Surface electromyography of the forearm musculature during an overhead throwing rehabilitation progression program

Abstract

Objective: The flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) provide dynamic stabilization to the medial elbow. It remains unclear how these muscles function during progressive throwing exercises. Our objective was to compare FCU and FDS surface electromyography (sEMG) during a throwing progression.

Design: Crossover.

Setting: Laboratory.

Participants: Sixteen healthy males.

Main outcome measures: Participants completed a plyometric throw (PLYO), long-toss 50% (LT₅₀), long-toss 75% (LT₇₅), and pitch (PITCH). sEMG was synchronized with three-dimensional kinematics to assess the acceleration phase of each exercise. Peak sEMG amplitude (%MVIC) and percentage change between progressive exercises was measured. Continuous sEMG data were assessed to determine when peak activation occurred during acceleration.

Results: FCU activity was greater during PITCH than LT₅₀, and during LT₇₅ than LT₅₀. Percentage change was greater from LT₅₀-to-LT₇₅ than PLYO-to-LT₅₀ for both muscles. PLYO and PITCH increased most during late acceleration, whereas LT₅₀ and LT₇₅ increased most during mid-acceleration.

Conclusions: FCU activity did not increase in a stepwise manner, and FDS remained unchanged. Each muscle demonstrated a disproportionate increase in activation during the second exercise progression (LT₅₀-to-LT₇₅) compared to the first (PLYO-to-LT₅₀), suggesting that additional exercises may be required to achieve a stepwise progression relative to forearm muscle activation.

Keywords: Elbow; Flexor carpi ulnaris; Flexor digitorum superficialis; Rehabilitation.