The purpose of this study was to investigate the determinant factor on Uchi-Mata, a judo technique used most frequently across all weight divisions. 12 expert(20.83±1.03 years, 175.33±6.75 cm, 76.00±9.67 kg) and 12 novice(22.75±2.38 years, 176.50±6.63 cm, 78.43±2.38 kg) male subjects were participated in this experiment.
I conducted an independent t-test to compare and analyze the kinematic and kinetic variables of Uchi-Mata between groups. In order to identify skill factors influential on athletic performance, I selected 34 major factors out of 642 variables based on an analysis of effect size and confidence interval. Cohen''s d was 0.8 or larger, and the confidence interval was 95%. For an objective quantification of the extent of influence by each body segment while applying the technique, I calculated the kinetic contribution by each body segment.
The results were as follows:

1. Skill factor

1) Differences in kinematic factors for expert and novice players
The differences in kinematic factors for expert and novice players by body segment are as follows:

The average total time consumed in applying uchi mata was 1.173 seconds for expert players, and 1.256 seconds for novice players. Accordingly, expert players were faster than novice players by 0.083 seconds, however, this was not statistically significant.

Significant differences were observed for a displacement of the center of mass of X－E3(p=.039), E4(p=.001), Y－E2(p=.004) Z－E2(p=.024), E4(p=.040), a velocity of X－E2(p=.016), E3(p=.000), Z－E3(p=.001), a left hand displacement of X－E3(p=.009), E4(p=.002), Y－E2(p=.016), E3(p=.007), Z－E3(p=.001), a right hand displacement of X－E3(p=.005), E4(p=.000) Z－E4(p=.000), a left finger linear velocity of X－E3(p=.000), Y－E3(p=.025), Z－E3(p=.002), and a right finger linear velocity of X－E2(p=.008), E4(p=.047), Y－E3(p=.002), E4(p=.000), Z－E3(p=.020).
There were significant differences for a left hip angle of Y－E1(p=.044), E2(p=.002), Z－E2(p=.004), a right hip angle of X－E1(p=.015), a left hip angle with an angular velocity of X－E3(p=.028), a right hip angle with an angular velocity of Y－E3(p=.041), Z－E2(p=.001), a left ankle joint angle of X－E1(p=.045), E2(p=.042), and a left ankle joint angular velocity of E3(p=.043).
Significant differences were found for a right shoulder joint angle of X－E4(p=.017) Y－E1(p=.035), a left shoulder joint with an angular velocity of Y－E2(p=.028), a right elbow joint angle of E4(p=.015), a right elbow joint with an angular velocity of E1(p=.002), E3(p=.002), a trunk angle of X－E3(p=.029), Y－E1(p=.036), and an angular velocity of X－E1(p=.022), E3(p=.000), E4(p=.019), Y－E2(p=.022), Z－E1(p=.042), E3(p=.001), E4(p=.018).

2) Kinetic differences of expert and novice players
The differences in kinetic factors for expert and novice players by body segment are as follows:
Significant differences were observed when the left hip joint moment was Y－E2(p=.038), when the work done by the left hip joint was E2(p=.045), E3(p=.005), E4(p=.004), when the work done by the left knee joint was E3(0.040), when the work done by the left ankle joint was E2(p=.024), E3(p=.007), E4(p=.016), and when the work done by the right ankle joint was E4(p=.027).
The differences were statistically significant when the moment of the left shoulder joint was X－E3(p=.001), E4(p=.008), Y－E1(p=.002), E2(p=.038), E3(p=.036), E4(p=.006), Z－E1(p=.019), E3(p=.007), when the moment of the right shoulder joint was X－E2(p=.015), E3(p=.000) Y－E4(p=.032), when the work done by the right shoulder joint was E3(p=.040), E4(p=.000), when the power of the right shoulder joint was E2(p=.006), when the moment of the left elbow joint was E3(p=.004), E4(p=.016), when the work done by the right elbow joint was E4(p=.027), when the power of the left elbow joint was E2(p=.043), when the power of the right elbow joint was E1(p=.043), when the power of the left wrist joint was E2(p=.029), when the power of the right wrist joint was E2(p=.048), E4(p=.030), when the work done by the trunk was E1(p=.015), and when the power of the trunk was E1(p=.015), E2(p=.001).

2. Major skill factors

Among the 642 variables, I selected 34 major factors that are influential on athletic performance when applying uchi mata.
1) E1 - Lt Shoulder moment Y, Lt Shoulder moment Z, Rt Elbow power, Trunk work, Trunk power
2) E2 - Lt Shoulder moment Y, Rt Shoulder moment X, Rt Shoulder power, Lt Elbow power, Lt Wrist power, Rt Wrist power, Trunk power, Lt Hip moment Y, Lt Hip work, Lt Ankle work
3) E3 - Rt Shoulder moment X, Lt Shoulder moment X, Lt Shoulder moment Z, Lt Shoulder moment Y, Rt Shoulder work, Lt Elbow moment X, Lt Hip work, Lt Knee work, Lt Ankle work
4) E4 - Lt Shoulder moment X, Lt Shoulder moment Y, Rt Shoulder moment Y, Rt Shoulder work, Lt Elbow moment X, Rt Elbow work, Rt Wrist power, Lt Hip work, Rt Ankle work, Lt Ankle work

3. Kinetic contribution of each segment

1) An analysis of the kinetic contribution of each segment showed that for both expert and novice players, the results can be arranged in descending order as follows: Rt hip (Expert: 23.294, Novice: 27.771%) > trunk (Expert: 18.650, Novice: 20.386%) > Rt knee (Expert: 14.546, Novice: 14.984%) > Lt hip (Expert: 13.121, Novice: 12.528%) > Lt knee (Expert: 11.417, Novice: 8.814%) > Rt shoulder (Expert: 7.231, Novice: 5.055%) > Lt shoulder (Expert: 3.758, Novice: 3.389%) > Lt ankle (Expert: 2.794, Novice: 2.397%) > Rt ankle (Expert: 1.635, Novice: 1.898%) > Lt elbow (Expert: 1.571, Novice: 1.227%) > Rt elbow (Expert: 1.101, Novice: 0.946%) > Lt wrist (Expert: 0.649, Novice: 0.370%) > Rt wrist (Expert: 0.234, Novice: 0.235%). In terms of contribution, the top 6 segments accounted for 88.3% for expert players, and 89.5% for novice players.
2) The amount of work done in the case of expert players can be arranged in descending order as: Rt hip (24.473%) > trunk (19.133%) > Rt knee (13.509%) > Rt shoulder (13.405%) > Lt hip (11.055%) > Lt knee (9.731%) > Lt shoulder (2.835%) > Lt ankle (1.967%) > Rt ankle (1.488%) > Lt elbow (1.041%) > Rt elbow (0.992%) > Lt wrist (0.192%) > Rt wrist (0.181%). The contribution of the top 6 segments amounted to 91.3%.
For novice players, the order was: Rt hip (30.249%) > trunk (17.073%) > Rt knee (16.705%) > Lt hip (10.066%) > Rt shoulder (8.803%) > Lt knee (7.152%) > Lt shoulder (3.981%) > Lt ankle (1.530%) > Rt ankle (1.335%) > Lt elbow (2.024%) > Rt elbow (0.730%) > Lt wrist (0.164%) > Rt wrist (0.189%). The contribution of the top 6 segments came to a sum of 90.0%.
The above results on the 34 key factors which are influential on uchi mata and the kinetic contribution of each body segment can serve as useful reference tools in developing training programs and evaluating judo skills.