Fatigability and Cardiorespiratory Fitness During Sustained Walking Following Overground Locomotor Training in Individuals with Parkinson’s Disease



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Purpose: Increased performance and perceived fatigability during sustained walking is often present in people with Parkinson’s disease (PD). Cardiorespiratory fitness is also often diminished in people with PD, and this limitation may contribute to elevated fatigability during walking in members of this patient population. Pulmonary oxygen uptake kinetics during the rest-to-work transition (V̇O2 on-kinetics) is an objective measure of cardiorespiratory fitness that can be assessed during overground walking. Overground locomotor training (OLT) is a method that may be well suited to reduce fatigability during sustained overground walking and promote concomitant improvements in cardiorespiratory fitness in people with PD. The purpose of this study was to characterize changes in performance and perceived fatigability during overground walking and V̇O2 on-kinetics following a 12-week OLT program in people with mild-to-moderate PD. Methods: Twelve individuals with PD completed our OLT program. Performance fatigability was measured using the performance fatigability index, which accounts for both speed fluctuations (indicated by a pacing index) and total distance walked during a 10-minute walk test (10MWT). Perceived fatigability was measured using the perceived fatigability index, which accounts for both changes in perceptions of tiredness following the 10MWT and the total distance walked. V̇O2 on-kinetics was determined by fitting a mono-exponential function to gas exchange data from the first 6 minutes of the 10MWT. The time constant (τ) of phase-II of the V̇O2 on-kinetics response and the oxidative response index (ORI) were used as indicators of cardiorespiratory fitness. Results: Following OLT, improvements in the performance fatigability index (mean difference = -0.1 (0.1) 1/m, 95% CI: [-0.2, 0], p = 0.0029, Cohen’s d(unbiased) = 0.64), and total distance (mean difference = +83.6 (77.5) m, 95% CI: [34.3, 132.8], p = 0.0033, Cohen’s d(unbiased) = 0.54) were observed. Small effects (mean difference = -0.3 (1.6) au, 95% CI: [-1.3, 0.7], p = 0.4921, Cohen’s d(unbiased) = 0.24) were observed for the perceived fatigability index. Improvements in phase-II τ (mean difference = -7.8 (11.5) seconds, 95% CI: [-15.1, -0.5], p = 0.0393, Cohen’s d(unbiased) = 0.54) and the ORI (mean difference = +12.8 (14.9) mL/min/s, 95% CI: [3.3, 22.3], p = 0.0126, Cohen’s d(unbiased) = 0.83) were also observed. Conclusion: These data indicate preliminary success of OLT in people with PD for modifying performance fatigability during sustained overground walking in addition to cardiorespiratory fitness.