McMillan Running System

This post was provide by McMillan Running, a recommend resource for distance runners and coaches. This article is part one in a three part series detailing McMillan’s Six Step Training System.

By Greg McMillan, M.S.



As an exercise physiologist, I believe understanding sports science can help you train smarter and achieve your best performances. As a professional coach and full-time runner, I understand that the scientific jargon can be like, well, scientific jargon. There’s often a “disconnect” between what the physiologists say and what those in the real world of training and racing say (and do!).

In this article (the first of many offered on this website), I present a simple method to make the connection between science and reality and show you how to use this connection to improve your running. This way of looking at sports science gives you an idea of the underlying tenets of my philosophy of training. It would be presumptuous to say that this philosophy is a new, “magical” method. It’s essentially just the simple process I’ve used to make sense of physiology and how it relates to the time-proven methods of great runners and coaches – who are our greatest teachers of how to train and race. The result is as close to a foolproof way to plan your training as I’ve found.


The fundamental connection between the lab and your training/racing is illustrated in Graph 1, below. To fully understand this connection, let’s simulate an exercise test and I’ll describe how the variables measured relate to your training/racing.



If you come to an exercise physiology lab for testing, we’ll have you run on a treadmill. We’ll measure several variables that, as I’ll show, are key indicators of how you should train to achieve optimal results and your fastest performances.

Once on the treadmill, we start you running at your slow, easy run pace. Our instruments measure your heart rate, ventilation/breathing rate, oxygen consumption (VO2) and the level of lactate in your blood. We also record your effort level at each speed. These variables are shown on the Y-axis of Graph 1, above. On the X-axis, your speed is charted, starting slow and gradually getting faster and faster. The X-axis shows race pace, described by time. In other words, one-hour race pace indicates that this pace is what you can race for one hour. You don’t need to worry about what exact pace that is for you since the McMillan Calculator does it for you but I want to list these paces so you have an idea of the effort and how these match with changes in the physiological variables. Matching your real world speeds with various physiological variables is essential for applying the results of the test.

As you see on Graph 1, at your slow, easy pace, your effort is easy, heart rate and oxygen consumption are relatively low and your breathing is barely noticeable. There’s also very little accumulation of lactate in your blood. This pace is what for years has been called “conversational pace”.


Once you’re warmed up a little, we slowly increase the speed of the treadmill to around your two and half hour race pace – marathon pace for some runners, half-marathon pace for others, somewhere in between for most of us. Each of the variables on the graph gradually increases — faster heart rate, ventilation, oxygen consumption, a little more effort and lactate. It’s at this point (around two and half hour race pace) that runners often experience what has been called the “second wind”. It seems that the systems of the body are geared up (muscles pliable with large delivery of blood, energy-delivery systems running efficiently) to the point where the pace seems to get a little easier. Some scientists have called this pace, your Aerobic Threshold.  Again, you don’t need to wonder what your two and a half hour race pace is, the McMillan Calculator calculates that for you.


If we increase the pace to around your one hour and fifteen minute to two hour race pace, things begin to get interesting. Your effort becomes moderately hard but you could handle it for an hour or more. Both your heart rate and VO2 continue to increase at the same linear rate as before. At about this pace, however, you may notice that your breathing takes a noticeable increase – this is called the Ventilatory Threshold. The accumulation of metabolic by-products stimulates exhaling more air (and hence more CO2) to remove these products. We also see that lactate begins to accumulate slightly faster than at slower paces. In fact, if we increase the speed to around your one hour race pace, you see that your lactate curve takes a turn sharply upward. This is your Lactate Threshold, which you’ve probably heard about.  Also present at this pace is what many call the Anaerobic Threshold. (This is differnet than the Aerobic Threshold discussed above.) The idea is that at the this threshold pace you begin to require increasingly more energy through anaerobic energy pathways.


Increasing the speed to 25 minute, then 15 minute race pace, your effort becomes harder and harder. Heart rate and VO2 continue their straight-line increase while your breathing is now labored. Lactate accumulates at a very rapid pace. The thighs become harder to lift. Fatigue sets in.


