Contamination by an Active Control Condition in a Randomized Exercise Trial | JoVE Visualize

Area of Science:

Gerontology
Exercise Science
Clinical Trials

Background:

Contamination, defined as physical activity outside prescribed sessions, is often overlooked in randomized controlled trials (RCTs).
Understanding contamination is crucial for accurately assessing intervention effectiveness in exercise RCTs, particularly in older adults.
This study investigated aerobic activity outside of exercise sessions within an active control group of an older adult exercise RCT.

Purpose of the Study:

To examine the extent and predictors of contamination (out-of-class aerobic activity) in an older adult exercise RCT.
To compare out-of-class aerobic activity across different exercise intervention groups (Dance, Walking, Strength/Stretching/Stability).
To identify factors, including perceived session intensity and enjoyment, that influence contamination.

Main Methods:

A 6-month RCT involving older adults (mean age 65.06 years) assigned to Dance, Walking, or Strength/Stretching/Stability (SSS) groups.
Participants self-reported weekly out-of-class aerobic activity via home logs.
Statistical analyses examined group assignment, gender, age, BMI, session intensity, enjoyment, and adherence as predictors of out-of-class activity.

Main Results:

Out-of-class aerobic activity was lowest in the Walking group compared to Dance and SSS groups.
Significant predictors of out-of-class aerobic activity included gender, group, perceived enjoyment, and perceived intensity (all p<0.003).
Higher enjoyment correlated with more out-of-class activity, while higher intensity correlated with less. A group-by-intensity interaction indicated differences were mainly in those perceiving lower intensity.

Conclusions:

The Walking group may have perceived their sessions as sufficient exercise, leading to less compensatory activity.
The Dance and SSS groups might have viewed sessions as necessary but insufficient, potentially contributing to higher contamination.
Findings underscore the critical need for further investigation into contamination in RCTs to ensure valid results.