It is generally believed that the sports level and endurance of a professional athlete at the age of 45 are significantly lower than those at the age of 30. but the result of a marathon between retired and serving professional footballers was that there was no difference between 45-year-old retired footballers and 30-year-old serving players. 
Marathon can not fully reflect the endurance and sports level of football players
 it is wrong to think that the sports level and endurance of a professional player will be significantly reduced by the age of 45.