Muscular Endurance: What is It & How Do We Supercharge It?

What is muscular endurance and why is it important for triathletes to develop muscular endurance?

Here’s the thing: It is one thing to be able to perform for a long period of time at a slow pace or intensity. It is another to perform for a moderately long time at a moderately high pace or intensity. 

Muscular Endurance & Triathlon Race Pace

This is not a slow easy pace, but it is also not an all-out max effort. A moderately fast speed is the pace and intensity where most athletes race endurance events like a triathlon. 

This is the pace and intensity where you need your muscles at peak resistance to fatigue.

You should view your heart and lungs as your body's central system and your muscles as your body's peripheral system. Your central system supplies the oxygen-rich blood your peripheral system needs in order to do the work you are demanding of it. 

Long distance training at an easy effort builds your heart’s capacity to pump more oxygen-rich blood to your working muscles. If this blood is delivered to poorly trained muscles, performance will be low despite having a high aerobic capacity or “big engine”.

Here is where developing muscular endurance comes into play. 

Developing Muscular Endurance & Racing Faster, Longer

As you develop a high level of muscular endurance you train your muscles to resist fatigue and to elevate your lactate threshold.

In fact, by accomplishing this you decrease lactate production(1) at all exercise intensities. 

This in turn allows you to sustain the fastest pace you can tolerate over your chosen distance of racing. 

As opposed to developing aerobic capacity or a “big engine” (which can be developed through cross training and occurs relatively quickly), developing and increasing muscular endurance is very sport-specific.

For example, rowing will not help to develop your muscular endurance to perform well when running a half-marathon and vice versa.

Also, muscular endurance is developed in each sport over time. Often over the course of years. 

Muscular Endurance Training: The Pathway

Focusing on muscular endurance-type workouts should only be developed after you have developed your aerobic capacity.

That is not to say that while you are developing your aerobic capacity you are doing nothing to train your muscular endurance. This simply is not true. There is an overlap and a continuum as you train. 

You are never developing one ability in a silo at the complete expense of another.

In fact, combining all aspects of training abilities appropriately will give you the best chance of reaching your highest sustainable intensity output your body will allow. 

This translates into your highest sustainable pace.

Therefore, in a well-periodized program you will adjust your focus as needed. 

So where do you begin?

Shifting Focus from Volume to Muscular Endurance

Your first mission is to accumulate a number of weeks of training at a high volume using longer-distanced, slower-paced workouts. This is a focus on aerobic capacity, the “big engine.”

Following this phase, you then shift your focus to incorporate workouts that prioritize developing your muscular endurance.

What Muscular Endurance Workouts Look Like

Here is where interval training begins to come into focus. Longer duration intervals that last from 10 to 20 minutes at an effort level of 7 to 8 on a Borg scale of 1-10 (where 1 is the easiest effort and 10 is the hardest effort) will allow you to accumulate an appropriate amount of time to develop muscular endurance and train your muscles to resist fatigue. 

Be sure to incorporate short recoveries between these intervals to get the most out of them. 

As you progress in the sport these efforts may increase to longer steady state intervals of 20 to 40 minutes with continued short recoveries.

The efforts therefore become more “race-like.” 

Multiple Muscular Endurance Workouts A Week

Incorporating these efforts once a week for each sport you perform is an appropriate way to begin developing muscular endurance.

For example, if you are a triathlete, then performing a muscular endurance workout one time per week for the swim, bike, and run is an appropriate beginning dose.

As your body becomes more adapted (and depending on your race expectations) you may even add these types of sessions twice a week into your routine. 

Muscular Endurance: An Antidote To Slowing Down

Remember in endurance sports it is the athlete who slows down the least towards the end of the race and (specific to triathlon towards the end of each discipline) who is the most successful.

Developing your muscular endurance is critical in enabling you to maintain a high pace throughout the entire race and be the athlete who slows down the least.