I spent much of the weekend playing sports with my kids. You'd think that would be a normal weekend for a guy who writes about exercise for a living and has three active children, but it's never quite worked that way before now.

My son, who has Asperger's disorder, never cared a lot about sports, even when he played them. (Sometimes especially when he played them.)

My older daughter, Meredith, is the family's best athlete. She wants to play everything, but has only sporadically wanted me to help her with whatever she's playing at the moment.

And my younger daughter, Annelise, is far too sensible a child to take sports seriously. She likes her activities to be predictable, which is why she prefers ballet to baseball. (Meredith tried ballet once. She tried to turn it into a contact sport, which didn't work out so well.)

But things have changed lately. Harrison wants to play catch every day. And because Meredith wants to do everything better than her brother can do it, she wants to play at least as often as he does. That's on top of practicing soccer (she'll be on the travel team for the first time this fall), swimming, riding her bike, and whatever else she feels like doing.

So our yard is starting to look like a Play It Again Sports franchise after a tornado has hit - bats, balls, gloves, and bikes everywhere. As you can imagine, I'm in heaven.

I bring all this up because I just read this article, and I'm not sure how to react:

As a rule, I don't like to judge the choices other parents make, unless those choices involve doughnuts and Mountain Dew. But as a fitness professional, I wonder if all that expensive one-on-one training really does anything that general activity and physical maturation won't do naturally. Someone quoted in the story feels the same way:

I've talked to lots of trainers over the years who worry about athletes specializing in particular sports too early, and skewing their normal development. Some suffer overuse injuries before they've had a chance to become well-rounded athletes, or perhaps because they didn't try to become well-rounded athletes.

So, when it comes to kids and sports, I'm on the side of whoever wants kids to do lots of different activities to develop speed, balance, coordination, endurance, strength, and power as their bodies allow it.

If I had to develop a hierarchy of athletic development for children (call it the "sports guide pyramid"), I'd include four levels.

General activity would be at the base - playing tag, climbing on jungle gyms, terrorizing neighbors. Let kids make up their own games, as long as they don't involve human sacrifice.

Next I'd put slightly more specialized activities like swimming, riding a bike, and skating - whatever gets you from one place to another.

Right above that would be team and individual sports. I like soccer for speed, endurance, and footwork, but hockey, basketball, or tennis would be equivalent. Baseball is useful for speed, power, and hand-eye coordination, although the fitness benefits aren't the same. Martial arts, dancing, and gymnastics would also appear on this line. Some parents we know already have their kids involved in cheerleading, football, and wrestling, which I don't understand. (I can't think of any reason why an eight-year-old kid needs to know how to block and tackle, when history shows he can learn those skills in his teens and still go on to play at any level his size and talent will take him.) But, like I said, I try not to judge, and if parents want to get their kids into those sports, they belong in this section of the pyramid. Golf belongs here as well, for its benefits to coordination and athletic focus, although the fitness aspects are negligible.

At the tippy-top of the pyramid would be specialized physical training for a particular activity or goal.

That doesn't mean there aren't times when physical training is necessary. For example, this study of young soccer players with exercise-induced asthma shows that interval training helped them reduce their symptoms.

Conversely, this study of adolescent soccer players showed that strength training didn't significantly improve their performances in tests of agility and dribbling skills, compared to a group that did the same amount of soccer practice but didn't lift weights. There were significant differences between the two groups in strength and vertical-jump height, but those didn't translate into clear differences in skills specific to the sport. There were non-significant differences - that is, the strength-training group improved more in agility and dribbling technique by the end of the 16-week study - but there wasn't enough statistical power to draw a conclusion.

And you want to hear something really weird? The study's control group, which didn't play soccer or lift weights during the 16 weeks, actually improved more than either of the soccer-playing groups in the 10-meter-sprint test.

Which brings up an interesting question: What effect does physical maturity have on all this? Does the simple act of growing up improve a kid's speed and strength almost as much as formal strength training would?

In this study, all three groups were tested on the leg press at the beginning, at eight weeks, and at 16 weeks. The strength-plus-soccer group improved the most, adding 6 pounds to their lifts, on average. The soccer-only group added nearly 4 pounds, but the control group added 2 pounds to their leg-press strength without doing anything but getting four months older.

This study attempted to quantify the effects of maturation vs. sport-specific or fitness-specific training. It looked at elite junior soccer players between 12 and 17 years old, and found that the kids who were the biggest for their age group also performed the best on tests of strength, power, and agility, particularly the boys between 13 and 15 years old. The researchers say that size is a good marker of physical maturity, which implies better strength and nervous-system development.

Now, I'm not by any stretch suggesting that training isn't potentially useful for kids of any age, particularly if they have atypical issues they need to work around (asthma, for example). I'm just saying that the combination of general fitness, sport-specific skill training, and physical maturation takes care of just about everything through puberty. Post-puberty, it's completely different, and physical training matters a lot. Up until then, if all else is equal, it seems to me that we should just let the kids play.

Comments are open. Parents: agree or disagree? Athletes: were you (or would you have been) helped by fitness training at young ages?

Monday blog meat

• Relating to the above, this study shows that normal-weight kids are the fittest. Or, put another way, the fittest kids are most likely to be at what's considered the healthiest weight for their ages.
• Great news for self-lovers: An animal study suggests fish oil may prevent blindness.
• In other pro-supplement news (rare these days), a new study says echinacea may actually enhance the human immune system, thus preventing colds.
• Finally, according to a new survey, 30 percent of adult men, but only 9 percent of adult women, claim to have had 15 or more sexcual partners in their lives. The median is 7 partners for men, 4 for women. Remember when that was just an average night for Wilt Chamberlain?