Is the Covid-19 pandemic to blame for the rise in MLB injuries?

The lack of structure over the last year has made regular training and playing schedules difficult. The results can be seen in baseball treatment rooms

Baseball is a grind. Among the major US professional sports, MLB has the longest season: 162 regular-season games. Last year, due to the coronavirus pandemic, the 2020 season was shortened, which to many, seemed like a good thing. It would lead to an increased rest period and hopefully less injuries. It seems, however, that the opposite has come true. Already, only a few months into the 2021 season, injury listings are on the rise. Statistics have shown a 30% increase in injuries thus far. The usual suspects such as UCL elbow injuries and ACL knee injuries have popped up as expected, but the overwhelming increase has been on “strains” and “sprains”.

Strains and sprains often refer to muscles and tendons. The UCL and ACL refer to ligaments. This anatomic difference can be important. Ligaments are like small ropes holding bones together. The UCL helps stabilize the inner elbow joint while throwing. The ACL stabilizes the knee joint for cutting and pivoting. Muscles, on the other hand, are meaty structures made up of fibers that can be stretched, or if pulled too far apart, torn. This can happen even at the microscopic level. Tendons are what muscles turn into so they can attach to bones and move them. These can also be stretched or torn. When muscles or tendons are stretched or partially torn, they aren’t necessarily repairable by surgery and can take a long time to heal, developing into nagging injuries that repeatedly rear their heads throughout the season or an athlete’s career.

Baseball is a predominantly one-sided sport – meaning you do certain activities with only one side of your body at heavy loads. Throwing, for example, stresses only one arm. Hitting affects opposite sides of the body in unique ways. Pitch counts were designed to prevent Tommy John elbow surgeries and have their roots in overuse injury prevention. Unfortunately, there is some inherent limitation in their calculation as they do not take warmup pitches and practice throws into account. Now, some trainers are starting to consider whether the same rules might apply to hitting. Can a player swing the bat too much?

Muscles also differ from ligaments in that ligaments are a static structure. You can’t warm them up as much as you can a muscle. Injury prevention for ligaments tends to focus on limiting stress across them. Body mechanics play a big role in this, which is why so many teams have looked at motion analysis video capture for their pitchers. Based on the body’s position and acceleration, the stress across different joints can be calculated. Muscle injury prevention, however, may be more about performance cycles and proper warm ups than about maximum loads across a static structural ligament. With rule and schedule changes combined with intermittent stopping and starting of the 2020 season, some players may have lost their highly honed rhythm and therefore their bodies, despite the prolonged rest, may not have been properly warmed up for the current season’s workload.

A recent study of lower extremity muscle strains in Japanese baseball players was published in the Orthopedic Journal of Sports Medicine. In the study, researchers looked at 55 muscle strains on a professional baseball team between the 2006 and 2015 seasons. They also looked at MRIs of the player injuries. 60% of the muscle injuries were located in the hamstrings. Among the injuries studied, MRI predicted how long players were out. Lower grade strains took four to five weeks to return to play, whereas players with higher-grade injuries took 10 weeks to return.

In 2012, researchers published a study looking back at abdominal strains in major league baseball from 1991-2010. At that time, abdominal muscle strains represented 5% of all baseball injuries on the disabled list. These muscles appear to be more active on the leading side of a pitcher’s throwing motion, and both sides of a batter’s torso movement. At least 92% of these injuries were abdominal oblique or intercostal muscle strains. 44% of those injured were pitchers. Even then, the authors cautioned that an upward trend was being seen from 1991-2010, especially in early-season injuries during March and April. 12% of these players would battle a re-injury of the same muscle, and over half (55%) would suffer the re-injury during the same season. The overall injury rate also climbed 22% higher in the 2000s than the 1990s.

Areas of muscle strain injury prevention traditionally have focused on flexibility, fatigue, core stability, and strength. The concept of flexibility is something everyone is taught even at an early age in physical education class. Actual sports studies have been conflicting in preventing muscle strains based on flexibility, but those that do show a difference focus on pre-season muscle flexibility, which in baseball, may point to spring training affecting the early months of the season. Fatigue has a lot to do with endurance. Too little time spent building up the body’s energy reserves can result in early fatigue. But the opposite can be true too. Overworking or overtraining can lead to diminished returns and earlier muscle fatigue.

Stability refers to core stability and using the whole body to perform activities, which is especially true with pitchers. The term “kinetic chain” was coined to describe the generation of power from the ground up, traveling through the legs, the core muscles, the torso, and finally exiting out the arm. Like a boxer, much of a thrower’s power actually comes from the legs and hips. Finally, strength is a core principal of any athlete’s training routine, but one aspect that is sometimes neglected is the eccentric exercise.

While most weight-lifting focuses on squeezing the muscle to shorten it and bring the bones closer together (think of a biceps curl), eccentric exercise may be more important in injury prevention. This occurs when the muscle fibers are activated, but the muscle belly lengthens and the weight slowly moves away from the body. This recreates more of the scenario where a muscle is used to stabilize or slow the body down, such as in the follow-through of a throw, pulling up when sprinting to a ball, or stabilizing the trailing side during a swing.

Traditionally, despite an early-season rise in baseball injuries, the injury rate usually levels out, with the lowest levels seen by September. Even in 2015, the abdominal injury rate of MLB players seemed to turn downward from 2011. Yet, at the same time, the abdominal injury rate of minor league players was trending upwards. Minor league players tend to have less of a structured schedule than major league players. Perhaps the recent rise in abdominal injuries reflects the schedule and training irregularities that major league players aren’t used to seeing. As organizations and players are better able to return to their pre-pandemic routines, like much of the rest of the world hopes to do, perhaps they too will be healthier for it.

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