science

Running economy

Running economy is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Running economy rather than just read about it. In short: Running economy (RE) is a complex, multifactorial concept that represents the sum of metabolic, cardiorespiratory, biomechanical and neuromuscular efficiency during running. Oxygen consumption (VO2) is the most commonly used method for measuring running economy, as the exchange of gases in the body, specifically oxygen and carbon dioxide, closely reflects energy metabolism.

Key takeaways

Running economy belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Running economy to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Running economy from memory before moving on to harder problems.

Reference excerpt

Running economy (RE) is a complex, multifactorial concept that represents the sum of metabolic, cardiorespiratory, biomechanical and neuromuscular efficiency during running. Oxygen consumption (VO2) is the most commonly used method for measuring running economy, as the exchange of gases in the body, specifically oxygen and carbon dioxide, closely reflects energy metabolism. Those who are able to consume less oxygen while running at a given velocity are said to have a better running economy. However, straightforward oxygen usage does not account for whether the body is metabolising lipids or carbohydrates, which produce different amounts of energy per unit of oxygen; as such, accurate measurements of running economy must use O2 and CO2 data to estimate the calorific content of the substrate that the oxygen is being used to respire. In distance running, an athlete may attempt to improve performance through training designed to improve running economy. Running economy has been found to be a good predictor of race performance; it has been found to be a stronger correlate of performance than maximal oxygen uptake (VO2 max) in trained runners with the same values. The idea of running economy is increasingly used to understand performance, as new technology can drastically lower running times over marathon distances, independently of physiology or even training. Factors affecting running economy include a runner's biology, training regimens, equipment, and environment.

Measurement and values

Measurement Running Economy is calculated by measuring VO₂ while running on a treadmill at various constant speeds for anywhere between three and fifteen minutes. VO₂ is the amount of oxygen consumed in milliliters over one minute and normalized by kilogram of body weight. To compare running economies between individuals, VO₂ is interpolated to common running velocities while also quantifying how much oxygen is needed to run one kilometer relative to body mass. A lower value of running economy demonstrates better running efficiency and provides a good predictor for race performance. A new method for measuring such concepts can be found with the help of the use of wireless foot-worn inertial sensors together with dedicated signal processing algorithms.

Values of running economy

Factors affecting running economy There are a number of variables that may affect running economy: vertical motion while running, the ability of the muscles to absorb energy during the shock of landing and transfer it to push-off, biomechanical factors, technique and type of activity, fitness and training, age, fatigue, gender, race, weight of clothing and shoes, and environmental conditions. Various studies have shown marathon runners to be more economical than middle distance runners and sprinters at speeds of 10 to 19 kilometres per hour (6 to 12 mph). At those speeds, film analysis has shown that sprinters and middle distance have more vertical motion than marathoners.

Anthropometry

Running economy also depends on many innate characteristics with some body characteristics naturally giving runners an advantage. Some of these include height, limb length, and body mass distribution in certain areas of the body. Limbs are a greater distance from a person's center of mass, so they have greater rotational inertia compared to the rest of the body. As a result, limbs require more energy to move, so their morphology plays a role in running economy. In the legs, an increased weight in the feet relates to running economy since they are located most distally from the hips, slightly smaller than average feet are ideal for optimizing running economy. This is also why shoe choice affects running economy. Weight carried in the thighs also plays a role with weight distributed closer to the hip joint, but does not affect running economy as much as foot morphology. In one study, weights were added to the runners' feet and thighs and they found that VO₂ consumption increased twice as much in trials with weights on feet compared to thighs. While the distribution of mass in limbs has been correlated to running economy, there is no consensus on whether or not limb length is a factor. An ideal body for optimal running economy would include height slightly smaller than average for males and slightly greater for females, low body fat percentage, leg mass distributed closer to the hip joint, and a narrow pelvis with smaller than average feet. It has also been shown that there might be an inverse relationship between body weight and running economy. However this relationship is small, as the energy used in running is similar among people of different sizes. It's also possible that this relation has nothing to do with body mass and could be caused by inter-individual differences in physique.

Physiology

There are many physiological conditions that can affect running economy including maximal oxygen uptake, metabolic factors, tendon length, and ventilation. Running economy has also been observed to decrease towards the end of races while core temperature, heart rate, ventilation, and lactic acid increase. Therefore, training to decrease those factors could improve running economy. Metabolic energy is the amount of energy (ATP) that the body can produce from oxygen intake and nutrients available in the body. Factors that affect metabolism would be important for improved running economy so as to efficiently utilize the body's resources. Because oxygen is necessary for aerobic respiration, the higher VO₂ max a runner has, the longer they will be able to run without going into anaerobic respiration and accumulate lactic acid buildup. It is also preferable that a runner's body can burn fat as an energy source under intense work loads, in addition to carbohydrates. Fat takes more steps to metabolize than carbohydrates, so using them as an energy source is more expensive, but they contain more energy per molecule. When running, the Achilles tendon becomes stretched by flexion of the foot and stores some of that energy as elastic energy. Studies have shown that utilization of this elastic energy has a medium to large impact on reducing running energy. Energy stored in the tendon depends on how much the tendon is stretched and its internal properties. A shorter Achilles tendon moment arm length (the length between the tendon and force stretching it) will produce more energy, similar to how tightness in muscles stores and releases elastic energy.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Running economy

Start with the simplest possible case. Write down what Running economy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Running economy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Running economy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Running economy

In research: Running economy appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Running economy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Running economy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exercise physiology, Running, Sport of athletics terminology, so understanding it makes those chapters shorter.
In everyday life: Look for Running economy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Running economy in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Running economy means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Running economy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Running economy in simple terms?

Why does Running economy matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Running economy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Running economy.