Body composition, cardiorespiratory fitness, and neuromuscular adaptations induced by a home-based whole-body high intensity interval training
Question
Does 8 weeks of home-based, video-directed whole-body HIIT improve body composition, cardiorespiratory fitness, and neuromuscular function in healthy adults who are below physical activity recommendations?
Summary
This randomized controlled study tested an 8-week video-directed, home-based whole-body HIIT program in insufficiently active healthy young adults. Compared with a non-exercise control group, the HIIT group improved VO2peak, ventilatory threshold, leg lean mass, dynamic and isometric leg strength, and isometric endurance, while total fat mass and most fat measures did not change.
Methodology
- Twenty-eight healthy insufficiently active adults completed the study, with 14 in WB-HIIT and 14 in control.
- 28 participants.
- Bodyweight whole-body exercises delivered by video.
- Work intervals: 30 seconds all-out.
- Recovery: 30 seconds active recovery jogging on the spot.
- Intensity: All-out; achieved mean HR 74 +/- 5% HRmax and maximal HR 88 +/- 5% HRmax.
- 3-minute warm-up plus 12-16 minutes conditioning plus a few minutes stretching.
- 3 sessions/week.
- 8 weeks.
- Randomized controlled trial with two groups and pre-post repeated measures.
- VO2peak, First ventilatory threshold, Body composition, and Dynamic leg strength were tracked.
Outcomes
VO2peak
WB-HIIT increased VO2peak by about 5%; absolute VO2peak rose from 2.35 +/- 0.51 to 2.46 +/- 0.50 L/min, while control changed from 2.25 +/- 0.69 to 2.20 +/- 0.71 L/min.
Within WB-HIIT p=0.031; time x group p=0.012.
First ventilatory threshold
VO2 at VT1 rose in WB-HIIT from 1.31 +/- 0.33 to 1.56 +/- 0.36 L/min and did not change in control.
Within WB-HIIT p=0.002; time x group p=0.012 for absolute VT1 and p=0.006 for relative VT1.
Body composition
Leg lean mass increased from 16.6 +/- 2.7 to 17.1 +/- 2.6 kg in WB-HIIT, but fat mass and most other lean mass measures did not change.
Leg lean mass within WB-HIIT p=0.022; time x group p=0.014.
Leg strength and muscle endurance
WB-HIIT improved 3-RM leg press, MVC torque, and isometric endurance time.
3-RM time x group p=0.009; MVC torque time x group p=0.001; endurance time improved within WB-HIIT.
Training intensity relationship
More time above 80% HRmax was associated with greater absolute and relative VO2peak change.
rs=0.56; p=0.049 for absolute VO2peak and p=0.048 for relative VO2peak.
Insights
- A home bodyweight HIIT protocol can be built around 30-second all-out intervals with equal active recovery and progressive exercise variants.
- For healthy insufficiently active young adults, 3 weekly sessions over 8 weeks can improve aerobic fitness and neuromuscular performance.
- Do not overstate fat-loss effects from this protocol; DXA fat outcomes were largely unchanged.
- Intensity fidelity matters: time above 80% HRmax was associated with VO2peak improvement.
Limitations
- Small sample.
- Young healthy insufficiently active adults only.
- No blinding of participants or investigators during intervention and assessments.
- No long-term follow-up.
- Early exercise dropouts were replaced.
- Heart-rate zones used age-predicted HRmax.
Safety
- Three early WB-HIIT participants discontinued after a few sessions; two due to health problems unrelated to the study and one due to lack of time.
- Participants with conditions limiting maximal tests or training were excluded.
- Heart rate was monitored during sessions and participants could contact investigators for difficulties.