PMID 34858205

Research
All papers

Home-Based HIIT and Traditional MICT Prescriptions Improve Cardiorespiratory Fitness to a Similar Extent Within an Exercise Referral Scheme for At-Risk Individuals

Hesketh K, Jones H, Kinnafick F, Shepherd SO, Wagenmakers AJM, Strauss JA, Cocks M

Question

In an exercise referral scheme for at-risk individuals, does home-based HIIT improve cardiorespiratory fitness, adherence, compliance, and cardiometabolic outcomes more than traditional moderate-intensity continuous training?

Summary

This pragmatic exercise-referral-scheme trial let at-risk primary-care participants choose either 12 weeks of home-based bodyweight HIIT or traditional moderate-intensity continuous training. Home-HIIT was popular and improved cardiorespiratory fitness by a similar amount to MICT, with improvements maintained 3 months after the program. However, adherence was poor in both groups, early drop-off was higher in Home-HIIT, and MICT produced more favorable body-composition and blood-pressure findings. The study is highly relevant for real-world home HIIT but is not randomized.

Methodology

  • At-risk adults enrolled in a United Kingdom exercise referral scheme who selected either a structured MICT or Home-HIIT prescription.
  • 154 participants.
  • Home-based bodyweight intervals.
  • Work intervals: 1 minute: two bodyweight exercises for 30 seconds each with no rest between.
  • Recovery: 1 minute rest.
  • Intensity: >=80% predicted HRmax during intervals.
  • 8-18 minutes of interval/rest sequence plus 2-minute warm-up.
  • 3 sessions/week.
  • 12 weeks.
  • Pragmatic non-randomized patient-preference trial embedded in a United Kingdom exercise referral scheme.
  • Cardiorespiratory fitness, Body composition, Blood pressure, and Glucose tolerance were tracked.

Outcomes

VO2peak

Both Home-HIIT and MICT significantly improved relative VO2peak after 12 weeks and maintained significant improvements at follow-up; between-group differences were not significant.

Post: MICT +3.9 +/- 6.0 ml/kg/min, P<0.001; Home-HIIT +2.7 +/- 4.4, P<0.001; between P=0.130. Follow-up: MICT +2.9 +/- 5.1, P<0.001; Home-HIIT +2.0 +/- 5.7, P=0.015; between P=0.298.

Improved

Adherence and compliance

Adherence was poor in both groups and did not differ significantly; completed sessions were often compliant with the prescribed intensity.

Weekly adherence ITT: MICT 48 +/- 35%, Home-HIIT 39 +/- 36%, P=0.772. Per-protocol compliance: MICT 88 +/- 23%, Home-HIIT 82 +/- 23%, P=0.104.

Mixed

Drop-off

No exercise uptake and total drop-off were greater in Home-HIIT than MICT.

No exercise uptake: Home-HIIT n=27 vs MICT n=8. Total drop-off: Home-HIIT n=66 vs MICT n=32.

Safety concern

Body composition

MICT produced more favorable body-mass, BMI, and fat-mass changes than Home-HIIT; Home-HIIT showed less durable or no body-composition benefit.

Fat mass post: MICT -1.5 +/- 6.3 kg, P=0.010; Home-HIIT -0.2 +/- 2.0 kg, P=1.000; between P=0.030. BMI follow-up between-group P=0.001.

Mixed

Blood pressure

MICT reduced systolic, diastolic, and mean arterial pressure at follow-up; Home-HIIT did not improve blood pressure.

Follow-up systolic BP: MICT -6 +/- 9 mmHg, P<0.001; Home-HIIT +1 +/- 10, P=1.000; between P<0.001. Diastolic between P<0.001; MAP between P<0.001.

Mixed

Glucose and lipids

Fasting glucose, OGTT outcomes, and blood lipids were not improved in either group.

No significant within-group improvements in fasting glucose, OGTT measures, triglycerides, cholesterol, HDL, or LDL.

No clear change

Insights

  • Home bodyweight HIIT can be offered as a viable, popular option for at-risk adults who value time efficiency and convenience.
  • A simple 1-minute work / 1-minute rest progression from 4 to 9 intervals can produce CRF improvements, but adherence support is critical.
  • Home-HIIT should not be positioned as superior to MICT for cardiometabolic outcomes based on this study.
  • Workout apps should include lower-impact substitutions and adherence prompts because illness, injury, tiredness, motivation, and life demands affected participation.

Limitations

  • Participants self-selected intervention groups rather than being randomized.
  • Home-HIIT had lower baseline CRF than MICT.
  • No no-treatment comparator group.
  • Observed CRF variability exceeded the a priori estimate, so type II error cannot be ruled out.
  • Predicted HRmax rather than measured HRmax was used for prescription.
  • HR lag limits interpretation of short HIIT intervals.
  • Heart-rate monitors were provided for research and may have influenced motivation.
  • Dietary records were not collected.
  • Detailed eligibility criteria were in supplementary material and not extracted as explicit full paper evidence here.

Safety

  • Formal adverse-event counts were not reported.
  • Survey responses included illness or injury as reasons for missed sessions and need to adapt exercises.
  • Home-HIIT used impact exercises such as squat jumps, tuck jumps, burpees, and jumping jacks, which may require modification for some users.