De-la-O A, Jurado-Fasoli L, Castillo MJ, et al. - This cross-sectional study was performed among 73 (39 women) middle-aged sedentary adults (53.7 ± 5.1 years old) in order to examine the association of sedentary time, physical activity (PA) levels, and physical fitness (i.e., maximal oxygen uptake (VO ₂ max) and muscular strength) with 1,25-dihidroxyvitamin D [1,25(OH) ₂ D] in this population. Objective evaluation of sedentary time and PA intensity levels was done using triaxial accelerometers for 7 consecutive days. A maximum treadmill test was performed to determine VO ₂ max. An isokinetic strength test and a handgrip strength test was used to evaluate lower and upper limb muscular strength, respectively. A DiaSorin Liaison immunochemiluminometric assay was used to determine 1,25(OH) ₂ D plasma concentrations. Among these middle-aged sedentary adults, findings showed no impact of physical activity habits and sedentary behaviour on vitamin D status.