Because swimming works both the upper and lower body with little or no impact, it is considered one of the best cardiovascular modes of exercise. To make the best use of your exercise time, it is important to train at the right intensity. Monitoring your exercise heart rate is a reliable indicator of intensity level, but target heart rate calculation is somewhat different in the water from on land.
Why the Difference?
There are many theories for the difference between heart rate, or HR, on land vs. water. According to Joanne Maybeck, who provides workshops on “Aquatic Heart Zone Training”, there are several factors. Buoyancy in the water reduces the effect of gravity. Therefore, it takes less effort for the heart to deliver oxygen to the rest of the body. Temperature may also be a factor. Compared to land-based activity, the heart doesn’t have to work as hard to cool the body. Another variable is the “Dive Reflex,” which is a neurological response that happens when the face is in the water. This triggers a reduction in heart rate and blood pressure. Some may even experience this dive reflex in chest-deep water.
Determine Your Resting Heart Rates
Before you can calculate your exercise target heart rate range for the water, you must determine your resting heart rate both in and out of the water. Stand outside of the pool for three minutes to allow your heart rate to reach steady state. Next, count your pulse rate for one minute. Record the number. Slip into the water up to your shoulders and wait three minutes. Again, count your pulse for one minute and record the number. Finally, subtract the water pulse rate from the land pulse rate. This number is called your “aquatic deduction.”
Determine Aquatic Maximum Heart Rate
A simple formula for calculating your maximum heart rate, or MHR, for water exercise is 220 minus your age, minus your aquatic deduction. For example, the MHR of a 40-year old with an aquatic deduction of eight would be 172, using the following equation: (220-40) - 8 = 172.
Determining Your Exercise Heart Rate
For most, exercising at maximum intensity is not feasible or safe. To determine your training intensity, multiply your aquatic MHR by an appropriate percentage, ranging from 50 to 85 percent. For example, if you are just beginning to exercise, or have some health concerns, stay at the bottom of the range. If you want to challenge yourself, multiply your MHR by 80 and 85 percent. This will give you a training range for your water-based exercise.
Other Methods of Measuring Exercise Intensity
Measuring exercise HR on land can be done without stopping the exercise, whereas in the pool, you will have to pause to assess heart rate. Research published in the Journal of Strength and Conditioning demonstrates that an individual’s rate of perceived of exertion, or RPE, is also a reliable indicator of measuring exercise intensity. On a scale of one to 10, exercising between a four and eight is beneficial for promoting cardiovascular fitness. It then becomes an individual choice when measuring exercise intensity. Initially, you may want to use both assessment methods to ensure you are staying on track.
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