Influence of Age on Cardiorespiratory Kinetics During Sinusoidal Walking in Humans

Naoyuki Ebine; Alharbi Ahad-Abdulkarim-D; Yuki Miyake; Tatsuya Hojo; Daijiro Abe; Masahiro Horiuchi; Yoshiyuki Fukuoka

doi:10.3389/fphys.2018.01191

Influence of Age on Cardiorespiratory Kinetics During Sinusoidal Walking in Humans

Front Physiol. 2018 Aug 24:9:1191. doi: 10.3389/fphys.2018.01191. eCollection 2018.

Authors

Naoyuki Ebine¹, Alharbi Ahad-Abdulkarim-D¹, Yuki Miyake¹, Tatsuya Hojo¹, Daijiro Abe², Masahiro Horiuchi³, Yoshiyuki Fukuoka¹

Affiliations

¹ Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan.
² Center for Health and Sports Science, Kyushu Sangyo University, Fukuoka, Japan.
³ Division of Human Environmental Science, Mount Fuji Research Institute, Fujiyoshida, Japan.

Abstract

We sought to determine the influence of age on cardiorespiratory kinetics during sinusoidal walking in two groups: 13 healthy young subjects (YG; 7 men and 6 women, age 21 ± 2 years) and 15 healthy elderly subjects (ELD; 9 men and 6 women, age 67 ± 5 years). A treadmill's speed was sinusoidally changed between 3 and 6 km h^-1 in the YG and between 3 and 5 km h^-1 in the ELD during periods of 1, 2, 5, and 10 min, and in a stepwise manner. We compared the groups' heart rate (HR), ventilation ( $\dot{V}$ _E), and gas exchange (CO₂ output ( $\dot{V}$ CO₂) and O₂ uptake ( $\dot{V}$ O₂)) responses. We determined the phase shift (PS) and the normalized amplitude (Amp) ratio of these kinetics in relation to the sinusoidal change in walking speed in response to the magnitude from the maximum to minimum speeds as revealed by a Fourier analysis in all cardiorespiratory variables. Both the Amp ratio and PS in the $\dot{V}$ _E, $\dot{V}$ CO₂, and $\dot{V}$ O₂ responses were very similar between the ELD and YG, and being independent of the periods of sinusoidal oscillations. In marked contrast, the PS of the HR kinetics was significantly slowed in the ELD compared to the YG. The Amp ratio of HR was not related to the covariance variation of HR (CVHR) at standing rest in the ELD. The HR kinetics during sinusoidal walking may not be attributable to parasympathetic nerve activity into the heart in the ELD. The slope of the Amp of $\dot{V}$ _E related to the Amp of $\dot{V}$ CO₂ ( $\dot{V}$ _E/ $\dot{V}$ CO₂ slope) was steeper in the ELD (0.0258) compared to the YG (0.0132), suggesting that exercise hyperpnea could be greatly induced during walking in the ELD. These findings suggest that aging influences the alterations of autonomic nervous system-dependent slower HR kinetics and exercise hyperpnea during walking in the ELD.

Keywords: age; energy cost; heart rate; sinusoidal walking; ventilation.