# Preliminary Outcomes of Combined Treadmill and Overground High-Intensity Interval Training in Ambulatory Chronic Stroke PMID: 35185766 Journal: Frontiers in neurology Published: 2022-02-04 Authors: Boyne P, Doren S, Scholl V, Staggs E, Whitesel D, Carl D, Shatz R, Sawyer R, Awosika OO, Reisman DS, Billinger SA, Kissela B, Vannest J, Dunning K ## Question To assess preliminary outcomes of combined overground and treadmill locomotor HIIT in chronic hemiparetic stroke, including overground translation of treadmill speed gains, responsiveness of outcomes across gait, fitness, cognition, fatigue, subjective, and brain-volume domains, and moderation by baseline gait speed. ## Summary This small pilot study tested a combined overground and treadmill locomotor HIIT protocol in 10 ambulatory people more than six months after stroke. Participants completed a four-week no-intervention control phase followed by 12 supervised HIIT sessions over four weeks. Gait function, exercise capacity, fatigue, perceived change, and several other domains improved more during the treatment phase than during the control phase, and fastest overground gait speed improved by about 61% of the fastest treadmill speed gain. No serious adverse events occurred, but mild and moderate events such as soreness, fatigue, and lightheadedness were common in this clinical sample. ## Population - Ten ambulatory chronic stroke survivors more than six months post-stroke with gait speed below 1.0 m/s and substantial walking limitations; 10 matched healthy controls provided baseline comparison only. - Sample size: 10 - Age: Stroke participants mean 59.8 years, SD 6.8. - Sex: 4 female and 6 male stroke participants. - Fitness level: Low gait function and aerobic capacity: comfortable gait speed 0.41 m/s, six-minute walk distance 156 m, VO2peak 13.1 mL/kg/min. - Health status: Chronic unilateral middle cerebral artery territory stroke; screened to exclude significant treadmill ECG abnormalities and recent cardiopulmonary hospitalization. ## Methodology - Single-arm pilot study with a four-week no-intervention control phase followed by a four-week supervised locomotor HIIT treatment phase; healthy controls had baseline testing only. - Four-week no-intervention control phase plus four-week treatment phase with 12 HIIT sessions. - Cardiovascular stress laboratory, MRI research center, and rehabilitation research laboratory. - Controlled study design. ## Protocol - Combined overground and treadmill locomotor HIIT. - Modality: Overground corridor walking and treadmill walking. - Work intervals: Short sessions: 30-second maximum safe speed bursts; long sessions: 3-4 minute bursts at 90% peak heart rate. - Recovery: Short sessions: 30-60 seconds resting recovery; long sessions: 2-3 minutes active recovery at 70% peak heart rate. - Sets or repetitions: Not reported as a fixed repetition count; 40 minutes of HIIT blocks per session. - Intensity: Short intervals at maximum safe speed; long intervals at 90% peak heart rate, with actual mean HR 78-83% peak HR across modalities. - Session duration: 45 minutes. - Frequency: Approximately 3 sessions per week. - Program length: 4 weeks. - Progression: Progress speed, assistive device, or gait pattern as tolerated to maintain speed challenge or target HR. - No-intervention control phase. - Modality: No exercise intervention. - Program length: 4 weeks. ## Outcomes ### Overground translation of treadmill speed gains Status: improved Fastest overground gait speed improved by 0.16 m/s during treatment and fastest treadmill speed improved by 0.29 m/s; overground speed change averaged 61% of treadmill speed change. Treatment phase changes were significant for fastest overground gait speed and fastest treadmill speed; reported translation 95% CI 33-89%. ### Walking capacity Status: improved Six-minute walk distance increased by 31 m during treatment compared with -2 m during control. Treatment phase estimate 31 m [95% CI 16, 47]; significant treatment-versus-control phase difference. ### Exercise capacity Status: improved Ventilatory threshold and peak oxygen consumption each increased by 1.8 mL/kg/min during treatment. Ventilatory threshold treatment phase estimate 1.8 [0.6, 3.0]; peak oxygen consumption estimate 1.8 [1.2, 2.4]. ### Fatigue Status: improved PROMIS-Fatigue decreased during treatment, indicating less fatigue. Treatment phase estimate -4.8 T-score points [95% CI -9.1, -0.6]; significant treatment-versus-control phase difference. ### Safety Status: mixed No serious adverse events occurred, but 5 of 10 participants had intervention-related mild or moderate adverse events. 18 intervention-related adverse events: 15 grade 1 and 3 grade 2; 0 grade 3-5. ## Practical Insights - Task-specific overground intervals may improve transfer from treadmill speed gains to overground walking in chronic stroke rehabilitation. - Clinical HIIT for gait-impaired stroke survivors requires screening, supervision, fall-risk controls, and individualized speed progression. - Baseline walking speed may influence absolute gains and should be considered when setting expectations or designing trials. ## Limitations - Small sample size. - Not designed to test efficacy or effectiveness. - No randomized crossover order or randomized control group. - No active control intervention. - No adjustment for multiple statistical comparisons. - Limited generalizability to broader stroke populations. - Some outcome measures lacked rater blinding. ## Safety And Adherence - No serious adverse events occurred. - Intervention-related adverse events occurred in 5 of 10 participants. - Intervention-related soreness/pain, fatigue, and lightheadedness were reported. - Treadmill training used a fall-protection harness and participants were screened with treadmill ECG stress testing. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/35185766/) (pubmed) - [DOI](https://doi.org/10.3389/fneur.2022.812875) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8854218/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.