Effects of wide step walking on swing phase hip muscle forces and spatio-temporal gait parameters.

Human walking can be viewed essentially as a continuum of anterior balance loss followed by a step that re-stabilizes balance. To secure balance an extended base of support can be assistive but healthy young adults tend to walk with relatively narrower steps compared to vulnerable populations (e.g. older adults and patients). It was, therefore, hypothesized that wide step walking may enhance dynamic balance at the cost of disturbed optimum coupling of muscle functions, leading to additional muscle work and associated reduction of gait economy. Young healthy adults may select relatively narrow steps for a more efficient gait. The current study focused on the effects of wide step walking on hip abductor and adductor muscles and spatio-temporal gait parameters. To this end, lower body kinematic data and ground reaction forces were obtained using an Optotrak motion capture system and AMTI force plates, respectively, while AnyBody software was employed for muscle force simulation. A single step of four healthy young male adults was captured during preferred walking and wide step walking. Based on preferred walking data, two parallel lines were drawn on the walkway to indicate 50% larger step width and participants targeted the lines with their heels as they walked. In addition to step width that defined walking conditions, other spatio-temporal gait parameters including step length, double support time and single support time were obtained. Average hip muscle forces during swing were modeled. Results showed that in wide step walking step length increased, Gluteus Minimus muscles were more active while Gracilis and Adductor Longus revealed considerably reduced forces. In conclusion, greater use of abductors and loss of adductor forces were found in wide step walking. Further validation is needed in future studies involving older adults and other pathological populations.

The Biomechanics and Motor Control of Tap Dancing.

Although tap dancing is a popular dance genre, little is known about the biomechanics and motor control of this complex motor skill. We conducted a detailed 3D kinematic analysis of movement timing, amplitude, and symmetry in three experienced female tap dancers. Kinematic analyzes of three basic tap dance steps (nerve beats, brush brush stamps, and heel ball walks) were undertaken. A 10-camera Vicon motion analysis system was used to collect the data. The results showed the feet and knees to play a major role in movement execution. Each step required at least 10° of ankle motion (range: 10° to 66.8°). Knee range of motion varied from 1.3° to 147.4°. For each of the dance steps the hips showed the smallest amplitude of movement, which was not greater than 21° in two out of the three dance steps. Analyzes of movement timing showed that each of the dance steps was fast, accurate, and well synchronized. The nerve beats took on average 0.50 seconds, the brush brush stamps 1.36 seconds, and the heel ball walks 4.03 seconds. A high degree of symmetry in total movement amplitude was evident at the ankles,knees, and hips for the nerve beats and heel ball walks. There was a mild degree of asymmetry at the hip for the brush brush stamp steps (symmetry index 90%). The results showed that experienced dancers had very high levels of proficiency in controlling movement amplitude, timing, and inter-limb coordination across the ankles, knees, and hips. This resulted in skilled, fast, and well executed dance steps.