I just read a series of short articles on Active.com entitled Shin Splints 101 which contained some conventional thinking on this common running injury. I just wanted to contrast and compare ideas for evaluation, treatment and exercise based on our findings at the MIHP Think Tank. Are you ready for an advanced course on shin splints? Here we go:
Our work in muscle injury revolves around two basic physiologic principles:
1. Sherrington's concept of reciprocal innervation: If one muscle is short and tight (or over facilitated), then it's antagonist will neurologically become long/weak (inhibited)
2. Synergistic dominance: If one muscle become over facilitated, then it's synergist may become inhibited
Another premise uphold when looking at muscle injury is this: The muscles that come in crying out in pain are not usually the short/tight ones, but the ones that are long and weak. The underfacilitated. The overused.
What is a shin splint? It is an injury resulting from overload to the anterior compartment muscles of the lower leg (primarily tibialis anterior and tibialis posterior). These muscles are responsible for decelerating dorsiflexion (tibialis posterior), plantar flexion (tibialis anterior) and pronation (both of them).
Who are their antagonists? The gastrocnemius is the antagonist to tibialis anterior. That is, if the gastrocnemius (calf muscle) is short/tight, then the tibialis anterior becomes long and weak, and thereby prone to injury.
Who are their synergists? The gastrocnemius is the synergist to posterior tibialis (i.e. they both decelerate dorsiflexion). If the gastrocnemius become short and tight, then the posterior tibialis may become inhibited.
Pronation v. supination: Because both the TA and TP are located on the medial side of the ankle, they are prone to injury in someone who over pronates. Remember, pronation should only occur for 25% of the stance phase. Any more time spent pronating will result in overload to the tendons and ligament on the medial side of the ankle and lower leg.
The two most common causes of over pronation: Believe it or not, it isn't a lack of an orthotic in your shoe! Before you slip an orthotic in your shoe or invest in motion control running shoes, consider that the two most common causes of over pronation are a weak gluteus medius (hip abductor) and a lack of ankle dorsiflexion (tight calf muscles).
Conventional wisdom says: Strengthen the gastrocnemius (calf muscles) by doing heel raises and the tibialis anterior by doing toe raises. Stop over pronation by purchasing supportive shoes.
ReBUTTal on conventional wisdom: The tibialis anterior didn't get hurt because it was too weak. It got hurt because it was inhibited and/or overworked. Don't work an already overworked muscle. Instead stretch the gastrocnemius (calf muscles) with the toes pointed straight ahead AND strengthen your gluteus medius and maximus (your butt muscles).
For you clinicians out there:
1. Check pelvic alignment. An anteriorly rotated innominate or inflare can create a functionally longer leg, creating an over pronation scenario.
2. Check for trigger points in the iliopsoas and piriformis as these will externally rotate the leg (creating over pronation forces) and inhibit the gluteal muscles. Counterstrain them.
3. Check for trigger points in quadratus lumborum. The quadratus lumborum and gluteus medius are functionally antagonistic in the frontal plane. If QL is short/tight, then GM becomes long and weak. Counterstrain it and then teach QL to work long and GM to work short.
4. Normalize ankle dorsiflexion. If this is just due to tight gastrocnemius, the gravity drop or downward dog exercise are excellent. If the restriction is felt in the anterior ankle then a posterior talar glide will be necessary to normalize dorsiflexion.
Enough said. Now, go and chase those runners down and help get rid of their pain!
Until next time...