Performance Demands in Softball Pitching: A Comprehensive Muscle Fatigue Study

Background: Monitoring pitch count is standard practice in minor league baseball but not in softball because of the perception that fast-pitch softball pitching is a less stressful motion. Purpose: To examine muscle fatigue after fast-pitch softball performances to provide an assessment of performance demand. Study Design: Descriptive laboratory study. Methods: Bilateral strength measurements (handheld dynamometer) were made on 19 female softball pitchers (mean age [SD], 15.2 1.2 years) before and after pitching a game (mean number of pitches, 99 21; mean innings pitched, 5 +/- 1). A total of 20 tests were performed on the dominant and nondominant sides: forearm (grip, wrist flexion/extension, pronation/supination, elbow flexion/extension), shoulder (flexion, abduction/adduction, external/internal rotation, empty can test), scapula (middle/lower trapezius, rhomboid), and hip (hip flexion/extension, abduction/adduction). Fatigue (percentage strength loss) was categorized based on bilateral versus unilateral presentation using paired t tests: bilateral symmetric (significant on dominant and nondominant and not different between sides), bilateral asymmetric (significant on dominant and nondominant but significantly greater on dominant), unilateral asymmetric (significant on dominant only and significantly greater than nondominant), or unilateral equivocal (significant on dominant only but not different from nondominant). Results: Bilateral symmetric fatigue was evident for all hip (dominant, 19.3%; nondominant, 15.2%) and scapular tests (dominant, 19.2%; nondominant, 19.3%). In general, shoulder tests exhibited bilateral asymmetric fatigue (dominant, 16.9%; nondominant, 11.6%). Forearm tests were more variable, with bilateral symmetric fatigue in the elbow flexors (dominant, 22.5%; nondominant, 19.2%), and wrist flexors (dominant, 21.6%; nondominant, 19.0%), bilateral asymmetric fatigue in the supinators (dominant, 21.8%; nondominant, 15.5%), unilateral asymmetric fatigue in the elbow extensors (dominant, 22.1%; nondominant, 11.3%), and unilateral equivocal fatigue in the pronators (dominant, 18.8%; nondominant, 15.2%) and grip (dominant, 11.4%; nondominant, 6.6%). The mean (+/- SD) pitch velocity was 49 +/- 4 mph, with a small loss of velocity from the first to last inning pitched (3.4% +/- 5.0%, P < .01). Conclusion: Fast-pitch softball pitching resulted in profound bilateral fatigue in the hip and scapular muscles, with more selective fatigue in the shoulder and arm muscles. Clinical Relevance: These findings emphasize the importance of strength in the proximal musculature to provide a stable platform for the arm to propel the ball.