Sports Science of Hurdling and Steeplechasing

It is impossible to excel in hurdling and steeplechasing events without basic sprinting or middle-distance running ability. For these races are won mainly on the ground, and therefore the best method of clearing a hurdle or water jump is that which returns the athlete quickly to the track with a rhythm and effort akin to a running action. Hurdling and water jump techniques are therefore modifications of running form.

Hurdling

To avoid jumping—which checks forward momentum and interrupts the running action—good performers at these events clear the hurdles by using a running step-over action of the front leg, combined with a sideways-swinging rear leg movement. In clearing 2 ft 6 in hurdles neither movement is greatly emphasised; but in the men’s 120 yards race, where the barriers are 3 ft 6 in., even a tall, long-legged athlete has to exaggerate them. The technique of the 440 yards intermediate (3 ft) hurdler falls between these two extremes.

The expert hurdler therefore runs over the obstacles mainly by ‘making room’ with his legs, and in the process raises his Centre of Gravity only a little more than in taking a running stride. Thus, in comparison with their times on the flat, champion high (3 ft 6 in.) hurdlers need no more than about 2-0 sees to clear ten barriers—an average of 0-2 sec per hurdle. The figure is fractionally above 1-0 sec in the men’s 220 yards event (10 x 2 ft 6 in.) and women’s 80 metres race (8 X 2 ft 6 in.). Indeed, a few exceptional hurdlers have taken even less time.

Clearance: the flight-path of the Centre of Gravity. The fastest hurdle clearances are those where the athlete’s Centre of Gravity is raised only slightly more than in taking a running stride—theoretically, with the high point directly above the obstacle and with take-off and landing distances almost equal. (Note that even in a running stride the take-off exceeds the landing distance, i.e. relative to the high point of the Centre of Gravity.)

However, in negotiating the obstacles, hurdlers are compelled to raise their Centres of Gravity even higher, and take-off distances are greater because: (i) their approach speeds do not permit the close take-off; they need more distance in which to raise the leading leg; and by taking off farther away, in consequence, must spring higher to avoid dropping on to the hurdle. The Centre of Gravity therefore attains a higher point, in front of the obstacle ; (ii) although even 3 ft 6 in. hurdles can be cleared with the upper body and hips no higher than in running, this can be achieved only through a higher raising of the hurdler’s Centre of Gravity; for, with the raising of the legs, the hips drop in relation to the Centre of Gravity. If the Centre of Gravity were not so raised, the athlete would hit the obstacle.

Of necessity, therefore, even a highly-efficient clearance takes longer than a normal running stride. The distance it covers is also greater, and this, with the take-off to landing ratio, varies from athlete to athlete and, for any one hurdler, from one clearance to another. Distances and ratios are dependent upon: (i) economy of the clearance position. In efficient high hurdling, a pronounced forward trunk lean and correctly timed arm and leg movement provide a ‘lay-out’ of extreme economy. Here the Centre of Gravity is as near to the hurdle as possible for a quick return to the ground. Conversely, a poor ‘lay-out’ wastes time in the air; (ii) height of the athlete in relation to the height of the hurdle.

Compared with a taller athlete (where both are built proportionately and are equal in all other respects), the Centre of Gravity of a short hurdler moves greater vertical distances and therefore takes more time to rise and fall. In consequence his take-off and landing distances are greater.

He will not be at this disadvantage, however, if (e.g. through abnormally long legs) his Centre of Gravity is the same height above the ground at take-off. Using the same approach speed in both instances, an athlete should cover less ground in clearing a low hurdle than a high one; (iii) approach speed. Theoretically an increase in sprinting speed lengthens both take-off and landing measurements. In fact, however, as a hurdler gathers speed over the first few flights so, successively, are increases in take-off distance matched approximately by landing reductions; ratios change, but the overall distance is constant to within a few inches.

Conversely, as speed is lost take-offs shorten and landings lengthen. All this suggests that greater approach speed, with the concomitant lengthening of the take-off measurement, permits a more horizontal drive and a lower, faster clearance; (iv) leading leg action. The faster the pick-up of the leading leg, the closer can the athlete get to the hurdle and the quicker his clearance can be. (This assumes a set speed of approach.) Accomplished hurdlers use a very fast, high leading leg action; flexion at knee and ankle reduces its moment of inertia about the hip joint, allowing maximum angular velocity; and its quick, high movement imparts speed to the hurdler’s Centre of Gravity.

