The downtown Berkeley Y has something almost no other gym in the East Bay has: children. Kids running past you up the stairs, kids rummaging through jackets at the lost-and-found, kids digging indeterminate matter out of their ears in the lobby. Most gyms are exclusively adult affairs, catering to fitness nuts and personal trainers; weight-training is particularly fraught with the perils of self-absorption. But the Berkeley Y is an admirably multigenerational facility whose members include both the very young and the very old. It's an almost charming relief that somewhere in this country, the demographic most yearned after by marketers and TV stations has to acknowledge that other age groups and types actually exist.