A comparison of two short-term intensive physical activity interventions: methodological considerations

Abstract

Background: Increases in chronic illness due to sedentary lifestyles and poor metabolic fitness have led to numerous intervention strategies to promote physical activity (PA). This paper describes the methodological strategies of two short-term PA interventions. Outcome measures reported are PA adherence and compliance rates during the intervention and at 3, 6 and 12-month follow-up.

Methods: The 40-day interventions were: a pedometer-based walking program (n = 251) and a group-based intensive program (n = 148). There was also an active control group (n = 135). Intervention subjects were prescribed PA each day and required to record all activity sessions (pedometer steps or energy expenditure from heart rate monitors).

Results: Compliance (≥ 150 min/wk PA) was highest post-intervention (81.1% and 64.5% for the group and pedometer subjects, respectively) and then progressively decreased across the 12-month follow-up period (final compliance rates were 53.5% and 46.6%, respectively) although they remained significantly higher than pre-intervention rates (zero %). There was significantly higher adherence to 6 months (75.0% and 64.9%), and compliance to 3 months (64.9% and 51.0%), for group versus pedometer subjects. The active control group maintained the highest adherence and compliance rates across the study.

Conclusions: The group-based program resulted in higher adherence and compliance rates post-intervention although both types of interventions showed long-term effectiveness to increase activity patterns.

Figure 1

Flow chart of subject recruitment and selection.

Figure 2

40-DAY PA itinerary for the group intervention arm showing the 40 consecutive days of activity.

Figure 3

Compliance rate for the pedometer subjects (% achieving the average daily step count across each week of the intervention) and group subjects on both group exercise days and on the subjects' individual exercise days (% achieving ≥ 30 min recorded activity per day across each week of the intervention).

Figure 4

The percentage of subjects remaining in the study (adherence) and achieving ≥ 150 min PA/wk (compliance) at the various test times. Shaded area indicates the 40-DAY PA intervention phase. 1 indicates a higher rate between the active controls and intervention subjects. 2 indicates a higher rate for the group subjects versus the pedometer subjects using Chi square analysis (p < 0.05). Compliance was calculated using ITT analysis.

Figure 5

The mean (± SE) intensity of the PA sessions by the group subjects. Individual training days and group-led training days are shown separately.

Figure 6

The mean (± SE) kJ recorded during each PA session and averaged for each week of the intervention. Individual training days and group-led training days are shown separately.