Stepping onto a single step: a kinematic study.
BACKGROUND AND PURPOSE: To describe the timings and ranges of linear displacements of the pelvis and feet occurring in a healthy older population when stepping up onto a step, and to describe variations noted in a small sample of subjects with hemiplegia. METHOD: An observational case series study design was used and the study took place in a gait laboratory in a general hospital. A convenience sample of 54 healthy volunteers (mean age 57.6 years, range 40-90 years; 26 males, 28 females) and six subjects with chronic hemiplegia (mean age 61.7 years, range 47-70 years; five males, one female) was recruited. Participants stepped up onto an 18 cm step. The following outcome measures were made: kinematic measures of stepping up cycle time; pelvic lateral displacement; width of foot base; and height of heel clearance by use of CODA (a three-dimensional movement analysis system). RESULTS: The mean (standard deviation, SD) stepping up cycle of healthy subjects was 1.68 seconds (+/- 0.22 seconds). The total range of pelvic lateral displacement during one stepping up cycle was 70 mm. Pelvic lateral displacement was asymmetrical, being significantly greater towards the initial weightbearing leg (p<0.0001). Older subjects (aged 60+ years) had less heel clearance (p<0.03) than younger subjects (aged <60 years). Stepping up performance by subjects with hemiplegia showed wide inter-subject variability, and was observed to be as much as three times slower to use as much as four times the range of pelvic lateral displacement and twice the foot base, and to be asymmetrical in timing of the stepping up cycle. CONCLUSIONS: This kinematic study describes a healthy stepping up pattern not previously reported. Age and hemiplegia influenced the amount and speed of movement adopted during the task. Information about the movement strategies used by the elderly and those with hemiplegia should guide physiotherapists in their management of physical function.