Correlations Between Trunk Static and Dynamic Muscle Strength and Sprint Performance in Adolescent Male Sub-Elite Flatwater Kayakers

Background Flatwater sprint kayaking is a high-intensity speed-based Olympic water sport with substantial physical, technical, tactical, and psychological demands. Among its performance determinants, sprint performance is the key factor for competitive success. However, the role of trunk dynamic and static muscle strength and the sprint performance are yet to be established in adolescent male sub-elite flatwater kayakers. The purpose of this study was to determine the associations between trunk dynamic and static muscle strength, and sprint performance. Method Thirty eligible adolescent male sub-elite flatwater kayakers completed assessments of trunk dynamic and static muscle strength, as well as 200 m sprint trials on a kayak ergometer/dynamometer. Trunk static strength of the abdominal, back, left and right lateral regions was assessed using the Abdomen Bridge Test (ABT), Back Bridge Test (BBT), Left Side Bridge Test (LSBT) and Right Side Bridge Test (RSBT), whereas trunk dynamic strength, including trunk flexion, extension, left and right rotation strength, was evaluated using the 1-min sit-up test (1-min SUT), 1-min back extension test (1-min BET), 1-min Trunk Left Rotation Test (1-min TLRT) and 1-min Trunk Right Rotation Test (1-min TRRT). Sprint performance indicators for the K1 200 m flatwater sprint performance were assessed using a kayak-specific ergometer (Dansprint PRO) and included sprint time (SP), stroke rate (SR), mean and peak velocity (V-Mean and V-Peak), as well as bilateral symmetry of paddling force output (BS-PFO). All tests data for normality (Shapiro-Wilk and Kolmogorov-Smirnov ^a ), and Pearson’s correlation coefficients were calculated with significance set at the standard alpha level (0.05). Results Results indicated that lateral trunk static strength was significantly associated with 200 m sprint performance. Both left and right side trunk static strength were negatively correlated with sprint time (r = − 0.409 to − 0.420, p < 0.05) and positively correlated with peak velocity (r = 0.313 to 0.466, p < 0.05–0.01), whereas no significant relationships were observed for abdominal or back bridge strength (all p > 0.05). In contrast, dynamic trunk muscle strength showed stronger and more consistent associations with sprint performance. Trunk flexion strength (1-min SUT) was strongly related to faster sprint time (r = − 0.658, p < 0.01) and higher stroke rate, mean velocity, and peak velocity (r = 0.328–0.577, p < 0.05–0.01). Trunk extension strength (1-min BET) was positively associated with mean and peak velocity (r = 0.428–0.459, p < 0.01). Additionally, trunk rotational strength (1-min TLRT and TRRT) was significantly correlated with sprint time, stroke rate, and velocity outcomes (|r| = 0.313–0.501, p < 0.05–0.01). No trunk strength variables were significantly associated with bilateral symmetry of paddling force output (all p > 0.05). Conclusion The findings of this study indicate that trunk muscle strength, particularly dynamic trunk flexion and rotational strength as well as lateral trunk static endurance, is closely associated with sprint performance variables in adolescent male sub-elite flatwater kayakers. These results suggest that effective force generation and transfer during sprint kayaking rely heavily on coordinated trunk muscle function rather than ventral or dorsal static endurance alone. Accordingly, training programs for young kayakers should prioritize the development of dynamic trunk strength and lateral trunk stability to optimize sprint performance.