The aim was to compare the effect of 2 differing 10-week resistance training programs on the peak power (PP) output, muscle volume, strength, and throwing velocity of the upper limbs in handball players during the competitive season. The subjects were 26 men (age 20.0 +/- 0.6 years, body mass 85.0 +/- 13.2 kg, height 1.86 +/- 0.06 m, and body fat 13.7 +/- 2.4%). They were randomly assigned to 1 of 3 groups: control (C; n = 8), heavy resistance (n = 9), or moderate resistance (MR; n = 9) training, performed twice a week. A force-velocity test on an appropriately modified Monark cycle ergometer determined PP. Muscle volumes were estimated using a standard anthropometric kit. One-repetition maximum (1RM) bench press (1RMBP) and 1RM pull-over (1RMPO) scores assessed arm strength. Handball throwing velocity was measured with (TR) and without run-up (TW). Both training programs enhanced absolute PP relative to controls (p < 0.05), although differences disappeared if PP was expressed per unit of muscle volume. Heavy resistance-enhanced 1RMBP and 1RMPO compared to both MR (p < 0.01 and p < 0.05, respectively) and C (p < 0.001 for both tests). Heavy resistance also increased TR and TW compared to C (p < 0.01 and p < 0.05, respectively). Moderate resistance increased only TR compared to C (p < 0.01). Thus, during the competitive season, the PP, 1RMBP, 1RMPO, and TW of male handball players were increased more by 10 weeks of bench press and pull-over training with suitably adapted heavy loads than with moderate loads. It would seem advantageous to add such resistance exercise before customary technical and tactical handball training sessions.