In last week’s RBR Newsletter Dr. Mirkin wrote an excellent column on Tips for Keeping Your Maximum Heart Rate Up As You Age. He referenced a study in his article:
“A recent study from Ball State University in Indiana shows that exercising as you age slows down the loss of maximum heart rate (Med Sci Sports Exerc, Jan, 2016;48(1):73-81). Keeping your maximum heart rate up means that your heart isstronger, which allows you to exercise faster and longer. Nearly 650 healthy men and women, ages 18-80, not taking any heart-rate-altering medications, completed two treadmill all-out efforts at least one year apart. The older participants had lower average maximum heart rates, but those who were most fit and had the highest values had the least drop in their maximum heart rates over the year, regardless of age.”
This makes sense — if you continue to exercise, especially if you continue to exercise with intensity, your max heart rate won’t drop as fast as if you sit on the couch and watch TV all the time.
Many riders use max heart rate to set training zones, because that’s the default method used by heart rate monitors. Both Polar and Garmin heart rate monitors set the training zones based on max heart rate, which the HRM calculates. You have the option of putting in a more refined estimate of your max HR by suffering through a max HR test.
Think of a Car
Here’s a simple analogy: think of a car. The higher the RPMs it can produce, the faster you go in a drag race. However, does this car get good gas mileage at your normal driving pace?
The human body is more complicated than a car, especially a race car. Your body is more like a hybrid with three different engines (energy systems):
1. Oxidative aerobic system (low power / long duration).
2. Glycolytic anaerobic system (moderate power / short duration)
3. ATP-PC (high power / short duration)
To complicate matters further, you have three different transmissions (your legs have three different types of muscle fibers):
1. Slow-twitch (low power, great endurance)
2. Fast-twitch IIa (moderate power and endurance)
3. Fast-twitch IIb (high power and shorter endurance)
Each energy system and fiber type responds to different kinds of training.
How Do You Monitor Intensity?
A prior Question of the Week was:
How Do You Monitor Intensity While Riding, If At All?
- 49%: I listen to my body, i.e. perceived exertion
- 24%: I use heart rate zones determined by my max heart rate
- 11%: I don’t monitor intensity
- 10%: I use power zones determined by my functional threshold power
- 4%: I use heart rate zones determined by my lactate threshold
- 2%: Something else
I’m very pleased that 83% of our readers monitor your intensity while riding, because training by intensity is the most effective way to train! Dr. Mirkin and I agree on this. He says:
“I believe that all healthy people should use some variation of a stress-and-recover exercise program, in which they damage their muscles by going a little harder and faster on one day, then feel soreness in their muscles and go much slower on the next day. When their muscles feel fresh again, they can take another intense workout.”
However, setting your training zones based on max heart rate isn’t the best way.
Max Heart Rate Doesn’t Show Cycling Fitness
Imagine two club riders: Joan is 41, and she started riding when she was 25. This year she suffered through a stress test in a lab and determined that her max HR is 160 bpm. Jim is 55 and just started riding last year. He’s also suffered through a stress test this year to determine his max HR — 171 bpm. Although Joan is younger than Jim, she has a lower max HR. Women aren’t small men. You have different physiological responses to exercise, including lower max HRs, all other things being equal.
Because Jim has a higher max HR, is he fitter?
In each rider’s stress test the lab also determined Joan’s and Jim’s Anaerobic Thresholds (AT). Riding at moderate intensity your oxidative aerobic system is providing the energy for your muscles. As you go harder and harder, your glycolytic anaerobic system starts providing energy, in addition to your aerobic system.
Where your body starts producing significant amounts of energy from your anaerobic system is your AT. This is where your body also starts producing significantly more lactate than your body can clear. Another name for Anaerobic Threshold is Lactate Threshold (LT).
The lab tech says that Joan’s AT is 136 bpm, 85% of her max HR and that Jim’s AT is 103, 60% of his max HR.
Why the difference?
Your max HR is primarily a function of your genetics and age, although fitness does play a role. Your AT represents your current fitness and can change significantly with training. If Jim trains hard for several years he may maintain his max HR at 171 bpm. More importantly, he’ll raise his AT to 128 bpm, 75% of his max HR. (Depending on fitness, AT ranges from 65% to 90% of max HR.)
On club rides Joan rides with the fast bunch, drops the guys on hills and holds her own in the sprints. Jim rides with the new riders’ slow group and is gradually getting fit enough to stay with the group.
Max heart rate doesn’t take into account differences in fitness. Joan is much fitter than Jim, and their heart rate responses are much different.
Basing Joan’s and Jim’s training zones on each rider’s max heart rates doesn’t take into account fitness. But why not?
Your cycling fitness is a result of:
1. How fast your heart can beat in a sprint.
2. Your heart’s stroke volume: how much blood it pumps per beat.
3. Your VO2 max, how much oxygen your muscles use out of the oxygen delivered by your cardiorespiratory system. Your VO2 max sets the upper limit on your performance.
4. How hard you can ride and how fast your heart beats before you start to go anaerobic, i.e., the percentage or fraction of your VO2 max that you can sustain for any given time.
5. How much power your muscles can deliver.
6. Your pedaling economy: how efficiently that power moves you down the road.
All six of these improve depending on how long you’ve been riding and the kind(s) of training that you do. Training based on your by max HR only takes into account the first factor.
How to determine your training zones by perceived exertion, anaerobic threshold, and power are explained in my eArticle Intensity Training: Using Perceived Exertion, a Heart Rate Monitor and a Power Meter to Maximize Training Effectiveness. It also explains how to use the zones effectively to improve your training to meet your personal goals.