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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.

Somebody told the athlete to lean forward to run faster, and they took it to heart. Now they run the whole 200 bent at the waist with their hips out behind them. The advice was not entirely wrong. It was advice about the start of a race, applied to all of it.

The lean changes as the race goes on

Out of the blocks the whole body is tilted well forward, and that is correct. An accelerating athlete needs to push the ground backwards, and a body angled forward is what lets the push go back rather than up. Over the next several steps the body rises gradually, and by the time the athlete is near top speed they are running close to upright, with only a small forward tilt left.

The Film Room holds the two phases to different standards for exactly this reason. Its sprint setting treats upright running as usually sitting around 5 to 10 degrees from vertical, and flags a trunk leaning more than about 20 degrees as folded well forward. Its block start setting does close to the opposite: there, a trunk that is already within about 25 degrees of upright in the drive phase is flagged as standing up too early.

Where the lean comes from

What matters more than the amount is where the lean starts. A lean from the ankles tilts the whole body as one line, from the foot through the hips to the head. A fold at the waist tilts only the upper body, and the hips go back to balance it.

The two can look alike in a still photo and produce very different running. With the body folded at the waist, the thigh has less room to come up in front, so knee lift drops and more of each stride happens behind the athlete instead of in front of them. The hips sit lower and further back, and ground contact tends to get longer. It is a way of working harder to go slower.

Leaning back is the other fault

Late in a race, especially a 200 or a 400, tired athletes often go the other way. The head tips back, the shoulders drift behind the hips, and the feet start reaching out in front. A foot landing ahead of the body brakes on every step, which is a large part of why the last 50 metres of a hard 400 can look like running into a wind that is not there.

What the number can and cannot tell you

The sprint setting measures the angle between vertical and the line from the hips to the shoulders, takes the typical value across the frames it tracked, and reports it against its range. Three things about that number are worth knowing before you coach from it.

• It has no direction. It records how far the trunk is from vertical, not which way, so a runner leaning back 10 degrees and a runner leaning forward 10 degrees get the same reading. The clip tells you which one you have.
• It cannot separate a lean from the ankles from a fold at the waist, since both tilt the line from hips to shoulders. Frame-step to a moment when the foot is on the ground and check whether the ankle, hips and shoulders sit roughly in one line.
• It is one number for the whole clip. Film acceleration and top speed together and you get a blend of two postures that are supposed to be different. If the question is top-speed posture, film the upright part of the run on its own, and use the block start setting for the first six steps.

When the reading does come back folded, the app pairs it with a cue about running tall through the hips and names tall marching with the hips over the foot, a drill that lets the athlete feel the difference between a tall position and a bend at the waist without any speed to hide it.

Leaning further forward at top speed will not make an athlete faster, however much it feels like trying harder. Speed at that point comes from how hard the foot strikes down and back into the ground and how quickly the leg comes through again, and both work best from a tall position.

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