Finding Your Race Pace Article

This article was written by Jeff Godin of Blackstone Valley Performance Center

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Finding your race pace
Jeff Godin, Ph.D., CSCS, HFPD, CISSN
In any endurance sport one of the first things an athlete learns, usually the hard way, is that a pacing strategy is a key element to success. If the athlete goes out too hard, they will falter at the end and lose time. If an athlete goes out too slow, he/she may finish strong, but maybe the athlete could have finished faster. Somewhere in between is the fine line where the athlete’s pace optimizes their performance. The question is: What is the ideal race pace and how can an athlete find that sweet spot?
Exercise intensity is tied to exercise duration. You can run fast but not for very long. For example a 100 meter sprinter runs around 22 mph but for only 10 seconds, a very fast 5k is run at a sped of 14.5 mph, and a very fast marathon is run around 12.5 mph. The figure below shows this relationship in terms of wattage on the bike. It can be seen that higher power outputs can be held for short durations (800watts for 10s) and lower power outputs can be held for longer durations (180 watts for 1+ hrs.).  (Graph didn’t come out- go to www.bvhp.com for full article with graphs).

It is even trickier in the sport of triathlon where the effort in one activity is going to affect the performance in another. For example, someone could run under 21 minutes for a 5k, but find it very difficult to run this pace after riding the bike for 20K.
In a perfect world we could predict race pace in terms of speed for the swim, bike, and run. But since the world isn’t perfect, it has currents, hills, heat, wind all of which make using speed for pacing, alone, tenuous. I am not suggesting that you disregard this important parameter, rather let’s use it in conjunction with other obtainable data.
Power meters have become very popular on the bike. There are a few different types available and each has pros and cons. They are all reliable, but the watts they record may vary slightly from brand to brand because of where the data is collected, i.e. cranks versus hub. Power is an excellent way to pace on the bike. Power is a measure of work produced per unit of time. It is unaffected by the environment. So, for example, if I am climbing a hill and my power is 300 watts, speed is 10 mph and I compare that to riding on a flat road at 300 watts where my speed is 25 mph I am expending the same amount of energy regardless of the gradient of the road and speed. Unfortunately we don’t have power meters for the swim or for the run.

It would be advantageous to be able to monitor our pace based on our physiologic response to the exercise. This is where heart rate can provide us with meaningful information. Heart rate is linked to our metabolism. During events lasting longer than 30 minutes, 90-99% of the energy is derived aerobically, that is, it requires oxygen. When you start to exercise, your skeletal muscles call for more energy (ATP).
You have some stored ATP but not very much, there is only enough to last 10s of high intensity exercise. As the muscle calls for more ATP other energy systems kick in to convert carbohydrate, fat, and protein into ATP. This requires oxygen which is supplied by the cardiorespiratory system. The increase in energy demand, results in an increased oxygen demand, which results in an increased cardiorespiratory response, namely heart rate goes up. There is a direct relationship between heart rate and energy expenditure, if you know one you can predict the other.
How can you use this information to find your ideal race pace for specific events? The first step is to identify the intensity that is related to the anaerobic threshold (AT). What AT represents is hotly debated, but a few things are certain: 1) carbohydrate is the only fuel used at this intensity; 2) exercising above AT results in metabolic acidosis; 3) exercise time is limited above this threshold because of the limited availability of carbohydrate and the developing metabolic acidosis. Preferably, testing for AT is done in a human performance lab with a metabolic cart and lactate analyzer. But you can estimate it with a time trial test. Pick a bike or run course that you can complete in about 45 minutes and after a thorough warm-up, ride/run these distances as fast as possible. Wear a heart rate monitor and record your average heart rate. This heart rate approximates your heart rate at the lactate threshold. Once you know this number you can have an idea where your heart rate needs to be for different distance races.
Races lasting 1-1.5 hours: Target heart rate can be at or just above AT. The longer your anticipated time, the lower your heart rate should be. Target heart rate should be between +5 beats of heart rate at AT. Some well trained athletes may be able to go above this guideline because of their ability to tolerate high levels of metabolic acidosis. A novice may be more comfortable below this guideline because they haven’t developed a strong buffering system.
Races lasting 2-3 hours: Target heart rate should be in the range of 93-99% of AT heart rate. You should try an avoid going above AT for too long. Not only will the metabolic acidosis associated with exceeding AT cause premature fatigue, but you will be wasting valuable glucose. When you go above AT more ATP is produced anaerobically, this produces two units of ATP per unit of glucose. When ATP is produced aerobically it yields 32 units of ATP per unit of glucose. The advantage of avoiding too much work above AT is clear; producing most of ATP aerobically will spare the glucose for later in the race.
Races lasting 4-6 hours: Target heart rate should be in the range 85-92% of AT. In this heart rate range you utilize more fat as a fuel. This is extremely important because in a race of this length you do not have enough glucose stored in our body to last the whole race and you can’t replace it fast enough. If you utilize more fat, you can spare your glucose until later in the race.
Ultra distances beyond six hours: A target heart rate of 75-84% of AT would be advisable. At this intensity, again, you utilize more fat as a fuel and spare glucose. Also, the lower intensity doesn’t produce as much of a heat load and you would lose less fluid through sweat and are not as likely to over heat. Both dehydration and heat stress are major contributors of fatigue during ultra distance events.
Below is a working example for an athlete with a AT heart rate of 165 on the bike and 170 on the run:
Time
Intensity
Bike AT 165
Run AT 170
1-2hrs
LT HR + 5
160-170bpm
165-175 bpm
2-3 hours
93-99% LT
153-163bpm
158-168 bpm
4-6 hours
85-92%
140-152 bpm
144-157 bpm
6+
75-84% LT
123-139 bpm
127-143 bpm
These percentages are based on the average metabolic/ physiologic response during exercise and are based upon some reasonable assumptions and would apply to most people. Some athletes may be successful outside of these ranges because of their individual response. Working with an exercise physiologist can help you better define these zones. Follow your heart; it will help you achieve your optimal race pace.
Jeff Godin is an Associate Professor and Chair of the Exercise and Sort Science Department at Fitchburg State College and co-owner of Blackstone Valley Human Performance (www.bvhponline.com). He can be reached at jgodin@bvhponline.com.