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Aqua Beat
Heart Rate Monitors Make a Splash!
Part Two
By
Joanne Maybeck
This is the second of four articles about using
this hot new fitness tool in aquatic exercise classes and personal
training.
In Part One (in the February/March 2000 issue),
we learned what a heart rate monitor is, how to use it, and that
monitors can be used in the pool as a superior way to accurately and
effortlessly measure heart rate in beats per minute. This is a great
tool for aquatic fitness instructors and personal trainers who need to
know participants’ and clients’ heart rates. We also learned where
to purchase a monitor. So…
Now that I have my monitor, what
should my heart rate be, when I exercise?
That depends on how you calculate it!
Traditionally, the equation “220-age” has
been used to estimate a person’s maximum heart rate. And, an intensity range of 60 to
90% of a person’s estimated maximum heart rate is considered to elicit
a safe cardio respiratory or aerobic effect during training.
Remember the poor pool participants in Part One, who
were frantically searching the wall chart for what their heart rate
should be, when the instructor asked them to take a pulse rate? Most heart rate wall charts
follow the “220-age” equation, and display the 60 to 90% range for
various age groups (20, 25, 30, 35, and so on).
A more accurate way to calculate exercise intensity via
heart rate is to use Karvonen’s formula. To do this, you must know
your resting heart rate. Find
it by taking your heart rate for 60 seconds for three mornings before
rising from bed, and average the three.
Then, calculate as follows:
220 – Age – Resting Heart Rate = Heart Rate
Reserve
Heart Rate Reserve x 50% + Resting Heart Rate = Minimum
Training Threshold
Heart Rate Reserve x 85% + Resting Heart Rate = Maximum
Training Threshold
But, is everyone’s maximum heart
rate “220 – their age”?
No way! And,
it’s true that both of the methods above are based upon that
assumption. So, where did “220” come from? It supposedly relates somehow to
newborn babies’ maximum heart rate. But, no one has put a baby on a
treadmill yet, to work them to the max. And, research has established
that there may be a margin of error as large as 30 beats per minute in
“220” based formulas.
So, what is the best way to
estimate maximum heart rate?
World-class athlete and heart rate monitor
“guru” Sally Edwards calls this the Best-Fit Formula. After years of searching for a better formula, she
believes it to be the most accurate to date. Here it is:
210 minus 50% of your age minus 5%
of your body weight (pounds) + 4 if male and 0 if female = Estimated
Maximum heart rate.
But,
exercising in the water throws another curve ball…
Are
heart rates during aquatic exercise the same as on land?
No! Aqua heart rates are 13% or 17
beats per minute lower in water than heart rates during comparable land
exercise. Why is my heart
rate lower in water than on land? There
are five theories. And they
make good sense!
Temperature - Water
cools the body with less effort than air. This reduced effort means less
work for the heart, resulting in a lower heart rate.
Gravity
- Water reduces the effect of gravity on the
body. Blood flows from below the heart back up to it with less effort,
resulting in a lowered heart rate.
Compression - Water
is thought to act like a compressor on all body systems, including the
vascular system, causing a smaller venous load to the heart than
equivalent land exercise.
Partial Pressure - A gas
enters a liquid more readily under pressure. In water exercise, the gas
is oxygen and the liquid is the blood. So, more efficient gas transfer
due to water pressure may reduce the workload of the heart.
This
is a primitive reflex associated with a nerve found in the nasal area. When the face is submerged in water, this reflex lowers heart
rate and blood pressure. This reflex is stronger in some individuals
than in others. Some research suggests that the face doesn’t even need
to be in the water for the dive reflex to occur. Some people experience
its effect when standing in chest deep water.
So,
how do I calculate my aquatic target heart rate?
Take a
13% or 17 beats per minute deduction from your minimum and maximum
training thresholds on land.
So, strap on your heart rate monitor, jump in the pool,
and finally know that you are exercising at a more accurate aquatic
target heart rate!
Next … Using heart rate monitors to
“tailor” workouts, and useful features of monitors on the market
Joanne
Maybeck is a fitness instructor and personal trainer in New York City. She is certified by ACSM, ACE,
AEA, and AAAI/ISMA. Joanne
presents the CEC workshop Aquatic Heart Zone Training and will soon
offer on-line heart monitor education. She believes in training with heart! For more about Joanne, please
visit her Internet web site or email her at FitNYC@aol.com
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