Activity monitor outperforms pedometers

NEW YORK, Sep 28 (Reuters) A new physical activity monitor does a better job than standard pedometers of keeping track of how far and how fast a person walks each day, a new study shows.

Dr. Cormac G. Ryan of Glasgow Caledonian University in the UK and colleagues compared the new monitor, known as the activPAL (made by PAL Technologies, Glasgow), in a head-to-head trial with two commonly used pedometers, the Yamax Digi-Walker SW-200 and the Omron HJ-109-E.

Pedometers count the number of steps a person takes. Most are worn at the waist. The activPAL, which weighs 20 grams, is stuck to the front of the thigh with an adhesive, and works by measuring acceleration. It records cadence and step number for each walking period, and data from the device can be downloaded onto a computer.

Twenty study participants tested each device at a series of speeds on a treadmill and outdoors. Each wore four of the activPAL monitors and two pairs of the pedometers so the researchers could check for variability between devices of the same type. The researchers used videotapes of the walkers as their ''gold standard'' of measurement.

The activPAL was quite accurate at all speeds, the researchers report in the British Journal of Sports Medicine, with an overall error rate of less than 1.11 per cent for measuring step number and cadence.

The Yamax device had a roughly 33 per cent error at the slowest walking speed of 0.9 meters per second, while the Omron had an error of about 23 per cent at this speed. Accuracy improved as walking speed increased, with errors dropping to 5 per cent or less for speeds of 1.56 meters per second or greater.

The researchers conclude that the activPAL is an effective device for measuring cadence and step number in healthy adults, but that further research is needed to determine if it will also be useful in populations with a markedly different gait, such as children or the elderly.

The main disadvantage of the activPAL device is its considerably greater expense, the researchers note. ''This has to be balanced against the quality and detail of information provided by these devices,'' they add.

One of the study's authors helped invent the activPAL and is a director of the company that makes the device. However, he did not participate in collecting or analyzing the study data, according to a disclosure statement.

REUTERS SAM VC0940