My letsrun.com response to the article: more information

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My letsrun.com response to the article: more information

Post by Tinman » Tue Feb 16, 2016 8:07 am

From the article: “In humans, there are two types of muscle fibers, Type I (slow-twitch) and Type II (fast-twitch). Type II fibers can be subdivided into two categories: Type IIa (aka intermediate or fast-twitch oxidative) and Type IIb (fast-twitch glycolytic). Type I fibers use oxygen to produce energy and take a long time to fatigue. Type IIb fibers do not use oxygen, relying solely on glycogen to produce energy. These muscle fibers contract faster and more powerfully than Type I fibers but fatigue quickly”.

My Response:

Due to the challenge of understanding technical elements of conversation during a phone interview with the letsrun.com journalist, Jonathan Gault, portions of the article he wrote and posted on the homepage were a bit off-target. This response attempts to clarify off-target information in the article. Further, this response elucidates the origins of my Critical Velocity training method and how I derived it.

During the interview, I mentioned that type IIb muscle fibers are found only in rodents, not humans. That aside, type IIb, like their human counterpart, type IIIx, fibers are commonly labeled as fast-glycolytic muscle fibers. (I prefer to call them fast-explosive fibers.)

I briefly talked about type IIx fibers: I did not describe a conversion process to type IIa - the fast intermediate fiber group. However, I did say that type IIa muscle fibers are the main target of my training system.

In my opinion, type IIa fibers are critical to a runner' success. These fibers are highly malleable. Using high intensity training, these fibers become proficient at regenerating ATP (the substrate energy used in muscle contraction) without oxygen via the "anaerobic" or non-oxidative metabolic pathway. Using moderately intense training, these fibers become proficient at processing available oxygen inside muscle mitochondria, the organelles inside of muscle fibers (cells) that use oxygen to generate ATP (energy for work).

On page 153 of Exercise Physiology: Theory and Application to Fitness and Performance, Sixth Edition textbook, Dr. Scott K. Power and Dr. Edward T. Howley state that type IIa (intermediate) muscle fibers, or fast-oxidative glycolytic fibers, “…contain biochemical and fatigue characteristics that are between type IIx and type I fibers. Therefore, conceptually, type IIa fibers can be viewed as a mixture of both type I and type Ix fiber characteristics. However, note, that type IIa fibers are extremely adaptable. That is, with endurance training, they can increase their oxidative capacity to levels equal with type I.”

My training system targets type IIa muscle fibers. Specifically, based on both experience and empirical data, I believe that 90% of V.O2 max is the best intensity for meeting that goal. In 1989-90, as a volunteer coach and graduate assistant at the University of Wisconsin- La Crosse, I created my CV concept and workouts for my athletes. I combined feedback from runners who were completing workouts that I assigned, lab data, and studies on lactate dynamics. Further, I included what I learned while training for summer road races. I learned that when I trained at a pace a few seconds per mile faster than my 10k intensity (I ran about 34-35:00 at that time), my race times improved steadily, week after week. When I ran intervals at 5k pace or faster, however, I seemed to improve only 3-4 weeks before struggling or tanking in races.

When I assigned threshold workouts, athletes tended to run too fast - by 8-12 seconds per mile. Rather than telling them to slow down, I asked them how they felt. They said, "Great!" Conversely, when they actually ran at threshold pace, they often said it felt too slow or uncomfortable. And, during the days that followed such workouts, they recovered fast, as long as they ran 12 or more seconds per mile slower than 5k pace. If they approached 5k pace or faster, their ability to recover was lengthened substantially. And, like my experience with the time-course of performance enhancement, they tended to improve in races for just three or four weeks when they ran 5k pace or faster in significant volume during workouts.

I learned quickly that athletes improved a lot, felt good, and seemed to have a lot of enthusiasm for training at 5k pace plus 12 to 16, maybe 20 seconds per mile, with approximately 16 seconds per mile the most typical best sensation, as reported by them. Later I created math formulas to equalize the intensity across a spectrum of runners: i.e. the relative time was adjusted to each runner's reference race performance level.

During that same time-frame of coaching, I tested runners for V.O2 max (maximum oxygen consumption) and lactate production in the Human Performance Lab at the University. I noticed that the average lactate for our team's runners at the end of a V.O2 test, taken three to five minutes post-exercise, was ~11 mmol. During the test, athletes were asked to point to a number of the Borg (perceived exertion) Scale, positioned in front of the treadmill. Typically they pointed to somewhat hard exertion level approximating 50% of their peak V.O2 lactate level, or ~5.5 mmol. *That was 1.5 mmol above the highly regarded anaerobic/lactate threshold value at the time – as described often in endurance sports magazine articles.

