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 .
Total free living energy expenditure in patients with severe chronic obstructive pulmonary disease.
Resting  energy expenditure ( REE )  is often elevated in patients with chronic obstructive pulmonary disease ( COPD ) , but no data are available regarding total energy expenditure in free living conditions . We compared total daily energy expenditure ( TDE ) in eight COPD patients ( FEV1 36 + /- 13 % ) admitted to a pulmonary rehabilitation center and eight independently living healthy subjects , matched for sex , age , and body mass index ( BMI ) .  TDE was measured over a 2-wk interval using doubly labeled water in combination with measurement of REE and body composition .  The COPD patients had a significantly higher TDE than the healthy subjects ( 2,499 + /- 320 kcal/d and 2,107 + /- 88 kcal/d , respectively , p < 0.01 ) . The nonresting component of TDE ( TDE-REE : physical activity and diet-induced thermogenesis [ DIT ] ) was significantly higher in the COPD patients than in the healthy subjects , result ing in a ratio between TDE and REE of 1.7 + /- 0.2 and 1.4 + /- 0.1 , respectively ( p < 0.01 ) . The results indicate that COPD patients exhibit an increased TDE in comparison with healthy subjects . The difference could by attributed to an increase in the nonresting component of TDE , since REE was comparable between the groups
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 .