The Effects of Anthropometrics on the Start Position of the Snatch: Implications for Bar Path Kinematics.

Abstract

Abstract
INTRODUCTION: Optimising an individual lifter’s hip height at the start position (SP) of the Snatch lift (SN) has been identified as a key factor in determining a successful lift. Whilst it has been indicated that individual anthropometrics affect Olympic lifting mechanics and technique, anthropometrics has also been shown to affect the direction of the bar from the SP to the end of the FP. Considering that it has become widely accepted that a lifters SP is influenced by their height, body mass, somatotype and body proportions, the aim of this research is to provide insight into the relationship between anthropometric characteristics and adopted SP and how this affects kinetic and kinematic variables at the SP. METHODS: 20 experienced male weightlifters performed three single lifts at 85% of their most recent one repetition maximum (1RM). Kinetic and kinematic data of the barbell and lifter were collected during each trial using Qualisys Track Manager before being exported into visual 3D where the outcome measures and anthropometric data were derived. The Outcome measures were Ground Reaction Force Vector Angle (GRF°) at the SP, Absolute Hip Height at the SP relative to the floor and Maximum Horizontal Barbell Displacement (MHBD) from the SP to the FP. The anthropometric characteristics analysed were: absolute body segment lengths, absolute limb length ratios and body segment lengths normalised to standing height. A stepwise regression analysis was then performed to see whether anthropometric variables predicted each outcome measure. RESULTS: Absolute Femur length (r2=0.34, p<0.01) and shank to femur ratio (r2=0.20, p=0.05) were found to be significant predictors of absolute hip height at the SP of the SN. Relative femur length (r2=0.45, p<0.01), relative trunk length (r2=0.69, p<0.01) and shank to femur ratio (r2=0.77, p<0.05) were found to be significant predictors of the GRF° at the SP of the SN. No anthropometric variables were found to be significant predictors of MHBD. CONCLUSION: Based on these results it can be concluded that a lifters femur length, shank to femur ratio and relative trunk length are the most important anthropometric parameters to consider when optimising an individual’s SP for the SN lift. Furthermore, in order for force to be transferred effectively through the kinetic chain, body segments must be arranged so that muscle length-tension relationships are optimised and joint torque can be maximised. Therefore, a combined approach that considerers the isolated body segment lengths, in conjunction with how they interact to affect the entire barbell-lifter system is desirable. The coach should spend time familiarising themselves with how different anthropometric segment lengths and ratios creates a correct SP, to enable them in setting the optimal SP for each lifter.