The purpose of this study was to determine and compare the resultant joint torques exerted during similar arm curl exercises performed at slow, medium, and fast rates of lifting using a barbell and a weight machine. Three men experienced in strength-training performed lifts under nine different conditions of load and rate of lifting. The resultant torque at the elbow was determined for one trial under each condition. The following conclusions appear to be warranted:
1. For the seated arm curls performed with a barbell, the resultant elbow torques, exerted at all but the extremes of the range of motion, were independent of the rate of lifting. For arm curls performed with a Universal weight machine, the elbow torques required to lift a given load were independent of the rate of lifting except when the duration of the lift was less than 2 s.
2. Inertial effects were greatest at fast lifting rates and declined asymptotically as the rate of lifting decreased.
3. Because the form of the results for all three subjects was essentially the same despite pronounced differences in the subjects' heights and weights, conclusions based on an analysis of the performances of any other subjects experienced in weight training would probably be the same as those reached in the present study.
If it is accepted that muscular strength can best be increased by repeatedly requiring the muscles to produce forces close to the maximum of which they are capable, as the Overload Principle states, the results obtained in this study also suggest that:
1. For a given load, a fast rate of lifting is likely to yield a slightly better rate of strength development than slower rates of lifting.
2. Neither of the two pieces of equipment used in the study is inherently superior to the other in terms of strength development.