The Heart's Function

from Polar Electro

You may think that monitoring your heart rate is too much science and not enough play, but it can actually increase your enjoyment.

Cardiovascular system
The cardiovascular system of the body has three components:
· The heart (cardiac muscle)
· The blood vessels
· The blood
The cardiovascular system serves a number of important functions in the body. It e.g. delivers oxygen and nutrients to, and removes carbon dioxide and metabolic waste products from, every cell in the body.

Heart
The heart is the primary pump that circulates blood through the entire vascular system. Heart has two atria acting as receiving chambers and two ventricles acting as sending units. The right side of the heart (right atrium and ventricle) receives the blood that has circulated throughout the body and sends it into the lungs for reoxygenation. The left side of the heart (left atrium and ventricle) receives the oxygenated blood from the lungs and sends it out to supply all body tissues.
Figure 1. The heart and blood circulation.
The direction of blood flow is indicated by arrows.

Cardiac muscle has the unique ability to generate its own electrical signal that allows it to contract rhythmically (about 60-80 beats per minute). Although the heart initiates its own electrical impulses, their timing and effects can be altered by the parasympathetic nervous system, the sympathetic nervous system and by hormones. At rest, parasympathetic system activity predominates but during times of physical or emotional stress the sympathetic system predominates. The electrical activity of the heart can be recorded as an electrocardiogram (ECG).
Figure 2. Resting ECG. Heart rate 60 beats per minute.
Figure 3. Exercise ECG. Heart rate 170 beats per minute.


The cardiac cycle includes all events occurring between two consecutive heart beats. In mechanical terms, it consists of all heart chambers undergoing a relaxation phase (diastole) and a contraction phase (systole). During diastole, the chambers fill with blood. During systole, the chambers contract and expel their contents. Ventricular contraction (systole) begins during the QRS complex and ends in the T-wave.

Heart rate is one of the simplest and most informative of the cardiovascular parameters. When one begins to exercise, heart rate increases rapidly in proportion to the exercise intensity. In Polar heart rate monitors the transmitter in the belt detects the ECG. When the transmitter picks up a QRS complex, it transmits an electromagnetic signal, which is detected by the wrist receiver.

By monitoring heart rate, the simple observation that the harder we exercise, the faster our heart beats is put to good use. Professional athletes and amateurs alike have for decades been relying on the information provided by their heart rate monitor for the following reasons:
 

1. A heart rate monitor is like a rev counter, giving a precise measurement of exercise intensity.
2. Training at your own ideal pace is made possible with a heart rate monitor.
3. Direct measurement of heart rate during exercise is the most accurate way to gauge performance.
4. Progress can be monitored and measured, increasing motivation.
5. It maximizes the benefits of exercise in a limited amount of time.
6. It introduces objective observation. Are you on the right track? Are you improving?
7. It is a tool for regulating frequency and intensity of workouts.
8. Because of the immediate feedback it provides, heart rate monitoring is an ideal training partner.

How does it work?

When you start training, your heart rate increases rapidly in proportion to the intensity of the training. In Polar Heart Rate Monitors, the transmitter belt detects the electrocardiogram (ECG - the electric signal originating from your heart) and sends an electromagnetic signal to the Polar wrist receiver where heart rate information appears.

The heart moves blood from the lungs (where the blood picks up oxygen) to the muscles (which burn the oxygen as fuel) and back to the lungs again. The harder the training, the more fuel the muscles need and the harder the heart has to work to pump oxygen-rich blood to the muscles.

As you get fit, your heart is able to pump more blood with every beat. As a result, your heart doesn’t have to beat as often to get the needed oxygen to your muscles, decreasing resting heart rate and exercise heart rate on all exertion levels.

Why Monitor Heart Rate During Outdoor Activities?

You may be familiar with heart rate monitoring in running and road cycling, but it is just as valuable during other outdoor sports.

There are many reasons to monitor your heart rate during Outdoor Sports:

• Pace - You can use heart rate as a speedometer to set a pace that you’ll be able to maintain. The personalized nature of heart rate means the pace will be right for you.

• Energy expenditure - Measuring heart rate allows the determination of energy expenditure so that you know how many calories to ingest to keep going.

• Adaptation - Heart rate responds to internal and external factors, giving you a way to monitor your internal condition (energy expenditure, aerobic fitness and indirectly - hydration) and the effects of altitude and weather. The Polar HRrest test can help you determine how you’re adapting.

• Intensity - Heart rate is an accurate measure of the intensity of an activity - you’ll know how hard you are working.

• Safety - Monitoring heart rate can keep you from pushing too hard, thus reducing your risk of injury.

• Progress - Heart rate allows you to objectively measure improvements in your level of fitness.

• Planning - A plan that includes how hard to exercise, measured using heart rate, will help you accomplish your goals. Use the Polar FitnessTest to measure changes in your level of fitness and evaluate your plan.

• Variety - You may think that monitoring your heart rate is too much science and not enough play, but it can actually increase your enjoyment. You can be extremely creative with your time and avoid the pitfall of doing the same thing day after day.

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