Exercise broadly divides into aerobic and strength training. Aerobic exercise, such as walking and cycling, boosts cardiorespiratory function, while resistance training builds muscle. Both are necessary, but middle-aged people should pay particular attention to strength training. The reason is simple: it is a period when the rate of muscle loss accelerates.
According to the medical community on Wednesday, when a person does not exercise, muscle declines by 1% each year starting in their 30s, falling to about 3% each year from their 60s. By the 80s, only about half the muscle of someone in their 30s remains. In the 70s, muscle mass drops by about 30% compared to the 30s and 40s, but because fat fills the space left by lost muscle and body weight is maintained, many people fail to notice the decline. In 2017, the World Health Organization (WHO) classified muscle loss not as a phenomenon of aging but as a separate disease, assigning the diagnostic code for "sarcopenia," and Korea took the same measure in 2021.
Muscle loss is not simply a matter of losing strength. When muscle declines, the ability to process blood sugar in response to insulin drops markedly, raising the risk of diabetes, and it is also linked to the incidence of cardiovascular disease, heart failure, and cancer. According to the Korea National Health and Nutrition Examination Survey, the domestic prevalence of sarcopenia was 6.6% in men and 9.2% in women.
So how much is enough? A paper published this June in the British Journal of Sports Medicine by a research team at Harvard University's T.H. Chan School of Public Health provided a concrete answer. After tracking about 147,000 Americans over 30 years, the group that performed strength training for 90 to 119 minutes per week had 13% lower overall mortality, 19% lower cardiovascular disease mortality, and 27% lower neurological disease mortality compared with the group that did not exercise. Exceeding 120 minutes per week produced no additional health benefits. Applied to real life, this standard suggests a reasonable approach of three to four times a week, spread out at around 30 minutes per session. Mortality was lowest when strength training and aerobic exercise were combined.
This study was based on Americans. It is difficult to apply the figures directly to Koreans, who differ in body type and basic fitness. What matters is that the "ceiling" on exercise volume is lower than expected. With strength training, doing more does not necessarily produce proportionally greater effects.
When designing strength training, three factors must be combined: intensity, frequency, and sets and repetitions. Intensity refers to how much weight is handled, frequency to how often one trains, and sets and reps to how many repetitions are divided up with rest in between. Even when doing the same 30 repetitions, dividing them into two sets of 15 with rest is often more beneficial to the muscle than doing them all at once. In particular, middle-aged people with high blood pressure or cardiovascular problems should check their underlying condition before setting the intensity.
Whether to continue when pain is felt is also a frequently asked question. The muscle soreness that comes after exercise (delayed-onset muscle soreness) is a product of micro-damage to muscle fibers and the recovery process, and is to some extent unavoidable. However, if the stiffness persists into the next day or there is an abnormal sensation, it is better to rest. Muscle does not grow during exercise. Recovery and growth occur only after exercise has provided stimulation and sufficient rest is taken. Pushing through pain only lengthens the recovery period and raises the risk of injury.
As important as exercise is protein intake. The general recommendation is that 1.2 to 1.6 grams of protein per kilogram of body weight is needed. One egg contains about 6 grams of protein, 200 grams of tofu about 20 grams, and 100 grams of chicken breast and a piece of mackerel are at similar levels. Animal protein has a high absorption rate, but consuming it together with plant protein is better for balance. Rather than eating protein all in one meal, spreading it evenly across three meals improves absorption efficiency. Protein supplements are sufficient when used only as a supplementary means when it is difficult to meet intake through natural foods.
The right time to prevent sarcopenia is not old age, 65 and older. According to studies, the point at which changes in strength and physical performance begin is age 50. Since physical ability slowly begins to decline starting at 50, it is important to become aware of resistance training from this period. Strength training in middle age is not about improving athletic performance, but an investment to protect daily life in old age. Since excessive exercise is not the goal, maintaining a sustainable intensity and frequency is key.
