Influence of aerobic fitness on cardiovascular responses during slow head-down tilting.

This study examined the influence of cardiorespiratory fitness (CRF) on mean heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) responses to slow head-down tilting. Twenty-four young, healthy volunteers were tilted randomly from the horizontal plane to -30, -60, and -90 degrees with lower limbs extended or flexed. A multivariate analysis of variance between three independent variables (level of CRF, tilt angle, and lower limb position) and three dependent variables (mean HR, SBP, and DBP) was performed on the cardiovascular changes from an initial horizontal baseline value (absolute change) and from a horizontal value that immediately preceded tilting angles (relative change). The results for significant absolute cardiovascular changes indicated a CRF influence on HR increase (F = 6.42, p less than .05), a tilt-angle influence on SBP increase (F = 9.56, p less than .001), and DBP increase (F = 6.49, p less than .01) and an interaction influence between CRF level and limb position for DBP (F = 5.83, p less than .05). Significant relative cardiovascular change was noted for tilt-angle influence on HR (F = 9.04, p less than or equal to .001). We conclude, therefore, that physical therapists should consider the CRF of individuals and the tilt angle to be used before they conduct slow head-down tilting for therapy.