Validity of the ActiReg system and a physical activity interview in assessing total energy expenditure in long-term survivors after total gastrectomy.

BACKGROUND & AIMS: Malnutrition is common after total gastrectomy. There is a need for clinically useful methods to assess energy requirements. We aimed to validate measurements of energy expenditure by an activity monitor (ActiReg) and a physical activity interview (HPAQ(modified)), in long-term survivors after gastrectomy for gastric carcinoma, using doubly labelled water as reference method. METHODS: Total energy expenditure (TEE) was estimated by DLW (14 days), ActiReg (3 days) and HPAQ(modified) (7 days) in 15 patients. Measurements were repeated after 12 months. Basal metabolic rate was measured with indirect calorimetry. RESULTS: ActiReg and HPAQ(modified) both underestimated TEE by 180 (+/-254 SD) and 130 (+/-326 SD)kcalday(-1), i.e. 14% vs. 12%, respectively. However, this was evident only at higher levels of physical activity (PAL(DLW)> or =1.65), whereas at lower levels (PAL<1.65) no difference was found. There were no changes in TEE over time independent of the method used. DLW and ActiReg had approximately the same width of the 95% confidence interval of this estimate, while it was 2.4 times larger by HPAQ(modified). CONCLUSION: Both simple methods underestimated total energy expenditure at higher, but not at lower physical activity levels. The ActiReg method appears useful to estimate changes in TEE over time.

Validation of ActiReg to measure physical activity and energy expenditure against doubly labelled water in obese persons.

ActiReg is an instrument that uses combined recordings of body position and motion to calculate energy expenditure (EE) and physical activity (PA). The aim of the study was to compare mean total energy expenditure (TEE) measured by ActiReg and doubly labelled water (DLW) in obese subjects. TEE was measured by the DLW method during a period of 14 d in fifty obese men and women with metabolic risk factors. During the same period ActiReg recordings were obtained for 7 d. RMR was measured by indirect calorimetry and also estimated by standardized equations. Because EE may be disproportionately increased in obese subjects during weight-bearing activities, we established a new set of physical activity ratios (PAR). These ratios were based on oxygen uptake measurements during treadmill walking. The mean TEE according to the DLW was 13.94 (sd 2.47) MJ/d. Mean TEE calculated from the ActiReg data and measured RMR was 13.39 (sd 2.26) MJ/d, an underestimation of 0.55 MJ (95 % CI 0.13, 0.98; P = 0.012) or 3.9 %. RMR derived from standard equations based on weight, age and sex were overestimated while the RMR based on fat-free mass values in addition was underestimated. Despite slight underestimation ActiReg may be used to measure TEE in obese subjects on two premises: RMR should be measured, and the increased EE during weight-bearing activities in obese subjects should be considered.

Description and validation of the ActiReg: a novel instrument to measure physical activity and energy expenditure.

The ActiReg (PreMed AS, Oslo, Norway) system is unique in using combined recordings of body position and motion alone or combined with heart rate (HR) to calculate energy expenditure (EE) and express physical activity (PA). The ActiReg has two pairs of position and motion sensors connected by cables to a battery-operated storage unit fixed to a waist belt. Each pair of sensors was attached by medical tape to the chest and to the front of the right thigh respectively. The collected data were transferred to a personal computer and processed by a dedicated program ActiCalc. Calculation models for EE with and without HR are presented. The models were based on literature values for the energy costs of different activities and therefore require no calibration experiments. The ActiReg system was validated against doubly labelled water (DLW) and indirect calorimetry. The DLW validation demonstrated that neither EE calculated from ActiReg data alone (EEAR) nor from combined ActiReg and HR data (EEAR-HR) were statistically different from DLW results. The EEAR procedure causes some underestimation of EE >11 MJ corresponding to a PA level >2.0. This underestimation is reduced by the EEAR-HR procedure. The objective recording of the time spent in different body positions and at different levels of PA may be useful in studies of PA in different groups and in studies of whether recommendations for PA are being met. The comparative ease of data collection and calculation should make ActiReg a useful instrument to measure habitual PA level and EE.