Coaches are constantly adjusting their training plans as new research emerges, revealing more effective ways to develop athletes to their peak potential. This is a huge advantage for competitors today, especially with information being more accessible than ever. However, coaches ultimately decide which training methods they implement. Many still hold onto old-school conditioning philosophies—one of the most debated being the heavy use of distance workouts for sprinters. At first glance, these workouts may seem counterproductive for athletes who rely on explosive speed over short distances. While excessive distance training may not be the most efficient way to develop top-end speed, there is scientific evidence suggesting that, when applied strategically, it can offer benefits to sprinters.

This is one of three articles that will break down three key scientific factors that explain how distance training can impact sprinters through muscle fiber adaptation, aerobic capacity, and endurance in both recovery and mental resiliency. Understanding these principles will help you see the bigger picture of how distance workouts, in moderation, can play a role in your speed development.

Why You Need To Know How Distance Workouts Affect Your Speed

If you’re reading this as an athlete, then you’ve already ventured deep enough into your sport to know too much for your own good. Yes, it’s possible to know too much. What do I mean by this? Being able to question your coach is both a gift and a curse. On one hand, it shows you’re invested in your performance and starting to think critically about training. On the other, it can lead to second-guessing workouts. You will start holding back in practice because you’re unsure if what you’re doing is actually helping. You may even go as far as outright ignoring your coach’s workout. I’ve been guilty of this myself. It frustrated me to see other athletes doing workouts that seemed more tailored to their events. But training isn’t always as simple as doing whatever looks best on paper.

Understand Your Coach’s Perspective

Your coach is in their position for a reason—they care. It’s their job to train you based on what they believe is best. Once I realized this, I had to adjust my mindset about distance workouts. Technically, I’m a sprinter, but my coach wasn’t making me run distance every day. The workouts had a place in our structured training week. When I really thought about it, they made a lot of sense.

The purpose could be to add volume, aid in recovery, or target specific energy systems and muscle fibers that might otherwise be neglected or overused. These workouts can be the bread and butter of your sprint program when implemented correctly. Even if your coach isn’t thinking that far ahead, you can. Understanding the reasoning behind these workouts allows you to commit fully to your training regimen.

Before we break this down, understand that what you’re about to learn is a deep dive into the science of sprint performance. It’s a lot to take in, but every piece of it is crucial if you want to maximize your speed and endurance without wasting your training.

Muscle Fiber Type Adaptations

As runners, we use every system the body has in order to perform at our absolute best. The muscle fiber adaptations we make should be intentional. We have three main muscle fibers with the addition of one crucial muscle fiber that is lesser known: Type l, Type lla, Type llx, and a Type l/lla hybrid. I’ll explain how these fibers function for our benefit as well as how we train them. Then we’ll discuss the crucial development of the Type l/lla hybrid fibers from distance training primarily.

Look at the graph above. The first muscle fiber recruited is always Type I, also known as the slow-twitch fiber. These fibers are oxidative and have a slow nerve conduction velocity, meaning they take longer to produce a muscle twitch compared to other fibers (The Movement System, 2020). While they generate less power, their high fatigue resistance and aerobic base make them essential for longer sprints. In fact, sprinters rely on slow-twitch fibers for roughly 30-40% of their race. The catch? The more you train slow-twitch fibers, the less time you spend developing the more explosive and demanding fibers—Type lla and Type llx—which are critical for sprint performance.

The Importance of Every Muscle Fiber In Sprinting

Type I fibers become most useful in sprints when Type lla and Type llx fibers fatigue. Type lla fibers, known as fast oxidative, are aerobic-based like Type I but generate more power with slightly lower fatigue resistance (The Movement System, 2020). These fibers dominate during the majority of a long sprint.

“In humans, type I, or slow-twitch, fibers possess slower twitch speeds and are relatively fatigue resistant. Type IIa fibers, or fast oxidative glycolytic (FOG) fibers, present higher twitch speeds than type I fibers but are less fatigue resistant. Type llx fibers, or fast glycolytic fibers, possess the fastest twitch speeds but are highly fatigable [1].”

(Plotkin et al., 2021)

Once Type lla fibers reach their peak, Type llx fibers take over. These fast glycolytic fibers rely on anaerobic energy and are responsible for the explosive speed at the start of a race. However, they fatigue the fastest. If you’re only used to recruiting these fibers in your race, you’ll accumulate an extreme excess of lactic acid, which can destroy your performance. Hence, you should be developing more Type lla fibers, alongside Type l/lla hybrid fibers we have yet to get into.

Here’s an Example

Imagine you’re picking up a weight slowly—you’re primarily recruiting Type I fibers. Now, if you lift the weight faster, your body starts recruiting Type lla fibers. But if you attempt to lift it as fast as humanly possible, Type llx fibers come into play after the Type lla fibers have done all they can. If you decide to pick up the weight at a moderate-to-fast speed—somewhere between controlled and explosive—you’ll start recruiting Type I/lla hybrid fibers. These fibers act as a bridge between pure endurance and pure power.

Type l/lla hybrid fibers give you a balance of strength and fatigue resistance. They’re not as slow as Type I fibers, but they’re also not as powerful as Type IIa. In sprinting, this means they help maintain speed when explosive fibers start fatiguing. This will allow for a smoother transition between endurance and power output. The following graph demonstrates how Type l/lla hybrid fibers can be extremely beneficial compared to just Type l fibers. The additional power contribution and endurance is key to its significance.

Training Muscle Fibers in Distance Workouts

Developing muscle fibers is similar to training any other muscle group. Each fiber contains myosin heads that break down during exercise, triggering hypertrophy and stimulating protein synthesis, which ultimately leads to structural adaptations within the muscle (The Movement System, 2020).

As a sprinter, incorporating the right balance of workouts is crucial for developing Type I/lla hybrid fibers. These fibers thrive under a combination of fartlek runs and extensive tempo workouts. However, the key to maximizing their growth, and succeeding in those workouts, lies in the aerobic foundation built through properly structured distance workouts.

So, there you have it. The first of three extremely important reasons to do your best in distance workouts. You can be at ease knowing that those distance days will prove to be excellent in improving your muscle fiber adaptation distribution for sprinting. Keep in mind that you should definitely still be developing your Type lla and Type llx muscle fibers through other sprinting workouts and lifts. The message you should learn today would be to trust your coach. As an athlete, your job is to stand on the line ready to give your all—no matter the time, place, or reason.

Works Cited

The Movement System. “Muscle Fiber Types Explained: Type 1, Type 2a, Type 2x | Muscle Physiology and Training Adaptations.” YouTube, 7 July 2020, URL. 

Plotkin DL, Roberts MD, Haun CT, Schoenfeld BJ. Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives. Sports (Basel). 2021 Sep 10;9(9):127. doi: 10.3390/sports9090127. PMID: 34564332; PMCID: PMC8473039.