Dehydration during recovery from muscle damage impairs satellite cell activation in young men

Roughly 3 out of 10 adults are dehydrated. While the effect of dehydration on endurance performance is well known, its effect on muscle repair has not been elucidated. Our pilot data demonstrate that 72-h dehydration during recovery delayed muscular strength recovery following muscle damage in young men compared with euhydration, which suggest that there could be an alteration in muscle repair. Muscle repair following damage requires the activation and proliferation of satellite cells, commonly reflected by an increase in the number of Pax7 + satellite cells. Given the high prevalence of dehydration and its detrimental effect on performance recovery, whether dehydration alters key cellular mechanisms of muscle repair, satellite cell activation, remains unknown. Purpose: To examine the effect of dehydration during recovery on SC activation after muscle damaging exercise in young men. Hypothesis: Dehydration during recovery will impair SC activation compared to recovering in a hydrated state in young men. Methods: Recreationally active men (n=6, 20±3yr, 173.6±8.1cm, 78.9±12.2kg) completed two identical unilateral maximal eccentric knee extensions protocols (EIMD; 10 sets × 30 reps) in a hydrated state to induce muscle damage. To ensure that participants were hydrated prior to the EIMD protocol, participants underwent a 3-day hydration baseline during which they consumed >3.7L of water per day. Following EIMD, participants underwent 48hr of recovery under either hydrated (HYD) or dehydrated (DEH) condition using a randomized crossover design. For DEH, no fluid was consumed for 24hr and then consumed 1.5L of water for the remaining 24hr. For HYD, participants consumed >3.7L of water each day for 48hr. For both conditions, participants consumed the same low moisture diet to control the effect of macronutrients on recovery. Vastus lateralis (VL) samples were collected prior to (PRE), 24hr, and 48hr post EIMD. Immunohistochemical analysis was used to identify the number of Pax7+/DAPI+ cells. The number of Pax7+/DAPI+ cells were manually counted using ImageJ and then normalized to 100 muscle fibers. Results: A significant (p< 0.05) time × condition interaction effect was observed. In HYD, the number of Pax7+/DAPI+ cells increased from PRE (17±4cells; p=0.003) and 24hr (14±2cells; p=0.024) to 48hr (25±1cells). At 48hr, the number of Pax7+/DAPI+ cells in HYD (25±1cells) were greater than DEH (15±2cells; p=0.011). No significant differences for the number of Pax7+/DAPI+ cells were observed in the DEH condition across time. Conclusion: Mild dehydration during recovery from muscle damage impairs satellite cell activation in young men, highlighting hydration status as a modifiable determinant of skeletal muscle regeneration. However, the long-term effect of underhydration on skeletal muscle repair warrants further investigation. Disclosure of funding sources: This project was supported by institutional start-up funds awarded to Dr. Hui-Ying Luk at Texas Tech University. This abstract was presented at the American Physiology Summit 2026 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.