What is an Abdominal Side Strain?
Side strains are an injury almost unique to cricket's fast bowlers. Javelin throwers are the only other athletic participants who also regularly strain the side abdominal muscles.
In bowlers, side abdominal strains occur on the non-bowling side of the body and the majority is strains of abdominal muscle insertions on to the lower ribs. Side strain injury is caused by tearing of the internal oblique muscle from the under surface of one of the lower four ribs or costal cartilages. MRI scans can document the site of a muscle tear, characterise the severity of injury, and monitor healing. Bony stress lesions (such as stress fractures of the 10th or 11th ribs) can occur but are less common.
There is a traditional belief that a side strain is almost a ‘rite of passage' for an elite fast bowler that is almost certain to occur once early in his playing career and is thereafter unlikely to return. However, there are cases of recurrent side strains that plague bowlers throughout their career.
Diagram 1
Normal anatomy of anterolateral abdominal wall. Diagram shows internal oblique muscle arising from iliac crest and inserting into lower fourth rib under cover of external oblique muscle.
Diagram 2
Normal anatomy of anterolateral abdominal wall. Diagram of coronal section through abdominal wall shows three flat muscles. Internal oblique muscle lies immediately underneath ribs.
What Causes Side Strain?
Side strains are strongly related to bowling speed, with the fastest bowlers much more likely to suffer this type of injury. It is postulated that the mechanism of injury for internal oblique muscle strain is sudden eccentric contracture with rupture of muscle fibres. An eccentric contraction is one that stops a muscle or joint from excessively lengthening.
Movements associated with bowling and throwing cause lengthening of the muscle, which is then subjected to superimposed eccentric contraction, making it vulnerable to rupture.
In research studies focusing on fast bowlers, the muscle tear occurs on the non–bowling arm side. For example, in a right-handed bowler, the left arm is initially hyperextended and then forcefully pulled through to allow the right arm to follow through and release the ball. In the hyperextended position, the internal oblique muscle on the left side can be assumed to be at maximum tension or eccentric contraction. The sudden vigorous motion from this eccentric contraction or pull through that allows the dominant shoulder to flex and release the ball is the probable point at which the internal oblique muscle is likely to rupture. A similar mechanism can be proposed for other throwing sports.
How is Side Strain Diagnosed?
MRI appears to be a sensitive test for evaluating side strain injury, showing an abnormality in all patients who had a clinical suspicion of a muscular tear. Stripping of the periosteum occurs as the muscular attachment is avulsed from the osseous or cartilaginous origin; this can result in excessive hemorrhage even though the muscle tear may be low grade.
How to Prevent and Treat Side Strain
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