Q. Did those old exercise machines that quickly oscillated a belt around the midsection have any fat-burning benefits?
A. In a word, no, though some modern studies indicate that gentle full-body vibration has some other health benefits.
For the flab-flapping belts, the underlying theory was apparently that the vigorous mechanical massage would break down fat cells for removal by the bloodstream or lymphatic circulation, or that it would simply tone the flabby area.
These and other elaborate passive-exercise machines were the descendants of equipment for both active and passive exercise developed by a Swedish doctor, Gustav Zander, who introduced them to Americans at the 1876 Centennial Exhibition in Philadelphia. Some of his devices resemble the tension-based machines used in modern health clubs.
The vibrating belts enjoyed their greatest popularity from the 1930s to the 1960s, but no formal scientific studies proved any weight-loss or muscle-toning benefits.
One study of low-magnitude vibration involved overweight mice. The results, reported in 2012 in The Journal of the Federation of American Societies for Experimental Biology, showed improved bone strength and more immune cells, but not weight loss.
Hand-wringing over sanitizers
Q. Does the widespread use of hand sanitizers risk breeding resistant bacteria?
A. Alcohol-based hand sanitizers containing 60 percent to 95 percent alcohol do not increase the chances of producing resistant bacteria, according to research cited by the Centers for Disease Control and Prevention, but some other kinds may do so.
Furthermore, even the recommended kinds of sanitizers do not eliminate all germs, the CDC warns in its guidelines for sanitizer use. Soap and water are still more effective than hand sanitizers for removing or inactivating certain kinds of germs, like Cryptosporidium, norovirus and Clostridium difficile, especially when hands are grimy, not just contaminated.
Hand sanitizers that are not based on alcohol - notably those that rely on substances called chlorhexidine and triclosan - are both less effective and slower to act than alcohol, other studies have found, and both of these agents do present a risk of producing bacterial resistance.
Triclosan especially may increase the risk of antibiotic-resistant E. coli and salmonella, a 2006 review concluded, possibly presenting a public health hazard with widespread use.