Motion sensors have become popular for recording of physical activity (PA). Pedometers record number of steps and accelerometers may in addition estimate energy expenditures. PA guidelines recommend 150 min of moderate activity weekly for adults to maintain health. However, studies using accelerometers show that less than 5 % of the general population achieved that level. Technical developments have drastically changed the nature of human PA. Population studies demonstrate that cardiometabolic risk factors decrease when the daily step numbers exceed 9000–10000 or moderate PA 30–45 min. We have used in two intervention studies an accelerometer that records the number of steps (impacts) and accelerations (g) and observed in healthy females (N=80) beneficial effects on bone mass at daily impacts of 50–100 at 4.1 g or more (corresponds to a jump from height of 10 cm), on maximal oxygen uptake, calf muscle and cholesterol levels at daily impacts of 1000–2000 at 2.1 g or more (walking 5 km/h). In obese sedentary prediabetic subjects (N=77) we found that even very light PA (0.3–0.7 g) associated to the improvement of insulin sensitivity. Objective measurement of PA is a reliable method in studies examining the physiological effects of exercise producing also useful information to implement PA recommendations for individuals at various fitness levels. Supported by the Finnish Diabetes Association and EVO funding.