originally posted at thebodymechanic.ca in 2012/13 and then updated in 2015. Here is an old post slightly reworked. Please read Eric Meira's post on functional exercise that is just fantastic.
A few years ago found myself defending the lowly clamshell exercise for runners. I was discussing with other physios whether the clamshell exercise was less "functional" than a band walk exercise (where you put elastic bands around your knees/ankles and walk forwards, sideways or backwards). I suggested that both were NOT (or equally) functional but agreed that both had their uses. I can tellyou, I convinced no one :)
The consensus against me was that the clamshell sucked and that the band walk exercise was superior because it was more "functional" for runners. I tried to argue indeed the bandwalk might be a better exercise but not because the Bandwalk was more "functional".
The problem is the word "functional".
What the heck do you mean by 'functional".
When I heard someone say the bandwalk exercise was more "functional" than the clamshell I immediately thought malarky. Because my knee jerk reaction to hearing "functional" was my brain translating this to "movement specificity" or kinematic specificity. Meaning the exercise you are training matches the kinematics (specifically the displacements or joint angle motion) of the athletic task (in this case running).
Using kinematic/movement specificity to judge a Bandwalk or a Clamshell was a no brainer. In terms of function (using the kinematic specificity definition) they both suck. No runner lies on their side and lifts their leg up (e.g. the clamshell) but no runner runs sideways with a bloody elastic band around their knees.
So lets define "functional"
My knee jerk translation of "functional" to being "kinematically specific" is a little narrow.
Function to me means that the exercise has some sort of relevance to the task the athlete hopes to accomplish. Viewing it this way then exercises can be functional or relevant thru a number of different means:
1. Movement specific: this means the exercise task somehow looks like the athletic task it is trying to train. This means your exercise has similar form (due to motor control) to the goal task. Furthermore, it suggests that the neuromuscular recruitment pattern is similar to the exercises (e.g. muscle onsets, offsets, ratios etc) For example, squats are great functional exercise to get out of a chair.
2. Muscle or joint specific: this means the exercise is training similar muscles to the muscles that are being used in the goal task.
3. Velocity specific: this means if your goal task requires you to move fast than you should probably train fast. Exercises are therefore "functional" if they lead to some sort of carryover to the goal task's speed demands. We know that you don't actually have to move fast to get this carryover, sometimes just the intention to move fast will garner improvement
4. Movement direction: if your goal task requires a lot of deceleration than you should probably train the eccentric loading capability during your exercise. For a runner, you might think they have increased hip adduction during the impact phase of running which occurs for less than 100 milliseconds. Thus you should probably train this deceleration ability over that specific time frame for it to be functional.
5. Context: the exercise should be similar to the context of the goal task. The context might the exercises relationship to gravity or even to a societal or performance context (e.g you train to shoot free throws while people are screaming at you).
So what is more functional the lowly clamshell or Bandwalks?
Trick question! You can't answer this. There is no functional scoresheet. The better question is what is more useful to the runner or athlete. You have to be able to answer why you are prescribing an exercise in the first place. What is your intention with each exercise? What do you hope to accomplish? If you prescribe an exercise because it is "functional' than this is just begging the question. Functional isn't enough it has to lead to some specific gain. And if you think it is functional why is it beneficial?
A case example in the limits of functional justification: The BandWalk
I think most people would argue that the Bandwalk is more "functional" for the runner because it appears to train the muscles used in running in a more similar manner kinematically and more of the muscles that a runner uses when they are running.
But does it really do this? How much of the previous "functional" components does the band walk satisfy?
Movement Specificity: No runner runs with a band around their knee, they don't run sideways or backwards. On its surface it certainly isn't very similar in terms of joint angles and displacements. If you think movement specificity is important or practice makes perfect than training a movement that is so dissimilar to running can't be justified in this manner.
Movement Direction: Lateral band walks do not train the hip abductors in the manner that they are used during running. Eccentric control occurs over very short period under high impact loads when running. Band walks are extremely dissimilar to this. They are slow. They have an external force that is extremely different to the force vectors that create joint torques during running. We don't satisfy a movement specificity or even a velocity specificity argument. Considering this is the Bandwalk still functional?
Context? The band walk looks better than the clamshell that is for sure. The athlete is standing and shifting weight. But are they standing a shifting weight like a runner shifts weight? Nope. Is just standing and having weight shift enough to make it functional? Why not do dumbbell curls while standing and shift your weight back and forth.
