This study was undertaken to investigate cardiorespiratory response according to weight support and velocity using a lower-body positive pressure (LBPP) treadmill and to find specific velocity and weight support combinations after bilateral TKA.

Twenty-five patients who underwent a primary TKA were enrolled. Subjects walked with 2.5km/h and 3.5km/h on a LBPP treadmill at 3 levels (50%, 75%, 100%) of body weight (BW). Each trial was performed for 2minutes. Oxygen consumption (VO₂), heart rate, systolic (SBP) and diastolic blood pressure (DBP), respiratory exchange ratio (RER) and rate pulse product (RPP) were measured continuously with average values. Borg's rating of perceived exertion scale (RPE) and Visual Analog Scale (VAS) of knee pain were recorded immediately after each condition.

In the two-way repeated measures Anova, VO₂ levels (P<0.01) were increased in proportion to BW. HR (P<0.01), RPP (P<0.01), RPE (P<0.01), RER (P<0.01) and VAS (P<0.01) were also higher at 100% of BW compared with 50% and 75% of BW. However, SBP (P=0.65) and DBP (P=0.39) were not influenced by difference of BW levels. While walking with a speed of 3.5m/s at same BW level, only RPE (P<0.01) and RER (P=0.01) values were statistically greater than 2.5m/s. Based on BW and gait velocity settings of the LBPP treadmill, the equations were VO₂=1.46 v+0.081 BW+3.13 (r²=0.34).

This study demonstrated that cardiorespiratory responses during LBPP treadmill were determined by combination of weight support and velocity, and it was more influenced by change of weight support than velocity. These findings suggest that factors such as body weight support and speed should be considered for gait training to improve aerobic capacity early after bilateral total knee arthroplasty.