Dynamic physiological responses to the incremental shuttle walk test in adults

Abstract Introduction: Understanding the normal dynamic physiological responses to the incremental shuttle walk test might enhance the interpretation of walking performance in clinical settings. Objective: To assess dynamic physiological responses to the incremental shuttle walk test and its predictors in healthy adults. Methods: We assessed the simultaneous rates of changes of Δoxygen uptake/Δwalking velocity (ΔVO 2 /ΔWV), Δheart rate/Δoxygen uptake (ΔHR/ΔVO 2 ), Δventilation/Δcarbon dioxide production (ΔVE/ΔVCO 2 ), and Δtidal volume/Δlinearized ventilation (ΔVT/ΔlnVE) during the incremental shuttle walk test in 100 men and women older than 40 years. Fat and lean body masses (bioimpedance) were also evaluated. Results: We found that the dynamic relationships were not sex-dependent. Participants aged ≥ 70 presented declines in ΔVO 2 /ΔWV slope compared to those aged 40-49 (215 ± 69 vs. 288 ± 84 mL.min-1.km.h-1). Obese participants presented shallower slopes for ΔVO 2 /ΔWV (2.94 ± 0.90 vs. 3.84 ± 1.21 mL.min-1.kg-1.km.h-1) and ΔVT/ΔlnVE (0.57 ± 0.20 vs. 0.67 ± 0.26). We found negative influence of fat body mass on ΔVT/ΔlnVE (R2 = 0.20) and positive influence of lean body mass on ΔVO 2 /ΔWV (R2 = 0.31), ΔHR/ΔVO2 (R2 = 0.25), and ΔVT/ΔlnVE (R2 = 0.44). Conclusion: Dynamic relationships during walking were slightly influenced by age, but not sex-dependent. Body composition played an important role in these indices. Our results may provide better interpretation of walking performance in patients with chronic diseases. Resumo Introdução: Compreender as respostas fisiológicas dinâmicas normais ao incremental shuttle walk test pode melhorar a interpretação do desempenho da caminhada em ambientes clínicos. Objetivo: Avaliar as respostas fisiológicas dinâmicas em detrimento do incremental shuttle walk test e seus preditores em adultos saudáveis. Métodos: Foram avaliadas as taxas simultâneas de alterações de Δcaptação de oxigênio/Δvelocidade da caminhada (ΔVO2 /ΔVC), taxa de Δfrequência cardíaca/Δcaptação de oxigênio (ΔFC/ΔVO2), Δventilação/Δliberação de gás carbônico (ΔVE/ΔVCO2 ), e o Δvolume corrente/Δventilação linearizada (ΔVC/ΔlnVE) durante o incremental shuttle walk test em 100 homens e mulheres com mais de 40 anos. Massa gorda e a massa magra corporal (bioimpedância) também foram avaliadas. Resultados: Descobrimos que as relações dinâmicas não eram dependentes de sexo. Os participantes com idade ≥ 70 apresentaram declínios na inclinação da relação ΔVO2 /ΔVC e