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THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 9 - SEPTEMBER 99


Getting to the Heart of the Softer-Baseball Debate

Softer baseballs are used in an effort to reduce the severity of impact injuries to the brain, face, and heart, but debate on their efficacy, along with hesitance within baseball, has hindered their widespread adoption.

Recent reports on baseball impact injuries bring the issues into sharper clinical focus, including new information about the etiology of commotio cordis and conflicting reports about whether softer baseballs reduce the risk of that event. Another study addresses the risk of eye injuries with softer baseballs (see "Researchers Weigh In on Eye Issues, below).

Lance Van Auken, director of publications and media relations for Little League Baseball, says several models of softer baseballs are approved for play in various Little League divisions. Each local league's board of directors determines which balls the league will use. "We do know that a majority of the very youngest divisions [5- to 8-year-olds] use some type of softer baseballs. However, in the divisions that include players ages 9 to 18, the softer baseballs are rarely used," he says.

New Information on Commotio Cordis

Commotio cordis, sudden death from relatively minor chest wall impact in the absence of structural cardiac injury or abnormality, is rare in sports. Each year two to four commotio cordis deaths are reported in baseball (1). Maron et al (2) recently published information on 70 cases contained in the US Commotio Cordis Registry. The victims were most likely to be boys younger than 16, and the most common sports involved were baseball, softball, and hockey.

In 192021, Link et al (3) narrowed the proposed mechanism of commotio cordis by showing that impacts that occurred 30 to 15 msec before the peak of the T wave produced ventricular fibrillation in young pigs.

In a separate report, Link et al (4) described the high frequency of heart block and ST-segment elevation after resuscitation, which may explain why resuscitation is often difficult in patients with commotio cordis.

Do Softer Baseballs Reduce the Risk of Commotio Cordis?

In 1992, Janda and colleagues (5,6), using a computerized model, anesthetized pigs, and crash test dummies, suggested that softer baseballs did not decrease and perhaps increased the risk of commotio cordis. In their most recent study (7), Janda's group assessed 9 soft-core baseballs as they struck a three-rib biomechanical surrogate at three speeds (40, 50, and 60 mph). A standard Major League baseball served as a control. Janda says the study determined the "viscous criterion" (VC) for each baseball. VC was developed by the automotive industry during crash testing to measure how far and how fast the chest caves in during impact, says Janda, an orthopedic surgeon in Ann Arbor, Michigan, and director of the Institute for Preventative Sports Medicine (ISPM). Baseballs with higher VC values could carry a greater injury risk.

The study found that one of the softer baseballs had a significantly lower VC value than the standard baseball at all three speeds, six had a lower VC at 60 mph, four had a lower VC at 50 mph, and one had a lower VC at 40 mph. One of the softer baseballs had a higher VC at 60 mph. The researchers say the study shows that not all softer baseballs significantly reduce the risk of chest impact injuries. "We also determined that the weight of the ball was critically important," Janda says. The two lightest baseballs were among the group that had a significantly lower VC. (The standard baseball was the fourth lightest baseball.)

In a 1996 review of protective equipment in youth baseball (8), the US Consumer Product Safety Commission (CPSC) analyzed the impact of softer baseballs. The type of baseball involved was recorded in 94% of 88,700 baseball impact injuries recorded in 1995. The CPSC reported that the softer baseballs were involved in fewer and less severe injuries than were the standard baseballs. In its discussion of the apparently contradictory studies (5,6) from Janda's group, the CPSC notes that it commissioned an independent review of the articles by six scientific and medical experts. The reviewers questioned the ability of the biological and biomechanical models to mimic chest impact injuries in children. The CPSC concluded that softer baseballs can reduce the number and severity of youth baseball injuries.

Meanwhile, Link et al (3) also evaluated the effect of softer baseballs as a component of their pig study. They tested three softer balls and a standard Little League baseball on 48 pigs, timing impacts to occur with the up slope of the T wave. Each ball weighed the same and was propelled at 30 mph.

Researchers noted a relationship between baseball hardness and the likelihood of ventricular fibrillation. The lowest risk was for the softest baseball; although a reduced risk of death was seen with medium-soft and least-soft baseballs, the difference did not reach statistical significance. The authors concluded that though the softest baseball may not be practical for competitive play by older youths because of ball performance, it may be useful for T-ball or recreational play.

Link and Janda are critical of each other's studies. Link says that Janda's most recent study (7) deemphasizes the finding that the balls used in T-ball were safer. He also notes that the 192021 Janda study (7) evaluates both weight and softness, which obscures the qualities that make a ball safer. "The data with safety baseballs in both our and Janda's experiments show there is little doubt that safety baseballs will reduce the risk of both cardiac and other injuries in youth baseball," says Link, who is assistant professor of medicine and director of the Cardiovascular Center for the Evaluation of Athletes at New England Medical Center in Boston.

Janda says the 30-mph speed used by the Link group is slower than actual Little League play, particularly when kids are using aluminum or titanium bats. Link counters that his group's latest study (9) yielded the same results using a 40-mph velocity. Janda also notes that his group looked at nine baseball models, whereas Link's group evaluated three.

