Energy Balance during Backpacking

Abstract

Energy expenditure and energy intake were determined in three subjects during a 160-kilometer backpacking trip. Prior to the trip, heart rate and oxygen consumption during treadmill walking while carrying a backpack were measured. Subjects recorded heart rate during hiking. Heart rate was used to estimate energy expenditure based on the heart rate : oxygen consumption relationship (Heart Rate Method). Expenditure was also estimated from distance walked and elevation gained (Terrain Method). Subjects recorded food consumption, and were weighed upon finishing the hike. Mean heart rate during hiking was 105 ± 12 beats per minute. According to the Heart Rate Method, net expenditure averaged 3410 ± 955 kilocalories on days 1 – 4, and 2586 ± 974 kilocalories on day 5. Net expenditure from the Terrain Method was approximately 28 % lower. Gross expenditure, using the Heart Rate Method, averaged 4928 ± 1050 kilocalories on days 1 – 4, and 3550 ± 1052 kilocalories on day 5. Energy intake averaged 2134 ± 625 kilocalories on days 1 – 4, and 1117 ± 320 kilocalories on day 5. Expected weight loss due to the caloric deficit was 1.8 ± 0.4 kilograms, and actual weight loss was 1.7 ± 0.6 kilograms. Subjects expended nearly 5000 kilocalories per day and did not consume sufficient food to maintain body mass.

Key words

oxygen consumption - energy expenditure - energy intake - heart rate

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