Investigating interpersonal relationships between school resource officers and Black students

This investigation examined skeletal muscle fiber type specific differences in fiber size, myonuclear content, satellite cell content, and capillarity with aging and lifelong aerobic exercise. Healthy women (n=27) and men (n=41) were recruited and thoroughly screened into three groups: young exercisers (YE women: n=10, 25±1 y, VO2max 44±2 ml/kg/min; YE men: n=10, 25±1, VO2max 53±3 ml/kg/min), lifelong exercisers (LLE women: n=7, 72±2 y, VO2max 26±2 ml/kg/min; LLE men: n=21, 74±1 y, VO2max 34±1 ml/kg/min), and old healthy controls (OH women: n=10, 75±1 y, VO2max 18±1 ml/kg/min; OH men: n=10, 75±1 y, VO2max 22±1 ml/kg/min). LLE men were further subdivided into LLE-Performance (LLE-P: n=14, 74±1 y, VO2max 38±1 ml/kg/min) and LLE-Fitness (LLEF: n=7, 75±2 y, VO2max 27±2 ml/kg/min), based on their training intensity and competitive focus. LLE exercised on average ~5 days/wk for 7 h/wk for >50 y. Muscle biopsies were obtained from the vastus lateralis and immunofluorescently stained and analyzed for fiber type, size, myonuclear content, satellite cell content, and capillarity. On average, 683±22 and 558±20 fibers were analyzed for each female and male subject, respectively. Women showed a few hierarchical trends (YE>LLE>OH) in composite fiber size (P<0.05 for YE ii vs. OH only) and capillarity (CCEF, P<0.05 for all). LLE women had similar fiber type distribution as YE, and a trend toward greater MHC I fiber distribution (P=0.09) and lower hybrid distribution (P=0.09) relative to OH. OH women had fewer MHC I fibers compared to YE (P<0.05). LLE women had ~2x greater satellite cells than YE (P<0.05). In men, LLE had a greater MHC I fiber distribution than OH (P<0.05), OH men had the highest MHC IIA/IIX hybrid fiber distribution (P<0.05), and YE men trended toward greater MHC IIA fiber distribution than LLE (P=0.08). LLE men had ~25% greater MHC I fiber size than the other groups (P<0.05 vs. YE and OH) and greater MHC I fiber and all-fiber composite capillarity compared to healthy aging (P<0.05 vs. OH). Increased training intensity (LLEP) was associated with less MHC I/IIA hybrid fibers (P