Link says he is concerned that the public's perception of Janda's studies could lead to underutilization of the softer baseballs, which he believes could increase the risk of sudden death and other injuries.

J.J. Crisco, PhD, research director of the National Operating Committee on Standards for Athletic Equipment (NOCSAE), says part of the problem with interpreting the data about softer baseballs and developing standards for protective equipment is that the dynamics of chest impact injuries are more complicated than for head injuries or muscle contusions. "We know why softer baseballs decrease those injuries: accelerators and stress. But we don't yet have a mechanical variable to decrease for commotio cordis," he says.

There is no widely accepted standard for baseball hardness, though Crisco notes that the American Society for Testing and Materials is working on proposed standards. He adds that the baseballs used in Little League—made from cheaper materials—have been found to be harder than those used in Major League Baseball. NOCSAE has published a voluntary standard for baseballs that are designed to reduce head injuries. Crisco says the group is presently updating the standard to address a greater spectrum of injuries, including commotio cordis.

What's the Prevention Message?

Though Janda and Link disagree on the safety of softer baseballs, they do agree that the devices are not magic bullets for preventing commotio cordis and that good coaching can help young players avoid baseball impact injuries.

"We believe kids should be taught how to get out of the way," Janda says. "I've heard eyewitness reports of kids panicking and walking right into the ball, but if you watch Cal Ripken, he tucks his head and rolls his shoulder so that his scapula takes the blow." He says that kids also need to learn how to avoid chest impact injuries by sliding into base with their back toward the catcher. Janda says some recreational leagues seek to avoid baseball impact injuries among younger players by having the coach of the batting team do the pitching; a few use mechanical pitching machines.

The research jury is still out on how well chest protectors prevent chest impact injuries. Eleven (16%) of the players in the US Commotio Cordis Registry were wearing commercially available protective gear when the incidents occurred. Janda says the ISPM is conducting a study on chest protectors.

Van Auken says that Little League Baseball is in the third year of a 3-year study to determine the protective value of equipment (ie, softer baseballs, batting vests, face masks, breakaway bases) used by various divisions.

References

  1. Kyle SB: Youth Baseball Protective Equipment Project: Final Report. Washington, DC, US Consumer Product Safety Commission, 1996
  2. Maron BJ, Link MS, Wang PJ, et al: Clinical profile of commotio cordis: an under appreciated cause of sudden death in the young during sports and other activities. J Cardiovasc Electrophysiol 1999;10(1):114-120
  3. Link MS, Wang PJ, Pandian NG, et al: An experimental model of sudden death due to low-energy chest-wall impact (commotio cordis). N Engl J Med 192021;338(25):1805-1811
  4. Link MS, Wang PJ, Pandian NG, et al: Resuscitation in a biological model of commotio cordis, sudden death from low energy chest wall impact, abstracted. J Am Coll Cardiol 192021;31(2):403A
  5. Janda DH, Viano DC, Andrzejak DV, et al: An analysis of preventive methods for baseball-induced chest impact injuries, abstract. Clin J Sport Med 1992;2(3):172-179
  6. Viano DC, Andrzejak DV: Mechanism of fatal chest injury by baseball impact: development of an experimental model. Clin J Sport Med 1992;2(3):166-171
  7. Janda DH, Bir CA, Viano DC, et al: Blunt chest impacts: assessing the relative risk of fatal cardiac injury from various baseballs. J Trauma 192021;44(2):22021-303
  8. Kyle SB, Adler P, Monticone RC Jr: Reducing youth baseball injuries with protective equipment. Consumer Prod Safety Rev 1996;1(1):1-4
  9. Link MS, Wang PJ, VanderBrink BA, et al: Reduced risk of death with safety balls in an experimental model of commotio cordis: sudden death from low energy chest wall impact, abstracted. J Am Coll Cardiol 1999;33(2):534A


Researchers Weigh In on Eye Issues

Baseball is the leading cause of sports-related eye injuries in children aged 5 to 14 (1,2). One of the concerns among physicians and coaches has been that a softer baseball could increase the risk of eye injury because the softer material might protrude farther into the eye orbit.

To investigate those suspicions, a recent investigation by Vinger et al (1) had two objectives: (1) to measure the intrusion of baseballs of 6 different hardnesses launched at several speeds into an artificial eye orbit, and (2) to determine if baseball players could tell the difference between harder and softer balls when catching, throwing, and batting.

Researchers found that the softest of the six baseballs intruded significantly into the orbit, and recommended that this ball be used only among players younger than age 6 who have little grip strength. They found that orbital intrusions of the next two softest balls were not clinically meaningful and, because they had a lesser peak force and onset rate than Major League baseballs, should not cause an increase in eye injuries.

When the researchers evaluated whether softer baseballs changed the feel of the game for participants, they found that children younger than age 14 could detect a difference only when using the softest baseball and that adults could not differentiate between the hardest "soft" baseball and standard baseballs.

