Kinetic analysis of individual upper limbs during baseball tee-batting motion at different hitting-point heights

Abstract

Kinetic analysis of individual upper limbs during baseball tee-batting motion at diŠerent hitting-point heights. Japan J. Phys. Educ. Hlth. Sport Sci. 59: 431 452, December, 2014 AbstractThe purpose of this study was to clarify the kinetic features of the upper limbs at diŠerent hitting-point heights (high, middle, and low) during baseball tee-batting. Twenty-three collegiate male baseball players (age: 19.8±1.3 yr, height: 1.74±0.04 m, weight: 74.1±6.2 kg, athletic career: 12.0± 2.1 yr) participated. Three-dimensional coordinate data were captured using a VICON MX system (12-camera, 250 Hz), and kinetic data for each hand were collected using an instrumented bat equipped with 28 strain gauges (1000 Hz). Three tee-batting heights were set for each subject based on the upper and lower limits of the strike zone according to the rules of baseball. Kinetic variables for the upper limbs, such as joint torque, joint torque power, and mechanical work, were calculated. The period of forward swing motion was divided into down-swing and level-swing phases. The results are summarized as follows: 1) The extension torque and positive torque power at each individual shoulder joint were signiˆcantly greater at the low hitting-point height than at other heights. 2) The positive torque power for extension torque at each individual elbow joint in the last half of the down-swing phase was signiˆcantly greater at the low hitting-point height than at other heights. 3) Negative power for adduction/abduction torque at each individual shoulder joint in the level-swing phase was observed at the low hitting-point height. 4) The mechanical work done by joint torque about the ‰exion/extension and adduction/abduction axes at the shoulder, the ‰exion/extension axis at the elbow, and the palmar/dorsal ‰exion and radial/ulnar ‰exion axes at the wrist showed large and positive values, and diŠered signiˆcantly among hitting-point heights. These results indicate that 1) the ‰exion/extension torque at each individual shoulder joint contributes greatly to adjustment of the translational movement of the bat in the vertical direction during the down-swing phase, 2) the adduction/abduction torque at each individual shoulder joint exerts a larger proportion of the longitudinal force of the bat to withstand centrifugal force at a low hitting-point height than at other heights in the level swing phase, and 3) consequently, it tends to be more di‹cult to adjust the bat to the hitting-point at a low height in comparison with other heights.Key wordsclosed loop problem at upper limbs, inverse dynamics calculation, instrumented bat, stationary ball batting キーワード上肢閉ループ問題，逆動力学演算，センサー・バット，静止球打撃

Optimisation of the upper body motion for production of the bat-head speed in baseball batting

“…In the performance simulation, the adjustments to the joint angles were subtle (Table 1, Figures 6, 7 and 8), in particular the knob-side shoulder abduction/adduction angle was not greatly altered; however, the knob-side shoulder abduction torque and elbow extension torque were greatly increased around ball impact (Figure 9). The result also supports previous investigations into the kinetic characteristics of the upper limbs in baseball batting (K. Ae et al, 2014). Prior research has demonstrated that the knob-side shoulder abduction torque exerted around ball impact does not contribute to increases in the bat-head speed due to the large centrifugal force exerted along the longitudinal axis of the bat (Koike & Mimura, 2016).…”

“…The knob-side shoulder adduction/abduction and elbow flexion/extension torques displayed substantial differences between the second and third optimisations. Several studies have concluded that the hand force and joint torque of the knob-side were larger than those of the barrelside in baseball batting (K. Ae et al, 2014;Koike et al, 2004;Koike & Mimura, 2016). The variation of the joint angles in the optimised performance was allowed within ±2 SD of the standard motion data, and the subsequent RMSE of the joint torques was relatively small (Table 2), when compared to the exerted peak joint torques of the upper limbs observed previously (K. Ae et al, 2014).…”

“…Joint angular accelerations were calculated as the second-order differential of the joint angles of the standard motion, which is the relative angle between proximal and distal segments using Euler (Cardan) angle, for use as input to the simulation model. The period of the bat swing was defined as the time from the instant at which the sum of speeds of the bathead and handle exceeded 3 m/s until one frame before ball impact to avoid distortion of the data (K. Ae et al, 2013Ae et al, , 2014Koike et al, 2004).…”

“…In baseball batting, it is not possible to calculate the joint force and torque of the upper limbs due to 'closed loop problem' (Vaughan et al, 1982a(Vaughan et al, , 1982b. The force and moment of the individual hands were distributed by the optimisation procedure, dependent on the measured kinetic variables of the individual hands (K. Ae et al, 2013Ae et al, , 2014Koike et al, 2004). In order to evaluate the accuracy of the simulation model, a root mean squared error (RMSE) between the measured and simulation model data was calculated for the time histories of bat-head speed, bat orientation angle and joint angles (17 DOFs).…”

Development of a rhythmic auditory biofeedback system to assist improving the kinetic chain for bat swing performance

“…We asked the participants to swing a 0.55 kg bat as if they were hitting a ball at belt height in the pitcher's direction ten times. We chose these parameters because previous studies found that swing form is affected by ball speed [22], whether a pitch is a breaking ball [23], ball height [24,25], direction the ball is to be hit [26], and the weight of the bat [27]. We then captured acceleration data, which we used to verify the validity of the system's judgment (i.e., difference between skilled and novice).…”