Lockie, RG, Schultz, AB, Callaghan, SJ, and Jeffriess, MD. The effects of traditional and enforced stopping speed and agility training on multidirectional speed and athletic function. J Strength Cond Res 28(6): 1538–1551, 2014—This study investigated the effects of a traditional speed and agility training program (TSA) and an enforced stopping program emphasizing deceleration (ESSA). Twenty college-aged team sport athletes (16 males, 4 females) were allocated into the training groups. Pretesting and posttesting included: 0–10, 0–20, 0–40 m sprint intervals, change-of-direction, and acceleration test (CODAT), T-test (multidirectional speed); vertical, standing broad, lateral, and drop jumps, medicine ball throw (power); Star Excursion Balance Test (posteromedial, medial, anteromedial reaches; dynamic stability); and concentric (240°·s-1) and eccentric (30°·s−1) knee extensor and flexor isokinetic testing (unilateral strength). Both groups completed a 6-week speed and agility program. The ESSA subjects decelerated to a stop within a specified distance in each drill. A repeated measures analysis of variance determined significant (p ≤ 0.05) within- and between-group changes. Effect sizes (Cohen's d) were calculated. The TSA group improved all speed tests (d = 0.29–0.96), and most power tests (d = 0.57–1.10). The ESSA group improved the 40-m sprint, CODAT, T-test, and most power tests (d = 0.46–1.31) but did not significantly decrease 0–10 and 0–20 m times. The TSA group increased posteromedial and medial excursions (d = 0.97–1.89); the ESSA group increased medial excursions (d = 0.99–1.09). The ESSA group increased concentric knee extensor and flexor strength, but also increased between-leg knee flexor strength differences (d = 0.50–1.39). The loading associated with stopping can increase unilateral strength. Coaches should ensure deceleration drills allow for appropriate sprint distances before stopping, and athletes do not favor 1 leg for stopping after deceleration.