Muscle & mechanical loading · graded by use, three uses
REHIT / Sprint Interval Training
Cardiorespiratory fitness (measured VO2max The most oxygen the body can use during all-out exercise, a standard measure of aerobic fitness.) in inactive adults, REHIT protocol.
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How this letter has changedLatest: October 2026 · Corrected.
The B rested on two meta-analyses A study that pools the numbers from several trials into one combined estimate. of sprint and interval training in general (Sloth et al., PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 23889316; Milanović et al., PMID 26243014), which the record itself said did not test REHIT. A PubMed search found randomized trials of the REHIT protocol from three independent groups, all finding VO2max rose: Metcalfe et al. (Eur J Appl Physiol, 2012; PMID 22124524), Cuddy et al. (Int J Environ Res Public Health, 2019; PMID 30736402) and Hu et al. (J Exerc Sci Fit, 2025; PMID 40689309). The letter is unchanged and now rests on them. Insulin sensitivity and blood pressure are graded C.PMID 23889316 PMID 26243014 PMID 22124524 PMID 30736402 PMID 40689309
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REHIT is a short form of sprint exercise: two all-out sprints of 10 to 20 seconds in a session of about 10 minutes. In trials from three separate teams, inactive adults who did it 2 or 3 times a week raised their measured fitness. Results for blood sugar control were mixed, and it did not help men with type 2 diabetes. A blood pressure drop seen in one trial was not found in another. No trial measured lifespan or deaths.
The B belongs to one of the three uses graded on this record. The other two carry their own letters.
As studied, and the trials
Metcalfe et al. (Eur J Appl Physiol, 2012; PMID 22124524), Cuddy et al. (Int J Environ Res Public Health, 2019; PMID 30736402) and Hu et al. (J Exerc Sci Fit, 2025; PMID 40689309): three independent groups. B, not A, until blinded VO2max assessment is confirmed.
As studied, and the trials
Metcalfe et al. (Eur J Appl Physiol, 2012; PMID 22124524) found insulin sensitivity rose in men only; Ruffino et al. (Appl Physiol Nutr Metab, 2017; PMID 28121184) found no improvement in type 2 diabetes. Mixed: C.
As studied, and the trials
Cuddy et al. (Int J Environ Res Public Health, 2019; PMID 30736402) found systolic pressure fell more with REHIT than with moderate training; Ruffino et al. (Appl Physiol Nutr Metab, 2017; PMID 28121184) found no difference from walking. Not replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away. against a control: C.
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See the full evidence record →Graded on Cardiorespiratory fitness (measured VO2max) in inactive adults.
Why this gradeThe reasoning, and what the grade does not cover.
Grade B on measured VO2max in inactive adults doing the REHIT protocol. Randomized trials from three independent groups found it rose (Metcalfe et al., 2012; PMID 22124524; Cuddy et al., 2019; PMID 30736402; Hu et al., 2025; PMID 40689309).
WHY NOT AVO2max is an instrument-recorded function that could carry an A, but the published rule requires blinded trials, and no abstract reports that VO2max was assessed blinded.
WHAT THIS GRADE DOES NOT COVERinsulin sensitivity and glucose control, and blood pressure, which are graded C on their own evidence; longevity or mortality, which no REHIT trial measured; and any particular machine or app sold for the protocol.
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Each use, with its trials
This record carries a separate letter for each thing it has been measured on. The headline grade is the best of them, and it does not transfer to the others.
Metcalfe et al. (Eur J Appl Physiol, 2012; PMID 22124524), Cuddy et al. (Int J Environ Res Public Health, 2019; PMID 30736402) and Hu et al. (J Exerc Sci Fit, 2025; PMID 40689309): three independent groups. B, not A, until blinded VO2max assessment is confirmed.
Metcalfe et al. (Eur J Appl Physiol, 2012; PMID 22124524) found insulin sensitivity rose in men only; Ruffino et al. (Appl Physiol Nutr Metab, 2017; PMID 28121184) found no improvement in type 2 diabetes. Mixed: C.
