The wind-up and the pitch ... preventing TB... treating heart attacks through MRI... TV's link to fat kids... pinpointing damage in heart attacks... long waits for a liver... daily grind can be bad for baby
Anatomy of a pitch
"Pitcher Mike Mussina winds up for the pitch. Pushing off with his back leg, he generates a significant shear force. He releases the ball, and lands on his right leg with a vertical force of 150 percent of his body weight. What a pitch! It's a good thing that Mike spent the off season strengthening his leg muscles..."
Not your traditional play-by-play, to be sure, but that's just how Hopkins's Edward McFarland might describe the action on the field for the Orioles fans at home.
McFarland, director of sports medicine, measured the forces generated during baseball pitching. Though people tend to focus on pitchers' throwing arms, McFarland concludes that the legs play an important role in the quality of a pitch and bear a large amount of the force generated by a pitch. "A strengthening program shouldn't ignore the lower extremities. Pitchers need to be in good overall fitness," concludes McFarland, who is also a consulting orthopedic surgeon for the Baltimore Orioles.
McFarland studied seven college and high school baseball pitchers. He and his colleagues measured pitching forces using a special instrumented mound containing force plates. The pitchers, he found, pushed off with a force that is 35 percent of their body weight. After releasing the ball, they landed with a force that is 150 percent of their body weight. In contrast, walkers push off with a force equivalent to 20 percent of their body weight, and land with a force that is 110 percent of their body weight.
"A lot of strength coaches and trainers knew this, but did not have the science backing it up," McFarland notes.
The research also may help explain pitching's "fatigue factor," or why pitchers often fatigue late in the game, says McFarland. Part of the problem may be that they lose leg strength--something that could be addressed through weight training.
In addition, McFarland discovered that the more forcefully a pitcher pushed off with his back leg, the faster he moved his wrist when releasing the ball. Faster wrist movement also appears to translate into faster pitches.
But pitchers should avoid overpushing with the back leg, which can jeopardize performance--for example, by decreasing the speed of the pitch and injuring the shoulder. Says McFarland, "Every segment has to be in synchronized rhythm, or it messes up the mechanics."
The segment that appears to be most injury-prone in all baseball players is the shoulder, McFarland concludes following a separate epidemiological study. The orthopedist studied injuries sustained by a Division I college team over three years. During that time, the players reported 277 orthopedic problems. The most common site of injury was the shoulder, mainly from tendonitis, says McFarland, who has also documented similar shoulder injuries in musicians. Pitchers were not the only ones with sore shoulders. Here's the score, by position, for the number of shoulder problems: pitchers 21, infielders 28, and outfielders 14. --Melissa Hendricks
Tuberculosis claims more lives worldwide than any other infectious disease. Patients infected with HIV are especially at risk, and have contributed to a worldwide resurgence of TB. But public health experts hoping to prevent tuberculosis face huge hurdles.
Patients are determined to be at risk for developing active TB when they have a positive purified-protein derivative (PPD) skin test. Until now, the recommended treatment for preventing TB among such patients has entailed a 12-month course of prophylactic drug therapy. However, that is unaffordable and inaccessible in many parts of the world, especially in developing nations, where the majority of TB cases occur.
But now researchers from the Johns Hopkins School of Public Health say they have found cheaper and easier regimens for preventing the disease. In a study involving 750 HIV-infected patients with positive PPD skin tests, the researchers recently demonstrated that a six-month course of the drug isoniazid, or a two-month course of rifampicin and pyrazinamide, prevents TB just as well as the 12-month treatment does.
While both regimens proved effective in preventing TB (just 4-5 percent of patients developed active TB after two and a half years), patients who received the shorter course of treatment were more likely to complete the regimen, the researchers found. They report their findings in the March 14 Lancet.
"This is a great leap forward in finding a way to prevent TB in a lot of people who previously would not have been able to receive appropriate preventive measures," says study co-author Richard Chaisson, associate professor of medicine and international health. He and lead author Neal Halsey, professor of international health, say their findings have prompted the World Health Organization to re-evaluate its current TB prevention policy. --MH
Treating heart attacks through
In promising early studies, Hopkins researchers have shown that a sophisticated version of magnetic resonance imaging (MRI) can precisely measure a chemical in the heart that is tied to the extent of muscle damage from a heart attack.
The scientists believe their noninvasive method can improve methods for determining the location and severity of a heart attack, and ultimately guide doctors in picking the most effective treatment for heart attack patients.
Until now, doctors of heart attack patients have relied primarily on a diagnostic blood test that indirectly measures levels of a chemical called creatine, which helps provide fuel for the heart, explains Hopkins radiologist Paul Bottomley. "If you have a heart attack, cells become leaky, and creatine leaks out." The blood test detects levels of creatine kinase, an enzyme that breaks down creatine.
"But the blood test doesn't tell you where the heart attack occurred, how big it was, or when it happened," says Bottomley.
Using MRI in combination with another technique called magnetic resonance spectroscopy (MRS), Bottomley and Hopkins cardiologist Robert Weiss developed a method for directly pinpointing depleted creatine in injured heart tissue. They first imaged the heart with MRI, then zeroed in to measure creatine concentrations in specific areas using a spectrograph.
"The hope for our tests is that they are a way of determining whether tissue is viable," says Bottomley. "That's important because if tissue is not viable, we know it won't benefit from therapies like bypass surgery and angioplasty."
Bottomley and Weiss tested their technique on 10 heart attack patients and compared those results to tests of 10 healthy volunteers. The scientists were able to observe depleted creatine levels in every former heart attack patient, the team reported in the March 7 Lancet.
In a separate study, associate professor of medicine Joao Lima and his colleagues report that MRI can also be used to predict which patients are at risk of complications following a heart attack.
