KINGOFTHEHILL

In my recent research that which has sought to determine the factors that lead to or cause arm injuries contracted from participation in ball throwing sports such as baseball or football, authors  Arnel L. Aguinaldo and Henry Chambers have provided an eloquent approach of deep research of kinematic chain effects on arm and shoulder injuries. Both research design and measurement methods have been successful in the ability to legitimately determine what factors have leading roles in ball throwing arm injuries.

 

              In this brief review I will summarize the results and conclusions of two recent articles that have sought to determine factors that have an effect of arm related injuries. These articles are related and the most recent (2009) builds on its predecessor.

             

              The first article appeared in the Journal of Applied Biomechanics in 2007, sought determine the effects of upper trunk rotation on shoulder joint torque. This piece was well designed in that it used n=38 pitchers in varying levels of proficiency and age. Motion capture was conducted using eight visible cameras interfaced with a real-time motion capture system which employed 34 anatomical landmarks combined with the Helen Hayes lower body marker set used to bilaterally define the hip, knee, ankle, shoulder, elbow, and wrist joints as well as the upper and lower limb segments. Each pitcher threw 15 off the indoor mound  to a simulated strike zone at a regulated distance of 18.4 m. Pitches were rated by either the pitchers or their trainers on a scale of 1 to 5. One being the worst and five being the best. The highest rated pitch that was able to hit the strike zone and provide usable data was selected.

            

             Results showed that group 1, professional pitchers, rotated their torsos toward home plate with the largest percentage in the pitch cycle (34.3%) and also recorded the lowest shoulder internal rotational torque at 33 N.m. Ball throwing sports require employment of momentum sequentially transferred from larger body segments (legs) to smaller body segments (arms) (Putnam, 1991, 1993; Bahamonde, 2000).  This study concluded that greater shoulder internal rotational torque was increased by increasing the duration of time in the pitching cycle of the; legs, pelvis, and trunk (Aguinaldo & Chambers, 2007). It may then elude further to the fact that these factors build on a kinetic chain to reach maximum angular velocity.

            The second article appeared in The American Journal of Sports Medicine in 2009. This research seemed to explore further information learned in the first. However, in this instance the authors sought to determine the relationship or correlation of throwing mechanics with elbow valgus load in adult pitchers. The research question trying to be answered in this body of research is; Does trunk rotation along with other biomechanical variables that define sequential body motion, will significantly predict elbow valgus loading? n=69 adult baseball pitchers pitched off of an indoor mound during a 3 dimensional motion analysis to measure whole body kinematics and kinetics at 240 Hz. Thirteen biomechanical variables were calculated and extracted for regression analysis to investigate their associations. In addition to a regression analysis an ANOVA between pitchers with two trunk rotation onsets and two arm slot onsets (Aguinaldo & Chambers, 2009).

           

            Results Six biomechanical variables had significant correlations with elbow valgus torque-with peak shoulder external rotation, elbow flexion at peak valgus torque, and elbow loading rate. All of which accounted for 68% of the variance in the model. Reduced elbow valgus torques were associated with increased elbow flexion. Players who initiated trunk rotation before the front contact had significantly higher elbow valgus torques than did those who rotated afterward. This study concludes that there are six factors that contribute to elbow valgus load. It also concluded that those pitchers that rotated later after foot contact had less elbow valgus load (Aguinaldo & Chambers, 2009).

 

 

 

 

 

 

References

 

Aguinaldo, A.L., & Chambers, H.C.,(2007). Effects of Upper Trunk Rotation on Shoulder Joint Torque Among Baseball Pitchers of Various Level. Journal of Applied Biomechanics, 23, 42-51.

 

Aguinaldo, A.L., & Chambers, H.C.,(2009). Correlation of Throwing Mechanics With Elbow Valgus Load in Adult Baseball Pitchers. The American Journal of Sports Medicine, 61, 165-171.