Intro:
Did you know that just in our two feet we have 38 muscles and tendons, 214 ligaments, 52 bones, and all wrapped up in this amazing ‘stuff’ called fascia?
We are a fantastically well-put-together machine, designed to do things in ways to optimise our natural gifts. So, when we are looking to improve our running and we search for ‘the secret to performance running’ we find it in the phenomenon known as the Stretch-Shortening Cycle (SSC).
SSC:
The SSC occurs in the muscles and tendons (and possibly the fascia) of the lower limbs, by contracting quasi-isometrically. This simply means that they produce the power for the foot to hit and lift almost simultaneously on each strike. This whole contraction happens in around 0.5 of a second and is one of the key reasons elite runners have such high strike rates (98 steps per min). Moreover, this contraction can produce nearly 50% of the forward propulsion in running when athletes are strong, fit, and at optimal weight.
To explain this ‘quasi-isometric muscle action’:
· Isometric muscle action - the muscle contracts without any joint movement, so it is held static while under load.
· The quasi (partly/ almost) means we have a sort of static or stiff contraction but only almost so…we still have a limited, but not a great deal of joint action – understandably, not the easiest concept to absorb!
To experience this quasi-isometric contraction, try;
Putting the weight on your heels and jumping up and down
Put the weight into the balls of your feet (the place you would land if you were skipping) and bounce up and down quickly (see video below).
https://www.youtube.com/watch?v=947ZuH10R_M&t=7s
I came across this thinking when speaking to the late Professor Craig Sharp while doing my postgraduate degree at Brunel University. Prof Sharp originally came from a veterinary science background and later became a leading figure in Sports Science. This unique background gave him great insight into the human and animal sciences.
In running it was traditionally thought that muscles lengthen ie. work eccentrically as the foot hits the floor, and muscles shorten ie. work concentrically as the foot pushes off. However, Prof Sharp pointed out, “recent evidence from human research, and experiments on animals show that muscles contract quasi-isometrically during the propulsive phase of many stretch-shorten – type movements”.
The same ‘air time’ seen in animals can also be seen in elite runners.
Why the balls of your feet?
You would never contemplate doing plyometric work or skipping, bounding, and landing on your heels, right? This type of strength work is key to increasing tendon stiffness, which is also a key part of the SSC and thus performance running. So, this brings us to foot placement.
Taking the thinking on the SSC to a vision, it is beautiful to watch elite runners, especially in a group (watch the track or triathlon videos), they are like poetry in motion but more importantly, you will not see any bouncing up and down (vertical oscillation) as the quasi-isometric muscle contraction is at play.
The same air-time is seen in humans and animals when running.
We can see the old way of thinking about muscle contraction in running when we look at recreational runners. If they have a lower strike rate (cadence) and hence they are over striding. Therefore, the foot is on the ground for longer, thus rolling through from the heel and loading through the mid-foot before toeing off, thus producing more of a bounce up and down or side to side.
Heel striking:
We know the debate on foot strike has raged on now for many a year and I am not saying there is only one way, however, I am saying there is one way to optimally utilise the SSC.
I have read many a paper po-pooing ‘fore-foot’ landing and arguing for mid-foot landing or heel striking or this or that. So much conflicting chatter out there. For example, studies from the IAAF that set up cameras during the 2017 World Championships showed many of the marathon runners were landing towards the rear of the foot (see below). Maybe a little more use of the SSC will see the sub 2hr marathon and not the reliance on carbon shoes or pogo sticks?!
https://www.worldathletics.org/news/press-release/2017-world-championships-athletics-biomechani
Nevertheless, I can also show you from the very same 2017 competition that the 10,000m or 5,000m runners are landing on the balls of their feet (forefoot). The same applies to a large percentage of triathletes at a world-class level, with varying degrees from male to female.
https://www.youtube.com/watch?v=C93qwVmBseE
https://www.youtube.com/watch?v=L9DkIaW6ZiQ
I don’t have the answer to the question of why they are landing towards the rear of the foot in marathons, I wish I did. Maybe partly it can be explained by the marathon runners’ still very high strike rate and landing predominantly under their center of mass.
The old days:
Historically, we never really saw heel strikers in running, possibly because the only runners were ‘serious’ runners on cinder tracks and later tartan tracks with just spikes or even using racing flats in road running that have little or no support. Maybe the birth of the recreational runner and the development of the over-engineered running shoe (and over-marketing / overpricing) has facilitated the relatively recent heel-striking phenomenon. I’m not speaking about Vapour flies here, more the air-zoom et al.
It would be interesting to go back and look at the same marathon runners and look at them when they used to run over 5k and 10k on the track. What sort of foot strike did they have then?
So, the take-home messages are whether elite or age grouper;
The biggest bang for your buck; if you have a low strike rate, to increase the strike rate (cadence), find out how to do this here.
Ensure your foot is landing under your center of mass (under your hips)
Improve your lower limb SSC strength, through plyometric work through skipping, hill training, or traditional bodyweight plyometric work.
Word of caution:
If looking to transition into utilising the SSC by landing more on the balls of your feet as you run, then ensure that progression is done sensibly and gradually or look to get a recognised coach to help.
We will be looking at the strength element of running in our next blog.
JB