Finish Stronger by maximizing your Economy

Your "economy" or mechanical efficiency (ME) links your sustainable power to your actual performance work rate, velocity or speed.  The better the ME the greater the achieved velocity.  

Your ME is determined by measuring the volume of oxygen taken up by your working muscles at a given sub-threshold exercise intensity. For example, during a bike test your VO2 consumption at a standard power output can be used for comparison. A reduced volume of oxygen at the same power output after repeated testing would suggest an improved oxygen economy and improved performance potential.

At the Fit Stop Lab we measure ME during the Cardio-Metabolic Exercise Profile (CMP) by comparing your actual VO2 ml/kg/min measured at your anaerobic and aerobic thresholds with the predicted VO2 through calculations using the power output. 

We also measure Efficiency and Economy during a 20-minute sub-max exercise test called the Exercise Economy Profile. This test is conducted a couple of days after the CMP and requires performing a 20 minute continuous bike or treadmill test at 80% of your VO2Max.  

Outcomes from the EE Profile include:

GE = The Gross (Mechanical) Efficiency is the ratio of work accomplished to energy expended which describes whole body efficiency. Normal fit cyclists are typically around 20% while Pro Riders average closer to 25%.

EE = Cycling Economy or Running Economy refers to the actual power output generated at a cost of 1 L of oxygen (L= Liter). Highly trained amateurs cyclists generate approximately 75 W/L/min where as the pros are measured in the 85 W/L/min range.

VO2 drift = is commonly referred to as the VO2 slow component. Endurance performance can be enhanced by training to decrease the magnitude of the slow component. World class cyclists show increases of VO2 less than 130 ml over 20 minutes at a work rate of 80% of VO2 max. Unfit or normal fit cyclists will show 3-4 times this amount of drift for 20 minutes at the same relative intensity.  This assessment is a good indicator of how well your aerobic base has been established (or not). Specifically, when you have established a solid aerobic base you will see that during a sub-threshold (below AT) intensity (often best measure is near or at the AeT) the VO2 or heart will maintain a steady straight line consistent with the workrate (i.e., pace or power at AeT).  This is often referred to as "coupling." For more information on coupling check out Joe Friel's article. 

Here is an example of a 20 minute economy test

For more information on fitness testing at the Fit Stop Human Performance Lab go to http://www.fitstop-lab.com/fitnesstesting.htm.

APPLICATIONS

1. For endurance athletes and enthusiasts the benefit of understanding and evaluating your economy is that you can learn to maximize velocities at lower energy expenditure levels by focusing on the appropriate energy systems in training (e.g., zone training).  The right training effect can lead to a faster pace and better conservation of fuel at that pace, while limiting recovery problems.

2. For those individuals who are focused on weight management or more general health and fitness goals the benefit of understanding your economy is two-fold. One, by repeating over and over again the same activities or exercises can lead to mechanical efficiency's that will limit your calorie burn potential.  For example, walking the same flat route over and over again will promote a very efficient walking economy which will lead to faster pace but potentially lower calorie burn.  There is a need then to mix up your routine and the types of exercise.  Two, on the other hand if you plan to go on extensive hikes or other long endurance activities you would like to optimize your economy for that event so that you can finish strong, no matter the distance.