# Effect of high-intensity interval training on cardiometabolic component risks in persons with paraplegia: Results of a randomized controlled trial PMID: 38924175 Journal: Experimental physiology Published: 2024 Aug Authors: Farrow M, Maher J, Deere R, Spellanzon B, Williams S, Thompson D, Bilzon JLJ ## Question Does a 6-week home-based upper-body HIIT intervention improve fasting insulin, peak aerobic capacity, peak power output, and other cardiometabolic component risks in persons with chronic paraplegia compared with maintaining habitual diet and physical activity? ## Summary This randomized controlled trial tested 6 weeks of home-based upper-body HIIT in adults with chronic paraplegia. The program was feasible and had very high compliance with no adverse events reported, and it improved peak power output and postprandial Matsuda insulin sensitivity compared with a habitual-lifestyle control group. It did not improve fasting insulin, VO2peak, body composition, resting blood pressure, lipids, inflammatory markers, or most psychological and functional outcomes. ## Population - Adults with chronic paraplegia from spinal cord injury, wheelchair users for more than 75% of waking hours. - Sample size: 27 - Age: HIIT 46 +/- 9 years; control 45 +/- 7 years. - Sex: 13 male and 14 female overall; HIIT 9/9 male/female, control 4/5 male/female. - Fitness level: Wheelchair users with chronic SCI; 20 of 27 completers had above-average baseline VO2peak for untrained SCI reference values. - Health status: Chronic paraplegia more than 1 year post-injury, with high prevalence of cardiometabolic risk factors at baseline. ## Methodology - Randomized controlled trial with 2:1 allocation to home-based upper-body HIIT or waiting-list habitual-lifestyle control. - 6 weeks - Home-based arm-crank HIIT with baseline and follow-up laboratory assessments at the DisAbility Sport & Health laboratory, University of Bath. - Randomized and controlled study design. ## Protocol - Home-based upper-body HIIT. - Modality: Arm-crank ergometry. - Work intervals: 60 seconds. - Recovery: 60 seconds at about 5 W. - Sets or repetitions: 10 intervals. - Intensity: 80%-90% HRpeak, progressed by 5% every 2 weeks. - Session duration: 30 minutes. - Frequency: 4 sessions/week. - Program length: 6 weeks. - Progression: 80% HRpeak weeks 1-2, 85% weeks 3-4, 90% weeks 5-6. - Habitual-lifestyle control. - Modality: No prescribed exercise intervention. - Program length: 6 weeks. ## Outcomes ### Peak power output Status: improved PPO was higher in HIIT than control at follow-up; authors report HIIT increased PPO by 12% while control was almost unchanged. HIIT 101 W (97-106) vs control 90 W (83-96) at follow-up; P=0.006, Cohen's d=1.37. ### Matsuda insulin sensitivity index Status: improved Postprandial Matsuda insulin sensitivity was higher after HIIT than control. HIIT 5.42 (4.69-6.15) vs control 3.75 (2.46-5.04) at follow-up; P=0.036, d=1.24. ### Fasting insulin Status: no clear change No between-group difference in fasting insulin at follow-up. P=0.415, d=0.39. ### Relative VO2peak Status: no clear change No between-group difference in relative peak aerobic capacity. HIIT 19.1 mL/kg/min (17.9-20.3) vs control 18.3 (16.5-20.0); P=0.417, d=0.37. ### Body composition and resting blood pressure Status: no clear change No between-group differences in body mass, BMI, waist, waist:hip ratio, body fat percentage, fat mass, fat-free mass, resting HR, systolic BP, or diastolic BP. All reported P values >0.05. ### Fasting blood biomarkers Status: no clear change No between-group differences in HOMA2-IR, glucose, triglycerides, total cholesterol, HDL-C, LDL-C, NEFA, leptin, adiponectin, CRP, lymphocytes, or neutrophils. All reported P values >0.05; IL-6 was not included because 18 participants were below the standard curve. ### Adherence and safety Status: improved The home-based HIIT program had high compliance and no adverse events reported. 98% compliance; no adverse events over 425 home-based exercise sessions. ## Practical Insights - For adaptive HIIT in chronic paraplegia, a 10 x 60-second arm-crank format can be feasible at home when paired with monitoring, check-ins, and safety screening. - Short upper-body HIIT may improve upper-body power even when VO2peak and most cardiometabolic markers do not change. - Heart-rate targets alone may underrepresent or misclassify intensity in people with spinal cord injury; RPE should be considered alongside HR. - Programs should monitor whether prescribed HIIT displaces habitual light activity, especially in low-activity clinical populations. ## Limitations - Small final sample and under-recruitment relative to planned sample size. - Missing venepuncture and cannulation data reduced sample size for blood and OGTT outcomes. - Short 6-week duration. - No moderate-intensity exercise comparator. - Control group changes in physical activity may have confounded results. - Heart-rate-based prescription was difficult for some participants and may vary by injury level. ## Safety And Adherence - No adverse events were reported to the research team. - Two HIIT participants dropped out due to pressure sores unrelated to the intervention. - Participants were monitored during and after exercise testing and the first home HIIT session for symptoms including chest pain, headache, visual changes, dizziness, and light-headedness. - Participants had to be accompanied by an adult for home exercise sessions. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/38924175/) (pubmed) - [DOI](https://doi.org/10.1113/EP091803) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11291867/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.