(21) INTERPRETING HEART RATE VARABILITY TRENDS IN NATIONAL COLLEGIATE ATHLETIC ASSOCIATION DIVISION II INTERCOLLEGIATE FOOTBALL ATHLETES

Background: Intercollegiate (American) football athletes are exposed to a vast number of sport- and non-sport- related stressors throughout the sport season, which when not addressed can negatively impact athletic performance. Coaches overseeing these athletes can use heart rate variability (HRV), a non-invasive and easily accessible stress marker, to monitor and adjust each athlete’s training to mitigate fatigue. This monitoring system may assist coaches in optimizing athlete performance throughout the season.

Purpose: To identify HRV trends in intercollegiate football players across the sport season, including pre-season camp.

Methods: Eight (four linemen and four non-linemen) NCAA DII football athletes completed this study. Resting heart rate (RHR), natural logarithm root mean square of successive differences (lnRMSSD), lnRMSSD covariance (lnRMSSDcv), vertical jump (VJ), and psychometric scores were obtained Monday-Thursday with a minimum of 3 recordings being averaged to represent a weekly value. Each HRV assessment (Polar H10 chest strap, EliteHRV app) were obtained between 6:30am and 9:30am before resistance training sessions and under fasted conditions. Recordings consisted of a 1-minute stabilization period followed by 1-minute recording period. Measurements were taken at baseline, each week of pre-season camp, bi-weekly through the competitive season, and post-season. Maximal oxygen uptake (VO_2max) was assessed via McArdle Step Test at baseline, after pre-season camp, at mid-competitive season, and post-season. One-way repeated measures ANOVA and Pearson correlation (r) were used to identify statistical differences (p< 0.05) and relationships between variables at baseline, pre-season, mid-season, and post-season.

Results: lnRMSSD had a strong to very strong positive relationship with VO_2max (r=1, p< 0.001), while VJ had a weak to very weak relationship with lnRMSSD (r=0.05-0.271, p=0.556-0.907) throughout the season. The relationship between HRV measures and psychometric scores throughout the season were inconsistent.

Conclusion: Increased fatigue was identified in the week following each long ( >4 hours) road game. lnRMSSDcv showed greater sensitivity to game travel compared to lnRMSSD. The accumulation of fatigue identified by HRV measures aligned with the gradual decline in VO_2max across the season. HRV appeared to be a better indicator of fatigue than peak VJ height and the single-item psychometric questionnaire protocols that were previously used. PRACTICAL APPLICATION: HRV is an easy, non-invasive method to monitor athlete fatigue and readiness to train. Interpreting HRV values may aid coaches in planning weekly training loads, especially following game travel, to minimize performance decrements imposed by the accumulation of unmanaged stress. Coaches and sport scientists should aim for changes within the smallest worthwhile change of mean HRV values to manage sport- and non-sport-related stressors. Additionally, the use of HRV to monitor athlete readiness may be more sensitive than other athlete monitoring methods.

Acknowledgements: None