# The Effects of Short-Term High-Intensity Interval Training and Moderate Intensity Continuous Training on Body Fat Percentage, Abdominal Circumference, BMI and VO(2max) in Overweight Subjects PMID: 33467257 Journal: Journal of functional morphology and kinesiology Published: 2020-06-10 Authors: Russomando L, Bono V, Mancini A, Terracciano A, Cozzolino F, Imperlini E, Orrù S, Alfieri A, Buono P ## Question Does a 6-week, 3-days-per-week personalized supervised HIIT protocol improve body fat percentage, abdominal circumference, BMI, and VO2max compared with standard MICT in young overweight sedentary adults? ## Summary This small randomized trial compared six weeks of supervised personalized HIIT plus resistance training with a longer MICT plus resistance-training program in young overweight sedentary adults. Both groups improved body composition and estimated VO2max, with no significant training-by-time interaction. A secondary comparison of percent changes favored HIIT for VO2max and showed only a trend for greater fat-mass reduction. The protocol is useful for HIIT Play as a time-efficient, equipment-based interval template, but the evidence is limited by small sample size, estimated VO2max, and combined resistance training. ## Population - Young healthy overweight sedentary volunteers performing less than 60 minutes of exercise 1-2 times per week - Sample size: 20 - Age: Overall 24.9 +/- 2.9 years; HIIT 24 +/- 3 years; MICT 26 +/- 2 years - Sex: HIIT 3 male/7 female; MICT 4 male/6 female - Fitness level: Sedentary; baseline VO2max 38.1 +/- 2.2 mL/kg/min overall, 38.6 +/- 2.3 in HIIT and 37.6 +/- 2.1 in MICT - Health status: Healthy overweight adults; BMI 26.1 +/- 1 kg/m2 overall; Mediterranean-type diet without food restriction ## Methodology - Randomized controlled trial with pre/post assessments - 6 weeks - Supervised exercise training setting using resistance machines, jump box/stepper for HIIT, and treadmill for MICT - Randomized and controlled study design. ## Protocol - Personalized supervised HIIT plus resistance training. - Modality: Machine resistance training followed by jump-box/stepper interval training. - Work intervals: 30 seconds at 140% of maximum workload, targeting HR up to 90% predicted HRmax. - Recovery: 90 seconds active recovery at 25% of maximum workload, targeting HR up to 60% predicted HRmax. - Sets or repetitions: 4 x 120-second HIIT cycles after 20 minutes of resistance training. - Intensity: Personalized from YMCA-adapted test; HRmax predicted with Tanaka equation; resistance training at approximately 70% 1RM. - Session duration: 40 minutes: 6-minute warmup, 20-minute RT, 8-minute HIIT, 6-minute cooldown. - Frequency: 3 days/week. - Program length: 6 weeks. - Progression: HIIT workload increased by 5% every 2 weeks. - Moderate-intensity continuous training plus resistance training. - Modality: Machine resistance training followed by treadmill continuous cardiovascular training. - Work intervals: Continuous 30-minute treadmill session. - Sets or repetitions: 20 minutes resistance training then 30 minutes continuous treadmill training. - Intensity: MICT at 60-70% predicted HRmax; resistance training at approximately 70% 1RM. - Session duration: 60 minutes: 6-minute warmup, 20-minute RT, 30-minute MICT, 4-minute cooldown. - Frequency: 3 days/week. - Program length: 6 weeks. ## Outcomes ### Training completion Status: improved Seventeen of 20 participants completed training; the three dropouts were in the MICT group. HIIT and MICT participants who remained completed a similar number of sessions. HIIT 17.6 +/- 0.5 sessions; MICT 17.1 +/- 0.7 sessions out of 18; p=0.103. ### Training-related injury Status: no clear change No training-related injury was reported. ### BMI, body fat percentage, abdominal circumference, VO2max Status: improved Both HIIT and MICT improved the tested health-related parameters over time, but two-way ANOVA did not show a significant training-by-time interaction for any parameter. Training x time interaction p>0.05 for all parameters. ### VO2max percent change Status: improved Percent-change comparison favored HIIT for estimated VO2max. Delta mean percentage: MICT +3.2% vs HIIT +5.7%; p=0.05. ### Fat mass percent change Status: mixed Percent-change comparison showed a trend toward greater fat-mass percentage reduction with HIIT, but it did not meet conventional significance. Delta mean percentage: MICT -5.7% vs HIIT -8.2%; p=0.06. ### BMI and abdominal circumference percent change Status: no clear change Percent-change comparisons did not favor HIIT over MICT for BMI or abdominal circumference. BMI: MICT -4.3% vs HIIT -3.4%, p=0.28; abdominal circumference: MICT -1.6% vs HIIT -1.1%, p=0.30. ## Practical Insights - A very small total hard-work dose, 2 minutes per session, can be embedded in a 40-minute resistance-plus-HIIT workout and still target high intensity. - Compared with a 60-minute MICT-plus-RT protocol, this 40-minute HIIT-plus-RT protocol produced similar broad improvements and a stronger VO2max percent-change signal in a small sample. - Body-composition claims should be cautious: the key fat-mass comparison was a trend, and the training-by-time interaction was not significant. - Combining HIIT with resistance training is product-relevant for workout design but complicates attribution of outcomes to HIIT alone. ## Limitations - Small sample size of 20 randomized participants. - Three dropouts all occurred in MICT, leaving unequal completer groups. - HIIT was combined with resistance training, limiting attribution to interval training alone. - VO2max was estimated by walking test, not directly measured by maximal gas exchange. - Body fat percentage was estimated by girth equations, not imaging or DXA. - Participants were young healthy overweight adults, so findings may not generalize to older adults, obesity, or clinical populations. - No food restriction was imposed; dietary changes were self-reported rather than tightly controlled. ## Safety And Adherence - None of the recruited subjects reported any training-related injury. - The paper does not describe a detailed adverse-event monitoring protocol beyond injury reporting. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/33467257/) (pubmed) - [DOI](https://doi.org/10.3390/jfmk5020041) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739244/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.