Neurology: Young people with concussion, why does exercise aggravate symptoms

In the past ten years, the treatment guidelines for concussions have evolved from [rest until symptoms disappear] to [progressive exercise]
.

However, because exercise may trigger or aggravate concussion symptoms, it is challenging to determine the precise amount or intensity of exercise required to cause a therapeutic effect

In addition, the exact mechanism of the exacerbation of exercise-related symptoms is still largely hypothetical, and clinical decision-making regarding exercise recommendations remains challenging
.

Few studies have studied the physiological response to acute exercise after a concussion

Although many factors may be the basis of these mechanisms, changes in vascular response during exercise may be one of them
.

These include changes in the effects of changes in arterial carbon dioxide on cerebral blood flow

Blood vessel

Previous work has shown that compared with healthy controls, people who have experienced a concussion have a higher resting cerebrovascular sensitivity (cerebrovascular activity) to arterial carbon dioxide, and its level is proportional to the acute and chronic resting symptoms
.

Therefore, during exercise, the cerebrovascular is more sensitive to the increase of carbon dioxide, which may lead to an increase in cerebral blood flow, exceeding the level of meeting metabolic requirements, which may be the basis for the aggravation of exercise-related symptoms

Although there are observational support from case studies, there are few experimental studies on the mechanism of cerebral vascular activity after a concussion, the response of cerebrovascular to aerobic exercise, and the aggravation of exercise-related symptoms
.

However, there are few experimental studies on the mechanism link between cerebral vascular activity, cerebrovascular response to aerobic exercise and exacerbation of exercise-related symptoms after a concussion
.

In this way, David R Howell of Childrens Hospital Colorado in the United States tried to define the cardiopulmonary and cerebrovascular reactions of adolescents and young people with or without concussion during acute exercise, and whether these reactions are related to the aggravation of symptoms
.

They recruited participants with recent concussions from the exercise concussion clinic from January 9, 2018 to February 22, 2020
.

If their concussion occurred <3 weeks before the initial test and they had symptoms at rest, they were included

Participants completed a progressive, symptomatically restricted, sub-maximum exercise program on stationary bicycles
.

They also assessed the heart rate, blood pressure, end-tidal carbon dioxide ratio (FETCO2), middle cerebral artery blood flow (CBF), and cerebral vascular function (vascular activity and autoregulation) during sitting, resting and exercising

They performed a total of 107 exercise tests (40 concussion patients, 37 healthy participants initially; 30 concussion patients followed up)
.

Concussion participants were initially tested (mean = 17.

Participants in the control group (average = 18.
3 ± 2.
4 years; 62% were women) underwent a test
.

During the whole exercise process, FETCO2 increases with the increase of heart rate, reaches a plateau, and decreases at higher exercise intensity
.
Carbon dioxide explained more than 25% (R2>0.
25; P<0.
01) of the change in resting CBF for most people (73%)
.

In the concussion group, the severity of resting symptoms and the heart rate when FETCO2 reached plateau explained two-thirds of the change in the exacerbation of exercise-induced symptoms (R2 = 0.
65; FETCO2 β = -1.
210 ± 0.
517 [SE], P<0.
05 )
.

There is a moderate and statistically significant relationship between the response of the cerebral blood vessels to carbon dioxide (cerebrovascular activity) and the response of the cerebral blood vessels to exercise-induced FETCO2 changes (R2=0.
13, P=0.
01)
.

The important significance of this study lies in the discovery that in aerobic exercise after a concussion, the relationship between arterial carbon dioxide response and aggravation of symptoms may be mediated by the increased sensitivity of cerebrovascular to exercise-related carbon dioxide increase
.

Original Source:
Howell DR, Hunt DL, Aaron SE, Hamner JW, Meehan WP, Tan CO.
Association of Hemodynamic and Cerebrovascular Responses to Exercise With Symptom Severity in Adolescents and Young Adults With Concussion .
Neurology.
Published online October 11, 2021:10.
1212 /WNL.
0000000000012929.
doi:10.
1212/WNL.
0000000000012929

Association of Hemodynamic and Cerebrovascular Responses to Exercise With Symptom Severity in Adolescents and Young Adults With Concussion

Leave a message here