Q&A: Why Do Some Runners Overuse Rectus Femoris?

Response From Coach James Dunne

Thanks for the great question Maureen. This is something I've been considering a lot over the past few months.

N.B. I'd be interested in the opinion of others in the Sports Injury industry... The following are simply my thoughts and simple rationalisations of what I see coaching on a daily basis.

If anybody has any research to back these points up, or prove me wrong - I'd gladly welcome the input either way! 

If you consider the following factors in combination, I feel it could be fairly easy to explain why distance runners have a tendency become so overactive through Rec.Fem.

Different Hip Flexors for Different Ranges

In terms of the muscles making up the hip flexor complex, and their individual lever-arms / muscle actions; Iliopsoas really comes into its own in producing inner range hip flexion (knee up near hip height, and above). In this inner range, Iliopsoas is far more mechanically effective in flexing the hip than Rec.Fem. could ever be.

Conversely, when the hip is in a mid and outer range flexed position, Rec.Fem. has a far more effective lever-arm to create hip flexion, than that of Iliopsoas. The body tends to favour the path of least resistance, thus Rec.Fem. picks up most of the load in flexing the hip through outer and mid range.

Running Pace Dictates Range of Hip Flexion Used

Most of us recreational athletes don't run much running (if at all) at paces requiring inner range (~90^o) hip flexion as part of our running gait. Put simply, we don't run the majority of our milage with our knees coming up near hip height. Most of us aren't running at paces requiring that kind of stride length.

Instead, during swing phase of most running paces below a sprint, most of us work the hip through from outer to mid-range of flexion, and back again during stance phase.

This whole cycle keeps the hip in the sagittal range-arc that favours Rec.Fem. as the go-to hip flexing muscle, due to its mechanical lever arm. That's not to say that Iliopsoas isn't involved - of course it is, partially assisting in hip flexion, but also in its role as a lumbro-pelvic stabiliser.

Another Long Lever-Arm

Consider also the lever arm not of the relatively small Tensor Fascia Lata (TFL) muscle in isolation, but of TFL and the ITB in combination. The ITB acts kind of like a super-long tendon for TFL, providing it with a massive lever arm in comparison to its muscular size. Perhaps this enables it to assist in hip flexion (as well as abduction) due to it's anterior positioning relative to the axis of the hip joint.

When Rec.Fem. fatigues, I often see TFL kicking in more in an attempt to assist hip flexion - the problem is that it simply isn't mechanically efficient in doing this, so it just becomes overactive and tight - directly affecting tension in the ITB.

Rehab & Re-education

The way I see it, there are a number of rehab and gait re-education factors to be considered here.

1) Strengthening Iliopsoas

As alluded to above, if a runner does very little training in a range of hip flexion that really challenges Iliposoas, chances are it will be significantly weak in comparison to Rec.Fem., creating an imbalance. To improve muscle balance, it will almost certainly benefit the athlete to work on specific Iliposoas strengthening as part of a consolidated rehab plan. This is so often omitted.

Article on Iliopsoas Strengthening to follow soon!

2) Gait Re-education

I often find that increasing hamstring activation in early swing phase, flexing the knee slightly more through swing to the point of recovery (heel under the body), helps to reduce the torque of the swing leg acting on the hip in the sagittal plane. This reduces the effort required from Rec.Fem. to flex the hip.

This often has to come with a regime of hip flexor and quad stretching, to accommodate the increased knee flexion in swing phase.

I find this means of taking the load off the hip flexors through shortening the lever-arm of the swinging limb (essentially a third class lever) particularly effective.

As I said... simply some thoughts I've been having recently. Comments both for and against are very welcome!