Effects of body weight support and gait velocity via antigravity treadmill on cardiovascular responses early after total knee arthroplasty

To investigate the effects of body weight support (BWS) and gait velocity on cardiovascular responses during walking on an antigravity treadmill early after unilateral and bilateral total knee arthroplasty (TKA). This study was a cross-sectional study design. Fifty patients (7 males and 43 females; average age, 72.0 ± 5.1 years) at 4 weeks after unilateral (n = 25) and bilateral (n = 25) primary TKA were enrolled in the study. Subjects walked on an antigravity treadmill at speeds of 2.5 km/hour and 3.5 km/hour with 3 levels (50%, 25%, and 0%) of BWS. Cardiovascular responses were monitored by measuring oxygen consumption (VO(2)), heart rate (HR), systolic and diastolic blood pressure (SBP/DBP), the respiratory exchange ratio (RER), and rate pressure product (RPP). Borg rating of perceived exertion (RPE) and a visual analog scale (VAS) of knee pain were recorded immediately after each trial. There were no significant differences in cardiovascular responses between the unilateral and bilateral TKA groups. In the repeated measures Analysis of Variance, VO(2) levels, HR, RPP, RPE, RER, and VAS were significantly increased in proportion to 3 levels (50%, 25%, and 0%) of BWS for unilateral and bilateral TKA groups, respectively. Meanwhile, SBP and DBP were unaffected by differences in BWS. At 3.5 km/hour, VO(2), RPE, and RER values were statistically greater than those at 2.5 km/hour under the same BWS conditions. We found that the reduction in the metabolic demand of activity, coupled with positive pressure on the lower extremities, reduced VO(2) and HR values as BWS increased. Cardiovascular responses vary according to BWS and gait velocity during antigravity treadmill walking. BWS rather than gait velocity had the greatest effect on cardiovascular responses and knee pain.