The big guy who steps up to the plate in slow-pitch softball may think he's getting more exercise than the two little old ladies in tennis shoes who stride up his street every day. But move over, shortstop - the grannies are actually getting a better workout.

Different activities have different benefits and risks, of course, and burn calories at different rates. The more aerobic activities - those that increase the heart's ability to pump - offer obvious conditioning benefits.

But don't be discouraged if you like a sport that's low in aerobic or caloric benefits. Though a bowler might split a pizza and a pitcher after the game, consuming more calories than she has burned, she does benefit from just doing something. Remember: Studies indicate that a well-conditioned 60-year-old who works at staying in shape has the same physiology as a 20-year-old couch potato.

Here are the relative merits of activities you might be involved in this summer

SWIMMING

The crawl burns between 10.6 and 12.9 calories per minute. Treading water requires five calories per minute, while the backstroke burns 14 calories per minute. Obviously, the workout varies with the skill level. Mark Spitz, who won seven Olympic gold medals, could swim all day. But a less graceful swimmer, splashing and puffing, gets an anaerobic workout with just a couple of laps.

Benefits: Involves little weight-bearing. Improves flexibility in people who have little, such as arthritis sufferers. Few injuries. But again, swimmers should work up to swimming 20 minutes at a time two or three times a week.

Disadvantage: You need a pool.

SOCCER

This is a rapidly growing sport that suits players of all sizes. 176-pound man would burn 10.9 calories for every minute of nonstop soccer action.

Benefits: Strong aerobic component if played well. Develops lower limb muscles.

Risks: Thanks to sliding tackles and heading, injuries are many. Weekend warriors lack conditioning; conditioned athletes get overuse injuries.

LACROSSE

Baltimore's beloved sport is both anaerobic and aerobic, yet produces fewer injuries than, say, soccer and football.

Benefits: Develops strong quadriceps - well-defined upper legs from running up and down the field and sprinting during fast breaks. The upper body has to be strong, too, especially the wrists, to pass the ball quickly. To pass and catch requires fine motor skills.

Risks: For some reason, female players, especially in high school, seem prone to torn anterior cruciate ligaments in knees.

BIKING

Biking is an excellent form of exercise, one that increases cardiovascular efficiency. It should be done for at least 20 minutes, two to three times a week. A 176-pound man, riding at a leisurely 5.5 mph, would burn 5.1 calories per minutes. Riding at 9.4 mph would burn 8 calories per minutes, while a racing biker burns 13.5 calories per minute.

Benefits: Puts less strain on weight-bearing joints, and injuries are rare. Develops lower body muscles. And it can give you "runner's high."

Risks: Serious bikers are prone to overuse injuries, like shoulder problems and back strain. The iliotibial band, a thick band of tendon that runs from hip to knee, can get irritated and tight.

GOLF (walking and carrying clubs)

A six-hour round of golf involves more waiting than exercise. "An individual playing twice a week is not going to get in shape," says Lew Lyon, director of the Good Health Center at Good Samaritan Hospital in Baltimore.

Benefits: Relaxation - if people don't get frustrated with their game. Bending over to pick up the ball works the extenders in the back.

Risks: Your swing can cause back problems. Make sure your back and abdominal muscles are in shape.

DUCKPIN BOWLING

Bowling has no aerobic benefits, but it offers recreational value for the older person who may do nothing else.

Benefits: Increases flexibility in the shoulder girdle, upper back, pelvis, hip and trunk. Trunk muscles are strengthened, and back extenders get a good workout.

Risks: Short of smacking your fingers between balls, there is little injury risk. It can be undertaken by just about anyone, and usually is relaxing - unless you have a bad split.

HORSEBACK RIDING

Horseback riders are some of the strongest athletes around.

Benefits: Requires certain well-developed muscles, and anyone who has ridden a horse will remember what those muscles are - inner thigh and trunk.

Risks: Falls can cause broken ribs and wrists, paralysis and even death.

SOFTBALL (slow-pitch)

Nobody is going to say softball is highly aerobic; there's too much waiting around. What little exercise it provides usually occurs when running to base.

Benefits: "It gives Americans a chance to be moderately active without getting in shape," says John Lopez, director of the Towson Sports Medicine and Rehabilitation Center. And it offers esprit de corps appeal.

Risks: Lots of injuries - shoulders, elbows, hamstrings, knees, ankles, collision injuries. And softball players, unlike baseball players who ice an injured arm, tend to treat injuries by applying a cold beer - to their lips.

WALKING

"This is the best activity that anyone can participate in," says Lew Lyon of Good Samaritan Hospital. Lopez agrees. A walker moving at a normal pace burns between 6.2 and 6.6 calories per minute of walking.

Benefits: Increases metabolism and circulation without putting undue stress on the body. Unlike joggers, walkers don't compound the effects of the forces of gravity when their feet strike the pavement, creating problems for knees, ankles and hips. Also, to jog a mile might take eight minutes, while walking that mile might mean exercising for 14 to 16 minutes - and, remember, the key to exercising is to do it for at least 20 continuous minutes.

Risks: Next to none, but walk, don't stroll, and do it at least two to three times a week and for 20 minutes. So tell Fido he simply cannot stop at every bush and fire hydrant in the neighborhood.

TENNIS

An average player burns 8.7 calories per minute, but "If you're a really good player, you'll get a tremendous workout," Lopez says. "If you're not very good, you will spend the time chasing the ball and missing the ball."

Benefits: Helps the overall body, developing muscles in the legs, upper body, abdomen and shoulder girdle. Can be played even into your 80s.

Risks: Tendinitis, bursitis and overuse injuries - "Even a little thing like changing strings can do it," says Lyon. Lopez adds that a racket with a wrong-size grip or an improper backhand can result in "tennis elbow."

BASKETBALL

A full-court pickup game burns 11 calories per minute. It's anaerobic and aerobic.

Benefits: Conditions upper and lower body; improves ability to run and jump.

Risks: You must be in shape or risk torn hamstrings and back problems. Basketball is a leader in sprained ankles and "jumper's knee," soreness under the kneecap. One of the worst injuries is a tear to the anterior cruciate ligament in the knee, which requires surgical reconstruction. ACL injuries occur when a player stops suddenly and his or her shoes grip the hard court. Someone who is playing pickup basketball a couple times a week is in good shape, but, unfortunately, basketball isn't something that can be played later in life.

Calories, where available, are from "Nutrition, Weight Control and Exercise" by Frank I. Katch and William D. McArdle

Pub Date: 5/10/98