The Physiological Association Between Mental Toughness And Heart Rate Variability

Heart rate variability (HRV) assesses the function of the parasympathetic nervous system by monitoring the variation in time between each heartbeat, representing the dysregulation of the autonomic nervous system (ANS) and sympathetic nervous system (SNS). HRV is routinely utilized to assess aerobic fitness and cardiovascular health in multiple populations and is a metric used to determine performance. Mental toughness (MT) is an up-and-coming metric also used to assess performance. Current research supports HRV being utilized as a potential tool for physiological stress and mental health due to the possible relationship between cardiac autonomic modulation and perceived psychological stress. PURPOSE: The purpose of this study was to investigate the relationship between HRV and mental toughness in healthy individuals. METHODS: Ten healthy individuals (Age 38.6 + 16.0; Ht. 66.5 + 4.0; Wt. 153.4 + 26.8; %BF 23.6 + 9.4; VO2 37.7 + 12.4) filled out a validated 8-question MT questionnaire survey to quantify MT. MT survey was separated into individual (1-8) and total scores. 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 Pearson’s correlations to determine the association between HRV variables and MT total score and single questions. All analyses were performed using SPSS (v.29.01). RESULTS: There was no significant correlation between total MT score and HRV indices (r = 0.07, p = 0.64). However, there were significant correlations between MT-Q6 and LF (r = 0.667, p = 0.035) and MT-Q8 and LF/HF ratio (r = -0.814, p = 0.004). All other individual MT questions and HRV indices correlations were not significant. CONCLUSION: Total MT scores are not associated with HRV indices in healthy individuals. However, MT individual questions are significantly correlated to the ratio between SNS and PNS activity, along with baroreceptor activity.