Orthostatic tolerance in males who perform chronic resistance training versus controls

The purpose of this study was to investigate whether individuals who performed chronic resistance training (CRT) had an increased lower body negative pressure (LBNP) tolerance over controls (CON), and to determine if there was a correlation between lean body mass (LBM) and LBNP tolerance index (LTI). Fourteen male subjects were classified as either CRT or CON based on past history of resistance training; this was verified with 5-RM bench press and leg extension tests. The subjects attended 3 sessions. On the first session, maximal oxygen uptake (VO_2max) was assessed and the subjects were given an orientation LBNP test. During the second session, the subjects underwent a neck chamber test, another LBNP test and an orientation to strength tests. The final visit consisted of underwater weighing and final strength tests. CRT and CON subjects were not different in age, height, % body fat, VO_2max, and maximal HR (P>0.05). Significant differences were found between groups in weight, LBM, years of resistance training, 5-RM bench press and leg extension, and resting forearm and leg circumferences (FC and LC, respectively; P<0.05). LBNP data showed no between-group differences in systolic, diastolic or mean arterial blood pressures (SBP, DBP and MABP, respectively), forearm blood flow (FBF), forearm vascular resistance (FVR) and LC at rest or 25, 50, 75 or 100% LBNP max. There were, however, significant decreases in HR, SBP, MABP, and FBF for both groups as presyncopy approached. Significant differences were found between CRT and CON for LBNP_max (p=0.005) and LTI (p=0.003). LBM did not significantly correlate with LTI (p=0.0785). Multiple regression analyses indicated LBM + LC (p=0.0112) and LBM + 5-RM leg extension (p=0.0113) to be significant, however slope (beta) was -0.11. and -0.016, respectively. CRT did not alter carotid sinus mechanoreceptor function; ΔR-R was non-significantly different between CRT and CON. In conclusion, individuals who perform chronic resistance training have an improved LBNP tolerance.