How the Body Works: The Jump Serve
By Sarah Walls
The goal of an effective jump serve is to generate maximal
force through a series of muscular contractions and joint actions that is
transferred from the ground through the entire body, up the arm, and through
the final wrist snap. Successful execution leaves defending players only a
fraction of a second to react.
This article will discuss the biomechanics of the jump serve
within four distinct phases:
- Phase
1: Jump
- Phase
2: Arm Cock
- Phase
3: Acceleration/Strike
- Phase
4: Deceleration
Phase 1
The execution of the jump can, again, be broken down into
several stages. These include the preparation, takeoff, and landing.
The preparation phases consists of the approach steps taken
prior to takeoff. Players should focus on a strong eccentric contraction to
transfer the horizontal forces of the approach into the vertical forces needed
for the takeoff. As the jump is prepared for, the forward leg is extended and
the heel is planted – this stops forward momentum. Athletes lacking
strong eccentric strength tend to slow their approach and often drift forward
or laterally during the jump. Generally, athletes who can quickly stop forward
momentum and convert those forces into the vertical plane, the higher the jump
will be.
The takeoff: During the final portion of preparation, the
muscles switch from eccentric to isometric to concentric. When maximum tension
in the muscles is developed, the actual jump (or takeoff) begins.
Landing occurs after arm swing, so although this is jumping
forward a bit, it makes sense to touch on this action now. The majority of
lower body injuries in volleyball occur during landing (any type). Therefore,
careful attention and coaching should be given to this stage. When getting
ready to land from a jump, the feet should be directly under the hips. Upon
ground contact the ball of the foot hits first, followed immediately and
quickly by the heel. The speed with which the ball-to-heel contact occurs is
the key to a safe landing – the quicker, the safer. When practicing
landing technique, an athlete should be coached to pretense the foot and leg
muscles prior to touchdown (still airborne) and mentally prepare for the
impact. Then, the athlete should land softly while focusing on a smooth and
fast ball-to-heel transition.
Primary muscles involved in this phase: gluteus medius,
gluteus maximus, hamstrings, quadriceps femoris, gastrocnemius, tibialis
anterior, soleus.
Phase 2
During the arm cock the thoracic spine rotates in the
transverse plane to create potential energy through the obliques, rectus
abdominus, and lumbar erectors. Simultaneously, the glenohumeral joint abducts
and externally rotates to help create valgus torque on the ulnar collateral
ligament (the elbow). Finally, momentum from the takoff and the actual cocking
of the arm causes a passive length tension relationship to develop in
non-contractile connective tissue. At this point, the arm is ready to swing
forward to make explosive contact with the ball.
Muscles involved in this phase: obliques, rectus abdominus,
lumbar erectors, medial deltoid, teres minor, infraspinatus, biceps brachii.
Phase 3
The striking phase of the jump serve begins the moment the
arm starts to swing forward. This action is quite explosive, but must also be
controlled. First, the shoulder is internally rotated and horizontally adducted
via help from the subscapularis, pectoralis major, anterior deltoid, teres
major, and serratus anterior. Next the triceps brachii extend the elbow.
Finally, the wrist is flexed (or snapped) via a powerful contraction from the
flexor carpi radialis and flexor carpi ulnaris.
Phase 4
After the ball has been hit, the deceleration phase begins
with the purpose being to slow the arm swing and prepare for landing (both
prevent injury). The arm is slowed by the external rotators of the rotator
cuff, rhomboids, and middle trapezius and also through the torque placed on the
posterior deltoid and biceps brachii.
Conclusion
Overall, the entire body must be strong, flexible, and
stable to successfully execute a powerful and controlled jump serve. Assuring
the muscles involved at each joint action in each phase are healthy and strong
will have a big payoff when combined with technical training.
