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!)
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© 1999-2013 Greg McMillan
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I gotta hand it to you. Your training program really produces results.Those long intervals and fast finish runs really paid off today. Thanks for helping me to become a much better runner.