Ingebrigtsen, J, Holtermann, A, and Roeleveld, K. Effects of load and contraction velocity during three-week biceps curls training on isometric and isokinetic performance. J Strength Cond Res 23(6): 1670-1676, 2009-The velocity-specificity principle in training is well established by studies applying isokinetic training devices. However, the contraction velocity during customary resistance training using barbells is rarely stable and can be manipulated in several ways. By manipulating load and intention of movement, the significance of contraction velocity during barbell training on gains in strength-related parameters was investigated. Twenty-seven subjects (divided into 3 experimental groups) performed standardized biceps curls 3 times a week for 3 weeks under the following conditions: high load and slow contraction velocity (HS), high load and fast contraction velocity (HF), and low load with fast contraction velocity (LF). Twelve subjects received no intervention, serving as controls (C). Elbow flexion strength was tested before and after the training period at both isometric and 4 isokinetic contraction velocities (30, 90, 240 and 300°/sec) using a dynamometer. Rate of force development (RFD) was calculated in 100 millisecond epochs from isometric torque curves. Increased maximal isometric strength was seen in HF (9.7%), whereas HS improved slow isokinetic strength (8.5%). There were no improvements in force performance for LF and C. In none of the groups were changes in RFD observed. These findings support the principle of training specificity, highlighting the importance of details concerning contraction velocity on the outcome of resistance training using free weights.