Fitness CK

The "exercise CK" often mentioned in the fitness field is serum creatine kinase. It is a core biochemical indicator that reflects the degree of muscle micro-damage, but it is by no means the only criterion for judging overtraining or health damage. If ordinary fitness people have no symptoms of discomfort, it is a normal physiological reaction for CK to rise to 3-5 times the reference value after exercise, and there is no need to panic.

Last week, I just picked up a girl with zero foundation in my studio. After two days of "Devil Legs Training" with a friend, her physical examination showed that her CK value was 1287U/L, which is 6 times higher than the upper limit of the reference value for women. She sat at the front desk with the report sheet and shed tears. She said that she read popular science and said that high CK means rhabdomyolysis, and the next step is dialysis for kidney failure. I took the report and looked through it, and saw that she had no other discomfort except for sore legs and shaking when walking down the stairs, so I asked her to buy two bottles of electrolyte water and drink it down. She would eat two more bowls of rice when she got home and rest for 72 hours before checking again. As a result, she came to check yesterday and it had dropped to 230. There was nothing wrong with her.

In fact, regarding the increase in CK after exercise, there have always been two completely different voices in the fitness and sports medicine circles. Scholars engaged in basic research generally believe that the essence of elevated CK is that after muscle fibers are stimulated by external forces, the permeability of the cell membrane increases or micro-damage occurs. CK originally existing in the muscle cells leaks into the blood, causing the value to rise. This micro-damage is the result of excessive muscle recovery. The premise of recovery is that as long as it is not accompanied by symptoms such as persistent severe muscle pain, soy sauce-colored urine, nausea and dizziness, even if it rises to less than 10 times the reference value, it is within a controllable range and does not require medical intervention at all. Rest + replenishing water + supplementing carbohydrates and proteins will bring it down on its own.

Bodybuilding veterans who have been in the gym for more than ten years will not take the small increase in CK seriously at all. Many people will even take the initiative to use the increase in CK after training as a reference to judge whether the training has given enough stimulation. If the CK is not doubled compared to the resting value the next day after doing chest training, it can only mean that the capacity is not stacked enough this time, or the weight is not enough, or the interval between sets is too long, and the amount will have to be increased next week.

Of course, controversy has always existed. Many conservative coaches will require members to stop training as soon as CK exceeds the upper limit of the reference value, and even require members to reduce subsequent training intensity. They feel that as long as CK rises, it is a signal of overtraining, and long-term high load will bring irreversible burden to the kidneys. This statement is not wrong, but it is indeed a bit too cautious - when I was preparing for the competition last year, I arranged heavy deadlifts, leg presses and 40 minutes of fasting aerobics for three consecutive days. My CK at rest reached 3800U/L, and I was shocked at the time. I asked a sports medicine doctor I was familiar with. They saw that I could eat and sleep, and that except for the delayed soreness, it didn’t even affect my ability to walk. They just sent me back, and told me to drink more salt water and not take painkillers blindly. After three days, the reexamination dropped to over 700, and there was no problem at all.

But that doesn’t mean you don’t need to worry about high CK. If it is more than 15 times the reference value and is accompanied by the discomfort symptoms mentioned above, then don’t hesitate and go to the hospital directly. If rhabdomyolysis is really the case, a large amount of myoglobin blocking the renal tubules will indeed induce acute kidney injury. We don’t need to take this risk. Especially if you are a novice, don’t get too excited and follow the master to do 10 sets of deadlifts and 10 sets of squats on the first day in the gym. Muscle endurance is already poor, and if you catch up with the state of not warming up, being dehydrated, and staying up late the day before, it is really easy to cause problems.

To put it bluntly, CK is like your weekly test scores when you were in school. A high score means that you have studied hard during this period. It is okay if you exceed the target a little. If you get some sleep and eat well, you will get better. If you really feel uncomfortable after getting an outrageous score, it is not too late to see a doctor. Don't be scared by an indicator and don't dare to train, and don't be stubborn and ignore the signals given by your body. Fitness is a process of dialogue with your body. There are not so many black and white standards.