dr.ricky online

Tag: volleyball

  • Visualizing NCAA GPA data

    On 5 Sept 2018, the NCAA Research team tweeted out this chart  :

    It reports the average core high school grade point averages (GPA) among NCAA Division I freshman student athletes. So, a bit of a background – the National Collegiate Athletics Association governs just about all collegiate athletic programs in America, and the Division I schools devote the most money and resources to their athletic programs. A great deal of attention is thus focused on the Division I programs, almost to the detriment of the others (it goes all the way to Division III). The GPA is usually used as a measure of academic performance, though it may not reflect the difficulty of the coursework. But this chart is an egregious use of “infographics” to mislead rather than to bring insight to data:

    • Without a Y-axis to denote scale, the use of bar charts here visually make it appear that 3.77 is 7x higher than 3.07, when it’s actually far smaller in scale on standard 4.0 GPA scales (it tops out at 4).
    • The categorical use of the different sports makes it appear that it is the independent variable, and that GPA is what is being measured. But since the GPA was measured in high school, it actually precedes the sport.
    • Because of this switch in dependent and independent variables, a reader may interpret some form of causality – implying for example that choosing fencing will lead to better academic performance.

    Good data visualization should serve to bring new insight to the data that isn’t evident from just looking at the numbers. The GPAs considered here range between 3-4, which is letter grade B-A, quite above average academically, and that is unsurprising. These are the high school GPAs of student athletes recruited to Division I schools, arguably the most competitive programs. This is a measure of their past academic performance, but doesn’t say anything about how the sport chosen affects their current or future performance. The data, however, informs something about the sports programs themselves. Using the exact same data, I replotted the chart.

    High school GPA of males and females as recruited into NCAA Div 1 sports programs.

    The chart is in two parts – on the left is the section where a sport is available for both males and females, and on the right is a smaller section for sports that are gender specific. The axes go from 3.0 to 4.0, indicating the spread within this range. Sports are labeled accordingly.

    A linear relationship exists between enrolled female and male student athlete high school GPAs  – regardless of sport program. What this means is that at least within each sport, they apply their GPA criteria roughly with the same proportion to both genders. Which probably means that the sports programs recruit from the same communities for both men and women, that is fencing programs put a heavier emphasis on high GPAs for admission than basketball programs do, regardless of gender. But we see a stark difference in the GPA cutoffs between genders: almost all athletic programs recruit females with a GPA above 3.5, while more than half athletic programs enrolled male student athletes with GPAs below 3.5. In fact, all the male specific sport programs – baseball, wrestling and football – recruit with GPAs below 3.5. One cannot make definitive interpretations without further details on how the data is collected, but this implies that the barrier to entry to a collegiate athletic program, at least based on GPA, is significantly lower for males than for females. While some may think that this indicates superior academic performance among female student athletes, it could be an indicator for a systemic bias when recruiting for women across all sports programs.

  • Homographic terms

    Homographic terms

    Many terms in athletic coaching are poorly defined yet form the basis of disagreements. For example, the word athletic is really not quantifiable, and describes some quality that cannot be calibrated, yet is used as a basis of comparing people. In volleyball, the idea of ball control is heavily valued, is generally thought be observable, but different people will have different specific ideas as to what constitutes having ball control, or how to measure it.

    Homographic (despite the potentially juvenile interpretation) refer to situations where the same word can carry multiple meanings, and thus be confused between concepts, often leading to disagreements because each party was actually thinking of a different meaning for that word. For example, the word fly can be used both as a noun and a verb, each one carrying radically different meanings.

    But a more subtle disagreement comes with blocking. Blocking refers to both a technique and a strategy. For stat collection purposes, in beach volleyball, a block is only recorded when a player earns a point by jumping up and  intercepting a ball at the net. Consequently, this technique is confused with the whole strategy of blocking, which is a component of defense that limits the offensive options of the opposing team. Blocking actions that serve to guide the ball out or into the convertible control of the team are just as valuable as a stuff block. The technique of blocking is thus simply one of the options of the strategy of blocking. Good blockers consider all the available tools for the strategy. A jumping blocker that knocks the ball out of the defensive arena simply introduces unnecessary unpredictability. An effective blocker may never jump at all, and still control the attack options of the other team, and the contribute to the point conversion opportunities.

    Google Image result for volleyball setting

    Another term with homographic confusion between a technique and a strategy is setting – the popular image of volleyball setting (at least as unscientifically assayed through Google Images) is the distinct technique hand setting. Operationally, though, setting is a strategy of establishing the offensive opportunities for the team, and, as with blocking, the technique of hand setting is merely one of the many factors that figure into the strategy of good setting. One who can execute the technique of a hand setting well is not necessarily a good strategic setter. Conversely, good strategic setting should have a broad range of control techniques to carry options for efficient point scoring. Unfortunately, much of the dialog conflates the two meanings of setting, leading to this notion that one can judge the strategic value of a setter simply by evaluating the execution of the technique.

