The influence of arm lowering movements (ALM) on a vertical jump with all but the ankle joints immobilized was studied in five healthy volunteers. Subjects were instructed to rapidly lower both arms after takeoff when jumping from an initial position with the elbows flexed. They performed the jumps either with their hands empty or holding 4 kg dumbbells. ALM prolonged the time subjects were airborne, especially when holding the dumbbells. Protocol for the experiment required that subjects maintain maximum angular velocity of the ankle joint, vertical platform force, and electromyographic monitoring from the triceps surae muscle. Positive acceleration of the head increased in the ALM jumps, and became even more pronounced when the jumps were performed with dumbbells. This increase in head acceleration was inversely proportional to the downward acceleration of the hands. These results indicate that prolonging a vertical jump depends on ALM in the air.