Dexter Fowler and the impact of intercostal muscle strains

A core muscle group fundamental to the mechanics of numerous baseball activities as well as breathing, intercostal muscle strains can be devastating to a player's performance. This painful reality has recently come to fruition for Houston Astros outfielder Dexter Fowler, who was recently placed on the 15-day DL with a right intercostal strain after missing four games battling the injury. The strain comes in Fowler's first season with the team and pauses a promising start to his Astros tenure, which has seen him produce at a 122 wRC+ clip in 76 games after a mildly disappointing 2013 season limited by a number of nagging injuries.

The intercostals are a collection of 11 separate muscles on each side of the ribcage, each of which are found in between the ribs (costae in Latin), hence their moniker. Muscles comprised of three principal layers, they connect one rib to another and work to expand and contract the ribcage to aid in breathing. The intercostals are most commonly injured due to a sudden contraction when they are in a position of stretch, such as when throwing, or during motions involving excessive side bending or twisting forces, such as swinging a bat. The injury mechanism, as with other non-contact injuries of the core, sees the player performing a repetitive activity or an activity that overextends their usual level of exertion or range of motion. Symptomatically, players often experience a sudden, sharp pain or pulling sensation in their lower ribcage during the provoking motion. Pain is commonly acute but can occur gradually over time and is often present when taking a deep breath. Severity of the strain can vary but can be broken down into three grades:

• Grade I – Mild, with few damaged muscle fibers. Some discomfort and minimal loss of strength and motion.
  
• Grade II – Moderate, significant number of muscle fibers damaged with no rupture. Increased pain and discomfort. Significant loss of strength and motion.
• Grade III – Severe, where the muscle is ruptured. Increased pain and discomfort, with a palpable defect of the muscle. Surgery often required.
  

The discomfort arising from an intercostal strain can permeate all baseball activities. From a throwing perspective, Fowler's right-sided injury can be particularly troublesome, since he is a right-hander. Wind-up and stride components of throwing are potentially not affected by the strain, aside from some pain upon inspiration in preparation of throwing. Arm cocking and acceleration phases, with their quick and dramatic shifts in weight distribution and transfer of force, are where the core muscles will be maximally activated, with significant stretch of the intercostals occurring during arm cocking and explosive contraction of the intercostals occurring during acceleration and into arm deceleration and follow-through, creating large amounts of tension arising from their participation in deceleration and in maintaining balance and posture during the throwing motion.

Hitting performance is also affected with intercostal strains, as the cocking, coiling, acceleration, and deceleration phases of hitting are akin to those seen in throwing and involve the same biomechanical processes and muscle group recruitment. Because the activity of the intercostals encompasses almost the entire hitting (or throwing) motion, Fowler's injury will be felt and exacerbated despite his ability to switch hit, but will be more pronounced when swinging left-handed, as alluded to in the throwing mechanics discussion. However, the injury should affect hitting less than throwing, due to the forces generated and translated throughout the hitting motion better distributed across the body and into larger, more accommodating muscle groups, with less dramatic weight shifts involved, preventing excessively large motions arising from the core.

A less focused upon aspect of baseball that is at play with Fowler's injury and game—one that is predicated upon speed and quickness—are the effects of the strain on transition mechanics, in particular, the transitions from standing in place to sprinting on the base paths as well as the transition from swinging to running. A sizable number of intercostal strains occur in the moments after contact is made, in the first few steps coming out of the batter's box, when the hitter's body exhibits large amounts of spinal rotation, and effort is being made to transfer energy into sprinting as quickly as possible. Abduction of the lead leg—when batting lefty, this is the right leg—in an oblique direction (towards first base) in the midst of a quick transition from standing to sprinting is one that puts the intercostals at increased risk of injury. Players are not immune to suffering strains on the base paths, as Todd Hundley's injury while looking over his right shoulder to find where a sharply hit ball landed after rounding second base can attest.

As with many muscle strain injuries, Fowler's treatment protocol is a conservative one, with RICE therapy, anti-inflammatory medication, as well as stretching exercises and other physical therapy modalities available for use. Time to complete recovery from intercostal strains is usually on the order of four to six weeks.

Given Fowler's history of of core injuries, which includes a rib contusion from running into the outfield wall in 2010 and an abdominal strain in 2011, extra attention will be paid to ensure that his current strain will not place him at increased risk for continued core injuries.

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Stuart Wallace is an associate managing editor and writer at Beyond The Box Score. You can follow him on Twitter at @TClippardsSpecs.

References: Dines, J. S. (2012). Sports medicine of baseball. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.