Athlete Education: Endurance training for your fiber type, Part 1

There are two general categories of fiber types: slow-twitch (ST, Type I) and fast-twitch (FT, Type II). Don’t let slow-twitch fool you, it doesn’t mean they’re slow! Fiber type has to do with how energy is produced, what substrate (fuel) they prefer, how they recover, what type of rest & rest intervals they need. You can be a fast twitch, which a lot of people associate with muscularity and, for example, sprinters, but they can still be an endurance athlete. We can also go the other way and have a slow twitch person that is a sprinter (though rare). Muscle fiber types actually span on a continuum from that pure slow-twitch to the pure fast-twitch, and everything in between. The key is finding out what your tendencies are and how to best train for that. My best practical example that I came up with was when I was with my run coach: we did a 200 easy then a 200 hard. I did okay on that. But when he let me walk instead of jog, or do standing recovery and then run, that is where I shined. I’ve never really thought of myself as a fast-twitch type, but in terms of recovery, I most definitely am. Is it related to all my medical issues? We don’t know. Time will play out and we’ll find out.

But back to slow twitch and fast-twitch.

You can, with training, shift fiber types toward the others’ characteristics, however your foundational muscle fiber type plays a huge role. Individual characteristics that help identify where you are on the spectrum of fast and slow twitch includes: mitochondrial density, capillary density, oxidative and glycolytic enzyme activity, creatine phosphate stores, and contraction velocity. That was a lot of exercise science in one sentence, I realize.So let’s break it down into something easier to understand. With acute (short term) training we don’t change fiber types, but with chronic training load (8-10+ years), we can shift them. What are you willing to do to get yourself there?

Characteristics of Slow twitch muscle fibers

  • Slow to fatigue
  • Can utilize carbs, fat & protein as fuel
  • Can convert lactic acid back to a usable form of energy
  • Lower intensity, long duration capacity
  • Recruited first for exercise in most cases
  • Greater blood supply (high capillary density)
  • Creates muscle “tone” vs size when used (they do hypertrophy but not to the extent of Fast Twitch)

Characteristics of Fast twitch muscle fibers

  • Fast to fatigue
  • Uses Creatine phosphate and carbs as fuel
  • Produces lactic acid as a by-product (not converted to usable form of energy)
  • Poor blood supply (low capillary density)
  • Short duration, high intensity work
  • Recruited as the need for more work as it is created
  • Significant increase in muscle fiber size
  • Takes 3-5 minutes to completely recover the fuel sources & return to homeostasis

Characteristics of slow-twitch runners.

  • Have a limited use of the anaerobic system for end of race kicks.
  • Can handle faster easy runs for two reasons: 1) better fuel system so they burn fat at higher intensity and 2) they use slow-twitch fibers at higher intensities before having to recruit fast-twitch.
  • Their anaerobic capacity is naturally weak so they need regular injections of faster running to generate some lactic acid.
  • Performances are more consistent.
  • They can maintain Peak shape for longer.
  • They take fewer competitions to reach Peak shape.
  • They are better at jog recovery between workout reps than fast-twitchers because they are less reliant on phosphagen and anaerobic systems.

Fast twitch runners on the other hand…

  • Have a high anaerobic capacity to use a kick at the end of a race, if it is not used to stay on pace. If the athlete delves into an aerobic capacity to stay on pace too much they have no kick.
  • They need easier recovery runs (or skip recovery runs) to make sure they’re fast twitch fibers aren’t recruited.
  • They will burn more glycogen at slower paces then slow-twitch Runners, because the fuel system and fat burning is not as developed. They need lots of anaerobic intervals at faster or moderate speeds to increase the lactic threshold instead of threshold runs. For example: 400s at a 10K pace with very short active rest (walking, keep moving, but not jogging).
  • Active rest to prevent the anaerobic system from recovering and being used.
  • Performance is more irregular.
  • Maintain Peak shape for shorter periods of time.
  • They need more competition to reach peak shape.
  • Needs to be more careful with intensity selection when training aerobically. Much easier to go over the edge and miss your training stimulus.
  • Keep long runs very slow as it is very easy to go out quickly and produce lots of lactic acid.
  • Standing or walking recovery because it allows recovery of anaerobic and creatinine phosphagen systems. They can better handle short intervals than longer.
  • Poor lactic acid management and poor ability to use lactate as fuel.
  • They have to augment their Aerobic System with large amounts of energy from the anaerobic system, thus need to work to decrease the amount of augmentation needed so that we can use more of the anaerobic capacity to kick in at the end.
  • Will use fast-twitch fibers to help do the work at earlier intensities because they have less slow-twitch fibers.

So what does that mean for you as the athlete?

The long run.

A slow switch runner can handle a longer & faster paced run, as well as adding stuff into the runs – strides, surges, hills, etc. as previously mentioned. Fast twitch runners, however, shouldn’t go running for too long or too fast – the slow-twitch fibers will start to get recruited after a prolonged period of time, which is counterproductive. With the more inefficient fuel system, glycogen depletion happens sooner and can negatively impact subsequent training, or you will need to build in more recovery days. The bottom line is too long or too fast of a long run will negatively impact their anaerobic abilities to a large degree, which is what a fast which athlete thrives off of. So if you’re a fast-twitch athlete, do a long run every other week.

