RELATIONSHIP BETWEEN THE BCH ANGLES AND RELATIVE BARBELL MASS FOR THE YOUNG WEIGHTLIFTERS DURING SNATCH

RELATIONSHIP BETWEEN THE BCH ANGLES AND RELATIVE BARBELL MASS FOR THE YOUNG WEIGHTLIFTERS DURING SNATCH

Hung Ta Chiu

Institute of Physical Education, Health and Leisure Studies, National Cheng Kung University, Taiwan email: htchiu@mail.ncku.edu.tw

INTRODUCTION

From the previous studies, investigating the relative movement between the bar and the body of the lifter seemed to be more adequate to evaluate the technique of the snatch than analyzing the barbell trajectory or the kinematics of the body movement alone. The BCH angle, a new single parameter which represents the relative movement of the lifter’s body and the barbell, has been validated to compare the snatch technique of the young female lifters. This study involved filming the snatch movement of ten young weightlifters and attempted to use the BCH angle to compare their snatch techniques.

METHODS

1. Subjects

Subjects Age (yrs)

Height (m)

Weight (kg)

Successful lifts

Males (n=5)

16.6 (1.1)

1.66 (0.06)

73.4 (11.3)

29 Females

(n=5)

18.4 (0.5)

1.57 (0.08)

69.8 (14.2)

52

2. Instrument and procedure

(1) A high speed camera (Mega speed MS1000, sampling rate=120 Hz) was set on the left side of the lifters to capture the snatch movement in the sagittal plane. The barbell mass lifted was determined by the coach’s instruction and the order was similar to that adopted in competitions.

(2) The six events in this study included (Figure 1):

Events Definition

LO lifting the barbell off the floor

CK clearing the barbell past the knee of the lifter

PB extension of the lifter’s hip joints to push the bar away from his/her body

MF the barbell reaching its maximum forward position MH the barbell reaching its maximum vertical height

CB the lifter catching the bar overhead

Figure 1: The six events included: LO, CK, PB, MF, MH and CB (from left to right in order).

Figure 2: The BCH angle

 The more lifters who had the lifts of greater RBM have performed smaller BCH angles at the MF and the MH

events.

As the barbell reaching the maximum forward position, performing greater BCH angle implied that the barbell has been far away from the lifter. The greater BCH angle at the MH event may showed that the lifter has squatted down under the bar too early.

These above inadequate movements perhaps increase the difficulty to catch the bar successfully.

RESULTS AND DISCUSSION

Table 1: The RBM and BCH angles at the six events

Males (n=5) Females (n=5)

RBM 1.34±0.14 1.18±0.24

BCH Angles (deg) at:

LO 37.8±3.1 41.4±3.7

CK 34.5±2.7 34.7±3.5

PB 12.3±3.5 7.3±4.8

MF 52.2±21.7 42.3±14.5

MH 148.2±13.9 140.3±20.4

CB 202.1±13.9 202.8±10.3

RBM: Relative Barbell Mass = barbell mass/ body weight

(3) The BCH angle defined as the angle between the projection vector of the 7

cervical spinous process to the barbell and the projection vector of the 7

cervical spinous process to the hip joint in the sagittal plane was calculated (Figure 2).

Figure 3: Relationship between BCH angles at the MF (left), MH (right) event and RBM for female weightlifters. The BCH angles of the female lifters at the MH (r=-0.75, p<0.0001) and the MF (r=- 0.53, p<0.0001) events were negatively correlated with the RBM.

Figure 4: Relationship between BCH angles at the MF (left), MH (right) event and RBM for male weightlifters. The BCH angles of the male lifters at the MH (r=-0.63, p=0.0002) was negatively correlated with the RBM. To exclude the data of the one of the male subjects (in the red circle), the BCH angles at the MF of the other four male lifters also had negative correlation with the RBM (r=-0.57, p=0.0033).

CONCLUSIONS

The results of this study show that the BCH angles of the

lifters at the MH and MF events had higher correlation

with the relative barbell mass. To reduce the BCH angle as

the barbell reaching the maximum forward position and

the maximum vertical height has been critical for the

lifters to snatch the heavier barbell successfully.