Chronotropic Response and Heart Rate Variability before and after a 160 m Walking Test in Young, Middle-Aged, Frail, and Non-Frail Older Adults

Figures

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  Figure 1. Flow diagram of the study protocol. FRAIL = fatigue, resistance, ambulation, illness, and low performance scale; CFS = clinical frailty scale; HRV = heart rate variability; FFT = Fast Fourier Transform; PSD = power spectrum density; ROC = receiver operator characteristic.

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  Figure 2. Heart rate time series from a selected (a) young adult, (b) a non-frail older adult and (c) a frail older adult during the whole test. The left fragment shaded in gray corresponds to the first 5 min of standing rest (baseline). The white part shows the fragment where participants walked a fixed distance of 160 m. Fragment sizes of walking are different as every person walked at their own preferred pace. The right gray shaded fragment corresponds with the recovery phase, which means 5 min of standing rest. Adapted with permission from Ref. [27]. 2022, AIP Publishing.

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  Figure 3. Receiver-operator characteristic (ROC) curve (A) and scatter plot (B) of LF (nu) evaluated during 5 min of standing rest (baseline phase) in 15 non-frail and 27 frail older adults. The best cut-off point, indicated by symbol ‘x’ in panel (A), was determined according to the shortest orthogonal distance from each point to the optimum vale (0,1). The line in panel (B) indicates the cut-off point at 77.3 normalized units (nu).

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  Figure 4. (a) Heart rate time series from young adults (group C1), non-frail older adults (group nF) and frail older adults (group F) during the whole test. Dashed vertical line represent the final of baseline phase (first 5 min). The final of the walking test cannot be specified as every subject walked to their own pace and traveled the fixed distance of 160 m in different times. (b) Chronotropic response ΔHR and changes in selected HRV parameters comparing recovery vs. baseline phases expressed as a percentage. Changes were calculated through Equation (1) for young (C1), middle-aged adults (C2), non-frail older adults (nF), and frail adults (F). Black dots in panel (b) represent the outliers of the data. ¶ p < 0.05 compared to C1 (comparison between groups). # p < 0.05 compared to C1 (comparison between groups).