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Pace or Pulse The Great Debate

The great debate - what is more useful in training: your pace or your pulse/heart rate (HR)? Proponents of each feel equally strong. Leaving subjectivity and economics aside; what does science say?

Regarding Heart Rates
The heart is a muscle which gets stronger, larger and improves efficiency with conditioning. (i.e. HR lowers and volume of blood pumped per beat increases)
Exertion raises HR and generally more exertion means higher HR.
HRs have some correlation to other physiologic changes in our bodies. (i.e. lactate threshold)
HR may indicate the need for rest if resting HR is elevated in the morning
Maximum HR is derived from multiple formulas that are estimates and that vary by 10 or more beats per minute.
Individual maximum HR can be reasonably established in a controlled laboratory setting with qualified scientists.
HR lag is the effect of HR rising after an effort is completed. (i.e. During fast interval training, your HR will continue to rise after you stop.)
HR drift is the effect of HR to slowly rise over longer periods of exercise time with constant physical output. (i.e. HR tends to rise even though you’re maintaining your goal pace in a marathon.)
HRs vary greatly between individuals. (i.e. All physically fit 20 year old males don’t have the same resting, maximum or workout HR.)
Individual differences affect HR. (i.e. gender, hormones, medications, hydration, sleep status, stress, body position – even upright to aerobar positions on a bike.)
HR is affected by the environment. (i.e. humidity, temperature, elevation.)
HR is an indirect measurement of exercise intensity.

Regarding Pace
All races are timed and are from a starting point to an ending point.
The first one to the finish – wins. (Ok, some exceptions for handicapped races, age graded races, etc.)
In order to run a specific time for a specific distance a runner should do training at that pace. (This is neuro-muscular specificity. Muscles will function best in the way they are trained.)
In order to run fast, you must train fast. (This also is neuro-muscular specificity. Run slow to race slow. Run fast to race fast.) Pace is a direct measurement of intensity.

Some Other Tidbits
From the experts (exercise physiologists):
Subjective rating (1-10 scale) of effort in a workout was more accurate than HR in correlating to pace in at least one study.
HR ranges are prescribed to guide training efforts. (i.e. 70-85% of MAX HR = aerobic range)
A given HR has little to no correlation to pace. (i.e. A 7:00 mile does not equate to a given HR.)
HR monitors are often recommended for novice runners in order to learn “effort” levels to avoid over training. (i.e. use as a biofeedback device)
HR monitors vary in accuracy and need to be calibrated.

A Couple Final Points
I have had triathletes tell me they could have run faster but they listened to their “coach” who told them to keep their HR within a specific range. The result was a disappointing outing. I have had a number of HR monitor wearers relate to me how much HR varies from day-to-day and run-to-run, despite feeling fine. The fact is if you follow the “ranges” rigidly you will run distance races progressively slower. And finally, a college coach and HR use advocate told me that for one workout, he has his runners go out to a half-way keeping their HRs at 140 then turn around and return in 18:00. Why he didn't use a HR to guide the effort on the way back? Because he wanted them to run at a fast "pace" to get used to racing and running hard for the last half of the race. Pace again is the critical factor not HR.

If you run to improve your times, regardless of the distance or pace, HR is simply too inaccurate to guide us. So when it comes to heart rate monitors, the research verdict is in - save your money, buy another couple pair of shoes instead. On the other hand, if you like numbers, you can afford it and it motivates you; go for it.

In the end, I know of no race that evaluates HR (MAX, average or recovery) to determine the winner; to determine your personal record; or to break records. Until research can support otherwise, neuromuscular specific training, not HR is the ticket!

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