AEROBIC POWER AND SHORT-TERM HEART RATE VARIABILITY DURING HEAD-DOWN NECK FLEXION

Abstract

900 Short-term heart rate variability (HRV) is positively related to aerobic power. However, the relationship between aerobic power and changes in HRV during physiological perturbations is not as well understood. The purpose of this study was to determine the relationship between the change in HRV evoked by head-down neck flexion (HDNF) and VO2peak in young, healthy volunteers. Five-minute EKG recordings were obtained from 11 participants (age=19-22) while lying prone (P) and during HDNF, 10 of whom completed a maximal incremental exercise test on a cycle ergometer for determination of VO2peak. The EKG recordings were assessed for the standard deviation of normal RR intervals (SDNN) and for high- and low-frequency spectral power (HF and LF). The VO2peaks ranged from 28 to 41 ml/kg/min and were positively associated with SDNN under P and HDNF conditions (r=0.649 and r=0.733, respectively). HDNF resulted in a decrease in SDNN (91.6±12.4 to 75.9±9.9; p<0.05) and an increase in LF/HF (0.811±0.18 to 1.36±0.37; p<0.05). Furthermore, the association between VO2peak and change in SDNN during HDNF approached significance (p=0.19). These data indicate a positive relationship between VO2peak and HRV, and further suggest an increase in sympathovagal balance during HDNF. In addition, these data may point towards a relationship between the change in SDNN and VO2peak. Further investigation is needed in healthy, as well as other populations, to determine if the magnitude of change in HRV during physiological perturbations is associated with greater cardiovascular risk.