Heart Rate Variability-Derived Thresholds for Exercise Intensity Prescription in Endurance Sports: A Systematic Review of Interrelations and Agreement with Different Ventilatory and Blood Lactate Thresholds

Abstract

Background Exercise intensities are prescribed using specific intensity zones (moderate, heavy, and severe) determined by a ‘lower’ and a ‘higher’ threshold. Typically, ventilatory (VT) or blood lactate thresholds (LT), and critical power/speed concepts (CP/CS) are used. Various heart rate variability-derived thresholds (HRVTs) using different HRV indices may constitute applicable alternatives, but a systematic review of the proximity of HRVTs to established threshold concepts is lacking. Objective This systematic review aims to provide an overview of studies that determined HRVTs during endurance exercise in healthy adults in comparison with a reference VT and/or LT concept. Methods A systematic literature search for studies determining HRVTs in healthy individuals during endurance exercise and comparing them with VTs or LTs was conducted in Scopus, PubMed and Web of Science (until January 2022). Studies claiming to describe similar physiological boundaries to delineate moderate from heavy (HRVTlow vs. VTlow and/or LTlow), and heavy from severe intensity zone (HRVThigh vs. VThigh and/or LThigh) were grouped and their results synthesized. Results Twenty-seven included studies (461 participants) showed a mean difference in relative HR between HRVTlow and VTlow of − 0.6%bpm in weighted means and 0.02%bpm between HRVTlow and LTlow. Bias between HR at HRVTlow and VTlow was 1 bpm (limits of agreement (LoA): − 10.9 to 12.8 bpm) and 2.7 bpm (LoA: − 20.4 to 25.8 bpm) between HRVTlow and LTlow. Mean difference in HR between HRVThigh and VThigh was 0.3%bpm in weighted means and 2.9%bpm between HRVThigh and LThigh while bias between HR at HRVThigh and VThigh was − 4 bpm (LoA: − 17.9 to 9.9 bpm) and 2.5 bpm (LoA: − 12.1 to 17.1 bpm) between HRVThigh and LThigh. Conclusion HRVTlow seems to be a promising approach for the determination of a ‘lower’ threshold comparable to VTlow and potentially for HRVThigh compared to VThigh, although the latter needs further empirical evaluation. LoA for both intensity zone boundaries indicates bias of HRVTs on an individual level. Taken together, HRVTs can be a promising alternative for prescribing exercise intensity in healthy, male athletes undertaking endurance activities but due to the heterogeneity of study design, threshold concepts, standardization, and lack of female participants, further research is necessary to draw more robust and nuanced conclusions.

Metabolic flexibility and resting autonomic function in active menopausal women

“…Therefore, in situations of moderate intensity, such as FATmax -the intensity at which MFO is reached-, the better the autonomic resources at rest (i.e., better cardiovascular health) the higher the energy derived from fats may be, allowing carbohydrates to be used as a substrate at intensities over FATmax. Consequently, maintaining resting sympathovagal balance and a well-functioning vagal activity, lead to better metabolic exibility in MFO intensities, which could be related to the effective communication between the liver and the brain via the sympathetic (afferent) and vagus (efferent) nerves (Matsubara et al, 2022), pointing to these nonlinear variables as quali ed descriptors of cardiovascular and metabolic regulation and control systems (Kaufmann et al, 2023). This interaction and maintenance of balance would enhance the ability to effectively modulate energy substrate availability.…”

Reliability and validity of a non-linear index of heart rate variability to determine intensity thresholds

“…Considering these issues, searching for an alternative to determining exercise intensity thresholds is justifiable. Threshold detection using heart rate (HR) variability (HRV) has been extensively investigated over the past years since HR monitoring presents a relatively simple, non-invasive, and cost-effective option available to the general population ( Kaufmann et al, 2023 ). HRV offers insights into the fluctuations in heart rate from beat to beat and can reveal physiological adaptations in several conditions, including exercise ( Manresa-Rocamora et al, 2021 ).…”

Exploring the Hidden Complexity: Entropy Analysis in Pulse Oximetry of Female Athletes

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