Physiological Fitness - Aerobic Capacity

Exercise physiologists generally agree that there are only three things you can improve to become physiologically more fit for endurance sports performance: aerobic capacity, lactate threshold and economy. Ultimately, these are the reasons you train. So what are they and how do you improve them? I'll discuss aerobic capacity now and come back to lactate threshold and economy in a few days.

Also referred to as VO2 max, aerobic capacity is your ability to use oxygen to produce energy. The more oxygen your body can process the more energy you can produce and the greater your output (power or pace). It’s common to find that the fastest athletes in a race have the highest aerobic capacities of the entrants. The farther down the race results you go typically the lower the athletes’ aerobic capacities. But don’t take this to mean that knowing your VO2 max tells you how fast you will go or how well you will do compared with others in your race category. The two other physiological factors – lactate threshold and economy – also play a major role in race outcomes. One of these by itself does not constitute all of what it takes to race fast.

Aerobic capacity is literally at the heart of success in endurance sport. Improvements in aerobic capacity have largely to do with how much blood (which contains oxygen) the heart pumps out to the working muscles with every beat. This is called “stroke volume” and has a lot to do with how much aerobic capacity you have. A purpose of training is to improve your stroke volume. There are basically two ways to do this. The first is to focus on the volume of your training. The heart responds to lots of time spent at higher-than-resting intensity (above about 50 percent of VO2 max) by becoming more efficient and effective which ultimately means pumping more blood per beat.

The other way to improve aerobic capacity is by doing high-intensity intervals, especially those done at about the power or pace associated with your VO2 max. At that intensity your heart rate is approaching maximum, so these are very hard efforts. This method will produce a higher stroke volume sooner than by relying only on volume. Most experienced athletes employ both strategies.

There are other physiological contributors to aerobic capacity such as aerobic enzymes found in the muscles, blood vessel diameter and ability to dilate, blood volume and related hematocrit (red blood cells). Many athletes seem to believe their lungs are the deciding factor when it comes to aerobic capacity. Training produces insignificant changes in lung volume.

Body weight also has a lot to do with aerobic capacity. The formula for determining VO2 max is expressed in terms of milliliters of oxygen consumed per kilogram of body weight per minute. What this means is that as you lose body weight, especially fat as opposed to sport-specific muscle, your VO2 max increases. And most of us have experienced this at both ends of the weight spectrum. When we have gained weight it’s harder to run or ride a bike uphill. Conversely, when body weight has been low the effort of exercise is decreased at any given power or pace. This is clearly the affect of body weight on aerobic capacity.

Aerobic capacity is largely dependent on who your parents were. Research (Bouchard, 1986) has shown that identical twins have nearly identical aerobic capacities. While genetics probably sets the boundaries for the upper limit of your VO2 max, proper training can take you to near the upper limit. But also bear in mind that there are two other physiological factors that contribute to endurance performance. I'll come back to them soon (I hope).

Coaching Novice Athletes, Part 6

This is the last of 6 parts on how I coach novice athletes. Note that in the other 5 I have occasionally offered comments on how what I do with novices varies from the way I train advanced or experienced athletes. This last topic is clearly in that area.

6. Anaerobic Endurance. This is the training ability that has the greatest risk-reward associated with it. Doing workouts in this category have been shown to greatly improve aerobic capacity (VO2max), lactate/anaerobic threshold, and economy. And those are the big 3 when it comes to fitness. Lots of reward. But also lots of risk. Injury, illness, and burnout can all result from a steady diet of anaerobic endurance (AE) training. This is the most challenging workout the athlete can do, and since most serious athletes are of the "never enough" mindset, they often take this to the extreme.

So the bottom line is that it is highly unusual for me to have novice athletes do AE workouts. In fact, I can't recall having any do it, but it may have happened a long time ago. If so, someone would bring it to my attention, I'm sure. I seldom have experienced triathletes do AE training also. And then primarily those who are seeking to compete at the highest level at the shorter distances. I have on a few occasions had pro long-course triathletes do shortened versions of AE workouts to bump up their fitness in the late Base period. But this is rare.

For experienced road cyclists AE training is critical to success. Road races often come down to 2- to 3-minute episodes that determine the final selection (the break that succeeds). These episodes are played out on climbs and when there are strong cross winds or when a team is clearly superior. Motivation plays a big role in doing such hard workouts. You have to get "up" for the workout well in advance. This is why road cyclists like to do their group rides. These are usually mini-races made up of lots of AE efforts.

So what is an AE workout? There are many, many variations. Here is the most basic:

5 x 3 minutes at CP6 (3 minute recoveries)

What this means is do an interval workout (after warming up) made up of 3-minute intervals done 5 times for a total of 15 minutes of AE effort. Each interval is done at an intensity of CP6 ("critical power/pace" for 6 minutes). CP6 is the highest, average power or pace you can produce in 6 minutes. This is about your VO2max power/pace. After each work interval recover for 3 minutes.

I call these "intervals til you puke." The name comes from my college track days when all my coach knew were these killer workouts. We did this every day, or some variation on it. Five days a week (we took weekends off back then). There was no reasoning behind it then. No measurement of effort (other than the coach reminding us of how miserably slow we were after he timed each interval as he sat in the stands sipping a soda). It was sickening. Literally. Guys used to vomit during the workout. Someone did that every day. Me included. It's no wonder so many of us were injured and fried by the season's end. We just thought we were wimps.

