Lab Rat: Fitness Assessment


If you are like me, you probably “just like to ride” (or run, ski, hike, climb…) and rarely if ever have a specific training plan that gets you to a state of perfect fitness. On the other hand, I DO strive to be in “optimal” fitness at all times which enables me to pretty much jump into anything that comes along. For me, “optimal” translates into a regular exercise routine that consists of cycling a few days a week, running a few days a week, doing functional strength one or two days a week, and one or two full rest days. I adjust the volume and intensity of my activity depending on upcoming events.

In February, Travis Dougan with the SCCA/Starbucks Cycling Team connected me with Steve Crain and Aubrey Kreitzmann of CycleScienceTraining. Given my ambiguous approach to “training,” the initial objective was simply to get to know them and try their basic fitness assessment program, especially the VO2 max test, which I’d never done before.

Although I don’t really “train,” I am of course curious about how my fitness compares to the rest of humanity, and wonder about lifestyle changes that have the potential to improve my “optimal” fitness. So, I connected with Steve and Aubrey.

The initial plan was to post a single report about that experience, but one thing led to another…and after several months I’m still in the process of assessing fitness assessments.

Although still a work in progress, one important “ah hah” during these three months has been a reminder about the importance of the interplay between biomechanics, nutrition, cardiovascular fitness, and functional strength. We get the most benefit when we pay attention to all of them as a unified whole that are integrated into our lifestyles.

Metabolic testing is better than ever. Here is a concise (though oversimplified) overview of the kinds of metabolic tests available and what they can tell you:

VO2 Max:
Is a measure of the volume of oxygen that an individual can uptake. Oxygen is a limiting reagent in the metabolism of the energy-releasing molecule ATP (adenosine triphosphate), so the more oxygen that can be taken in, the greater an individual’s aerobic capacity. As exercise intensity increases, oxygen uptake plateaus, and this is the VO2 max point.

Mid-way through a VO2 max test at Cycle Science Training, Aubrey Kreitzmann takes a blood sample from my ear to determine OBLA.
Mid-way through a VO2 max test at Cycle Science Training, Aubrey Kreitzmann takes a blood sample from my ear to determine OBLA.

VO2 max is considered one of the best indicators of cardiovascular fitness and aerobic endurance, although it is not a predictor of athletic performance. VO2 max is genetic; well-trained individuals are usually already at or near the upper limit of their VO2 max; untrained individuals can usually train to increase their VO2 max to their upper limit.

 A graph of the VO2 max test.
A graph of the VO2 max test.

VO2 max is measured by gradually increasing the effort to pedal (or run) until exhaustion while measuring O2 and CO2 with a mask and tubes attached to “metabolic cart.” The protocol typically takes about 15-20 minutes. VO2 max values for endurance athletes are typically given as ml 02/kg body weight/minute, and range from 35 for sedentary people to the mid-90s for some top athletes. Professional endurance athletes are typically above 60; Miguel Indurain was reportedly in the high 80s.

From my perspective, knowing one’s VO2 max value is probably of most benefit to recreational athletes who are strictly following a training program and have specific race objectives.

Onset of Blood Lactate (OBLA); Lactate Threshold (LT); Anaerobic Threshold (AT):
These are equivalent terms for describing the point at which the body produces lactic acid faster than it can be metabolized. Lactate (lactate is the base form of this molecule, lactic acid is the acid form), is part of the metabolic pathway that occurs during muscular movement when fat and glycogen (the carbohydrate storage molecule) are metabolized. The value you get through a LT test is correlated with heart rate and power, so when you are out on the road there are several ways to monitor effort relative to LT.

A graph of the lactate threshold test.
A graph of the lactate threshold test.

Increasing one’s lactate threshold increases one’s aerobic capacity. The typical prescription is interval training (or fartleks, or high intensity interval training–aka HIIT.) In these kinds of workouts you push past the lactate threshold, followed by short recovery periods below the threshold.

Lactate threshold is a better predictor of performance than VO2 max, and is a better indicator of one’s aerobic capacity than heart rate. Lactate can be measured with a pin-prick blood test, or with a new generation of non-invasive near infrared light sensors such as those produced by Moxy and BSX.

For most of us, lactate threshold is perhaps the most useful metric, but since a blood test or special device is required some folks might be reluctant to get tested.

Functional Threshold Power (FTP)
Is the maximum power (in watts) that can be sustained for an hour. Since no no blood sample or analysis is required, FTP is used as a proxy for lactate threshold. Utilizing FTP is one major reason folks ride with power meters.

The standard test for determining FTP is a one-hour “time trial” effort. In practice, the test is typically done in as a 20 minute test, and the average power is multiplied by 95% to get the FTP value.

