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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 5 91.3, p, 0.001), upper trapezius (F 5 36.5, p, 0.001), middle trapezius (F 5 33.8, p, 0.001), and lower trapezius (F 5 21.6, p, 0.001). The latissimus dorsi demonstrated higher activation during the propulsion phase (p, 0.001), and all trapezius muscles demonstrated higher activation during the recovery phase (p, 0.001). There was a significant main effect of resistance for the posterior deltoid (F 5 3.4, p 5 0.043), with higher muscle activation in the low resistance trials compared with the heavy resistance trials (p 5 0.036). Recreationally active individuals demonstrate activation of the posterior shoulder when using a pool-based surfboard. This poolbased surfboard may be beneficial to activate the posterior musculature and may be more accessible than standard surfing to baseball athletes. [ABSTRACT FROM AUTHOR]

Single sub-threshold odorants can, according to a few reports, become perceptible in concert. That is, they can exhibit mixture additivity. The present study measured thresholds for mixture of 1-butanol, 2-pentanone, and n-butyl acetate, and for each of these separately. 'Complete' additivity resulted, in that the threshold concentration of each compound in the mixture (measured by gas chromatography) turned out to be one-third of each component separately. Earlier threshold studies also claimed complete additivity and even hyper-additivity (synergism); in this regard they, like this study, differ from the more numerous studies of suprathreshold mixtures, which yield imperfect additivity (hypo-additivity). Mixtures not only enhance sensitivity, but they may also promote stability; intersubject variability was smaller for the mixture than for the components. Subjects were 20 young (18–26 years) and 20 elderly (69–91 years) persons, who gave two sets of thresholds on 2 days. Concordant with earlier findings, the elderly's thresholds averaged higher (≈ 20 times) than the young's, but complete additivity nevertheless held, even though they operated over different portions of the concentration continuum. The study affords a look at inter-test reliability of thresholds by comparing correlations between same and different compounds examined on same and different days.