In tennis you need explosiveness, strength, balance, stamina, speed and agility. The movements you do on the tennis court are short and fast, so you are using a lot of anaerobic energy. But because you stay on the court for hours, you need a good aerobic endurance as well. Running stairs is a great activity that can give you tremendous results in your tennis fitness training. Running stairs is extremely effective in increasing your endurance and building your lower body strength. And if you want to add the balance and agility element into your stair training, you can do different variations of lunges and jumps, described below.