Does training well and staying in good shape help to prevent the covid-19 infection?

Maintaining overall good health, which includes regular physical exercise, a balanced diet, and getting enough sleep, is important for supporting your immune system. A strong immune system is vital in helping your body respond effectively to infections, including viruses like SARS-CoV-2, which causes COVID-19.

However, it's important to understand that while good physical health can potentially lessen the severity of symptoms if you do get infected, it does not guarantee prevention against COVID-19. Even very fit and healthy people can still contract and spread the virus. The immune system's response to a novel pathogen like SARS-CoV-2 can vary greatly among individuals and depends on many factors, including age and genetics, not just overall health and fitness.

The most effective measures to prevent COVID-19 infection are:

Getting vaccinated: COVID-19 vaccines have proven to be highly effective at preventing severe disease, hospitalization, and death. They also reduce the risk of getting infected and transmitting the virus to others.
Following public health guidelines: This includes wearing masks in certain settings, practicing good hand hygiene, maintaining physical distance from others in high-risk situations (especially in indoor or crowded places), and avoiding close contact with people who are sick.
Regular testing: If you have symptoms of COVID-19 or have been in close contact with someone who has tested positive, get tested.

Remember that recommendations may evolve as the situation changes and as new research becomes available.