REF-1328 · Church et al., 2007 · JAMA · Paper · PubMed

Do short easy sessions count?

In a trial of 464 sedentary women (102 controls; number analysed not in the abstract), 72, 136 and 192 min a week at 50% of VO2peak raised peak VO2 4.2%, 6.0% and 8.2% over controls. Not athletes (A).

Main caveat: Abstract only. The number analysed, dropouts by arm, session frequency and mode, adherence and the SDs of change could not be checked.
strong evidenceMeasured on non-athletes

Church, Earnest, Skinner and Blair tested how fitness responds to different weekly amounts of exercise at the same intensity.

In the Dose-Response to Exercise in Women (DREW) trial, 464 sedentary, postmenopausal, overweight or obese women with systolic blood pressure of 120.0-159.9 mm Hg, enrolled in the Dallas area from April 2001 to June 2005, were randomised to a non-exercise control group (102) or to exercise expending 4 kcal/kg (155), 8 kcal/kg (104) or 12 kcal/kg (103) a week for 6 months — 50%, 100% and 150% of the NIH Consensus Development Panel's recommended dose.

Every exercise group trained at the heart rate of 50% of the woman's peak VO2. Weekly exercise time averaged 72.2, 135.8 and 191.7 min. Baseline peak absolute VO2 was 1.30 ± 0.25 L/min. After adjustment for age, race or ethnicity, weight and peak heart rate, peak VO2 rose by 4.2%, 6.0% and 8.2% compared with controls (P < .001 for each; P for trend < .001).

The response did not differ by age, BMI, weight, baseline fitness, race or ethnicity, or hormone therapy; blood pressure did not change.

Our reading: this is the cleanest dose-response in the base for easy exercise volume at a fixed low intensity, and even the lowest dose, about 70 min a week, moved fitness in sedentary women; per minute the gain shrank slightly as the dose grew (our arithmetic). It says nothing about trained athletes, and the abstract does not report individual responses.

Protocol

Participants: n = 464 randomised; sedentary, postmenopausal, overweight or obese (BMI 25.0-43.0) women with systolic blood pressure 120.0-159.9 mm Hg; enrolled April 2001 to June 2005, Dallas, Texas.
Arms: non-exercise control (n = 102); 4 kcal/kg/week (n = 155); 8 kcal/kg/week (n = 104); 12 kcal/kg/week (n = 103) — 50%, 100% and 150% of the NIH consensus dose.
Intensity: target heart rate associated with 50% of each woman's peak VO2, the same in all exercise arms.
Duration: 6 months.
Primary outcome: peak absolute VO2 (L/min) on a cycle ergometer; analysis adjusted for age, race or ethnicity, weight and peak heart rate. Blood pressure also reported.
Not in the abstract: sessions per week, mode of training, supervision, adherence, dropouts and the number analysed, SDs of change.
Registration: ClinicalTrials.gov NCT00011193.
Funding and interests: NIH, National Heart, Lung, and Blood Institute (grant HL66262, in the PubMed and Europe PMC records); conflicts of interest are not stated in the abstract or the PubMed record.

Key Results

Arm (energy per week)RandomisedExercise time, min/week, mean (SD)Peak VO2 change vs control
Control102——
4 kcal/kg (50% of the NIH dose)15572.2 (12.3)+4.2% (P < .001)
8 kcal/kg (100%)104135.8 (19.5)+6.0% (P < .001)
12 kcal/kg (150%)103191.7 (33.7)+8.2% (P < .001)
Dose-response: P for trend < .001.
Baseline: peak VO2 1.30 (0.25) L/min.
Subgroups: no treatment × subgroup interaction for age, BMI, weight, baseline VO2, race or ethnicity, or baseline hormone therapy.
Blood pressure: no significant change in systolic or diastolic pressure in any exercise group against control.
Individual response: the SDs of change in the exercise and control arms are not in the abstract, so the share of women who did not improve cannot be told from noise.
Our arithmetic: +4.2% of 1.30 L/min is about 0.05 L/min, +8.2% about 0.11 L/min; per weekly minute the gain was about 0.058% at the lowest dose and 0.043% at the highest.

Mechanisms

Measured: peak VO2 and blood pressure only.
Authors' interpretation: previously sedentary, overweight or obese postmenopausal women had a graded dose-response in fitness across levels of exercise training.
Inference: at a fixed low intensity, weekly volume (minutes or energy) set the size of the fitness gain in untrained people; whether frequency or session length mattered at equal volume cannot be told from this design or the abstract.
Inference: in this population 50% of VO2peak sits at or a little above the 30% VO2R that REF-1327 proposed as the floor for the less fit (with a VO2peak of about 15-20 mL/kg/min, 50% of it is about 35-40% VO2R; our arithmetic, body mass not in the abstract), which fits a gain at every dose.

Practical Application

Do short easy sessions count? In a trial of 464 sedentary women (102 controls; number analysed not in the abstract), 72, 136 and 192 min a week at 50% of VO2peak raised peak VO2 4.2%, 6.0% and 8.2% over controls. Not athletes (A).
For a beginner, minutes are the dose: about 70 min a week at an easy pace already moved fitness against controls, and more minutes moved it more. This supports the minutes part of SYNTH-75's order in the untrained; DREW varied weekly energy expenditure at one intensity and did not test frequency or a higher intensity.
30 easy minutes every day (210 min a week), for an untrained person: just above DREW's top dose (191.7 min) and at a daily frequency the abstract does not report; the graded trend suggests, but the trial did not test, a further gain for a beginner (transfer from sedentary postmenopausal women; our comparison).
Not everyone will respond the same: at 50% of VO2peak a low amount left 38.5% classed as non-responders in REF-1277, but most of such spread in controlled trials is measurement error (REF-1274); judge one person over months, not one test (SYNTH-13).
For a trained rider this does not carry over: 50% of VO2peak lies far below the first threshold (VT1 at 69.8% of VO2peak in amateur cyclists, REF-1324) and near the floor below which fitter people did not gain (REF-1327). Inference.

Limitations

Abstract only. The number analysed, dropouts by arm, session frequency and mode, adherence and the SDs of change could not be checked.
Who. Sedentary, overweight or obese postmenopausal women with raised blood pressure; age is not in the abstract. Men, younger women and trained people were not studied.
Outcome. Peak absolute VO2 (L/min), adjusted for weight among other covariates; no performance, lactate-threshold or durability outcome.
One intensity. All arms trained at 50% of VO2peak, so the trial shows volume at low intensity, not low against higher intensity.
Funding and interests: NIH/NHLBI (HL66262); no device maker, federation or data platform named; conflicts not stated in the abstract. The JAMA issue carried an editorial comment (JAMA 2007;297:2137-9), not read here.
How this entry was checked and changed
Why this level

a large registered RCT (464 randomised; the rubric's A for a large pre-registered RCT of 100 or more). Read from the abstract only (closed access; no copy in Europe PMC, and the University of South Carolina repository record listed by OpenAlex is not marked open access), so the number analysed, dropouts, session frequency and the SDs of change could not be checked; the population (sedentary women) is handled by the Tier and Applicability lines, not the level