When we take the pace even faster, reaching 10 then eight minute race pace, things really get interesting. Your effort becomes very hard, and breathing passes from tolerable to maximum capacity. Your heart rate and VO2 reach their maximum and stay there. Lactate is now accumulating very rapidly.


If we finally kick the pace up to your five or four minute race pace (or faster), effort, breathing, heart rate and VO2 are all redlined and lactate floods the muscles and blood. It will only take a short time before you’ve had all your body and mind can take. You’re now bathing in a sea of lactic acid. You give the STOP sign and straddle the treadmill belt until it slows to a walking pace.


While you recover with an easy jog, allowing the fog that is total exhaustion to clear, we now have a clear picture of your physiological status across several speeds. We can link specific effort levels, heart rates, breathing rates, lactate levels and oxygen consumption values with these various running speeds and race paces at various distances. We’ve just made the key connection between the lab and the real world – physiological responses linked with specific race paces. Using this information, we can now prescribe very specifically, the optimal training paces you should use to affect various key aspects of your fitness: endurance, stamina, speed and sprinting.

I’m not suggesting that each runner needs to get a treadmill test performed. On the contrary, I find that Graph 1 is very similar for all high-performance runners so it’s applicable to each runner’s training. In other words, it’s likely that at 30 minute race pace, you and other competitive runners will be operating at approximately the same percentage of max heart rate.

I simply wanted to help you understand the physiological reactions at various race paces so that you don’t have to go to a lab for testing. I want to show that by being able to estimate your equivalent race paces for various race distances (which is what the McMillan Calculator does for you), you can then train very specifically to obtain the desired physiological adaptations.

Effectively, you’ve learned how to link sports science with multi-pace training, the training system that is the foundation of most of the world’s successful training programs.


In the next section of this article, I’ll take the results of this test one step further and show how the various energy systems of the body are linked to specific types of training. You’re then ready to set up your scientifically-based, yet individualized program that gives you the best opportunity for success and removes all guesswork from your running.



In the first section, you saw how different physiological responses occur at different race paces. In general, as you increase your pace: heart rate, effort level, oxygen consumption, ventilation and lactate all increase. Some of these variables increase linearly until reaching a maximum level or plateau (heart rate and oxygen consumption). Other variables exhibit a “threshold” after which they increase at a faster rate than at slower paces (lactate and ventilation).

It’s not as if this is completely new information. After all, you’re a competitive runner and have spent some time experiencing all these reactions. Nevertheless, it’s helpful to see it displayed graphically. Visualizing Graph 1 will carry forward into this and future sections to give you a complete picture of the training process.



In this section, I’ll break Graph 2, above, into four parts. Loosely, these four parts describe the four main categories or zones of training. While many coaches, athletes and sports scientists have different names for each category of training, for simplicity’s sake, I’ve named the sections: Endurance, Stamina, Speed and Sprint. I’ve used these terms before in articles I’ve written.


The first section of Graph 2, on the far left, corresponds to when you’re running at your slow, easy pace. I’ve labeled this as “Endurance”. Science and experience have taught that optimal “Endurance” training occurs when your heart rate is between 60 and 75% of maximum and your oxygen consumption stays between 55-75% of your VO2max. In this zone, your breathing is comfortable and the effort is easy. Your lactate level hangs around 1 to 1.5 millimolar, only slightly above resting levels.

If you follow the paces on the x-axis of Graph 2, you’ll see that the pace range for this zone is rather wide. Appropriate paces can be as fast as your three and a half hour race pace or as slow as your 10 hour race pace, depending on the workout. To see what these paces are for you and your performance level, you’ll just enter your times into the McMillan Calculator. But that’s the next step. For now, let’s discuss these zones in detail.

The goal of Endurance training is simple, to build endurance. To do this, your body adapts in very specific ways. Research has shown that Endurance-zone training results in specific adaptations to your cardiorespiratory and nervous systems as well as to the muscles themselves. The key cardiorespiratory or “central” adaptations that result from Endurance training include an increase in your stroke volume — the amount of blood that is pumped with each heart beat. The result is that fewer heartbeats are needed to deliver the same amount of blood to the working muscles. You experience this as a slower resting pulse and lower heart rates at a given pace.

