When talking about running gait, and especially in relation to injuries, most people will focus on the stance phase – that is the section of the cycle where the foot is in contact with the ground. We’re all concerned with how the foot strikes the surface and what it does between this point and when the toes leave the floor at the end of stance. What happens at the knee and hip joints and pelvis in stance phase also gets a fair amount of attention. What very few people consider is what happens with the other leg during this time!
The most important thing I can tell you about the swing leg is that “the foot will only go where it is put”. This is a direct quote from James at Kinetic Revolution. What he is saying is that we are all concerned over how the foot impacts the floor, but how the foot hits the floor is largely dictated by the swing phase before it. Here’s an example:
In a runner with very little hip and knee flexion in their mid to late swing phase, a compensation occurs whereby the knee extends fully just as the foot hits the ground. This is to help them achieve that little bit more distance per stride, which is limited due to the reduced hip flexion. This will usually result in a heavy heel strike and the two combined can contribute to both shin and calf pain, and patellofemoral knee pain.
A slight increase in knee and hip flexion during the second half of the swing phase, means we cover more ground with each step, reducing the need for full knee extension and instead resulting in the foot hitting the ground underneath a flexing knee, rather than out in front of an extended knee. This is a much better scenario for both the lower leg and knee joint.
In addition, an increase in the flexion moments at the knee and hip during mid to late swing phase means a reduced ground contact time, or stance phase. This is also good news as less time in contact with the floor, reduces the stresses being loaded through the joints and tissues.
It’s an interesting concept and one we covered a lot on the running analysis and retraining course I attended with Kinetic Revolution a couple of weeks back. It was really interesting to see how a slight adjustment to a runners swing phase really impacts the rest of the gait cycle.