Precise Measurement of Exercise Intensity: Target Heart Rate Monitoring, Heart Rate Reserve, and Individualized Safety Limits
Heart rate is the frequency of the heart's periodic mechanical activity, that is, the number of times the heart beats per minute. Heart rate reflects exercise intensity and is the most commonly used and simple indicator for assessing exercise intensity, training level, physical function, and post-exercise recovery ability. Target heart rate, also known as the desired heart rate, refers to the intensity at which the heart is expected to reach and maintain a certain level during exercise. It is generally a heart rate range, expressed in beats per minute; it can also be expressed in beats per 10 seconds.
During exercise, too low an intensity will render the workout ineffective or yield poor results; too high an intensity may cause injury. To achieve optimal exercise results, it is essential to exercise at an appropriate intensity. The heart rate reflected by this expected intensity is called the target heart rate. There are many methods for determining the target heart rate, and two commonly used formulas are currently employed.
The first method is the maximum heart rate method, where a person's maximum heart rate is 220 minus their age. The lower limit of the target heart rate is typically set at 50% of the maximum heart rate, and the upper limit at 60%. For example, a 20-year-old's maximum heart rate is 200 beats per minute, and their target heart rate range is 100 to 120 beats per minute. The second method is the heart rate reserve method, where heart rate reserve is the maximum heart rate minus the resting heart rate. The lower limit of the target heart rate is equal to heart rate reserve multiplied by 20% plus the resting heart rate, and the upper limit is equal to heart rate reserve multiplied by 40% plus the resting heart rate.
For example, a 20-year-old with a resting heart rate of 72 beats per minute has a heart rate reserve (HRR) of 128. This calculates to a lower limit of 97.6 beats per minute and an upper limit of 123.2 beats per minute. Therefore, the target heart rate calculated using the HRR method is between 98 and 123 beats per minute. The target heart rate calculated using the HRR method takes into account the individual's resting heart rate and is more individualized than the result calculated using the maximum heart rate method. Therefore, the HRR method is more recommended for calculating target heart rate. An accurate target heart rate range should be determined through specialized testing at a professional institution using specialized testing methods.
Research shows that the target heart rate for obese patients exercising to lose weight is generally between 20% and 40% of their resting heart rate plus their heart rate reserve. This target heart rate can vary at different stages of exercise for weight loss, requiring repeated testing to determine the optimal range. Knowing the target heart rate allows for targeted exercise, maximizing the effectiveness of weight loss. Furthermore, determining the target heart rate also takes into account the exerciser's physical capacity and workload.
Therefore, target heart rate is also an important measure to ensure safety during exercise for weight loss. Obese patients often have contributing factors to or already have certain chronic diseases. Clearly, the exercise capacity of obese patients is lower than that of normal-weight individuals of the same age and sex. If they adopt the same exercise intensity as normal-weight individuals, not only will they not achieve the best weight loss results, but the presence of chronic diseases may also significantly increase the risks associated with exercise.
Obese patients can control the intensity of their exercise during weight loss by adjusting their target heart rate, thus ensuring safe and effective weight loss. It's important to note that determining the target heart rate requires specialized institutions and professionals to ensure its accuracy. Heart rate reflects not only intensity but also cardiac function. Generally, obese patients who lack physical activity have a faster resting heart rate, indicating poorer cardiac contraction and ejection capacity, and a smaller stroke volume. Severely obese patients, due to fat accumulation around the heart and impaired ventricular diastolic function, experience a further decrease in stroke volume, thus limiting their ability to withstand exercise intensity.