This Is AuburnElectronic Theses and Dissertations

Molecular predictors of the hypertrophy response to resistance training in young untrained female adults




Smith, Morgan

Type of Degree

PhD Dissertation




We determined 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, varied in females that classified as higher (HR) or lower (LR) responders following resistance training (RT). Thirty-four untrained college-aged females completed a 10-week full-body RT protocol (twice weekly). Body composition, right leg muscle imaging, a right leg vastus lateralis biopsy, and strength testing occurred prior to and following the intervention. A composite pre-to-post change score consisting of four variables was used to define HR (n=8) and LR (n=8): i) whole body lean/soft tissue mass (LSTM), ii) VL muscle cross-sectional area (CSA), iii) mid-thigh muscle cross-sectional area (mCSA), and iv) maximal deadlift strength. For all participants, training increased LSTM (+1.1±1.1 kg, p<0.001), VL CSA (+2.7±2.7 cm2, p<0.001), mid-thigh mCSA (+8.9±7.0 cm2, p<0.001), deadlift strength (24±13 kg, p<0.001), mean muscle fiber cross-sectional area (+759±1198 µm2, p=0.001), satellite cell number (+0.026±0.061 cells/fiber, p=0.025), and myonuclear number (+0.29±0.37 nuclei/fiber, p=0.013). HR exhibited superior training responses to LR in LSTM (2.2±0.7 kg versus 0.3±0.6 kg, respectively, p < 0.001), VL CSA (5.9±2.5 cm2 versus 0.6±0.8 cm2, p<0.001), mid-thigh mCSA (16.0±6.2 cm2 versus 3.2±2.9 cm2, p<0.001), and deadlift strength (37±15 kg versus 13±7 kg, p=0.001). The 24-hour MyoPS response to the first RE bout was not different between HR and LR (p=0.367). A significant group*time interaction was found for satellite cell number after RT (p=0.025), but not muscle ribosome content (p=0.888). Specifically, satellite cell number increased in HR (p=0.026), but not LR (p=0.628). Pre-training values multiple variables were also greater in HR versus LR: i) LSTM (44.2±3.3 kg versus 39.2±3.5 kg, p=0.010), ii) VL CSA (20.1±2.2 cm2 versus 17.6±1.9 cm2, p<0.028), and iii) mid-thigh mCSA (117±8 cm2 versus 99 ± 6 cm2, p<0.001). Fat mass prior to RT, sleep duration, energy intake, body mass-normalized training volume, and menstrual cycle days at pre- and post-data collections were not significantly different between response groups. These data suggest that untrained female participants with an enhanced satellite cell response to RT, and more muscle mass prior to RT, exhibit more favorable RT adaptations.