ASK A PHYSIO - Leg Extensions

ASK A PHYSIO - WHATS THE DEAL WITH LEG EXTENSIONS??

Ask a Physio is a section of our monthly PT newsletter that allows you to have your burning questions answered by our Physiotherapists. If you have a question that you would like to ask a member of our team email [email protected] for the chance to have it included in the next edition.

Hi Physio,

I have been reading a lot about the issues with the Leg Extension exercise and I am a little confused as to whether I should be using it with my PT clients or not – can you give me your opinion please?

Nick - PT (Traralgon)

Hi Nick,

This is a very hot topic and one that will surely raise some discussion – however here is a simple summary of the issues with this exercise.

1. Shearing Forces :

In the majority of ground based leg exercises – such as squats and lunges – the resistance to movement runs through the knee joint – basically compressing and stabilizing the knee itself. However – in an exercise such as the Leg Extension the resistance is at 90 degrees to the shin – as this is where you are pushing against to raise the shin pad.

The resistance is at 90 degrees to the long axis of the bone (the tibia) – which has the effect of producing shearing forces across the knee – compared to a squat where the resistance runs along the long axis of the bone. This comes in to play especially with those recovering from ACL repair as the shear forces can significantly load the ACL graft.

2. No Co-Contraction:

In conventional squats and lunge type movements there is contraction of the quadriceps ( to extend the knee) at the same time as there is contraction of the hamstring group ( to extend the hip ) – this is termed co-contraction.

In the Leg Extension exercise there is contraction of the quads with limited hamstring involvement – again promoting shearing forces across the knee and reducing muscle involvement.

3. Functional Transfer:

The actual motion of the Leg Extension exercise produces limited functional carry over to real life sports and daily tasks - compared to squatting and lunging movements that are common patterns in everyday life.

4. Reduced Muscle Involvement:

The majority of PT clients are time poor and are better off doing an exercise involving a large number of muscle groups compared to smaller isolated groups – simply from a time management and results perspective.

My opinion - stick with the closed chain weightbearing exercises - the benefits of definitely outweigh those of the leg extension machine.

Devon Soutar - Physiotherapist