(1) Background: Collaboration between the health care sector and the sports sector to increase physical activity (PA) behaviour among inactive adults is still rare. The objective of the study was to evaluate the short- and long-term effectiveness of a mixed PA intervention on the PA behaviour in an adult population. (2) Methods: In a quasi-experimental study with two follow-up measurements (four and 12 months), adults were contacted by post before their stay in a health resort. During the health resort stay, the intervention group (IG) received PA counselling and a coupon for 12 standardised free-of-charge sessions in a sports club. The participants in the comparator group (CG) received PA counselling and written material. PA was measured with an accelerometer (GENEActive). Linear mixed-effects models were applied to examine the change in PA behaviour, both within and between groups in moderate- to vigorous-intensity PA over time. (3) Results: We obtained at least one follow-up measurement from 217 participants (IG = 167, CG = 50), who were 50% female, with an average age of 53 (±6) years. PA significantly increased from the baseline to the four-month measurement by 58 min./wk (95% CI 36, 80) and to the 12-month measurement by 24 min./wk (95% CI 2, 46) within the IG. No change in PA occurred in the CG. We also found a short-term between-group (IG vs. CG) difference in change over time, but not a long-term difference. (4) Conclusions: The study confirms that a collaboration between the health care sector and local sports clubs is a feasible method of recruiting people into a standardised PA programme and to increase their PA over the long term.
Keywords: counselling; health care sector; inter-sectoral collaboration; physical activity; standardised sports club programme.