It's that time of year: Kids hit the sports fields running, and often hobble back off. Back to school means back to organized sports for more than 30 million children and teenagers — and roughly 2.5 million emergency-room visits during the year for resulting injuries.

Fortunately, catastrophic ones are rare. University of North Carolina scientists tracked 22 years of high school sports to conclude that about one student athlete out of every 100,000 players suffers a severe, occasionally fatal, injury or illness.

Still, high on the worry list for August and September are heat-related illnesses like the one that killed a Virginia high school football player last week — a tragedy that specialists say is preventable if coaches and players follow proper precautions about limiting workouts on hot, humid days and keeping well hydrated.

Much, much more common, especially in the fall: Too many kids got out of shape during the summer, meaning they're jumping back into practice with weakened muscles. That's a recipe for muscle strains, sprained joints and bone fractures that can sideline an athlete for weeks, more if they don't get the right care.

"This is a time when we get a lot of kids coming into our offices with injuries," says Dr. Pietro Tonino, sports medicine director at Loyola University Health System.

"You hear this from parents all the time: They can't get the kid to mow the grass, shovel snow, take out the trash. All those things years ago helped prepare us for the sports season," adds Brian Robinson of the National Athletic Trainers Association, and the head athletic trainer for 1,600 athletes at a suburban Chicago high school.

"If you're going to go out for football in August, you better start getting ready in May."

What if you didn't follow that advice? There's still time to get in shape before winter sports like basketball. But for every sport, specialists say, there are steps that parents, players and coaches still can take to improve the odds of a safe season.

Topping that list: Every child and teen needs a physical exam every year — even if the school doesn't require one — to be sure they're fit to play organized sports.

A good exam can highlight strengths and weaknesses that might make one sport a better fit than another.

It also may turn up warning signs of serious problems, such as whether a player is at risk for heartbeat irregularities that can cause sudden cardiac arrest — a very rare occurrence, but one that NATA warns is a leading cause of death in young athletes. Tonino says a good physician will ask whether a family member died young of a heart condition, and if the player has ever had a heart murmur or fainting episodes. Any of those could warrant a more in-depth exam to rule out heart problems.

Then comes proper conditioning. That means more than working up to intense practices. If the abdominal and thigh muscles aren't strong enough — known as "core strength" — then players of any sport overuse their other muscles, leading to strains, sprains and fractures, Tonino explains.

A common one is nicknamed Little League shoulder, where young baseball players get tiny fractures of the growth plate near the shoulder because they didn't have proper support for their throwing arm.

Another is the notoriously painful torn knee ligament called the ACL, or anterior cruciate ligament, common in any sport with a lot of twisting, jumping or pivoting — basketball, soccer, football, volleyball, skiing. It's more common in female athletes than males, who tend to bend their knees more as they jump and land, better for shock absorption. Also, females typically have weaker hamstrings, muscles at the back of the thigh that relieve stress on the ACL when the knee bends — something more of that core conditioning can help.

Beyond getting in shape is following the safety rules.

Federal health officials have launched a major campaign to alert coaches that 300,000 people a year suffer a concussion during sports or recreation activities, and that they must come out of the game even if they insist they feel fine. Concussions aren't mere bangs, they're mild brain injuries. If someone gets a repeat concussion before the brain recovers from the first, they can suffer serious brain damage or even die, warns a Centers for Disease Control and Prevention coach alert.

And the NATA is urging coaches to teach high school football players to pay attention to updated rules against "spearing," or headfirst contact. Running into another player with the top of the head, in a chin-down stance, can break the would-be tackler's neck.

It's a hazard that trainers like Robinson too often see from freshmen, the first year that 100-pound teens play together with 250-pounders.

"A lot of these little guys are starting to tackle and diving at people's feet. Those are the kids who are going to end up with head or neck injuries," he said. "Keep your eyes up, see what you're going to hit."