In the video, note the dramatic contrast in stride and footstrike between runners 1 and 3 (flexed knee at contact, midfoot or very mild heel landings) and runners 2 and 4 (overstriding with extended leg, highly dorsiflexed foot, and pronounced heel strike). Runner 1 is wearing Newton shoes (2mm drop Distance Racers I think). Runner 2 appears to be in Mizuno Wave Creations, which have a large "shock absorber" in the heel. Can't easily make out the shoes for runners 3 and 4, but they appear to be standard training shoes with a reasonably large heel lift.
A few points are worth mentioning here:
1. Overstriding is a very real occurrence in a race setting. Runners 2 and 4 both land on a highly dorsiflexed foot with a nearly straight leg that is extended well out in front of their center of mass (COM is located roughly near the hips). The thinking is that overstriding will result in the shoe and skeletal structures of the lower body absorbing much of the initial impact as shock travels through the heel and up the leg, and that this in turn might increase the likelihood of repetitive use injury in places like the tibia, knee joint, and hip joint. I would also suspect that the pronounced heel strike requires greater activity of the muscles on that anterior side of the lower leg (e.g., the tibialis anterior) to slow the foot slap that occurs after initial contact - this can be associated with things like the development of anterior shin splints.
2. In a midfoot landing with a flexed knee, and more or less vertical orientation of the lower leg at initial contact (runners 1 and 3), the soft tissues of the leg (muscles and springy tendons/ligaments) likely are doing more of the initial shock absorption, relieving some of the impact on the bones and joints of the leg (see below). It is possible, however, that increased muscle usage could also result in increased metabolic cost to the runner (see Derrick, 2004 for more on this).
3. As runner's 1 and 3 show, it is possible to adopt a midfoot or very light heel landing in shoes that vary in their construction. My personal belief has grown to the point where I now view form as more important than shoes, and this video shows that you can adopt a potentially less impactful stride even in a more heavily cushioned, heel-lifted shoe. That being said, such shoes, in my opinion, make it much harder to get to that stride, and this is something I have experienced myself. Form and shoes are separate yet linked, and it is my belief that moving to less shoe with a smaller heel lift can help one to migrate away from and overstriding gait.
4. So, ultimately the question that arises is if you are an overstrider, what can you do? A few weeks ago I wrote a post discussing a paper published by Dr. Brian Heiderscheit and colleagues in the journal Medicine & Science in Sport and Exercise. Dr Heiderscheit's paper showed that runners who adopt a quicker stride (increased step rate) reduced impact at both the knee and hip. The study showed that increasing stride rate by 10% increased the flexion angle of the knee at initial contact, shortened stride in terms of distance of the heel from the center of mass at contact, reduced vertical excursion of the center of mass (i.e., less bounce), reduced the inclination of the foot at impact (i.e., a less pronounced heel strike), and reduced braking impulses. Many of these changes were observed with even just a 5% increase in stride rate. There was a lot more to that study, and a limitation was that the results are not yet linked to reduced injury rates (a study is apparently underway), but the take home message was that adopting a shorter, quicker stride might be a good approach to overcoming an overstriding gait, potentially reducing injury risk in the long run (no pun intended!).
5. Finally, a personal note. I have been working very hard over the past several months on making these very changes (shorter, quicker) to my own stride. Why? Take a look at the video below of me from the same point in the Manchester race as the video posted above:
Video of my footstrike/gait just after mile 6 of the Manchester City Marathon. Video shot at 300 frames/sec with a Casio Exilim EX-F1 camera. Courtesy of http://www.runblogger.com/.
This video was taken almost a year ago, and the pronounced heel strike is fairly apparent - I wanted to change my gait if for no other reason than to see if I could. After a long period of initial awkwardness, I now feel very comfortable running with a shorter, quicker stride, and most of the time now I seem to run on my midfoot or forefoot (depending in large part on shoe choice and fatigue). Will this make me a better or less injury prone runner? It's hard to say, since I've never suffered an injury that has caused me to miss significant training time. The transition, however, has been amazingly interesting to experience, and I now feel like a switch-hitter in terms of running form. I can move between a heel and mid/forefoot strike easily, and I can tell almost instantly which is going to be more appropriate and comfortable in a given shoe. All of this is a continual learning process, and I suspect that my form will be a work in progress for many years to come - I look forward to it!
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