Through the sluggish action of a longer, heavier leading leg, tall hurdlers sometimes squander their height advantage; their take-off is too far back, with the Centre of Gravity raised too much in consequence. Tall men have the edge in these events, yet, through quicker, more exaggerated movements, athletes of a mere 5 ft 8 in. have demonstrated exceptional efficiency in clearing even high (3 ft 6 in.) hurdles. Often, the short hurdler’s difficulty lies much more in having to stride unnaturally between the obstacles.

A combination of fast, high leading leg action, forward lean (marked in high hurdling) and powerful thrust from the take-off leg gives speed to the Centre of Gravity in a more forward direction; the efficient hurdler drives at the obstacles. In this way, athletes of only fair sprinting ability often maintain good average speeds throughout their races; (v) attaining the correct point of take-off. A hurdle can be cleared efficiently only when the point of take-off is commensurate with approach speed, the subsequent raising and lowering of the Centre of Gravity and quickness in front of the obstacle; and it must be reached without overstriding.

If too close, the hurdler has to jump high to avoid the obstacle, getting his high point beyond it. If he is too far away again he must jump high to avoid dropping on to it. Either way, he wastes time, is too erect, hurries the trailing leg, lands heavily and disturbs his sprinting rhythm.

A slightly shortened stride immediately prior to take-off encourages a good forward drive and body-lean, and can lead to a desirable (if only slight) forward rotation of the whole body before leaving the ground.

Although a hurdler running the 120 yards event in 13-4 sees has an average speed of only 26-8 ft per second (18-2 m.p.h.), at top speed in the race he might clear the hurdles at as much as 32 ft per second, i.e. 21-8 m.p.h. The formula d — %gtz can be used to calculate the time taken for his Centre of Gravity to rise specific distances, i.e. from take-off to the high point, and on this basis to estimate its horizontal motion in that time.

But these figures do not represent take-off distances, for at the instant of leaving the ground the hurdler’s driving foot is approximately 1 ft behind his Centre of Gravity (measured horizontally), and his high point of clearance is in front of the obstacle.

To summarise: it is impracticable to lay down precise distances and ratios. In good hurdling: (i) the Centre of Gravity’s high point is as near, horizontally, to the hurdle as possible and is raised little above a normal running position. Controlling factors, here, are leading leg speed at take-off and the economy of clearance position. Thus, the hurdler spends the shortest possible time off the ground; (ii) the hurdles are cleared at maximum horizontal speed. Therefore, provided condition (i) is fulfilled, the greater the distance between take-off and landing, the better. In assessing clearance efficiency, time and distance should always be considered together.

While hurdling events favour tall athletes, short (5 ft 8 in.-5 ft 10 in.) skilful hurdlers lose less time in clearance than is often supposed, for, to some extent, they make up the disadvantage of an initially lower Centre of Gravity by using a closer take-off.

Clearance: other aspects. The following features of leg action are basic to all good hurdling: (i) a pronounced forward take-off drive (ii) a wide separation of the legs immediately after take-off (greatly assisted by a forward trunk lean ; (iii) a fast leg-pivot (i.e. the front leg’s downward-backward motion co-ordinated with the lateral recovery of the rear leg ; (iv) a landing which flows smoothly into the first of the running strides. The hurdler ‘comes down running’.

In all four phases, front and rear leg movements should be regarded as components of a single action. In this respect, the important points are:

Timing of leg action. Ideally, the legs should move fast and continuously throughout clearance, and should be so timed that the front foot lands only slightly ahead of the Centre of Gravity with the greatest possible backward speed relative to the hips. However, as the leg-pivot cannot begin until the front foot is clear of the hurdle, in high hurdling (and with short hurdlers particularly) there must be a split-second pause after take-off to allow the front foot to get into position for downward movement.

Pivot speed is influenced by horizontal speed, and the time spent off the ground. The greater the horizontal speed, the sooner can the front thigh begin its downward movement and the more delayed, relatively, can be the rear leg recovery. Other things being equal, an athlete with high clearance speed is capable of a better pivot timing than a slower hurdler—and obtains a smoother transition into the sprinting action.

A fast pivot, i.e. one related to the cadence of the running action, is the ideal, but this is possible only when the hurdler spends little time in clearing the obstacles. However, the pivot must always be properly co-ordinated; if it is too fast, the front foot lands too far behind the body and the athlete stumbles into a shortened first stride; if it is too slow, he may fail to clear the rear leg safely, or will land with the front foot too far ahead, checking his forward motion.

