Muscle Activity During Sprints. Get Strong and Big Legs!

Hi! I am the author and founder of Old School Calisthenics

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Sprints are fundamental exercises utilized by all professional athletes because they improve conditioning, motor skills, stimulate fat loss and hypertrophy. You can use them for many purposes. In fact, sprints are firstly strength exercises that develop explosive power, leg and core strength, muscle size and definition, and cardiovascular endurance.

Sprints Biomechanics

Muscles transfer force to bones through tendons. They move our bones and associated body parts by pulling on them. The process is termed muscle contraction.

The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonistWhen sprinting, hamstrings and quads co-contract.

Antagonist and agonist muscles often occur in pairs, called antagonistic pairs. 

You’ll understand more about how muscles activate and work during different stances of a sprint by watching the figure below. The general conclusion is that sprints effectively train the calves, quads, hamstring, glutes and abs.

Muscle Activation During Sprints
Image Source: Research Gate

Why Are Sprints Effective to Build Strength and Size?

You don’t need confirmation of why sprints are efficient in leg development if you look at professional sprinters and their overall fitness level. They obviously train many more exercises, but getting better with sprints is for sure their first objective.

We can assume that sprints help develop performant, strong and robust legs, glutes and a small waist.

Sprints are compound power moves. They utilize a lot of energy, and it’s the reason why they burn so many calories and why they cause sugar cravings. Once you incorporate sprint sessions, one little suggestion: increase your complex carbs intake rich in fibers.

There is a great activity in the leg and core muscles when running at full speed. The muscle with the longest duration of activity during sprinting is the HAMSTRINGS, even though the quads work very intensively. Studies also show increased muscle activity with increases in speed and distance: Muscle Activity When Sprinting, according to scientists.

Long endurance sprints, such as the 400 meter, were performed in some studies to consider the effects of fatigue. These studies observed that *EMG activity increased as the sprint progressed. Increased contact times in the latter half of the run could be as a result of the increasing number of slow-twitch fibers involved as the fast-twitch fibers fatigued.

*Electromyography (EMG) is an electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles.

How to Sprint and Run Long Distances Correctly?

Running a long distance at a cardio pace requires a totally different running technique than sprinting short distances at full speed. The vast majority take things for granted and believe running it’s easy and comes naturally. In reality, very few (except for the pros) know how to run with a proper form and pace. It takes a lot of time and incremental adjustments until you master the perfect running technique. Check the video below about the leg movement:

A tip for beginners: run without headphones. I know you may need music for extra motivation or to hold on to a fast pace, but in your quest to learn the proper running technique, you should focus on that and your breathing until you comprehend it.

Sprints Can Seriously Injure You!

We consume a great amount of energy and resources when sprinting, which we have to replace. Thus, you need sustainable nutrition. I have the right nutrition eBook designed for athletes particularly: Nutrition Secrets and Intermittent Fasting eBook.

When sprinting, we place our body and mind in a state of alert, and it’s why the organism utilizes so many resources. In a way, we are not meant to sprint too often, even though we can run at a steady pace for very long. For the organism, sprints are more like a defense mechanism to get out of a risky situation.

Everything About Sprints

Of course, I do not have evidence to support all these other than my own common sense and experience. However, I do know that sleep deprivation and regular sprint sessions do not go along very well. You could get injured badly because the body can’t support the effort and intensity due to lack of sleep.

It’s very simple if you listen to your body. For instance, I know my energy level, and if it’s low that day, I won’t sprint at all, even though I am used to high-intensity sprint workouts. I wait until I feel fully rested and energized.

The Best Sprints Workout for Muscle and Strength Gain, Plus Fat Loss

I always begin with at least 15 minutes jogging at an aerobic pace or until I feel very well warmed up. Sometimes, depending on the temperature, I might need 30 minutes to get myself ready for a high-intensity sprint training session. Anyways, the thing is that a proper warm-up is necessary. Then:

  1. 2-3 Sprints x 400 meters (a full track length)
  2. 2 Sprints x 200 meters
  3. 4 Sprints x 100 meters
  4. 10 Sprints x 20-50 meters
  5. 100 Squats, in any way you want!

The rest time is relative to your own capacity to recover. Do not cool down the muscles; that’s what matters the most. Wait a little for the heart and breathing to calm down.

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