Abstract Pexa, BS, Johnston, CD, Elder, EE, Ford, KR, Patterson, MQ, and Myers, JB. Pool-based surfboard elicits activation of posterior shoulder muscles during a surfing stroke. J Strength Cond Res 38(7): 1300–1304, 2024—Surfboard paddling may activate posterior shoulder muscles, which are critical to baseball pitchers' injury risk and performance. The purpose of this study was to measure posterior shoulder muscle activation during different phases of the surf stroke (propulsion vs. recovery) on a pool-based surfboard. Twenty healthy active adult subjects completed a familiarization and testing session with the pool-based surfboard. During the testing session, electromyography (EMG) sensors were placed on 6 posterior shoulder muscles: latissimus dorsi, infraspinatus, posterior deltoid, upper trapezius, middle trapezius, and lower trapezius. Subjects completed 4 laps in a pool at 3 separate resistances (low, moderate, and heavy) in a randomized order. The peak EMG signal during each phase (propulsion and recovery) was recorded. A 2-way within subject ANOVA (resistance-by-phase) with post hoc Bonferroni’s corrections was used to identify differences in EMG activation. There was a significant main effect of phase for the latissimus dorsi ( F = 91.3, p &lt; 0.001), upper trapezius ( F = 36.5, p &lt; 0.001), middle trapezius ( F = 33.8, p &lt; 0.001), and lower trapezius ( F = 21.6, p &lt; 0.001). The latissimus dorsi demonstrated higher activation during the propulsion phase ( p &lt; 0.001), and all trapezius muscles demonstrated higher activation during the recovery phase ( p &lt; 0.001). There was a significant main effect of resistance for the posterior deltoid ( F = 3.4, p = 0.043), with higher muscle activation in the low resistance trials compared with the heavy resistance trials ( p = 0.036). Recreationally active individuals demonstrate activation of the posterior shoulder when using a pool-based surfboard. This pool-based surfboard may be beneficial to activate the posterior musculature and may be more accessible than standard surfing to baseball athletes.

Pool-Based Surfboard Elicits Activation of Posterior Shoulder Muscles During a Surfing Stroke