Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB.
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Effects of Step Rate Manipulation on Joint Mechanics during Running.
Med Sci Sports Exerc. 2010 Jun 23. [Epub ahead of print]
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Increased step rate = increased leg stiffness. Which will be OK for some of the people some of the time. If you already have high leg stiffness increasing step rate might just push you up above the zone of optimal leg stiffness (ZOOLS) = stress fracture, bone injury. On the other hand, it might form a useful form of therapy for a runner with decreased leg stiffness and soft tissue injury who is dropping below the ZOOLS. Decrease step length, increase cadence =increase leg stiffness in soft tissue running injury; obviously the opposite applies, so perhaps lengthen stride, decrease cadence in patients with bone related running injury.
As you know Ian, running is effectively modelled as a spring mass system- a simple harmonic oscillator. There is a nice JAVA app. here:
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1825.0
Increase the value of K (leg stiffness) and observe what happens to the frequency of the oscillation (step frequency if you like) . I know you'll enjoy playing with it, Ian.
While were on the subject, there are some great resources for anyone who wants to improve their understanding of mechanics to underpin their biomechanics knowledge here: http://www.animations.physics.unsw.edu.au/mechanics/index.html -
Does this study make any reference as to the running distance examined for the study? Or is it solely a study done on the effects of step/strike rates (over a short distance) relating to hip, knee & ankle joint loading forces with association to injury risk.
What is stated may be conducive for long distance road running (i.e. possibly offsetting muscle fatigue/soreness in the marathon as well as reducing the accumulated forces gained from training) but I wouldn't think to be that conducive for shorter distances from a performance perspective... particularly track races.
Putting aside the suggested benefits for injury reduction, I wonder what the implications would be on speed/performance on the whole. I presume strike cadence is a matter of balance (i.e. between vertical/horizontal excursion & energy/forces involved) & would differ between race distances... as well as running technique of the runner.
This brings to mind something I've been thinking about for a while regarding orthotic therapy. Orthotics are commonly seen as a form of injury treatment product but how about a performance enhancement product... i.e. helping reduce ground reaction forces & reducing metabolic cost (reducing muscle tension/work) during a race... but not necessarily used for training (providing an underlying biomechanical issue is not present). I have been thinking of modifying a pair of racing flats with a custom orthotic. Has study been done regarding this area?... this however is probably another topic altogether. -
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Simon,
Glad you have pitched in on this. Annoyingly I can't seem to open the first link properly (the page opens but the java app won't run) - will try again later.
If our current understanding of ZOOLS is correlated with injury as you state above is the following a reasonable summation?
- Runner has history of soft tissue injury. They appear to be taking relatively long steps, showing increased joint kinematics (knee flexion for example) and marked CoM excursion. Potential management: Shorten stride length/increase cadence (thereby increasing leg stiffness)?
In London a lot of 'running technique' coaches seem to have popped up of late. See here for the sort of theories they subscribe to: http://www.youtube.com/user/fitnessfootwear#p/u/6/Jio7DK15Q1E
I have spoken to a few and essentially they give some postural and stride length re-education. Maybe they are onto something with out realising? -
Ian, try updating your java player, if you get no luck I'll e-mail it to you. Otherwise, you're probably on the money; as it seems are your running technique coaches, provided they are spotting those candidates that are too high in their ZOOLS and those that are too low and adjusting accordingly. Is this clinical take home?;)
Maybe they're on to something with realisation. -
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Absolute classic. Bill Murray is a hero.
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No 1 - gutted I missed Ghostbusters
No2 - Simon thanks for the Java demo - it is a really great, simple model.
No3 - Simon thanks for the stiffness paper
No4 - I'm interested in this performance improvement thing - Are we talking about reduction in injury potential and therefore the ability to train harder or actually changing the mechanics of running to be individually more efficient?
It is an area that very much interests me so I will be interested to hear any theories - not that I'll be able to understand all of it probably!
Regards,
Robin -
Robin,
I'm sure I've read a post of Simon's which mentioned an increase in leg stiffness directly improved performance/speed (assuming this individual was still within their ZOOLS for that given activity of course). Can't think of the reference off the top of my head - sure Simon will enlighten in the morning.
Get yourself to Woodland Grange at the end of this month and hear it from the horses mouth: http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=149725&postcount=2 -
Robin,
These two (which are also on the Leg Stiffness thread) discuss the relationship between leg stiffness and performance
IanAttached Files:
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Stiffness - leg power and hopping stiffness + relationship with sprint performance.pdf
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Thanks for the papers
Robin -
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Forgot the reference:
http://biomech.media.mit.edu/publications/Ground_Stiffness_Metabolism.pdf
These guys looked at metabolic cost but the first paragraph talks about Tom Mcmahon's work. -
Am I the only person appreciating the irony of the fact that this thread is talking about "Zones of Optimal Leg Stiffnesss -ZOOLS whilst concurrently discussing Ghostbusters in which Dana becomes possessed by ZUUL, the minion of Gozer the Gozarian?
Sadly,
Robin -
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I reckon Drs Spengler, Venkman and Statz had reduced kleg...
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Thanks for that PDF... I have skimmed through it & it looks very interesting. Some points stated have put a new perspective on the understanding of the topic.
Once I have a closer read I will like to discuss further... particularly on the practical applications of it, which I have been looking into for a while & recently been putting into practice.
If only my ideas had developed at the same time as my body... I would have more time to play around with them. Anyway, better late than never. -
The following are points I found interesting from the previously cited PDF...
View attachment Lower Extremity Stiffness Implications PDF.pdf
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A better a -
Spooner - over 24 hours have passed and the suspense is killing me.
What would a better analogy be?? -
I was going to talk about springs, but changed my mind. I didn't realise I'd hit the send button and by the time I did, it was too late to edit. You'll find out in couple of weeks. You getting there on Thursday? Give me a bell, when you get there. -
Yep driving up after work Thursday night. Beer o'clock.
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The more common and frequently used term is "stride frequency", not "step rate", for the number of running steps/strides per minute. In coaching runners, it is typical for many inexperienced runners to "overstride" or have an increased stride length versus their optimal stride length, so we tell the runners to "chop their stride" and "increase their stride frequency". While this would be expected to diminish the center of mass excursion and decrease joint loading for each running step, one must also consider that the accumulated loading force on the joints per unit of time spent running does not change nearly as dramatically since there are more foot collisions per minute when stride frequency is increased.
Interesting research, however.:drinks
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