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.