  • Volleyball and Newton

    Volleyball and Newton

    I ignited a fierce debate a few months back by simply asking:

    “the higher you jump, the more force you land with, right? (Yes, it’s a trick question)”

    I posed the question shortly after the McKibbin Brothers released their video on dealing with knee pain, and a trainer was explaining that you could land with up to 5x body weight in force (about 45 seconds into the video) – which then rolls into this rabbit hole about the equivalent of elephants on your knees. Now how could this be?

    So, a lot of this comes from the incorrect use of the term “force”. Basic physics, which most people should know, force acting on an object is defined by it’s mass multiplied by its acceleration, or

    Force =mass x acceleration 

    In most cases, we are talking about the force of gravity, which imparts the same acceleration to objects regardless of their mass (which is why in a vacuum, a feather and a bowling ball will fall at the same rate). This is an appropriate situation, because for a jumping athlete, that impact with the ground is really the same question about falling from different heights. So, what is acceleration? Acceleration is a change in velocity over time. The higher up you are, the more time gravity has to affect you, and so by the time you get to the ground, your velocity is higher. But what happens on impact? The velocity changes, from whatever it is imparted by gravity, to zero. This, too is a type of acceleration, and it’s this acceleration where the force comes from. So, let’s look at this equation again:

    F=ma = m (starting velocity-ending velocity)/time

    if we rearrange it:

    F x time = mass x change in velocity 

    The missing element in this discussion is how much time is being taken to bring the falling athlete to rest. Since mass and the change in velocity aren’t changing, we need to look at the relationship between time and the amount of force applied. The assumption in all the landing measurements is that the athlete stops on contact with the ground – hence, time is set to be very small. Thus, the amount of force goes up to effect the same change in velocity (the term, I believe, is impulse). But if we are able to extend the amount of time landing, the force acting can go down.

    It’s like dropping your phone from various heights. But how can a protective case allow it to drop without as much damage? That’s because parts of the phone can continue to fall as the case deforms, increasing time, decreasing force, and protecting the phone itself. Likewise, the flaw in the force plate measurements is not considering that a body is an elastic object and can redistribute the energy of impact. It only measures the force based on a very short period of time, and that will bring the force measurement up.

    In sand, since falling time continues longer than on an inelastic force plate, the force will decrease. But there are still more things to do to dissipate that energy of impact. Now will those exercises actually help? That’s a discussion for another day.

  • A nuclear option

    A nuclear option

    On the Facebook group Volleyball Coaches and Trainers (VCT), a coach shared a rule with regards to juniors beach volleyball tournaments held in the Chicago area – an optional one, in which any team, at any time, can request that no hand setting be used for the remainder of that particular match. It’s a bit peculiar, since it does open the possibility of changing the parameters of a match when it is already in progress. Then again, I don’t see it as being too different from the current AVP tournament format that changes the scoring system and let serve penalty at match point. But the stream of comments (I think over 100 at the time of writing) demonstrate a substantial objection to it, using words like “ludicrous” and “stupid” – mostly to defend the practice of hand setting.

    The VCT group is not open to public perusal, but many commenters decried the rule as depriving their teams of a tactical, if not critical, advantage. There are even those coaches who would forbid their teams from playing in tournaments that did not allow hand setting. Which is puzzling to me – volleyball variations happen all over the world, and as far as adaptations are concerned, this one is pretty mild. I’d say the 9-man game with race-based selection baked into the rules is far more controversial. As an act, hand setting on the beach may look esthetically pleasing, but is functionally disposable – historically, the team with the highest win record, Misty May and Kerri Walsh, employed hand setting sparingly, often not at all. Notice that the rule in question is a nuclear option: it bars the requesting team from hand setting as well. When invoked, it applies equally to both teams in a sport that is supposed to value versatility and grit. So why see this as some kind of attack on learning a skill instead of an opportunity to diversify the game?

    Hand setting is the golden calf of beach volleyball – some coaches insist on seeing it executed, without objectively quantifying its effects on team performance. But challenging the assertion of it’s inherent superiority is the topic of another post, the key point here is that the game is completely playable without hand setting, and in refusing the participate due to a small restriction, what are we really teaching our kids? Are we not participating because we cannot get things our way? Should we not focus on the opportunity offered to learn how a different related culture works? How we answer these speaks to what we prioritize as coaches, and that could be the difference.

