Saturday, February 28, 2015

For geeks only


As part of my job as a pediatric nurse practitioner in a busy teaching practice, I get the opportunity to attend weekly Grand Rounds. This is a one hour educational lecture, presented by a resident or attending, with a different topic every week. I love to learn and Grand Rounds is always really interesting. This past week, I attended a lecture by Philip Skiba, DO, PhD, MS, who is the director of our Sports Medicine department. The topic was Assessing Sports Performance. Dr Skiba has done a lot of research and lecturing on this topic. He's also coached many elite and olympic level athletes. So for today's blog post, I put on my science nerd hat and share some of the highlights of his talk--this was a topic near and dear to this runner's heart. Besides, it was fascinating.

Nope!
Dr Skiba talked a lot of performance of runners. Since this was a medical lecture, the information was pretty scientific. He used a lot of graphs and mathematical formulas. I even heard the term Krebs cycle tossed around! That was a nightmare blast from my biochemistry days! Who knew that I would need to remember that again? But he also talked a lot about some important concepts behind why we train the way we do. I'm going to try to sum it up here without getting too technical, and to prepare this post, I had to do a lot of background reading. Hopefully, I'm able to simplify it enough that it will all make sense and you can apply some of the concepts to your training! I also thought that his lecture helped me understand why we runners train the way we do, and why the work Becky has me doing, in the form of heavy lifting and interval training, is really having a positive impact on my running.

Dr Skiba introduced the concepts of critical power and VO2max. Critical power is the rate at which you can maintain your pace without exhaustion. Some of us refer to this as endurance. If you are very aerobically fit, you will have a high level of critical power. Critical power is a number that can be determined in a lab. Elite athletes train using knowledge of their critical power. If you run beyond your critical power, you start to become fatigued and your performance starts to suffer.

VO2max, also known as aerobic capacity, is the ability of the body to utilize oxygen. Having high critical power and high VO2max means you you can perform at a high level without exhaustion, without going into an anaerobic state (produce lactic acid), or become fatigued. Athletes who have a high VO2 max can perform at a higher level because their bodies have the ability to produce more energy. This explains why a lot of endurance athletes use the banned substance, epo, because this substance helps increase red blood cells, which carry oxygen in the body. More oxygen means increased aerobic capacity. BTW, the maximum allowable hematocrit for professional cyclists is 49.5%. You and I are probably sitting around 36%.


Lactate threshold is another determinant of performance. Lactic acid is a byproduct of metabolism, and begins to build up when you're working hard. Lactate threshold is the level of exercise at which lactate begins to accumulate in the blood. The more fit you are, the longer you can perform at lactate threshold. Lactate threshold is usually about 80-85% VO2max for fit athletes. Lactate threshold is probably the best predictor of performance. And even though conventional wisdom says accumulating lactate is bad, that isn't true. The body can use lactate for fuel and it does during endurance activities. However, increasing lactic acid levels does lead to fatigue.

Economy also plays a role in performance. Running economy is defined as the volume of oxygen consumed at submaximal speeds. An athlete who has a very efficient stride will be able to outrun another athlete who has a higher VO2max, simply because he is using less energy. Body weight is another factor that affects performance. Increased body weight has a negative effect on your VO2max. Also, the heavier your legs are, the lower your running economy. You will run slower than you would with a lower body weight.

There is only so much a runner can do to improve VO2max and critical power. Most of that is genetically determined. But there is some room to improve both parameters. In fact, newer, less conditioned runners can show much more dramatic improvement in these areas that experienced runners. In addition, some of us have more slow twitch muscle fibers (good for endurance events) and some have more fast twitch muscle fibers (good for sprinters). But because no one has 100% of either type, there is some evidence that training can alter this as well. One thing you can really have an impact on is your lactate threshold, though, and that is the focus of a lot of training plans.

Slow vs fast
I need to mention here that just because a person tires out quickly when trying to run long distances doesn't mean they have mostly fast twitch muscles. Keep in mind the concepts of VO2max and critical power. If you run faster than your VO2max you will fatigue very quickly. This has more to do with conditioning than anything else. I had to put this in here because I've actually had non-runners tell me that they "can't run long distances" because they only have fast twitch muscles, that they are more of a sprinter. Girlfriend, please. Pace yourself.

What does all this scientific information mean for the recreational athlete? What if you don't have access to a lab to measure your critical power or your VO2max? How do you know what your lactate threshold is? Can't I just run with my heart rate monitor and be done with it?

There are a few things you can do to improve your VO2max/aerobic capacity. Think intensity, not training volume. That means that stop the madness with the high mileage training. Studies show that HIIT (high intensity interval training) is better at increasing VO2max than endurance training. Some examples are intervals and speed work. A way to increase your lactate threshold is to train at higher volumes of training with your efforts at higher than resting intensity. Think tempo runs. Strength training has also been shown to increase VO2 max, lactate threshold, and running economy. It doesn't have to be all about high mileage.

