Effects of a motivational, individual and locally anchored exercise intervention (MILE) on cardiorespiratory fitness: a community-based randomised controlled trial

Abstract

Background: Risk factors for chronic disease, including low cardiorespiratory fitness levels (VO_2max), are often present in middle-aged populations. We aimed to evaluate the efficacy of a motivational, individual, and locally anchored physical activity intervention on increasing VO_2max in 30-49 year-olds with low VO_2max.

Methods: 232 adult volunteers with low VO_2max were randomised to intervention (n = 115) or routine care (n = 117). The intervention included four motivational interviews; six months' free membership to a local sports club; and a GPS-watch/activity monitor for uploading training data to an online platform/community. Routine care was one or two motivational interviews. Inclusion criteria were low VO_2max based on the cut off levels: ≤ 39 and ≤ 35 ml O₂/kg/min. For 30-39 and 40-49 year-old men respectively and ≤ 33 and ≤ 31 ml O₂/kg/min for 30-39 and 40-49 year-old women, respectively. The primary outcome was change in VO_2max from baseline to twelve months estimated with a maximal ergometer bicycle test. Secondary outcomes included physical activity, biochemical and anthropometric measures, and health-related quality of life. The primary analyses were based on all available data and sensitivity- and predefined sex analyses were performed. The between-group differences were estimated using independent t-tests and presented with 95% confidence intervals.

Results: No significant between-group differences in primary or secondary outcomes were found at twelve months' follow-up. The mean VO_2max change from baseline in the intervention- and routine care (ml/kg/min) was 3.8 (95% CI: 2.6; 5.0) and 3.4 (95% CI: 1.7; 5.2), respectively. No changes in physical activity were observed. The mean VO_2max (ml/kg/min) changes from baseline in the intervention- and routine care group in men were: 5.0 (95% CI: 3.5; 6.4) and 3.5 (95% CI: 1.5; 5.4); and in women: 1.5 (95% CI: -0.1; 3.1) and 3.4 (95% CI: -0.1; 7.8), respectively. Significant differences in VO_2max between non-completers (44.2%) and completers were observed, 26.3 (95% CI: 25.1; 27.5) vs 28.2 ml/kg/min (95% CI: 27.1; 29.0; p = 0.02). Sensitivity analyses did not change the main result.

Conclusion: Offering a multi-component physical activity intervention to 30-49 year-olds with low levels of VO_2max had no effect on the change in VO_2max from baseline to twelve months compared with routine care.

Trial registration: ClinicalTrials.gov (no. NCT01801956 ). Registered 1 March 2013.

Keywords: Accelerometry; Community; Maximal ergometer bicycle test; Physical activity; Randomised explanatory design.

Fig. 1

Graphical depiction of the timeline and content of the intervention and routine care in ‘The MILE-study’. Squares reflect the fixed elements, e.g. membership of the sports club. Circles reflect the activities that were flexible, e.g. the motivational interviews. This graphical method was proposed by Perera et al. [25]

Fig. 2

Participant flow in the MILE-study, Randers Municipality, Denmark, 2013–2015