How Efficiently Does an Athlete Translate Metabolic Power into Speed?
Economy describes the energy cost of locomotion: how much metabolic energy an athlete needs to run, swim, ski, row or otherwise move at a given speed.
It is the translation between metabolic power - the energy the athlete can produce - and external performance - the speed the athlete can achieve with that energy. Better economy means that less metabolic energy is required for the same speed, or that more speed can be produced from the same metabolic power.
That makes Economy one of the most performance-relevant and often overlooked metrics in endurance diagnostics: the athlete’s muscles create the energy, but Economy determines how much speed the athlete gets from it.
Economy: the energy cost of locomotion
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Performance Is More Than just Capacities
VO₂max, VLamax, threshold, fat combustion and carbohydrate combustion describe important parts of an athlete’s physiological capacity. But races are not won by higher VO₂max or more mmol/L of lactate. They are won by the athlete who simply is the fastest.
Two athletes can have very different physiological capacities and still produce the same speed. An athlete with the greater metabolic capacity can be slower if more energy is required to achieve the same speed.
This is the diagnostic blind spot Economy closes.
Speed is metabolic power divided by the energy it costs
Training the correct Limitation
When an athlete is slower than expected, it is easy to conclude that physiological capacity is insufficient. The likely response is then more or harder training to increase an athlete’s capacity.
But the limitation may also be how efficiently an athlete can translate his or her metabolic capacity into speed.
If Economy is not measured, a coach could design a training plan that targets the wrong system. If Economy is measured, the question becomes much more precise: does the athlete need more physiological power, or does the athlete need to convert the existing power into speed more effectively?
The first step toward better training prescription is knowing whether the limitation is the metabolic capacity or the conversion of that engine into speed.
Which limitation is being trained?
Conventionally, running or locomotion economy is often assessed by just looking at oxygen uptake at submaximal speeds. The athlete performs steady-state stages while a metabolic cart measures VO₂, and oxygen cost is related to speed.
VO₂ alone, however, is not identical to locomotion energy demand. The energetic equivalent of one liter of oxygen changes depending on whether the athlete uses more fat or carbohydrates as a fuel. Total measured VO₂ also includes baseline metabolic demand that is not caused by the locomotor task itself.
More importantly, oxygen uptake does not capture anaerobic energy contribution. As intensity rises and non-oxidative energy contribution becomes relevant, a VO₂-only economy calculation increasingly fails to represent the athlete’s complete metabolic energy demand.
Even when substrate utilization and base metabolic demand are accounted for, conventional gas-exchange-only assessments are only valid for low speeds with no significant anaerobic energy component. But this creates a major blind spot: races are not won at low speeds! The economy that really matters is the one at high speeds. But this is where VO₂ only measurements fall short and this is why the economy at race pace stays unknown with conventional testing.
What a VO₂-only measurement sees
Economy with INSCYD - From Low Intensity to Race-Relevant Speed
INSCYD approaches Economy from total metabolic energy demand rather than from oxygen uptake alone. Aerobic and anaerobic energy contributions as well as substrate utilization and base metabolic rate are accounted for.
This allows Economy to be expressed as the relationship between total metabolic power and speed across all speed ranges. The result is an Economy profile that can be used where coaches need it most: not only at comfortable submaximal speeds, but also at high, race-relevant speeds.
Instead of asking how much oxygen the athlete consumes, Economy asks the performance question: how much metabolic energy does this speed actually cost?
Total metabolic demand across the whole speed range
The turning point in athlete communication
Motivating athletes to work on technique can be difficult. For athletes who think in terms of power, calories, speed, training hours etc., technique training is looked at as “touchy, feely” with no clear tangible performance gain, until now. With INSCYD you can visualize the energy demand and speed of individual efforts and compare them with reference data or a comparison group.
That turns the vague statement such as “the athlete needs better technique” into something measurable. Now you can pin a number on the technique of an athlete and clearly show: your technique costs or wins you a certain amount of power or speed over your competition. This changes everything in athlete communication and especially motivation to buy into regular technique training over classic conditioning exercises.
Knowing technique is important is totally different to being able to show and quantify the performance gains by better technique, and this is what you can do now!
Economy
The fastest equipment for any athlete
Economy analysis can also quantify whether equipment actually improves performance. The principle is simple: compare the metabolic energy required to achieve the same speed, or compare the speed achieved at the same metabolic demand with different equipment.
In swimming and triathlon, this can be used to compare wetsuits or race suits. In running, the same approach can be used to quantify the individual effect of different racing shoes or supershoes. Similar comparisons can be applied wherever equipment changes the relationship between metabolic demand and speed: like in canoeing, skiing and many other sports.
The athlete can simply become faster because the energetic cost of locomotion has improved.
This type of analysis has helped athletes globally to win medals. Often the latest piece of equipment or the most expensive one is not the fastest item on an individual athlete.
Equipment B compared with equipment A
Explore other INSCYD metrics.
Aerobic capacity: how much energy the athlete can produce through oxidative metabolism.
Read more VLamaxGlycolytic power: how fast the athlete can produce energy without oxygen.
Read more Aerobic & Anaerobic Energy ContributionHow much of the energy at a given intensity comes from each pathway.
Read more
