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The study purposes were to record the lower extremity sagittal and frontal joint moments and powers during gait initiation (GI); evaluate GI support moments in both planes; and analyze planar energy patterns in a group of 15 healthy, young adults. 3D motion and ground reaction force data were used to calculate support moments (SM) and joint moments and powers as well as center of mass (COM) kinematics. STEP1 had no visible SM. It appeared in STEP2 and, by STEP3, resembled that seen in steady-state gait. Joint moments demonstrated a similar development towards typical patterns over the three steps. Correlations of moment data between planes indicate that the frontal plane component of the SM acts to keep the COM centered. It is suggested that Winter’s 1980 SM definition be extended to include both a support (sagittal) component and a centering (frontal) component. Energy was calculated for individual bursts of joint powers in both planes and each step had characteristic patterns in each plane, with patterns resembling steady-state gait appearing in the third step. Test-retest reliability (ICC range: 0.796 – 0.945) was high with CV values in the sagittal plane (36.6 – 37.5%) being less variable than in the frontal plane (39.0 – 82.0%). COM kinematics revealed that acceleration peaked in STEP2 (ICC range: 0.950 – 0.980, CV < 20.0%). Data supported hypotheses regarding the dominance of the frontal plane power in STEP1, with substantial power coming from hip flexors. As well, powers in the sagittal plane were generally of larger magnitude than in the frontal plane.

Gender Differences in Postural Stability Among Children This study aimed to examine the gender differences in postural stability among 8-12 year-old children. Twenty-six children participated in this repeated measures study to measure the centre of pressure (COP) under one normal condition (CONTROL: hard surface, eyes open, and looking straight ahead) and two challenging sensory conditions (ECHB: eyes closed and head back; and EOCS: eyes open and compliant surface) in randomized order. Girls had significantly lower COP path velocity (COP-PV, p < 0.05, medium effect), smaller radial displacement (COP-RD, p < 0.05, medium effect), and lower area velocity (COP-AV, p < 0.05, medium effect) as compared to boys when the three conditions were pooled. Gender differences were found in the percentage changes in COP-RD during ECHB (p < 0.05, large effect) and EOCS (p < 0.05, medium effect), and in COP-AV during both ECHB and EOCS conditions (p < 0.05, medium effect). Postural stability performance of girls had higher correlations with age (-0.62 vs. -0.40), body mass (-0.60 vs. -0.42), foot length (-0.68 vs. -0.45), and physical activity level (-0.45 vs. 0.02), as compared to boys. Girls had better postural stability than boys but were more affected by altered sensory input information. Girls are more capable of integrating their sensory inputs, whereas boys treat each sensory input somewhat separately and rely more on somatosensory feedback. Exercises such as standing on unstable surfaces with eyes open instead of eye closed and head back are more beneficial to children's postural stability control system.

H:Q Ratios and Bilateral Leg Strength in College Field and Court Sports Players One of the key components in sports injury prevention is the identification of imbalances in leg muscle strength. However, different leg muscle characteristics may occur in large playing area (field) sports and small playing area (court) sports, which should be considered in regular injury prevention assessment. This study examined the isokinetic hamstrings-to-quadriceps (H:Q) ratio and bilateral leg strength balance in 40 male college (age: 23.4 ± 2.5 yrs) team sport players (field sport = 23, soccer players; court sport = 17, volleyball and basketball players). Five repetitions of maximal knee concentric flexion and concentric extension were performed on an isokinetic dynamometer at two speeds (slow: 60 °·s-1 and fast: 300°·s-1) with 3 minutes rest between tests. Both legs were measured in counterbalanced order with the dominant leg being determined as the leg used to kick a ball. The highest concentric peak torque values (Nm) of the hamstrings and quadriceps of each leg were analyzed after body mass normalization (Nm·kg-1). Court sport players showed significantly weaker dominant leg hamstrings muscles at both contraction speeds (P < 0.05). The H:Q ratio was significantly larger in field players in their dominant leg at 60°·s-1 (P < 0.001), and their non-dominant leg at 300°·s-1 (P < 0.001) respectively. Sport-specific leg muscle strength was evident in college players from field and court sports. These results suggest the need for different muscle strength training and rehabilitation protocols for college players according to the musculature requirements in their respective sports.