In the muscles, there is a corresponding increase in the number of tiny blood vessels (capillaries) to deliver this greater volume of blood per beat. The number and size of mitochondria, the power plants of the muscle cells, also increase. You become more efficient at using fat as a fuel source, decreasing your reliance on your limited carbohydrate stores (muscle glycogen). Speaking of glycogen, Endurance training stimulates the muscles to store more glycogen making this fuel readily available for long duration efforts as well as high intensity workouts.

The nervous system becomes very coordinated in its recruitment and use of your slow-twitch muscle fibers, which helps improve your running economy. There’s even a stimulus for your fast-twitch muscle fibers to become more “endurance-like”.

You experience all of these adaptations quickly when starting or increasing your Endurance training. You go from feeling out of breath easily to being able to chatter throughout the entire run. Your breathing becomes easy and the legs no longer feel rusty. They seem completely happy to go for a run and when you encounter hills, there is only a mild increase in effort compared to the full-on lactic acid, breathing-to-the-max effort that you experienced before training. Objectively, you see your morning and resting pulse drop and your heart rate remain lower at a given pace.


The next section of the graph is the “Stamina” section. This zone corresponds to when you are running between two and half hour race pace to about your 25 minute race pace. Optimal Stamina training occurs when your heart rate is between 83 and 92% of its maximum (though this can vary from runner to runner), and oxygen consumption is 85-90% of max. In this zone, your breathing is fast but under control. The effort has been described as “comfortably hard” and your lactate level hangs around 2.5 to five millimolar, right about where your lactate threshold occurs.

Research has shown that training in the Stamina zone helps push several critical thresholds (lactate, ventilatory and anaerobic) to faster paces. The result is that you can run faster before crossing these thresholds. The key cardiorespiratory adaptations that result from Stamina training deal with what scientists call the “Lactate Shuttle”. While we used to think that lactate simply started being produced and eventually accumulated to the point where fatigue sets in, we now know that lactate is always being formed, just at different rates. At rest and during light exercise, only small amounts are formed. During heavy exercise, large amounts are produced. Once formed, the body has mechanisms whereby the lactate is “shuttled” to other tissues to be used for fuel, sort of like recycling. This recycling or shuttling has a maximum capacity, however. Once reached, the production of lactate outpaces its removal resulting in the accumulation of it in the blood. Thus, the lactate threshold is reached.

I should note that lactate has a partner, a hydrogen ion. When the lactate and the hydrogen ion are together, they form lactic acid. Once produced, however, lactic acid readily splits into lactate and its former pal, the hydrogen ion. Like lactate, the hydrogen ion which causes the working muscle cells to become more acidic and begin to fatigue, is controlled, up to a limit, by the body. This process is called the bicarbonate buffering system. This system captures the hydrogen ion thereby forestalling the rise in acidity in the muscles. Once this system is overwhelmed, however, the cells become more and more acidic which interferes with energy production and leads directly to fatigue.

Stamina training helps to improve the efficiency of these two processes and over time, results in less lactate and hydrogen ions accumulating, effectively pushing your lactate threshold to a higher pace.

You experience this adaptation as the ability to run longer and faster before “going over the edge” and suffering from lactic acid overload. Research has shown over and over that the speed at your lactate threshold is the most important factor in distance running success (5K to marathon racing). Push your lactate threshold faster and you will race faster over all distances. It’s therefore critical that you understand Stamina training and how to incorporate it into your program (the next two sections).

Just like in the Endurance zone, to receive the adaptations described above, you simply need to train at the paces that define the Stamina section of Graph 2.


The third section of Graph 2 is labeled “Speed”. This section corresponds to running between your five and 25 minute race pace. As compared to the Stamina section, the various physiological reactions to running at this pace start to redline. Your heart rate and oxygen consumption go from 90% up to maximum. Your breathing is fast and labored. The effort is hard and your lactate level tops four, six and even eight millimolar.

