I heard about a volleyball research paper while listening to an episode of the Perception & Action podcast. That paper is How functional movement variability facilitates successful skill adaptation during the volleyball attack by, I believe, a group of Portuguese researchers.

While I think the podcast does a decent job of presenting the ultimate conclusions of the paper, I found it difficult to ascertain from it how the experiment was actually done. Fortunately, that’s pretty clearly outlined in the paper. As the title indicates, it’s about attacking. Specifically, attacking against a block under three conditions:

  • Double block taking cross
  • Double block taking line
  • Split double block allowing an attack at 6

Hitters took turns attacking as part of a serve-pass-set-attack sequence, with three receivers. The attackers were not included among the passers. They each did an equal number of attacks against all three of the above blocking set-ups. There’s a diagram in the paper showing the drill structure.

There were two training groups:

Traditional Approach (TA) group: Each blocking set-up was trained separately. The hitters first faced the block taking cross for 6 balls, then taking line for 6 balls, and finally the split block in the last 6 balls. Or some other variation of the sequence. In other words, the hitters knew what block set-up they were going to face before each rep.

Constraints Led Approach (CLA) group: Here the attackers still spread their attacks evenly across the three block set-ups. The difference here, though, is those set-ups were random. So the hitters didn’t know before each rep which kind of block they faced.

There’s a whole section on spacial temporal variables. You may find that interesting, though it’s pretty technical. For most of us, the key bit is the attack performance the results from the preliminary test (t1), immediately following 6 weeks of training (t2), then finally somewhat later to test retention (t3).

Here’s the graph showing the results for the two groups:

As expected, the two groups showed the same performance before the training. While the TA group showed little gain from the training, the CLA group improved markedly, and even extended the gain slightly in the retention test. The * in the graph indicates a statistically significant difference.

Makes sense when you think about it, right? Real attacking situations involve uncertainty about what the hitter will face. That requires decision-making. The CLA approach incorporates this, while the TA approach removes it.

Now, this study is based on a total of 12 male players who averaged about 17 years old at the start of the study. All the players play at a relatively high level in the Portuguese system. So not exactly a widely representative sample. This is a limitation you have to watch for in these kinds of research studies. Thus, we can’t jump to the firm conclusion the CLA approach used above is better than the TA approach based just on these findings.

That said, this paper is part of a growing literature supportive of variability in training over low variability, blocked methods. In other words, while doing something repetitively might be useful in some specific instances, broadly speaking it’s better to make things more variable.

Oh, and it’s looks like variability is better for injury prevention too. That’s a discussion in How we Learn Move, and in this other episode of the Perception & Action podcast.

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John Forman
John Forman

John is currently the Talent Strategy Manager (oversees the national teams) and Indoor Performance Director for Volleyball England, as well as Global Director for Volleyball for Nation Academy. His volleyball coaching experience includes all three NCAA divisions, plus Junior College, in the US; university and club teams in the UK; professional coaching in Sweden; and both coaching and club management at the Juniors level. He's also been a visiting coach at national team, professional club, and juniors programs in several countries. Learn more on his bio page.

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