Today's tennis stars aren't preoccupied by building muscle and increasing the power behind their rackets. Most of them are focused on speed, agility and their movement across the court.

That has inspired a curious trend: Male tennis players appear to be getting skinnier.

In the modern sports world, weigh loss is something of an oddity. Professional basketball, baseball and hockey players value muscle mass, and many young players enter those leagues in need of adding weight to improve their performance.

In tennis, though, almost the opposite seems to be happening. According to a story in The Wall Street Journal, Canada's Milos Raonic has worked hard to drop 12 pounds from his 6-foot-5 frame. That comes after England's Andy Murray adopted a training regimen focused on speed, while global star Roger Federer, in his twilight years as a professional, has continued to emphasize court movement.

This trend follows roughly two decades of tennis players who poured their efforts into bulking up and developing formidable power games. By the time power players like Andy Roddick retired in the past few years, his kind was something of a dinosaur going extinct.

Part of that is an adaptation to how tennis courts have changed: The WSJ notes that as players grew more powerful, courts were designed to be grittier and slower, rewarding players who valued defense and agility over power.

The current generation is the product of those changes.

One curious footnote in this trend is that women have by and large failed to match men in slimming down. Stars like Serena Williams -- currently the world's No. 1 female -- continue to dominate with muscular physiques and playing styles geared toward power and strength.

Check out Samantha Stosur in action at Australian Open. Looks like she hasn't skipped any visits to the gym.

It's worth noting that while some tennis stars have emphasized weight loss, others have found that building a lean physique doesn't necessarily produce a significant drop in weight. Muscle strength is still important, but few men value strength at the expense of agility and speed.

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