In general, a delayed rear leg gives faster and more continuous action, subsequently, and better timing and speed on landing. In fact, an efficient downward front leg movement is largely dependent upon the correct timing of the rear leg; a conscious attempt to ‘claw’ with the leading foot is not recommended. The holding of a forward trunk lean encourages and simplifies this delayed rear leg movement.

Absorbing reaction. The leg movements of hurdling are the cause of greater upper body twisting reactions than in normal running. Yet, these reactions can be channelled and absorbed without upsetting balance and running continuity—a simpler problem for flexible athletes.

At take-off the reaction to leg movement is shared between the ground (which reacts by driving the hurdler forward and upward) and the upper body (which absorbs reaction to the eccentric leg thrust— i.e. in a horizontal plane—by its forward lean and pronounced arm action. (The so-called ‘double-arm action’ is contrary to efficient body mechanics, and is not recommended).

However, the body alone can absorb reaction to leg movement originating in the air; and here, action and reaction are in parallel planes, and possess equal and opposite angular momenta about an axis (of displacement) passing through the hurdler’s Centre of Gravity.

As the leading leg moves down and back and, simultaneously, the rear leg recovers laterally , reaction is absorbed: (i) in the horizontal plane , by holding a forward lean, to increase the horizontal distance between the axis of displacement and the secondary axes of the shoulders. Thus, the arms, swung wide of the body to increase their moments of inertia, take up more reaction than would otherwise be possible. This lean also increases the trunk’s moment of inertia about the axis of displacement, enabling the upper body to absorb any further reaction without markedly twisting out of sprinting alignment; (ii) in the frontal plane , by lowering an extended ‘opposite arm’ in its backward swing, whilst simultaneously raising the other, so preventing an exaggerated upper-body tilt towards the rear leg; reaction to counter-clockwise leg movement is absorbed by clockwise arm movement, and vice versa; (iii) in the sagittal plane by a straightening of the upper body. In this plane the legs may be considered to work in opposition; the ‘unjacking’ of the body is caused only by the action of the front leg, for the other perhaps encourages a weak contrary rotation, weak because of the rear leg’s smaller moment of inertia about the

Centre of Gravity (through which the axis of displacement must pass).

Because of the trunk’s greater moment of inertia about this axis, both range and angular velocity of the trunk are far less than those of the leading leg. Moreover, while the leading leg movement blends with, and is quickened by, an overall forward body rotation (due to an eccentric leg thrust at take-off), this same rotation acts in opposition to the trunk’s reaction. Therefore, although the trunk does straighten to some extent, nevertheless it maintains a forward inclination for balance and acceleration on landing.

Steeplechasing

In the course of running 3000 metres, clearing twenty-eight 3 ft hurdles and seven water jumps, in terms of energy expenditure the steeplechaser cannot resort to the crisp, exaggerated hurdling movements of the shorter races. However, as steeplechasing standards improve, so does the general efficiency with which the hurdles are negotiated.

It must be emphasised that the proper hurdling of the twenty-eight 3 ft hurdles is more efficient than clearances where the leading foot is placed on top of the hurdles. This latter method may be necessary for those who cannot hurdle but, since the athlete must raise his Centre of Gravity much too high and interrupt his running action, it is uneconomical. And it is slower, as is very obvious when a ‘hurdler’ and ‘stepper’ clear the last three or four hurdles in a close race. The would-be specialist steeplechaser should therefore master hurdling techniques.

In taking the water jump the skilled performer speeds up several strides before take-off and gauges this spot without chopping or changing stride. For it is essential to accelerate beyond average racing speed in order to negotiate this wide (12 ft) obstacle.

He then springs on to the rail, meeting it just above the hollow of the front foot. Now, by maintaining a crouch position over a bent leg, he reduces the body’s moment of inertia about the supporting foot, thus pivoting quickly and easily forward. The leg thrust (primarily horizontal) is powerfully yet smoothly co-ordinated. The trunk straightens, the rear leg is kept trailing momentarily and the arms are raised laterally for balance correction. The landing (about 2 ft from the water’s edge) is made on one foot and the first stride is taken on to dry land.

Experience proves that although, in the early laps, it is possible to clear the water in one leap from the rail, in terms of energy expenditure this becomes increasingly costly as the race proceeds. It is therefore more economical to negotiate the obstacle in the manner described, and to do this throughout the race.

Sorry, comments are closed for this post.

Share On Facebook
Share On Twitter
Share On Google Plus
Share On Pinterest