Longitudinal Change of Forearm-Hand Inertia Value and Shoulder Musculature Using Dual X-ray Absorptiometry in Youth Japanese Baseball Players: Implications for Elbow Injury.

Toshiharu Tsutsui,Suguru Torii,Satoshi Iizuka,Toshihiro Maemichi

doi:10.3390/sports8120152

Toshiharu Tsutsui, Suguru Torii + Show 2 more

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https://doi.org/10.3390/sports8120152

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Journal: Sports	Publication Date: Nov 25, 2020
Citations: 2	License type: CC BY 4.0

Affiliation: Waseda University, Japan Sport Council

Abstract

It is important to understand the timing of the maximum increase of forearm-hand inertia value and lean body mass (LBM) of the shoulder girdle musculature when elbow injury frequently occurs. This study aimed to clarify the discrepancies of those in youth baseball players. Forty-three male baseball players (8- to 14-years-old) participated in this study. The forearm-hand inertia value and LBM of the shoulder girdle musculature were calculated using dual-energy X-ray absorptiometry (DXA). A cubic spline fit was applied to the annual increase forearm-hand inertia value and LBM of the shoulder girdle musculature for each chronological age and years from peak height velocity (PHV) age. As a result of cubic splines fitting, the peak timing for forearm-hand inertia value and LBM of the shoulder girdle musculature was 12.42 and 12.75 years in chronological age, −0.66 and −0.11 years in PHV age. Therefore, the peak timing of forearm-hand inertia value was about 4 months earlier in chronological age and half a year earlier in PHV age than LBM of the shoulder girdle musculature. Acquiring sufficient shoulder girdle musculature during the period when the growth of the shoulder girdle musculature cannot catch up with forearm-hand inertial value is necessary to reduce the elbow load while throwing.

Highlights

Baseball is a popular sport all over the world, and many children start playing it at an early age.As an injury specific to youth baseball players, elbow injury is reported to occur in approximately a quarter of the pitchers aged between 9 and 12 years [1,2]
According to a report investigating the relationship between the elbow varus torque during throwing and the segment mass of the upper limb by using dual-energy X-ray absorptiometry (DXA), the elbow varus torque has a positive relationship with the mass of the hand and forearm [9]
It is important to understand the timing of the maximum increase of forearm-hand inertia value and the lean body mass (LBM) of the shoulder girdle musculature during the ages at which elbow injury frequently occurs

Summary

Introduction

As an injury specific to youth baseball players, elbow injury is reported to occur in approximately a quarter of the pitchers aged between 9 and 12 years [1,2]. The suggested risk factors for elbow injury in youth baseball players are mostly associated with pitching. These risk factors include the number and frequency [3,4], position [1,5], bad posture, flexibility of the lower limb muscles [6], and poor throwing biomechanics, like lowering the position of the elbow and using only the elbow to the periphery [7]. According to a report investigating the relationship between the elbow varus torque during throwing and the segment mass of the upper limb by using dual-energy X-ray absorptiometry (DXA), the elbow varus torque has a positive relationship with the mass of the hand and forearm [9]

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