A systematic review with meta-analysis – Journal of Science and Medicine in Sport 2021 – published ahead of print. Düking et al.
Background: Monitoring heart rate variability (HRV) as an indicator of daily variations in the functioning of the autonomic nervous system (ANS) may assist in individualizing endurance training to produce more pronounced physiological adaptations in performance.
Aims: To systematically perform a meta-analysis of the scientific literature to determine whether the outcomes of endurance training based on HRV are more favourable than those of predefined training.
Methods: PubMed, and Web of Science were searched systematically in March of 2020 using keywords related to endurance, the ANS, and training. To compare the outcomes of HRV-guided and predefined training, Hedges’ g effect size and associated 95% confidence intervals were calculated.
Results: A total of 8 studies (198 participants) were identified encompassing 9 interventions involving a variety of approaches. Compared to predefined training, most HRV-guided interventions included fewer moderate- and/or high-intensity training sessions. Fixed effects meta-analysis revealed a significant medium-sized positive effect of HRV-guided training on submaximal physiological parameters (g=0.296, 95% CI 0.031 to 0.562, p=0.028), but its effects on performance (g =0.079, 95% CI −0.050 to 0.393 p= 0.597) and O (g =0.171, 95% CI −0.213 to 0.371, p= 0.130) are small and not statistically significant. Moreover, with regard to performance, HRV-guided training is associated with fewer non-responders and more positive responders.
Conclusions: In comparison to predefined training, H -guided endurance training has a medium-sized effect on submaximal physiological parameters, but only a small and non-significant influence on performance and O2peak. With regard to performance, there are fewer non-responders with HRV-based training.