Why Flop High Jumpers Use a J-Curve Run-Up
Why are “flop” high jumpers coached to perform a J-curve run-up?
The answer is that the forces generated by the curved section of the run-up assist the athlete to clear the cross bar.
To fully understand this we need to discuss centrifugal force.
What is Centrifugal Force?
In layman’s terms centrifugal force is the outward pull felt by an object moving on a curved path. It is the force that makes objects move outwards when they are spinning around something or travelling on a curve. It is the tendency of an object to leave a circular path and fly off in a straight line.
Examples of Centrifugal Force
When you swing an object around on a string or a rope, the object will pull outward on the string. This is centrifugal force at work.
Centrifugal force pushes you outwards while you are spinning on a playground roundabout.
It is the effect that you get when you swing a half-full bucket of water in a vertical circle and the water stays in the bucket, even when it is above your head. The centrifugal force is pushing the water to the bottom of the bucket.
Centrifugal Force in High Jumping
In high jump, if an athlete takes off to jump while running a curve, the centrifugal force will pull them outwards towards the landing area.
If used properly, the centrifugal force generated by a curved approach allows a young high jumper to concentrate on jumping UP, rather than OVER the cross bar. The centrifugal force will do the work rather than the athlete having to.
A young high jumper who does not run a curve will have no centrifugal force naturally pulling them towards the landing area. This means that the athlete will have to “dive” towards the bar (and often into it!) as they try to land safely on the mats.
Learning to Lean
To fully capitalise on the curved run-up and the forces that it generates, the athlete must lean away from the bar throughout the curve and up to the point of take-off. In fact the curve and the lean should go hand-in-hand.
If an athlete is leaning away from the bar just prior to take-off, as they begin to execute their jump, the centrifugal force will pull them into an upright position and then hopefully up and over the bar.
If the athlete is running fully upright just prior to take-off (with no lean away from the bar) as they jump the centrifugal force may pull them TOWARDS and possibly INTO the bar.
Worse still, if the athlete is leaning TOWARDS the bar just prior to take-off, as they jump, the centrifugal force will cause them to lean even further in towards the bar, making a clearance even less likely.
A high jump flop run-up is curved in order to take advantage of the forces generated that can potentially assist an athlete over the cross bar. These forces can only be properly exploited if the athlete can maintain a lean away from the bar right up to the point of take-off.
Young high jumpers need to be taught to curve and lean.
Darren Wensor is a sports development professional, coach educator, specialist coach of young athletes and founder of the blog coachingyoungathletes.com. Learn more about him here and connect with him on Twitter, Facebook, Linkedin, Anchor or via email.