# Neuromuscular Assessment of a Stand-Up Paddle Stroke
###### Abstract  
This study analyzed muscle activity during the stand-up paddle stroke, considering the paddling side and the adjacent and opposing muscles relative to the position of the arms during paddling. Methods: Fourteen male paddleboarders performed three trials covering 195 m in which surface electromyography of the upper trapezius, biceps brachii, triceps brachii, tibialis anterior, and gastrocnemius medialis were recorded (four-cycle strokes on each side). The data were processed according to percentage of maximum voluntary contraction (% MVC). The MVC activation values (uV) for each muscle were then calculated and presented as percentage MVC (% MVC). Results: The recovery phase accounted for 60% of the paddle cycle, while the pull phase represented 39%. During right-side padding, higher % MVC was found in the opposite-side upper trapezius (24.35%, \(p<\) 0.01) during the pulling phase and in the adjacent biceps brachii (8.36%, \(p<\) 0.03) during the recovery phase. In left-side padding, greater % MVC was found in the opposite-side upper trapezius (27.60%, \(p<\) 0.01) during the pulling phase and in the opposite-side triceps brachii (42.25%, \(p<\) 0.04) during the recovery phase. Furthermore, the pulling phase exhibited higher MVC in the opposite-side upper trapezius compared to the recovery phase, both in the right-side (24.35%, \(p<\) 0.03) and left-side (27.60%, \(p<\) 0.01) paddling. Conclusions: these findings help establish the muscular activity of both sides of the paddling technique and the differences between the upper and lower limbs. SUP; paddle sports; muscular activation; EMG; stroke phases Article  
Neuromuscular Assessment of a Stand-Up Paddle Stroke  
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the upper extremities, trunk, hip stabilizers, and knees [9; 17]. During SUP in an ergometer and at sea, it was demonstrated that muscle activation during the water-based test started sooner and was maintained longer than that during the ergometer test [17]. [PERSON] et al. [9] evaluating different postures, found higher biceps brachii activity when paddling on the knees on the board and higher activation of the external oblique and triceps brachii in the standing position. Analyzing the muscles involved in paddling, the upper trapezius is responsible for producing clavicle elevation and retraction relative to the thorax due to its attachment to the distal clavicle [18]. The biceps brachii muscle was found to be primarily activated during the recovery phase and the late pull phase. Its role in this context involves assisting in shoulder flexion, aiding the upper hand (the hand opposite to the one holding the paddle) in lifting the paddle and preparing for the subsequent pull phase [9]. In the case of the triceps brachii, it was observed to mainly engage from the later stage of the recovery phase to the middle stage of the pull phase [9]. The tibialis anterior muscle was noted for its activation in maintaining board balance [19]. Finally, the gastrocnemius medialis muscle was found to be activated during the pull phase, with significantly higher activation levels associated with the task of maintaining balance. This heightened activation can be attributed to the higher center of gravity in the standing position and the increased sway movements, which demanded additional effort to ensure stability [9]. During SUP, paddlers can alternate between left- and right-hand sides for paddling [2], involving pushing cycles, controlling the fluid movement of the board and the relative movements of the paddle and the water, consequently, the paddle has to continuously change his or her basic attitude to adjust trajectory and balance [20]. Therefore, it is important to consider different settings such as the sea and lakes [21]. Thus, during recreational SUP practice, participants often alternate paddling sides based on physical or natural conditions. To date, the understanding of paddling on both sides remains limited.