Imagine Sarah and Melissa up against Alix and April at the Tokyo Olympics this Summer.1 The score is 20-19 in the second set of the Gold Medal match. I doubt that anyone will say but what if Sarah was using the same sunscreen Alix uses? or what if they were only wearing another brand of bikini.. On the other hand F1 auto racing and 12 meter yacht racing represent a combination of athlete and machine and in the case of F1 the team strategist may be the most important element. You have to ask what is important in sport? What makes for fair competition and how do you compare results among events? Convention and rules decide what is important and fair. Sports make distinctions between male and female athletes. Age classes are common throughout sport and a number have weight classes. Technology has become part of many sports, but generally it's heavily regulated.
except in running
Recently the World Athletics, the body that governs many running events, ruled on a Nike shoe with a new rule that basically allows it. I'm not a runner, but there's a lot of interesting physics and biomechanics going on. In endurance sports the elites are judged by their athleticism - what are their VO2 max, COT and a few other measures? VO2 max is roughly the maximum rate of oxygen consumption - think of it as directly related to the maximum amount of power you can generate. The cost of transit or COT is calculated for about anything that moves. You can think about it as your fuel economy.
The graph shows what the cost of transit looks like for a person. Everyone will be different, but the curve shapes are similar for people in reasonable physical condition. Walking has a very narrow region of high efficiency or low COT. People are very good at finding their optimal walking speed and not straying from it You can become more inefficient and burn more Calories by increasing your walking speed - it doesn't have to be by much - and get an additional benefit of a more intense exercise.
Running is different. Here COT is almost flat over a large speed range until you've reached your maximum comfortable speed. Reducing your COT will improve your times. Doping generally buys you a two to five percent lower COT. Of course that's dangerous and banned, but some do it anyway.
What if a piece of apparatus lowered your COT? What woud that mean for the sport? Would someone regulate it?
Variations of the Nike Vaporfly shoe have been around in development form for over four years. Early on it wasn't clear how much of a difference it made. Then about two years ago it started to become clear there was a serious advantage using it. The almost current shoe used in the two hour marathon assault effectively lowers COT by about four percent. It does so by reducing the amount of energy lost to the ground. The human foot acts a bit as a spring, storing energy as it hits the ground and releasing some as it rebounds. It's not terribly efficient, which is one of the reasons you're faster on a bike than on foot. A shoe can increase this efficiency, but until recently the increases have been under one percent - less than the natural daily variation an athlete sees.
It turns out World Athletics, the body that regulates running, basically hasn't regulated running shoes in over a decade until now. Nike uses a curved carbon fibre insert that adds a small amount of efficiency, but more importantly it has a very thick layer of a lightweight foam that acts as a spring. The amount of energy it can store is proportional to the thickness - in this case about four centimeters.2 The carbon fibre insert gives stability to what would otherwise be a very unstable foam pillar. Most conventional running shoes have less than a two centimeter platform which doesn't allow enough room for a curved carbon fibre insert .. that and the foam depth would be much lower reducing the spring effect in the process.
Tests so far indicate a four to six percent COT gain - this translates into two to four percent better times for a given athlete. The shoes gives an increase similar to doping. You might give everyone the same shoes, but there are a couple of issues. Nike patents heavily and not everyone runs for them .. we have an uneven playing field until other shoe manufacturers can find their way around. it's quite possible that medals might be determined by lawsuits. Worse are indications that not everyone has the same COT response to the shoe. The range appears to be zero to six percent with back strikers and very short contact times doing better. It also works bette for shorter runners as it increases their effective leg length faster than taller runners. That's probably about an additional one percent effect. A number of potentially great athletes may have been eliminated from the podiums of the world. Will be be looking at COT, VO2 max and Vaporfly responce as fundamental characteristics of a runner?
There are any number of access issues. Many of the Div-I colleges have shoe sponsorships. What if you're sponsor is the "wrong" company. And for non-sponsored programs and amateurs can afford a more expensive shoe. And the people impacted most - sponsored athletes - can't speak out one way or the other.
I don't follow athletics (track and field), but running seems like a rather pure sport. Of course shoes make some difference, but it seems like that component should be minimized rather than maximized so we can see what the athlete can do rather than some combination. A physicist might say something like just what is it the sport is trying to measure? I would like to think it's who is the best athlete.
So many questions.
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1 Two of the best women's beach volleyball teams in the world. Sarah and Mel are Canadian and current world champions. April and Alix are the best America has.
2 Hooke's Law.. the force needed to compress or stretch a spring varies linearly with distance. Twice the distance, twice the force.
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