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, find two recent studies. 
In the first, 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.
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 study 1finding 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 study1reported 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. 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.
Increased risk of elbow injuries requiring surgery
It isn't just increased risk of shoulder injuries to which pitchers in warm-weather climates permitting year-round play are exposed, say the authors of a new study by researchers at the University of Florida, it's also increased risk of elbow injuries requiring Tommy John surgery.5
In a study published in the Orthopeadic Journal of Sports Medicine, they found that there was a greater likelihood of undergoing Tommy John surgery in the Southeastern Conference (SEC) compared with the Big Ten, and an increased risk of ulnar collateral ligament reconstruction (UCL-R) for pitchers who played high school baseball in southern states versus northern states, irrespective of collegiate play location.
"Our data and others' data," said lead author Jason Zaremski, a physician at the University of Florida's Orthopaedics and Sports Medicine Institute, "raise the question of whether a pitcher has a finite number of innings he can throw before he is predisposed to an elbow injury." Some have suggested that conserving these innnings as an adolescent and high school pitcher may reduce the likelihood of an UCL injury, Zaremski said, but the "data indicate that even in high school, if one is pitching in a warm weather climate, he is at increased risk of having a UCL-R.
Is anyone listening?
One possible explanation is increased likelihood of pitching while tired in warm-weather climates; according to a 2006 study6 pitching with fatigue increases the injury risk up to 36 times in adolescent pitchers versus those not pitching with a tired arm, notes Zaremski.
"These findings have been available for almost a decade, yet [a 2014 study7] has shown that [they] have not influenced our young athletes. Adolescent pitchers continue to pitch with pain, with nearly half of the pitchers in this study being encouraged to keep throwing despite having arm pain," which is considered a precursor to potentially significant throwing injuries.
Take pitches into account
The findings prompted the authors to recommend that physicians, athletic trainers, and coaching staff be factor previous playing exposure should be considered when designing pitching and throwing programs for pitchers, especially for starting pitchers, where volume of pitches and innings thrown is increased compared with their relief pitcher counterparts. "Reducing the volume of throwing, especially at younger ages, may prevent UCL injuries in pitchers," they concluded.
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.
5. Zaremski JL, et al. Does Geographic Location Matter on the Prevalence of Ulnar Collateral Ligament Reconstruction in Collegiate Baseball Pitchers? Orth J Sports Med. 2015;3(1)(epublished November 20, 2015 doi: 10.1177/2325967115616582)(accessed November 23, 2015 at http://ojs.sagepub.com/content/3/11/2325967115616582?cpetoc)
6. Olsen SJ, Fleisig GS, Dun S, Loftice J, Andrews JH. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am J Sports Med. 2006;34:905-912.
7. Makhini EC, et al Performance, return to competition, and reinjury after Tommy John surgery in Major League Baseball pitchers: a review of 147 cases. Am J Sports Med 2014;42:1323-1332.
Created February 22, 2011, updated November 23, 2015
