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Objectives: Estimates of adults' moderate-to-vigorous physical activity (MVPA) based on self-report are generally higher than estimates derived from criterion measures. This study examines a possible explanation for part of this discrepancy: the cutpoint bias hypothesis. This hypothesis proposes that inter- and intra-individual variability in energy expenditure, combined with the fact that adults perform a high proportion of daily activities at or just above the traditional 3 MET cutpoint, result in systematic over-estimates of MVPA., Design: Cross-sectional., Methods: Time-use recalls (n = 6862) were collected using the Multimedia Activity Recall for Children and Adults from 2210 adults (1215 female, age 16-93 years) from 16 studies conducted in Australia and New Zealand between 2008-2017. Minutes spent in MVPA were estimated using models with varying levels of intra- and inter-individual (total variability) Unadjusted (0% total variability), Low (11.9%), Best Guess (20.7%), and High (30.0%)., Results: In the Unadjusted model, participants accumulated an average of 129 (standard deviation 127) min/day of MVPA. Estimated MVPA was 98 (110), 99 (107) and 108 (107) min/day in the Low, Best Guess and High variability models, respectively, with intra-class correlation coefficients with the Unadjusted model ranging from 0.78 to 0.83., Conclusions: These findings support the hypothesis of a cutpoint bias, which probably contributes to the large disparities seen between self-reported and criterion measures of MVPA. Future studies are needed to confirm these findings using other self-report instruments and in other populations., (Copyright © 2019 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Objectives: The objective of this study was to investigate changes in use of time when undertaking a structured exercise program., Design: This study used a randomized, multi-arm, controlled trial design., Methods: A total of 129 insufficiently active adults aged 18-60 years were recruited and randomly allocated to one of three groups, a Moderate or Extensive six-week exercise group (150 and 300 additional minutes of exercise per week, respectively) or a Control group. Prescribed exercise was accumulated through both group and individual sessions. Use of time was measured at baseline and end-program using the Multimedia Activity Recall for Children and Adults, a computerized 24-h recall instrument. Daily minutes of activity in activity domains and energy expenditure zones were determined., Results: Relative to changes in the control group, daily time spent in the physical activity [F (2, 108)=20.21, p<0.001] and Active Transport [F (2, 108)=3.71, p=0.03] time use domains significantly increased in the intervention groups by 21-45 min/day. Comparatively, the intervention groups spent significantly less time watching television [F (2, 108)=5.02, p=0.008; -50-52 min/day], relative to Controls. Additionally, time spent in the moderate to vigorous energy expenditure zone had significantly increased in the intervention groups by end-program [F (2, 108)=6.35, p=0.002; 48-50 min/day], relative to Controls., Conclusions: This study is the first to comprehensively map changes in time use across an exercise program. The results suggest that exercise interventions should be mindful not only of compliance but also of "isotemporal displacement" of behaviors., (Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)