Planning to run the Honolulu Marathon on Dec. 10, but your longest run still has not cracked the double-digit mile mark?

Want to join an adult soccer league, even though most of your exercise comes from scooting around in the office coaster chair?

Think it would be fun to play dodge ball for the first time since, well, the third grade?

Warning: You may be risking shin splints, tendinitis, stress fracture or worse.

Even if you are fit, making sudden, unaccustomed demands on your body is as unwise as sliding head-first into home plate — it is needlessly dangerous. Too many recreational athletes fail to prepare their bodies for their chosen sport, making themselves vulnerable to overuse injuries.

"If you are 30 years old and you throw overhead in a basketball game for two hours, the rotator cuff is seeing a strain it hasn't seen since Ronald Reagan was president," said Dr. John O'Kane, team physician for the University of Washington Huskies.

Conditioning — exercises that build muscle tolerance for specific stress and loads — is crucial for preventing injuries. Every sport, whether bowling or touch football, makes particular demands on the body. Conditioning allows the body to acclimate itself to the tasks by gradually mimicking the sports' actual motions, said O'Kane, associate professor of orthopedics and sports medicine at the University of Washington.

"The Mariners don't show up on the first day of the season and just start throwing at 90 miles an hour," he said. "They go to spring training."

REC JOCKS HAZARDS

Staying physically active undisputedly lowers your chances of developing certain diseases and dying prematurely. But playing recreational sports, particularly competitive team sports such as basketball, also carries risks of injury.

Jennifer Lesko, director of Therapeutic Associates-Queen Anne Physical Therapy in Seattle, said "quite a few" of her patients are otherwise fit and healthy people who injure themselves playing sports after work or on the weekends. She said people mistakenly use regular gym workouts as all-purpose training for their sports, regardless of whether they involve kicking, throwing or hitting.

So a player who hasn't done a single rotational movement exercise and then pitches six innings in a softball game is an injury waiting to happen.

"It's not that they're weak. It's just that those specific muscles are weak," Lesko said.

A German study published this year in the British Journal of Sports Medicine found that out of 7,124 adult Germans who regularly played recreational sports, 5.6 percent got hurt seriously enough during the previous year to require medical attention.

In 1993, researchers at the Center for Sports Medicine at Saint Francis Memorial Hospital in San Francisco tracked 986 volunteers for three months in one of the more comprehensive studies to consistently compare the injury rate of various fitness activities. Close to half of the participants, or 475 people, reported an injury, ranging from "ache-pain" that did not hinder play to contusions and fractures. Team sports had the highest injury rates; running was close behind. Walking and riding stationary bikes were the safest activities.

The most common injury sites were the ankle, knee, back and arm. The fittest and most active people suffered up to four times as many musculoskeletal injuries as more sedentary and less-fit people. The researchers theorized that the former group was at greater risk because they played longer, harder and more frequently. The study appeared in the American Journal of Epidemiology.

CUSTOM CONDITIONING

Even favorites such as dodge ball and kickball, which can seem deceptively safe, can cause trouble for the unconditioned. Just ask Noelle Smithhart.

Smithhart, 26, played kickball for three seasons in the Underdog Sports Leagues, a Seattle company that attracts people interested more in recreational fun than in athletic feats. She did almost no exercises to prepare for kickball, which requires punctuating long stretches of idle standing with bursts of sprinting. Her sole exceptions were occasional yoga and stationary stretching just before games.

The point of playing kickball "is just like it was in elementary school, running around and having fun," said Smithhart, a real-estate marketer. "Kickball is the exercise."

But during her first chilly evening game, Smithhart pulled a hamstring. Then she injured it again at another kickball game.

Smithhart ideally should have begun conditioning exercises for kickball two or three months before the season began, said Dr. Ben Kibler, medical director for Lexington Clinic Sports Medicine Center in Lexington, Ky. Kibler has done studies on how sport-specific conditioning can help improve games and reduce chances of injury.

Kickball requires flexibility, quickness and agility. Doing 10-yard sprints would be a good way to prepare for kickball's stop-and-start style, Kibler said. Kicking sports also demand a balance between the front and back muscles in the legs, as opposed to muscle balance between left and right legs as in running, he said.

O'Kane of the University of Washington said poor muscle coordination makes you more prone to injury. For a throwing sport such as baseball or basketball, O'Kane recommends targeting the muscles that control the shoulder blades and the rotator cuff (muscles and tendons that form a "cuff" over the shoulder) for two or three months beforehand. Pairing push-ups and lateral pull-downs would be one example. Follow the exercises for two or three weeks, then start making easy throws and increase the intensity over six weeks. After that, you'd be good to go.