  • Recognizing Sports Pseudoscience

    Recognizing Sports Pseudoscience

    In a recent discussion with BJ Leroy of USA Volleyball, I encountered a paper by Bailey et al (2018) published in the open access journal Frontiers in Psychology, titled  “The Prevalence of Pseudoscientific Ideas and Neuromyths Among Sports Coaches“. Since the journal is open access, the paper is readily available to download and read. The paper is basically a study on the pervasiveness of pseudoscience among sports coaches, even with ideas that have been long established to be untrue. Dr. Ed Couglin wrote a layperson friendly (albeit Irish-centric) interpretation of the paper.

    Suffice it to say, pseudoscience is rampant in sports culture, and pervasive in beach volleyball. I’d say much of the sponsor economy is built around pseudoscientific beliefs, but I’ll address those specific examples in future articles. What I’d like to share here is an excerpt from the Bailey paper, that outlines some properties of pseudoscience which will help you identify it. Bear in mind, this also applies to how people may argue their points online.

    • Unfalsifiability
    • Absence of self-correction
    • Overuse of ad hoc immunizing tactics designed to protect theories from refutation
    • Absence of connectivity with other domains of knowledge
    • Use of unnecessarily unclear language
    • Over-reliance on anecdotes and testimonials at the expense of systematic evidence
    • Evasion of genuine peer review
    • Emphasis on confirmation rather than refutation.
  • Court behavior beyond the game

    Court behavior beyond the game

    When people picture beach volleyball culture, they usually just think about just the game. People don’t seem to have to think about how the ball, or the net, or the court itself got there. Like the illusion of cooking shows on TV, these things didn’t actually magically appear – specially in public parks and areas, someone had to lug all the equipment there. Someone had to lay down lines, set up the net, bring out the balls. And someone has to break it all down and clear it away at the end of the day.

    In many venues, that someone is one person, or a very small group of people. The same dedicated people who will usually come week after week, spend the money out of their pockets to sustain the active social gathering. Oddly, though, this labor quickly becomes invisible. Players come to a venue simply assuming that they are entitled to challenge onto the courts, and fight to hang on to the courts. The commonly used “challenge” system can mean that those who have worked hardest to maintain a venue can end up using it the least.

    The unspoken injustice shows up in the gambit where players try to find that optimal timing to arrive late enough to avoid helping with set up, and leave early enough to avoid breakdown, while conspiring to form stacked teams to play as much as possible. Or in some cases, openly await the availability of the court set up to “steal” it from the ones who have worked on it. Anecdotally, I’ve observed self-professed “advanced” players disdainful to assist in these matters, more concerned about spending time warming up or stretching out — with the unspoken implication that the this is the appropriate burden for novices.

    Many communities have these selfless organizers and abused leaders, who do this for the love of the game. Afford them a bit more respect, and help to sustain the community. Offer to play with them, specially if you are borrowing their equipment. And at the very least speak your gratitude. Curb the entitlement, for those who rise in recognition often do so on the shoulders of the dedicated silent lovers of the game.

    Dedicated to the memory of Sammy delaSchott.

  • Another One Bites the Sand

    Another One Bites the Sand

     

    New season, new team for Tuesday night at Third Coast. Here is the shirt design, comments are welcome. You can order the Tanktop version There are also regular T-shirt versions.

  • The mythical 300 jumps

    The mythical 300 jumps

    This article has moved to a new location.

    Wilson, the sporting goods company, posted an ad on Instagram declaring

    DURING A MATCH, VOLLEYBALL PLAYERS ON AVERAGE JUMP 300 TIMES.

    The ad is accompanied by an illustration that depicts female beach volleyball players, which implies that this number applies to beach volleyball specifically. This number appears unusually high, so I inquired as to the source of the number.

    https://instagram.com/p/BedVH6rAMp0/

    Michelle Magsamen checked with the marketing department of Wilson, and provided three links that are the alleged source of this figure:

    1. From Redbull.com – 8 stats that show why beach volleyball is the best

    A beach ’baller jumps on average 300 times per game.

    In this article, the author Jonno Turner reports an average of 300 jumps per game – not per match as reported by the advertisement.

    1. From Schoolgamesfinals.org – this is an article written to encourage people to watch indoor volleyball at the school games of Loughborough University. The stat is reported at 300 times per match, but with indoor volleyball, there are up to five games per match, unlike the three set maximum for beach volleyball.
    2. A contributing article in Volleywood.net – written as “10 fun facts about volleyball”, it is a direct reprint from an article Ten fun facts about Volleyball from the website 10-facts-about.com. Fact 4 is listed as:

    Most volleyball players jump about 300 times a match.