Cuddy et al. (Int J Environ Res Public Health, 2019; PMID 30736402) found systolic pressure fell more with REHIT than with moderate training; Ruffino et al. (Appl Physiol Nutr Metab, 2017; PMID 28121184) found no difference from walking. Not replicated against a control: C.
The evidence, in fullSeven papers, each linked to its PubMed record.
Metcalfe et al. (European Journal of Applied Physiology, 2012; PMID 22124524): 29 sedentary adults, 6 weeks of REHIT or control; VO2max rose 15% in men and 12% in women. Cuddy et al. (International Journal of Environmental Research and Public Health, 2019; PMID 30736402): 32 inactive adults, 8 weeks; fitness rose 12% with REHIT and 7% with moderate continuous training. Hu et al. (Journal of Exercise Science and Fitness, 2025; PMID 40689309): 319 inactive men; REHIT cycling and burpee versions each raised VO2max 8% to 13% against a non-exercising control. Metcalfe et al. (BMC Public Health, 2020; PMID 32164631): the gain held unsupervised in 25 office workers. Ruffino et al. (Applied Physiology, Nutrition, and Metabolism, 2017; PMID 28121184): 16 men with type 2 diabetes; no improvement in insulin sensitivity or glucose. Background, not REHIT: Sloth et al. (Scandinavian Journal of Medicine and Science in Sports, 2013; PMID 23889316), sprint interval training, 19 studies of which 4 were randomized; Milanović et al. (Sports Medicine, 2015; PMID 26243014), interval training in adults aged 18 to 45. Grade B on measured VO2max, an instrument-recorded function; it is not A because no abstract confirms blinded assessment.
VO2max at baseline and every 8 weeks: this is the primary endpoint The one outcome a trial names in advance as its main test. Results on other outcomes carry less weight. in the CAROL Bike REHIT trials. Resting heart rate monthly and fasting glucose quarterly for the metabolic benefit documented in the T2D risk trials. The protocol is two 20-second all-out sprints within an 8.5-minute session, three times per week: substituting longer moderate sprints does not replicate the REHIT stimulus.
Evidence notes: randomized trial, meta-analysis
Endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. graded: Cardiorespiratory fitness (measured VO2max) in inactive adults (functional)
Last reviewed: October 2026
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
Primary evidenceSeven papers, each linked to its PubMed record.
Metcalfe et al. (European Journal of Applied Physiology, 2012; PMID 22124524): 29 sedentary adults, 6 weeks of REHIT or control; VO2max rose 15% in men and 12% in women. Cuddy et al. (International Journal of Environmental Research and Public Health, 2019; PMID 30736402): 32 inactive adults, 8 weeks; fitness rose 12% with REHIT and 7% with moderate continuous training. Hu et al. (Journal of Exercise Science and Fitness, 2025; PMID 40689309): 319 inactive men; REHIT cycling and burpee versions each raised VO2max 8% to 13% against a non-exercising control. Metcalfe et al. (BMC Public Health, 2020; PMID 32164631): the gain held unsupervised in 25 office workers. Ruffino et al. (Applied Physiology, Nutrition, and Metabolism, 2017; PMID 28121184): 16 men with type 2 diabetes; no improvement in insulin sensitivity or glucose. Background, not REHIT: Sloth et al. (Scandinavian Journal of Medicine and Science in Sports, 2013; PMID 23889316), sprint interval training, 19 studies of which 4 were randomized; Milanović et al. (Sports Medicine, 2015; PMID 26243014), interval training in adults aged 18 to 45. Grade B on measured VO2max, an instrument-recorded function; it is not A because no abstract confirms blinded assessment.
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AI-controlled resistance matching that produces the Norwegian 4×4 VO₂max stimulus in 8:40/session. Published RCT Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect.: equivalent VO₂max improvement to 150 min/week moderate cycling. Most time-efficient VO₂max protocol studied.
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("reduced-exertion"[tiab] OR REHIT[tiab] OR "reduced exertion"[tiab]) AND (interval[tiab] OR sprint[tiab])Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →