Dear Runners,

For this note I wanted to spend some time talking about the tools of speedwork and also the changes that speedwork introduces to our bodies. 

Physiological Purpose

Speedwork has one purpose and that is to make us faster runners.  It is often said that to run fast you have to run fast.  There is a lot of truth to that statement but the real key is to understand what is going on inside of our bodies that makes speedwork effective.  After all, we have to be changing something to actually change something. 

If you remember back to last week’s note on energy systems we talked about the aerobic (with oxygen) energy system and the anaerobic (without oxygen) energy system. To expand on that conversation I would also like to talk for a bit about muscle fiber types.  Basically there are two main types of muscle fibers: slow twitch (type 1) and fast twitch (type 2).  There are a lot of differences between these two fiber types. 

Type 1 (slow twitch) muscle fibers produce ATP (remember ATP – the fuel) aerobically, they are slow to fatigue, have lots of myoglobin, and have high mitochondria and capillary density.  These fibers are activated for basically every activity. 

Type 2 (fast twitch) muscle fibers are more complex than the Type 1 counterparts.  First of all, there are actually two different types of Type 2 muscle fibers and that is a very important point.  The Type 2x muscle fibers are pretty much the opposites of Type 1 fibers.  They have low myoglobin, low mitochondria and capillary density and generate ATP glycolytically.  They contract very fast and are also fast to fatigue.  These guys are used for power sports like sprinting, weight lifting and also in some common areas like a high velocity golf swing. 

Now, here’s where Type 2 fibers become really goofy.  There is also another form of Type 2 fibers called Type 2a.  These puppies are also known as convertible fibers and that is the really cool part.  Because they are convertible they can be converted from their Type 2 status to begin to act more like Type 1 fibers.  These guys have lots of myoglobin, mitochondria and capillary density.  They can also generate ATP aerobically OR glycolytically.  They have a fast contraction velocity and are slow to fatigue…although they are faster to fatigue than a Type 1 fiber.  These are activated for high intensity workouts or when Type 1 fibers are fatigued.   And when would Type 1 fibers become fatigued???  Hmmm…how about during a race…

It used to be thought that everyone was born with a fixed ratio of type 1 and 2 fibers and while this ratio varied from person to person, it could not be changed within a single person.  However, we now know that Type 2a fibers can be converted to act more like Type 1.  This means that we can have extra muscle fibers kick in when our Type 1 fibers become tired. 

So…the next question becomes…how do we get these Type 2a fibers converted?  Through speedwork!  By training (and pushing) our bodies in the anaerobic state then we are recruiting more of these Type 2a fibers. 

So the key to speedwork is that we need to push ourselves to a level of discomfort (not pain) so that we can experience anaerobic running to help recruit these Type 2a muscle fibers.  When we move to the point of 60%, 70% or 80% of VO2 max (this number varies significantly by runner) or 80% to 90% of max heart rate we are forcing our muscles to work at a rate where we can no longer supply enough oxygen to the muscles to do all of the work aerobically.  Therefore, our muscles go partially into an anaerobic state of training.  Or the anaerobic fibers are called into action. 

This anaerobic training also creates a lot of lactate as a byproduct.  We talked about this in the energy system note too.  Depending on the amount of mytochondria the lactate could either be used directly by the muscles or it has to be shuttled back to the liver to be converted ultimately to glucose where it can be used again. 

So in the end we are trying to train our bodies to 1) convert the Type 2a muscle fibers and 2) to work more efficiently so our bodies can deal with the lactate produced. 

Now that you know about the physiology…let’s talk about the training!

Speedwork Basics

There are so many different types of speedwork that I am not going to try to cover all of them.  However the fundamentals are similar for all so let’s stick with the basics. 

