What causes shin splints?
—E. BACHMAN, AUSTIN, TEX.
Claude T. Moorman III, director of sports medicine at Duke University Medical Center, offers an answer:
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“Shin splints,” the layman’s term for the painful sensations felt at the front of the shinbone (tibia) after exercise, occur when the constant pounding and stresses placed on the muscles, bones and joints overwhelm the body’s natural ability to repair damage and restore itself. We commonly see shin splints in athletes, military recruits and even in middle-aged weekend warriors, especially at the beginning of milder weather.
Overworked muscles are one major source of the aches. The muscles that connect the tibia to the ankle are held together by fascia—a tough, inelastic covering like a sausage skin. When the muscles naturally expand as a result of exercise, the resulting pressure can cut off blood flow, causing pain. This form of shin splints, known as exertional compartment syndrome, appears in athletes who play field sports such as soccer or who often run on hard surfaces.
Pain can also stem from injuries to the bone, ranging from stress reactions to full-blown fractures. The continual pounding endured during running, for example, can cause many microscopic cracks to develop in leg bones. Normally, with rest, the body easily fixes the tiny fissures. Without sufficient mending time, however, they can coalesce into a stress fracture—a hairline crack—or even a complete fracture, in which the bone breaks all the way through.
People can prevent shin splints by simply adding extra arch support to shoes to redistribute weight or changing to softer running surfaces. Doctors also recommend “active rest,” which means that a runner, for instance, should take up swimming or biking for a while. The change of pace gives the affected areas time to heal but maintains the cardiovascular benefits of exercise.
Warming up muscles before exercise to prevent injuries is a controversial subject, with smart people on both sides arguing for and against it. We at Duke, based on research conducted at the university, recommend a slow warm-up period. We believe that about 10 minutes of graduated activity is the best way to prepare the body for working out more strenuously. For shin splints, as with most things in life, moderation appears to be the best medicine.
Why do bees buzz?
—M. O’MALLEY, NEWTON, MASS.
Gard W. Otis, a professor of environmental biology at the University of Guelph in Ontario who studies bee behavior, ecology and evolution, explains:
Bees produce their distinctive “zzzz” in two ways. First, their wing beats create wind pulses that people hear as a buzz. This sound is not exclusive to bees—most flying insects produce a similar hum. The pitch of the sound produced is a function of the flapping rate: the faster the wings, the higher the pitch.
Second, some bees, most commonly bumblebees (genus Bombus), vibrate their wing muscles and thorax (the middle segment of their body) while visiting flowers. These movements make the pollen fall off the flower’s anthers onto the insect’s body. Some of that pollen gets deposited when the bee alights on the next bloom, resulting in pollination. The bee also grooms pollen onto basketlike structures on its hind legs, taking it back to the nest to feed to the larvae.
When bumblebees vibrate blossoms to release pollen, the noise is quite loud. Honeybees (genus Apis) are incapable of such “buzz pollination” and are usually quiet when foraging. Some plants are adapted to buzz pollination: Tomatoes, green peppers and blueberries all store pollen inside tubular anthers. When the bee shakes the flower, the pollen falls out. Consequently, bumblebees pollinate these crops much more efficiently than honeybees do.
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