Cardiovascular responses in older adults with total knee arthroplasty at rest and with exercise on a positive pressure treadmill

We investigated cardiovascular responses at rest and during submaximal exercise on a lower body positive pressure treadmill in older adults with total knee arthroplasty (TKA). Twenty-four adults (mean age 64.6 +/- A 7.9 SD) with unilateral TKA participated (median time since surgery 8.0 weeks). Heart rate and blood pressure responses were measured at rest standing on the positive pressure treadmill with 0, 10, 20, and 30 mmHg applied. Heart rate, blood pressure, oxygen consumption, minute ventilation, knee pain and perceived exertion were measured during submaximal exercise tests (0 and 40 % body weight support) conducted 1 week apart. At rest there were no differences in blood pressure across different treadmill pressures, but heart rate was significantly lower when 30 mmHg was applied compared to ambient pressure conditions (P < 0.05). Participants averaged 5.1 exercise test stages with 0 % body weight support (maximum speed 2.5 mph, 0 % incline) and 6.4 stages with 40 % body weight support (maximum speed 3.0 mph, 10 % incline). During exercise, heart rate, systolic blood pressure, oxygen consumption, and minute ventilation were lower when 40 % body weight support was provided for a given test stage (P < 0.01). Diastolic blood pressure, knee pain and perceived exertion did not differ with body weight support but increased with increasing exercise test stages (P < 0.05). Provision of body weight support allowed TKA patients to walk at faster speeds and/or to tolerate greater incline with relatively lower levels of heart rate, blood pressure, and oxygen consumption.