For those who want to become better workers, spouses, parents, athletes or lovers, there is a new frontier in personal growth – or at least a proliferation of products, mostly hawked over the internet, that promise to help turn the last bit of untrammeled downtime (sleep) into an opportunity for improvement.

New health products have emerged, often from the margins of commerce. Old self-help approaches like subliminal 「sleep learning」 have evolved and found new life on the web.

「While you sleep!」 has become an Internet marking catchphrase. The idea plays on two classic, if contradictory, American impulses: the desire to get ahead, and the compulsion to avoid the slightest expenditure of effort.

There are diet pills sold under names like Lose and Snooze and Sleep』 n Slim, which contain collagen and which the makers say can help maximize the body』s metabolism. There are foot pads from Japan that look like tea bags and promise to drain toxins and restore energy while you sleep.

On one Web site, hypnotictapes.com, besides recordings designed to improve public speaking or break addiction to alcohol or heroin, there are programs promising to help you, at least partly while sleeping, 「Overcome Fear of Clowns」 and 「Master the Bagpipes.」

Professionals who think the boss has been a little slow with that promotion – and who have left their skepticism in their other briefcase – can try to boost their careers with the Wealth & Success Power Affirmations subliminal program (「start advertising to your own mind」). Sold through sleep learning com, it can be played through stereo pillow speakers available on the same Web site for $29.95.

Not everyone selling self-improvement while sleeping promises overnight miracles. James Schmelter, a certified hypnotherapist who runs hypnotictapes. Com out of San Francisco, said sleep learning on its own is often of only marginal benefit, which is why it is only one of four elements in his hypnosis- at –home programs, many of which he records individually for customers and sells for $98. The other three parts of the program are to be listened to awake.

But unlike the hypnotized brain, which is receptive to spoken suggestions, the sleeping brain is not so suggestible, said Dr. Michael J. Sateia, the head of the sleep disorders program at Dartmouth Hitchcock Medical Center in Lebanon, New Hampshire. 「Generally,」 he explained, 「sleep is considered to be a state of being relatively 『offline,』 as it were, with respect to extrasensory input.」

Sleep learning is a self-empowerment concept that dates back at least to Aldous Huxley』s 「Brave New World,」 published in 1932, but for most of the intervening years it could be found mainly on cassette program tucked away on self-help shelves in bookstores alongside volumes on astral projection. That all changed with the Internet.

Marc Van De Keere, for example, is one seller of sleep-learning self-improvement products who said he has noted a spike in business in recent years. Mr. Van De Keere, a hypnotherapist who operates the Web site brainwave-entrainment. Com, said he had seen sales of subliminal problem-solving and meditation products increase by a third in the last few years.

This apparent renewed interest in learning while snoozing comes at a time of increased academic research into the topic. Last year, researchers at the University of Lubeck in Germany found that gently stimulating the brain during sleep with an electrical current at a certain frequency improved the ability of test subjects to remember a string of words they had learned before a nap.

Still, Dr. Jerome M. Siegel, a professor of psychiatry at the Center for Sleep Research at the University of California, Los Angeles, said that most research he has seen indicates that subliminal sleep learning is of little or no value because 「the sound had to actually wake you before you would benefit.」 Dr. Siegel recalled rigging a speaker system under his own pillow in junior high school in a failed effort to learn French. 「Even when you』re sleepy, but not asleep,」 he added, 「you don』t learn very well.」

A study in 1992 by the British Psychological Society dismissed the concept of sleep learning, finding that it can 「only occur if the sleeping person is partly awakened by the message.」 But such findings did not kill off interesting the concept and its seductive, something-for-nothing allure.

For Candace Kinsella, a retired nurse in Largo, Florida, who wanted to reduce by a few sizes, diet pills were not enough, so she turned to a weight-loss sleep program that not subliminal, but consists of spoken message like 「eat more vegetables,」 she said. Despite the potential distraction of someone talking while you『re trying to sleep, she said the program, which is sold on the Web site Robert-egby.com, is relaxing. 「It』s like going to sleep with the TV on,」 she said. She credits it with helping her lose 22 kilograms over one year.