While Endurance and Stamina training stimulate adaptations that improve your efficiency of several systems of the body, Speed training works to actually increase the capacity of several of your body’s systems. Research shows that Speed training increases the enzymes that help liberate energy from our fuel sources, improves the lactic acid buffering capacity, provides a greater stimulation and training of the fast twitch muscle fibers and results in a greater ability to extract oxygen from the blood as it perfuses the muscles.

You experience this as increased speed-endurance, the ability to run fast for a long period of time. The running motion becomes more consolidated as all errant form changes (like flying elbows, funky foot plants) are eliminated. They require too much energy. Your breathing acclimates to fast, constant efforts and your legs begin to feel fast and strong.

Like the other zones, to receive the adaptations described above, you simply need to train at the paces that define the Speed section of Graph 2.


The fourth and final section of Graph 2 is the “Sprint” zone. This section corresponds to running between your one minute and your eitght minute race paces. At these speeds, the various physiological responses are all at maximum capacity. Your heart rate and VO2 reach maximum. Your effort is very hard and lactate shoots higher and higher, reaching 12 to 20 millimolar in some runners. Breathing, as you would expect, is at full capacity.

There are two key adaptations that occur from training at paces which elicit these kinds of responses. The first is neuromuscular. Research has found that during this fast sprinting, groups of individual muscle fibers become more coordinated in their “firing” (contracting) so that you can achieve greater power and speed. Likewise, different whole muscle groups (like the quadriceps, for example) get “in sync” with each other resulting in faster turnover and a smoother stride. Basically, the body becomes efficient and coordinated at turning your legs over very fast. Your running economy improves.

The second adaptation affects the bicarbonate buffering system that we discussed in the Stamina section. Since training at this pace creates large accumulations of lactic acid (lactate and its compatriot, the hydrogen ion), it challenges the body’s ability to remove these by-products. With repeated exposure to elevated lactate (and associated hydrogen ion) levels, the body improves its ability to quickly remove it.

You feel these adaptations (improved neuromuscular function and acid buffering) as a smoother, less jerky stride when running at full speed. You feel that you are powerful and can simply fly across the ground. You begin to imagine yourself looking like the sprinters, smooth and powerful. Sprint zone training seems to greatly affect the torso of the body as you begin to run not just with your legs but to generate power through your stomach, pelvis and hips.

Incorporating some training at the paces that cause these reactions is often overlooked by distance runners who think that sprinting ability doesn’t help them, except maybe in the final kick to the line. However, I’ve found that athletes who incorporate a small amount of Sprint training into their programs are less likely to be injured, tolerate Speed and Stamina training better in addition to having more powerful “kicks” at the end of racing.


Pretty simple, huh? Train within the pace ranges that categorize the different zones and you’ll derive the specific adaptations that those zones offer. By understanding these adaptations, you now fully understand what each run is doing for you. This is a very important but often overlooked part of the training process. Each and every run must have a purpose and you should know it! This isn’t meant to take the fun out of your training but more to help you decide what is most appropriate for each workout so that you have more fun, reach your potential and race your fastest.

When I make a training schedule for a runner, each and every workout lists its particular purpose. The purpose doesn’t have to be overly detailed but it should convey the goal of the workout. For example, if a runner is doing a long run (i.e., Endurance training), the goal is clear: to improve endurance, fat-burning, etc. It reminds the runner of the Endurance zone and that in order to receive the optimal stimulus that will result in the appropriate adaptation the run has easy. This makes things easy and improvement a virtual guarantee. Runners usually mess up when they either 1) don’t know the purpose of a workout and then run too fast or too slow or 2) they don’t abide by the rules that govern optimal training in a particular zone.

You, of course, will now avoid this common trap because by knowing the specific race paces that define the parameters of each training zone, you can simply set your pace to match the zone and voilà, the adaptations will occur. (Of course, it’s more work than that which is why there are several important sections to follow!)

click here to read Part 2 of McMillan Running System

click here to read Part 3 of McMillan Running System

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