The Variation of Reaction Force when Decelerating an Overhead Barbell

When an athlete holds a barbell overhead, the reaction force is the weight of the barbell on his hand. In the case where the barbell is decelerated upward, the force applied by the competitor varies in relation to the weight of the barbell.

For Acceleration:

Acceleration of the Barbell: When the barbell accelerates upward, the force applied by the competitor is greater than the weight of the barbell. This means that the athlete must exert more force to overcome the inertia of the moving barbell. The reaction force still remains equal to the weight of the barbell, but the additional force applied by the athlete results in a net upward force greater than the weight.

For Deceleration:

Deceleration of the Barbell: On the other hand, when the barbell decelerates upward, the force applied by the competitor is less than the weight of the barbell. In this scenario, the athlete is applying a force in the opposite direction of the motion of the barbell, causing it to slow down. Despite the deceleration, the reaction force remains equal to the weight of the barbell, but the force applied by the competitor offsets part of the weight, resulting in a net upward force less than the weight.