A player gets physically and mentally tired during a Tennis Live Arena match like in a career mode match. (see Why are the bars of my tennis player diminishing?) However, at the end of a match, a player recovers a few percent of his physical and mental bars’ maximal values. Apart from the matches, these bars refill with time at a rate of 1 point every 30 seconds. If you want to speed it up, you can fill the bars by using Tokens or consumables.