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The walking movement of children of school age and adults can be regarded as very consistent. However, few studies have reported reliability of gait parameters in very young children that may be used as normative data for the clinical assessment of gait. In the present study, nine normal children of ages 10 to 21 mo. were assessed cross-sectionally using three-dimensional video analysis and digitization to assess within-day reliability of gait kinematics. Between-subject differences in gait kinematics were also examined. In addition, one child was assessed at the onset of independent walking and at monthly intervals thereafter to assess changes in gait kinematics during the first 8 mo, of autonomous walking. The case study allowed the acquisition of pilot data for longitudinal studies of this age group. 10 kinematics variables regarded as indicators of efficient walking were measured, and reliability was assessed using one-way analysis of variance and coefficient of variation. The study showed that all children produced reliable within-day results; however, the gait of each child was unique. In the case study, the between-month differences in gait kinematics were significant. The findings may be of clinical interest for pediatricians and child neurologists given the lack of normative data for this age group.

7 children 15 to 30 mo. old participated in a study of 3-dimensional kinematics of overarm throwing. Children of different ages were considered to be at different developmental stages of motor development. Video recordings were digitised and 3-dimensional coordinates established using the DLT algorithm. Qualitative analysis indicated that the children executed either a 'static' or 'dynamic' throwing action. Either could further be classified as 'arm dominated' or 'sequentially linked.' Maximum elbow extension was no more than 163 [degrees] for any child; release velocity was higher for older subjects; and the angle of ball release was large in 'arm-dominated throws' (M = 49 [degrees]) and comparatively smaller in 'sequentially linked' throws (M = 15 [degrees]).

This study examined the three-dimensional kinematics and motor development patterns in early walking gait longitudinally over 8 mo. and presents an example of walking development of one normal child which might be used for comparative purposes in the clinical assessment of gait.

This study assessed the development of coordination during the first 8 months of independent walking and identified potential hypotheses that may be tested by further research. The walking gait of a normal child was recorded on video at the onset of independent walking, and thereafter at monthly intervals over a period of 8 months. Video images were digitized and 3-dimensional coordinates obtained. The coefficient of variation was used to measure variability in the movement. Other variables studied included range of movement, relationships between angles, angular velocities, timing relationships, proportional distance and temporal phasing. By adopting a dynamical systems perspective, this study identified variables that challenged the stability of the locomotor system. Coordinative structures were observed to shift from one state to another from age 18 months; such mutations included decreased range of motion, hip-knee angle relationship that resemble mature walking, relative time of peak angular velocity, and stability of angle-angular velocity phasing.

Introduction: Squats recruit a large proportion of the body's muscular system and provide a foundation for strength training programs for athletes. However, our understanding of electromyographical activity in variations of the high-bar back-squat, notably the split squat, is limited. Therefore, this study aims to investigate surface electromyography (EMG) in the free, Smith and split types of squat. Method: A randomised sample of 10 healthy strength-trained males (mean ± SD age, 20.3 ± 0.5 years; height, 1.7 ± 0.6 m; mass, 78.1 ± 9.5 kg; strength training, 2.5 ± 0.5 years) performed 3 repetitions of each type of squat at 75% of their one repetition maximum. A Noraxon EMG - Raxon system was used to collect peak EMG, root-mean-square EMG (RMS EMG), and integrated EMG (iEMG) data for the eccentric and concentric phases of the squat. EMG data from the free and split squats were normalised to the Smith squat. Two-way ANOVAs were used for the analysis of type-of-squat and phase-of-squat (p ≤ 0.01). Results: Statistically significant effects for type-of-squat were found for peak EMG and iEMG of the bicep femoris (BF), lateral gastrocnemius (LG) and tibialis anterior (0.001 ≤ p ≤ 0.003), and for RMS EMG of the BF (p = 0.002) and LG (p = 0.001). Significant differences in phase-of-squat were found for peak EMG and RMS EMG of BF(p = 0.001). Discussion: The split squat elicited higher BF and LG muscle activity compared to the free and Smith squats. The findings suggest that the split squat effectively stimulates the BF and LG muscles and should consequently form an integral part of strength programs for athletes. [ABSTRACT FROM AUTHOR]

Introduction: Inconclusive previous research on squat depth and the evoked electromyography (EMG) activity muddles our understanding of muscle recruitment in the back squat. This study determined EMG activity as a function of squat depth in four superficial muscles of the lower limb using relative loading. Method: Eight resistance trained males (mean ± SD age: 21 ± 1 years) performed back squats to partial, parallel and full depth using depth-relative 5-repetition-maximum loads. Muscle activity in the vastus medialis oblique (VMO), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) during the concentric and eccentric phases of the squat was determined using surface electromyography. Peak (Peak EMG), mean (Mean EMG), and integrated (iEMG) EMG normalised to their respective maximum voluntary isometric contraction (MVIC) for each muscle were evaluated. Results: Three-way Anovas and Sidak post-hoc analysis revealed significant effects for squat type (p = 0.021 - 0.001), squat phase (p = 0.001), and muscle (p = 0.001). The significant differences were between the partial and the parallel squat (p = 0.016 - 0.001); for iEMG significant effects were also found between the partial and full squat (p = 0.001). The VMO elicited the highest EMG activity (e.g., Peak EMG 93.4 ± 36.9% MVIC; parallel squat, concentric) and the BF the lowest (e.g., Peak EMG 49.9 ± 14.7%). Greater GM activity occurred in parallel squats compared to full squats (mean difference in Peak EMG = 9.1% MVIC). Conclusion: The findings suggest that squatting to the parallel position or lower induces optimal contractile stimulation of the quadriceps. Squatting to parallel depth maximises EMG activation of the GM, possibly due to a more advantageous external moment arm or a reduction in neural drive. [ABSTRACT FROM AUTHOR]