The Connection Between Shank Angle & Injury
One of the most critical but ignored aspects of run form is the shank angle: the angle between the shank and a line dawn perpendicular to the ground at the point of impact. This angle determines the braking (and breaking) forces associated with every step you take as you run and the amount of propulsive force you apply to the ground—as well as the timing of that force.
The runner with a large shank angle usually hits the ground with a straight leg, with the landing foot well in front of the body. In contrast, the runner with a small shank angle hits the ground with the foot closer to the body (and the body’s center of mass), & with a “softer" and more flexed knee. Small SAT’s (shank angle at contact) provide milder landings, with impact force travelling up the leg at lower speed while reducing risk of injury. Running fast with high shank angles forces the runner to ram a leg into the ground at high speed with each step. Running quickly with lower shank angle brings your feet back and allows your leg to work like the springier structures they were intended to be (Owen Anderson, PhD).
(Left) Optimal shank angle @ 6-7 degrees, with flexed knees, midfoot strike at initial ground contact, large forces placed on the Achilles tendon and calf muscles.
(Right) Large shank angle at initial ground contact, “slap down” forefoot strike with straight legs, limited dorsiflexion and excessive force on metatarsals resulting in restricted forward velocity
The runner pictured to the right in orange Nike's clearly has poor dorsiflexion. This causes a ‘loose’ or ‘floppy’ foot due to relaxation at the ankle joint which results in striking the ground through the toes, resulting in poor force distribution that contributes to injuries such as shin splints, metatarsals fractures or runner’s knee. Poor dorsiflexion also reduces the ability to utilize and apply power from the posterior chain muscles. Unlike the bigger, stronger muscles in the calf, dorsiflexion is less natural and lacking from some runners’ gaits. Therefore, when pushing yourself to become a more accomplished runner or sprinter, a necessary focus should be put on dorsiflexion. Poor dorsiflexion can be caused by several factors.
One common and easily fixed issue is flexibility with the lower limb posterior chain muscles: when these are tight they restrict dorsiflexion. Another cause of reduced dorsiflexion is restriction of the ankle joint itself, usually caused by a tight joint capsule, or scar tissue and adhesions occurring in the joint. It could even be caused as a secondary reaction to many hours in the bike saddle, previous ankle injury, such as a sprained ankle. Finally, if there is no soft tissue or mobility issue, it may just be that the anterior muscles are weak, fatigue quickly and just aren’t utilised in the first place due to a lack of awareness or correct technique.
In order to decrease SAT, dorsiflexion upon impact is critical as the top of the foot must move closer to the shin instead of away from it. It can take months for a runner to transform completely from a high SAT to a six or seven-degree SAT.
The Fix:
1. Be aware of it and consciously try to dorsiflex as you run. This will feel strange to start with, but you are trying to encourage this to be second nature.
2. The range of dorsiflexion can be improved by a variety of manual therapy techniques. If it is a soft tissue issue, it is about stretching and releasing the calves. Self-massage (using rollers, trigger point balls or hands) along the muscles in the lower leg can offer critical and necessary improvements in biomechanics and mobility, assisting the relief of common foot issues related to a lack of range of motion, limiting dorsiflexion.
3. Single leg Isometric dorsiflexion holds:
Standing on one leg, lift one knee to hip height with a 90-degree angle at the knee joint with the shin perpendicular to the ground. Flex the toes of the raised leg upwards towards the shin and hold for 30 seconds. Arms should be held in running position and the glutes of the planted leg should be engaged. Repeat on the other side for 3 sets.
4. Dorsiflexion with a resistance band:
Attach a band to something stable in a loop e.g. table leg, pole. Sit on the ground with your leg straight in front of you. Loop the other end around your forefoot/toes. Shuffle back so there is a moderate amount of tension in the band. From there, allow your toes to come forward & then pull them back towards your shins and back 12 for 20 seconds, for 2-3 sets.
5. Heel walks:
Keep your heels on the ground while pointing your toes upwards without locking the knees. Walk on your heels with your toes pointing upwards for 20m x 3 sets, using your arms as you would when running. You’ll start to feel a slight ‘burn’ in your shins. This is not shin splints – congratulations, you are activating your tibialis anterior.
The change should be made progressively to avoid injury and all drills should be performed barefoot.
