Assessing fitness, strengths, and limiters on the bike

Power Profile

One way to assess our fitness, strengths, and limiters is to look at our power profile. Our power profile is the best power that we have ever produced for certain time periods and gives us some sort of rank. Here are a couple examples of how it looks on Trainingpeaks.

Rider A

Rider B

Rider A is a rock star and wins many races. She has category 1 anaerobic power. We know this based on her 5 second (ATP-PCr system) and 1 minute (glycolytic system) power (more on these energy systems to come). Her 20 and 60 minute aerobic power is ranked as a category 2. This means that it is very hard to drop her during the race and even harder to beat her at the end where anaerobic power is the key. She usually wins races in the sprints and late race attacks.

Rider B has international level pro anaerobic one minute power and domestic pro level aerobic power. Her limiter is a category 4 - 5 second power. Rider B also wins many races but almost always when the course has a big steep climb. She also can make a great late race attack.

Our power profile can tell us some of our strengths and weaknesses. With this information we will know if and where we should attack and where we could be put into difficulty. We can also use it to guide our training and track progress.

Fatigue Resistance

Another way to assess our fitness, strengths, and limiters is our fatigue resistance. Fatigue resistance can mean at least a couple different things. One example of this is comparing a road sprinter to a track sprinter. Who would you pick to win a race to the end of the block? I’d pick the velodrome sprinter because their legs are huge and their peak power is almost always higher. Who would you pick in a sprint to the end of the block after 100 miles of hard racing? Probably the road sprinter.

Fatigue resistance is the reason why rider B from above does win the occasional sprint. If the race is long and hard enough she will make it to the finish line with a lot more gas left in the tank compared to her competitors. If the race is really hard she may get to the finish line with no sprinters at all! Her category 4 sprint will win if everyone else’s sprint turns into a category 5 due to fatigue. So this is one way we can think about fatigue resistance. How long can you go for and how much effort can you put out before your power starts to drop?

Energy System Fatigue Resistance

Fatigue resistance can also look at how our own individual energy systems work. Here is a quick refresher of the three systems our body has to produce energy. The ATP-PCr and glycolytic systems are both anaerobic (do not use oxygen). The oxidative system is aerobic (uses oxygen). At any given moment all three systems are providing us with energy. As the intensity changes so does the percentage of input each energy system is providing. For example, the anaerobic and aerobic systems each provide about fifty percent of the energy when running a mile. Ninety eight percent of our energy comes from anaerobic metabolism during a 100 meter sprint. Ninety percent of our energy comes from aerobic metabolism during a marathon.

The ATP-PCr system provides us with energy for up to a good 10-15 seconds. After that the glycolytic system starts to take over more of the work load. The glycolytic system really shines from ~30-90 seconds but will provide us with the majority of our energy up to around a few minutes. After that our oxidative system provides the majority of our energy. Again, all three energy systems are always working together but the percentage of their input changes based on the duration of our effort/intensity we are working out at in the moment.

So we can say that there are two main ways to produce energy in our body. They are anaerobic and aerobic. There is variation in our fatigue resistance in both systems from person to person. One fascinating example is between Usain Bolt and Wayde Van Niekerk. They are both world record holders with massive anaerobic systems. Check out Usain Bolt’s ranking of his fastest times (at the time of writing this post) for each distance on the track.

• 100 meters - fastest ever time - 9.58 seconds

• 200 meters - fastest ever time - 19.19 seconds

• 300 meters - 3rd fastest time ever - 30.97 seconds

• 400 meters - 588th fastest time ever - 45.28 seconds

This fascinates me so much because all of these races are (almost) purely anaerobic at 45 seconds or less. He dominated in the 100 and 200 meters but only (“only” haha of course I could only dream of running a lap in 45 seconds) managed the 588th fastest 400 meter time. When his glycolytic energy system took over as he approached 30+ seconds he was not as dominant.

Speaking of the glycolytic system Wayde Van Niekerk holds the fastest 400 meters of all time. He holds the 88th fastest 100 meter time. So we could assume Van Niekerk’s glycolytic system is a little better than his ATP-PCr system.

If these two were cyclists Usain Bolt’s 5 second maximum power (ATP-PCR system) would be much higher than Wayde Van Niekerk’s. However, we would say that Wayde’s anaerobic system fatigue resistance was superior. He wouldn’t have as high of a maximum 5 second power but his 45 second power would be much closer to his maximum power than Usain Bolt’s. If we were using this information in a bicycle race we would tell Bolt to stay on Van Niekerk’s wheel until the last moment and then out sprint him. Van Niekerk would need to find a moment Bolt was not drafting on his wheel to sprint long to the finish or find a hard place to attack earlier in the race to use his superior glycolytic system and anaerobic fatigue resistance ability.

This is also what we see between Rider A and Rider B from above.

Rider A - 30.6% drop in power from 5 to 30 seconds - but much higher 5 second power

Rider B - 15.4% drop in power from 5 to 30 seconds

In Summary

These are a bunch of ways we can assess our fitness, strengths, and limiters on the bike.. One is our power profile. How much power can we produce when we are fresh and ready? Another is our fatigue resistance. We can think about fatigue resistance as how much work we can do before our power starts to drop. We can also think about fatigue resistance as the drop off in power within each energy system.

So are we currently a short or long sprinter? Not a sprinter at all? Can we attack and sprint at the end of a race? Are we faster on flats or climbs? Where do we attack? Do we attack? How long of a hill do we look for to attack on? How far from the finish? There are many questions that can be answered by performing some power tests in the next post.

Of course we probably have a good idea about some of the answers if we have been riding and racing for some time. Even if that’s the case, the main benefit to these power tests is that they give us objective numbers and are repeatable. Even if we know what our limiters are on the bike how do we know if our training is actually improving them? By performing these power tests throughout the year and seeing if the numbers are changing.

Check out some of my favorite power tests here.