Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University
Tempo runs are a crucial part of a successful weekly training plan for half and full marathoners attempting to lower their race times. Also referred to as lactate threshold runs, tempo runs require a runner to maintain a faster pace than your normal long run pace, but over a shorter distance. A tempo run is not an interval workout. A tempo run requires the runner to maintain a pace for a much longer period of time than the typical 800, 1,200, or 1,600 meter repeats that comprise an interval workout.
Tempo runs teach your body to become more metabolically efficient with regard to lactate production and clearance. And if tempo runs are done appropriately and frequently enough they will make your marathon pace seem easier. Make no mistake, the long run is essential part of your weekly training plan and it is required to build an aerobic base and prepare you mentally to be out on a race course for the necessary time. Tempo running compliments the long run training by teaching your body to maintain speed for an extended distance.
Becoming more metabolically efficient refers to the enhanced ability your body develops over time to deal with increasingly higher levels of circulating lactate in the blood. Human skeletal muscles are composed of essentially two fiber types, slow fibers and fast fibers. Slow fibers are utilized for endurance type activities and the fast fibers are used for more explosive types of activities. When you are running at a tempo pace and your skeletal muscles are working hard, you are using not only your slow fibers but also an increasingly larger percentage of your fast fibers.
At a tempo running pace lactate is being produced in the fast skeletal muscle fibers. Once lactate is produced by the fast fibers it is released into the circulating blood, and then it has to be cleared, or removed from the blood. If lactate is not efficiently removed from the blood, it will build up and cause fatigue, which means your running pace will need to slow.
Lactate removal from the blood is accomplished in essentially two ways. First, lactate is removed from the circulating blood by the slow fibers, and secondly lactate is removed from the blood by the heart tissue. So, if your ability to remove lactate from the blood stream becomes enhanced, you will be able to handle higher levels of lactate being produced and placed into the blood.
Lactate only becomes a problem for an endurance athlete if the rate it is being produced and placed into the blood exceeds the rate that it is being removed from the blood. Indeed, one very important aspect of being more aerobically fit is your ability to handle higher levels of circulating lactate in your blood. Accordingly, the more aerobically fit you become, the higher the levels of circulating lactate you can sustain before it begins to build up in the blood stream. This is what is meant by the common expressions “raising your lactate threshold”, or “raising your anaerobic threshold”.
The automobile analogy I like to use for increasing, or raising, your lactate threshold is that tempo runs train your engine to turn over at a higher rpm before it red lines. For example, prior to training with tempo runs you may have red lined at a 9:00 minute per mile pace, but following a few months of appropriate tempo run training you may not red line until an 8:30 minute per mile pace. Remember that hitting your red line means that lactate is being released into the circulating blood (by fast fibers) at a faster rate than it is being removed from the circulating blood (by slow fibers and your heart tissue).
Running at the correct pace is the fundamental and essential key for tempo run training to be effective at raising your lactate threshold. If you run to slowly, the fast fibers will not produce enough lactate to stress the removal process by the slow fibers and the heart. Conversely, running at to fast of a pace will create a situation where lactate production by the fast fibers will quickly overwhelm the ability of the slow fibers and heart to remove it from the blood.
There are a four ways I recommend to know if your pace is correct for an effective tempo run. First is simply by feel or what we call perceived exertion. This is what I refer to as feeling like you are at a running pace that is a “comfortably hard” effort. This pace should feel as if you are working hard, but not going anywhere close to a near all out pace as you would in an interval workout. Choose a running pace that you can maintain for approximately 60 minutes.
Second is paying close attention to your breathing pattern during your tempo run. A tempo pace will likely result in a breathing pattern of two running strides inhale and one running stride exhale. Or the exact opposite depending on what is most comfortable for you. If the running pace you have chosen results in a one stride inhale and one stride exhale breathing pattern then that is to fast for a tempo run effort; you have crossed over into an interval training pace.
Third is a talk test. If your tempo run effort allows you to communicate in short three or four word burst type “sentences”, then you have likely found that “comfortably hard” tempo running pace. If you can carry on a full conversation, that is your long run pace. And if you are not able to speak at all, then you are running at an interval workout pace.
Finally the fourth and most accurate method to accurately determine your tempo running pace is by heart rate. Tempo runs should be accomplished at approximately 85% to 90% of your true maximum heart rate.