# Comparing a recommendation for self-paced versus moderate intensity physical activity for midlife adults: an RCT

> **NIH NIH R01** · BROWN UNIVERSITY · 2020 · $494,428

## Abstract

The current USDHHS guidelines recommend that adults expend at least 1000 kcal per week in PA,12 which
can be obtained through 150 minutes per week of moderate intensity PA, 75 minutes of vigorous intensity PA,
or some combination. However, current estimates suggest that only 3.5% to 43.5% of US adults, and 28% of
overweight or obese adults adhere to these recommendations.13-16 Moreover, people across all World Health
Organization regions become less active as they age.17 A more progressive decline in PA is seen after age 45-
50.15,18 In essence, PA rates tend to decrease as people age and gain weight while the health benefits of PA
become more pronounced. A growing body of research19-36 suggests that a shift in national guidelines to
emphasize PA of a self-selected intensity (i.e., self-paced) instead of prescribed moderate intensity PA may
result in better adherence to PA programs, particularly among overweight and obese midlife adults.37,38 In the
proposed RCT we will conduct a field-based experimental test of the hypothesis that, among overweight and
obese midlife (ages 50-64) adults, adherence to PA programs will be improved when PA is explicitly
recommended to be self-paced rather than prescribed at moderate intensity. This approach represents an
important shift in mindset for those beginning a new program of PA: That is, PA need not be of a certain
intensity in order to “count”. If a self-paced recommendation is found to lead to better PA adherence among
overweight and obese midlife adults, this could have implications for PA recommendations for that population.
Aim 1: We will conduct an RCT comparing the effects of self-paced versus prescribed moderate intensity PA
on PA behavior among low-active overweight and obese midlife (ages 50-64) adults (N=240). Based on
procedures developed in our pilot, all participants will receive a 12-month intervention designed to help them
overcome barriers to regular PA.53 The independent variable will be random assignment to either self-paced or
prescribed moderate intensity PA. The primary outcome will be total volume of PA (frequency x duration x
intensity) as measured by accelerometry at months 3, 6, 9, and 12. H1: A recommendation for self-paced PA
will result in more PA (primary outcome) relative to prescribing moderate intensity PA based on current public
health guidelines.12,54-56 Secondary outcomes include: (a) self-reported min/week of PA over the 12-month
program, (b) fitness changes, and (c) weight changes at months 6 and 12.
Aim 2: Using EMA, we will examine putative mediators of treatment effects based on our conceptual model
(see Figure 1). H2: Self-paced PA will lead to a more positive affective response (primary mediator) and thus
greater increases in PA behavior.37 Secondary mediators (analogous to secondary outcomes) will include: (a)
perceived autonomy, and (b) perceived exertion (RPE).37 Other predictors of PA behavior will also be explored.

## Key facts

- **NIH application ID:** 10070286
- **Project number:** 1R01AG069349-01
- **Recipient organization:** BROWN UNIVERSITY
- **Principal Investigator:** David M Williams
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $494,428
- **Award type:** 1
- **Project period:** 2020-09-15 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10070286

## Citation

> US National Institutes of Health, RePORTER application 10070286, Comparing a recommendation for self-paced versus moderate intensity physical activity for midlife adults: an RCT (1R01AG069349-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10070286. Licensed CC0.

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