ESCONDIDO -- Instructor Sharon Timko was ready when a senior in her new fitness class declared a memorization exercise as "hard," with several other students nodding vigorously in agreement.

"It's supposed to be hard," Timko told the group Monday during the first adult education program in San Diego County to offer brain fitness classes -- a fast-growing national trend.

As baby boomers age, marketplace researchers have noticed a growing demand for brainpower classes, software and games.

On Monday, for example, the marketing research firm SharpBrains.com released its latest report showing that the market in brain fitness software grew from an estimated $100 million in 2005 to $225 million in 2007 and $265 million last year.

At Timko's Brain Fitness for Older Adults class at Escondido Adult School on Monday, students plugged earphones into a bank of computers to work on audio recall and memorization exercises.

Timko said that just as physical strength and agility declines with age, so do cognitive abilities to think, comprehend and remember.

Timko said her mental strength- and speed-building classes work much the same way that physical fitness buffs build strength over time. Instead of jogging or jumping jacks, her students progress from simple to increasingly complex computer software exercises designed to enhance cognitive abilities.

Tuition costs $15 for the 40-hour program that began in April and will go through June.

A 40-hour visual processing class is scheduled in the fall at the adult school campus, a lifelong-learning arm of the Escondido Union High School District.

Linda Anselm of Valley Center said she joined the class after being laid off, and that she already has noticed more brainpower.

"I'm remembering more and more," she said. "I'm also learning how to work on the computer, and now I don't have to refer to my notes so often when I do."

At 57, Allison Pickering of Escondido, assistant principal for adult education at the Escondido school district, said she's the youngest in the current class of 20.

"You have to continually challenge the brain. I'm feeling sharper," said Pickering, who is taking the class with her mother, Carolyn Pickering, 87, the oldest student.

"I'm sure my brain has gotten rusty," Carolyn Pickering said. "I already feel I'm benefiting."

Principal Dom Gagliardi said his school's program is patterned after those he visited elsewhere in California that are using PositScience Corp. software developed by researchers at the University of San Francisco.

"You have to concentrate," he said. "It's not an easy program."

Yet despite the tough mental workouts required, he heard only positive feedback in his classroom visits to other communities, Gagliardi said.

"This one particular stroke victim had been able to get his driver's license back" as a result of the class, Gagliardi said.

Although the Escondido class is aimed at the 55-plus set, it's OK for younger students to enroll.

"Some proponents want to have brain fitness centers on high school campuses," Gagliardi said. "We think this is going to be really popular."

For more information about Escondido Adult School programs, visit www.escondidoadultschool-rop.org.