In part 1 I told you a story about changing movement patterns, and now let’s cherry-pick some of the science to back up my claims. I will use a few studies from the same research group, focusing on running and knee pain (patellofemoral pain).
Willy RW, Davis IS (2011) The effect of a hip-strengthening program on mechanics during running and during a single-leg squat. J Orthop Sports Phys Ther. 41(9):625-32.
The first study is a study where the subjects got a training program (three times a week for six weeks) that included “typical” hip strengthening exercises and a single leg squat, with the focus on neuromuscular re-education (using mirrors and verbal feedback). This intervention did improve the single leg squat mechanics, but did not alter the running mechanics.“These results suggest that hip strengthening and movement training, when not specific to running, do not alter abnormal running mechanics.”
So you get better at what you practice. You practice single leg squats, you get better at single leg squats. You do not practice running, you don’t alter the running mechanics. But then this group did a really cool study where they did exactly what was necessary: attempting to change the running pattern in real time.
Noehren et al (2011) The effect of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome. British journal of sports medicine, 45 (9), 691-6
From the abstract:
“Ten runners with PFPS participated in this study. Real-time kinematic feedback of hip adduction (HADD) during stance was provided to the subjects as they ran on a treadmill. Subjects completed a total of eight training sessions. Feedback was gradually removed over the last four sessions. Variables of interest included peak HADD, hip internal rotation (HIR), contralateral pelvic drop, as well as pain on a verbal analogue scale and the lower-extremity function index. We also assessed HADD, HIR and contralateral pelvic drop during a single leg squat. Comparisons of variables of interest were made between the initial, final and 1-month follow-up visit.”
“Gait retraining in individuals with PFPS resulted in a significant improvement of hip mechanics that was associated with a reduction in pain and improvements in function. These results suggest that interventions for PFPS should focus on addressing the underlying mechanics associated with this injury. The reduction in vertical load rates may be protective for the knee and reduce the risk for other running-related injuries.”
So the only ‘exercise’ they did was running on a treadmill, with real time feedback about hip adduction. This caused: “significant reductions in HADD, contralateral pelvic drop, pain and the LEFI.” Also, “these changes were maintained at the 1-month follow-up and partially transferred to the single leg squat.”
That last thing is something very interesting: there is a partial transfer of the skill to the single leg squat, without practice or instruction of this movement. I’ll get back to this a bit further on.
And, let us not forget, the gait training “resulted in a significant reduction in pain, as well as improvement in function. On average, an 86% reduction in pain was seen.” This is important, because although very logical, the result could also have been a change in gait mechanics without reducing the pain. The relationship between mechanics and pain is not proportional. A lot of people have less then optimal biomechanics and do not experience pain.
Now, there still was one big problem with this study, it uses a lot of expensive technology, and it takes a lot of time to install all the markers on the patient. Could you also have these same great results with a more practical and affordable setup? So these researchers tried to answer this question:
Willy RW et al (2012) Mirror gait retraining for the treatment of patellofemoral pain in female runners. Biomech 27(10):1045-51
This study was almost the same as the previous, except that they used the common man’s real time feedback: a mirror and judicious vocal cords.
“Ten female runners with patellofemoral pain completed 8 sessions of mirror and verbal feedback on their lower extremity alignment during treadmill running. […] “During the last 4 sessions, mirror and verbal feedback were progressively removed.” […] “Subjects reduced peaks of hip adduction, contralateral pelvic drop, and hip abduction moment during running.” […] “Skill transfer to single leg squatting and step descent was noted. At 1 and 3 months post retraining, most mechanics were maintained in the absence of continued feedback.” […] “Subjects reported improvements in pain and function and maintained through 3 months post retraining.”
Really good results, maintained 3 months after the intervention! Of course there are ‘limitations to these studies’ and ‘further research is necessary’. And of course I’ve cherry-picked the studies that back up my case.
Let me highlight one surprising finding: there was a skill transfer from the gait training tot the single leg squat and the step descent. This is very interesting, because it kind of contradicts my point. I’m trying to ‘prove’ that you need to train very specifically, and here we see a non-specific training effect. There is a skill transfer to a movement that is not practiced and without any instruction or feedback.
Some kind of deeper learning seems to be involved here. Maybe it is due to the great amount of repetitions during the running retraining, relative to doing these exercises. Also, the effects at 1 month and 3 months suggest there has been a learning, and this only after 8 gait training sessions.
In the future I hope the write about skill transfer that is non-specific. This study uses the very simple activity of running, that is relatively easy to change. But imagine you have to specifically address and train all the locomotive movements that occur in a basketball game. This is impossible, so we have to rely on some non (or less) specific learning to occur.
So, for all you therapists and trainers out there, it is time to work on your ‘judicous vocal cords’. Learn to evaluate movement in real time, and how to change it.
And remember: if you want to change movement patterns, you have to change movement patterns, directly and specifically.
Is there no place for exercise? Of course there is, but that’s for part three of this series.
Thanks for reading and feel free to comment or discuss!
Pieter