Comparison of Good and Poor Jumper's Plantar Load Distributions During Vertical Jump Take-off Phase

Abstract

PURPOSE: Vertical jump is one of the most important tests in order to evaluate whole body power out-puts in athlete. Heights of vertical jump depend on vertical impulse in ground reaction force (GRF) during take-off phase. A plantar foot function might be important to get an effective GRF during vertical jumps. The purposes of the present study were to compare the Good and Poor Jumper's plantar load distributions and to obtain a plantar load pattern as to get an effective GRF in vertical jump. METHODS: In order to define sub-areas from foot anatomical measurement points, Pressure Plate Foot Scan(Rs Scan international, 0.5m plate, with 4096 resistive sensors,200Hz), VICON motion capture system(Oxford Metrics Ltd.,100Hz) and Force plate(Kistler,1Khz) were systematically synchronized as to acquire the data. Right and left foot plantar area were respectively divided into 5 sub-area (MF: medial forefoot, LF: lateral forefoot, MiF: midfoot, MH: medial heel, LH: lateral heel). Thirty two male subjects performed counter movement vertical jump on pressure plate and force plate. Subjects were divided into Good (n=8) and Poor (n=9) groups (Good: Age 21.4±2.4 yrs, BH: 173.9±4.6 cm, BW: 71.8±5.3 kg, Poor: Age 24.0±3.8 yrs, BH: 170.5±5.3 cm, BW: 69.7±7.4 kg)according to performance(jump heights). Total plantar load impulse, 5 sub-area plantar load impulses and weighting normalize time were calculated and compared between good and poor jumpers. RESULTS: In both groups vertical jump plantar load distribution change from Heel to LF and MF. Good jumper however, exhibited larger total plantar load impulse and MF plantar load impulse compared to poor jumpers (Total impulse: 0.71±0.05 VS. 0.61±0.06N·sec/BW,p<0.01, MF impulse: 0.39±0.04 VS. 0.28±0.07 N·sec/BW,p<0.01). As for the shift of weighting from LF to MF, good jumpers were faster in comparison with poor jumper (43.8±9.2 VS. 59.9±15.8%, p<0.05). CONCLUSIONS: MF impulse might largely affect the vertical jump performance, which might be accompanied by the fast plantar load shift from LF to MF. The results of this study suggest plantar load distribution change could be one of key factors to assess the skilled jump performance.