It's a common sight in the summertime; children bouncing up and down on trampolines in the backyard.

But as the weather heats up, a group of doctors is warning that these contraptions can be dangerous to kids.

According to the American Academy of Orthopedic Surgeons (AAOS), the number of Americans treated in hospitals each year for trampoline-related injuries is now 100,000 -- triple what it was in 1991. Most of those hurt are children younger than 14.

Some trampoline injuries are so violent they resemble those suffered in car or motorcycle accidents.

Sprains and fractures are common, and severe injuries can interfere with growth or cause paralysis or death: It's worse than just a broken wrist or a bump on the knee.

Swimming pools we fence off and restrict, but trampolines are in everyone's backyard.

Trampoline accidents can occur when someone falls off or through the mat, hits the rim or lands badly while attempting somersaults or other maneuvers.

Especially dangerous is the practice of two or more children jumping on a trampoline at the same time.

When that happens, it is usually the smaller child who gets hurt, either colliding with the other participant or being hit by an upward-moving mat.

The little guy always loses in these collisions.

In keeping with its ongoing "Prevent Injuries America" campaign, the AAOS has issued a statement called "Trampolines and Trampoline Safety." Among the academy's recommendations:

Careful adult supervision at all times. Children should never use the trampoline unsupervised.

Only one person should use the trampoline at a time.

Spotters should be present when the trampoline is in use.

Somersaults and other high-risk maneuvers should not be attempted without a safety harness.

The trampoline jumping surface should be placed at ground level, and the supporting bars and strings should have protective padding.

The American Academy of Pediatrics has also issued a statement, calling home use of trampolines "extremely unwise" and asking pediatricians to advise parents "never to purchase a home trampoline or allow children to use home trampolines."

Parents must recognize the risk of injury. Even with precautions, kids can never be totally safe on trampolines, and there are little data to prove that safety equipment such as nets and padding actually reduces injuries.

American Academy of Orthopedic Surgeons Press Release

Dr. Mercola's Comments:

Exercise is great and it is even better when you have fun. Trampolines can certainly contribute to that, but my concern is that many parents may not be familiar with the potential dangers of trampolines. If you have one, or know someone who does, you might want to pass along these recommendations. For exercise, I do find trampolines one of the better forms of exercise and it is superb for stimulating drainage of the lymphatics. However, the personal trampolines are far preferred, but one must obtain a high quality one that costs around $200 (800-497-9516). The inexpensive $20 ones don't last more than several weeks before they break down. I have been using one as an adjunct to my exercise program for the last several years and find it quite helpful.