I computed the oxygen cost of the ~5.5 mmol level, and it matched up with ~88-91.5% of V.O2 max. (By the way, I used an American College of Sports Medicine formula to convert oxygen cost to meters per minute, and later time per kilometer and mile.)

By the way, CV originally meant Critical Value, a term that defined statistical significance level. Later, I changed it from Critical Value to Critical Velocity, simply to make it a more clear and practical term. (Yes, I know others have, over the years, used a similar CV term in the literature. I never heard of the term at the time I labeled it as 90% of V.O2 max, however. Yet, just like threshold as a science term, it has many meanings to many people: CV doesn't mean the same thing to everybody.)

I’m often asked how I set up CV pace (90% of V.O2 max). I use several mathematical steps. First, race times are converted to a reference of 7 minutes. Then, I use my formula to convert over-land running velocity in meters per minute to average oxygen cost, then multiply it by 90%. Next, I convert the oxygen cost at 90% of V.O2 max back to meters per minute - and then to pace per kilometer or mile. The performance curve that I created places the equivalent 90% of V.O2 max at just under 33 minutes of racing. Some runners can’t hold 90% that long; others can hold it over 40 minutes after plenty of training that expands their type IIa fibers capacity to process oxygen effectively. In general, I tell the runners I coach to ask themselves a simple question while completing assigned CV workouts: ‘Can I hold this pace for half an hour?” If so, they are close to the correct CV pace.

Regards,
Tom Schwartz
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Re: My letsrun.com response to the article: more information

Post by dilluh » Tue Feb 16, 2016 4:45 pm

Thanks for posting this Tom. The devil is often in the details and those details often get lost in translation.

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Re: My letsrun.com response to the article: more information

Post by Tinman » Tue Feb 16, 2016 4:56 pm

I spent my lunch period redoing part of that post because Jonathan Gault, the journalist who writes for letsrun.com wanted me to clarify some points. I added more details and links to V.O2 max YouTube links. I'll let him read the revision and post it (at least I think he will). I told him that I can't give out my math formulas, since it took me 20 years to refine them; it's intellectual property, as I see it. Regardless, I hope the explanations are good enough to convey the message.

By the way, I'll speak at the Running Summit coaching clinic in Chicago on June 25th and 26th of this year, along with Dr. Joe Vigil, Dr. Jack T. Daniels, and Dr. Ross Tucker (of South Africa). I am contemplating the topics to speak about now. I may speak about CV training for one of the lecturers because there seems to be a big interest in knowing more about it and how to use it to coach others (or train oneself).

The Chicago Running Summit information is not up on the internet yet. It probably will be soon. I know there are a limited number of seats; they go fast.

www.runningsummit.com

Tom Schwartz
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Re: My letsrun.com response to the article: more information

Post by Biff » Tue Feb 16, 2016 9:20 pm

Thanks for the updated information!

I see you say ~30 minute pace for CV pace, but years ago I believe you said it was the pace you could hold for 40-45 minutes. Any reason for the change?

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Re: My letsrun.com response to the article: more information

Post by PeterMichaelson » Wed Feb 17, 2016 11:34 am

Tinman, great post!

I was wondering, say someone starts with 100 IIa fibers/motor units. Say after training with easy runs, tempo runs, and CV intervals for awhile, 70 of them are better at oxidative behavior than before training. Say the oxidative ones are numbered 1 through 70, and the glycolitic ones are numbered 71 through 100.

Now, the athlete runs a 300 all-out and after sufficient rest, runs 2400 all-out. Do the 1 through 70 (oxidative) fibers still have the capacity for glycolysis in that 300? Or do they only do oxidative now that they have been trained for that? In the 2400, do fibers 71 through 100 do a little bit of oxidative behavior? Or do they just do glycolysis? Or are they not even recruited because the intensity (speed) is lower in the 2400 vs. the 300?

Thanks in advance. Feel free to rewrite any of my questions, numbers, or assumptions. I know you only like 1 question at a time and this is actually 5 questions. It's also kind of 1 big question, but answer as much or as little as you would like.

