Your question is not very comprehensive, because after fitness, there are many nutrients to be supplemented. Is it vitamin deficiency that needs to be supplemented, or who says it needs to be supplemented? Vitamins are divided into fat-soluble and water-soluble. Fat-soluble vitamins can be stored in the body for a long time, and water-soluble vitamins can be excreted in a few hours according to individual differences, so you can supplement water-soluble vitamins, but water-soluble vitamins will not be stored. So it will take at least two weeks to take effect. There are many ways to supplement. The cheapest way is to go to the drugstore to buy a good deposit or Jin Shi Er Kang, and take it at breakfast or at the nearest training meal. They are all slow-release and can be absorbed slowly.

But please don't forget that there are six kinds of nutrition. It is impossible to supplement vitamins alone. Carbohydrate, protein, fat, water and minerals are indispensable.

Fitness must first understand the meaning of fitness.