Tennis is an all encompassing game – at least when it comes to the muscle groups you utilize to effectively play the sport!
Starting at your feet and ending with your hands, you use your entire body with every move in Tennis. In fact, something called the kinetic chain begins in your feet when you go to run, jump, or shuffle on the court. The energy created here passes from the first link in the chain (your feet) to the other major muscle segments of your body that make up the remaining links: lower legs, upper legs, hips, trunk, shoulders, upper arms, forearms, and finally hands.
Your major lower-body muscles start with your calves, specifically the gastrocnemius and soleus muscles. Next are your upper legs where your hamstrings (along the back of your thighs) and your quads (along the front of your thighs) are most engaged. Finally the gluteus maximus muscles are utilized.
The major trunk muscles are essential to giving power to your play as well as keeping you safe from injury. These start with the abdominal muscles consisting of the rectus abdominis that span from your ribs to your pubic bone. In addition are the transverse abdominis which wrap around the sides of your mid section like a security belt. Obliques on your sides and erector spinae along your spine are essential to keeping you balanced and secure. Further are the latissimus dorsi muscles which are the largest muscles in your back and they work together with all the other muscles to give you power and strength.
As for your upper-body muscles, the links include chest, shoulders, upper back, and arms. As you probably guessed, the pectorals are the main muscles activated in your chest. In your shoulders, you engage the deltoids and rotator cuff muscles that support your shoulder joint. The rhomoid and trapezius muscles are the main muscles used in the upper back and the biceps and triceps are essentially used in the upper arms.
Lastly come the flexor and extensor muscles in your forearms and ultimately the hands!