I regularly find myself debating this exercise with students, new staff, and part-time staff all from different clinical backgrounds and I always find myself asking them – “Why is that patient doing clams?”
For those unsure of the terminology, the “Clam” exercise is designed to activate the external rotators of the hip, performed in side lying with limited pelvic / lumbar rotation.
Firstly I’d like to make it clear that this exercise does have a place in some rehab plans and I am not adverse to including it as part of a program where necessary – but I strongly disagree with it being a mainstay in rehabilitation plans. Purely going from anecdotal evidence, people seem to use clams as a way of increasing endurance of the glutes, particularly glute med. Often prescribing high sets and reps to target the endurance component of the muscles. Previous literature has suggested that Maximum Voluntary Contraction (MVC) of greater the 50% is required to produce any strength gains in an individual muscle (Atha 1981). Figure 1 below demonstrates the EMG activation of glute med during 2 clam exercises, at 30 and 60 degrees hip flexion. Its clear from this study that the activation of glute med is below the required level to achieve any strength gains.
Glute med (if it ever did work in isolation, which I don’t think it does) would concentrically abduct the hip, isometrically stabilise the pelvis and lower limb, and eccentrically control adduction and internal rotation. The best types of activity to stimulate these actions are going to be weight bearing exercises (Figure 1); (Krause et al 2009).
There is evidence to suggest that the posterior portion of glute med is deactivated with any degree of hip flexion, with the bias for primary movement coming from gluteus maximus (Delp et al 1999). This said, Di Stefano et al’s (2009) study produced similar glute med activation at 30 and 60 degrees hip flexion. Either way, my argument is the same – clams probably aren’t working the structures you intend to target.
Reference: DiStefano 2009 here
Clinical Reasoning
My question to clinicians who regularly use clams is always “why?”. What is the purpose of this exercise? At the moment, I work with an elite athletic population. How often in their training and/or competition do they have to externally rotate a flexed hip in an open chain from a side lying position? Never. Even in standing, I can only think of them opening up their hip to control a ball in mid-air but then they are mainly using hip flexors to activate that movement – something we strictly instruct them not to do with a clam. So now that we can’t think of a transferable example for this exercise, I would ask “why are we doing high reps and sets of an exercise we don’t need to do?”
Problem solving
We have already said that the best exercises for glute med activation are weight bearing exercises and the reason for that is exactly the reason why we shouldn’t try and isolate glute med… in weight bearing, it will work as one part of a complex and brilliant kinetic chain. This was highlighted in a very interesting study recently by Kendall et al (2013) who used a nerve block on the superior gluteal nerve and then performed the Trendelmberg test. Even with a neural block to the gluteal muscles, patients maintained pelvic alignment through the step test, highlighting that in isolation, the glutes alone do not support the pelvis.
One of my preferred, early stage exercises to improve hip control / stability is a single leg isometric movement (figure 2).
The patient is instructed to rest the contralateral leg against the wall for balance only. All of the body weight should be through the standing leg. Explain to the patient that their foot is superglued to the floor, but you want them to rotate their thigh out (encourage external rotation). There should be no movement from the upper body, bum should be “tucked in” with text book posture and they should hold this contraction for 10s, repeat 10 times. I promise, it will burn your glutes towards the end. Try this yourself and pay particular attention to what else happens further down the chain. You’ll see activation of the VMO and the medial arch will raise as tibialis posterior activates too. A brilliant example of the kinetic chain in action.
“Providing the patient is able to single leg balance, any exercise targeting hip control should be done unilaterally”
Now, there are examples in the patient populations where this is not an appropriate exercise. For example, early stage ACL injuries due to the torsion this creates through the femur and tibia. Instead I would adapt the exercise to something that we were all taught very early on in our physiotherapy degree – a simple small box step, placing one foot from the floor onto a step and back onto the floor – where the standing leg is the working leg. If you are strict enough with posture and lumbo-pelvic control, this is great early stage exercise for the glutes and easily progressed into a full step up, step downs, lateral steps, greater step heights etc. (For exercise progression, please see my shameless plug for my recent Model of Exercise Progression). Kendalls (2013) paper that we mentioned earlier, supports this simple trendelmberg exercise for patients with marked hip abductor weakness. Krause et al (2009) found an increased activation of glute med with single leg exercises compared to double leg stance, so providing the patient is able to single leg balance, any exercise targeting hip control should be done unilaterally.
For the non-weight bearing patients there is reasoning to perform these open chain exercises. While we have said we may not be increasing strength, we know that there is some activation occurring within the glutes so we limit an atrophy and maintain neuromuscular activation while the patient is NWB. Refer back to figure 1- the top exercise for glute med EMG is straight leg hip abduction so even with these NWB patients there are more appropriate alternatives to the clam.
Conclusion
Two of the core elements of physiotherapy is the ability to clinically reason and to provide effective exercise prescription. I would encourage people who regularly use any exercise, not just clams, as part of their mainstay exercise protocol to consider exactly why they are using them. I personally don’t think there are many examples where the clam is an appropriate exercise for sports medicine populations. The exception being NWB patients who are unable to control long lever exercises like single leg hip abduction. Therefore, there is an argument that the clam may quickly become an extinct creature.
Yours in sport
Sam
Plinths and Platforms 