How exactly do speed intervals make you faster?
First, let’s take a look at the physiology behind things. During speed workouts, you maximally activate your slow-twitch muscles and intermediate muscle fibers. This in turn increases your aerobic capacity.
Speed workouts also increase your production of myoglobin, myoglobin is an iron- and oxygen-binding protein found in muscle tissues. Myoglobin transports oxygen to the mitochondria (membrane-bound cell organelles that generate most of the chemical energy needed to power the cell's biochemical reactions) in your muscles, which in turn produce ATP to give your muscles energy. As you increase your myoglobin levels, you improve your body’s ability to quickly transport oxygen to your muscles for energy…making you able to run faster. High-intensity running is the best way to develop myoglobin.
While genetics play a major role in just how fast you can become, you will still see benefits from performing speedwork. Your body will become more efficient at recruiting your fast-twitch muscles. Fast twitch muscle fibers disappear 1% each year. So, it is important to do speedwork and strength training.
Your running economy will improve so that you expend less energy while running faster and your stride will be more powerful. Runners with strong legs and a good technique are able to propel themselves forward and have a longer stride. This also mean less injuries. When you run fast, you have a wider range of motion. This will improve flexibility, use more muscles, and better form means less injuries.
You will improve fat burning. 100% of fat is burned during a speed session compared to just 50% fat during a long-distance run. During your session your body will burn off carbs as its main energy source; however, after your session your body will start to burn off fat. This is your body’s natural reaction to resupply your anaerobic system and aid in recovery. * On the flip side, you’ll likely to pick up a few muscle strains when you start your journey to becoming a stronger/faster runner. It happens to everyone so don’t be disheartened - trust the process.
So simply put, if you want to run faster, you have to practice running faster! Speed workouts train you how to output more effort, maintain a higher cadence, and mentally cope with physical discomfort while running. If you practice this skill once per week consistently, you won’t just become faster -you will run faster with less effort.
Now let’s debunk one thought many of you have: You need to be fast to do speed work.
There is no pace requirement to do speed workouts. Every level runner can receive benefits from doing speed work. Even if running faster is not one of your goals, speed workouts should still be part of your routine to get a well-rounded training program.
Your paces for speed workouts are relative to your current fitness. Your body knows effort and that is purely what you go by! Speed work is performed at an effort that is hard (think an 8-9 out of 10). It doesn’t matter if hard is a 5-minute mile for you or a 10-minute mile for you.
Summary
Implementing speed workouts into your running routine will improve your stride, speed, and endurance. Together, these will enable you to run faster with less effort during your daily training runs. Becoming a more efficient runner will also help you get fewer injuries.
Additionally, a race day strategy can be planned once you gain the experience from these fast-paced training sessions. Your body will learn to tolerate the physical and mental discomforts while racing.