Those vows to hit the gym more often or adopt a new exercise regimen seem to be part of the human condition. And although your choice of outfits is secondary to the search for motivation, the right clothing can’t hurt.

"Women want to look good while exercising," says Kelly Cooper, vice president of merchandising, design and product development for Athleta, the Gap-owned athletic and lifestyle manufacturer and retailer. "When you’re wearing things that are more flattering, then you’re more motivated to work out."

Many of us appear to agree with her. In 2010, Americans spent more than $30 million on women’s fitness clothing, a 2 percent increase over the previous year.

This spring, fitness brands are focusing on pieces that are streamlined, lightweight and versatile enough to wear post-workout.

The most ubiquitous workout staple for women is the basic black capri-style legging from brands such as Lululemon or Hard Tail, which generally retail anywhere from $70 to $90. "The tight capri legging doesn’t die," says Riale. "Everyone wears them. We can’t keep them in stock, even in New York when it’s cold."

The cropped and skinny silhouette of the capri has eclipsed the boot-cut workout pants of three or four years ago, and fitness instructors are happy to have their clients wearing more streamlined gear. "The more form-fitting the fabric you wear is, the more it will stay out of your way and you can focus on your technique. Also, the instructor can see your form and make proper corrections," says Kimberly Weber, executive director of Physique 57, a cardio program based in Beverly Hills, Calif.

Yoga teacher Clio Manuelian agrees with the idea that less is more. "In yoga, the teacher needs to see the shoulder blades," she says. "There’s so much focus on that area, so wearing something like a tight tank top or a racer-back tank top is good so the trapezius (muscle) is visible."

On the footwear front, companies such as Nike are also adopting this less-is-more attitude. The Nike Free Quick and the Nike Free TR Fit are built with minimal construction to let the foot act as if nothing is there and move as it would naturally.

Staying in your workout clothes to run errands or go pick up the kids is certainly a familiar concept to many women living in warm climates. The market for clothes that layer over those tight leggings — so as not to feel quite so exposed when running into Whole Foods for a smoothie — has grown larger in the last several years, further blurring the lines between fitness and fashion.

"You see it all the time," says Karyn Riale, a national retail buyer for Equinox gyms. She notices women buying and wearing a lot of what she calls "to and from the gym" jackets — generally a fitted zip-up structured jacket with a fashionable element, such as an exaggerated funnel or fold-down neckline and a subtle print.

Athleta focuses heavily on items that layer over gym clothes. "Layering is a huge trend for us for spring," Cooper says, adding that tank-style cotton dresses and skorts (a combination of "skirt" and "shorts") are big sellers.

Alo, an L.A-based company, manufactures a collection of apparel designed to transition from the gym to the street. Fitted, funnel-neck, zip-up jackets and lightweight sweatshirts layer easily over more body-conscious workout basics such as leggings and a fitted tank top or T-shirt. Performance apparel, such as tank tops with a built-in bra, come in a bright mix of colors.

When it comes to long runs or marathon yoga sessions, manufacturers are addressing issues such as chafing, irritation and odor. Consider:

Lululemon has created a pair of yoga pants that aren’t just minimal in style, they’re also minimal in care. The Silverescent Luon pant is made to withstand lengthy yoga retreats where washing your workout wear after a day of sweating isn’t necessarily an option. The pant wicks away sweat, is quick-drying and has anti-odor technology sewn into the company’s signature Luon fabric.

The sleeves of the new Nike Cyclone jacket are articulated and allow for optimal range of motion to avoid chafing and reduce irritation.

And then there is the clothing that claims to enhance and tone the body during a workout. Reebok has taken the same approach to clothing that it did with its line of Easy Tone sneakers. The fitted tops, capri pants and shorts are equipped with bands that, according to the company, create resistance to help tone and strengthen muscles and encourage better posture and body alignment.

Lytess claims its Slimming Leggings drain fluids and activate lipolysis (the hydrolysis of fats resulting in the production of carboxylic acids and glycerol). Caffeine and shea butter are embedded in the fabric, which supposedly reduces fat and smoothes the skin for more toned thighs and hips.

Whether or not you believe those claims, Tracie Hendricks, a group fitness instructor at Equinox gym, says toning clothes can offer benefits. "It might make a difference in someone with bad posture. Any time you stand up straighter, you’re going to engage your core and lengthen your spine," Hendricks says. "But do I believe you can get a yoga butt by putting on pants? No, yoga will give you yoga butt."