BTW, while heart rate training has a place in all of this, it is important to know that heart rate monitors do not predict aerobic capacity. All the heart rate monitor tells us is how hard we are working at that moment in time. But monitoring how fast your heart rate goes down after an activity is a predictor of aerobic fitness. A more fit person will recover more quickly.

I walked away from this lecture both awed and overwhelmed. I had no idea that there was so much science behind running and cycling performance. I reflected on this information a lot over the past couple of days. This is the kind of testing and training that is utilized with elite athletes. That's a lot of pressure. I can see why a lot of elites might be tempted to dabble in banned substances, just to see those numbers improve. We mere mortals focus on mile splits. Imagine having your runs broken down into all those numbers and graphs. Seems to me that it kind of takes the fun out of running, doesn't it?

For more information:
http://m.runnersworld.com/race-training/find-your-tempo?page=single
http://www.athleteinme.com/ArticleView.aspx?id=242 (includes info on measuring VO2max at home)
http://www.sport-fitness-advisor.com/exercise-physiology.html links to great articles
http://www.runnersworld.com/race-training/four-lessons-i-have-learned-physiology
http://running.competitor.com/2014/02/training/how-do-muscle-fibers-determine-speed_67060
http://physfarm.com/new/
http://www.ideafit.com/fitness-library/hiit-vs-continuous-endurance-training-battle-of-the-aerobic-titans
http://www.runnersworld.com/race-training/get-faster-and-stronger-with-high-intensity-and-volume-training

20 comments :

  1. Wow, that is a great lecture. And oh boy, the Kreb's cycle makes me cringe! We talked about a lot of this in the RRCA coaching certification course as well. I have to say, I've really been thinking a log about changing my approach to training after your experience. But I haven't met anyone like your coach. I'm not quite sure how to develop my own plan. I would love to see your training plan sometime to see if something similar would work for me and backing off the miles would make a difference in my time. I've decided to retire from the marathon after MCM in the fall ( I haven't announced that outloud until right now).

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    1. I'm curious why you've made the decision to retire from running marathons. I don't plan on doing many..

      I'd be happy to share my training plan with you. The only thing that won't be on there are the workouts Becky had me do when I went to see her.

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  2. Very interesting, but that makes my head hurt with too much info, LOL. I just like to run, and knowing I'll never be elite or speedy is totally ok in my book.

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    1. Yeah, I was kind of regretting writing the summary as I tried to pour through all the info. But I wanted to put it out there.

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  3. Ground rounds sound like a very interesting part of your job! He would have left my head spinning with all that information! The world revolves around math and science and I feel a little smarter after reading all this, don't know what I am going to do this all of that but it was interesting to read!

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    1. The key to take away from all this is that you don't need to do high mileage to train for distance events. And if you want to run faster, intervals/speed work/tempo runs are really the way to go.

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  4. I use a combo of all of those things, usually. I did train by my heart rate only for Gasparilla and it went beauifully, better than I expected. I'll continue with it for my marathon. If I was running any of these races for a time goal, my approach would be different. For my fall marathon, I'll go back to my usual way of training, which includes tempo, steady state and speed work. Until then, I'm enjoying the more relaxed slow base building. :)

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    1. Seems like your approach worked well for you at Gasparilla!!

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  5. Really interesting stuff! I've tried to teach myself a little bit more about lactate threshold lately. :)

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    1. I didn't know the why behind my training, but this all made sense to me! I'd like to learn more.

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  6. I didn't know you did that for a living. That is a very rewarding career!

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  7. Yep, this is the stuff the RRCA coaching certification weekend is made of. Overthinking on this DOES take some out of the fun of running to me. At the end of the day, there are people who will respond better to high mileage training and those who respond better to intensity. Certainly all plans need to have both. In marathons though, at that 'hitting the wall" point when your glycogen stores run out, your success or failure will depend on how well you trained your slow-stitch muscle fibers.

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    1. Exactly. But not everyone should be doing super high miles. Did you learn how to determine what your clients should be doing? For sure, training plans aren't one size fits all.

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  8. So much science!

    Great post, though. It's nice to have the workings of the body broken out like that. Even if it is way over my head!

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    1. Oh trust me, this post was a challenge for me, and I've got a background in this!

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  9. I love to learn about this. I really want to go to a lab in town and do the VO2 test and see where I am at. I've always felt pretty good about my endurance, but I don't posses much speed. While injured I did 30 burst of speed on elliptical as a way to keep my fitness up and it seemed to work. I would just like to find a way so I could tackle the marathon distcance and feel good at the end.

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    1. When I ran Chicago last year, it was a totally different experience from the first time. I did everything that I wrote about above, with my trainer. My highest mile week wa 38 miles. I felt great at the finish, and never hit the wall.

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  10. I'm very intrigued by the science of running and would love to get my RCAA certification, just for the knowledge not necessarily for coaching. There is so much information and it gets overwhelming. What works for one person does not necessarily work for another, so the magic is finding what works for you. Great post.

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    1. I want to keep learning about this as well. Truly fascinating stuff!

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