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Biomechanical Differences Associated with Two Different Load Carriage Systems and their Relationship to Economy

100%

Lloyd R. , Cooke C.

Human Movement

2011

tom 12

nr 1

65-74

Purpose. To explore relationships between load carriage economy and the kinematics and kinetics of load carriage using both a backpack (BP) and a double pack (DP). Basic procedures. Nine participants walked on a treadmill at gradients of between 27% downhill and 20% uphill, and over a force plate on level ground, at a speed of 3 km.h-1. Expired air was collected throughout the treadmill experiment and all experiments were filmed for subsequent biomechanical analysis. The relative economy of load carriage was expressed in terms of the Extra Load Index (ELI). Main findings. There was a tendency for the double pack system to be associated with better economy than the BP. The double pack system provoked significantly less forward lean than the backpack and the horizontal displacement of the CoM was also smaller for the double pack system and both of these factors were strongly related to economy. There was, however, a greater range of motion of the trunk in the DP condition and this was also associated with improved economy. Conclusions. The results suggest that the DP was associated with smaller perturbations in gait than the BP and that this represents an advantage in terms of economy. In particular freedom of movement of the trunk in the sagittal plane may be an important consideration in the efficiency of load carriage systems.

Associations of Power at V̇O2peakand Anaerobic Threshold with Rank in British High Performance Junior Surfers

80%

Barlow M. J. , Gresty K. , Findlay M. , Cooke C.

Human Movement

2015

tom 16

nr 1

28-32

Purpose. The objective of this study was to determine the relationships of peak oxygen uptake ( V̇O2peak), power at V̇O2peak and power at the anaerobic threshold (AT) with national ranking in a sample of British high performance junior surfers. Methods. Eighteen male surfers (aged 15.4 ± 1.4 years) from the British Junior Surfing team were tested for V̇O2peak and AT using an adapted kayak ergometer; national ranking was used to indicate performance level. The AT was identified as the point at which V̇E/V̇O2 started to rise without a concomitant increase in V̇E/V̇CO2. Spearman’s rank (rs) and partial correlations (rp) controlling for age were used to identify the relationships between the physiological variables and national ranking. Results. Mean V̇O2peak was 3.1 ± 0.5 l · min-1 (47.7 ± 7.2 ml · kg-1 · min-1) and mean AT occurred at 48.1 ± 12.2 W. There were significant correlations between national ranking and power at V̇O2peak (rs = -0.549, p = 0.028), power at AT (rs = -0.646, p = 0.009), and age (rs = -0.579, p = 0.012). Significant partial correlations were established controlling for age between national ranking and power at V̇O2peak (rp = -0.839, p = 0.000) and power at AT (rp = -0.541, p < 0.046). Conclusions. The power outputs associated with V̇O2peak and AT were significantly related to surfer ranking in this sample. However, due to the low coefficient of determination associated with the AT/ranking relationship, AT does not discriminate well between the ranking of surfers. These findings support the inclusion of power at V̇O2peak in assessment batteries for junior competitive surfers.