The extra time high school pitchers living in warm-weather climates spend in baseball activities puts them at greater risk of injuries to their pitching shoulders than their cold-weather peers, finds a first-of-its-kind study published in the February 2011 edition of the American Journal of Sports Medicine. 
Researchers at the Mayo Clinic in Rochester, Minnesota and the Kerlan-Jobe Orthopedic Clinic in Los Angeles collected data on a random sample of 100 uninjured male high school baseball pitchers between 14 and 18 years of age who had pitched competitively for at least the past 3 consecutive years with no current injuries or complaints of pain. Fifty pitchers were recruited from the cold-weather group (Minnesota) and the warm-weather group (California, Arizona).
Testing was then performed during the athlete's off-season with at least 1 day of rest to measure throwing of shoulder range of motion (ROM), and internal and external rotation muscle strength of the dominant (pitching) and non-pitching shoulder, and the number of months per year in which each athlete participated in pitching activities during the 3 years prior to study participation captured.
Findings
Analyzing the test results and participation data, researchers found:
- significant differences in dominant arm rotational strength, with the cold-weather climate group exhibiting significantly greater external rotation strength (which plays a critical role in maintaining a healthy, stable shoulder joint);
- significant differences, as expected, in the number of months per year the athletes participated in pitching activities (9 months on average for the warm-weather group compared to an average of 6 months for the cold-weather group);
- an inverse negative relationship between the average number of months participating in baseball activities and internal rotation motion and external rotation strength in the warm-weather group (i.e. greater time spent pitching was associated with less internal rotation and external rotation strength); and
- that the time spent in pitching activities was not predictive of any motion or strength measures for the cold-weather group.
Injury risk
"Although athletes in the current study were uninjured, our results indicate that athletes who reside in warmer-weather climates may be at increased risk for injury secondary to excessive time dedicated to pitching during a calendar year," the study says, "an increased injury risk ... further supported by the inverse relationship between the number of months pitching and internal rotation ROM, and external rotation strength."
Significant internal rotation motion loss, and external rotation muscle weakness, the study noted, have each been associated with throwing arm injury in the baseball athlete in prior studies.3,4,5
"The amount of time an athlete dedicates to pitching activities is clinically significant," the study notes, "as many injuries in baseball are believed to be a result of cumulative microtrauma associated with throwing."
The results are consistent with a prior study1 finding that 10 months per year spent pitching increases the injury risk for athletes from warm-weather climate fivefold compared with playing patterns of uninjured athletes.
The same study1 reported that individuals who spent more than 8 months per year pitching were at approximately 5 times increased risk for injury requiring surgery, prompting the authors to suggest that youth pitchers may require more than 3 months of active rest (i.e not throwing) each year to minimize the risk for serious injury.
Another study2 found that pitching during the years of skeletal immaturity and rapid growth (ages 11 to 13) has the greatest potential to affect vulnerable tissues, with the potential to contributing to loss in internal shoulder ROM and external rotation gain for 16-year-olds compared to 8-year-olds.
Vulnerable group
The relative weakness of the external rotators in warm-weather athletes compared to their peers who live in cold climates, and the negative relationship between months spent pitching and internal rotation and external rotation strength in the warm-weather group "suggest these athletes are a previously unrecognized, vulnerable population in terms of their injury risk," the study concludes.
Year-round play hurts, not helps
"What we can say pretty definitively at this point is that playing baseball year-round as a young athlete is not a key to long-term success," says Wendy Hurd, PT, PhD, SCS, one of the study's co-authors. "Even though there might be opportunities to play ball year round when you live in a warm-weather climate, it is advantageous to the health of the pitcher's arm to take extended periods of rest from throwing."
While youth coaches, Dr. Hurd notes, "rarely see the consequences of 'over pitching,'" college and pro coaches are aware of the problem. As a result, she says, "it is much more attractive to coaches of older athletes to draft or recruit a talented athlete with less pitching experience than one who has been pitching year round since the age of 8 [because of the] strong association between throwing arm injury and year-round participation."
"Keeping up with the Joneses" mentality
As sports medicine professionals, Dr. Hurd says, it is hard to fight what she sees as the role societal norms and expectations make to the problem of overuse injuries, or what she labels the "'keeping up with the Joneses' mentality" that many parents have. "Just like when we see our neighbor buying a large screen tv or expensive luxury sedan, we feel like we have to one-up them with our children. If the neighbor's child is playing in an all-star league, then our child will play in two. If your child is going to play traveling ball, our child will play at a pro-day."
At its root, she sees a common problem: kids are simply not getting enough rest: "It doesn't matter what climate you live in, though if you live in a warm-weather climate it is a lot easier to play more months out of the year than a child living in Minnesota!"
The bottom line for parents, says Dr. Hurd: you are not going to turn your 12-year-old into a hall of fame pitcher, but you can keep him from becoming one.
Source: Kaplan KM, Jobe FW, Morrey BF, Kaufman KR, Hurd WJ. Comparison of Shoulder Range of Motion, Strength, and Playing Time in Uninjured High School Baseball Pitchers Who Reside in Warm- and Cold-Weather Climates. Am. J Sports Med. 2011; 39(2): 320-328.
Footnotes
1. Olsen SJ 2nd, Fleisig GS, Dun S, Loftice J, Andrews JR. Risk Factors for shoulder and elbow injuries in adolescent baseball pitchers. Am. J Sports Med. 2006; 34(6); 905-912.
2. Meister K, Day T, Horodyski M, Kaminski TW, Wasik MP, Tillman S. Rotational motion changes in the glenohumeral joint of the adolescent/Little League baseball player. Am. J Sports Med. 2005;33(5):693-698.
3. Myers JB, Laudner KG, Pasquale MR, Bradley JP, Lephart SM. Glenohumeral range of motion deficits and posterior shoulder tightness in throwers with pathological internal impingement. Am. J Sports Med 2006;34(3):385-391.
4. Wilk K, Macrina L, Fleisig GW, et. al. The correlation of glenohumeral joint internal roation deficit (GIRD) and rotational motion to shoulder injuries in professional baseball pitchers. Am. J Sports Med. in press 2010.
Created February 22, 2011
