Don’t just cite the research, actually read and understand it!

I came across a post on social media regarding an academic study of serve-reception. Here’s the full quote.

A study published in the Journal of Sports Sciences by Paulo et al. (Paulo A, Zaal FTJM, Seifert L, Fonseca S, Araújo D. Predicting volleyball serve-reception at group level, 2018) showed that, about serve-receive success “decreasing alignment of the receiver with the ball and the target increased the chances of using the underhand-lateral pass, and that the use of the underhand-lateral pass was associated with lower quality receptions”. So, if you play volleyball do not be lazy, move your feet fast (you will only move fast if you lower your hips and stay on your toes), place your body and platform BEHIND the ball, if you want to increase your chances to succeed in serve receive. Do not trust side passes. Science is saying that!

The last couple of sentences jumped out at me. They are clearly interpretations of the paper findings, ones seen to support the idea of center-line passing. I’m not a fan of focusing on that beyond introductory teaching, as you will see if you follow the link.

But that’s not the point of this post. Instead, I want to focus on the analysis side of things.

Being the curious sort, and having lots of experience reviewing this kind of research from my own PhD work, I read the paper in question. Not surprisingly, reading the paper produced two significant issues with regards to the social media post.

First, the results don’t make a strong case. Yes, the authors of the study did find that receiving the ball in the center line – what they refer to as “underhand-frontal pass” – did produced better passing results than passing outside the center line (underhand-lateral pass). They described the difference, however, as being weak from a statistical perspective.

Second – and this is the bigger problem – the causality is unclear. By that I mean we don’t know if the passers opted to pass outside their center line. They may have been forced to do so by the serve. Given that the sample is from international level men’s players and includes topspin jump serves, I’m inclined to believe it’s not really a question of choice.

I think we can agree that a ball hit hard outside your body line is harder to pass than one hit straight at you. You simply don’t have as much time to get a well-positioned platform in place. Forget about moving your feet! Naturally, we expect these more difficult serves to produce worse passes on average. Despite this, the authors of the paper don’t see a big difference, statistically, between lateral and center-line passing performance.

Could it be that in fact lateral passing would prove superior if considering equally difficult serves? Well, we know in terms of hard serves going outside the body that center-line passing is basically impossible. What about slower or closer serves where you could get the ball center line, though? Could it be that lateral passing would show better results? This paper provides no insights in that regard.

So the poster of the item above has attempted to use as support for their own views research which at best only offers weak evidence. Really, it provides no evidence at all because the analysis of technique does not control for serve characteristics (i.e. difficulty).

There’s more issues

There’s also a major issue with this paper in that the sample the authors use is extremely narrow. It includes only four passers. They all come from the Portuguese Men’s National Team. So we’re making judgements based on the performance of just a few male players of a certain caliber in one team receiving serves from servers they’d probably passed against many, many times before in training.

Can you see how this might be a problem in terms of being representative?

That automatically says you should draw no real conclusions from the findings. I’m not saying there isn’t some quite interesting stuff. There certain is, both in this paper and this one the same authors did focused on single receiver passing. What I am saying is the best you can do with this kind of research is to say something like, “That’s interesting. We should explore it more deeply.”

Don’t be that poster

Please, please, please take the time to actually read any research presented to you. Don’t accept what people say about the research at face value – especially if that person might have an agenda, like supporting their own position. That was what tipped me off in this particular case. Also, don’t cherry pick from your own perspective. Don’t just present research that you think supports your case and ignore or downplay the stuff that contradicts you. Confirmation bias is a real issue for us all.

There’s a phrase I heard a while back that I think is a good one to live by in this sort of context. It is “strong views, loosely held”. That means you are strong in your belief, but able to change your mind on things when presented with good evidence. It’s not about being right. It’s about getting it right.

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