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Re: My letsrun.com response to the article: more information

Post by Tinman » Wed Feb 17, 2016 1:46 pm

As a general rule, start all CV workouts at a pace that you can sustain for 40-45 minutes. As you warm up, move that pace down closer to the true 30-35 minute pace. Fast intermediate fibers are used to run at CV pace, and to warm up them it takes awhile. Always progress workouts slowly for ideal effect and minimization of injuries.
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Re: My letsrun.com response to the article: more information

Post by Tinman » Wed Feb 17, 2016 2:00 pm

Peter, there's not an either/or situation. All Type II fibers (fast intermediate, called "a", and fast explosive, as I call them, or "fast glycolytic) have capacity to regenerate ATP with or without oxygen. It's just that when you focus time on developing aerobic stamina, the ability to process oxygen is enhanced and hence a delay in fatigue is created. By focusing on fast reps, you escalate capacity to regenerate ATP fast, but the cost is great - a lot of fatigue - and an inability run far well. It's fine if you are 400-800m runner to escalate the non-oxidative pathway of regenerating ATP, but lousy if you run races over 3 minutes, in my opinion. Yet, even 800 and 400m runner benefit greatly, in my opinion, from aerobic stamina development - by focusing on Tempo, Threshold, or CV training, besides speed training and buffering workouts, such as fast 300s or 400s.

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Re: My letsrun.com response to the article: more information

Post by dilluh » Wed Feb 17, 2016 2:59 pm

Tinman wrote:As a general rule, start all CV workouts at a pace that you can sustain for 40-45 minutes. As you warm up, move that pace down closer to the true 30-35 minute pace. Fast intermediate fibers are used to run at CV pace, and to warm up them it takes awhile. Always progress workouts slowly for ideal effect and minimization of injuries.
When just starting to get into CV workouts, I have had good results with taking, say, a 5x1000m workout and early in training doing the first 2-3 reps at LT pace and then if things feel good, doing the last 2-3 reps closer to true CV pace. In all honesty, even when very race fit, I will often run at least the first rep at LT pace or a touch faster just to make sure everything's feeling ok for the workout. Progression is the way to go with CV, I think. As Tom said, you are still getting maximal benefit even if the first few reps aren't right at CV pace and with a greatly reduced risk of blowing the workout or injury.

I've also found that my body responds really well (and very quickly) to LT training and I often build up a lot of weeks using progressively higher volume LT workouts before switching over to a relatively short stint of CV training before key races in the 5k-HM range. CV is great but I've found I don't need a ton of it to get sharp for the 10k.

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Re: My letsrun.com response to the article: more information

Post by runchristrong » Thu Feb 18, 2016 2:08 pm

Tom.... I just want to express my appreciation for the accessibility that you have offered all of us over the years through various platforms. After 20 years of coaching athletes on the high school, collegiate and post-collegiate levels, I am most assuredly an "old dog" who still likes to learn "new tricks." I am, and always have been, first and foremost a student of the sport. The recent successes of your athlete, Drew Hunter, and the coverage that you and your philosophies have received, has once again drawn me toward being very intrigued by a "new" (for me) approach to training; most specifically in the application of CV workouts.

I totally understand your decision to refrain from sharing your mathematical formulas for determining CV for an athlete. So, can we assume, then, that the input of a personal recent performance into the running calculator provided on your site (http://www.runningprs.com/calc2/index.php) will provide the correct range for our own CV paced workouts?

Thanks again!

Jason Henley

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Re: My letsrun.com response to the article: more information

Post by Tinman » Thu Feb 18, 2016 3:26 pm

Yes, the fast end of the range is true CV, the slow end is where you start or warm up, deciding if you feel good enough to speed up or not that day.
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Re: My letsrun.com response to the article: more information

Post by runchristrong » Thu Feb 18, 2016 5:50 pm

Ok.... That makes sense but let me ask another question, if you don't mind. Is CV better figured off of a longer distance performance than a shorter one?

For example, I notice that if I put in a time of 5:00 for the 1600 (my best TT last year... yes, oh so close), the calculator gives me equivalent performances of 10:40 for the 3200 and 17:06 for the 5K. The CV range that I get from my 5:00 performance for 1K repeats is 3:28-33. However, if I input the 10:40 or 17:06 equivalent, I get a range of 3:32-36.

Thanks again for your time.

-J

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Re: My letsrun.com response to the article: more information

Post by Tinman » Thu Feb 18, 2016 5:54 pm

Use 3km times to 10km times.
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Re: My letsrun.com response to the article: more information

Post by TexNav » Fri Feb 19, 2016 12:19 pm

Awesome read Tom, thank you for sharing!

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