Calorimetric Validation of the Caltrac® Accelerometer During Level Walking

Abstract

The primary purpose of this study was to compare the Caltrac accelerometer output with measured energy expenditure (Ee). Twenty-five volunteers (10 men, 15 women) walked on a level motor-driven treadmill at four different speeds (54, 81, 104, and 130 m.min-1) with the Caltrac device affixed to the waistline. Each of the four experimental trials lasted eight minutes, and the testing was completed within an hour. During the test, oxygen consumption (VO2) (in L.min-1 and in mL.kg-1.min-1) and nonprotein respiratory exchange ratio were monitored by the Beckman Horizon metabolic cart. The accelerometer output at the end of each exercise bout was also monitored and subsequently divided by 8 to convert the readings to counts.min-1. The mean VO2 (L.min-1) at steady state (ie, 6th-8th minutes of exercise) was converted to a caloric value. We obtained a moderate correlation coefficient (r) of .76 between the accelerometer output and the VO2 (mL.kg-1.min-1) and a high correlation coefficient of .92 between the Ee and the accelerometer readings. The Caltrac accelerometer output (counts.min-1) was significantly higher (p less than .01) than the Ee (kcal.min-1) at the four walking speeds. The difference between the accelerometer output and the Ee ranged from 13.3% to 52.9%. The data were further analyzed with linear, polynomial, multiple, and stepwise regression models. The results of the analyses revealed that the Caltrac accelerometer output is a valid predictor of Ee during level walking when the appropriate regression equation is used to adjust the values.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of placement and orientation of body-fixed accelerometers on the assessment of energy expenditure during walking

“…The best prediction of EE~,.t was obtained from the measured IMA variables at the lower back (r=0.92-0.97). These results are comparable to those reported by Balogun et al and Haymes and Byrnes, who reported correlations of 0-92 and 0-94, respectively, between energy and expenditure and IMA measured in vertical direction with a body-fixed uniaxial accelerometer at waist level during walking (BALOGUN et al, 1989;HAYMES and BYm'qES, 1993). The influence of accelerometer orientation on IMA was evident, especially at the limbs and during the lowest walking velocities.…”

A triaxial accelerometer and portable data processing unit for the assessment of daily physical activity

“…These correlations are higher than those found for standardized activities in the laboratory using the uniaxial Caltrac [6], [39]- [41] or the TA of Meijer et al [5], [23]. Discrepancies between measured and estimated values of during high-intensity activities and low intensity activities were also smaller than those reported for the Caltrac [17]- [19] and the accelerometer of Meijer et al [23].…”

“…Reproducibility of acceleration counts measured at the low back during various exercises was good ( 0.94) and a pooled correlation coefficient of 0.74 was found for the relationship between acceleration count and energy expenditure [6]. From more recent studies it can be concluded that Caltrac output shows good correlation with measured energy expenditure during separate well-defined activities in the laboratory, like treadmill walking ( 0.68-0.94), but generally overestimates energy expenditure under these circumstances [17], [18]. Under freeliving conditions the uniaxial Caltrac can be used to distinguish among interindividual levels of daily physical activity, but tends to systematically underestimate the energy requirements when compared to whole body indirect calorimetry [19] or the doubly labeled water method [20], [21].…”

Improvement of walking speed prediction by accelerometry and altimetry, validated by satellite positioning

“…Therefore, many studies have attempted to test the accuracy of accelerometry for assessing walking speed and the related energy expenditure. Good correlation was found between walking speed and the integral of the modulus of body acceleration in 0% slope conditions (BALOGUN et al 1989). Under variable uphill or downhill conditions, however, prediction of speed or energy expenditure is not possible (MELANSON andFREEDSON, 1995, TERRIER et al, 1999).…”