Alright, i've been exercising for tennis for a while and my endurance exercise generally consists of me doing suicides on my drive way which is on a slight incline. I go up and down twice and that is 1 lap. I used to do 5,3,2 laps with breaks in between and a 2 minute break at the end before repeating. I did it 3 times. Today I did 6 laps (took a 35 second break) then 4 laps (took a 25 second break) and then 2 laps. After the 2 laps I rested for 2 minutes and repeated the process 2 more times. I was pretty tired at the end and my heart was racing, can someone tell me if this is bad shape for a tennis player that wants to play singles to be in and if so what I can do to get into better shape? Thank you.