Markers of Endurance Fitness
The three markers of endurance fitness are: aerobic capacity (VO2max), anaerobic/lactate threshold (AT/LT), and economy. Sport science knows less about economy than the other two markers. But it may be the more critical to performance, especially in very long events. Here is a quick summary of economy, and, in Part 2, what you can do to optimize yours.
The less oxygen it takes for you to turn the pedals, run, ski, or swim at any given submaximal workload, the more economical you are.
Race Distance and Economy
The longer the race, the more critical economy becomes. For a triathlete doing an Ironman, this is a huge determiner of performance. For the road cyclist racing a 45-minute criterium, economy is still important, but not nearly as critical to the outcome. The same is true of a 5km race for a runner.
The Ironman bike ride is done at a significantly lower power output than a 45-minute criterium or an 18-minute 5km. The crit and 5km are raced at an intensity between AT and VO2max. So these fitness markers are critical to such a performance. The Ironman is raced at around 70 percent of AT. During such long durations the rider can’t afford to waste energy. The gut has a limit to how much energy it can process from food and drink while racing.
Energy Expended vs. Energy Intake
If the rate at which energy is expended due to low economy is greater than the intake rate, then the athlete will “hit the wall.” On the other hand, the crit racer and 5km runner can afford to waste some of the energy, as their race outcome will not be decided by how much energy is wasted. There is plenty of stored fuel available for such a short race and none will need to be replaced. The key issue for the road cyclist and runner is how to optimize economy in order to produce more power or speed.
When riding, running, or swimming, your economy is likely between 20 and 25 percent effective, meaning that 75 to 80 percent of all the calories you burn are not producing power or speed. Most of the lost energy is expended as radiated heat. That may seem like a lot of lost energy, but it’s common. Interestingly, research reveals that athletes with high aerobic capacities tend to be somewhat less economical than athletes of otherwise similar ability with lower aerobic capacities.
Economy depends on many factors, several of which are outside of your control. As an example, in cycling, economy is somewhat dependent on the length of your thigh bone (long femurs relative to leg length pedal more economically than short ones). For all endurance sports, economy depends in part on the ratio of your slow-twitch to fast-twitch muscles (slow-twitch are more economical). Such physical determiners of economy largely result from your genetics.
The most significant aspect of economy over which you have control is how you physically pedal, run, or stroke. For example, in cycling, “mashers” are less economical than “spinners.” How rapidly and smoothly you apply torque to the pedals has a significant effect on performance.
In “How to Optimize Your Economy, Part 2,” I’ll go over the effective ways to train to improve your economy.