Molecular predictors of resistance training outcomes in young untrained female adults

• Published in: Journal of applied physiology (1985) 2023-03, Vol.134 (3), p.491
• Main Authors: Smith, Morgan A, Sexton, Casey L, Smith, Kristen A, Osburn, Shelby C, Godwin, Joshua S, Beausejour, Jonathan P, Ruple, Bradley A, Goodlett, Michael D, Edison, Joseph L, Fruge, Andrew D, Robinson, Austin T, Gladden, L Bruce, Young, Kaelin C, Roberts, Michael D
• Format: Article
• Language: English
• Subjects: Abundance; Adaptation; Biopsy; Body composition; Cell number; Cells (biology); Females; Muscles; Physical training; Quartiles; Resistance training; Satellite cells; Soft tissues; Strength testing; Strength training; Training
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00605.20221

We sought to determine if the myofibrillar protein synthetic (MyoPS) response to a naïve resistance exercise (RE) bout, or chronic changes in satellite cell number and muscle ribosome content, were associated with hypertrophic outcomes in females or differed in those who classified as higher (HR) or lower (LR) responders to resistance training (RT). Thirty-four untrained college-aged females (23.4 ± 3.4 kg/m2) completed a 10-wk RT protocol (twice weekly). Body composition and leg imaging assessments, a right leg vastus lateralis biopsy, and strength testing occurred before and following the intervention. A composite score, which included changes in whole body lean/soft tissue mass (LSTM), vastus lateralis (VL) muscle cross-sectional area (mCSA), midthigh mCSA, and deadlift strength, was used to delineate upper and lower HR (n = 8) and LR (n = 8) quartiles. In all participants, training significantly (P < 0.05) increased LSTM, VL mCSA, midthigh mCSA, deadlift strength, mean muscle fiber cross-sectional area, satellite cell abundance, and myonuclear number. Increases in LSTM (P < 0.001), VL mCSA (P < 0.001), midthigh mCSA (P < 0.001), and deadlift strength (P = 0.001) were greater in HR vs. LR. The first-bout 24-hour MyoPS response was similar between HR and LR (P = 0.367). While no significant responder × time interaction existed for muscle total RNA concentrations (i.e., ribosome content) (P = 0.888), satellite cell abundance increased in HR (P = 0.026) but not LR (P = 0.628). Pretraining LSTM (P = 0.010), VL mCSA (P = 0.028), and midthigh mCSA (P < 0.001) were also greater in HR vs. LR. Female participants with an enhanced satellite cell response to RT, and more muscle mass before RT, exhibited favorable resistance training adaptations.