Last week I wrote a recap of the course I recently attended on the prevention and treatment of running injuries. In that post I mentioned that the topic of impact loading rate has gained a lot of Nike Air VaporMax Femme interest lately in terms of it’s potential relationship to injury risk in runners. In the comments that followed that post, Amby Burfoot suggested that I write a summary of what exactly vertical loading rate is, and why it is important to a runner. This post is my attempt to give a shot at an explanation, but also to point you to a series of posts by an expert on the topic – physcial therapist Jay Dicharry from the University of Virginia SPEED Lab.Vertical Loading Rate – What is It and Why is it Important?
As we run, each Adidas Superstar Femme foot comes into contact with the ground some 80-100 times per minute on average. This translates to a stride rate/cadence of 160-200 steps/minute, and I choose to keep the range broad here since cadence varies from person to person and to some degree with running speed. Every time you land, your foot impacts the ground with a certain amount of force, which is counteracted by an equal and opposite amount of force applied by the ground on your foot. This equal and opposite force is known as the ground reaction force or GRF for short. Nike Air Max 270 Womens The ground reaction force comes in a number of components, typically broken into anterior-posterior (along the direction you are traveling), horizontal (side-to-side), and vertical (straight up and down). Of these, the vertical GRF is the greatest in magnitude, and is the one I will focus on here.
Below Nike Air Max 2017 Femme is a graph depicting the vertical ground reaction force curve for a heel-toe runner (modeled after Cavanagh and LaFortune, 1980)On the vertical (Y) axis is the value of the vertical ground reaction force as a function of body weight. You can think of this as a proxy for how much force the foot is applying to the ground as you run. The horizontal (X) axis shows time in milliseconds – the amount of time each foot is in contact with the ground varies among people and at different running speeds, but 300 milliseconds (about 1/3 of Nike Air Max 270 Mens a second) is a reasonable number for a typical runner. The curve depicted on the graph shows how vertical GRF changes from the point of initial contact of the foot with the ground (time 0) to the point where the foot leaves the ground on toe-off (about 300 ms). What you’ll notice in this graph is that www.tonyrusconi.it there are two distinct force peaks. First, the impact peak is the initial force applied to the ground by the foot and lower leg at initial heel contact (remember, this graph is for a heel-toe runner). Full body weight is not being applied at this point, so the impact peak is basically a function of the weight of the foot and lower leg hitting the ground. The active peak represents the force applied by the foot and supported body weight during roughly mid-stance. Notice that it is larger than the impact peak – this is the typical Nike Air Max 95 Mens pattern.In the above graph, vertical loading rate is essentially the slope of the line from initial contact to to the impact peak (in practice, it is usually measured in the region from 20-80% between these points). The loading rate simply represents how quickly the impact force is applied – a steeper slope Adidas Superstar Mujer means a more rapid collision. A more gentle slope would indicate that force application during impact is being spread out over a longer period of time. A reasonable analogy would be punching the wall with your bare fist – your fist comes to a very rapid stop and the force is applied quickly. This is not a good thing for your fist. On the other hand, if we put on a boxing glove, we could still hit the wall really hard, but the cushion in the glove would slow down the impact and distribute the force over a longer period of Nike Air Max 95 Mens time. Consequently, it would not hurt as much, and would likely not damage the bones in your hand. The same logic applies to crumple zones in a car – when you crash the crumple zone slows down force application to protect the driver and passengers from the sudden shock of an immediate impact.The upshot of the Nike Air Presto Mujer above information is that if you are going to run in a heel-toe style, putting cushion under the heel will slow down impact and decrease the loading rate by spreading force impact over a longer period of time. This is a good thing for your heel bone (the calcaneus), and why barefoot runners tend to move away from a heel strike, particularly on hard surfaces. Your heel fat pad does not provide enough protection to absorb impact during barefoot heel-toe running. If you are a heel-toe runner, particularly one who overstrides www.domoreso.fr with an extended knee and a pronounced heel strike, you should by all means wear a shoe that has a cushioned heel.
