Your Easy Days Are Too Hard And Your Hard Days Are Too Easy

  • By Aaron Hersh
  • Published Jul 19, 2013
  • Updated Jul 22, 2013 at 11:47 AM UTC

Why your easy days are too hard, your hard days are too easy, and how to find the perfect balance to maximize your training.

This article was originally published in the May/June 2012 issue of Inside Triathlon magazine.

Neal Henderson has successfully coached a wide variety of athletes, triathletes and cyclists ranging from age groupers to Olympians by sticking to a fundamental training philosophy—one he believes to be the key to endurance performance. Contributing editor Aaron Hersh interviewed Henderson, who is the director of sport science at the Boulder Center for Sports Medicine in Colorado and owner of Apex Coaching, on this philosophy and how it can be used to improve any athlete’s performance. The following is a sampling of their conversation.

The Philosophy

The objective of all training is to achieve the greatest level of adaptation, not to become the most tired. Many times people train to get tired or to burn calories. Go ahead and burn calories if you want to work out and lose weight. That’s all well and good, but if you’re a high-performance athlete, whether your definition of high performance is finishing your first Olympic-distance race or trying to win the Ironman World Championship, the best way to achieve your goal is to have an adaptive response to training, which results in improvement, not to simply do more training. You want to do training that has an effect. There are some consistent themes in the way the most successful athletes train, and that’s really about a polarization of effort—workouts are either extremely easy or extremely hard, with almost no training in the middle, and that’s the crux of my philosophy.

Draw Boundaries

The first step in creating a polarized training plan is evaluating the athlete in some objective way. Some of the standard laboratory-type tests I use often include a lactate profile test, occasionally a VO2max test, and an oxygen utilization test to find the mix of carbohydrates and fats an athlete uses for fuel at various intensities. In some cases, we’ll look into less commonly measured things, such as anaerobic power. The lab testing is typically done at the very beginning of the season, or when I start working with the athlete, and then three or four months later, to assess change.

The next part after gathering an athlete’s physiological capabilities is to look at field responses. We perform tests similar to the lab protocols, but we’re out cycling or running on the road. For example, it’s typical that we would do a lactate profile and VO2max test both on the bicycle and in the lab, and then just the lactate profile test while running. We see clear differences in the threshold and heart rates between the two sports, so we conduct tests for both. To conduct these tests outside the lab, we need to have some objective measure of power on the bicycle, usually a power meter, and we use pace or speed while running. Within several days of doing the objective lab measurements, I would have people do what we call power profiling, where we look at maximum power for five seconds, five minutes and 20 minutes. This testing procedure is espoused by Andrew Coggan, [Ph.D.,] author of Training & Racing with a Power Meter. Typically a five-minute power test is analogous to VO2max. The 20-minute maximal effort is analogous to the lactate threshold power determined by the laboratory testing. One difference that I have in testing procedure compared to Dr. Coggan is to have the athlete complete all testing in just one session, instead of over multiple days.

From those field tests we get some comparisons for things like an athlete’s preferred cadence on the bike. When we do the lactate profile test in a lab, everyone holds a more consistent 80 to 100 RPM, whereas when they’re out in the field they’re going to push whatever RPM, and we’re going to get an idea of what they like to use. When running, we get a look at their perceived effort, their speed, heart rate and their pace. Lot of times we’ll even do some video taping to get a look at the mechanics of how they’re moving, as well.

In most cases, there’s not going to be a dramatic difference between an athlete’s performance inside and outside the lab, but when there is, that always raises a little red flag for me. In some cases, people actually underperform in the field relative to what they’re doing in the lab. When that happens, I’m going to look at their cadence and their pacing. That’s often a lesson for the athlete. Field-testing might be something, depending on where an athlete needs to make improvements, that we do more frequently, every four to eight weeks.

We use the data from the lab and field tests to establish the athlete’s training zones. The zones used by different training systems, whether it’s Joe Friel’s Training Bible, Carmichael Training Systems or what we set up at the Boulder Center for Sports Medicine, the zones are not typically dramatically different. Where we might find some differences is in the amount of prescribed training at these different levels. I prescribe extremely hard training and extremely easy training, because it is at those extremes when the body is going to be stressed. And that’s when we are going to have the adaptations and the improvements. And ultimately, that’s what I am looking for: I want to see change. I want to see the athlete improve. I don’t want to see an athlete just be tired, or just be fit—I want them to be high performing.

The Foundation of Endurance Performance

Two-thirds to three-fourths of all training performed by the athletes who I work with is done at a fairly easy effort—what I call steady-state aerobic base pace. Aerobic base and active recovery, or Zone 1 and Zone 2 training (see chart on page 68), are going to make up the lion’s share of training, whereas most athletes spend too much time in Zone 2 and 3, thinking it is easy enough. Aerobic base workouts need to be performed at a low enough intensity that the athlete can recover from their high-intensity training and build a very large training volume base. The adaptations that we get from the low-intensity training, the steady-state aerobic base training or whatever you like to call it, are an increase in economy and efficiency. We have more fat utilized as fuel at any intensity level. Within the body you have two different fuels that are primarily used during endurance exercise: carbohydrates and fat. Protein is only used for energy production to a very small extent. At lower-intensity exercise you’re going to have a more even mix of carbohydrate and fat used. As you work harder, there is a progressive shift to using more and more carbohydrates. Once an individual is near their threshold effort, the intensity they can do for one hour, they are using almost exclusively carbohydrate fuel. Carbohydrate can only be stored in limited quantities in the body—in muscle glycogen, liver glycogen and blood glucose. We also have a limited capacity to take in and process carbohydrate while we are exercising, and as intensity increases, the body can process less and less carbohydrate. When you run out of that precious carbohydrate fuel, intensity will drop. Fat calories stored within the body, even in a very fit individual, are essentially unlimited, so training the body to metabolize fat is critical to endurance performance because it spares precious glycogen stores needed to go fast.

When we train at low intensities, we develop an increased ability to oxidize (metabolize) more fat at any given intensity. So, let’s just say that at a seven-minute-per-mile pace an athlete with poor aerobic efficiency in terms of utilizing fat may derive 50 percent of all his calories from carbohydrates and 50 percent from fat. With more aerobic base intensity training we could see that ratio shift over maybe a two- to three- to four-month period, so he’s burning 60 to 70 percent of those calories for that same running pace from fat and only 30 to 40 percent from carbohydrates.

An individual who has more aerobic efficiency—the ability to spare glycogen and use more fat as a fuel at any given intensity—is going to be at an advantage versus somebody who uses more carbohydrate and has to ingest more and then has to regulate intensity to digest those carbohydrates. Low-intensity training allows athletes to eventually exercise at a higher intensity at the end of a long training session or a race because they spare glycogen.

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Aaron Hersh

Aaron Hersh

Aaron Hersh is the Senior Tech Editor of Triathlete magazine. To submit a question, write Aaron at

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