Muscle Contractility – fatigue resistance

Muscle Contractility

Part 4 – Fatigue Resistance

 

So far in this series we have discussed muscle contraction speed and muscular strength.  Now we move on to the third characteristic of muscle contractility – resistance to fatigue.  Put succinctly, the more resistant your muscles are to fatigue the better you will perform.  This obviously brings up the question of how to best train your muscles to be more fatigue resistance.  Let’s take a look at this in more detail.

Muscular resistance to fatigue plays a very important role in distance running.  The more resistant to fatigue your muscles are, the better you will perform.  An increased resistance to fatigue results in being able to produce a higher power output for a set distance (i.e. running faster for any particular distance) or producing the same power output for a longer period of time (i.e. maintaining a particular pace for a longer distance).  Either way, your performance improves.

Muscular resistance to fatigue is an inborn characteristic heavily influenced by your particular genetics.  However, the good news is that no matter what your genetics, resistance to fatigue is the most trainable of factors for most people.

Some muscle fiber types are more fatigue resistant than others.  For example, slow twitch fibers are known to be more resistant to fatigue than fast twitch fibers.  However, the situation is more complicated than just leaving it at slow twitch vs. fast twitch fibers.  Like all human characteristics, the pattern of distribution of fatigue resistant muscle fibers follows a normal curve (i.e. standard distribution).  Some individuals are simply born with fibers that possess either a greater than or less than normal resistance to fatigue.  The range of capabilities can be quite dramatic.

A strength study illustrates my point very well.  In this study, 87 men and women performed as many repetitions as possible with 75 percent of their maximum resistance in the chest press.1  While, on average, the subjects performed between 8 and 13 repetitions, the complete range of repetitions performed was between 5 and 24 repetitions.  Two individuals were able to perform a maximum of only 5 repetitions and one subject was able to perform an amazing 24 repetitions.  The other 85 subjects fell between these two extremes.  When plotted on a graph, the normal distribution curve is quite evident.

This study perfectly illustrates the range of fatigue resistance found in humans.  If you are blessed with an above average muscular resistance to fatigue, then you will be able to maintain a set workload for a longer period of time than the average, just like the individual in the study who could perform more than twice as many repetitions as the normal person.  On the other hand, if your fibers are more susceptible to fatigue than the average, you could be like the individuals who fatigued at twice the average rate.

Within a particular type of muscle fiber there is a range of capabilities across any population.  Your slow twitch fibers could be significantly more resistant to fatigue than my slow twitch fibers.  Or you might posses fast twitch fibers that are as resistant to fatigue as my slow twitch fibers.

This would help explain the performance of elite runners.  Elite runners may posses fast twitch fibers that are as resistant to fatigue as average runners slow twitch fibers.  As an example, physiologists have identified a fast twitch fiber, termed Type IIa, that has the strength and speed of a fast twitch fiber but is nearly as fatigue resistant as slow twitch fibers.

Conversely, elite runners may also have slow twitch fibers that are much more resistant to fatigue than the average runner.  A real world example of this phenomenon could be found by comparing Daniel Komen to Sebastian Coe.  Daniel Komen, a world class 3,000 and 5,000 meter distance runner, has a best 1 mile time that is about 1 sec. faster than that of former 800 meter world record holder Sebastian Coe.  However, at 5,000 meters Komen’s best performance is 83 seconds (or 10%) faster than Coe’s.2  This would indicate that Komen’s muscle fibers contract at nearly the same rate as those of Coe, but posses superior resistance to fatigue.  It could also offer a possible explanation for why Coe was not able to attain elite status at longer distance races.

Even though muscle fiber resistance to fatigue is mostly determined by genetics, the news is not all bad.  Muscle fibers’ ability to resist fatigue does improve with training.  The magnitude of improvement will mostly be governed by genetics, but improvement is entirely possible.  My personal bias is that fatigue resistance is the most easily improved and experiences the greatest magnitude of improvement of the 3 factors.

How do you improve muscular resistance to fatigue?  As simple as it may sound, you improve it the same way you improve any other physical factor; you overload it.  Running increasing distances, especially at faster paces, provides a potent stimulus to the muscle.  The muscle responds by increasing its ability to resist fatigue.  I won’t go into detail about all the different chemical and biological changes that occur in the muscle increasing its ability to resist fatigue, just know that these changes are taking place.

Have you ever noticed that most marathon training programs have a regularly scheduled and increasing distance long run as the core workout?  Typically the runner is instructed to gradually increase the distance of their longest run until they peak at a maximum distance of 20 miles or so.  The most common reason for instructing the runner to train up to these distances is to “build the aerobic system” and train the body to run the necessary distance.  What is really happening during the long run is that the muscle is adapting to an increasing load and is improving its ability to resist fatigue.  While your aerobic capacity may or may not improve as you run longer distances for sure your muscles are adapting by getting more powerful and resistant to fatigue.  The faster you run your long runs the greater the training effect on the muscle.

Long runs and power runs are the best way to train your muscles to resist fatigue.  Obviously, if you are training for a marathon your long runs will be considerably longer than if you are training for a 10k and balancing the distance of your long and power runs with your ability to recover from those runs becomes increasingly important.  The important thing is to understand the principle and apply it to your own personal situation.

References: 

1.  Westcott, W (1993). Nautilus 2 (3): 6 – 7.

2.  Noakes, T (2001). The Lore of Running, 64 – 65.


Comments

Muscle Contractility – fatigue resistance — 1 Comment

  1. Pingback: Muscle Contractility – part 4 | Training Science

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>