Heart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute (BPM), it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and tracking of medical conditions. It is also used by individuals, such as athletes, who are interested in monitoring their heart rate to gain maximum efficiency from their training.
Heart rate is measured by finding the pulse of the body. This pulse rate can be measured at any point on the body where an artery's pulsation is transmitted to the surface - often as it is compressed against an underlying structure like bone - by pressuring it with the index and middle finger. The thumb should not be used for measuring another person's heart rate, as its strong pulse may interfere with discriminating the site of pulsation Some commonly palpated sites include:
The ventral aspect of the wrist on the side of the thumb (radial artery)
- The ulnar artery
- The neck (carotid artery),
- The inside of the elbow, or under the biceps muscle (brachial artery)
- The groin (femoral artery)
- Behind the medial malleolus on the feet (posterior tibial artery)
- Middle of dorsum of the foot (dorsalis pedis).
- Behind the knee (popliteal artery)
- Over the abdomen (abdominal aorta)
- The chest (aorta), which can be felt with one's hand or fingers. However, it is possible to auscultate the heart using a stethoscope.
- The temple
- The lateral edge of the mandible
A more precise method of determining pulse involves the use of an electrocardiograph, or ECG (also abbreviated EKG). Continuous electrocardiograph monitoring of the heart is routinely done in many clinical settings, especially in critical care medicine. Commercial heart rate monitors are also available, consisting of a chest strap with electrodes. The signal is transmitted to a wrist receiver for display. Heart rate monitors allow accurate measurements to be taken continuously and can be used during exercise when manual measurement would be difficult or impossible (such as when the hands are being used).
The most accurate way of measuring HRmax for an individual is via a cardiac stress test. In such a test, the subject exercises while being monitored by an EKG. During the test, the intensity of exercise is periodically increased (if a treadmill is being used, through increase in speed or slope of the treadmill), or until certain changes in heart function are detected in the EKG, at which point the subject is directed to stop. Typical durations of such a test range from 10 to 20 minutes.
Conducting a maximal exercise test can require expensive equipment. If you are just beginning an exercise regimen, you should only perform this test in the presence of medical staff due to risks associated with high heart rates. Instead, people typically use a formula to estimate their individual Maximum Heart Rate.
Formula for HRmax
Various formulas are used to estimate individual Maximum Heart Rates, based on age, but maximum heart rates vary significantly between individuals.
Even within a single elite sports team, such as Olympic rowers in their 20s, maximum heart rates can vary from 160 to 220. It gained widespread use through being used by Polar Electro in its heart rate monitors,)
These figures are very much averages, and depend greatly on individual physiology and fitness. For example an endurance runner's rates will typically be lower due to the increased size of the heart required to support the exercise, while a sprinter's rates will be higher due to the improved response time and short duration., etc. may each have predicted heart rates of 180 (= 220-Age), but these two people could have actual Max HR 20 beats apart (e.g. 170-190).
Further, note that individuals of the same age, the same training, in the same sport, on the same team, can have actual Max HR 60 bpm apart (160 to 220):
Training regimes sometimes use recovery heart rate as a guide of progress and to spot problems such as overheating or dehydration . After even short periods of hard exercise it can take a long time (about 30 minutes) for the heart rate to drop to rested levels.
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