Motor Control: No way. Doing bandwalks are nothing like the motor patterns used in running. Timing would be way off, no impact, no feedforward activation of muscles to damp vibration, hardly any storage of elastic energy. Do you think the "extensor paradox" occurs during a band walk. Not a chance. These two tasks are completely separate beasts. There is no way you can argue you are engraining some motor pattern during the band walk to enhance running.
Is the BandWalk Garbage?
Nope. It can certainly help runners. I rarely use it but I still think it is reasonable for a runner to train with it. Because it satisfies our simplest category of "function". It trains a group of muscles that runners need. These exercises build the capacity of those muscles and this probably transfers over to increased mechanical efficiency and maybe even some injury protection. However, if you think that it is functional enough to actually change a runners form than you might end up getting some poor results.
The problem with this last justification for strength coaches and rehab people is that it is too simple.
As therapists we want to think that we have some special knowledge about special exercises. We don't. There are no special exercises. Train hard, train smart, get strong, build power, build tolerance, build capacity, build endurance, build the ability to absorb load, dampen vibration, produce strength at all ranges etc. Have a generalized, good all around program and you will probably have good results. Maybe throw in some assessments to see where your athlete is lacking and then train the hell out of that and you will do better. But, there are no running exercises. And that is contrary to what both the research suggests and gurus suggest. Pick an expert in a field of strength and conditioning (powerlifting, olympic lifts, corrective exercise, pilates, yoga, core stabilizinationists etc) and they all swear by their success with runners. They are all probably right - thus no specific running exercises.
OK, so is the clamshell better?
No way! The clamshell sucks most of the time. I used to hate clamshells because I thought I was better than that. I thought runners should never do it. I thought it was remedial and "non-functional".
The clamshell works fewer muscles, has the person lying down, looks kinematically different than running and doesn't satisfy many of the functional principles I laid out earlier. BUT, it does train some muscles substantially different than the bandwalk. This is where it can be a useful exercise.
The clamshell sees the hip flex to 90 degrees and has the patient externally rotate the hip. At 90 degrees, because of changes in the line of pull of many hip muscles (GMax, GMed, Piriformis) the only muscles that externally rotate the hip are the deep external rotators. So training the capacity of these muscles might carryover to running.
I used to abhor the clamshell. Then I started testing more runners with the clamshell. A number who tested strong in many positions would tremble during the clamshell. Crazy, they had a lovely one leg squat, strong hip abduction but had trouble with 10 or 15 clamshells. What does that tell me? Such a massive deficit in function. Would you suggest clamshells here or something to address that specific movement? This seems like a case where I would suggest clamshells. If a runner can't do them I would want to address that deficit. I sure can't say if it is problem but if an athlete can't do something so simple, in a muscle group relevant to performance, then perhaps I should address it.
But, do I want to see every runner doing them as part of a "functional" program. Of course not. They suck for that. This is a case a where the exercise prescription is "functional" because it addresses a specific limitation in a specific runner.
OK. What do I suggest?
I have no exercise that addresses all of the components of "Functional" but that's why runners should get a comprehensive program.
If I have a bias I lean to training "Comprehensive Capacity". This means you train runners like they are athletes. Big multijoint-compound exercises that train strength, high load power (e.g cleans), low-load power (plyometrics), variable range (not just mid range but end range and weird stuff) exercises and unilateral exercises. The thing with the word "functional" is that is so broad to be meaningless to justify an exercise. Choose exercises based on some other specific capability of the neuromuscular system you hope to improve.
An aside: If you train "comprehensive capacity" and have a well rounded training program do you really need to do in depth assessments? Don't your exercises become your assessments? Or your exercise regime is so well rounded you address everything an assessment might tell you.
The Key Question: Why are you training what you are training?
For runners, I only think that we are training the muscle, joint, tendon and nervous system's capacity to tolerate stress that running imposes. This makes runners more powerful, mechanically efficient and may make them less injury prone.
Do exercises help change running form?
This is seems to be the underlying idea behind an exercise that kind of looks like running (eg. the clamshell). That training in that manner will improve your running form. But there is some evidence to suggest that this does not occur (Willy 2011). We probably aren't training form. We aren't correcting the biomechanics of running by choosing certain exercises. We aren't engraining some motor programs that carryover to running. If you want to do any of these things you have to do that while running and with some form of feedback. Our bodies are not puppets where muscles can be tightened or loosened to obtain some different posture or form. That is a motor control skill not something that changes with other exercises.
So why are you prescribing the exercises you prescribe for your runners?
Please let me know what other rationales are out there. I don't think this brief article really addresses everything
This discussion was also quite serendipitous. I was just finishing a pictorial post of bunch of hip exercises that people can use for their patients. The pictures are all high quality and the idea is that you download them and put them into handouts or your website and what not.