+ / -

In youth sports, the subjective qualities of an athlete (attitude, effort, teamwork, sportsmanship) are more important than the objective ones (points, wins/losses, etc).  The subjective qualities are difficult to measure by definition.  This post is about an objective way to measure your players.  Rather than focus on outright wins and losses, I like to use a different measure.

I am a big fan of using the +/- (plus/minus) statistic in basketball.  It is more commonly associated with hockey, but I think it applies well to basketball.  By combining both offensive scoring and defensive efficiency, it is an objective measure of the athlete's performance.

I use this statistic as my main evaluation tool for my team's performance in games.  I evaluate the +/- of each individual athlete and each combination of athletes (pairs, trios, quads and full sets).  I adjust the statistic for the amount of time the athlete or combination have played.  Also, I evaluate these results as compared to the expected result.  For example, if Player A played 16 minutes of a 32 minute game and finished +3, that's good.  If we won the game by 20 points, I would expect them to be +10 (50% playing time * 20point win), which would indicate they underperformed in comparison to the team.  This comparison technique creates a ranking of the players on the team.  Over the course of many games in a season, this statistic is a very strong measure of each player.  Over a small sample of games or individual games, the statistic is highly influenced by the combinations of teammates on the court and the combination of opponents.  Making decisions based on a small sample is not advised.

This statistic is possible because I diligently track playing time and the team scoring during each shift.  The person that does the scoring is less important to me, though it is tracked by the standard scorebook.  I will acknowledge the top scorers during the season, but the biggest praise each week and for the year, is for the players that have the best +/-.  Those players had the biggest positive impact on the outcomes in the game.

Which stats do you focus on?

Youth Distance Running Limits

We've all heard stories of wonderkids that run amazing distances or times at a very young age, but we also have seen our share of injury and burnout stories from pushing kids too far, too fast, too young.  An overuse injury on a growing body, especially prior to finishing puberty, can create a lifelong problem.

I have spent many years as a runner, as a coach and as a dad of a youth runner.  I have no specific training nor am I in the medical field.  That being said, I think I've used my experience and my mathematical abilities to come up with a workable formula for reasonable limits on the distance that youth runners should complete.

First, the formulas (explanations will follow):

Maximum Daily/Event Distance (km):
        (Age in years ^ 2) / 10
Maximum Weekly Distance (km):
        Max Day amount * Age in years ^ 0.5 (sq root of age) * Season Factor
 Season Factor:
        Off-season: 50%    Normal Peak: 75%   Post-Puberty/Elite: 100%

The Maximum Daily Event Distance came from observations of many youth runners from a Summer track program I coached during high school and college, as well as the participation success from races that I helped organize with my running club.  I came up with general rules of 7 years old for a 5k and 10 years old for a 10k, in high school before running a half-marathon and around 21 for a marathon.  I noticed that this essentially fit a mathematical equation and used the extrapolated results at other ages. 

From that straightforward calculation, I began to review guidelines for weekly mileage limits.  From experience, I wanted to limit the number of days of running for younger ages and eventually settled on the square root of the age as the multiplier.  That is not to suggest that a 16 year old can only run 4 days a week, though that would be the case if they are running longer distances each day (equal to their max daily distance * season factor).  In practice, their daily distance will be lower, allowing them to run 5-6 days comfortably.

The results allow for the dedicated and enthusiastic young runner to compete at a challenging level, but protects them from over-zealous coaches and parents and the resulting over-use injuries.

The charts below show the results at each age and then flips the calculation to show the age needed for a particular distance.

AGE	Single Run (km)	Single Run (miles)
4	1.6	0.99
5	2.5	1.55
6	3.6	2.24
7	4.9	3.05
8	6.4	3.98
9	8.1	5.03
10	10	6.22
11	12.1	7.52
12	14.4	8.95
13	16.9	10.50
14	19.6	12.18
15	22.5	13.98
16	25.6	15.91
17	28.9	17.96
18	32.4	20.14
19	36.1	22.44
20	40	24.86
21	44.1	27.41

	Normal/Peak		Post-Puberty/Elite
AGE	Weekly (km)	Weekly (miles)	Weekly (km)	Weekly (miles)
4	2.40	1.49	3.20	1.99
5	4.19	2.61	5.59	3.47
6	6.61	4.11	8.82	5.48
7	9.72	6.04	12.96	8.06
8	13.58	8.44	18.10	11.25
9	18.23	11.33	24.30	15.10
10	23.72	14.74	31.62	19.65
11	30.10	18.71	40.13	24.94
12	37.41	23.25	49.88	31.00
13	45.70	28.40	60.93	37.87
14	55.00	34.18	73.34	45.58
15	65.36	40.62	87.14	54.16
16	76.80	47.73	102.40	63.64
17	89.37	55.54	119.16	74.06
18	103.10	64.07	137.46	85.43
19	118.02	73.35	157.36	97.80
20	134.16	83.38	178.89	111.18
21	151.57	94.20	202.09	125.60

Off season/Pre-season weekly totals would be half the Elite amount

Age Age Distance (years) (yr mo) 1 mile      4.01 4yr 2 miles      5.67 5yr 8mo 5k      7.07 7yr 1mo 8k      8.94 8yr 11mo 10k    10.00 10yr 10 miles    12.68 12yr 8mo Half-marathon    14.52 14yr 6mo 20 miles    17.94 17yr 11mo Marathon    20.54 20yr 6mo What do you think?