Sex Differences Emerge in How Moderate-to-Vigorous Activity Tracks With Fitness
In a cohort of 720 adults from the Paracelsus 10,000 study, cardiorespiratory fitness aligned with physical activity in a way that was not identical for women and men. The analysis separated moderate-to-vigorous physical activity into bouted episodes of at least 10 minutes, sporadic episodes of less than 10 minutes, and cycling time captured outside accelerometry because those minutes are often missed by sensors. That structure matters at the bedside and in prevention counseling: two people can report the same weekly activity total while arriving there through very different movement patterns, with different relationships to measured fitness.
Men in the cohort were more active overall than women, averaging 542 ± 296 minutes per week versus 350 ± 204 minutes per week. Women were slightly younger on average, carried lower body weight and smaller waist circumference, yet had higher fat mass in kilograms. More than half of the cohort met criteria for overweight, 8% of women and 10% of men had metabolic syndrome, and 24% were multimorbid. Across the sample, fitness was modest by reference standards, with the female and male participants landing at roughly the 30th percentile of the cited VO2peak reference values. In plain clinical terms, this was not a highly trained population; it was a community cohort in which routine movement still appeared to separate people with better and worse aerobic capacity.
A blunt pattern stood out immediately. Sporadic activity dominated the weekly total in every fitness group, but its share shrank as fitness rose, while bouted activity and cycling grew.
Bouted Activity and Cycling Carried More of the Fitness Signal in Men
The study used relative VO2peak from cardiopulmonary exercise testing as the outcome and modeled it against age, body mass index, smoking status, bouted MVPA, sporadic MVPA, and self-reported cycling minutes. In women, bouted MVPA was significantly associated with VO2peak, and the model fit improved when sporadic activity was added. A further gain came from including cycling, leaving all three activity patterns independently associated with fitness in the female models. The adjusted R² rose from 0.30 with bouted MVPA alone to 0.34 after adding sporadic and cycling activity.
Men showed a somewhat different profile. Bouted MVPA remained significant, and adding cycling further improved model fit, but sporadic MVPA did not contribute in the same independent way seen in women. In the male models, the adjusted R² reached 0.47 when bouted MVPA and cycling were included. BMI, age, and smoking status were also significant predictors in the regression models across sexes, which is exactly what physiology would predict: heavier body mass lowers relative VO2peak, aging reduces aerobic reserve, and smoking continues to erode cardiorespiratory performance.
This is not a trivial statistical split. Relative VO2peak reflects how much oxygen a person can use per kilogram of body weight during maximal exercise, so any activity pattern that repeatedly challenges the cardiovascular and skeletal muscle systems should influence it. Bouted episodes may provide a stronger sustained stimulus for mitochondrial and peripheral adaptations, while sporadic activity may accumulate enough intensity to matter, especially in women whose baseline physiological reserve and activity mix differ from men’s. Cycling complicates the picture further because it can represent substantial workload without always being captured by accelerometers, which means a conventional sensor-only approach can miss an important contributor to fitness.
Fitness Gradients Followed the Accumulation Pattern, Not Just the Total Minutes
Across both sexes, total MVPA increased from the low-fitness group to the high-fitness group, and the same gradient held for bouted and cycling activity. Among women, bouted MVPA rose from 47 ± 83 minutes per week in the low-fitness group to 129 ± 128 minutes per week in the high-fitness group. Among men, the corresponding increase was from 71 ± 92 minutes per week to 207 ± 157 minutes per week. Sporadic activity remained the largest component of total MVPA, but its relative contribution declined as fitness rose, from 77% in low-fitness women to 61% in high-fitness women and from 81% to 55% in men across the same fitness strata.
The cycling signal deserves separate attention. In the highest-fitness men, cycling accounted for 18 ± 20% of total MVPA, compared with 4 ± 11% in the lowest-fitness men. Women showed the same direction of effect, although less sharply, with 13 ± 19% versus 6 ± 17%. Because cycling is not reliably registered by accelerometers, its inclusion changed the interpretation of how weekly movement translated into aerobic performance. Without that diary component, a meaningful slice of exercise exposure would have disappeared from the analysis.
The clinical take-home is narrow but useful. Different movement patterns do not contribute equally to measured fitness, and the mix appears to differ by sex. In women, sporadic activity retained an independent association with VO2peak alongside bouted activity and cycling. In men, the association was driven mainly by bouted activity and cycling, with sporadic movement playing a less visible role once the other domains were entered into the model.
Because the design was cross-sectional, the direction of causality cannot be assigned. Higher fitness may encourage more structured activity, or more structured activity may improve fitness, or both processes may operate at once. What the data do show is that a single weekly MVPA number can obscure clinically relevant differences in how that activity is accumulated. Future longitudinal and intervention studies will need to determine whether sex-specific prescriptions should place different weight on bouted exercise, sporadic movement, and cycling when the goal is to improve VO2peak rather than simply count minutes.