That was a lot to digest, eh? I’ll post the rest in the next Athlete Education post

Athlete Education: You feel your heart…beat…

Classical formula heart rate max formula (HRmax) = 220 – your age.

Where did the 220 come from? It is the theoretical maximum that an infant’s heart can beat in one minute, and presumably for every year we lose a beat. This has been used since the beginning of time (not really but you get the gist) but it has been found to be, while an easy calculation, inaccurate especially for those of us over 40. You will find that a lot of the online heart rate calculators still use “220 – your age” instead of a more precise equation.

The American College of Sports Medicine (ACSM, 2010) recommends, when possible, to use the newer equation. As you see, this is a little bit more complicated and requires either a calculator, or a spreadsheet.

HRmax = 206.9 – 0.67 x your age

I like to get as precise as I can since we have an inaccurate tool to begin with, so when I program heart rates for my athletes I use the newer formula. I have it set it up in a spreadsheet, I know my athlete’s age, and away we go! My spreadsheet provides both run and bike numbers.

As I mentioned above, the theory is that you can lose one heartbeat per year, however if you’ve been athletic all your life, or if you genetically have a higher heart rate, or other genetic and lifestyle considerations, this may not apply to you. Henceforth in the new formula our age is not as weighted. Medications, stress, how well you slept, if you just ate, what you ate, when you’re training & caffeine can also influence HR considerably.

The next variable of heart rate is resting heart rate (RHR). This is the lowest that your heart rate can go at any time, otherwise you’d be dead. You get to the lowest point when you are the most relaxed in your deep sleep, some point during the middle of the night. The most accurate way to take this is to wear a heart rate monitor to bed, and then find out what your lowest number was as you slept. The other way to find it: wake up without the alarm and without moving around too much, find your pulse in your wrist or in your neck, and count for a full minute.

What’s the advantage of knowing your RHR? It shows change over time as it relates to fitness, ie, the more fit you are, the lower your RHR. If you get up one morning and find your heart rate is elevated 5 to 10 beats, look at lifestyle factors and influences going on, but it may be that you need to do a recovery session that day, or even take it off. Having the RHR elevated for a few days in a row can be indicative that you are getting over trained, and again something to check in with and see what’s really going on. Use resting heart rate in conjunction with other variables to give you a picture of what’s happening. If you have a good feel of your RHR, it can also be plugged into your HR Zone calculations, but then we’d have a whole new spreadsheet.

So now into your training Zones, and what you should be doing in each of them.

Zone 1: 65 to 74% heart rate max
This zone is used for Recovery, as well as longer aerobic training. Part of your warm-up and stuff in between your quality sets would be in this range. Recovery runs might even be in this range.

Zone 2: 75 to 85% of heart rate max
This stone is your higher end aerobic training, the very top is what we refer to as your sweet spot. The Sweet Spot is a heart rate or Pace even that you can maintain for an extended. Of time without too much effort, it just feels easy. This is the Zone where you develop the physiology to go longer & faster. Yes, it takes a good long while to really build it, to understand it, but once you do – you’re GOLDEN.

Zone 3: 86 to 89% of heart rate max
The dreaded “No Man’s Land” where, typically, people who are not used to working with heart rate end up – it’s too hard for your long runs and too easy for your quality runs. It takes discipline to stay out of this Zone. Obviously you’re going to pass through it on your way to Zone 4, but minimize hanging out unless it is specifically programmed into your training plan.

Zone 4: 90 to 95% of heart rate max
You could sustain this HR for about an hour, and then you’ll have to drop your intensity. This is your “quality” work section, keeping in mind that if the set is under 3 min, HR may not be the best indicator.

Zone 5: 95% & above
This is your max zone – however, you typically aren’t in this zone long enough to get a true HR read – it takes 3 min for your HR to respond & stabilize to effort, and most of the work in this zone… you’re not lasting that long. If you are, we need to re-adjust.

Use these for running, if you are cycling you’re going to be 5% lower – so take whatever number you got for the heart rate from above, and multiply by 0.95 (that spreadsheet is looking pretty good about now, eh?).

Now that you know your training zones, take a look at where you upload your data. What are the training zone numbers that system is using, and what are the formulas? I personally feel you need to know your numbers – memorize them – and go by that vs. what Garmin tells you. Update your Training Peaks or other apps if you are able.

So, the caveat with HR training… It’s a guess. Some people have a naturally lower or higher RHR, so it can influence your zones. Take them with a grain of salt. If you’re training in the middle, you’re probably going to be in the right area. As you gain experience using HR, and it feels too easy, bump your numbers up a few beats. If you’re using a program like Training Peaks, it may actually say you’ve set a new threshold (it does all your tracking over time), and then you have to go make sure it’s really a new threshold. Explore your data. Maybe it is, maybe it isn’t. Maybe HR was high because of temps, in which case, pace would be a better indicator.

Not training with HR yet? That’s ok. It’s the next level for when you are ready to improve. People starting out use time – how long they were out exercising/training, how often. Next is being aware of & controlling the intensity (HR). And yes, there’s more beyond this… when you’re ready: Pace… Power…