Role of the Long Head of the Biceps During Active Pitching in Healthy Collegiate Athletes: An Electromyographic Evaluation

Abstract

Objectives:Supraphysiologic forces placed on the glenohumeral joint during pitching leads to a high incidence of bicipital-labral pathology in competitive pitchers. Heavy debate in operative management between biceps tenodesis, labral repair, and debridement warrants further study in the role of the biceps during pitching. The purpose of this study was to evaluate the recruitment of the long and short heads of the biceps utilizing electromyographic evaluation and correlate activity with pitch velocity.Methods:Seventeen healthy, competitive, pitchers were recruited and consented to pitch in a controlled laboratory setting, under electromyographic observation. Surface electromyography (sEMG) was performed via electrodes placed on either head of the biceps, deltoid, infraspinatus, and latissimus dorsi, band pass filtered between 10-500 Hz and sampled at a rate of 1500 Hz during the pitching motion. sEMG was normalized to maximal volumetric isometric contraction (MVIC) via manual muscle testing (MMT). Pitch velocity was measured using a Speedster III radar gun, and then correlated to sEMG readings.Results:Average age of recruited subjects was 19.8 ± 1.4 years old. Average number of years pitched was 10.3 ± 3.6 years. Fourteen players reported their highest level of play was college, while two reported semi-professional, and one reported high-school. Average pitch velocity from included pitches was 70.6 ± 4.0 (range: 61 - 79). sEMG signals were interpreted in three modalities: median signal, integral sum of all signals, and time spent (ms) above 10% MVIC. Pitch velocity did not correlate to any sEMG analysis (p>0.05) by bivariate linear regression. Coefficient of variation was greater between pitchers than within pitchers. Greater than 80% of pitchers demonstrated statistically different activation of the long head of biceps muscle (LHBM) versus short head of biceps muscle (SHBM) (Figure 1). Three players had significantly greater short head activation, while 12 players had significantly greater long head activation.Conclusion:The long and short heads of the biceps are consistently activated during pitching, suggested they have a role during the late cocking and deceleration phase of pitching, although not correlated to ball acceleration. Preferential recruitment of either long or short head biceps suggest variability in fast ball pitching styles, that warrant further research for clinical implications.Figure 1.Electromyography time series data demonstrating LHBM dominant pitcher subject 9 (Blue) in comparison to SHBM dominant pitcher subject 10 (Yellow)