Physiological responses to the incremental shuttle walk test in healthy adults

Abstract

Physiological responses to the incremental shuttle walk test (ISWT) have been increasingly evaluated in patients. However, previous studies did not include healthy individuals. The aim of this study was to evaluate age- and gender-related changes in physiological responses to the ISWT and to establish predictive equations for such variables. We evaluated 103 non-trained healthy adults (49 males, aged 60±10). After familiarization, ISWT was performed using a telemetric gas analyzer. Physiological responses including oxygen uptake at ventilatory threshold (VO₂VT) were obtained. Maximum walking velocity (Vmax), lean (LBM) and fat (FM) body masses (impedance), and handgrip strength (HGS) were also measured. Participants were stratified in four age groups (40-49 to ≥70). A set of linear equations was provided for predicting physiological variables. The VO₂VT was identified in all but one participant. Among peak variables, heart (HR) and respiratory (RR) rates, tidal volume (VT), and gas exchange ratio (R) were not affected by sex as well as VO₂/HR, R, RR, and VT were not influenced by age. There were no effect of age and gender in VO₂VT (% of peak VO₂). Prediction equations adjusted by sex, age, height, weight, LBM, FM, HGS, and ISWT showed R² values ranging 0.352 to 0.661 (VO₂VT and peak VO₂ respectively). The best predictors of peak VO₂ were HGS, weight, FM and age (R²=0.661). Age, weight, height and gender explained 59.7% of Vmax variability. The results therefore might provide a more appropriate frame of reference for normalcy of physiologic responses to the ISWT in healthy older adults. Our results may be useful for better interpretation of walking performance in patients with cardiopulmonary disease.