Exercise and Heart Rate

Exercise and Heart Rate

Author: Stan Reents, PharmD
Posted: 5/6/2007 10:02:03 AM

Many people know that monitoring their heart rate during exercise helps them determine how hard they are working. And others know that exercising at an intensity that keeps their heart rate in a specific range will result in a "training" effect.

But, recently, new research has revealed other ways you can use your heart rate to determine not only how hard you are exercising, but, also how healthy your cardiovascular system is. This review will discuss 4 different ways you can use your heart rate to monitor your fitness. Your personal trainer may not even know some of these details.

MAXIMUM HEART RATE

Before you can calculate your "target exercise heart rate," you first need to determine your "maximum heart rate".

The traditional formula for calculating maximum heart rate is:

• Max HR = 220 - age

However, several years ago, researchers in the department of kinesiology and applied physiology at the University of Colorado in Boulder noticed that this formula underestimated exercise heart rates in older subjects.

Hirofumi Tanaka, PhD, and his group conducted an exhaustive review of 351 studies involving nearly 19,000 subjects and derived a new formula. They then validated the new formula in 514 healthy subjects.

The formula they propose is:

• Max HR = 208 - (age x 0.7)

In 40-year-old subjects, both formulas yield the same result (ie., 180 beats per minute). However, the Tanaka equation produces slightly lower limits (than the old formula) in subjects younger than 40, and raises the limit slightly in subjects older than 40 years old.

Other formulas exist. What's important is that, for the elderly, and people who are not in shape, maximum heart rate should be determined by calculation since it would be too risky for these people to submit themselves to an all-out exercise test.

Determining Maximum HR From An All-Out Run:

The November 2004 issue of Runner's World magazine offers a method for fit runners to determine their maximum heart rate:

• warmup
• run as hard as you can for 3 minutes
• walk for 2 minutes
• run as hard as you can for another 3 minutes

During the last minute of running, you should be at your maximum heart rate. NOTE: Do not do this unless you are fit, or have been given a clean bill of health by your physician.

But, let's say you're not interested in winning your age group in next month's neighborhood 10-K; you are only exercising for health reasons. In this case, you still need to know your maximum heart rate. This allows you to determine your "training" heart rate, which is explained below.

There's also a medical use for knowing maximum heart rate. Cardiologists have determined that the inability to attain a target heart rate during exercise appears to be an ominous predictor of mortality. Researchers at the Cleveland Clinic found that patients who could not reach at least 85% of their predicted exercise heart rate had a higher risk of death (Lauer MS, et al. 1999).

TRAINING HEART RATE

Now that you know your maximum heart rate, you can determine your training heart rate. Coaches and their athletes know that driving the heart rate up into a specific range is the key to improving performance in aerobic events like cycling, distance running, etc. For example, Ed Eyestone offers the following guidelines in the November 2004 issue of Runner's World magazine:

• 70-80% max HR: aerobic training pace
• 80-90% max HR: lactate threshold pace
• 90-97% max HR: long-interval pace
• 95-100% max HR: short-interval pace

Serious endurance athletes (triathletes, distance runners, etc.) will train mostly at the aerobic training pace. About 10% of their training will be at the lactate threshold pace. Extremely-intense "intervals" make up only a small percentage of the overall training plan.

Training heart rate is also helpful for people who want to exercise for health benefits. Research shows that untrained individuals will begin to improve their aerobic fitness when they exercise regularly at 50% of their maximum heart rate (Pollock ML, et al. 1998).

For example, for a 60-year-old person, the maximum heart rate (using the Tanaka equation) is 166. Fifty percent of that is 83 beats per minute. Thus, exercise does not need to be exhausting to achieve a health benefit.

RECOVERY HEART RATE

"Recovery" heart rate is a determination of how long it takes your heart rate to return to normal after you stop exercising. This concept is mostly for people who are out of shape. People with a slower recovery are at higher risk of sudden death than people who recover more quickly.

Researchers at the Cleveland Clinic exercised patients on a treadmill, then measured their heart rate 1 minute after running stopped and compared it to their peak heart rate. The failure of heart rate to fall rapidly after exercise stopped was associated with increased overall mortality (Cole CR, et al. 1999).

A similar result was seen in a study from France. Cardiologists exercised patients on a stationary bike for 10 minutes, then measured their heart rate 1 minute after cycling stopped and compared it to their peak heart rate. Patients with the poorest recovery had 2.1 times the risk of sudden death compared to patients with the best recovery (Jouven X, et al. 2005).

RESTING HEART RATE

And, finally, the 4th way you can use your heart rate to monitor your exercise program is to simply take your pulse while at rest. Resting heart rate is another indicator of your aerobic fitness.

One of the dramatic things that happens to your heart when you become aerobically fit is that your heart pumps more blood with each beat. This is known as "stroke volume". Since more blood is pumped with each beat, the heart doesn't need to beat as fast, so, resting heart rate is slower.

In one study of female runners, the resting heart rate directly related to how far the women ran per week (Williams PT. 1996):

MILES RUN	RESTING HR
0-10 miles/wk	69
10-20 miles/wk	66
20-30 miles/wk	65
30-40 miles/wk	63
40-86 miles/wk	61

You may have heard of marathon runners who have resting heart rates in the 50's, or, even in the 40's. Generally, this is a sign of a strong heart.

Unfortunately, the opposite is also true. In one study of middle-age men with no evidence of cardiovascular disease, a resting heart rate of 75 beats per minute or higher had 3.5 times the risk of sudden death compared to men with resting heart rates of less than 60 (Jouven X, et al. 2005).

SUMMARY

So, it turns out that something as simple as keeping track of your heart rate can tell you a lot about your health and fitness. Here's how to do it:

•Resting Heart Rate: Take your pulse as soon as you wake up in the morning, preferably, without an alarm clock, and definitely before that first cup of coffee. Take it while you are still lying in bed; don't sit up. If you don't want to do a 60-second count, then do a 6-second count and simply add a zero.

•Maximum Heart Rate: This was discussed above. To repeat, do NOT do the running test unless you have a clean bill of health from your physician. Instead, use the formula by Tanaka et al. listed above.

•Training Heart Rate: If you simply want to exercise for health benefits, you only need to exercise at about 50-60% of your maximum heart rate. However, if you want to improve your times in a 10-K race for example, then you need to push your HR into the 70-90% range periodically. Since it is very difficult to take your pulse when you are exercising this hard, use a heart rate monitor.

Source: http://www.athleteinme.com/ArticleView.aspx?id=275