The 400m hurdles, explained. FAQ.

The 400m hurdles is run over exactly 400 metres, one full lap of the track, entirely in lanes.

Each athlete stays in their lane from start to finish. The race starts from blocks, with a stagger between lanes to make up for the length of the bends. It's the same distance as the flat 400m (with ten obstacles / hurdles added along the way).

There are 10 hurdles to clear in a 400m hurdles race.

The first stands 45 metres from the start, then the rest follow every 35 metres. After the tenth hurdle, there are 40 metres of final sprint to the finish line.

The hurdles are 91.4 cm high for men and 76.2 cm for women.

That's noticeably lower than the 110m hurdles (106 cm). The 400m hurdles is generally referred to as a "low hurdles" event, unlike the 110m and 100m hurdles known as "high hurdles". The difficulty of the 400m hurdles doesn't come from the height of the hurdles, but from clearing them in a state of advanced fatigue, with a stride rhythm that shortens as the race goes on.

45 metres separate the start from the first hurdle, then 35 metres between each following hurdle, and 40 metres from the last hurdle to the finish.

These distances are the same for men and women. The interval between hurdles is at the heart of the race: it dictates the number of strides and forces every athlete to build a precise, tailored race plan.

Karsten Warholm holds the men's world record at 45.94, and Sydney McLaughlin-Levrone the women's record at 50.37.

The Norwegian set his time in the Tokyo Olympic final on 3 August 2021, in what remains one of the greatest races in the history of athletics (3 athletes were under the previous world record held by Kevin Young). The American broke her own record for the fifth time in the Paris Olympic final on 8 August 2024.

The lead leg is the one that goes over the hurdle first and horizontally; the other, called the trail leg, follows by folding to the side.

A well-timed clearance costs about three to four tenths compared with a normal stride; a clearance that is forced, off-balance or stuttered into costs far more.

The best men run 13 to 15 strides between the hurdles, the best women 15 to 17.

The longer the stride, the fewer are needed, but the rhythm becomes harder to hold the further the distance covered. Most athletes increase their stride count in the second half of the race, going for example from 13 to 14, then 15.

The race plan is the breakdown of strides between the hurdles, decided in advance by the athlete and their coach.

Example of a race plan: around twenty steps to the first hurdle, 13 strides to the fifth, switching to 14 up to the eighth, then a finish at 15 strides. This plan dictates the whole race: the slightest rhythm error is paid for by stuttering before the hurdle or clearing on the wrong leg, forcing the athlete to readjust for the following intervals.

Because fatigue shortens the stride; to keep attacking the hurdles cleanly, you have to add a stride, sometimes two.

The 400m hurdles is decided in the last 150 metres, when the legs stiffen and the stride length drops. The transition is anticipated in the race plan: better to add a stride at a chosen moment than to be forced into it in a rush in front of a hurdle.

It's better to prepare in advance the hurdles where the transitions will happen, rather than be caught out by them. But being able to adapt to any situation (weather conditions, a clearance mistake, the day's form...) is just as essential.

A successful switch is prepared in training: the athlete learns to recognise the signs of fatigue and loss of stride length, and plans the change before reaching breaking point. Going from 13 to 14 strides flips the lead leg. The transition can be made by slightly shortening the stride (either deliberately or because of fatigue) in the interval concerned.

Being able to attack off both legs offers greater tactical freedom to prepare a race plan: the athlete can change rhythm at any hurdle without stuttering and has a greater ability to adapt to any circumstances (weather conditions, a clearance mistake, the day's form...).

It's insurance against the unexpected — a headwind, early fatigue, a hurdle approached too close. In return, alternating demands double the technical work on both legs. And the "weak" leg often stays less efficient than the preferred one. Many coaches consider it a worthwhile skill to develop in a young hurdler.

Yes, on the bends: leading with the left leg lets you run on the inside line (a shorter path) and reduces the risk of disqualification.

With a left-leg attack, the trail leg (the right) comes round to the outside of the lane, allowing a clearance as close as possible to the inside line. With a right-leg attack on a bend, the athlete has to drift slightly outwards, and the trail leg risks passing beside the hurdle, below the level of the bar — grounds for disqualification. Since half the race is run on bends, the advantage is real but by no means essential at the top level.

On a race run around bends, the outside lanes are more advantageous. They are less tightly curved than the inside lanes, which means less resistance from the centrifugal force (which is greater in the inside lanes).

The inside lanes (1 and 2) force tight bends that break the stride rhythm and complicate clearance on the curve. The outside lanes (7 and 8) offer gentler bends, but the athlete runs there "blind", out in front of everyone, with no read on their rivals until the home straight.

Yes — touching or even knocking over a hurdle is not eliminatory, as long as it isn't deliberate or doesn't give the athlete an advantage.

The World Athletics rules prohibit three things: deliberately knocking over a hurdle with the hand or foot, clearing a hurdle in another lane, and trailing the leg beside the hurdle, below the horizontal plane of the bar. Hitting a hurdle can still be costly: the impact can affect speed and balance.

On average, count 2.5 to 3 seconds more over the 400m hurdles than over the flat 400m for the best specialists. The gap is larger for less experienced athletes.

This differential measures a hurdler's technical efficiency: the best athletes in the world get under 2 seconds. A high differential signals plenty of room for technical improvement; a very low one, on the contrary, indicates that the time is now limited by pure speed.

You can hardly avoid it, but you can learn to run fast in spite of it.

Contrary to popular belief, lactate isn't a waste product but a fuel that the muscle recycles; it's the acidosis accompanying its massive production that "burns" the legs. The answer comes in three parts: specific lactic-tolerance work in training, an effort distribution that delays the suffocation, and an economical clearance technique that wastes less energy hurdle after hurdle.

Source: G. A. Brooks, "The Science and Translation of Lactate Shuttle Theory", Cell Metabolism (2018)

Everything sets them apart except the number of hurdles: the 110m hurdles is a technical, explosive sprint; the 400m hurdles is an event of sustained speed and pacing.

The 110m hurdles are higher (1.06 m versus 91.4 cm for men) and much closer together (9.14 m), cleared in 3 strides (4 steps) over an effort of about 13 seconds. The 400m hurdles plays out over 45 to 55 seconds, with 35-metre intervals and a race run on bends.

On his world record (45.94), Karsten Warholm averaged over 31 km/h (hurdles included).

That's about 8.7 m/s across the whole lap. Early in the race, his top speed exceeds 34 km/h. For the women, Sydney McLaughlin-Levrone's record (50.37) works out to about 28.6 km/h on average.

By recording the split times at each hurdle: it's the basis of any analysis of the event.

On the track or from a video, you time the moment the foot touches the ground after each hurdle clearance. From that you derive the intervals, the number of strides between hurdles, the lead legs, the speed curve, the wear at the end of the race and the consistency of the rhythm. That's exactly what 4h/world offers: enter the times, and the analysis builds itself automatically.

The international convention measures each interval at the "touchdown": the moment the athlete's foot touches the ground after the clearance.

In practice, on the track or on video — ideally frame by frame — you record the moment of each foot strike after the hurdle. The interval between hurdles 3 and 4 is therefore the time elapsed between the foot landing after hurdle 3 and the one after hurdle 4. This method is used in the 4h/world web app.

It's the time an athlete would achieve by combining, in a single race, their best ever intervals on each sector.

On 4h/world, the theoretical potential is computed from all of an athlete's analysed races: best start, best passage between each hurdle, best finish. The gap between this potential and the personal best measures the "hidden" room for improvement.