The variations on AE interval workouts include hills and shortened workout intervals with equally short recovery intervals. Research supports work intervals of as short as 10 seconds for this type of training. The key is to design a workout like this so that it takes on the characteristics of what you will experience in the race for which you are training. AE intervals may be mixed with other ability workouts in the Build period (which is when AE training is usually scheduled) to create workouts that closely simulate race conditions. This could be something such as a muscular endurance steady state followed by anaerobic endurance intervals followed by power repetitions. That's pretty much what happens in a road race.

So there you have it: How I train novice athletes with some stuff on applying the same concepts for experienced athletes. I have glossed over a bunch of stuff here since I'm a bit pressed for time due to travel commitments. But it's still probably more than most of you want to read about. I know, you'd much rather be training than reading about training. If you have a burning desire to know more then consult one of my Training Bible books.

Now, off to Oslo where I will be speaking this weekend.

VO2max and Race Performance

Here's an interesting one. I got an email from a road cyclist who, along with four teammates, was tested for VO2max and various other things recently. He wonders how the data he and his buddies got from the testing could be of help. I'm not going to go into all of that here, but will do so at another time. I'd like to take a look at something else related to the test data - what determines the outcome of races.

To set the stage, here's the most basic data--the tested VO2max of each rider and his power at VO2max:

-Kevin(age 36) VO2max = 65, power at VO2max = @550w

-Mike (age 53) VO2max = 71, power at VO2max = @520w

-Matt (age 43) VO2max = 66, power at VO2max = @500w

-Marc (age 48) VO2max = 56, power at VO2max = @425w

-Nick (age 45) VO2max = 47, power at VO2max = @450w

Not knowing anything else about these riders but assuming all other things were equal, if they each did a 40k time trial who would you put your money on? Would it be Mike with the highest VO2max of 71, Kevin with the highest power output of 550w, or one of the others?

Before answering the question let me tell you more about these two variables. VO2max, also called "aerobic capacity," is a measure of how much oxygen your body uses when exercising at a maximal effort for an extended period of time. It is typically measured with the athlete wearing a breathing apparatus that determines how much oxygen is inhaled and how much is exhaled. The difference is what was used by the muscles to produce energy. The more oxygen one can use, the more aerobically fit that person is. We know that the elite cyclists in the pro peloton all have quite high VO2max levels. Should we test all of the riders at the start of one of the Grand Tours I'm sure we'd find they all are at least at a level of 70 (milliliters of oxygen per kilogram of body weight per minute). The same would be true of the elite male runners at the start of last Sunday's New York City Marathon. The elite women there would probably have tested about 10% lower.

So it sounds like Mike with the highest VO2max is where you should put your money, right? Let's examine this a little closer.

If we did indeed test all of the pro riders at the start line of a bike time trial race and then ranked them from the highest VO2max at the top to the lowest at the bottom, how would that compare with how the race actually finished? Would the highest VO2max win the race and the lowest finish last? Not at all. This has been done in several different sudies and the research has found no relationship between race results ranking and VO2max ranking - among elite athletes. Does that seem strange? Frank Shorter proved a long time ago that it isn't strange at all.

When Shorter was at the height of his running career in the 1970s his VO2max was about 72. That's very pedestrian for a world-class runner. One his top competitors was Bill Rodgers who had been found to have a peak VO2max of about 78. Even though Shorter's was 8% lower than Rodgers' aerobic capacity, Shorter usually won when they went head to head. In fact, Shorter proved to be one of the top marathon runners in the world with Olympic Gold and Silver medals along with wins in most of the major marathons of the day.

Back in 1989 I was invited by a friend to go for a run with Shorter and Rodgers in Boulder, Colorado. It was the first time the two had ever run together in a workout. Running with Shorter on my left and Rodgers on my right it was quite obvious why Shorter was so dominant despite a rather mundane VO2max. He ran like water flowing downhill, like a cloud passing by. There was no excess motion. No wasted energy. He was the definition of smooth. Rodgers, on the other hand, could be seen out of the corner of my eye and appeared to be some sort of Victorian machine with flywheels, crank arms, pistons and steam engines. He oscillated up and down, his arms swung across and around his body, and one leg had a flail to it in recovery. Shorter wasted none of his 72 VO2max; Rodgers wasted a great deal of his.

You see, there's much more to being fast than just aerobic capacity. At the elite level it's just a "ticket to the club." If you want to be an elite athlete you need to have a high VO2max. But that just gets you to the start line. To compete well you also must be economical like Shorter was and you need an anaerobic/lactate threshold at a high percentage of your VO2max. Shorter was undoubtedly excellent in this last category also. I've never seen any numbers on that for him.

Now back to our five teammates... You should be able to pick the TT winner by now. It's Kevin, the one with the highest power output at VO2max. Given the choice of a high VO2max or a high power output at a lower VO2max, always pick power. It should be obvious that the person who can put out the most power when at his top end is the person who is most likely to win. There's a close relationship between power and the results of a race. In the same way, if you know the paces a group of runner can do at VO2max you have the best indicator of how the race results will come out.

Running races and time trials are won by the fastest athletes, not by the athletes with the highest aerobic capacities. It's like asking all of the runners at the 10k starting line in your age group what their best 10k times have been in the last 8 weeks. Assuming comparable courses, you can quite closely predict how the 10k race will finish. Of course, there will be a few minor variations due to motivation, race-morning diet, fatigue, injuries and a few other factors. Power on a bike is much the same. It's a great predictor of performance.

Now with my luck Kevin will post a comment here saying that Mike usually beats him in time trials.