Some questions on sport activities.

I am taking tennis course this summer. I found out that serving is a difficult task. you serve, you have to strike the ball into the front-court box. And it is very hard to do it when you want to make your ball goes fast. I also feel that it is difficult to play with another one. I feel I am better at one-on-one. And before I attended my tennis course yesterday, I did some AB-wheel excercise. This excercise really helped me that it had the flow of energy in my arms going smoothly. So I did well in my tennis course last night. Speaking of being playing tennis, do you really need to have certain ability of the strength of your arms--no matter how good or how skilled you are?

Also that I feel playing basketball is quite hard. I felt holding ball which was barely. We shoot the ball into the bucket, we must be relax and let our muscles be loose. During the process of shooting and releasing ball into the mid-air, there is a crucial time to put all of your energy into it in order to make it accurate. But since just by holding ball without any movement is so tired, does that mean we need certain amount of energy in our arms to play it well?