The vertical jump is important for numerous sports applications. Not only is it a physical test of power for nearly every athlete’s strength and conditioning program, but it’s also an important skill element for many sports, especially basketball and volleyball. In a study this month in the Journal of Strength and Conditioning Research, investigators analyzed the skill portion of the vertical jump.
We usually think of the vertical jump as a power movement. There are some details in form coaches consider to be critical to a good jump, namely a strong counter-movement (when you lower rapidly just before the jump) and good arm action. But aside from these basic components of jumping skill, an athlete’s vertical jump is typically thought of as a pure expression of power.
However, it seems power is not the only factor at play in vertical jump performance. For example, in many lab tests a variable called ground reaction force is used to determine jumping power. Theoretically, the more power you put into the floor, the more power gets put into a jump. The problem is, good jumpers often have lower propulsive ground reaction forces than poor jumpers, which seems contradictory. Similarly, the peak torque at the joints tends to be the same amongst good jumpers and not-as-good jumpers. Therefore, if two jumpers produce the same amounts of power, but perform differently, the skill component must also be of critical importance.
In the newest study, the researchers found vertical leap may be more of a skill maneuver than many coaches and athletes realize. The researchers looked at two components of the vertical leap most thought to influence vertical jump height:
- Sequencing: The first factor the researchers investigated was joint sequencing, which means the order in which the pelvis, hips, knees, and ankles work to produce force. There are two schools of thought on the best sequencing strategy. One is a proximal-to-distal strategy, which means that a jump begins at the pelvis and then moves down the joints of the leg, ending at the ankle. The second is a simultaneous strategy, in which all these joints move at once.
- Arm Action: In addition to sequencing, the researchers considered arm action, which is a better known component of the vertical jump. The researchers were also interested in how arm action affected sequencing.
The researchers found both of these components to be highly influential. Whether the athletes used their arms or not, a proximal-to-distal strategy was superior. Beginning the jump at the pelvis, then moving to the hip and knee (which are mechanically linked), and finally the ankle, yielded the greatest performance, rather than initiating the movement with all joints at once. In fact, the longer the delay between joint activation, the higher the jump. A long delay doesn’t mean a slow jump, but rather a more efficient transfer of energy.
Arm action also improved jump performance. Not only that, but good arm action also meant a longer proximal-to-distal strategy. So even if arm action alone hadn’t directly improved jump height, it contributed to the skill component of a jump, anyway.
Any athlete who wants to improve his or her vertical jump should work on the skill component of jumping and arm swinging. The researchers also noted that these results have applications elsewhere, since the same strategies apply to various loaded exercises, such as cleans. So keep practicing your skill work.
1. Loren Chiu, et. al., “Proximal-to-Distal Sequencing in Vertical Jumping With and Without Arm Swing,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000388
Photo courtesy of Shutterstock.