There are three take-offs in the triple jump, with the first being from the board. The board take-off is a running take-off at a relatively low angle and it's fueled by momentum from the approach acceleration. The second and third take-offs are more of a bound from the floor.
BIOMECHANICAL PRINCIPLES OF VERTICAL FORCE
In utilizing proper sprint mechanics on the approach, the foot should contact the runway beneath the center of gravity (the pelvis region) on the ball of the foot first, and the foreleg generally perpendicular to the ground. There is a vertical component in sprinting -- a slight vertical bounce -- but this vertical displacement is much less than needed to clear the ground on triple jump phases.
In order for the jumper to have time to get the vertical displacement necessary in jump phases, the foot must be planted further out.
PATTERNS AMONG WORLD CLASS TRIPLE JUMPERS
Observation of ground contact photo sequences among the world's best triple jumpers reveals a re-occurring pattern in foot grounding on the second and third phase landings. Both women and men make contact with the runway with the foot AHEAD of the body (see figure 1).
Figure 1 - Hop Phase Landings & Take-Offs
ERROR DETECTION AND CORRECTIONS
- A steep take-off angle off the board will inhibit ground contact distances, whereas low trajectory off the board will set up preferred flight angles and forward foot placements.
- One common cause for a short step (middle phase) is landing the hop with the foot directly under the body upon initial contact -- causing the jumper to tip over. Ideally, in coming off the board the foot cycles from behind the athlete to ahead of the athlete on the hop landing. The foot should not be jammed down to the ground below the body's center of gravity.
- Although minimal ground contact times are necessary to keep the athlete moving, this is relative. There is such a thing as too little ground contact time. The foot must be on the ground long enough for the jumper to produce necessary vertical force to clear the runway.
- Prior to landings, even though the thigh sweeps backwards relative to the body before ground contact; this is a natural motion in reaction to ground speeds. Sweeping or pawing is often unnecessarily cued by coaches.
- An athlete that hunts for the ground will point the foot down (plantar flexed) while still airborne -- this is an error. In contrast, the foot should be in a dorsi-flexed position during flight right up to ground contact.
- Jumpers should wait for the ground to come back to them before each phase landing.
- Ground contact on the hop landing and step landing is full-footed-either flat or heel first.
- Landing the hop and step phases on the ball of the foot first will put the ankle in a weak anatomical position and result in the heel slamming down as a an after-effect-this is the reason for most heel bruise injuries. This error also dampens the power of each take-off.
- Torso posture should be vertical during flight between each landing.
- As with any concept, there can be extremes. If foot contacts are too far ahead on landings the athlete will hit the brakes.
Special thanks to Deutscher Leichtathletik-Verbrand for the use of their photo sequences.
Source: Biomechanics Report WC Berlin 2009 Triple Jump https://www.iaaf.org/development/research
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Robert Marchetti, a former NCAA Division I track coach at Rider University and Columbia University, is a private track and field coach located in Hamilton, New Jersey. For more information, you can email him at firstname.lastname@example.org. You can visit his website at www.coachup.com/coaches/robertm-4