For total EE , correlation coefficients were statistically significantly lower in uniaxial compared to multisensor devices .
For active EE , correlations were slightly but not significantly lower in uniaxial compared to triaxial and multisensor devices .
The high level of heterogeneity in the validation studies is only partly explained by the type of activity monitor and the activity monitor outcome .
Triaxial and multisensor devices tend to be more valid monitors .
The assessment of physical activity in healthy population s and in those with chronic diseases is challenging .
The aim of this systematic review was to identify whether available activity monitors ( AM ) have been appropriately vali date d for use in assessing physical activity in these groups .
Real-time estimation of daily physical activity intensity by a triaxial accelerometer and a gravity-removal classification algorithm.
We have recently developed a simple algorithm for the classification of household and locomotive activities using the ratio of unfiltered to filtered synthetic acceleration ( gravity-removal physical activity classification algorithm , GRPACA ) measured by a triaxial accelerometer . The purpose of the present study was to develop a new model for the immediate estimation of daily physical activity intensities using a triaxial accelerometer .  A total of sixty-six subjects were r and omly assigned into validation ( n 44 ) and cross-validation ( n 22 ) groups . All subjects performed fourteen activities while wearing a triaxial accelerometer in a controlled laboratory setting . During each activity , energy expenditure was measured by indirect calorimetry , and physical activity intensities were expressed as metabolic equivalents ( MET ) . The validation group displayed strong relationships between measured MET and filtered synthetic accelerations for household ( r 0·907 , P < 0·001 ) and locomotive ( r 0·961 , P < 0·001 ) activities . In the cross-validation group , two GRPACA-based linear regression models provided highly accurate MET estimation for household and locomotive activities . Results were similar when equations were developed by non-linear regression or sex-specific linear or non-linear regressions . Sedentary activities were also accurately estimated by the specific linear regression classified from other activity counts . Therefore , the use of a triaxial accelerometer in combination with a GRPACA permits more accurate and immediate estimation of daily physical activity intensities , compared with previously reported cut-off classification models . This method may be useful for field investigations as well as for self-monitoring by general users
For total EE , correlation coefficients were statistically significantly lower in uniaxial compared to multisensor devices .
For active EE , correlations were slightly but not significantly lower in uniaxial compared to triaxial and multisensor devices .
The high level of heterogeneity in the validation studies is only partly explained by the type of activity monitor and the activity monitor outcome .
Triaxial and multisensor devices tend to be more valid monitors .
The assessment of physical activity in healthy population s and in those with chronic diseases is challenging .
The aim of this systematic review was to identify whether available activity monitors ( AM ) have been appropriately vali date d for use in assessing physical activity in these groups .