Assessing Infant Carriage Systems: Ground Reaction Force Implications for Gait of the Caregiver.

Objective To assess the acute alterations of anterior infant carriage systems on the ground reaction force experienced during over-ground walking. Background Previous research has identified the alterations in posture and gait associated with an increased anterior load (external or internal); however, the forces applied to the system due to the altered posture during over-ground walking have not been established. Method Thirteen mixed gender participants completed 45 over-ground walking trials at a self-selected pace under three loaded conditions (unloaded, semi-structured carrier 9.9 kg, and structured carrier 9.9 kg). Each trial consisted of a 15-m walkway, centered around a piezoelectric force platform sampling at 1,200 Hz. Differences were assessed between loaded and unloaded conditions and across carriers using paired samples t tests and repeated measures ANOVA. Results Additional load increased all ground reaction force parameters; however, the magnitude of force changes was influenced by carrier structure. The structured carrier displayed increased force magnitudes, a reduction in the time to vertical maximum heel contact, and an increased duration of the flat foot phase in walking gait. Conclusion Evidence suggests that the acute application of anterior infant carriers alters both kinetic and temporal measures of walking gait. Importantly, these changes appear to be governed not solely by the additional mass but also by the structure of the carrier. Application These findings indicate carrier structure should be considered by the wearer and may be used to inform policy in the recommendation of anterior infant carriage systems use by caregivers.

Contribution of Trunk Rotation and Abdominal Muscles to Sprint Kayak Performance.

Over the past two decades the importance of trunk contribution to sporting performance has been highlighted through the expanse of literature concerning core stability and strength. However, the role of trunk motion and the abdominal muscles are yet to be established during sprint kayak performance. The purpose of this study was to determine the associations among trunk rotation, kayak velocity, and abdominal muscle activity during on-water sprint kayaking. Eight international paddlers completed five 150 m sprint trials. During each trial peak muscle activation (peak root-mean-squared electromyogram) of the latissimus dorsi, rectus abdominus, external obliques and rectus femoris for ipsilateral (stroke side) and contralateral (opposite side) were recorded as the paddler passed through a 5-m calibrated volume, in conjunction with upper and lower trunk rotation and kayak velocity. Results indicated a significant strong negative relationship between lower trunk rotation and peak velocity (r = -0.684, p < 0.05). Furthermore, a significant strong positive relationship (p < 0.05) with mean velocity was identified for the contralateral rectus abdominus and multiple significant associations between the rectus femoris, rectus abdominus and external obliques during the paddle stroke. Findings indicate that limiting the rotation of the lower trunk will increase both the peak and the mean velocity, with the rectus abdominus, external oblique and rectus femoris combining to assist in this process. Training should therefore focus on developing the strength of these muscle groups to enhance performance.

Partial swing golf shots: scaled from full swing or independent technique?

During practice and competition, golfers are required to use submaximal effort to hit the ball a given distance, i.e., perform a partial shot. While the full golf swing has undergone extensive research, little has addressed partial shots and the biomechanical modifications golfers employ. This study investigates the biomechanical changes between full and partial swings, and determines if the partial swing is a scaled version of the full swing. Using a repeated measures design, 13 male golfers completed a minimum of 10 swings in the full and partial swing conditions, whilst club, ball, kinematic, and kinetic parameters were recorded. Large and statistically significant reductions in body motion (centre of pressure ellipse: 33.0%, p = 0.004, d = 2.26), combined with moderate reductions in lateral shift (25.5%, p = 0.004, d = 0.33) and smaller reductions in trunk rotation (arm to vertical at top of backswing: 14.1%, p = 0.002, d = 2.58) indicate golfers favour larger reductions in proximal measures, combined with diminished reductions as variables moved distally. Furthermore, the partial swing was not found to be a scaled version of the full swing implying a new approach to coaching practices might be considered.