Four basic forms of speedwork include the following:

  • Fartleks (Swedish word that means speed play) For this run you just pick a spot in the distance (e.g. a stop sign) , accelerate your running until you hit that spot then slow down until you feel recovered.  This process repeats as many times as you like.
  • Intervals/Repeats – these two workouts are very similar.  With each one you have a period of speed (say 300 meters) and a period or recovery (say 100 meters).  These sessions are repeated a fixed number of times.
  • Tempo Runs – a tempo run is basically a bookended run (slow-fast-slow).  The first mile or two is slow then the mile(s) in between are faster, then the last mile or two is slow again. 

The difference between al l of these workouts focuses on the formality of their structure and also the amount of time you spend either going fast or resting.  In all speedwork there are 5 factors that you are trying to balance. 

  1. Distance – this is the distance (or time) you spending running fast.  This will vary based on the type of race you are training for and the workout you are doing.  Repeats for a marathon may be a mile long and tempo runs can be several miles.  However for a 5k the distance may be only 100 or 200 yards. 
  2. Interval – this is the time spent recovering or resting after a distance.  So you may run 400 meters quickly and then spend 2 minutes or 200 yards jogging to bring your heart rate back down.  The key here is that you are trying to bring your heart rate back to the point of doing a slower run. 
  3. Repetitions – this is simply the number of times you run your distance. 
  4. Pace – the definition here is self explanatory but the question becomes how fast should we go?  This answer will vary by the race distance you are preparing for.  However, you want these runs to be “comfortably hard” or a pace you could hold for 1 hour.  This typically means you should run a tempo run at your 10K race pace or slightly slower than your 5K pace.  If you are training for a marathon, this may be your race pace.  You want your pace to be sufficient to push your body to an anaerobic state (80% to 90% max heart rate – as an example).  This should also be a pace that you could run for one hour without slowing.   You would be tired, but you could do it.  Also, you will not be able to pass the talkability test at this pace.  Remember, you are surpassing your body’s ability to pull in enough oxygen to be fully aerobic.  As such, you won’t have extra oxygen for a conversation.  Also, you want to hold the same pace for the entire period and all reps. You don’t want to start fast and get slower. 
  5. Rest – this describes what you actually do during your interval to bring the heart rate down.   Typically we will go to a slow (or slower) run or jog.  Some people will fully stop and sit down which is common in repeats.  In a tempo run the rest portion is the slower miles at the beginning and the end.  Remember, rest doesn’t usually mean stop.  It just means to go slower than you are running during your distance portion so you go back to aerobic training. 

Injury Prevention

If you have run more than about 10 steps with me you know my philosophies on running injury free.  You have also heard me say that the two hardest things on the body are speedwork and long distances.  The bottom line is that speedwork is hard on the body and you need to run smart to prevent injuries.  Here are some guidelines for running injury free. 

  • You are not trying to run yourself into the ground.  Run speedwork at a pace that pushes you and a distance that gets progressively longer.  However, at the end of a workout, you should feel worked and pushed but not worn out.  It is often said that you should actually feel refreshed after speedwork.  I also like the phrase “a good kind of tired”.  If you feel run down or beaten up, you either went too fast or too long or both.  That is a wasted workout because the tearing down of your body is worse than the improvement from the training. 
  • Discomfort is normal but pain is bad.  Speedwork will push your body into an uncomfortable area.  Your muscles may have a burning sensation and may be sore when you are done.  However, if you feel pain (not soreness) then you went too far.  Take a few days off to recover.
  • Speedwork should only be done 1 time per week and the total mileage should be less than 10% of your weekly total. 
  • Stretch, stretch, stretch.  After speedwork and in the days following it is a good idea to stretch the muscles and roll them out with a massage tool. 
  • Warm up and cool down periods are important.  In cooler weather it is best to get a full mile or two going to get the muscles fully warmed but before attempting speedwork.  Then after the workout it is best to take a full mile at your long run pace to clear the waste product from your muscles. 

YouTube Video

This is a video that I just found recently.  My favorite line from this one is “I believe no decision should be made while running uphill”.  Classic!

Run well…


Shawn Herbig is an RRCA Certified Running Coach.  In his day job he owns a market research and data analytics firm called IQS Research. 

© 2013 Shawn Herbig