We have investigated whether a system of four inertial measurement units (IMUs) attached to the segments of the lower limbs could provide useful information about the kinematics of limb segment movement in gait in a healthy population. Four IMUs were attached to participants over their clothes. Participants then walked at their self-selected speed for 10 metres along a corridor and back. IMUs were removed, data downloaded on to a computer and ranges of motion were calculated for thigh, calf and knee, in addition to stride duration. 128 participants were recruited aged 18–97. There was little variation in most angle parameters up to age of 80. The relationships between angle and age are non-linear. There was a slight increase in stride duration with age of about 0.1% per year. The study concentrated on active subjects, with no specific co-morbidities that might affect gait. Results obtained may represent what is achievable for any given age, and approximate to changes that occur due to primary ageing. We propose that, after the age 80, peak muscle power declines below a threshold, such that muscular activity required to move a limb approaches the peak power available, and that it is the decline in peak muscle power that ultimately limits gait in active older people. Walking ability is important in maintaining independence as people age. It would be more effective to encourage exercises to maintain normal gait at a much earlier age. Deviations from the normal range could be identified early, and appropriate intervention given.