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Sep 2013
3:25pm, 17 Sep 2013
3,295 posts
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daviec
And also that efficiency isn't the be all, even for marathoners and longer.
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Sep 2013
3:50pm, 17 Sep 2013
4,481 posts
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jonp
Paul, you are missing that walking and running are bio-mechanically different, so it's not a simple case of a linear transition. At some point a person's biomechanics (and the physics involved) changes when they transition from walk to run. But from slow jog to run, the biomechanics is basically the same...
With a walking gait, you don't go airborn; you lift your body up (to it's maximum at mid-stance position), and then it rotates down and forward on to the front leg creating a stride-length.
With a running (slow jog right through to sprint), you go airborn; at midstance your body is at it's lowest position, it lifts up and goes ariborn after this point, and your whole body drops down onto a supporting leg. Essentially, the stride length is roughly relative to the distance that your body is moving through the air.
So walking and running are almost opposites biomechanically. There is no biomechanical advantage of a forefoot strike with walking (because there is no quick elastic recoil requirement). With running there are arguable benefits for forefoot landing due to elastic recoild benefits (at slower speed these benefits are reduced though)
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Sep 2013
5:19pm, 17 Sep 2013
3,949 posts
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paul the builder
I think I agree, actually. so I was wrong, or at least my logic doesn't work when it starts with walking at the slow end.
If we asked everyone to run, but at the very slowest pace that they could, and still be running - do you think there would be considerably more people landing on their heel, than there would be if they were asked to run hard and fast? If so, the essence of my point remains valid.
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Sep 2013
5:32pm, 17 Sep 2013
21,015 posts
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HappyG(rrr)
Ooh, is this thread alive? Used to get some fantastic spats in here, back in the day!
Not everyone heel strikes (as you pointed out paul, in earlier post) at marathon distance, even at the very successful top end of the sport. So it must be possible to be a mid or forefoot striker and still succeed at marathons, whether it's because of efficiency or not.
FWIW, I think there's something about safety and resilience as a measure, certainly for mid pack runners that most of us are. I don't know if this is called efficiency or if it conflicts with what people mean in here by efficiency. If efficiency just means going as fast as you can expending minimum energy, then heel strike may be "efficient".
But if you break your leg after 6 months of doing it and never run again, then it's not very sustainable! I'd like to know how to run safely, for as long as possible. That would count as effective, even if it isn't efficient, and I'd rather have some of that, thank you very much! :-)G
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Sep 2013
6:26pm, 17 Sep 2013
782 posts
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Canute
I agree with Jon that walking and running are different. However, both the observational evidence of what runners to do, and measurements of oxygen consumption suggest that heel strike is more efficient at low speeds. Theoretical considerations are consistent with this.
When estimating the energy costs of running, capture of elastic energy in the Achilles by forefoot striking is only one of several factors to consider. As Paul implies, trying to visualise the various contributions to energy costs when running is not easy. But let’s try.
There are three major energy costs when running: getting airborne; braking and repositioning the leg during swing phase. For a given time on the ground, the amount that the stance foot gets left behind is greater at higher speed because the body moves further forward during that period of time on stance. Therefore repositioning costs will be greater. Also for a given time on stance, braking cost will be higher at higher speed because the line form COG to point of support at foot-strike is more oblique. Therefore, at higher speed, it is essential to minimise the time on the ground. However this requires more airborne time and hence greater elevation cost. This cost of getting airborne can be somewhat reduced by increasing cadence and also by maximising capture of elastic energy in the Achilles tendon. In contrast, at slower speed, we can afford to spend longer on stance because leg repositioning cost and braking cost are less severe. Under these circumstances, the penalty from failing to capture elastic energy in the Achilles tendon is likely to be relatively less important than other costs, so tensioning the calf muscles is more likely to be a waste of energy. Though not that even at slow speed, capture of energy in the tendons of the large muscles of the thigh is still likely to be of some importance in capture a portion of both braking energy and gravitational potential energy. Note also that the tensioning of the Achilles might be more dependent on soleus than gastrocnemius at slower speeds and this is likely to be less efficient at capturing energy than gastrocnemius
However, balancing all these contributions to cost is complex, so in the end the strongest reason for believing that heel striking is more efficient at slow speed is the evidence for studies that compare oxygen consumption between different foot strike styles.
Happy G,
the question of which style creates greater risk of injury is not clear. The risk of metatarsal stress fracture and the risk of Achilles tendonitis are probably greater for forefoot strike. However, the stress at the knee might be greater with heel strike. At this stage there is little clear evidence regarding the relative risk of injury for heel strike v fore foot strike.
I think the overall conclusion is that for recreational distance runners, there is little to be gained by changing from your habitual style unless you are getting injured and the injury can be related to your foot strike.
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Sep 2013
8:56pm, 17 Sep 2013
16,825 posts
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FR
Walking is more efficient than running 
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Sep 2013
8:59pm, 17 Sep 2013
19,039 posts
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eL Bee!
Not if you want to achieve a 2:30 marathon!
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Sep 2013
9:00pm, 17 Sep 2013
16,827 posts
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FR
True, eL Bee, but in energy terms a walker with consume less than a runner over 26.2 miles.
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Sep 2013
9:03pm, 17 Sep 2013
19,040 posts
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eL Bee!
On which case lying down in bed is even more energy efficient, but THIS is a thread about running efficiently
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Sep 2013
9:05pm, 17 Sep 2013
16,828 posts
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FR
To be fair, the transition from heel to mid to fore appears to occur at a pace that most can't sustain for a marathon?
But I really don't see the fixation about foot striking...
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