    In all likelihood, this last link is the main source of this number, and was continually misinterpreted by the other writers to fit their current narratives. I tracked 10-facts-about.com to a company in Sweden called NanOak Technologies, appears to be a “content farm” – they produce these sites and brands like 10-facts-about and Wisefacts – ostensibly pouring out random interesting “facts” to attract page views, and therefore sell advertising. There is no verifiable vetting of this information, but they are cherrypicked to most likely to appeal to confirmation bias.

    In effect, this is fake news – unvetted information that is twisted just to profit from the misinformation. Though Wilson may have citations, those sources are ultimately unreliable at best.

    So what is the real number?

    Is there real data on the number of times beach volleyball athletes jump on average in a match? Much more peer reviewed data studies the indoor game, but there are some data on beach volleyball.

    1. Loren Anderson of Rise Volleyball Academy did some research on this during a discussion on the Facebook group Beach Volleyball Coaches. He tracked the all the jumps during the gold medal match at the FIVB 4-star beach tournament in the Hague between USA and Brazil. He counted 201 total jumps for all players, averaging 50 jumps per player over the match (~25 jumps per set).
    2. Loren also found a 2009 report from Slovenia (Turpin et al, 2009) that tracked the number and types of jumps during four matches of elite beach volleyball players during a tournament in 2006. They report a total average of 167.5 jumps per match (with a very large variance of 38.5), which comes down to about 40 jumps per player per match, or 20 per set.
    3. Perhaps most useful is that the FIVB report The Picture of the Game, last produced to statistically analyze 12 men’s and 12 women’s matches, and provides some pretty detailed stats and heat maps of defense. On page 37, it reports an average of 405.8 jumps per match (162.3 per set) for women, and 396.8 jumps per match (158.7 per set) for men. Dividing between the four athletes on the court, that comes down to ~40 jumps per set – which is consistent with the Turpin et al report.

    Granted, these are for elite volleyball players playing in high stakes tournaments, but it’s still nowhere near the 300 jumps per match average per player. In fact, only if you account for the jumping of all players on both teams in beach volleyball can you come close to this average number.

    Based on this research, the average number of jumps per player per match in beach volleyball seems to be between 40–80.

    Follow on Twitter and Instagram as @volleysensei

  • Sharing Volleyball Courts

    Sharing Volleyball Courts

    The abundance of public beach volleyball courts in Southern California is a pleasant anomaly. Locals usually do not have to compete for the availability of a court, but in most other places, beach volleyball courts are relatively rare, and communities have to share them. Very often, a park may only have one court, and cliques and alliances are often formed to defend priority in access.

    In civil interactions, though, the challenge court system is the most common traditional way for beach volleyball teams to share in the use of a court. When a pair of teams are playing against each other, waiting teams form a queue to challenge the winning team on the court. A winning team stays on the court, and a particular strong team can continuously play in theory. It’s also a source of great rancor when the list of teams waiting expands beyond around four waiting teams; the delays can be intolerably long for even the first attempt at using the court. For example, if six teams were sharing a court, the last team in line will have to wait for five entire games to be completed. Assuming an average 20 minutes per game, that is almost two hours.

    In practice, however, is that the wait is usually much longer. In traditional challenge court systems, the court itself is unused for significant periods of time, sometimes because the challenging team hasn’t warmed up in preparation – but most often because of delays caused by the winning team. After a set, the winning team requires a period of time to hydrate, catch their breath, use the restroom…in the meantime, the court is unavailable to any of the sitting teams. These delays add up, specially if the winning team has continuously won several games in a row.

    A solution

    I propose a skip-challenge system. Let’s assume there are six teams, A-F sharing the court. In the first set, team A plays team B. Assuming team A wins, both teams immediately step off the court at the point of victory, to allow an already warmed up team C and team D to begin playing. Teams A and B can share pleasantries at this time, and hydrate as needed, and prepare for the match between teams A and E (B goes to the end of the line). Assuming team C wins, both teams get off the court right away for teams A and E, and the next game is between teams C and F. The challenge then iterates from that point on.

    1. In the above example, team F gets on the court a full game earlier than in the standard challenge court system. Plus time saved from not having to wait for the recovery of the winning team makes it even faster.
    2. Every team sits at least one game after playing. Winning teams earn the right to limit this to one game, losing teams go to the end of the line.
    3. There’s no delay in getting teams to using the court, this maximizes the use of the facility and daylight.
    4. The desire to get on the court quickly incentivizes adoption of shorter, lower point games, since it shortens sitting times for everyone, although this is entirely optional.

    For large groups of teams, the skip challenge system may be a more equitable way of distributing a scarce resource, and keep volleyball communities healthy.