A couple of weeks ago, I ran a clinic for my running friends at Ängby Runners in Stockholm. I brought along a set of small plastic hurdles, about 20 centimetres high, known in running drills as wickets.

The aim was not to force everyone into one idea of perfect technique or encourage them to overthink every step. It was to explore some of the basic principles that can make running feel lighter, smoother and more efficient: posture and balance, rhythm and flow, reducing braking and wasted effort, and allowing the body to move more naturally.

The session was particularly relevant for runners who feel they are working harder than the pace on their watch ought to require.

We placed the wickets in a line on the track, initially 1.20 metres apart. The runners moved through them, placing one foot between each pair, while we gradually increased the spacing by ten centimetres at a time.

The point was not to see who could take the longest stride. Nor was it to prescribe some universal model of running form. We wanted to see what happened when each runner was asked to cover slightly more ground with every step.

At the shorter spacing, almost everyone looked comfortable. The task sat within their existing movement range. But as the gaps widened, the differences began to appear.

Some runners increased their cadence and hurried through the wickets without covering much more ground. Some reached for the next gap, placing the foot further ahead and visibly interrupting their own momentum. Others remained smooth and tidy but simply ran out of projection. They appeared to float across the surface without putting enough force into the ground to cover the larger spacing.

A few runners found something else. Their stride opened without becoming forced. They covered more ground without obviously working harder. Their rhythm remained intact, but the movement became more purposeful.

They projected rather than reached.

By projection, I mean moving the body further through each step rather than merely placing the foot further ahead.

For a moment, the wickets exposed the machinery: running speed is not simply fitness expressed more intensely, but a movement problem that every runner solves differently.

At its simplest, running speed is the product of two things:

Cadence multiplied by stride length.

To go faster, you must take more steps, cover more ground with each step, or combine the two. That sounds straightforward, but there are many ways to create the same pace, and they do not all have the same energetic cost.

One runner may produce speed through a rapid cadence and a relatively short stride.

Another may cover more ground with each step but create substantial braking when the foot lands.

A third may appear smooth and economical but lack the force and structural capacity to increase either cadence or stride length. As speed rises, the additional forces arrive faster than the body can organise them, so the runner simply runs out of options.

The watch may show the same pace. The body may be paying a very different price.

That difference in energetic cost is part of the scientific basis for describing running as a movement skill.

Exercise scientists use the term cost of transport to describe the energy required to move a given body mass over a given distance.

In its simplest form:

Cost of transport = energy used ÷ body mass ÷ distance travelled

Or, in ordinary language:

Running economy is the closely related practical measure: how much oxygen or metabolic energy a runner requires to maintain a particular speed.

Fitness determines how much energy the runner can produce. Economy determines how much speed that energy buys.

This is why two runners with similar aerobic capacities can perform very differently. One converts a greater proportion of the available energy into forward movement. The other loses more through braking, unnecessary muscular work, poor force direction or movement that does not contribute to speed.

The wickets did not change anyone’s aerobic fitness. They changed the movement problem and revealed how effectively each runner could solve it.

Every running step requires work. The runner must support body weight, control the downward movement of the body, maintain forward momentum, reposition the limbs and generate enough force to begin the next step.

Some of this work must be performed actively by muscles. Some energy can be stored temporarily in tendons and other elastic tissues, then returned later in the stride.

A more economical stride does not eliminate work. It organises it more effectively.

Several mechanical features may contribute to a higher cost.

If the foot lands too far ahead of the moving body, the initial braking impulse may increase. The runner loses more forward momentum during contact and must then restore it.

A runner can produce considerable force without organising it effectively for the task. Energy may be spent controlling unnecessary rotation, recovering from an awkward landing or stabilising movement that does not contribute meaningfully to forward progression.

If elastic tissues are not loaded and returned effectively, the muscles must actively perform more of the work. Muscular work has a metabolic cost.

Avoiding braking and unnecessary impact is not enough. To run faster, the runner must also produce force against the ground.

Without enough force, there is little projection. But the problem is not solved simply by increasing cadence. Each quicker contact still has to be organised, resisted and redirected. If the runner lacks the structural capacity to cope with those forces arriving more frequently, cadence itself may also remain capped.

The body must yield when it lands. Running should not resemble a rigid pole striking the ground.

But it must retain enough effective stiffness to store and redirect energy. If the ankle, knee, hip or trunk yields more than the runner can quickly recover from, energy is absorbed rather than returned.

Running skill is therefore not merely about how the movement looks. It changes the forces involved, how the tissues behave, how much muscular work is required and, ultimately, the energetic price of the pace.

