secondly with the introduction of ‘ torsional restraint ’ using torsion bars ( Adidas and Nike ) or a rigid block under the medial arch ( Asics ).
Terra , a shoe that used a new lightweight midsole material called phylon .)
The running boom of the 1970s , spurred on by the USA ’ s Frank Shorter ’ s victory in the 1972 Munich Olympic Marathon , got the world moving , including many people who had spent sedentary years on the couch . Running thus quickly became a commercial business opportunity . Meanwhile , in an attempt to assist the transition from couch to road and distance , the medical profession introduced the concept of jogging as a healthier style to minimise impact and injury .
This was an attempt to combine the walking and running movements by landing on the heel and transitioning to the forefoot , then pushing off with the big toe . The doctors of the time saw this a means to reduce the large number of knees , hip and back injuries being presented when generally overweight and untrained people moved from the couch to the road . Of course , they also recommended this mixture of running and walking , because these people initially did not have the cardiovascular fitness to go long distances without breaks .
Increasing Heel Heights
At roughly the same time , Nike introduced the Tailwind shoe in 1979 , the first shoe to have air pockets to provide cushioning , and of course , the depth of the heel had to be increased to accommodate the air pouch . Cushioning became the catchword of the time , and since jogging was heelto-toe , the focus was on putting design elements into the heel , as the new main point of impact . In effect , manufacturers overlooked the basic running mechanics in favour of commercial interests of running novices !
The Nike Max ( 1 ) had a semi-exposed heel air pocket which required a still greater heel height , and Asics followed the trend with its gel cells across most if its South African range . As the need for cushioning was deemed to increase , the stack height of shoes also increased , which then also forced more people into a heel-toe action . The heel to midfoot drop also increased to staggering measures . For example , the Asics Gel-Kayano 15 had a massive 33mm heel stack height to an 11mm midfoot , providing a drop of 22mm over a 150mm length , which meant a 14.7 % incline of the foot .
The problem was that the greater the heel height , the greater became the number of knee , lower leg and hip / back problems . Clearly this kind of drop was impacting on spine alignment as the body reacted to standing in a sloping shoe . The various shoe manufacturers addressed this in two manners , first by increasing the cushioning still further , and
While these reduced the ability of the shoe to twist , this new unnatural rigidity together with the high drop from heel to ball of foot reduced the foot ’ s ability to flex at the ankle . This resulted in many runners turning their foot outwards to give greater flex – this is exactly what weight trainers do when they perform deep squats – but the unnatural alignment of the knee added more knee and hip injuries , and the injury chain entered a viscous circle . Also , an additional challenge of high drops and rigidity was the increased pressure placed on the metatarsal heads of the toes – and no surprise that there was a surge in metatarsal injuries as well .
Driving Backwards
The fact is that walking is a heel-toe action , but a natural distance running action is a ball of foot landing with a slight forward lean , so that landing is just ahead of the centre of gravity . Momentum carries the centre of gravity over the landing point and then the heel kisses the ground . That movement happens without energy , as it ’ s pushed by gravity from the lean , and then the perputium of motion comes from the forefoot driving ‘ backwards ’ into the ground , which pushes the body forward . The key here is that distance running is about driving ( foot and elbows ) backwards , and not about putting a foot forward . For this reason , anyone who has a heel-strike with a straight leg ahead of the centre of gravity is actually stopping their progress , not assisting it .
Also important is that flexibility matters . The amount of flex of the lower leg compared to the foot is related to the stiffness or stretch available at the calf . It is of note that most elite distance runners have a long spindly calf , and they are able to flex their foot and ankle to land in a rolling way that allows a near heel-strike at low speeds . However , as they speed up , they will move to a forefoot landing , and this results in ‘ training ’ the calf muscle , which will become stronger and therefore shorter and bulkier ( more shaped ).
Next Month : In part 2 of this column , Norrie will dive further into the effect on shoe development by commercial interests and rivalries , as well as further technological breakthroughs .
About the Author
Norrie represented Scotland and Great Britain in numerous ultra-distance events , then represented South Africa in triathlon . He is a World Athleticsaccredited coach and course measurer , and travels all over the world to work on events , including the Olympics , where he has been part of four Olympic Marathon measurement teams . He has been appointed by World Athletics as Technical Delegate to a number of the world ’ s leading Label events in Africa , Asia and the Middle East . He has authored two books ( Everyman ’ s Guide to Distance Running and Every Beginner ’ s Guide to Walking & Running ), and counts 20 Comrades medals amongst his more than 150 ultra-marathon medals , as well as multiple wins at distances from 100km to 1000km . You can read more from him at www . coachnorrie . co . za .
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