In practice, FTP is probably the most useful metric because it is slightly easier to obtain than FTP, and once it’s done gives you an easy ceiling to remember; stay below your FTP on longer rides and you should be able to go all day long.

Metabolic Efficiency Test (MET)
Is a measure of the relative amounts of fat and carbohydrates (and its storage form, glycogen) metabolized during activity. Metabolic efficiency in the context of endurance athletics is defined as the ability to generate the most power while expending the least amount of energy. At the physiological level this translates into training the body to preferentially burn fat over carbohydrates, which is accomplished through a combination of diet and training.

Mid-way through an MET at Real Rehab.
Mid-way through an MET at Real Rehab.

Lean athletes carry between 1,500 – 2,000 calories of carbohydrates, but as much as 80,000+ calories of fat. This means that by training the body to preferentially burn fat over carbohydrates you tap into a significantly larger energy store. For perspective, a 180 lb cyclist pedaling 16-19 mph burns over 900 calories per hour; a ~6 hour century ride at this pace requires about 5,400 calories. With that kind of energy requirement, a body that is adapted to burn carbs will experience energy peaks and valleys, including the possibility of “bonking.” A body that is adapted to preferentially burn fat can go that whole distance without needing any additional food; water and electrolytes are all you need if you keep your level of activity within your personal fat burning zone.

To achieve this, the basic dietary prescription is to reduce grain consumption (grains cause an insulin spike that causes the body to crave more carbohydrates), and emphasize lean proteins, healthy fats, and getting carbs from veggies. The basic cardiovascular prescription is to spend plenty of time (6-7 hours per week) exercising at your own personal optimal fat burning zone. Which feels slow. I’m still in the midst of working on this myself, but local athletes Gina Kavesh and Martin Criminale independently report that by following this kind of program they have lost some weight, increased their lean muscle mass, and have sped up in their respective sports–cycling and ultra endurance running. Read Martin’s detailed report here.

The MET consists of two parts. The first part determines resting metabolic rate: you lay down in a darkened room wearing a mask connected to a metabolic cart–a computer that measures the relative amounts of oxygen and carbon dioxide–for 20 minutes. This determines the relative amounts of carbohydrates and fat that are metabolized at rest.

The active test looks similar to a VO2 max test in that you are set up on a trainer and a mask that is connected to a metabolic cart. The intensity gradually ramps up, but instead of going to exhaustion, the test goes (ideally) until the exercise is intense enough that the body must start using carbs, which are metabolized faster than fats. This point is called the metabolic efficiency point (MEP). According to Matt Hawley at Real Rehab, most people he has tested only metabolize carbs. In fact, I observed a MET in which a fellow preparing for Ironman Canada who metabolized only carbs. To optimize his performance for an Ironman he would need to radically change his diet and training plan to get his body to make the shift to fat metabolism.

Although the concepts related to metabolic efficiency have been known for quite some time, it is starting to get renewed attention from multi-sport and endurance athletes.

I think the average cyclist doing rides of ~4 hours or longer on a regular basis would benefit from integrating metabolic efficiency into their lifestyles.

Critical Power:
Is the maximum peak power (in watts) that can be produced over a short period of time. This is typically done with a Wingate Anaerobic Test, which is an all-out 30 second effort.

Critical power is important for cyclists wanting to develop their ability to break away or sprint.

Maximum Cadence Test (MCT)
Is a ~6 second of all-out effort that shows how fast the legs can spin.

This test is important for cyclists wanting to develop their sprint or time trial technique, or who do multi-sport events.

Body Composition
Is the amount of body fat relative to overall body mass. At Cycle Science Training this is calculated by measuring skin fold thickness at different point on the body and then plugging the numbers into a formula.

Another technique, considered the most accurate, is hydrostatic weighing. In the test the subject is dunked in a tank of warm water and completely exhales while the technician records the body mass. The differences between the body mass while submerged and the body mass out of water are used to calculate the percentage of body fat.

Knowing your percentage of body fat can be a motivator to pay more attention to diet, since for most of us losing some weight can have the greatest effect on performance, especially climbing hills.

Seattle Area Resources:
Cycle Science Training: A full spectrum of testing and analysis, including VO2 max and Moxy to determine lactate threshold.

Cycle University: Offers FTP testing separately and as part of their popular ICE spin class series.

Fit First: Ultra distance runner and coach Jess Mullen provides nutrition-related services to help folks optimize their diets for their athletic goals.

Herriott Sports Performance: A full spectrum of testing and analysis, including Moxy to determine lactate threshold.

Pauole Sports/Seattle Performance Medicine: A full spectrum of testing and analysis, including VO2 max.

Real Rehab: Complete spectrum of testing and analysis, including VO2 max and MET.

Web Resources:
Dr. Phil Maffetone

Bob Sebohar

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