When it comes to fitness, experts say men generally want to be bulkier and women want to be trimmer and everyone wants to do what they are good at.
That's why as more women tackle brawny boot camps and men seek flexible peace on the yoga mat, crossing traditional gender lines, intelligently, can be a good idea.
"Women want to lose body fat, men want hypertrophy (bulk)," said Geralyn Coopersmith, national director of the Equinox Fitness Training Institute.
There are also hormonal, structural and body composition differences between the sexes, said Coopersmith, who trains the personal trainers for the chain's fitness centers.
"So if they're both training for a marathon they'll train in very similar ways but we'll look out for different things."
Women's wider hips leave them more prone to knee injuries, while men, pound for pound, will always have more lean body tissue.
"Technically the man is more fit in that regard," she said.
It's harder for women to tackle extreme workouts, such as Crossfit or P90X, Coopersmith said, but they can do it.
"They're not going to beat the men but will probably get pretty good at it and get very fit," she said, adding that too many young, healthy women don't challenge themselves enough.
Spot the difference
Dr. Michele Olson, an exercise physiologist with the American College of Sports Medicine said while everyone needs aerobic, strength and flexibility, the activities needed to achieve it can be very different, depending gender and age.
"In the early years women need to focus on bones and men on aerobics," said Olson, a professor at the Auburn University Montgomery Human Performance Lab, in Alabama.
She added that research shows it's important for younger women to take on activities with sufficient impact, such as jogging, jumping rope or step aerobics, at least 20 minutes twice a week, to develop good bone density.
"Bone density can fail women in their 40's," said Olson, "while men tend to have robust bones until very late in life."
She added that heart health is especially important for men, who are plagued with heart disease at a younger age. They need to focus on the correct exercises for the heart, including low-impact cardio exercises like bicycling or swimming.
Women at any age should lift weights, she said, adding interval-style training is more efficient in burning the mid-belly fat women tend to store after menopause.
"It doesn't have to be a boot camp. You can do it on a treadmill by adjusting speed or incline at one-minute intervals," she explained.
As men age, their lack of flexibility catches up with them, but estrogen has made the tendons of women more elastic.
"Women and men both play to their strengths," she said. "Even as children, athletes naturally select what they feel they're good at."
Connecticut-based fitness instructor Ellen Barrett believes the genders require different fitness formulas.
Even a simple bicep curl might not work for a woman, whose range of motion is generally greater, said Barrett.
Super-intense, military-style workouts and long-distance running are among the activities Barrett feels are made for men, while Pilates and yoga are so much more woman-friendly.
Barrett said when she attends a yoga class with her husband "it's like a tale of two cities."
"I feel like I've had a massage," she explained. "My husband has to recover."