Tuesday, May 15, 2012

It's All About The Standard Deviation

So my daughter is heading into her fifth year of club soccer and will be playing next year as a sophomore on her high school team. Using Deliberate Practice, she's improved her skills dramatically, but she still has one glaring weakness.

She's slow.

Well, she's not actually slow compared to other girls her age, she's just slow compared to other girl soccer players her age. It affects her self confidence when she plays to the point where she concentrates more on running than on her skills. Playing defense, she has the added stress that every time she's outpaced by a forward, there's a chance of a goal.

Which brings me to this summer's training. Her team practices are all about skills and your speed is whatever God gave you. She's going to need to work on speed on her own. She'll never be a world-class sprinter, but she can certainly get faster through strength and technique. As her dad, I will need to set expectations for her. What should those expectations be?

It's all about σ, the standard deviation.

Click on the image for a better view.

For the 40 yard dash, a good benchmark for a defender, she's probably right around the 50th percentile of all girls. Since we know it's unreasonable to expect her to run as fast as the fastest girls, it's pointless for me to look up record times in the 40 yard dash and use those as a marker for her performance. Instead, I looked up σ, the standard deviation for high school girl student athletes. It turns out that for the 40 yard dash, σ=0.37 or thereabouts. Just as a reference point, the mean is about 6.05 seconds.

The standard deviation of all girls her age gives me a guide for what I can give her as my expectations for her training. Since she will be doing much of her training on her own, these expectations will spur her on to perform*. If her summer training improved her 40 yard dash time by just 0.4 seconds, she would jump from the 50th percentile to above the 85th. It's probably unreasonable to expect anything more than that.

* - If you think this is harsh, then I'm sorry. Real life has expectations, too and they aren't given to you by a loving father. Instead, failing the expectations of life can lead to job loss, divorce or worse.


tim eisele said...

It is important to work on her speed, but I think that ability to change direction quickly is at least as important. It seems to me that, by combining superior maneuverability and acceleration with some strategic planning, she can force the other players to run *further*, which would negate a lot of their speed advantage. And it would also make it harder for them to fake her into running one direction, then dash off the other direction before she can switch tracks.

So, I'm wondering whether it might not be at least as useful (if not more useful) for her to combine running fast with rapid direction changes. I'm thinking that, in addition to a straight 40 yard dash, it might be a good idea to have her run back and forth on, say, a 5 yard track, and time how long it takes for her to complete 40 yards. It will be slower, but (a) it will help her to lose less time changing directions, and (b) this is probably something the other players aren't practicing, which could give her an advantage in an area that they aren't expecting.

K T Cat said...

Bingo! She trained with a premier elite U18 team (two years and two levels above where she usually plays) and was blown away by how much they concentrated on speed and agility.

The literature is filled with data for 40-yard dash times, but agility measures were a bit sparse. Having gone to almost all of her games over the last 5 years, my take is that if she were faster, she'd relax and her true skills would come out. She agrees.