The evidence behind
the threshold.
For two decades, prescribed sub-symptom-threshold aerobic exercise has moved from “rest in a dark room” to a tested, individualised treatment. Here’s what the research actually shows — and how this app helps it.
~48%
lower risk of persistent symptoms when sub-symptom aerobic exercise is started within ~10 days of injury, vs a stretching placebo (Leddy et al.).
13 vs 17
median days to recovery — aerobic-exercise group vs stretching group in adolescents with sport-related concussion.
<135 bpm
an example heart-rate threshold — a value this low on the test is associated with a higher risk of prolonged recovery, so the dose is also prognostic.
Find the threshold (the Buffalo test)
The Buffalo Concussion Treadmill/Bike Test adapts a cardiac stress test to stress the brain instead of the heart. Effort is raised by the minute while heart rate and symptoms are tracked; the heart rate at which symptoms first intensify is the Heart-Rate threshold (HRt) — a validated measure of exercise tolerance after concussion.
Prescribe a sub-symptom band
Trials prescribe aerobic exercise at roughly 80–90% of the HRt — hard enough to stimulate recovery, low enough to stay under the symptom threshold. The dose is about 20 minutes a day, most days of the week, individualised to each patient. Some apps prescribe from an age formula (a fixed percentage of 220 − age). SST Trainer prescribes from your patient’s measured threshold.
Structure each session
A session is built as a 5–10 minute warm-up, ~20 minutes of steady aerobic work held under the threshold, then a 5–10 minute cool-down — using any mode the patient prefers (walking, stationary bike, light jog).
Re-test and progress
Because the brain heals, the threshold rises. Protocols re-test every 1–2 weeks and lift the prescription accordingly, stopping when exercise tolerance normalises. Symptoms rising 2+ points in a session is the signal to stop and rest.
Where the dose comes from
The whole method turns on one number: the heart rate just below which symptoms intensify. It is individual, and how a tool obtains it is what separates them. SST Trainer measures it with a symptom-limited graded exertion test — the Buffalo test — for each patient. By contrast, the leading commercial concussion-rehab app, Rhea, prescribes from age-predicted maximum heart rate: the published CARE protocol it delivers targeted 55–65% of a fixed 220 − age, with no graded test to individualise the dose. An age formula can miss a given patient’s measured threshold by 10 bpm or more. To our knowledge, no published digital concussion-rehab programme prescribes from each patient’s own measured threshold — the dose is estimated. Measuring it, then holding the patient to it with verified live heart rate, is the gap this design fills.
ESTIMATED · AGE FORMULA
Dose set as a fixed share of 220 − age — the same formula for every patient of a given age, with no graded test (Chizuk et al. 2025; Hutchison et al. 2023).
MEASURED · GRADED TEST
Dose set just below the patient’s own measured heart-rate threshold, re-measured as they recover (Leddy & Willer 2013; Leddy et al. 2019).
Two safeguards sit on top of the measured band: progression is verification-gated — the band advances only on live, verified wearable sessions and is capped at the measured threshold, so it never ratchets up on an unverified number — and the clinician reads a serial trajectory of measured thresholds, not a self-reported symptom log. To our knowledge, no other commercial concussion app combines a measured heart-rate threshold, verification-gated training, and a serial measured-HRt clinician trajectory. The sub-symptom-threshold protocol itself is endorsed by the 6th International Consensus on Concussion in Sport and supported by randomised-trial evidence (Patricios et al. 2023; Leddy et al. 2019).
Progressive, not protective
This is graded exposure that lifts a ceiling as you heal — the opposite of pacing apps that help you avoid exertion. Different mechanism, different goal.
THIS APP · PROGRESSION
Train just under your symptom threshold; the band steps up as you recover. Drives the recovery forward.
RECALL APPS · PROTECTION
Stay inside an energy envelope to avoid crashes. Tells you when to stop, not how to progress.
Scope: progressive sub-symptom exercise is evidence-based for concussion / mTBI and exercise-intolerant recovery, under clinician oversight. It is not appropriate for every condition — graded exertion is contraindicated in some (e.g. ME/CFS, where pacing is indicated). Always follow your clinician.
Key references
The published protocol
Lewis, Z. (2026). A Standardised Clinical Protocol for Sub-Symptom-Threshold Aerobic Exercise Rehabilitation after Concussion (mild Traumatic Brain Injury). Zenodo. CC-BY-4.0.
The citable, peer-reviewable standard of the method this platform delivers — the clinical spine of the Concussion Rehab Mastery course, referenced to a 136-item evidence base.
doi.org/10.5281/zenodo.21482634 →Leddy JJ, Willer B, et al. Early Subthreshold Aerobic Exercise for Sport-Related Concussion: a randomized clinical trial. JAMA Pediatrics, 2019.
Leddy JJ, et al. Early targeted heart-rate aerobic exercise vs placebo stretching for sport-related concussion in adolescents: a randomised controlled trial. The Lancet Child & Adolescent Health, 2021.
Haider MN, Leddy JJ, Willer BS, et al. Exercise for Sport-Related Concussion and Persistent Postconcussive Symptoms (review). Sports Health, 2021.
Haider MN, Leddy JJ, Wilber CG, et al. The Predictive Capacity of the Buffalo Concussion Treadmill Test after Sport-Related Concussion in Adolescents. Frontiers in Neurology, 2019 (HRt <135 bpm and ΔHR ≤50 bpm predict prolonged recovery).
Popoli DM, Leddy JJ, et al. Practical Management: A Standardized Aerobic Exercise Program for Adolescents with Concussion in the Absence of Graded Exercise Testing. Clinical Journal of Sport Medicine, 2023.
Janssen A, Pope R, Rando N. Clinical application of the Buffalo Concussion Treadmill Test and Bike Test: a systematic review, 2022.
Leddy JJ, et al. A preliminary study of sub-symptom threshold exercise training for refractory post-concussion syndrome. Clinical Journal of Sport Medicine, 2010.
Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport — Amsterdam, October 2022. British Journal of Sports Medicine, 2023.
Chizuk HM, et al. Evaluating User Experience and Satisfaction in a Concussion Rehabilitation App (Rhea): a Usability Study. JMIR Formative Research, 2025.
Hutchison MG, Di Battista AP, Loenhart MM. A Continuous Aerobic Resistance Exercise (CARE) Protocol for Concussion Rehabilitation Delivered Remotely via a Mobile App: a Feasibility Study. JMIR Formative Research, 2023.
Summaries are educational and not a substitute for clinical judgement. This app is a clinician-directed coaching and tracking tool — not a diagnosis or a return-to-play clearance.
Put the evidence on the wrist.
The protocol your clinic already trusts, delivered to the wearable your patient already owns — with the structure and between-visit visibility that carries a patient through their whole episode of care, re-test by re-test, rather than dropping off after the second visit.