# Feasibility and efficacy of peak-velocity interval training vs. moderate-intensity walking training in people with multiple sclerosis with severe fatigue and walking impairment: A pilot randomized controlled trial PMID: 41418486 Journal: Multiple sclerosis and related disorders Published: 2026-02-01 Authors: Cleland BT, Jeng B, Brown N, Motl RW, Madhavan S ## Question Is peak-velocity interval walking training feasible and initially efficacious compared with moderate-intensity continuous walking training for people with multiple sclerosis who have elevated fatigue and walking dysfunction? ## Summary This pilot randomized controlled trial tested peak-velocity interval treadmill walking, a HIIT-style walking protocol, against moderate continuous walking in 12 people with multiple sclerosis, elevated fatigue, and walking impairment. Participants completed 12 sessions over about 5.5 weeks with 100% retention, high adherence, 100% intensity compliance, and no adverse events. PVIT achieved higher relative heart rates and greater relative walking velocity than MICT and improved VO2 peak more, but other walking, fatigue, and cognitive outcomes did not differ between groups. ## Population - Twelve people with multiple sclerosis, elevated fatigue, and walking dysfunction randomized to PVIT or MICT. - Sample size: 12 - Age: Mean 49.3 (7.4) years overall; PVIT 48.6 (7.4), MICT 50.4 (9.8). - Sex: 9 female and 3 male overall. - Fitness level: Clinical MS sample with impaired walking and low baseline aerobic fitness; PVIT baseline VO2 peak 16.6 (4.5), MICT 21.0 (3.1) mL/kg/min. - Health status: Multiple sclerosis, stable disease-modifying therapy, fatigue severity score >=4, PDDS 3-6. ## Methodology - Single-center, parallel-groups pilot randomized controlled trial. - 12 training sessions completed over about 5.5 weeks on average. - Brain Plasticity Laboratory at the University of Illinois Chicago. - Randomized and controlled study design. ## Protocol - Peak velocity interval training (PVIT). - Modality: Treadmill walking. - Work intervals: For each interval, speed ramped over 2 minutes to safe/tolerable peak velocity, then peak velocity held for 10 seconds. - Recovery: Walk at warm-up recovery velocity until HR was within 5 bpm of warm-up; if not recovered within 4 minutes, treadmill stopped and participant stood until HR recovered. - Sets or repetitions: Repeated intervals during sessions up to 40 minutes; exact count not reported. - Intensity: Peak safe/tolerable walking velocity; achieved 82.6 (7.8)% HRR across intervals/segments and 92% of intervals in vigorous HR range. - Session duration: Up to 40 minutes prescribed including pauses; observed walking time excluding rests/early stoppage 30.4 (10.0) minutes. - Frequency: 2-3 sessions per week. - Program length: 12 sessions. - Progression: Increase peak treadmill velocity when safely maintained; reduce 5-10% for instability, foot dragging, or excessive assistance. - Moderate-intensity continuous training (MICT). - Modality: Treadmill walking. - Work intervals: Continuous walking after warm-up. - Sets or repetitions: One continuous walking bout per session. - Intensity: 40-60% heart-rate reserve; HR continuously monitored and RPE assessed every 3 minutes. - Session duration: Up to 40 minutes prescribed; observed walking time excluding rests/early stoppage 37.1 (5.6) minutes. - Frequency: 2-3 sessions per week. - Program length: 12 sessions. - Progression: Treadmill velocity adjusted within and across sessions to maintain target HR range. ## Outcomes ### Feasibility Status: improved All enrolled participants were randomized and completed all testing and allocated training sessions; retention was 100%, overall adherence 86.1%, and intensity compliance 100%. PVIT adherence 84.5 (24.3)%, MICT 88.3 (9.5)%; retention 100% in both groups. ### Safety Status: improved No adverse events occurred in either group. ### Exercise intensity fidelity Status: improved PVIT achieved higher relative HR and peak velocity relative to maximal overground velocity than MICT; 92% of PVIT intervals achieved vigorous HRs. PVIT HRR 82.6 (7.8)% vs MICT 55.5 (14.1)%, p=0.002; peak velocity relative to maximal overground velocity 95 (41)% vs 70 (12)%, p<0.001. ### VO2 peak Status: improved VO2 peak improved more in PVIT than MICT: PVIT increased 2.3 mL/kg/min (13.8%) compared with MICT 0.4 mL/kg/min (1.0%). t(10)=2.2, p=0.05; Cohen's d 0.47 for PVIT and 0.10 for MICT. ### Walking, fatigue, and cognition Status: no clear change Between-group changes did not differ for comfortable or maximal 10MWT, 6MWT, FSS, SDMT, or CVLT-II. Other outcomes t<=1.9, p>=0.09; Z<=1.9, p>=0.07. ### Session duration and distance Status: mixed PVIT had shorter walking duration, more pause/rest duration, and less distance covered than MICT. Session duration 30.4 (10.0) vs 37.1 (5.6) min, p<0.001; pause/rest 3.6 (3.7) vs 1.1 (1.8) min, p<0.001; distance 1285 (780) vs 2167 (1085) m, p<0.001. ## Practical Insights - In a supervised clinical setting, individualized peak-velocity walking intervals can be feasible for people with MS who have fatigue and walking impairment. - Clinical HIIT may need flexible scheduling, HR recovery-based rests, and safety regressions rather than rigid session timing. - Higher intensity may improve aerobic fitness even with less total walking time and distance, but walking, fatigue, and cognitive benefits remain uncertain. ## Limitations - Pilot sample of 12 participants. - Planned sample was 20, but study stopped after interim analysis. - No long-term follow-up. - Trainers and participants could not be fully blinded. - Duration compliance was 60%, and PVIT had less walking time than MICT. - Flexible weekly dose improved real-world practicality but limited methodological rigor. - Requires supervised treadmill safety setup. ## Safety And Adherence - No adverse events occurred. - Participants wore a harness without body-weight support and could hold handrails. - Participants had to pass a graded exercise stress test. - PVIT included HR recovery criteria and treadmill stopping if HR did not recover within 4 minutes. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/41418486/) (pubmed) - [DOI](https://doi.org/10.1016/j.msard.2025.106930) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12926876/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.