Correcting Myths about Fat Loss and Physiological Monitoring: Limitations of Sit-ups, Precise Application of Morning Pulse Measurement and Target Heart Rate
Many people do sit-ups like crazy every day in an attempt to lose belly fat. However, sit-ups are not an ideal exercise for weight loss. First, sit-ups are high-intensity, short-duration exercises, a typical anaerobic metabolic process. Fat mobilization and utilization require a complex series of hormones and enzymes, and the mobilization rate is significantly slower than glycogen. It's very likely that the exercise will end before fat is even mobilized. Second, the human body's blood circulation is systemic, and the "proximity principle" for fat mobilization is incorrect. The fatty acids consumed by skeletal muscle come from the blood, and the fatty acids in the blood are released by adipose tissue throughout the body.
Even when abdominal muscles are contracting, the energy they burn doesn't specifically come from the abdominal fat covering them. Only moderate-intensity, long-duration, whole-body aerobic exercise can achieve abdominal fat reduction through overall body fat burning. Localized muscle exercises primarily increase muscle strength and size, with very limited effect on eliminating localized fat deposits. Excessive sit-ups can even lead to an increase in waist circumference due to hypertrophy of fast-twitch muscle fibers.
During exercise-based weight loss, real-time monitoring of physiological status is crucial. Morning pulse (the pulse upon waking in the morning) is a key indicator. No food or physical activity should be performed before measuring the morning pulse. A gradually slowing morning pulse is a sign that the cardiovascular system is responding well to exercise. For severely obese individuals, a significant slowing of the morning pulse after two weeks of exercise is often due to reduced fat accumulation around the heart, improving ventricular diastolic function and increasing stroke volume. If the morning pulse is more than 10% faster than usual, without any underlying cause such as a cold or fever, it indicates that the previous day's exercise load was too high, and fatigue has not yet subsided; the exercise intensity should be reduced promptly.
Determining the appropriate exercise intensity, or "target heart rate," is the cornerstone of successful weight loss. Currently, two common calculation methods exist. One is the "maximum heart rate method": Maximum heart rate = 220 - age, with the target heart rate range set at 50%–60% of maximum heart rate. The second, and more recommended, is the "heart rate reserve method": Heart rate reserve = Maximum heart rate - Resting heart rate. The lower limit of the target heart rate = Heart rate reserve × 20% + Resting heart rate; the upper limit = Heart rate reserve × 40% + Resting heart rate. This method takes into account individual differences in resting heart rate and is more targeted.
Studies suggest that the ideal exercise intensity for obese individuals trying to lose weight is generally between 20% and 40% of their resting heart rate plus their heart rate reserve. Target heart rate not only ensures that fat contributes to energy production to the maximum extent but also serves as a crucial safety barrier. Obese individuals generally have lower exercise capacity than those of normal weight; blindly adopting the intensity of exercise for normal individuals would significantly increase the risks. By controlling exercise intensity through target heart rate, obese individuals with poor cardiovascular function can maintain a sufficiently long exercise duration without developing lactic acid buildup.
It's important to note that as weight loss progresses, a person's physical functions improve, and their heart rate will decrease under the same workload. If the target heart rate isn't adjusted promptly, the exercise intensity will be substantially reduced, leading to poorer weight loss results. Therefore, resting heart rate should be reassessed and the target heart rate range adjusted periodically (usually every two weeks) to ensure the exercise program consistently operates within the "high-efficiency zone."