Heart rate and RPE during exercise with concussion
In the current literature, there is an interest in the body’s ability to shift from sympathetic to parasympathetic cardiovascular functions, as well as cardiovascular rhythm, metabolism and temperature regulation and how these processes may relate to prolonged recovery from concussion.
The authors of this study hypothesized that concussed individuals would show a reduced ability to have autonomic regulation, and an increase in heart rate and perceived exertion following concussion.
A prospective and controlled study was used to investigate the autonomic response of the body following a recent concussion (mean time since injury was 5 days) when using the Buffalo Concussion Treadmill Test.
The study included 40 participants who had recently suffered a concussion over the span of an 18-month period. They were excluded from the study if they had any orthopaedic or cardiac limitations that could impend their performance. The study included both male and female subjects, with ages varying between 13 and 18 years of age.
For participants that underwent the Buffalo Concussion Treadmill Test (BCTT), the authors describe the test as follows:
“The BCTT is a test of exercise tolerance that consists of graded exercise on a treadmill until the participant reaches maximum exertion or experiences an exacerbation of symptoms (i.e., demonstrates exercise intolerance) (…) During the BCTT, exercise intensity (treadmill grade) is increased each minute until termination of the test. After each minute, participants indicated their RPE on a scale of 6–20 (the Borg scale) and average HR each minute was calculated from recordings extracted from a Polar HR monitor (Polar Electro, Model FT1). Heart rate at rest and at the initiation of exercise (exercise time zero) were recorded to compare HR before and at the onset of exertion. Participants repeated the treadmill protocol when they reported being asymptomatic and were independently evaluated by a blinded physician as being recovered from concussion.”
For the test, a group of healthy subjects was also used as a control to compare heart rate response as well as rate of perceived exertion (RPE) at each level of the test.
The authors found that the heart rate for those who were severely concussed did not differ much from states of being acutely symptomatic as well as when later in a more recovered state. However, RPE for concussed individuals was much higher when symptomatic than when symptoms had been more resolved.
This study highlights that, while an increase in cardiovascular response and RPE can be expected with an increased workload - despite the level of concussion or not - subjects perceived working much harder when concussed. Nevertheless, participants did not have a large increase in cardiovascular response. From this, the authors deducted that the lack of linear response of cardiovascular output and RPE suggests an impaired ability to shift from parasympathetic to sympathetic control over heart rate at the onset of exercise.
Although this article clarifies and quantifies the current state of a concussion rehabilitation tool, it may not fully capture the impact of concussion on autonomic regulation. Additionally, since this publication, a few other articles have been published investigating when it is clinically safe to do a BCTT without impacting recovery; some suggesting testing to be done when the patient is minimally or completely asymptomatic.
Care should be taken when administering the BCTT, but it can provide helpful information in determining when a patient is showing improvement in workload and training, especially with rehabilitation for back to sport.
> From: Hinds et al., J Neurol Neurophysiol 7 (2018-01-16 05:59:43) . All rights reserved to The Author(s). Click here for the online summary.