I am pretty much in agreement with Barto.
I always teach a crouch start and a controlled but near-maximal acceleration out of the back. The effort remains high the entire way and there is no obvious 'shifting of gears.'
I am pretty opposed to walk-ins, jog-ins, skip-ins, etc. They just seem to introduce more unnecessary variability to the approach. The most classic example of this is Mike "Foul" Powell, who by many accounts gave up several 8.90+m jumps because of his inconsistent approach.
As for submaximal approach strategies (i.e. starting out slow to build "rhythm") I'm pretty opposed to this also. I think it poses a couple problems. First, it necessitates a longer approach run to get to an optimal takeoff velocity. Any time you lengthen the approach, you're just increasing the likelihood of stride-to-stride variability. Secondly, motor learning research indicates that accuracy tasks (which a jumps approach is if you think about it) are improved with efforts closer to maximum because it is easy for a performer to repeat 100% than it is to repeat 80% (or any other lesser effort).
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