This post is a link to a pdf ebook on the presentation I gave for the MSK-Plus course November 25, 2012. Below I give a brief intro into the confusion that surrounds these topics. If you note a huge amount of uncertainty, a whiff of grey and lack of simple answers than your interpretation is correct.
The pdf file is form footwear and footstrike running mechanics ebook nov20 2 2012.
We can change the following variables of running:
1. Kinematics or changing the position of the body (e.g. trying to not let your knees collapse inwards) or the timing of events (e.g number of strides per minute)
2. Footstrike style
3. Footwear: barefoot, "barefoot shoes", minimal shoes, traditional cushioned shoes with an attempt to "correct" something
We also hope that changes in mechanics will occur. Some variables that may be related to injury:
1. Rate of impact loading
2. Joint forces
3. Muscle loading, timing or activation levels
4. Joint kinematics
We assume that making one change will result in positive changes in other variables. The big assumption is that we know what is bad in running. It sounds so simple, but in practice it is not. Especially when we deal with something like pain and injury.
What you will see in the attached e book is that nothing is that simple. Changes in many variables related to running often don't result in the "positive change" in some running variable that we hope for.
Below is a brief introduction to the modifiable variables and their relationship to running mechanics and to a less extent injury. The attached pdf file goes into a little more detail.
Modifiable variables during running
Run barefoot or run minimal
I wish it were this simple. We have some data suggesting that some barefoot runners will run with a forefoot strike, reduced stride length and other changes and thus they will have a decreased rate of impact loading. We have no data suggesting that making this change reduces injury and the link between rate of impact loading and injury is a wee bit murky. We also have a number of research studies showing that just changing to barefoot is not sufficient to result in decreases in the rate of impact loading.
In Lehman's terms, we may want to be cautious about any blanket statements
Lose the cushioned shoes and run in flats
I do this but I certainly don't think its the answer for everyone. I also run in cushioned shoes because I think variety is important. As for mechanical changes when going to flats there is not a lot of robust data out there that supports this in terms of biomechanics. The assumption is that if you lose the heel on your shoes and the cushion you will automatically start to run with a softer gait. Again, this is not supported in the literature and research exists showing increases in rate of loading and joint loading with racing flat like shoes. Again, we need to reserve our blanket statements.
Convert from a heel strike to a forefoot or midfoot
The assumption is that heel striking is bad. Again, not strongly supported in the literature. Research is mixed with some work showing decreases in the rate of impact loading when going to midfoot or forefoot but we also have conflicting work showing the opposite. Again, blanket statements are not cool. The epidemiological research is also in its infancy, is correlational in nature and correlation data sucks for implying causation.
Decreasing stride length and increasing stride rate
This modification may have the most support and may be a common variable in other interventions. For example, I think that someone might strike the ground with a forefoot strike and have a large rate of impact loading if they have a long stride, while another individual might convert to a forefoot strike and also decrease the length of their stride. We might initially conclude that the forefoot strike was the variable that resulted in the decrease in the rate of impact loading but really it was just having a shorter stride. This may also be a factor with barefoot interventions. Barefooters tend to stride shorter...maybe those barefooters with higher impact loading rates failed to decrease their stride length. BUT, and there is always a but, we do have a well designed study that showed no changes in impact loading when increasing stride rate (Giandolini 2012). I am not even sure how that is possible but that was their finding.
The ebook does not touch on this but these would be things like increased frontal plane projection angle, hip valgus, hip internal rotation, pelvic obliquity, lack of hip extension, increased anterior pelvic tilt, prolonged pronation, lack of pronation, uneven arm swing, lack of trunk rotation etc. Surprisingly, we have very mixed data on this. Even the biggies like increased hip internal rotation and hip valgus. Sure there is some correlational data that shows that some runners with knee pain have greater amounts of hip valgus when compared with controls but the predictive data is much weaker. We also have data showing no relationship between assumed gait flaws and any current injury.
We don't know if pain begets gait flaws (e.g hip weakness) or if the biomechanical flaw caused the pain. What might surprise you is that we can often rehab a patient, get them running injury and painfree and they still present with the initial "biomechanical flaw". My concern with assuming that some biomechanical variables are faulty is that this views the body as being inherently weak and we forget about its amazing variability and strength. You will see lots of runners with huge amounts of hip valgus/knee collapse. You will shudder in horror at this. But sometimes that is just that person's little idiosyncrasy . They have always done it and they have adapted. You will try to fix them under the assumption that they are faulty. But this a massive assumption.
I am working on a large post on the kinematics of gait and injury. I will go into a lot of detail on this topic
OK. So everything is grey. What do I do?Warning: Opinions ahead.
Gait modifications can help with an individual in pain: We have good data that a slow return to running with modifications to form can help. I don't necessarily believe that this is always related to biomechanics in the sense that we are changing mechanics to be closer to an ideal. I think we are changing mechanics and it is the act of change that is important. Variability and novelty is important to me in all my rehab programs. Changing your gait loads the body differently and is also different for the brain. Different gait patterns may avoid certain physical stressors on the body and may not activate our pain neurotags because of the novelty. Further, most gait re-training is a slow, gradual return to running. This exploits our innate adaptive abilities.
How should people run if not in pain?
Please note, the suggestions below only relate to running form. There are a lot of things we can do to reduce the risk of injury. Below is not comprehensive.
If I have to go out on limb I would suggest four things:
1. Novelty and variety: different shoes, different surfaces, different speeds, different distances.
2. Check your cadence: if you are running a five minute kilometer than your steps per minute should be greater than 170 per minute. If you are "loping" and don't have a quick turnover consider increasing your cadence. What you are trying to avoid is landing with the foot extremely far in front of the body and this is associated with a close to straight knee at footstrike
3. With reservation and many exceptions, a midfoot to forefoot strike with the occasional heel strike thrown in: this one is tough for me to say and I have some hesitancy. If you are novice runner I would probably suggest running with a midfoot strike. I think the bulk of the research suggests that running with a midfoot strike is the way to go. I know that there is research suggesting heel striking is fine especially if it is not associated with overstriding. I totally get this. As I said, I have some hesitancy - I treat a lot of heelstriking runners and would not consider changing their gait so this suggestion is obviously not a blanket for everyone. Many heelstrikers have their feet land close to their body and their gait is soft and quick. However, I also think that thinking about midfoot striking will also help with your cadence. Last, for slower runners (10 minute miles) I doubt footstrike matters as much. One caveat, I also think many runners would benefit from using different footstrikes during the same run provided their cadence is not too low. This is consistent with my views on variety.
4. Gradual increase in running or in changes in form. This one is obvious. The body adapts over time we just have to give it some time to adapt.
My bottom line
I would be hesitant to change things about someone's form if they have no injury or past history. If they have had a series of past injuries or currently have an injury this is where I think we can help the most with changes in form. What you will see in the e-book is that there are so many exceptions to our commonly held beliefs about certain running related variables. These exceptions make me quite cautious in just trying to change runner's form when you don't actually know what you are causing when you try to make a change. I am lucky in that I have access to 3D motion capture equipment. I can see what happens with different changes in form. But I don't have force plates and I can make no comment on changes in joint loading or impact loading. And the "running expert physio" dude with one camera (or who just eyeballs a runner from behind) can't say what changes in force (e.g rate of impact loading are occurring) and is also probably wrong about a runner's kinematics should be a little cautious in just making changes based on one or two cherry picked research papers. What the research in this e-book shows is that many changes we assume to be good end up resulting in elevated levels of impact loading or joint loading. Thus, I advise caution.