The researchers used MRI to measure the size of a patient's heart attack and to see whether patients had microvascular obstructions, or blockages in the tiniest blood vessels that deliver blood to the heart. Forty-four patients underwent MRI 10 days after having a heart attack. (Seventeen patients also had an MRI six months after their heart attacks.) Roughly 16 months later, the researchers checked to see which patients had had further heart problems, such as congestive heart failure, stroke, or a subsequent heart attack.
The follow-up study revealed that patients whose MRIs showed the largest heart damage suffered the most post-heart-attack complications over the 16-month period. Moreover, patients whose microvessels had obstructions were five times more likely to have complications than were patients whose capillaries were clear.
"We hope that with more studies, MRI will become routine, a centerpiece for diagnostic imaging of the heart," says Lima.
Both groups of researchers note that their studies involved small numbers of volunteers; further studies using larger numbers of patients are warranted, they say. --MH
Why the tube makes kids
One out of four American children is obese, and television-watching appears to be fueling such childhood obesity. In the March 25 Journal of the American Medical Association, assistant professor of medicine Ross Andersen reports that the more hours of TV a child watches each day, the fatter that child is likely to be.
Andersen based his results on a national survey conducted by the Centers for Disease Control and Prevention of 4,063 children ages 8 through 16.
While the study revealed some good news--80 percent of American children reported exercising vigorously three or more times per week--"there were pockets of concern," notes Andersen. For example, while roughly one-quarter (26 percent) of all American children watch four or more hours of TV a day, the percentage among African American children is much higher--42 percent. Girls also become far more sedentary than boys as they enter adolescence.
Not only are children physically inactive while they watch TV, says Andersen, "they're also inundated with advertisements for junk food. These can become prompts for them to eat. TV becomes associated with eating." In neighborhoods that lack safe play areas and parental supervision, television becomes "an electronic babysitter," he says. "Community leaders and healthcare practitioners need to say, 'Can we offer safe and supervised, low-cost after-school sports and activities?'" --MH
Heart gene therapy begins|
For the first time, cardiologists at Hopkins and collaborators around the country are performing gene therapy directly on the human heart. The new procedure, they say, could one day become a safer, more effective alternative to bypass surgery and angioplasty.
The 125 heart disease patients who will volunteer in the nine-center clinical trial will receive doses of a gene for fibroblast growth factor. Researchers will snake a long thin tube, or catheter, from an artery in one leg up to the coronary artery, and inject a solution containing the fibroblast growth factor gene through the tube. In theory, the heart cells will then absorb the gene and begin pumping out fibroblast growth factor, which will induce the growth of tiny new vessels that will bypass blockages in the arteries. Patients will be closely monitored for side effects that may be caused by this growth factor, which is normally only produced in the embryo.
The Food and Drug Administration approved the protocol for the clinical trial in March. "It's very exciting because [this trial] is the first of its kind," says Jeffrey Rade, an assistant professor of medicine and co-principal investigator of the Hopkins arm of the study. "The FDA has been going very slowly in approving these trials. This field is in its infancy." -- MH
Women, Asian Americans, Hispanic Americans, children, and the elderly wait longer for liver transplants than do men and people of other ethnic and age groups, according to a study by researchers at the Johns Hopkins School of Public Health.
"This paper clearly demonstrates that everything is not the same for every patient," says lead author Ann Klassen. Her group published its findings in the March 5 Medical Care.
To be compatible, a donor liver must have the same blood type as the patient receiving the transplant. But even when Klassen and her colleagues controlled for differences in blood type, they found inequities among groups of people.
The scientists studied 7,422 patient records of those on waiting lists and transplant recipient lists between 1990 and 1992. The records are maintained by the United Network for Organ Sharing (UNOS). What the researchers found:
"It's not that barriers [to receiving a liver] are deliberately put up by malicious design," says Klassen. Rather, the reasons are far more complicated than race or sex discrimination, and "take more thought and planning to fix."
One factor that may limit access is body size, notes liver specialist Andrew Klein. Women and children are smaller than men, and therefore may be eligible for fewer of the available donor livers. "If we put big livers in small people, patients don't do as well," he says.
There are also key issues of access and cost. Patients who are unemployed or destitute have less access to medical specialists and to health insurance, says Klassen. In 1990, private insurance paid for 78 percent of liver transplants; patients without insurance turn to Medicare or Medicaid. While almost all states now cover liver transplants under Medicaid, some states limit coverage to children, or cap payments well below the median cost of a transplant (which was $186,000 in 1992).
Patients with less access to healthcare will be placed on waiting lists at a later stage in their liver disease than patients with better medical care. These people will be sicker, and therefore have a greater chance of dying while waiting for a liver, notes Klassen. In her study, she found that African Americans were almost twice as likely as Caucasian Americans to die while waiting for a liver. Asian Americans also had a higher risk of dying while on the waiting list.
The study's findings regarding foreign nationals merit further investigation, Klassen says. At least some centers appear more eager to take these patients on. Foreign nationals represented just 3.5 percent of waiting list entries overall, she notes; yet at several transplant centers, the proportion of such patients receiving transplants exceeded 20 percent. --MH
Daily physical activities like climbing stairs and walking appear to double the risk that low-income expectant women will deliver their babies prematurely, according to a recent study by School of Public Health researchers. The study involving 1,188 women appeared in the April 1 American Journal of Epidemiology.
By contrast, leisure time activity protected against premature delivery (before 37 weeks). Mothers-to-be who exercised more than 60 days during their first two trimesters had a 50 percent lower risk of pre-term delivery, says lead author Dawn Misra, assistant professor of maternal and child health.
Why the different outcomes? The women who exercise can choose when and whether to be active; they may also be less prone to depression and stress-inducing financial challenges, says Misra.
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