How to Improve your Cardio: 7 Things You Didn’t Know (Part 3- Muscle Fibers)

This is the third part of a seven part series on how to improve your cardio taken from Coach Chris Hinshaw’s Aerobic Capacity seminar.  You can find the links to the first two parts at the end of this post.

Part Three: The Tale of Two Muscle Fibers


Clearing Lactate


What if I told you it’s possible to PR your 5K, 10K, half marathon, or marathon time (or just improve your cardio in general) by creating an adaptation in the muscles of your arms?  That probably sounds crazy, but it is 100% truth.  

Because lactate spills into the bloodstream when levels get too high in a localized muscle group we can do upper body workouts to improve the efficiency of our legs.  Scroll to the end of this post for 6 examples of workouts that will help you do just that.

The number one way Locomotion Fitness can help endurance athletes is by improving your bodies ability to clear fatigue at a faster rate.  The burning sensation, heaviness, and fatigue you feel in your muscles when running (or cycling, swimming etc.) comes from a build up of a muscular byproduct called lactate (check out the last post in this series for more on lactate).

Luckily for us your bodies ability to clear lactate (or even produce it in the first place) can be improved through training.  In other words, lactate clearance and lactate threshold are both trainable adaptations.

We can teach your muscles to consume lactate as fuel.  Literally taking the thing that was slowing you down and transforming it into an energy source that keeps you going longer.  This is possible because your type I muscle fibers consume lactate for energy!

But what are muscle fibers?


Muscle Fibers


We have 2 skeletal muscle fiber types in our bodies.  They are called Type I, and not so creatively, type II muscle fibers.  Type II muscle fibers can be further broken down into Type IIa and Type IIb.


Type I


Type I fibers are the golden goose for improving your cardio.  They are known as ‘slow twitch’ muscle because they contract more slowly than type II fibers.  They are slower because type I fibers use oxygen as a fuel source, and making energy from oxygen takes a series of reactions known as the Krebs cycle, which takes time.

On the upside their use of oxygen means type I fibers can contract for a LONG time before they fatigue.  Therefore, type I muscle fibers are great at helping athletes run, cycle, or swim for hours.  

Add to this the fact that type I fibers consume lactate as part of the krebs cycle and we’ve got a muscle type that can be trained to improve your cardio dramatically.


Type IIa


These fibers are also known as intermediate fast-twitch fibers.  They can use oxygen to create energy like type I fibers, but they can also create energy without oxygen (anaerobically).  They are almost a hybrid of type I and type II fibers.

Because they too use oxygen, you can also improve your cardio by training these fibers to be more efficient with oxygen and lactate.


Type IIb


IIb muscle fibers use anaerobic metabolism (no oxygen) to create muscle contractions.  They excel at producing fast and powerful bursts of strength and speed. They burn out quickly and aren’t very useful in developing your cardiovascular system so that’s all I will say about them in this series.



 How to Improve Lactate Tolerance and Lactate Clearance


All that physiological mumbo jumbo is great, but how can you apply that to improving your cardio?  We need to teach your type I and type IIa muscle fibers to function better in the presence of lactate and make them more efficient at using that lactate as fuel.

To do this we need to implement two types of workouts into your training regimen.  The first is what’s called a lactate tolerance workout, and the second is known as lactate clearance workout.


Lactate Tolerance


To improve lactate tolerance you need to fill your muscles with lactate and let your body adapt to operating with high levels of lactate present.  Like any other training adaptation this takes time and consistency. But how do we get lactate in your muscles?

To fill your muscles with lactate you need to work at a high intensity for 2-5 minutes and then REST (the first post in this series goes in depth on the importance of rest) for at least 3-5 minutes.  If you do not wait at least 3 minutes your body will switch to the aerobic energy system from the glycolitic energy system (the second post in this series talks all about energy systems), defeating the purpose of this exercise.


Here are two lactate tolerance workouts:


  1. 5 Rounds
  • 20 Seconds fast floor press (light- roughly 45# for men and 25# for women
  • 20 sec static hold at the top of the floor press
  • 20 sec SLOW floor press
  • Rest 3-5 Minutes

Part a. floods the muscles with lactate, part b. engages all slow twitch muscle fibers, and part c. teaches your body how to operate with high levels of lactate.


2.  3 Rounds

  • 5 Tuck Jumps
  • 10 Plate Jumps
  • 20 Sec Max Effort Row
  • 60 seconds of air squats at SLOW pace

This time, parts a. and b. are there to help recruit more muscle fibers, improve the neurological signal sent to your muscles, and begin the flood of lactate.  Part c. ensures the muscle is full of lactate. Part d. teaches your body how to operate with high levels of lactate.



Lactate Clearance


Now that we’ve taught your muscles how to function with high levels of lactate present it’s time to teach those muscles how to clear the lactate out of your system.  

There’s two ways to work on improving lactate clearance.  

The easiest way to improve lactate clearance is to take 5 minutes at the end of any high intensity workout and perform a clearance ‘workout’.  

To tack on a lactate clearance training session to a high intensity workout you simply need to end your workout using active rest as described in part one of this series.  As I said at the start of this post you can do this with any movement and upper or lower body muscle groups.


Here’s 2 examples:

  1. At the end of a High intensity workout perform PVC floor press for 3 minutes at a SLOW AND CONTROLLED pace.
  2. At the end of a High intensity workout perform air squats for 3 minutes at a SLOW AND CONTROLLED pace.

Simply continuing to move slowly once you’ve finished the high intensity portion of your workout will train your type I and type IIa fibers to consume the lactate you created from your high intensity workout.  Simple, but highly effective.



The other way to improve clearance is to perform a specific lactate clearance workout.


Here’s 2 examples:

  1. 5 Rounds
    • 12 Seconds of plate shoulder press (Light and Fast, roughly 45# for men and 25# for women)
    • 48 Seconds of PVC shoulder press (slow and controlled)

2. 5 Rounds

    • 12 seconds of goblet squats (Light and Fast, roughly 45# for men and 25# for women)
    • 48 seconds of air squats (slow and controlled)

All 5 sets should be done with no rest between reps or sets.  Here the 12 seconds of fast work creates the lactate and the 48 seconds of slow controlled movement teaches your type I and type II muscle fibers to clear that lactate out.



The Hard Part is Over


We’ve talked about A LOT of physiology over the past 3 posts.  Luckily that part of the series is over and we can move on to some other, less boring but equally important, part of improving your cardio.


**Part 4 will be released later this week and focuses on what an athlete needs to come to terms with before every training session.  Sign up for our email list below so you catch the next one in your inbox.

Part 1- Rest:

Part 2- Lactate:


Featured Image: “Lab-Grown Muscle” by National Institute of Arthritis and Musculoskeleta is licensed under CC BY-NC-SA 2.0 


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