Leg Immobilization and Recovery Resistance Training Affect Skeletal Muscle Angiogenesis-related Markers In Young Healthy Adults Regardless of Prior Training Experience

We recently reported that resistance trained (T, n=10) and untrained (UT, n=11) young adults (18-35 years old) experience vastus lateralis (VL) muscle atrophy following 2 weeks of disuse, and 8 weeks of recovery resistance training promotes VL hypertrophy in both groups. However, angiogenesis protein targets and muscle capillary number were not examined. Currently, no human studies have determined if disuse followed by recovery resistance training affects angiogenesis-related markers. Therefore, we examined whether disuse and/or recovery resistance training affected angiogenesis-related markers. All participants underwent 2 weeks of left leg immobilization using locking leg braces and crutches followed by 8 weeks (3d/week) of knee extensor focused progressive resistance training. VL biopsies were obtained at baseline (PRE), immediately after disuse (MID), and after resistance training (POST). Western blotting was used to assay angiogenesis-related markers and immunohistochemistry was performed in 16 of 21 participants to determine type I and II muscle fiber capillary number. Significant main effects of time (p<0.05) were observed for protein levels of VEGF (MID<POST), VEGFR2 (PRE & MID<POST), TSP-1 (PRE<POST), TIMP1 (MID<POST), phosphorylated/pan eNOS (Ser1177) (POST<PRE), and pan eNOS (PRE<POST). VEGFR2 exhibited a training status*time (p=0.018) effect, but no differences exist between T and UT at any time point. A significant main effect of time was observed for type II fiber capillary number (PRE<POST), and type II fiber cross-sectional area increased from MID-to-POST (+25%, p<0.001) and PRE-to-POST (+20%, p=0.019). No significant correlations exist for percentage changes in type II fiber capillary number and type II fiber cross-sectional area from PRE-to-MID (r= 0.020), MID-to-POST (r= 0.392), or PRE-to-POST (r= -0.120) across all participants (p>0.100). Although disuse and recovery resistance training affect skeletal muscle angiogenesis-related markers, prior training history does not differentially affect these outcomes. Mason McIntosh was supported by NIH G-RISE T32 Fellowship (5T32GM141739-03). 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.