Coach Jeff

Written by Coach Jeff


Long-term development: Why workout times don’t always translate to race day performance

Have you ever had a perfect marathon training cycle and made breakthroughs in all your workouts times, only to find that your workout fitness doesn’t seem to translate to a similar performance on race day? Don’t worry, you’re not alone. This is something many of your RunnersConnect teammates also struggle with and this article is going to attempt to explain why this happens and how it works at the physiological level.

In one of my previous articles, I detailed the process of how long it will take you to benefit from a workout. While that was a useful piece to help identify when you’ll start realizing the benefits of a particular training session on a micro level, I didn’t mention how workouts benefit your fitness in the long-term. However, by understanding how the long-term process of training works, we can shed a little light on why runners can sometimes workout faster than they can race, especially in the marathon.

In non-scientific terms, I call this phenomenon the “backlog” of fitness. Think of it like investing – you’re banking fitness and miles, but you can’t withdraw them yet because the investment hasn’t matured.

Physiologically, this all relates to the development and life-cycle of mitochondria (the aerobic powerhouse that supplies our muscles with energy). By examining how mitochondria contribute to your racing performance and analyzing how they are developed, you get a clear understanding of how this “backlog” of fitness works and why it pays to keep training year after year. (Don’t worry, this isn’t going to be a complicated scientific discussion; I’ll keep things simple and easy to understand, so don’t crucify me if you’re PhD in exercise physiology – that’s not my purpose here.)

First, we’re going to take a look at the role of mitochondria and how they are developed. Second, we’ll examine how the density and volume of mitochondria play a role in both your short and long-term development. Finally, we’ll put it all together for you so you can appreciate how your body adapts to the workload and gets better each training segment. By the end of this article, you’ll have a very clear understanding how micro and macro cycles work in regards to your aerobic progression.

The importance of Mitochondria

Mitochondria are microscopic organelle found in your muscles cells that contribute to the production of ATP (energy). In the presence of oxygen, mitochondria breakdown carbohydrate, fat, and protein into usable energy. Therefore, the more mitochondria you have, and the greater their density, the more energy you can generate during exercise, which will enable you to run faster and longer.

The more mitochondria you have, and the greater their density, the more energy you can generate during exercise, which will enable you to run faster and longer.

Contrary to popular belief, you can increase the volume and density of your mitochondria with both long, slow runs (research study) and more intense training sessions (research study). This is one reason it’s critical to have a mix of training stimuli in your training plan, which includes long runs at both easy and faster paces as well as tempo runs and more intense VO2max sessions. Neglecting one of these energy systems for a long period of time limits your long-term mitochondrial development.

Mitochondria Volume

Now that we can appreciate the value of mitochondria to your performance on race day, we can examine how mitochondria contribute to your long-term development.

Most importantly, the volume (total number) of mitochondria contained in each muscle cell takes years to fully develop. In fact, most coaches believe that you can infinitely increase mitochondria volume; however, there is a point after a few years where increases are minuscule. Therefore, after years of running you’ll develop a mitochondria powerhouse that will enable you to realize continual gains in your fitness.

Mitochondria volume represents the macro cycle of training. Each training cycle, you’ll develop more mitochondria and carry over those positive gains to your next training cycle. It’s a slow process, but it’s why Olympic caliber athletes train for many years to get to the top of their sport. For reference, in The Anatomy of a Medal, Dr. Joe Vigil outlined the training of Deena Kastor during her transition from a good college runner to bronze medalist at the 2004 Athens Olympics. Dr. Vigil attributes the majority of Deena’s success to the slow and gradual progression from 40 miles per week to 110+ miles per week.

Mitochondria Density

The other spectrum of mitochondria development is their density (the size of each mitochondrial). Like volume, mitochondria density can be developed with both slower and faster training sessions. However, mitochondria density is more effected by training volume – the more you run, the faster you will increase the density.

Unlike mitochondria volume, which can be developed infinitely, there is an absolute mitochondrial density that each individual can attain

Unlike mitochondria volume, which can be developed infinitely, there is an absolute mitochondrial density that each individual can attain, usually reached after 8-12 weeks of training. Not surprisingly, this time frame usually correlates with when you start feeling fit during your training segment.

Mitochondria Development and Fitness

The final aspect to consider when looking at the short and long-term effect of training is at what rate you realize the benefits of mitochondria development.

Mitochondria have a half life of one week. Simply speaking, you’re able to gain half of the potential benefits to your mitochondria each week that you train. For example, if went from no training to running 25 miles, you’ll realize 50% of the benefits of that 25 mile week. Run 25 miles the next week at the same intensity and you’ll realize 25% of the benefits from week one. This continues until you reach 100%. Here’s a simple chart to explain it:

Week 150% of benefits of 25mpwup 50%
Week 275% of benefits of 25mpwup 25%
Week 387.50% of benefits of 25mpwup 12.5%
Week 493.75% of benefits of 25mpwup 6.25%
Week 596.88% of benefits of 25mpwup 3.125%
Week 698.44% of benefits of 25mpwup 1.5625%

This is a simplistic progression since it assumes you do not increase you mileage or intensity over this six week period. However, it does demonstrate how you benefit from mitochondria development and how it is critical to slowly increase training stimulus and training volume with time.

Putting it all together

Now that you’ve learned how mitochondria work and how they can benefit you as a runner, how does this relate to the “backlog of fitness” theory mentioned earlier?

The backlog of fitness concept is a result of the micro and macro development of mitochondria. As we’ve seen, on the micro level, mitochondria density peaks at 8-12 weeks of training. Likewise, the positive adaptations to mitochondria you realize from training get smaller and smaller each week. Therefore, at some point within the micro cycle of training, you’re going to stagnate mitochondria development, which is the most crucial component of training. However, you can still improve your running economy, VO2max and lactate threshold, which enables you to run workouts that exceed your marathon ability or readiness.

Luckily, mitochondria development from the macro level never ceases. Each training cycle you complete enables you to develop a greater volume of mitochondria. So, during the next marathon training cycle you tackle, you’ll still be limited to the same relative gains to mitochondria development, but this time you’ll have a greater total number of mitochondria, which means you’ll be better able to capitalize on your fitness on race day.

Your takeaway

Don’t get frustrated when you have a difficult time translating the vast improvement in your workout times to your upcoming marathon. Sometimes, a race that is good but still a little under your expectations is just a sign that you reached a peak at the micro level. However, you’ll be able to carry those benefits over to your next training cycle and realize effects of all the hard work you put in.


Dudley, G. A., Abraham, W. M., & Terjung, R. L. (1982). Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle. Journal Of Applied Physiology, 53(4), 844-850.
Fitts, R., Booth, F., Winder, W., & Holloszy, J. (1975). Skeletal muscle respiratory capacity, endurance, and glycogen utilization. The American Journal Of Physiology, 228(4), 1029-1033.

A version of this post originally appeared at

Free Strength Training Course

The Right Way to Add Strength Training To Your Running to Avoid Injury and Improve Performance

Here’s what we’ve got for you

How the “core” actually contributes to your running and which muscle groups are most important for staying injury-free

Which type of strength training exercises are most likely to directly improve your running performance (based on scientific research)

The 5 most common mistakes runners make with strength training (and how you can fix them)


Connect with Jeff Gaudette on Google+

One Response on “Long-term development: Why workout times don’t always translate to race day performance

Leave a Reply

Your email address will not be published. Required fields are marked *

Adding new comments is only available for RunnersConnect Insider members.

Already a member? Login here

Want to become an Insider for free? Register here