Key result
Heavy training in male runners/triathletes increased standing vagally mediated HRV (ES 0.62; 90% CI 0.36-0.88) alongside worsened training tolerance and performance, indicating parasympathetic hyperactivity.
Why the study?
Does a training protocol of heavy training and tapering alter heart-rate variability and training tolerance in male runners/triathletes?
Does a training protocol of heavy training and tapering alter heart-rate variability and training tolerance in male runners/triathletes?
Standardized Mean Difference: 0.62 (95% CI 0.36–0.88)
Vagally mediated HRV during standing increases in response to both functional overreaching and performance improvements, highlighting the need to interpret HRV alongside subjective training tolerance.
Standing HRV increases warrant caution alongside tolerance metrics in endurance athletes; leaves open prospective validation for overreaching detection.
PURPOSE: Heart-rate variability (HRV) as a measure of autonomic function may increase in response to training interventions leading to increases or decreases in performance, making HRV interpretation difficult in isolation. This study aimed to contextualize changes in HRV with subjective measures of training tolerance. METHODS: Supine and standing measures of vagally mediated HRV (root-mean-square difference of successive normal RR intervals [RMSSD]) and measures of training tolerance (Daily Analysis of Life Demands for Athletes questionnaire, perception of energy levels, fatigue, and muscle soreness) were recorded daily during 1 wk of light training (LT), 2 wk of heavy training (HT), and 10 d of tapering (T) in 15 male runners/ triathletes. HRV and training tolerance were analyzed as rolling 7-d averages at LT, HT, and T. Performance was assessed after LT, HT, and T with a 5-km treadmill time trial (5TTT). RESULTS: Time to complete the 5TTT likely increased after HT (effect size [ES] ± 90% confidence interval = 0.16 ± 0.06) and then almost certainly decreased after T (ES = -0.34 ± 0.08). Training tolerance worsened after HT (ES ≥ 1.30 ± 0.41) and improved after T (ES ≥ 1.27 ± 0.49). Standing RMSSD very likely increased after HT (ES = 0.62 ± 0.26) and likely remained higher than LT at the completion of T (ES = 0.38 ± 0.21). Changes in supine RMSSD were possible or likely trivial. CONCLUSIONS: Vagally mediated HRV during standing increased in response to functional overreaching (indicating potential parasympathetic hyperactivity) and also to improvements in performance. Thus, additional measures such as training tolerance are required to interpret changes in vagally mediated HRV.
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Bellenger et al. (2015) studied Functional overreaching (n=15). Heavy training and tapering vs. Light training was evaluated on Standing vagally mediated HRV (RMSSD) after heavy training (ES 0.62, 95% CI 0.36-0.88 (90% CI)). Heavy training in male runners/triathletes increased standing vagally mediated HRV (ES 0.62; 90% CI 0.36-0.88) alongside worsened training tolerance and performance, indicating parasympathetic hyperactivity.
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