Use of Self-paced Walking Tests to Estimate Aerobic Fitness in Older HIV-infected Patients

Abstract

PURPOSE: HIV-infected patients treated with highly active antiretroviral therapy (HAART) have increased risk for impaired aerobic capacity. Effects of aging could have an additional impact as HAART now prolongs survival for an estimated 30-50 years. Measuring aerobic capacity is cumbersome and requires resources that are not readily available to many clinicians. It is possible that field tests conducted in the office or clinic could provide adequate information regarding patients' aerobic capacity. This research aimed to determine the feasibility of using self-paced walking tests for estimating aerobic capacity in older HIV-infected patients. METHODS: 15 HIV-infected men, aged 50+ years (58 ± 5 yrs) on HAART, performed a modified Bruce graded exercise test (GXT) to exhaustion, a 6-minute walk (6-MW), and a Long Distance Corridor Walk (LDCW) on separate visits. CD4 cell count was high in these asymptomatic patients (441± 215 cells/uL). Associations between VO2peak and 6-MW distance and the 400-meter time of the LDCW were tested by Pearson correlation coefficients. Paired t-tests were used to compare ending heart rate for each test. Data are mean ± standard deviation. RESULTS: Tests were well tolerated by all subjects. Performance in the 6-MW (535 ± 92 meters) and the LDCW (400-m, 266 ± 41 seconds) walking tests were strongly correlated (r = -0.84, p<0.001). There was a linear association between VO2peak (19.4 ± 4.3 mL/kg/min) and both 6-MW distance (r = 0.55, p = 0.03) and 400-meter time (r = -0.65, p <0.01). Ending heart rate was the same for 6-MW (117 ± 15 bpm) and 400-m (118 ± 18 bpm) and was lower than the GXT (141 ± 14 bpm)(p<0.01). CD4 count was not associated with performance in any of the tests (p>0.2). CONCLUSIONS: These preliminary results suggest that self-paced walking tests may provide a safe and reasonable estimate of aerobic capacity in older HIV-infected patients on HAART. Additional subjects will help to determine the optimal protocol and covariates to derive an equation for estimating VO2peak.