The role of subsymptom threshold aerobic exercise for persistent concussion symptoms in patients with postconcussion syndrome: a systematic review

Key points

1. 01All 12 included studies reported symptom improvement with SSTAE, regardless of study design
2. 02No studies documented significant worsening of concussion symptoms or serious adverse events after starting exercise
3. 03Only 3 of the 12 studies were RCTs, and all had small sample sizes and low to moderate quality ratings
4. 04The most studied populations were children, adolescents, and young adults; evidence in older adults and those with medical comorbidities is limited
5. 05Targeting approximately 80% of the heart rate that provoked symptoms for 20 to 30 minutes, 3 to 5 days per week appears to be a reasonable starting protocol

How it was conducted

Design

Systematic review of experimental studies

Databases searched

MEDLINE (Ovid), PubMed, Embase, and CINAHL from inception to May 4, 2019

Studies included

12 studies: 3 RCTs, 2 case series, 6 cohort studies (1 retrospective, 4 prospective, 1 retrospective chart review), 1 pre-post pilot study

Participants

Pediatric and adult patients with a history of concussion from all causes with persistent symptoms lasting at least 4 weeks

Intervention

Sub-symptom threshold aerobic exercise (SSTAE), either as sole intervention or as major component of multimodal rehabilitation

Quality assessment

Downs and Black scale for RCTs (scores low to moderate); Newcastle-Ottawa Scale for cohort studies (mostly poor); NHLBI tool for before-after studies

What they found

• All 12 included studies reported a significant reduction in persistent post-concussion symptoms following SSTAE
• Chan et al. (RCT): active rehabilitation group had greater reduction in Post-Concussion Symptom Scale (PCSS) scores than usual care group (p value reported as significant); no adverse events related to protocol
• Dobney et al. (prospective cohort): within-group improvement in PCSS scores at follow-up compared to pre-intervention (p<0.05); significant improvements in all symptom clusters including physical, cognitive, emotional, and sleep-related symptoms (p<0.05)
• Gagnon et al. (case series): post-concussion symptoms significantly decreased post-intervention (p=0.0X); all participants returned to activity by end of the program (mean duration approximately 8 weeks)
• Grabowski et al. (retrospective cohort): statistically significant decreasing trend in total PCSS scores (p<0.05); maximum symptom-free heart rate on graded exercise test increased (p<0.05); BESS balance errors decreased (p<0.05); two instances of minor symptom exacerbation, resolved with exercise intensity adjustment
• No study documented significant worsening of concussion symptoms or serious adverse events after exercise initiation; few studies had robust adverse event monitoring systems
• The only fMRI study showed no significant difference in fMRI activation between the aerobic exercise group and healthy controls post-intervention
• RCT quality assessed by Downs and Black: low to moderate; cohort and other observational study quality assessed as poor by Newcastle-Ottawa Scale

Limitations

• Only 3 of 12 included studies were RCTs, all with small sample sizes and open-label designs, limiting certainty about efficacy
• Most studies were in children, adolescents, and young adults who were otherwise healthy; findings may not generalise to adults, non-athletes, or those with medical comorbidities
• Considerable variation in exercise protocols (intensity, duration, frequency, modality) across studies makes it difficult to identify an optimal prescription
• Many studies incorporated SSTAE as part of a broader rehabilitation programme, making it impossible to isolate the independent effect of aerobic exercise alone

Why it matters

For patients

People experiencing concussion symptoms lasting beyond 4 weeks may benefit from guided aerobic exercise kept below the level that triggers their symptoms, and available evidence suggests this is safe to try.

For clinicians

SSTAE, targeting approximately 80% of the heart rate that provoked symptoms for 20 to 30 minutes, 3 to 5 days per week, is a reasonable evidence-informed starting protocol for PCS, ideally confirmed via a supervised graded exercise test such as the Buffalo Concussion Treadmill Test.

For readers

This systematic review consolidates early evidence that prescribed aerobic exercise is a promising, safe departure from strict rest for persistent post-concussion syndrome, but higher-quality RCTs in diverse populations are still needed before strong clinical guidelines can be issued.