Foot strike in running is talked about a lot. Whether a person first hits the ground with their heel, mid-foot or forefoot. Lesser consideration is given to the rotation of the leg and how this influences the position of the foot on the ground. In other words, does the foot face straight ahead, toes turned in or toes turned out?
To understand how the biomechanics work it can be handy to feel it yourself. To do this stand-up and put your left heel on the ground just in front of you. Keep the pressure nice and light through your heel. You'll notice that your knee is fairly straight. Now place your left fingertips on the bony part on the outside of your hip. As you turn your foot inwards and outwards you are creating rotation through your leg and you will be able to feel this underneath your fingertips at your greater trochanter (side hip bone). This demonstrates that the rotation of your foot as it contacts the ground has most of its effect at the hip joint, more so than the knee or the ankle/foot.
Each person has their own individual characteristics to how their foot is placed on the ground during running. It is quite common for there to be differences between the left and right sides. This is usually a reflection of slightly different ‘architecture’ or bone structure in the femur (thigh) and tibia (shin). Naturally, the femur has a slight twist inwards and the tibia has a slight twist outwards. Typically, the tibia has slightly more rotation than the femur, resulting in a slightly toe out position. This said, the amount of rotation varies from person to person.
To roughly test your natural foot position on the ground, start by walking/jogging/running on the spot. Make sure you move for a reasonable amount of time, enough to get distracted by something else. Alternatively, purposefully distract yourself by counting numbers or talking to someone. Randomly stop yourself and allow your feet come to settle in their own way. Take a look down and note your foot position on the ground. Whilst this may sound fairly rudimentary, it is a surprisingly effective way at determining your preferred foot position.
Another strategy is to look down whilst you are running and simply observe your foot position. This can be fairly tricky, particularly if you strike with your foot underneath your body in a more mid-foot to forefoot pattern. Also, your foot is moving mighty quick and can be tricky to see.
In a clinical setting is not uncommon for me to work with runners who have been given advice to change their foot position on the ground. For example, I worked with a chap who had fairly moderately turned out feet/legs and had previously run like this, with no worries. His running coach suggested that he turn his feet straight ahead. This had the effect of rotating his hips inward and contributed to an episode of knee pain. Simply returning to his previous and more suitable running pattern alleviated his problem.
When it comes to the rotation of your foot as it lands on the ground, the idea is to go with the flow. The make up of your skeleton favours working in a particular way and that is likely to be different from someone else and may even be different side to side. Acknowledging and accepting this can lead to better running technique and more efficient movement through the legs during running. Sounds pretty good to me. On the flip side, excessively controlling or restricting movement away from normal can increase the load on the musculoskeletal system.
A little tack on note for the end: muscle strength, length and control also contribute to foot position on the ground. A chat for another day. So does foot structure and some other funky stuff.