A lot of people think tennis requires the energy of, say, a hot hand of canasta. To judge from the way some of our friends play, they might as well be at the card table. But even the young, frisky and supposedly well-conditioned tennis player can profit from a specific training regimen for tennis.

Tennis conditioning does two things: It raises your general stamina so you're not seeing double in the third set on a hot day, and it increases strength in specific areas so you can hit certain shots with greater confidence and control, even when tired.

Though you may have jogged three miles a day all winter long, there are other things you can do to enhance your tennis conditioning greatly. Unlike running, tennis is a game of quick starts and stops, which put great pressure on the heart and lungs in short bursts.

First, be sure to do the usual stretching and loosening exercises. Tennis requires so much running and jumping on one's toes that the calf muscles and Achilles tendons become very tight. Spend at least two minutes every day leaning against a wall, a fence or a tree with your feet flat on the ground. Do body bends for your back. Loosen your shoulders before hitting serves or overheads.

Jumping rope is a good aerobic conditioner for tennis players. Five uninterrupted minutes with the rope is the equivalent of about one mile's jogging, and it also makes you lighter on your toes.

For the quick spurts that will save critical points, however, you need some "interval" training - short sprints. You can practice on the open road by sprinting 15 yards, then walking 15, over and over for about five minutes.

But this is tennis, and it's more fun to train on the playing field of our sport. Take six old tennis balls, and put three of them on the sideline at net and the others on the sideline where it meets the service line. If your partner is along, he or she should do the same thing on the other side of the court.

Line up at the baseline. On "go," sprint to the net, pick up one ball, sprint back to the baseline and set it down. Then run to the service line, bring one ball back to the baseline. Continue the race until you have moved all six balls to the baseline. A very quick tennis player can complete this exercise in 30 seconds. Then fall over and expire.

Q - Should a woman work out with weights to increase her arm strength?

A - If you're serious about your game, yes. The great Margaret Smith Court credited her power and endurance to a weight-training program. Many health spas have weights you can use. As a woman, however, you should stress repetitions rather than total weight.

Q - I have a two-handed backhand, but I want to be able to volley with one hand. My arm is so weak I can't keep the racket head up.

A - If you have access to a Nautilus training center, the trainer can show you how to work on the specific muscles used to hit a backhand. Otherwise go to a gym with pulley weights and do 30 repetitions imitating a backhand volley.

Q - Is it a good thing to ride a bicycle to the tennis courts?

A - Yes, if you don't arrive too exhausted to play. Bicycling is a very strenuous activity in itself and great for overall conditioning, but it could make you weak-kneed for the first 10 minutes on court.

Q - How do I know if I'm in good enough shape to play in a midsummer tournament?

A - By playing under similar conditions now against a top rival. Play in the midday heat. If you can go the full distance - three sets with no breaks - you are physically and mentally ready for the tourneys. CAPTION: Picture, A GAME OF QUICK STOPS AND FAST STARTS.