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Resistance training induces skeletal muscle hypertrophy via the summated effects of postexercise elevations in myofibrillar protein synthesis (MyoPS) that persist for up to 48 h, although research in females is currently lacking. MyoPS is regulated by mTOR translocation and colocalization; however, the effects of resistance training on these intracellular processes are unknown. We hypothesized that MyoPS would correlate with hypertrophy only after training in both sexes and would be associated with intracellular redistribution of mTOR.Recreationally active males and females (n = 10 each) underwent 8 wk of whole-body resistance exercise three times a week. Fasted muscle biopsies were obtained immediately before (REST) and 24 and 48 h after acute resistance exercise in the untrained (UT) and trained (T) states to determine integrated MyoPS over 48 h (D2O ingestion) and intracellular mTOR colocalization (immunofluorescence microscopy).Training increased (P0.01) muscle strength (~20%-126%), muscle thickness (~8%-11%), and average fiber cross-sectional area (~15%-20%). MyoPS increased above REST in UT (P = 0.032) and T (P0.01), but to a greater extent in males (~23%; P = 0.023), and was positively (P0.01) associated with muscle thickness and fiber cross-sectional area at T only in both males and females. mTOR colocalization with the cell periphery increased (P0.01) in T, irrespective of sex or acute exercise. Training increased (P ≤ 0.043) total mTOR, LAMP2 (lysosomal marker), and their colocalization (P0.01), although their colocalization was greater in males at 24 and 48 h independent of training status (P0.01).MyoPS during prolonged recovery from exercise is greater in males but related to muscle hypertrophy regardless of sex only in the trained state, which may be underpinned by altered mTOR localization.

Home-based resistance exercise (RE) has become increasingly prevalent, but its effects on protein metabolism are understudied. We tested the effect of an essential amino acid formulation (EAA+: 9 g EAAs, 3 g leucine) and branched-chain amino acids (BCAAs: 6 g BCAAs, 3 g leucine), relative to a carbohydrate (CHO) placebo, on exogenous leucine retention and myofibrillar protein breakdown following dynamic bodyweight RE in a home-based setting. Twelve recreationally active adults (nine male, three female) participated in a double-blind, placebo-controlled, crossover study with four trial conditions: (i) RE and EAA+ (EX-EAA+); (ii) RE and BCAAs (EX-BCAA); (iii) RE and CHO placebo (EX-CHO); and (iv) rest and CHO placebo (REST-CHO). Total exogenous leucine oxidation and retention (estimates of whole-body anabolism) and urinary 3-methylhistidine:creatinine ratio (3MH:Cr; estimate of muscle catabolism) were assessed over 5 h post-supplement. Total exogenous leucine oxidation and retention in EX-EAA+ and EX-BCAA did not significantly differ (p = 0.116) but were greater than EX-CHO (p < 0.01). There was a main effect of condition on urinary 3MH:Cr (p = 0.034), with post hoc analysis revealing a trend (p = 0.096) for reduced urinary 3MH:Cr with EX-EAA+ (32%) compared to EX-CHO. By direct comparison, urinary 3MH:Cr was significantly lower (23%) in EX-EAA+ than EX-BCAA (p = 0.026). In summary, the ingestion of EAA+ or BCAA provided leucine that was ~60% retained for protein synthesis following home-based bodyweight RE, but EAA+ most effectively attenuated myofibrillar protein breakdown.

There are limited tools to measure anabolic sensitivity non-invasively in response to acute physiological stimuli, which represents a challenge for research in free-living settings and vulnerable populations. We tested the ability of a stable isotope breath test to detect changes in leucine oxidation (OX) and leucine retention (intake-OX) across a range of anabolic sensitivities. Healthy males ingested a beverage containing 0.25 g·kg

A wide variety of analytical techniques have been employed for monitoring chemical reactions, with online instrumentation providing additional benefits compared to offline analysis. A challenge in the past for online monitoring has been placement of the monitoring instrumentation as close as possible to the reaction vessel to maximize sampling temporal resolution and preserve sample composition integrity. Furthermore, the ability to sample very small volumes from bench-scale reactions allows the use of small reaction vessels and conservation of expensive reagents. In this study, a compact capillary LC instrument was used for online monitoring of as small as 1 mL total volume of a chemical reaction mixture, with automated sampling of nL-scale volumes directly from the reaction vessel used for analysis. Analyses to demonstrate short term (~2 h) and long term (~ 50 h) reactions were conducted using tandem on-capillary ultraviolet absorbance followed by in-line MS detection or ultraviolet absorbance detection alone, respectively. For both short term and long term reactions (10 and 250 injections, respectively), sampling approaches using syringe pumps minimized the overall sample loss to ~0.2% of the total reaction volume.