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Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. Effects of Step Rate Manipulation on Joint Mechanics during Running. Med Sci Sports Exerc. 2010 Jun 23. [Epub ahead of print]
Quote:
Abstract
PURPOSE:: The objective of this study was to characterize the biomechanical effects of step rate modification during running on the hip, knee and ankle joints, so as to evaluate a potential strategy to reduce lower extremity loading and risk for injury. METHODS:: Three-dimensional kinematics and kinetics were recorded from 45 healthy recreational runners during treadmill running at constant speed under various step rate conditions (preferred, +/- 5% and +/- 10%). We tested our primary hypothesis that a reduction in energy absorption by the lower extremity joints during the loading response would occur, primarily at the knee, when step rate was increased. RESULTS:: Less mechanical energy was absorbed at the knee (p<0.01) during the +5% and +10% step rate conditions, while the hip (p<0.01) absorbed less energy during the +10% condition only. All joints displayed substantially (p<0.01) more energy absorption when preferred step rate was reduced by 10. Step length (p<0.01), center of mass vertical excursion (p<0.01), breaking impulse (p<0.01) and peak knee flexion angle (p<0.01) were observed to decrease with increasing step rate. When step rate was increased 10% above preferred, peak hip adduction angle (p<0.01), as well as peak hip adduction (p<0.01) and internal rotation (p<0.01) moments, were found to decrease. CONCLUSION:: We conclude that subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries.
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.
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.e...ics/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.
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.
Matthew, this is a subject which I am very interested in. Can I suggest that you read this review paper first as it may answer many of your questions. Then, I should be more than happy to discuss this further.
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)?
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)?
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?
Ian, try updating your java player, if you get no luck I'll e-mail it to you.
Will update it tonight squire - as soon as I have finished watching Ghostbusters.
Quote:
Originally Posted by Simon Spooner
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?
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
__________________
I see you girls checkin' out my trunks
I see you girls checkin' out the front of my trunks
I see you girls lookin' at my junk, then checkin' out my rump, then back to my sugarlumps
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.
I'd love to but I only have the time and budget to do 1 other thing besides the x ray course you suggested and I plumped for Craig's Biomechanics Bootcamp. Hopefully there will be some similar discussions there.
Thanks for the papers
Robin
__________________
I see you girls checkin' out my trunks
I see you girls checkin' out the front of my trunks
I see you girls lookin' at my junk, then checkin' out my rump, then back to my sugarlumps
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?
Both. In general researchers have increased leg stiffness by manipulating surface stiffness. When we run on a compliant surface, the surface and the leg act like two springs in series. So we have an effective spring stiffness for the system made up from the stiffness of the leg "spring" (kleg) and the surface "spring" (Ksurf). The body wants to maintain centre of mass (COM) kinematics, i.e displacement, frequency of oscillation etc. so in response to a compliant surface it will increase the leg stiffness to compensate for the decrease in surface stiffness to maintain constant COM kinematics. Increasing leg stiffness in this way increases the elastic energy storeage and return, metabolic cost is reduced.
Quote:
Originally Posted by RobinP
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!
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
__________________
I see you girls checkin' out my trunks
I see you girls checkin' out the front of my trunks
I see you girls lookin' at my junk, then checkin' out my rump, then back to my sugarlumps
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
Know this, when I first thought of the acronym "ZOOLS", I had the film Ghostbusters in my head. Like I said earlier: film!!!!
Matthew, this is a subject which I am very interested in. Can I suggest that you read this review paper first as it may answer many of your questions. Then, I should be more than happy to discuss this further.
Hi Simon,
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.
Big sigh... it seems this coach has taken a few pages from Professor Lieberman's premise in justifying how we apparently evolved to run (I'll say no more).
Quote:
Originally Posted by Ian
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?
Yes, I don’t think their reasoning is the same... it is a different wavelength. So I've heard so many times before from Pose/Chi running convertees & barefooters... it is the fear of having that braking affect when (as they put it) "striking ahead COG". I think they believe it is an epidemic & that those of us who don’t follow their methods are striking too far ahead & thus subsequently are deemed ‘brakers’.
As greater forces are imparted to the body, greater resistance to movement is needed in order to produce controlled movements. The amount of stiffness required has been reported to increase with the demands of the activity (Arampatzis et al., 1999; Farley et al., 1991; Granata et al., 2001; Arampatzis et al., 2001a,b; Kuitunen et al., 2002; Seyfarth et al., 2002; Stefanyshyn and Nigg, 1998).
Arampatzis et al. (2001a,b) studied subjects rebounding from a drop landing, and reported that as rebound velocity increased, an associated increase in lower extremity stiffness was observed. Farley et al. (1991) observed that vertical stiffness increased with increased velocity as subjects performed one legged hops on a treadmill.
I suppose the above point helps support why in part that plyometrics are beneficial for runners. It may also support the idea of running with an added weighted extremity (i.e. ankle weights)... adding weight to the extremity would contribute to greater force imparted to the lower limb as well as invoking greater resistance to movements (i.e. heel kick during swing phase). Both methods would seem to be conducive to adopting & adapting to greater degrees of stiffness of the lower limb.
Quote:
Stiffness also appears to be related to stride parameters. It has been shown that, for a given velocity, a longer stride length is associated with lower stiffness (McMahon and Cheng, 1990; Farley and Gonzalez, 1996; Derrick et al., 2000).
During normal running, Farley and Gonzalez (1996) reported subjects who naturally ran with a greater stride length, exhibited decreased leg, and vertical stiffness. Therefore, while increasing the stride length of a runner may be beneficial to performance, it should be understood that this alteration may decrease the vertical stiffness of the runner, which could negatively influence velocity.
This didn’t seem to resonate with me. I would have thought the opposite, that being... a longer stride length would induce greater leg stiffness as a result of the increased demands of the activity i.e. higher resistance needed. Maybe the key point here is... “for a given velocity, a longer stride length is associated with lower stiffness”... as a result of overstriding (??).
Quote:
Kerdock et al. (2002) reported that an increase in lower extremity stiffness, induced by having subjects run on softer surfaces, was associated with greater running economy.
I suppose a good analogy here would be that of tyre pressures for your car... tyres with little pressure (lower stiffness) would be less economical than tyres with high pressure (higher stiffness) in regard to petrol economy.
Quote:
Stiffness was not directly calculated in their study. However, compared to the injured subjects, the uninjured group demonstrated reduced peak vertical ground reaction force values, in the presence of similar knee flexion, suggesting they may have been less stiff. On the other hand, it has been suggested (Granata et al., 2001; Williams et al., 2003, 2001) that too little stiffness may allow for excessive joint motion leading to soft tissue injury.
I wonder if this should have implications on stretching routines for runners... particularly before the event. I have read in the past that stretches (in particular static stretches) were not conducive before a race. Thus stretches may have an adverse impact on the state of lower limb stiffness.
I suppose a good analogy here would be that of tyre pressures for your car... tyres with little pressure (lower stiffness) would be less economical than tyres with high pressure (higher stiffness) in regard to petrol economy.
Spooner - over 24 hours have passed and the suspense is killing me.
What would a better analogy be??
How do you know "a" was for analogy?
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.
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.
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.e...ics/index.html
The idea that increases in "step rate" can be beneficial for many runners is nothing new. This has been a coaching technique for distance runners ever since my high school running years (early 1970s).
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.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Effects of step rate on running mechanics
(I'll say no more).
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