Grade-school gym teacher Valentino Taguding has witnessed the deterioration. In his 21-year career, he has seen the young physiques in his care soften steadily as children become more idle.

“The muscle tone is not quite there. They’re not as active,” said Taguding, a physical education instructor at Island Creek Elementary School in southern Fairfax County.

So he and his boss, Principal Susan Owner, praised the goal of a state bill requiring a sharp increase in time that Virginia kids spend in PE class from kindergarten through eighth grade.

But the two educators worry about how the measure would work in practice. The biggest concern: What subjects would be sacrificed to free up the time?

“The school day is only so long,” Owner said. “Music should be worried.”

That sums up the key arguments for and against the bill, which Gov. Robert F. Mc­Don­nell (R) is deciding whether to sign. Sponsored by a pair of doctors with seats in the General Assembly, the measure won overwhelming approval from lawmakers disturbed by the national epidemic of childhood obesity.

Despite the easy passage, the bill is drawing strong opposition from school boards, administrators and teachers unions, which are urging Mc­Don­nell to veto it. He hasn’t said what he’ll do.

I vote for signing it, thus forcing kids to run more relays, do more pull-ups and play more dodge ball. I say that even though I’m no jock. When I was in school, my worst grades were in gym (and handwriting), but I always enjoyed PE. It was fun, and I was vaguely aware that it was also good for me.

Gym class is more important now. Research confirms Taguding’s impression that children are less fit than in the past. Nearly a third of Virginia children and teens are classified as overweight or obese, according to the Virginia Foundation for Healthy Youth.

The reasons are numerous and well-known. Computer games have become more popular than tag. More kids commute to school by bus or car than on bikes or legs. They swallow too much sugar in their sodas and fat in their french fries.

First lady Michelle Obama has made childhood obesity one of her signature issues, and Virginia first lady Maureen Mc­Don­nell is right there with her.

Mc­Don­nell, whose own vigorous physical activities once included time as a Redskinette, is a leading backer of the healthy youth foundation. Supporters of the bill hope she’ll quietly urge her husband to approve it.

The legislation would require all Virginia schools by 2014 to have an average of 150 minutes a week of physical education instruction in grades K-8. In elementary school, that would be in addition to recess. In Fairfax and Arlington County, the bill would typically force elementary schools to add between 30 and 90 minutes of PE class each week.

The Virginia bill is similar to one passed in the District last year.

In Montgomery and Prince George’s counties, where there’s no state requirement, elementary school children generally have 50 to 60 minutes of gym class each week.

Opponents say it’s up to families, not schools, to promote a healthy lifestyle for children. It’d be great if families did so, but they don’t. Overprotective-ness is partly to blame.

“It a sign of the times. They’re worried about children going out and playing unsupervised. We did that [as children], but now parents keep them inside [where they] play video games,” Taguding said.

The nation needs to turn this trend around, and the Virginia bill is one way to do it.

“Nobody blames the schools. We recognize it’s a societal issue. But the schools are in a unique position to address it,” said Del. John M. O’Bannon III (R-Henrico), the bill’s sponsor in his chamber. Both he and the Senate sponsor, Ralph S. Northam (D-Norfolk), are neurologists.

Those arguments, along with personal experience, explain why the House approved the bill by more than a 2-to-1 margin and the Senate approved it 38 to 2.

“I think people get it. You don’t have to walk down the street very far to see the problem,” O’Bannon said.

Nonetheless, powerful opposition remains.

The Fairfax School Board sent McDonnell a detailed two-page letter opposing the bill. The school system said it lacked time to add classes and would have to pay between $18 million and $24 million to hire new PE teachers. Also, some school systems don’t have enough exercise rooms.

I recognize the costs, but the schools have three years to find ways to make it work. Also, as the economy recovers, more money could be raised.

As for finding the necessary class time, we could spread the pain by trimming five minutes a day off every other subject or lengthening the school day (working parents would welcome that).

I’d certainly prefer taking one of those steps rather than cutting music or art.

The federal education law is called No Child Left Behind. A Fairfax educator called this bill “No Child Left on His or Her Behind.”

Virginia should follow the District’s lead on this one.