Light Exercise is Specifically Prescribed
Aside from light aerobic exercise being the first stage of the return to sport protocol for athletes, light exercise is now effectively specifically prescribed as part of general concussion management. The available evidence suggests “light” or “low-intensity” exercise may actually significantly improve the speed of recovery from post-concussion symptoms. The specific mechanism of benefit is unknown but aerobic exercise training has known beneficial effects on autonomic nervous system regulation, cerebral blood flow regulation cardiovascular physiology, and brain neuroplasticity. In fact it may be one of the few, actual “therapies” that have RCT evidence of improving concussion recovery. Given the promising evidence, these guidelines recommend early initiation of low-risk, light physical activity from approximately 24–48 hours after injury. Even though most of the evidence of benefit was generated in studies of adolescent and young adult athletes, it seems reasonable to extrapolate and prescribe light exercise to sedentary people as well to aid concussion recovery with safety caveats. In particular, when describing exercise intensity recommendations, “light” or “low-intensity” exercise should be tailored to the individual i.e. what is “light” or “low-intensity” for them. e.g. for a sedentary person who does not usually exercise, light exercise may only be a comfortable walk. Additionally “physical activities that pose no or low risk of sustaining another mTBI/concussion (e.g. walking or stationary cycling) are advisable.” (Guideline 1).
Is Concussion Symptom Exacerbation with Exercise Acceptable?
Mild symptom exacerbation during exercise does not necessarily indicate harm or require return to strict rest. Given the potential therapeutic benefit of light exercise, Guideline 1 suggests that “physical activity should be started between 24 and 48 hours post injury, gradually increasing from low to moderate physical activity, provided that it is at a level that does not result in significant exacerbation of post- concussive symptoms. A small increase in symptoms is acceptable”.
What represents a mild exacerbation has been formally defined as no more than 2 points on a 0-10 symptom scale, based on the Amsterdam consensus of 2022 which appears derived from the source literature that demonstrated the benefits of exercise on concussion recovery, where trial participants were instructed to cease exercise if symptoms exacerbation exceeded this 2 point limit.
Unfortunately there is some internal inconsistency within the Amsterdam consensus and the two derived Australian guidelines about the acceptable duration of symptom exacerbation. Some sections define a ‘brief’ exacerbation as lasting less than 1 hour, whereas other sections simply emphasise return to baseline before the next exercise session or stage. Guideline 1 additionally describes activity-related symptom exacerbations resolving or improving within 24 hours as ‘transient’ and states that such transient worsening during gradual return to activity is common and safe.
The influential systematic review by Leddy et al that was extensively cited in the Amsterdam consensus, examining rest and exercise early after sport, when discussing the beneficial effects of physical activity on concussion recovery, merely states in regards to duration:
“Symptom exacerbation during PA, prescribed aerobic exercise and cognitive activity is typically brief (ie, less than an hour) and does not delay recovery”
This descriptive observation about the typical duration of symptom exacerbations appears subsequently to have been operationalised in the Amsterdam consensus as a <1-hour definition of ‘brief’, despite there being no clear evidence that 1 hour represents a biological or safety threshold.
Considering this, the following represents a reasonable summary of the source evidence and guidelines:
- Early physical activity with light exercise is recommended post injury to facilitate recovery
- Mild symptom exacerbations during physical activity (no more than 2 points on a 0-10 symptom scale) of symptoms are considered safe and acceptable. If exacerbation is more than mild, the exercise session should be ceased and restarted when symptoms settle.
- As most exercise-related exacerbations reported in the studies were brief (<1 hour), this can reasonably be used as a pragmatic target for a well-tolerated exercise dose, rather than as a validated safety threshold.
- If a mild exacerbation lasts longer than 1 hour but returns fully to baseline before the next planned exercise session, the available evidence does not clearly indicate that this is harmful or that exercise progression must be abandoned. Exercise can reasonably be resumed once symptoms have returned to baseline. Indeed the GRTSF of Guideline 2 only requires symptoms to “return to baseline prior to commencing the next activity or stage”. Consideration could be given to reducing the intensity or duration of the next exercise bout, if prolonged symptom exacerbation recurs.
The above describes a reasonable approach to both exercise during light intensity early activity as well as progression through the early stages of the GRTSF.
However at the advanced stages of the GRTSF, before progression to contact or other activities carrying a risk of head impact, the athlete should be symptom-free at rest and should not develop concussion symptoms during or after exertion.”
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