg-1 ⋅d-1. The trial was registered at clinicaltrials.gov as NCT04981652. [ABSTRACT FROM AUTHOR]

The article discusses the effect of beta-hydroxy beta-methylbutyrate (HMB) supplementation on body fitness, composition, muscle damage indices and hormonal profile. Pathways for HMB's mode of action are inhibition of protein degradation via proteasones, enhancement of sarcolemmal integrity via cytosolic cholesterol and increased protein synthesis via the mammalian target of rapamycin (mTOR) pathway. Also discussed are hormonal interactions, HMB dosage and safety issues.

In contrast to the effect of nutritional intervention on postexercise muscle protein synthesis, little is known about the potential to modulate protein synthesis during exercise. This study investigates the effect of protein coingestion with carbohydrate on muscle protein synthesis during resistance-type exercise, Ten healthy males were studied in the evening after they consumed a standardized diet throughout the day. Subjects participated in two experiments in which they ingested either carbohydrate or carbohydrate with protein during a 2-h resistance exercise session. Subjects received a bolus of test drink before and every 15 mm during exercise, providing 0.15 g∙ kg-1∙h-1 carbohydrate with (CHO + PRO) or without (CHO) 0.15 g∙ kg-1∙h-1 protein hydrolysate. Continuous intravenous infusions with L-[ring-13C6]phenylalanine and L-[ring-2H2]tyrosine were applied, and blood and muscle biopsies were collected to assess whole body and muscle protein synthesis rates during exercise. Protein coingestion lowered whole body protein breakdown rates by 8.4 ± 3.6% (P = 0.066), compared with the ingestion of carbohydrate only, and augmented protein oxidation and synthesis rates by 77 ± 17 and 33 ± 3%, respectively (P < 0.01). As a consequence, whole body net protein balance was negative in CHO, whereas a positive net balance was achieved after the CHO + PRO treatment (-4.4 ± 0.3 vs. 16.3 ± 0.4 μmol phenylalanine∙kg-1∙h-1 respectively; P < 0.01). In accordance, mixed muscle protein fractional synthetic rate was 49 ± 22% higher after protein coingestion (0.088 ± 0.012 and 0.060 ± 0.004%/h in CHO + PRO vs. CHO treatment, respectively; P < 0.05). We conclude that, even in a fed state, protein coingestion stimulates whole body and muscle protein synthesis rates during resistance-type exercise. [ABSTRACT FROM AUTHOR]