Updated

Spring is here and women everywhere are beginning to panic at the approach of bikini weather.

If you've let your workout slide under the comfort of bulky layers and winter coats, experts say now is the time to jumpstart a year-round fitness regimen.

"Spring shape ups, getting ready for that bikini are always a great thing to help inspire you to stay in shape for the long run," said Jeanette Jenkins, an LA-based fitness expert and founder of The Hollywood Trainer company.

For the very determined, Jenkins, who counts Queen Latifah and Christina Applegate among her clients, has created the Bikini Bootcamp DVD, a fierce, non-stop regimen designed to whip that winter body into summer shape.

"It's a super-high intensity workout to really maximize results so you can look good in a bikini," said Jenkins. "When you have a very short amount of time you need quick results."

The first 30 minutes rotate high-intensity cardio activities, like sprints, squat thrusts and jumping jacks.

"You do one circuit of four exercises for five minutes, then switch to another," she said.

That's followed by 30 minutes of sculpting moves to tone and define.

"I want it to be almost like carving out a diamond," she added.

Jenkins said the workout is so intense she recommends doing it only three times a week.

"The first time you do it you're going to be sore for five days. I'm not kidding," she said.

Crunch, the national fitness chain, has also been holding Beach Body classes every spring for the last three years.

"It's a full-body conditioning class with focus on a different body part each week," explained Carol Johnson, group fitness coordinator and instructor.

"We do specific exercises that target the thighs, abs, triceps. The focus is about looking great in your bikini and looking forward to the beach or pool."

The class uses weights and body bars for toning, and jumping jacks to get the heart going.

"We get all ages. And I get men, which is fantastic," Johnson said.

Mary Jayne Johnson, an exercise physiologist from the American Council on Exercise, says now is the time to tone for summer but she warns against unrealistic expectations.

"Seasonal goals are fine," she said, "but it can be like yo-yo dieting applied to the exercise world. Any woman who's ever gone into a department store and put on a bikini has had a panic attack," she said.

"But you need attainable goals. Is putting on a string bikini where you're ever going to be in your life?"

Jenkins also urges self-acceptance.

"Love yourself as you are now so you're not thinking that life will change dramatically when you get to this new body shape," she said.

"Find one or two parts that you absolutely love on your body and let that inspire you to work on the rest. Stay committed and consistent. Don't beat yourself up."