A major new study has revealed, in unprecedented detail, exactly how childhood cancer survivors accumulate physical activity across the days of the week — and the findings are already being described as a turning point in survivorship care. By applying sophisticated statistical modeling to minute-by-minute accelerometer data from hundreds of survivors in Norway, Switzerland, Finland, Denmark, and Germany, an international research team has identified distinct weekly activity “trajectories” that differ strikingly between adolescent and adult survivors, and between survivors and healthy peers. The work, published in the Journal of Cancer Survivorship, suggests that many survivors quietly struggle through a pattern invisible to conventional research: a dramatic collapse in activity on weekends.
Childhood cancer survival rates have risen dramatically over the past decades, with the majority of young patients now living well into adulthood. That success has exposed a new challenge: late effects of treatment, including cardiovascular complications, reduced bone mineral density, chronic fatigue, musculoskeletal problems, and psychological distress. Physical activity is widely regarded as one of the most powerful, modifiable tools to prevent, delay, or mitigate these late effects. Guidelines recommend that children and adolescents accumulate at least 60 minutes of moderate-to-vigorous physical activity (MVPA) per day, while adults should aim for 150 to 300 minutes of moderate activity per week. Yet most prior research has relied on weekly or daily averages — a blunt instrument that tells us nothing about how activity is actually distributed across the week, or on which days survivors might need the most support.
The new study, led by first author Mari Bratteteig of the Oslo Centre for Biostatistics and Epidemiology at Oslo University Hospital and the Norwegian School of Sport Sciences, set out to change that. Drawing on data from two large research programs — the Physical Activity in Childhood Cancer Survivors (PACCS) study, which included adolescents aged 9 to 18, and the Swiss SURfit randomized controlled trial, which included adult survivors aged 18 to 49 — the researchers analyzed hip-worn ActiGraph GT3X+ accelerometry from 434 adolescent and 156 adult survivors. Participants wore the devices for one to two weeks, capturing the vertical-axis acceleration used to classify time spent in MVPA and light physical activity (LPA). Controls came from the PACCS comparison group and the Norwegian National Physical Activity Survey 2, with the adult controls matched exactly to survivors on sex and age.
The methodological heart of the study lies in its use of multivariate latent class mixed models, a statistical framework capable of grouping individuals based on the shape of their repeated daily measurements over time. Rather than asking whether survivors move more or less on average than healthy peers, the model asks whether distinct patterns of day-to-day movement exist within the population — and whether individuals can be reliably assigned to one of those patterns. The team ran models with one through six classes, testing 50 different sets of initial parameter values to avoid convergence toward local maxima, and selected the optimal model using the Akaike information criterion, the Bayesian information criterion, entropy as a measure of class discrimination, and the minimum class size needed for stability. Both MVPA and LPA were entered simultaneously into the models, meaning the classes were defined by the interplay of two intensities rather than one — a methodological first in this population.
The results were revealing. Among adolescent survivors, four distinct weekly trajectories emerged. Twenty percent of the group fell into a “Low regular” pattern, averaging only about 30 minutes of MVPA and 140 minutes of LPA per day — never approaching the guideline of 60 minutes of MVPA on any day of the week. A further 32 percent followed a “Medium, drop weekend” trajectory, sustaining roughly 60 minutes of MVPA on weekdays before falling to around 30 minutes on Saturday and Sunday. Eight percent showed a curious “Medium, peak Friday” pattern, with activity climbing steadily from Monday to Friday and then collapsing over the weekend. The largest group — 41 percent — followed a stable “Medium regular” trajectory of about 60 minutes of MVPA and 200 minutes of LPA every day, closely in line with guidelines.
Adult survivors showed a different landscape. Forty percent followed a “Medium regular” trajectory at about 40 minutes of MVPA and 250 minutes of LPA daily. Thirty-one percent again showed the weekend drop, falling from roughly 50 minutes of MVPA on weekdays to about 20 minutes on weekends. Twenty-three percent maintained steady MVPA but accumulated a striking 350 minutes of LPA per day — a pattern the authors suggest may reflect manual labor, with its emphasis on walking and lifting, among those with lower educational attainment. Only 6 percent — nine individuals — achieved a “High, drop weekend” trajectory, exceeding 60 minutes of MVPA and 400 minutes of LPA on most weekdays. Notably, no “Low regular” MVPA trajectory was identified among adult survivors at all.
When the researchers compared survivors with healthy controls, the picture grew even more interesting. Among adolescents, the four trajectory shapes were broadly similar between survivors and controls, but survivors showed fewer fluctuations and narrower confidence intervals — a pattern the authors interpret cautiously, possibly as “energy economization” or more planned, structured behavior shaped by the demands of living with late effects. More striking was the allocation: only 20 percent of adolescent survivors, versus 31 percent of controls, occupied the Low regular class, and survivors were overrepresented in the two medium-activity classes. Among adults, three of four trajectories were comparable between groups, and survivors again showed a more favorable distribution, with no equivalent of the low-activity class found in 17 percent of controls.
