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A few weeks ago, I spent the morning with the Stanford Human Performance Lab (HPL) to do some lactic threshold testing and get a benchmark for the early stages of the training year. Although I'm usually not a "train by the numbers" guy, I thought it would be good to figure out if I'm at least in the ballpark with my target heart rate ranges. Exercise Physiologist Phil Cutti was my guide and task master.

Phil first had me lay down on the "Dex" machine (a Lunar iDXA DAX System made by GE Healthcare) which used low level x-rays to get a full body scan of my body fat levels. It took about 10 minutes of sitting still for it to spit out an x-ray image of me with some disturbing numbers. Sixteen percent body fat? That's 4-5% higher than last year at this same stage! It's the nightly ice cream, I know it! Damn, I seriously need to shed some pounds.

Not so fast, said Phil. The Dex is extremely accurate in measuring body fat, including areas that aren't usually measured with a caliper test, such as fat around your intestines and in your muscles. In short, it's not fair to compare the results of the Dex with a caliper test. We then had a good discussion about what is the best target body fat % given my age, target race of 100 miles, the risks of dieting while training, and the potential to turn all this fun training into a five month hunger-driven grumpfest. Phil emphasized that overall fitness should be the goal, not a certain weight target, and I certainly shouldn't push to the point of risking getting sick or I would never make it to the starting line. He also pointed out that my weight - 156 lbs - was only 3-4 lbs higher than my "race weight" from last year. In short, my normal training schedule will probably get me down to 150-152 lbs and it may not be worth stressing to get any lower.

The Dex readout also had a lot of other information, although it wasn't clear how to use it for training purposes. For example, I'm carrying more lean muscle mass and fat on my left side, which might indicate asymmetry in my stride or leg length. My BMI is in the normal range. My android (fat above the waist level) to gynoid (fat below the waist level) ratio was 0.86, indicating less risk of cornary disease. Hmm, good to know, I guess.

From there, Phil led me to the world's most insane treadmill (it goes to 20 mph, just in case Usain Bolt drops by) and explained the process for the lactic threshold test. I would run 6 minute intervals starting at 7mph; normally this is done in 4 minute increments, but since my target race was ultra-distance he thought it best to lengthen the interval. After each interval I would step off the treadmill so he could take a small blood sample from my ear lobe, and then he would increase the speed 0.5mph and I would do it again. While I ran, he would measure the lactic acid content of my blood, as well as ask me what my perceived effort was. We would continue this until I couldn't complete a six minute interval or indicated I was ready to stop.

It began slowly, which gave me a chance to get to know Phil a bit better. For many years he was an elite cyclist until he broke his back in an accident. He has since made a long and amazing recovery, and even completed the North Face 50k last year. His passion for understanding the body's ability to perform and heal were contagious. I didn't even mind that he was making me bleed every few minutes. ;-)


For about 90 minutes, I pounded away on the treadmill until I finally said going beyond a 5 min mile pace would risk me projectile vomiting all over their clean lab. In retrospect, I probably should have eaten breakfast sooner in the day. ;-) After a quick warm down, he sat me down with the results. First he shared an analogy of the body to a machine that helped frame the discussion. It went something like this:

Chassis (what you're dealt with) -> Body shape and size
Engine (ability to process) -> VO2Max and Lactate Threshold
Horsepower (how fast/hard) -> Pace/Power Output
Miles Per Gallon (how long on the same energy) -> Running Economy

So there are many things to consider when training, and this test was specifically focused on the engine. We spoke about how I am currently in an aerobic phase of training, so I haven't been pushing to the red line at all and that should be taken into account.


He showed me the chart, and we talked about how the goal of training is to push the red curve down and to the right by specifically addressing two areas - aerobic training to increase my speed at the same lactic levels, and LT/speed training to improve my overall lactic threshold. The results indicated the following training ranges:

Aerobic - 131 to 151 bpm (roughly 8-9 mph on a treadmill)
Threshold - 151 to 164 bpm (roughly 9-10 mph on a treadmill)

I noticed two things right away. First, my current aerobic training zones (125 to 140 bpm) and pace were too low. After speaking with Phil about how I had gotten those ranges from a VO2 Max test two years ago, he basically said it was likely I was improving both my aerobic capacity and running economy over that time period. But he also emphasized that it's good to have some long runs where I stay on the low end of the aerobic range to help train my body to process fat. Second, my current threshold training zones (162 to 170 bpm) were too high. So basically I needed to go a bit harder in aerobic training, and could go slower on my harder runs and get a similar benefit.

Phil spent 20 minutes with me to explain how these aren't hard and fast rules since there are other benefits of training beyond these ranges. For example, a hard track workout may exceed the threshold heart range, but give tremendous benefit to running economy and turnover (my "miles per gallon"). He also had lots of other little tidbits, and was careful to explain how his recommendations for me are different than what he would tell a 20-year-old on the track team because (a) my ability to adapt and recover are different, and (b) the ultra distance has a very different set of needs than a 5k/10k.

Phil was generous with his time to answer all my questions about training levels, recovery, calorie intake, stride efficiency, and how to adopt these track-based learnings to the ever-changing trail courses. We agreed I would come back again in a few months to get another checkpoint and dial in my target HR and speeds for Western States.

I felt energized to train with all this new knowledge, and the clarity of knowing there are some things I can affect by sticking to a plan. It may be worth the $200 just for the boost of morale! Now back to the trails...

- SD

My parents-in-law gave me a great gift for the holiday season this year - a gift certificate for a full VO2 Max and resting metabolism test. Last week I went to BaySport of Redwood City, CA, where Physical Therapist Brian Tomason put me through two sessions of testing to find out how my body utilized oxygen, fat, and calories. Both sessions used a system by New Leaf which tracked my oxygen and CO2 usage through a mask, and my heart rate. Brian doesn't get many ultrarunners, so he was excited to see what my "abnormally high levels of racing" might yield.