While advocating the use of softer baseballs in youth baseball to prevent brain injury and commotio cordis, the researchers note the best way to decrease eye injuries in baseball is to use protective eyewear that conforms to American Society of Testing and Materials (ASTM) standards for batters, base runners, and fielders.

References

  1. Vinger PF, Duma SM, Crandall J: Baseball hardness as a risk factor for eye injuries. Arch Ophthalmol 1999;117(3):354-358
  2. Kyle SB: Youth Baseball Protective Equipment Project: Final Report. Washington, DC, US Consumer Product Safety Commission, 1996


Lisa Schnirring
Minneapolis


Field Notes

Can Lean Meat Help Lower Cholesterol?
Patients who have hypercholesterolemia may not need to banish lean red meat from their menus, according to study published in the June issue of Archives of Internal Medicine.

In the randomized, multisite study, 191 men and women with hypercholesterolemia consumed a diet that included 6 oz of lean red meat (beef, veal, or pork) or lean white meat (poultry or fish) 5 to 7 days a week.

During the 9-month trial, total cholesterol and low-density lipoprotein cholesterol concentrations in the two groups were nearly identical and were 1% to 3% below baseline. Triglyceride levels remained near baseline and high-density lipoprotein cholesterol concentrations increased about 2% for both groups. The authors concluded that counseling patients to replace high-fat meats with leaner red and white meats provides more food choices and may improve long-term patient adherence.

Under federal labeling rules, a "lean" meat contains less than 10 g of fat, 4.5 g of saturated fat, and 95 mg of cholesterol per 3-oz serving. According to a press release from the National Cattlemen's Beef Association, a handy way to remember the lean cuts of beef is to keep in mind that each has the word "round" or "loin" in the name. Cuts of pork with "loin" in the name are also considered lean.

Teen-Friendly Exercise Encouragement
The drop-off in physical activity during adolescence represents the start of a cardiac risk factor for many young people. The President's Council on Physical Fitness and Sports, examining the issue in the June issue of its Research Digest, suggested the following strategies for promoting activity in this age-group:

  • Appeal to teens' growing need for independence by stressing that they can and should take personal responsibility for their health.
  • Offer a choice of activities. For example, programs that include rock climbing, in-line skating, or kayaking might be more appealing than traditional physical education programs.
  • Present exercise as attractive, especially when compared to being sedentary. For example, spread the message that it's "cool" to sweat, or highlight athlete role models.
  • Schedule teen-specific recreation programs during evening hours.
  • Seek the input of young people when planning physical activity programs.

Late-Night Exercise May Not Impair Sleep
Some people rule out evening exercise because they've heard that vigorous exercise close to bedtime impairs sleep. However, a study in the June issue of Medicine & Science in Sports & Exercise challenges this view.

Researchers at the University of California at San Diego examined the effect of intense, prolonged presleep exercise in 16 competitive male cyclists. Participants spent a baseline night in the lab, followed by an experimental night and a recovery night. All the subjects underwent each of two protocols at different times. On the experimental night, subjects exercised under bright light for 3 hours or sat under bright light for 3 hours, starting 90 minutes before their usual bedtime. Exercise consisted of cycling at 65% to 75% of heart rate reserve. The subjects went to bed 30 minutes after the exercise or sedentary period. Researchers found no difference in objective or subjective sleep variables under the two protocols.

The researchers say that the study may have practical implications for groups wanting to exercise before bedtime, such as air travelers or students who study late at night. But they caution that the ability to sleep soon after exercise may be unique to physicially fit people because they may recover more quickly after exercise than less-fit people.

Trampoline Injuries Soar
Trampoline injuries in the United States totaled an estimated 83,400 in 1996, a 140% increase over the 1990 figure, according to a report by the American Academy of Pediatrics (AAP) in the May issue of Pediatrics.

Most injuries occurred on home trampolines and involved falling on or from the trampoline or from collisions between simultaneous jumpers. Strains or sprains accounted for 40% of injuries, fractures for 30%, contusions and abrasions 13%, lacerations 11%, and other injuries 6%. The data in the AAP report are from the US Consumer Product Safety Commission's National Electronic Injury Surveillance System and the National Pediatric Trauma Registry.

The AAP states that the report reaffirms its position that physicians should discourage parents from purchasing home trampolines and children from using them. The AAP has also stated that trampolines should not be used for routine school physical education classes or placed on outdoor playgrounds.

Gary A. Smith, MD, DrPH, a member of the AAP committee that authored the report, says the number of backyard trampolines is increasing at an epidemic rate. "When you're driving in the suburbs, you see them up and down the street," he says.

Many parents mistakenly think that children won't be injured if supervised by an adult, says Smith, who is a pediatric emergency physician at Children's Hospital in Columbus, Ohio. He notes that for 56% of the children who were treated at Children's Hospital for a trampoline-related injury in 1996, an adult was supervising at the time of injury. The AAP has suppported a ban of home trampolines since 120211. "I'm hearing now that in many areas homeowner's insurance is hard to obtain if you have a backyard trampoline," Smith says. "Maybe that will help turn the tide."


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