Author(s): ACEITUNO PINTO, H., CANO-CAPPELLACCI, M., OPAZO-DÍAZ, E., YUMHA, M.J., AMADOR, P., Institution: UNIVERSIDAD DE CHILE, Country: CHILE, Abstract-ID: 929

INTRODUCTION:
Recently, it has been reported in young, trained males and males with obesity that in the moderate intensity domain of exercise, heart rate (HR) kinetics exhibit a slow component, distinct from oxygen uptake, which reaches a steady state at intensities below ventilatory threshold 1 (VT1). The functional significance of the slow component in at moderate intensity is unclear. The autonomous nervous system (ANS) is known to be the principal modulator of HR during exercise. Therefore, the aim of this study is to establish the relationship between HR variability, representing the ANS, and the HR kinetics in moderate intensity domain in normal weight persons and persons with grade 1 obesity.
METHODS:
Sixteen persons with grade I obesity (OB) of 27 ± 4 years old and sixteen age-matched normal weight persons (NW) were recruited. All volunteers visited the laboratory on two non-consecutive days. On the first day, resting HR variability was measured, and an incremental test was conducted to determine VT1. HR variability assessment involved calculation of low frequency (LF), very low frequency (VLF) and high frequency (HF) power and the ratio LF/HF. On second day, subjects performed three transitions from unloaded cycling to 70% of the load associated with VT1. HR was measured during each transition. HR kinetics were determined for each participant following the procedure described by Zuccarelli et al. (2018). One of three possible models: mono-exponential, biexponential, and exponential+linear) were fitted to the HR data. The frequency of each model in each group was compared using chi-squared analysis. Comparisons between groups were made using the Mann-Whitney test, and Spearmans test was used to establish correlations between variables. Statistical significance for all tests was set at p ≤ 0.05.

Zuccarelli, L. et al. (2018). Comparison between Slow Components of HR and V&O2 Kinetics. Medicine & Science in Sports & Exercise, 50(8), 1649–1
RESULTS:
In the OB group, the frequency of HR kinetics with mono-exponential, biexponential, and exponential+linear models was 2, 10, and 4, respectively, whereas in NW group was 2, 12, and 2, respectively, with no significant differences in frequency between groups (p = 0.65). Significant differences between NW and OB groups were found in baseline HR (p = 0.018) and time delay (p = 0.001). Significant correlations were observed in the OB group between baseline heart rate and LF (Rho = -0.51) and LF/HF (Rho = -0.46). In the other hand, in the NW group, significant correlations were observed between fundamental HR and LF (Rho = 0.42) and VLF (Rho = 0.47).
CONCLUSION:
NW and OB persons exhibit similar HR responses to constant load moderate exercise, and not all subjects exhibit the HR slow component. Parameters of heart rate variability are related differently with heart rate kinetics parameters in OB and NW groups. Further studies could focus on identifying factors that determine the type of heart rate response to moderate exercise intensity.