Apparently during World Championships action today two players suffered ankle injuries in a single set. With the foot injury suffered by the Bulgarian Yosifov earlier in the tournament (see video below), the ‘spate’ of injuries prompted a reader on the facebook page to comment that the FIVB needs to change the centre line rules. I didn’t see either of the current actions so I don’t know if they were the result of legal or illegal actions so I’ll assume for the moment that they were both legal actions.
The first thing I will say is that Ruben Acosta tried to address this issue about ten years ago but despite his not inconsiderable power, he couldn’t even persuade people to have a discussion about it. So the groundswell of support to change the rule is essentially zero.
Another thing that is essentially zero is the chance of incurring an ankle injury. So the second thing I will say is that there is no reason to change the rule. This week three players suffered very visible injuries. Therefore we have the danger of net actions at the forefront of our mind. But how dangerous are these actions in reality? We know that in a men’s volleyball match each team has about 100 spikes per match. Each of these theoretically creates an injury risk by having spikers and blockers jumping very close to each other. So in a match we have 200 spikes. In this tournament there are 103 matches. In total there will be about 20,000 ‘injury risk moments’ of which three have led to injury. That means there is an injury roughly every 6,500 actions. The probability of injury is a number very, very close to zero. If you look at it another way, the teams will play 206 matches this tournament. That total of three injuries means a team could expect to have a foot injury about once every 70 matches, or an individual could have one about once every 420 matches. In my team I have had one ankle injury during a match in the last five seasons, about 170 matches.
I think when an ankle injury occurs we should not think about how many of them there are, because there are actually hardly any. We should be thinking of how few there are and how insanely improbable it is to happen at all.
The phenomenon of incorrectly judging probability is very common. The most visible example being that of shark attacks.
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