Assessing curvilinear sprint performance in basketball: The role of stretch-shortening cycle and isometric force-time metrics

Recent research emphasizes the importance of multidirectional movements in basketball. This cross-sectional study examines the differences in stretch-shortening cycle function, strength qualities, and dynamic and isometric force-time characteristics between basketball players with faster and slower curvilinear sprint (CS) performance. Forty-five competitive young male basketball players performed a basketball-specific three-point CS test and were divided into fast (n = 22) and slow (n = 23) groups based on their best CS times. Drop jump (DJ), countermovement jump (CMJ), and isometric mid-thigh pull (IMTP) tests were used to calculate the various force-time curve metrics. Independent samples Welch's t-tests with Hedges' g effect sizes and 95% confidence intervals were used to compare the force-time metrics between the two groups. In the DJ test, significant between-group differences (p < 0.05) with moderate to large effect sizes were observed in ground contact time (g=-0.896, 95% CI [-93.23, -19.28] ms) and its subphases (braking phase time and propulsion phase time), reactive strength index (g = 0.899, 95% CI [0.10, 0.49] m/s), and five other force-time metrics such as take-off peak force in body weight (g = 0.849, 95% CI [0.24, 1.33] BW). In the CMJ test, significant differences were mostly observed in braking-related metrics, including mean braking power (g = 0.789, 95% CI [0.52, 3.76] W/kg) and mean braking force (g = 0.732, 95% CI [0.03, 0.32] BW). In the IMTP test, no significant between-group differences were found in peak force (p = 0.224, g = 0.392), whereas all rate of force development (RFD) metrics showed significant differences with large to very large effect sizes (g = 0.822-1.407). The largest effect was observed for RFD at 150 ms (g = 1.407, 95% CI [1258.68, 3427.52] N/s), which closely matches previously reported ground contact times during CS, highlighting the importance of rapid force production within the brief contact phase that represents the sole window for actively modifying body momentum during locomotion. These findings suggest that DJ reactive strength index, CMJ braking force-time characteristics, and the rate of reaching maximal isometric force, rather than maximal isometric strength itself, in the IMTP test distinguish CS performance in male junior basketball players.