Warm-up jumps (quarter-quicks) consisted of the subject beginning in a standing position then bending the knees until the thigh was 45 degrees to the horizontal. The subject initiated the jump from this position. Upon land- ing, the subject resumed the starting position and pushed off for the next attempt. The half quick jumps consisted of the subject beginning in a standing position then bending the knees until the thighs were approximately parallel to the floor. The subject initiated the jump from this position. Upon landing, the subject returned to the standing position prior to the initiation of the next jump. The contrast jumps were of the same protocol as the quarter quick jumps but with no resistance being applied via the VertiMax®.