If you’re a cardio-conscious athlete, you are aware of the importance of pacing your workout to hold your heart rate within a specific training zone. If you are new to swimming, however, you may not be aware that your heart rate on dry land differs from your heart rate while exercising in the water. Exercising at heart rates equivalent to those on dry land may lead to overtraining, so adjust your heart-rate expectations when you enter the water.
Dry Land Heart Rates
Your training zone on dry land is defined as a percentage of your maximum heart rate. To calculate your maximum heart rate, subtract your age from 220. Your target heart rate zone to avoid overtraining is 50 percent to 85 percent of this number when training on land. For example, a 30-year-old’s maximum heart rate is 190 beats per minute making her training zone is 95 to 162 beats per minute.
Swimming Heart Rate
Your heart beats slower when you’re in the water than on land, so you must reduce your training heart rate while you’re in the water. According to the website for Los Angeles Trade Tech, your heart rate drops by 17 beats per minute when you swim. For example, a 30-year-old athlete’s maximum swimming heart rate would be 173 beats per minute (190-17=173) and her training zone would be between 78 (95-17=78) and 145 (163-17=145) beats per minute while swimming.
Cooling Effects of Water
Water conducts heat away from your body much more efficiently than does air, cooling your body much more quickly. Part of the cardiovascular response to exercise is an effort to move hot blood from deep within your body to your skin so it can radiate heat. Because the heart does not have to work as hard to cool your body off when it’s in water, your heart rate when swimming is generally lower than if you were doing an exercise at a similar exertion level on land.
Although you barely notice it when you’re close to the surface of the water, hydrostatic pressure pushes against your body when you’re in the water. This pressure slightly increases your blood’s natural tendency to return to your heart—a process called venous return—and also lowers the load put on your heart as you swim.
Respiration and Heart Rate
When you hold your breath, your heart rate declines. Most swimming workouts require that you control your rate of respiration, breathing only at specific times. This slower, controlled breathing rate helps to lower your heart rate, which slows to match your body’s slowed oxygen intake.
Mammalian Diving Reflex
Although scientists aren’t sure why, when you put your face in the water, you trigger the mammalian diving reflex, an autonomous nerve reflex that lowers your heart rate and blood pressure. The mammalian diving reflex is also triggered for some people when they are standing chest deep in water.
- Digital Vision./Photodisc/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.