I've never really done much benchmarking of my heart rate (HR) zones prior to this, aside from the standard "220 beats minus your age" kind of thing. 90% of my runs are really for fun, loosely organized around a "long fartlek" or "go until it hurts". But now that Sophie is around, I've felt the need to make my ever-disappearing training time as efficient as possible. I figured a good starting point would be to make sure my training HR zones are correct. I know can hold 158 beats/minute through a 10k and it feels hard, so I figured that was roughly what my anaerobic threshold (AT) was (AT is when you start building lactic acid, and you're burning almost all energy from glycogen instead of fat - read: unsustainable for long periods of time). I do most of my aerobic training between 130 and 145 beats/minute, which feels easy to me, but just enough where I can feel my breathing pick up.

The VO2 Max Test
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The first test was the V02 Max test. For this, they strapped on the mask and an HR monitor, and put me on a treadmill. Over the course of 25 minutes, they slowly cranked up the speed and incline until I maxed out at 12 degrees and 10 miles/hour (and nearly passed out). This calculated the oxygen and CO2 levels at each heart rate. Brian used other systems to find my body fat %, etc. Here are the test results:

MaX HR: 172. I guess that's not bad. It sure felt like the "max"!

VO2 Max: 73.3. The VO2 Max represents your peak oxygen uptake, ie, your ability to deliver oxygen to your muscles. Brian said that anything over 60 is considered "above average shape", and that most people come in around 40. A professional athlete that is tapered would come in around 80-90. Overall, it looks like my body is utilizing oxygen well, but there may be some room to grow.

Calorie Burn in Aerobic Zone: 13.1 kCal/minute from fat. Brian said this is a very high rate for use of fat calories, but he's not surprised given the volume of training and racing. Basically, I've tuned my body to burn fat very efficiently when I'm at an aerobic pace.

Anaerobic Threshold: 125 beats/minute. This is the point where your body starts needing to use glycogen instead of fat to process calories. I was very surprised to see how low this was, particularly given that I have run 50-milers with an average heart rate of 145 beats/minute. If this test was right, I haven't been doing any true aerobic training since my heart rate is too high on my "easy" runs. Close examination of the output chart shows that I am very efficient at burning fat below 110 beats/minute, but it drops off like a cliff between 110 and 140 beats/minute. A better trained athlete would have this holding steady of decreasing gradually to an AT much closer to my Max HR.

The Resting Metabolism Rate Test
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The next morning, I came in for a resting metabolism test to determine what my caloric burn needs are at rest. I had fasted for 12 hours, and they strapped the mask on me again and had me chill out in a dark room for 20 minutes to relax as much as possible. That is, as much as one can with a big tube strapped across your mouth. ;-)

The results of this test were also very interesting:

Resting heart rate: 38 beats/minute. Most of the men in my family have a low heart rate and I'm fairly well conditioned, so I'm not surprised this is low. I know individuals with resting heart rates as low as 32-34 beats/minute.

Resting metabolism caloric burn: 516 calories. This means that I only need 516 calories per day to maintain my body weight, or 744 calories on a typical non-workout day. What?!? That's like two donuts!!! A typical BMI would say that 2200 calories is about right for my age, and a standard chart prediction for a trained athlete would have been closer to 1700 calories. Brian was a bit baffled at the low reading, but then pointed out that nearly all of those calories were consumed from fat and both my oxygen and CO2 levels were shallow. Basically, my body is insanely efficient at rest. Apparently I could fast for a week on the couch and only lose one pound.

Recommendations
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Brian said that I'm basically in really good shape, and that the post-test recommendations are mostly for people trying to get in shape, not crazy endurance people like ultrarunners. But he did say this:

1) My body fat level is just fine. Given my ability to stick to high levels of training, he said I could certainly get down to the 9-10% found in most elite 10k runners (ab cover shoot, anyone?). But when he saw the 100k's and 100-miler on the schedule combined with my fat-burning aerobic capacity, he suggested it would be good to carry an extra couple of pounds for fuel. He also warned that since my resting metabolism is so low, it's hard to lose weight via diet, and the only outlet would be to exercise even more than I already do.

2) I should consider "aerobic intervals" to raise my AT. Brian was a bit perplexed by my low AT calculation (given my race pace at previous 50-milers, which would have had my bonked or dead by mile 30), and warned that the test could have been off. But the quick drop off from aerobic to anaerobic indicates that I could benefit from much slower workouts just under my AT. He suggested going 5 minutes just under AT, resting for 15 seconds, then repeating over an hour.

3) I should do more weight training. Brian congratulated me on being efficient with what I have - by his calculations, my body is very good at using every muscle and every gram of fat. But that means I'm "always at 11", requiring me to recruit all that I have for every race. Weight training could give me more muscle mass, and require me to recruit less muscles for the same amount of work. I certainly have enough headroom in my resting metabolism to feed a few more muscles.

I'm going to take Brian's advice on a few fronts, and do more weight training and at least one weekly aerobic interval. I did one aerobic run this weekend at 120 beats/minute, and it was excrutiatingly slow. But there could be benefit, so I'll stick with it. I don't want to turn my favorite daily activity into too much work, so I'm going to stick with "fun" for most runs.

It certainly is helpful to have some specific numbers associated with calorie burn during exercise, and a more realistic benchmark for my daily intake. I'm burning much more during exercise than I had thought, but am using much less outside of exercise. All of this data will be helpful in charting out a food/race plan for longer runs.

I'm open to feedback if any of you have (a) ever done anything like this, and (b) see anything crazy in my test results or recommendations.

Thanks, SD

PS - Congrats to all the racers who mastered the Woodside 50k this Sat!