LAUSR

PURPOSE Potential interactions between sedentary behaviour, physical activity (PA), and physical fitness with 25-hydroxyvitamin D (25(OH)D) status have been previously suggested. However, data are scarce concerning the association between these predictors of general health and the main active metabolite of vitamin D, the 1,25-dihidroxyvitamin D (1,25(OH)2D. This study aimed to analyse the relationship of sedentary time, PA levels, and physical fitness (i.e., maximal oxygen uptake (VO2max) and muscular strength) with 1,25(OH)2D in middle-aged sedentary adults. METHODS A total of 73 (39 women) middle-aged sedentary adults (53.7 ± 5.1 years old) participated in this cross-sectional study. Sedentary time and PA intensity levels were objectively measured with triaxial accelerometers for 7 consecutive days. VO2max was determined by a maximum treadmill test. Lower and upper limb muscular strength was assessed by an isokinetic strength test and by a handgrip strength test, respectively. 1,25(OH)2D plasma levels were measured using a DiaSorin Liaison® immunochemiluminometric assay. RESULTS No significant relationships were found between objectively measured sedentary time, PA levels or physical fitness (i.e., VO2max, extension and flexion peak torque, and hand grip strength) and 1,25(OH)2D (all P > 0.05). All results persisted after controlling for age, sex, fat mass or energy, vitamin D, calcium, and phosphorus intake. CONCLUSIONS In summary, our results show that vitamin D status is not affected by physical activity habits and sedentary behaviour in middle-aged sedentary adults.