Impact of Resistance Training on Markers of Oxidative Stress and Proteostasis in Skeletal Muscle in Middle-Aged Untrained Adults

PURPOSE: To determine whether 8 weeks of unilateral leg extensor training, which elicited modest vastus lateralis skeletal muscle hypertrophy, influences the expression of markers associated with ROS, antioxidant defense, protein breakdown, chaperone activity, and stress response/autophagy in middle-aged adults. Moreover, we compared pre- and post-training outcomes to younger, healthy participants. HYPOTHESIS: Differences in assayed markers will exist between younger-untrained versus middle-aged individuals prior to and following training. METHODS: We investigated the effects of unilateral leg extensor resistance training (2 days/week for 8 weeks) on protein markers in apparently healthy middle-aged participants (MA; 56 ± 8 years, 13 females, 3 males) and compared pre- and post-intervention values to a group of young participants (Y; 21 ± 3 years, 9 females, 5 males) to determine rejuvenation effects. Vastus lateralis muscle biopsies were collected, and relative protein expression was analyzed using Western blotting, with expression values normalized to those of the young group. Independent and dependent samples t-tests were conducted to compare protein expression levels between two groups, with statistical significance set at α = 0.05. DATA: Resistance training significantly increased 4-HNE ( p = 0.0018, +25.1%), SOD1 ( p = 0.0003, +53.0%), Calpain-1 ( p = 0.0074, +58.6%), HSP60 ( p = 0.0052, +34.5%), and HSP90 ( p = 0.0581, +69.1%) in middle-aged participants. Post-training levels of SOD1 ( p = 0.0112, +43.5%), Calpain-1 ( p =.0008, +83.2%), Calpain-2 ( p < 0.001, +102.1%), HSP60 ( p = 0.0453, +63.8%), and HSP90 ( p = 0.0018, +155.8%) were significantly higher compared to young untrained participants. In contrast, 20S proteasome levels non-significantly decreased post-training ( p = 0.2599, −42.5%) and remained significantly lower than the younger group ( p = 0.0034 ). SUMARY OF RESULTS: Resistance training in middle-aged adults led to significant changes in pathways related to oxidative stress, proteolysis, and chaperone activity. Oxidative stress markers increased, as indicated by elevated 4-HNE levels and SOD1. Proteolytic activity showed significant increases in Calpain-1 and Calpain-2, while 20S proteasome levels declined relative to younger participants. Chaperone defense pathways were upregulated, with higher post-training levels of HSP60 and HSP90. Compared to young untrained participants, middle-aged adults exhibited significantly higher post-training levels of SOD1, Calpain-1, Calpain-2, HSP60, and HSP90. CONCLUSION: Resistance training in middle-aged adults led to significant changes in pathways related to oxidative stress, proteolysis, and chaperone activity. with minimal resistance training in middle-aged adults. Ongoing efforts will determine if autophagy is altered and/or any of the outcomes were significantly associated with the hypertrophic responses. DTL is supported by a Presidential Graduate Research Fellowship. Assay costs & supplies were provided through discretionary laboratory funds & resources from MDR & ANK. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.