Objective: In cardiac rehabilitation, a treadmill is one of the most convenient devices in exercise tolerance test (ETT) to evaluate objective physiologic responses. However, it is difficult to apply the conventional treadmill to the patients with general weakness, motor weakness or pain on the lower extremities. A treadmill using body weight support (BWS) might be helpful to patients having such problems. There are few researches on the alteration of oxygen consumption in middle-aged people. The aim of this study was to quantify the changes of oxygen consumption during ETT with BWS system in middle-aged people who may have clinically more chances of taking ETT than other age groups.
Methods: We evaluated 20 healthy, middle-aged people (age 57.4±3.8 years; height 161.4±9.6 cm; weight 62.2±11.1; 10-M walking test at comfortable speed, 8.3±1.7 seconds; 10-M walking test at maximal speed, 6.0±1.3 seconds) who can walk independently without any aids. ETT was performed by Bruce protocol (stage 1∼stage 10) at four different body weight support levels (BWST 0%, BWST 25%, BWST 50% and BWST 75%). And the interval time between each level of BWS treadmill test was 20 minutes for recovery to the basal status. We measured systolic blood pressure, diastolic blood pressure, peak heart rate, rating of perceived exertion (RPE), metabolic equivalents (METs) and oxygen consumption rate (VO2) at each BWS level.
Results: Systolic blood pressure and diastolic blood pressure were not different among the BWS levels at any stages. Peak heart rate, RPE, and METs were negatively associated with BWS level, although they were not always significantly different between BWS levels. As BWS level increased, VO2 also showed a tendency to decrease. At stage 1, VO2 on the conventional treadmill and BWST 25% were significantly higher than that on BWST 50% and 75% (p<0.05). VO2 on the conventional treadmill and BWST 25% were significantly different from the other BWSTs at stage 2 and 3. BWST 75% displayed significantly lower VO2 than the conventional treadmill and BWST 25% at stage 4. From stage 5, the relationship between the level of BWST and VO2 was not significant, although VO2 decreased as BWS level increased. The equation from a multiple regression analysis was: VO2 (ml/kg/min) = (3.077 × stage) + (−0.123 × BWST level) + 16.154 (r2 = 0.526).
Conclusions: We studied the changes of oxygen consumption in middle-aged people during maximal ETT with BWS system. We can apply BWS treadmill to the patients who cannot participate in ETT due to their gait problems. Also we can expand the BWS treadmill usage in safety. |