Who ended up in which trajectory? Across both age groups, the dominant factors were sex, age, sleep duration, and educational level. The most vulnerable group — adolescent survivors in the Low regular class — was disproportionately female, older, slept fewer than eight hours on weeknights, and had survived central nervous system (CNS) tumors, a finding consistent with the motor and sensory impairments that can follow brain tumor treatment. Importantly, the authors note that physical activity has been shown to support neural recovery and enhance motor proficiency and cognitive function specifically among CNS tumor survivors, making this subgroup a clear priority for targeted intervention. Sleep, a modifiable behavior, emerged as a particularly intriguing thread: adolescent and adult survivors with low weekday sleep were concentrated in the least and most extreme classes, and the authors suggest that improving sleep hygiene may be an underexplored lever for increasing activity.
The weekend drop may prove to be the study’s most actionable finding. More than one-third of both adolescent and adult survivors showed a marked collapse in activity from weekdays to weekends — the precise opposite of the “weekend warrior” pattern debated in the general population, where people accumulate little weekday activity but catch up on weekends. The authors propose several plausible mechanisms: depleted energy after an intense week, the absence of active commuting to school or work, and the lack of organized sports or structured leisure on weekends. Because the drop is so common and so spatially and temporally predictable, interventions designed specifically to shore up weekend activity — community programs, family-based activities, telecoached weekend plans — could deliver disproportionate gains in total weekly activity volume.
The study is not without limitations, which the authors confront directly. Accelerometers under-register activities with little vertical movement, such as cycling, strength training, and swimming. One to two weeks of monitoring may not capture habitual behavior, although prior evidence suggests physical activity is reasonably stable over time. Sedentary time was not included in the models despite its known independent effects on health. The adult survivor sample came from the baseline of a randomized controlled trial testing an exercise intervention, raising the possibility of selection bias — survivors who volunteer for an activity-focused trial are likely unusually motivated — so the favorable adult survivor comparisons should be read with caution. Low inclusion rates in both the SURfit trial (19 percent) and the Norwegian survey (26 percent), and small numbers in certain diagnostic strata, meant that all reported group differences remain descriptive rather than formally adjusted.
Nevertheless, the implications for clinical practice are substantial. The findings demonstrate that the population of childhood cancer survivors is not uniformly inactive — most adolescent and adult survivors in this study followed patterns consistent with or close to public health guidelines — but also that a substantial and identifiable subgroup faces persistent, daily barriers to movement. Knowing that female adolescent survivors of CNS tumors who sleep poorly are concentrated in the least active class gives clinicians a concrete profile to screen for during follow-up care. Knowing that weekends are the weak link for a third of survivors gives intervention designers a specific target. The authors call for future research to determine which of these weekly trajectories are most beneficial — or most harmful — for long-term physical and mental health, and to investigate whether structuring activity differently across the week can translate into measurable reductions in late effects. In a population that continues to grow as survival rates climb, that knowledge could turn physical activity from a generic recommendation into a genuinely personalized tool of survivorship medicine.
Subject of Research: People
Subject of Research: Cancer
Article Title: Weekly Physical Activity Trajectories in Short- and Long-Term Survivors of Childhood Cancer: the PACCS and SURfit Studies
Article References: Bratteteig, M., Grydeland, M., Anderssen, S. A., Ruud, E., Torsvik, I. K., Thorsen, L., Fridh, M. K., Järvelä, L., Götte, M., Hansen, B. H., Zürcher, S. J., Kriemler, S., Perrier, F., & Rueegg, C. S. (2026). Weekly physical activity trajectories in short- and long-term survivors of childhood cancer: the PACCS and SURfit studies. Journal of Cancer Survivorship. https://doi.org/10.1007/s11764-026-02086-2
Image Credits: AI Generated
DOI: 10.1007/s11764-026-02086-2
Keywords: Childhood cancer survivors, physical activity trajectories, accelerometer, MVPA, light physical activity, PACCS, SURfit, late effects, weekend activity drop, survivorship care
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Nathaniel Bowman. (September 7, 2026). Tracking weekly physical activity in short- and long-term childhood cancer survivors. Scienmag. https://scienmag.com/tracking-weekly-physical-activity-in-short-and-long-term-childhood-cancer-survivors/
Nathaniel Bowman. “Tracking weekly physical activity in short- and long-term childhood cancer survivors.” Scienmag, 7 September 2026, https://scienmag.com/tracking-weekly-physical-activity-in-short-and-long-term-childhood-cancer-survivors/. Accessed 7 September 2026.
Nathaniel Bowman. “Tracking weekly physical activity in short- and long-term childhood cancer survivors.” Scienmag. September 7, 2026. https://scienmag.com/tracking-weekly-physical-activity-in-short-and-long-term-childhood-cancer-survivors/
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