The Ability Of Cardiac Autonomic Modulations Stress Index To Independently Predict Vo2max In Healthy Individuals

Cardiac autonomic modulation (CAM) is a pivotal element of heart health and the interaction of the sympathetic and autonomic systems (SAS). There is a clear link between CAM and the influence that aerobic exercise has on improving vascular health. Continual assessment of aerobic fitness is important to altering and improving training regimens to positively influence athletic performance. Heart rate variability (HRV) is commonly used to assess CAM in various healthy and athletic populations. A component of HRV that has recently been identified in determining the regulation of the SAS involvement in athletic performance and recovery outcomes is the stress index (SI). Henceforth, the SI may potentially provide a quick and non-invasive metric to assess aerobic performance more accurately. PURPOSE: To determine if the SI can accurately predict aerobic performance via VO2max in healthy individuals free of metabolic diseases. METHODS: fifty cardiometabolically healthy individuals (n = 30 males, n = 20 females; Age 37.8 + 12.7 years, %BF 24.9 + 4.0) completed a single maximal treadmill exercise protocol to determine VO2max. HRV was measured for 5 minutes in the supine position prior to performing the exercise protocol using an elastic belt and Bluetooth monitor (Polar H7). CardioMood software was used to process HRV indices; SI, high frequency (HF), low frequency (LF), and total power (TP) were assessed for the frequency domain, and standard deviation of all NN intervals (SDNN) and the square root of the mean of the squares of successive R-R interval differences (RMSSD) for the time domain. The data was analyzed using a multiple correlation and linear regression between HRV indices and VO2max to determine the relationship between the two. All analyses were performed using SAS (v. 28.0.1.1). RESULTS: HRV indices SI was not significantly correlated to VO2max (r = -0.118, p = 0.414). Additionally, SI and all other HRV indices were not able to independently or combined predict VO2max (R2 = 0.014, p = 0.414). CONCLUSION: The utilization of HRV to assess CAM has proven beneficial in multiple clinical and athletic settings. However, the utilization of the SI to predict aerobic performance via VO2max does not appear to be significant. Therefore, there are potential limitations to HRV to non-invasively assess aerobic performance.