Surface Electromyography of the Forearm Musculature During the Windmill Softball Pitch

Abstract

Background:Previous studies investigating the windmill softball pitch have focused primarily on shoulder musculature and function, collecting limited data on elbow and forearm musculature. Little information is available in the literature regarding the forearm. This study documents forearm muscle electromyographic (EMG) activity that has not been previously published.Purpose:Elbow and upper extremity overuse injuries are on the rise in fast-pitch softball pitchers. This study attempts to describe forearm muscle activity in softball pitchers during the windmill softball pitch. Overuse injuries can be prevented if a better understanding of mechanics is defined.Study Design:Descriptive laboratory study.Methods:Surface EMG and high-speed videography was used to study forearm muscle activation patterns during the windmill softball pitch on 10 female collegiate-level pitchers. Maximum voluntary isometric contraction of each muscle was used as a normalizing value. Each subject was tested during a single laboratory session per pitcher. Data included peak muscle activation, average muscle activation, and time to peak activation for 6 pitch types: fastball, changeup, riseball, curveball, screwball, and dropball.Results:During the first 4 phases, muscle activity (seen as signal strength on the EMG recordings) was limited and static in nature. The greatest activation occurred in phases 5 and 6, with increased signal strength, evidence of stretch-shortening cycle, and different muscle characteristics with each pitch style. These 2 phases of the windmill pitch are where the arm is placed in the 6 o’clock position and then at release of the ball. The flexor carpi ulnaris signal strength was significantly greater than the other forearm flexors. Timing of phases 1 through 5 was successively shorter for each pitch. There was a secondary pattern of activation in the flexor carpi ulnaris in phase 4 for all pitches except the fastball and riseball.Conclusion:During the 6 pitches, the greatest muscular activity was in phases 5 and 6. Flexor carpi ulnaris activity was greatest among the muscles tested. The riseball had the highest peak activity, but the curveball and dropball had the highest average signal strength. This muscle activity correlates with increasing distraction in the elbow, suggesting that flexor muscles act to counterdistract the elbow as they do for the baseball pitch.Clinical Relevance:Windmill pitchers are unique among overhead athletes as they throw, on average, more pitches per overhead athlete. Understanding the mechanics and physiology of the elbow in windmill pitchers is crucial to prevention and treatment of these increasingly common elbow injuries. This study establishes baseline data that will be useful to further prevent windmill pitch elbow injury.

Sport Biomechanics Applications Using Inertial, Force, and EMG Sensors: A Literature Overview

“…The most common approach to the analysis of sEMG signals is the assessment of the maximum or mean amplitude of the envelope, with or without normalisation to the maximum voluntary contraction [ 71 – 74 , 76 – 87 , 89 – 95 , 97 – 106 ]. The analysis of timing is also common in sport science, with usual approaches ranging from the detection of the onset and offset of sEMG activity and global and local maxima detection to examination of the entire time course using statistical parametric mapping [ 72 – 74 , 76 – 79 , 81 , 83 , 89 – 93 , 96 , 100 , 102 ]. Other advanced approaches include the analysis of the signal's frequency content, especially for fatigue estimation [ 79 , 106 ], classification of sEMG patterns through k -means clustering or support vector machines [ 82 , 88 ], and nonlinear analysis of the signals using the Lyapunov exponents [ 102 ].…”

“…The majority of the studies included the recordings of less than nine muscles [ 72 , 73 , 77 – 85 , 87 , 91 – 95 , 98 – 106 , 158 ], while only a few considered a number between nine and 16 [ 74 , 76 , 86 , 88 , 90 , 96 ] or bigger than 16 [ 71 , 97 ]. Most of the studies considered muscles of the lower limb [ 71 – 73 , 77 , 78 , 81 , 83 – 85 , 89 , 90 , 92 , 93 , 95 , 96 , 98 , 104 , 106 , 115 ], with the remaining focussing on the trunk and/or upper limb [ 74 , 76 , 80 , 82 , 87 , 94 , 100 , 102 , 103 , 106 ] or both the upper and lower body [ 79 , 86 , 88 , 91 , 97 , 99 , 101 ]. Bilateral recordings (involving the left and right hand side of the same muscles) were less common [ 71 , 74 , 77 , 82 , 86 , 88 , 90 , 97 , 98 , 101 ] than ipsilateral [ 72 , 7...…”

“…Most of the studies considered muscles of the lower limb [ 71 – 73 , 77 , 78 , 81 , 83 – 85 , 89 , 90 , 92 , 93 , 95 , 96 , 98 , 104 , 106 , 115 ], with the remaining focussing on the trunk and/or upper limb [ 74 , 76 , 80 , 82 , 87 , 94 , 100 , 102 , 103 , 106 ] or both the upper and lower body [ 79 , 86 , 88 , 91 , 97 , 99 , 101 ]. Bilateral recordings (involving the left and right hand side of the same muscles) were less common [ 71 , 74 , 77 , 82 , 86 , 88 , 90 , 97 , 98 , 101 ] than ipsilateral [ 72 , 73 , 76 , 78 – 81 , 83 – 85 , 87 , 89 , 91 – 96 , 99 , 100 ].…”

“…A lot of attention was also given to resistance training or weightlifting [78,80,81,85,86,94,97,102,103,105,108,125,128] and to cycling or handcycling [71-76, 104, 109, 112, 114, 119, 124]. Swimming is also getting increasing interest in recent years [82,87,91,106,131] as are ball sports such as softball, baseball, or cricket [98][99][100][101]. We found that less attention was given to sports such as rowing [120,134], golf [88,117], rugby or American football [77,137], cross-country skiing [79], gymnastics [135], ice hockey [132], pole vaulting [107], and skateboarding [115].…”

Strength and Motion in the Shoulder, Elbow, and Hip in Softball Windmill Pitchers

“…The three primary softball pitches are the fastball, the rise ball, and the drop pitch. Each of these pitches requires slightly different planes of motion, patterns of muscular activation, and neuromuscular control to be executed effectively, especially in the upper extremity …”