LOS ANGELES » In Santa Monica, women in skintight yoga pants and sunglasses with lenses the size of lazy Susans trot up and down giant cement steps. Men who look like they could hoist a Mercedes hang from a telephone pole, and trainers roll out yoga mats in the middle of the sidewalk.

In Silver Lake, guys can be seen using children's playground equipment to aid them in bicep development, tai chi lovers gather on the campus of the University of California, and aerobics happen on random bits of grass downtown.

Its mild climate, the lack of parks in its more dense areas and the propensity here to treat fitness a bit like performance art combine to make Los Angeles a municipal force in the art of improvised exercise. From the wealthy neighborhoods of Brentwood, where a traffic median is used as a track, to tiny parks in low-income neighborhoods downtown, where picnic benches are used for bench presses, the city often looks like one giant outdoor gym.

“;The way the city was planned, planners were not able to incorporate the amount of park space it needed,”; said Alina Bokde, the executive director of the Los Angeles Neighborhood Land Trust, a nonprofit group that creates parks and community gardens. “;So people tend to be very creative with the built-in environment they have.”;

Los Angeles is 10th among 13 big cities in the amount of park acres - just under 24,000 - it offers as a percentage of the city's total area, according to the Trust for Public Land, a nonprofit preservation group. (Yes, New York, you are first, but L.A. still has better asparagus.)

The city has various sets of steep staircases ascending bluffs and hills, the most famous near Fourth Street in Santa Monica, where two large sets attract scores of residents, who huff and puff their way to the top, iPod and egos firmly attached.

Kiki Kyle, a singer who lives in nearby Venice, wears her 4-year-old son as a large weight as she pounds her way up and down the stairs that hover above the Pacific Ocean at least once a week. To quiet him, she offers an ear bud and words of encouragement.

“;He makes me strong,”; Kyle said. “;I like the beach, and he can dance here if he wants to, too.”;

At the bottom of the stairs, runners cantering between the two sets of steps dodge trainers with their weights, their actor-waiter clients splayed like so much human rickrack along the sidewalk. Men hang from a telephone pole, pulling upward.

Last year, there was a bit of a set-to between exercise fanatics using the Fourth Street stairs and residents of Santa Monica who had grown weary of the early morning whistles of trainers and people who insisted on doing push-ups outside their door.

The Santa Monica City Council has since banned the use of exercise equipment and professional fitness programs on the Fourth Street median, although no citations have been issued. “;I expect it to be enforceable real soon,”; said Adam J. Gwartz, a neighborhood resource officer with the Santa Monica police. “;I really don't anticipate many tickets.”;

For now, free weights continue to emerge from trunks. Mats are rolled out. Instructions are barked in tones often reserved for people who do not pick up their towels from the floor. Beach town laws are no match for those in search of strengthened hamstrings.

Jay Kerwin, who owns Boot Camp L.A., runs his clients up and down grassy hills, sometimes in the crab position, and past the fabricated elephants sitting in the oozing tar of the La Brea Tar Pits along the Miracle Mile. It is convenient, he said, adding, “;You don't need a lot of equipment to run up stairs.”;

Children's equipment also gets a grown-up workout. Last week, in Bellevue Park in Silver Lake, Michael Castro used a playground to anchor his ankles as he worked his abs, the violet jacaranda leaves falling nearby.

Sam Lopez, a trainer in Silver Lake, demonstrated four ways to use a picnic bench for push-ups near the reservoir there. You can use the bench part, he said, or pop your sneakers on the table part for a greater challenge.

“;We get it done,”; he said.

His client Lily Cano concurred. “;I think it's nice to be here breathing fresh air as opposed to the gym, where you breathe everyone else's air,”; Cano said.