Cardiac Autonomic Responses during Exercise and Post-exercise Recovery Using Heart Rate Variability and Systolic Time Intervals—A Review

Abstract

Cardiac parasympathetic activity may be non-invasively investigated using heart rate variability (HRV), although HRV is not widely accepted to reflect sympathetic activity. Instead, cardiac sympathetic activity may be investigated using systolic time intervals (STI), such as the pre-ejection period. Although these autonomic indices are typically measured during rest, the “reactivity hypothesis” suggests that investigating responses to a stressor (e.g., exercise) may be a valuable monitoring approach in clinical and high-performance settings. However, when interpreting these indices it is important to consider how the exercise dose itself (i.e., intensity, duration, and modality) may influence the response. Therefore, the purpose of this investigation was to review the literature regarding how the exercise dosage influences these autonomic indices during exercise and acute post-exercise recovery. There are substantial methodological variations throughout the literature regarding HRV responses to exercise, in terms of exercise protocols and HRV analysis techniques. Exercise intensity is the primary factor influencing HRV, with a greater intensity eliciting a lower HRV during exercise up to moderate-high intensity, with minimal change observed as intensity is increased further. Post-exercise, a greater preceding intensity is associated with a slower HRV recovery, although the dose-response remains unclear. A longer exercise duration has been reported to elicit a lower HRV only during low-moderate intensity and when accompanied by cardiovascular drift, while a small number of studies have reported conflicting results regarding whether a longer duration delays HRV recovery. “Modality” has been defined multiple ways, with limited evidence suggesting exercise of a greater muscle mass and/or energy expenditure may delay HRV recovery. STI responses during exercise and recovery have seldom been reported, although limited data suggests that intensity is a key determining factor. Concurrent monitoring of HRV and STI may be a valuable non-invasive approach to investigate autonomic stress reactivity; however, this integrative approach has not yet been applied with regards to exercise stressors.

Face cooling exposes cardiac parasympathetic and sympathetic dysfunction in recently concussed college athletes

“…However, deducing which branch of the autonomic nervous system is abnormal in concussion patients during sympathoexcitatory maneuvers using heart rate variability metrics is difficult because heart rate variability metrics largely represent parasympathetic activity (Joyner ; Michael et al. ). Nonetheless, some heart rate variability metrics, such as RMSSD and HF, have been found to be abnormal in concussion patients during standing (Hilz et al.…”

“…Some investigations have assessed heart rate variability in concussed patients during various sympathoexcitatory maneuvers. However, deducing which branch of the autonomic nervous system is abnormal in concussion patients during sympathoexcitatory maneuvers using heart rate variability metrics is difficult because heart rate variability metrics largely represent parasympathetic activity (Joyner 2016;Michael et al 2017). Nonetheless, some heart rate variability metrics, such as RMSSD and HF, have been found to be abnormal in concussion patients during standing (Hilz et al 2011), isometric handgrip exercise (Abaji et al 2016), and submaximal cycle ergometer aerobic exercise (Gall et al 2004).…”

“…Heart rate variability is an analysis technique that has been used to assess autonomic function in concussion patients and primarily gives information regarding cardiac parasympathetic activity (Joyner ; Michael et al. ). Results supporting the idea that resting autonomic function is impaired in concussion patients are inconclusive.…”

“…In this context, concussion patients can exhibit brainstem abnormalities and lesions (Levine et al 2008;Niogi et al 2008;Rutgers et al 2008;Huang et al 2009;Polak et al 2015), which provides structural evidence that autonomic control centers located in the brainstem could be disrupted following a concussion. Heart rate variability is an analysis technique that has been used to assess autonomic function in concussion patients and primarily gives information regarding cardiac parasympathetic activity (Joyner 2016;Michael et al 2017). Results supporting the idea that resting autonomic function is impaired in concussion patients are inconclusive.…”

Cardiometabolic Recovery and Lactate Removal may be Related to Muscular Adaptations

“…Heart rate variability (HRV) analysis is an established method used to quantify the extent of autonomic recovery from exercise [5,6]. After completing a given exercise, a rapid decrease in parasympathetic cardiac activity to resting levels suggests a relative and physiological systemic recovery imposed by the workload [7,8] and the amount of time required for parasympathetic reactivation after exercise may be significantly influenced by several factors, including exercise intensity[9] and cardiorespiratory fitness [10,11].…”