Resistance training increases lower body negative pressure tolerance

This study investigated whether whole body resistance training would increase tolerance to lower body negative pressure (LBNP). Twelve males (age = 19.6 +/- 0.4 yr; mean +/- SD) underwent an acute, 12-wk program of upper and lower body resistance training (ART). Pre- and posttraining, the ART group and a control group (CON; N = 8; age = 25.4 +/- 2.4 yr) underwent LBNP tolerance tests and neck pressure-suction testing. Additionally, a group of chronically resistance-trained individuals (CRT group; N = 5; age = 22.4 +/- 0.9 yr) were tested. LBNP tolerance was increased in the ART group after training and the CRT group exhibited a significantly higher LBNP tolerance than the other groups. The ART group exhibited a decreased leg circumference change at the same absolute negative pressure at which tolerance occurred pretraining. This indicated a decreased fluid pooling after ART. The CRT group exhibited a "flattened" hypotensive portion of the carotid sinus-heart rate baroreflex curve, but this appeared to be due to the increased neck muscle mass of the subjects. We conclude that whole body ART increases LBNP tolerance possibly mediated through alterations in vascular compliance. CRT results in even greater LBNP tolerance with the responsible mediating mechanisms unclear.