Augmenting Your Heart Rate Monitor Training
By Rich Strauss

It is critical that you understand two things. The first is that heart rate measures the CUMULATIVE stress on your body. This cumulative stress includes the intensity of your exercise as well as recovery, hydration, etc.

The second is that to race at a certain pace, you must train at, just above, or sometimes significantly above that pace. To run at pace x, you need to achieve the fitness (endurance, muscular endurance, lactate tolerance, the ability to efficiently burn fat, etc) to run pace x AND the neuromuscular coordination to run at pace x. The only way to run pace x is to run at x or faster. With all of the attention paid to heart rate training, the importance of pace is a commonly ignored point. I suggest you read Jack Daniels' Running formula for a comprehensive discussion of the use of pace in training: cruciblefitness.com/library/books/books.htm

Pace is a measurement of work produced. When a 150 pound athlete runs around a track at 1:15/400m pace, he produces a very specific amount of power, which results in a specific workload. His heart rate only measures how much his body is stressed while producing that workload. If you train at that workload consistently, over time your body will adapt and you will be better able to maintain that workload. Eventually this workload will be less stressful. This will be reflected in a lower heart rate at the same pace. You have to ask yourself if you train to race at a lower heart rate, or if you train to race at a faster pace. If your objective is to race faster, then you need to recognize that heart rate is an indirect measure of workload, clouded by many environmental and personal variables. For your training to be most effective, you should add an intensity measurement tool, such as Critical Power or Critical Speed, that measures the actual work produced.

Wouldn't it make more sense to use both heart rate and pace to measure intensity? That way you can have two data sets with which to make a DECISION about how to train. For example, my training plan calls for a tempo run at or just under my lactate threshold heart rate (LTHR). For me this is about 172 bpm. I also define a tempo run as a Critical Speed value, CS 30 (my average pace in a 30 min time trial). This pace is (was, I'm out of shape right now) 6:45-50. Because I want to use both hr and pace to define my workout, I decide to do my workout on the track. After my usual warm-up I accelerate to tempo pace. I settle into a 172 heart rate, but my pace is only 7:00. Umm. What to do. I quickly do some thinking and remember that I only got 5 hours sleep last night, I'm a little dehydrated, and it's a bit warm. I decide that my heart rate is reflecting these cumulative variables, so I increase my pace to 6:50 and my heart rate settles at 175.

I would argue that had I only used my heart rate to determine how hard to train, I would not have trained hard enough (in this case fast enough) to achieve the desired training response. Does this mean that you should throw the hrm away and train only by pace? No, but by using other tools, such as Critical Speed or Critical Power, you can gather more data and make more informed training decisions.

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