Reduced-exertion HIT (REHIT) in sedentary adults: three 10-min sessions a week with one or two 10-20 s all-out sprints, 6 weeks
VO2max +15% (men) / +12% (women), insulin sensitivity +28% (men)
Participants
n=29 healthy but sedentary young men and women, randomised to REHIT (n=15: 7 men, 8 women) or a control group (n=14: 6 men, 8 women) that kept its normal sedentary lifestyle.
Protocol
3 sessions per week for 6 weeks; each session 10 min in total.
Session content: low-intensity cycling at 60 W with short all-out sprints — one sprint in the first session, two in every later session; sprints lasted 10 s (week 1), then 15 s (weeks 2-3), then 20 s (last 3 weeks).
Tests before and 3 days after the programme: VO2max and the glucose/insulin response to a 75-g oral glucose load (OGTT).
Perceived exertion of the sessions: RPE 13 ± 1 (Borg 6-20) — "relatively low".
Key Findings
VO2max rose in the male training group (+15%) and the female training group (+12%), P < 0.01.
Insulin sensitivity rose by 28% in the male training group (P < 0.05); the abstract reports no significant change for the women.
The authors' conclusion: a feasible, genuinely time-efficient intervention improved metabolic health and aerobic capacity in sedentary people.
Practical Application
In 29 sedentary young adults, 6 weeks of three 10-min sessions a week, each holding only one or two 10-20 s all-out sprints, raised VO2max by 15% in men and 12% in women at a perceived exertion of just 13 ± 1 — a dose small enough to fit any week. The subjects were untrained, so for a trained cyclist this is the floor ("something beats nothing"), not a training-block prescription: a sedentary VO2max responds to almost any stimulus, a trained one does not.
Inference, not tested: in a collapsed week (illness recovery, travel, work), one or two 10-min sessions with a couple of all-out sprints is a defensible way to keep touching high intensity; expect maintenance at best, not the gains seen here.
Not from this paper: SIT versus continuous training in trained subjects is in REF-049; how sprint length (10 s vs 30 s) changes the response is in REF-050.
Limitations
Sedentary participants only; nothing in the study speaks to trained athletes.
6 weeks, two small groups; the abstract gives no data on the control group's change and no performance outcome.
Metabolic-health framing (insulin sensitivity, T2D risk), not endurance performance.
How this entry was checked and changed
Content correction 2026-09-27
"3 × 20 s all-out once per week, VO2max +2-3%, 15-20 min per session, trained cyclists need 5-8 efforts" -> the trial ran 3 sessions/week of 10 min with one or two 10-20 s sprints in 29 sedentary adults; VO2max rose 15% (men) and 12% (women); the trained-cyclist dosing was not from this paper and was removed.
Tier 2-3 -> Tier 0 (sedentary); type "Minimal dose study" -> parallel RCT with sedentary control.