The kangaroo is an extreme example of elastic locomotion. Its long, compliant tendons can store large amounts of energy as it lands and return that energy during take-off. As hopping speed increases, elastic return allows the kangaroo to avoid increasing muscular work in direct proportion to speed.

Humans are less specialised. We also use elastic recoil, particularly through the Achilles tendon and the structures of the foot, but human running depends on a changing relationship between active muscular work and stored elastic energy.

We are a motor connected to a spring.

The motor produces force. The spring stores and returns part of it.

The spring cannot return energy that was never stored, and it cannot be loaded effectively if the runner cannot control the forces acting through it.

Too little force and there is little to store. Too little structure and the energy disappears into excessive joint movement and muscular stabilisation. Too much rigidity and the runner pounds against the ground rather than adapting to it.

The skill lies in producing enough force, accepting it and redirecting it at the right time.

Humans are not the fastest animals. We are not the strongest, and we are not the most elastic.

We are unusually good at combining moderate speed with endurance.

Our advantage is not one spectacular adaptation but a system. We can dissipate heat through sweating. We can stabilise the head and trunk while moving. We have long legs, large gluteal muscles and elastic tissues capable of storing and returning energy. We can sustain submaximal movement for hours.

These traits are often discussed in relation to persistence hunting, although the extent to which persistence hunting shaped human evolution remains debated.

The broader point is more secure: the human body contains a suite of adaptations that support economical endurance movement.

But evolution supplied the hardware. It did not guarantee that a modern adult, after decades of sitting, flat surfaces, limited jumping and repetitive movement, would retain the strength and coordination required to use it well.

The ancient engine can become de-tuned.

De-tuned does not mean broken. It means that some of the strength, timing and movement options the system once possessed are no longer readily available.

As we increased the spacing, three responses appeared repeatedly.

They were not diagnoses, and no runner fitted perfectly into one category. They were simply common ways of solving the same movement problem.

The spinner had no difficulty moving the legs quickly. Cadence rose easily, sometimes to very high levels, but each step covered relatively little ground.

There is nothing inherently wrong with a short stride. At easy speeds, it may be entirely appropriate.

The limitation became visible when the runner was asked to go faster or cover a larger gap. Cadence continued to rise because no other strategy was available.

The runner had turnover, but little projection. They were spinning the wheels without fully connecting the engine to the ground.

The answer is not to tell them to reach further forwards. That usually creates braking. The goal is to develop the capacity from which a longer stride can emerge.

The reacher responded to the wider gap by sending the foot forwards.

At first glance, this looked like success. The measured stride was longer. But the extra distance had been created in front of the body rather than through greater projection behind it.

The foot landed further ahead of the runner’s moving mass. Contact became heavier, rhythm was interrupted, and the runner had to travel over the planted leg before continuing forwards.

This is where an apparent gain in stride length becomes expensive. The runner creates braking, loses momentum and must then spend energy restoring it.

The wickets made this visible. At one spacing, the runner moved smoothly. Ten centimetres later, the foot began hunting for the next gap.

The gap should be covered by moving the body further, not simply by placing the foot further away.

The third response was harder to spot because, at first glance, nothing appeared to be wrong.

The floaters looked smooth. They were relaxed, light and rhythmical. They did not spin excessively or reach for the next wicket.

But they also put relatively little force into the ground. They floated across the surface rather than loading it.

As the spacing increased, they did not necessarily make an obvious technical error. They simply ran out of movement. There was not enough force passing through the body and into the ground to produce the required projection.

This matters because running speed is not created by avoiding impact. It requires force.

But the floater’s limitation is not simply an inability to lengthen the stride. They may also struggle to increase cadence, because quicker contacts bring the forces closer together. If the body cannot organise, resist and redirect those forces rapidly enough, there is no easy second route to speed.

They simply reach the edge of the movement they can currently organise.

If they suddenly try to push harder or manufacture a more powerful stride, the body may be unable to hold its position under the increased load. Their restraint may therefore be a solution rather than simply an error. The body has found a way to run within its current structural capacity, keeping the forces manageable while also limiting the speed available from each contact.

Before the floater can move faster, they must develop the capacity to produce more force, accept it and return it quickly enough to repeat the cycle.

The most important thing we saw at the clinic was not that runners could be divided into three types.

It was that every runner had a point beyond which the movement changed.

At one wicket spacing, they flowed. At the next, they began to reach, or they hurried, or the smooth stride simply stopped producing enough movement.

The threshold was different for every runner, but everyone had one.

By movement threshold, I do not simply mean the point at which the runner becomes tired. I mean the point at which speed, duration or accumulated fatigue causes the movement solution to change.

That raised a more important question than who could clear the widest gap:

That is where Part Two begins next week.