Mathews, M, O'Conchur, C, and Comfort, P. The acute effects of heavy and light resistances on the flight time of a basketball push-pass during upper body complex training. J Strength Cond Res 23(7):1988-1995, 2009-The aim of this study was to investigate the acute effect of high-load and low-load complex training on upper-body performance-determined by the flight time of a basketball push-pass. Twelve competitive male athletes (21.8 ± 4.5 years, 82.0 ± 11.7 kg, 181.6 ± 5.6 cm), with at least 6 months weight training experience and no musculoskeletal disorders, undertook 3 testing conditions. Condition 1 involved 5 repetitions at 85% of a 1 repetition maximum (1RM) bench press; Condition 2 involved 5 repetitions of a 2.3-kg medicine ball push-pass; and Condition 3 was the control, where participants rested for the equivalent time of the other conditions (∼20 seconds). Each condition was preceded and followed by an electronically timed basketball push-pass. Results indicate a significant (3.99%, P = 0.001) reduction in flight time following the completion of Condition 1 (85% 1RM) but no significant changes (1.96%, P = 0.154) were seen following Condition 2 (medicine ball push-pass). Furthermore, there was a significant difference (P = 0.016) between Condition 1 (85% 1RM) and Condition 2 (medicine ball throw). This study appears to confirm previous research suggesting that high loads are required to elicit a potentiation effect. For those athletes wishing to produce a short-term enhancement of power, they should consider loads in the region of 85% 1RM. Results with the lower load showed greater variation, with some individuals responding and others not. Because there appears to be an individual potentiation response to lighter loads, we recommend that, when equipment is limited, athletes and coaches experiment with a range of loads when performing contrast training.