Why does my sprinter slow down on the curve but not on the straight?
Running a bend costs speed for reasons that have nothing to do with fitness, and most of them are mechanical.
A sprinter who looks fast down the straight and noticeably slower through the bend of a 200 or a 400 is not necessarily undertrained. A curve costs speed on its own, for reasons that have nothing to do with fitness, and most of them are things a coach can actually see on film.
What changes on a bend
Running in an arc means leaning inward to counter the outward pull of the turn, and that lean changes what each leg is doing. The outside leg has to push through a longer, more open stride than the inside leg, and the arms stop moving in a simple front-to-back line to help hold the lean. An athlete who tries to keep straight-line sprint mechanics through the bend is fighting the turn instead of using it, and that fight shows up as lost time.
- Leaning too little into the curve, so the body fights the bend and strains rather than accelerates.
- Leaning too much or too early, which shortens the inside leg's stride and can pull the athlete toward the rail.
- Keeping the arms moving in a straight front-to-back line, when a slight asymmetry through the bend is what actually holds the lean.
What the sprint setting reports, and where it stops
The Film Room's sprint setting reports trunk lean against a 0 to 20 degree range, but that range describes forward lean into the direction of travel on a straight line. Filmed on a curve, the same number does not mean the same thing, because the lean the athlete needs there is partly sideways, not forward, and the setting was not built to tell the two apart.
A camera set up along a bend is watching an athlete cross the frame at a changing angle for the whole clip, not a straight line at a constant distance. That is a different measurement problem than sprinting on the straight. The honest use of the sprint setting is to film the straight sections for the numbers, and judge the curve itself by eye until there is a setting built for one.
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Related
How far forward should a sprinter lean?
A lot out of the blocks, very little at top speed, and never by bending at the waist, which is the version that gets taught by accident.
Read →Why does my sprinter run faster in a relay than in the open 100?
A flying handoff removes the one phase of a sprint an open 100 cannot skip, and that is most of the gap.
Read →Why your sprinter's back leg never fully extends out of the blocks
The rear leg is supposed to finish straight at clearance, and when it does not, the fix is almost never in the leg itself.
Read →Try it: Sprint timer app: 40-yard dash and flying sprints with one phone