# Combined low-volume high-intensity interval training and inspiratory muscle training in patients with metabolic syndrome: A randomized controlled trial PMID: 42071842 Journal: Medicine Published: 2026-04-24 Authors: Uyar H, Vardar-Yagli N, Saglam M, Calik E, Uyaroglu OA, Ozdede M, Durusu Tanriover M ## Question Does adding inspiratory muscle training to an 8-week low-volume HIIT programme produce greater improvements in cardiorespiratory fitness, metabolic syndrome parameters, and respiratory muscle function than low-volume HIIT alone in adults with metabolic syndrome? ## Summary In a randomized controlled trial of 38 adults with metabolic syndrome, participants were assigned to treadmill low-volume HIIT, low-volume HIIT plus inspiratory muscle training, or a lifestyle-advice control for 8 weeks. Both exercise groups performed 26-minute supervised treadmill HIIT sessions three times per week, using six 1-minute intervals at 90-100% VO2max with 2-minute active recoveries. VO2max, several cardiometabolic markers, and metabolic syndrome z-score improved in the exercise groups, while respiratory muscle strength and endurance improved mainly when inspiratory muscle training was added. One participant withdrew because of knee pain and no serious adverse events were reported. ## Population - Clinically stable adults with metabolic syndrome. - Sample size: 38 - Age: Mean about 50 +/- 5 years; abstract reports ages 42 to 60 years. - Sex: 67% women. - Fitness level: Low baseline VO2max, about 15.6-17.9 mL/kg/min across groups; no recent scheduled exercise program. - Health status: Metabolic syndrome; clinically stable with no recent medication changes and no recent cardiac events, heart failure, renal failure, peripheral vascular disease, or exercise intolerance. ## Methodology - Interventional, parallel-group, randomized controlled, double-blind trial with three groups: LVHIIT, LVHIIT plus IMT, and control. - 8 weeks. - Cardiopulmonary Rehabilitation Unit at Hacettepe University, Faculty of Physical Therapy and Rehabilitation, Ankara, Turkiye. - Randomized and controlled study design. ## Protocol - Low-volume HIIT with optional inspiratory muscle training. - Modality: Treadmill aerobic intervals; LVHIIT+IMT group also used inspiratory muscle training device. - Work intervals: 1 minute at 90-100% VO2max. - Recovery: 2 minutes active recovery at 50-70% VO2max. - Sets or repetitions: 6 intervals per session; IMT 60 inspiratory maneuvers twice daily in the combined group. - Intensity: Warm-up/cool-down 30-50% VO2max; intervals 90-100% VO2max; recovery 50-70% VO2max; IMT 50% MIP. - Session duration: 26 minutes for LVHIIT; IMT session duration not reported. - Frequency: 3 LVHIIT sessions/week; IMT twice daily for LVHIIT+IMT. - Program length: 8 weeks. - Progression: IMT load adjusted after MIP reassessment; LVHIIT progression not explicitly reported. - Lifestyle and physical activity advice control. - Modality: Advice only, including moderate-intensity aerobic activity recommendations such as brisk walking, cycling, or swimming. - Intensity: Recommended at least 150 minutes/week of moderate-intensity aerobic activity; no supervised exercise. - Frequency: Telephone reinforcement every 2 weeks. - Program length: 8 weeks. ## Outcomes ### VO2max Status: improved VO2max in mL/kg/min increased in LVHIIT from 15.57 +/- 4.78 to 19.98 +/- 4.40 and in LVHIIT+IMT from 16.26 +/- 3.77 to 20.57 +/- 1.85, with no change in controls. Group x time P = .005 for VO2max mL/kg/min; within-group P = .001 for LVHIIT and P = .002 for LVHIIT+IMT. ### MetS z-score Status: improved MetS z-score decreased from 4.55 +/- 4.30 to 0.10 +/- 2.50 in LVHIIT and from 3.17 +/- 2.73 to -0.95 +/- 2.65 in LVHIIT+IMT, with little change in controls. Group x time P = .000. ### Body composition and anthropometrics Status: improved Significant group x time interactions were observed for body weight, BMI, visceral fat ratio, waist circumference, and hip circumference; waist circumference decreased in both exercise groups but not control. Group x time P values: body weight .016, BMI .039, VFR .015, waist circumference .014, hip circumference .006. ### Glycemic markers and DBP Status: improved Fasting plasma glucose, HbA1c, and resting diastolic blood pressure improved in exercise groups, with no significant control change. Group x time P values: FPG .010, HbA1c .018, DBP .040. ### Respiratory muscle performance Status: improved MIP, MEP, and respiratory muscle endurance improved significantly only in the LVHIIT+IMT group. Group x time P values: MIP .049, %MIPpred .001, MEP .038, respiratory muscle endurance .000. ### Adherence and adverse effects Status: mixed All participants completed at least 87.5% of sessions; one participant withdrew due to knee pain and no serious adverse events were observed. ## Practical Insights - A six-by-one-minute LVHIIT protocol performed three times weekly can improve short-term VO2max in supervised adults with metabolic syndrome. - A total weekly LVHIIT time of about 78 minutes including warm-up and cool-down may be effective for short-term cardiometabolic improvements. - Adding IMT appears most relevant for respiratory muscle outcomes, not clearly for additional VO2max gains. - For app translation, VO2max intensity targets need practical alternatives such as RPE or heart-rate zones. ## Limitations - Small sample size. - Predominantly female sample limits generalizability to male patients with metabolic syndrome. - No IMT-only group, so independent IMT effects cannot be determined. - Short 8-week intervention. - No long-term follow-up. - Many outcomes are surrogate markers rather than clinical events. - Supervised treadmill setting limits direct generalization to unsupervised or bodyweight-only HIIT. ## Safety And Adherence - One LVHIIT+IMT participant withdrew due to knee pain. - No serious adverse events were observed during or after training. - Participants were monitored by a physiotherapist during supervised sessions and instructed to report symptoms or unusual events. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/42071842/) (pubmed) - [DOI](https://doi.org/10.1097/MD.0000000000048311) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13124325/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.