For strength, I would suggest pushups. Probably the best exercise anyone can do, ever. Don't push off the hands though, get yourself a something like that:
http://www.amazon.com/GoFit-GF-PUB-Push ... B0007W2FLS
...this will prevent any wrist injuries that you may incur while doing advanced pushups and will give you a bit deeper stretch. Not sure how many standard pushups you can do, but if you can comfortable cross 10 x 3 then you need to challenge yourself a bit. It is important to keep form while doing any exercise and concentrate on contracting the muscle you are working to complete the exercise. Best way to do so while challenging yourself is to slow down the rep, to the point where it becomes hard enough to execute. You can use a chair and raise your legs for a more advanced version that will target slightly upper chest muscles. Moving your arms closer together will transfer the load more to your triceps and moving it further apart will transfer it more to your chest.
You should keep your reps sub 10, around 7-8 preferably while the last one being a "failed" attempt, meaning you struggle and may not complete it or lose your form.
Your begging routine should look like this:
- Jump ropes about 15 minutes
- Pushups 3 x max no more then 10
- Pushups with raised legs 3 x max no more then 10
- Chin ups 4 x max no more then 10
- Lunges with appropriate weight 4 x 8-10
- Ab wheel 4 x max (start from your knees for a few month before moving up to full stand)
Should take about 1.5 hours at most. 1 day of rest is a MUST after each workout.
Everything should be done slowly and deliberately while keeping your form for each exercise. This type of routine will target most muscles you need for tennis. I suggest to stay away from Machines or Free weights in the gym for a good few month. Machines restrict your workout too much to a muscle ground, they are great isolators but not so great for a sport like tennis. Free weights are better, but requires you first to "learn" to keep your form while performing any exercise.
To get stronger for tennis, mostly means to get your core stronger and more balanced. Think about picking up a Yoga routine, this is improve your balance greatly, allowing you to engage more of your muscles into your shots. Stay away from heavy weight lifting, not because you will get slower, but because of an injury risk and lower range of motion on these. Sure, they will make you look better, but there are other exercises that can help you play better tennis. Keep it simple and short. Try to slowly cut rest time as you get more advanced with the routine, this will give you better results with less time spent. Avoid "adding" more exercises. Once you are able to complete the routine with almost zero rest between each set - time to split the muscle groups into different days. If you get there I will be glad to help.
Level 13 Edberg and counting...