New Orleans, LA - The great nuclear-powered aircraft carriers now on station in the Indian Ocean are 1,092 feet long, or about one-fifth of a mile. These largest of warships have more than 11 decks, a flight deck area measuring four-and-one-half acres, and more than 3,000 rooms and compartments throughout. Today’s sailors, male and female, expend considerable energy walking about these ships. Accordingly, their energy needs must be supported by a diet that is nutritious and meets their caloric needs.

It is accepted that energy requirements vary with activity level. The energy requirements for the vast number of shipboard occupations are unknown and not necessarily the same for women as they are for their male counterparts. The use of doubly labeled water (DLW), composed of special forms (isotopes) of hydrogen and oxygen, has been used in previous studies to estimate the energy expenditure of various military personnel doing their jobs in a variety of places. The results from these tests, have been accepted as highly accurate, but expensive.

A team of researchers has suggested that pedometer based-technology may offer the potential for a lower-cost alternative to the DLW method for determining total daily energy expenditure of sailors at sea. A new type of pedometer was used that measures whether a person is running, walking or shuffling and records the distance a person covers on foot in each type of activity by responding to the body motion at each step. What is unknown is whether energy expenditure estimates obtained with these less expensive pedometers are accurate.

This question was addressed in the study, “Prediction of Shipboard Total Daily Energy Expenditures Using Pedometry.” The authors are William J. Tharion, Miyo Yokota, and Reed W. Hoyt, all from the U.S. Army Research Institute of Environmental Medicine, Natick, MA; Mark J. Buller, from GEO-CENTERS, Inc, in Natick, MA; and James P. DeLany, from the Pennington Biomedical Research Center, Baton Rouge, LA. The researchers will present their findings in detail during the American Physiological Society’s (APS) annual meeting, part of the "Experimental Biology 2002” conference. More than 12,000 attendees will attend the conference being held at the Ernest N. Morial Convention Center, New Orleans, LA from April 20-24, 2002.

Seventeen U.S. Navy sailors (seven males, ten females) volunteered to participate in the study. The Navy classified their occupations as physically active or sedentary.

The study took place during an 8-day training exercise at sea aboard an amphibious assault ship resembling a small aircraft carrier. Testing consisted of two estimations of total daily energy expenditure (TDEE) in kcal by the DLW method (Reference Standard), but expensive; and pedometers worn on the shoe (experimental method), which is less expensive but not validated

Activity was recorded in four modes (running, walking, slow foot movements, and no activity). Resting metabolic rate (RMR) was estimated using a previously published equation: RMR (kcal/day) = 500 + 22 (Lean Body Mass) . Unlike previous studies, the logger device was worn in the laces of the shoes and study volunteers existed in a free-living environment where they were able to run, walk, have other slow foot movements like shuffling, and no activity. Multiple regression analyses were used to determine the best prediction equation for TDEE from pedometry measures and to compare the model's calculated TDEE to that measured from DLW (the reference standard).

The Mean + SEM of total daily energy expenditure as measured by DLW was 3000 + 153 kcal/day compared to that predicted by pedometry which was 3023 + 99 kcal/day. This prediction equation can predict with 95 percent confidence TDEEs within + 193 kcal.day.

Conclusions

This study demonstrated that pedometers provided significant accuracy in assessing total daily energy expenditure (TDEE). However, because of the abundance of ramps and ladders on ships the predictive capabilities of pedometry may be better when trying to assess TDEE on land. Pedometry does appear to be a possible alternative and cost-effective method to the DLW when assessing TDEE.

In this modern age of warfare, this may be vital as the United States Navy embarks upon a modernization program and extends deployments to meet worldwide contingencies. Measuring TDEEs will provide better understand the energy requirements of soldiers, sailors, airmen, and Marines so that nutritional requirements for various deployments can be optimally met.

- end -

***