Table 2.

Agreement between Acti4 accelerometry-based classifications and video recording of the semi-standardized protocol (n = 20)

Accelerometer		Sit	Stand	Move	Walk	Run	Stairs	Cycle
Actigraph GT3x	Sensitivity (%)(a)	99	75	67	93	92	71	94
	Specificity (%)(b)	97	99	93	95	100	100	98
Axivity AX3	Sensitivity (%)(a)	96	73	63	91	95	78	93
	Specificity (%)(b)	97	98	94	94	100	100	99
ActivPAL Micro4	Sensitivity (%)(a)	99	74	55	93	94	72	94
	Specificity (%)(b)	97	99	93	95	100	100	98

Physical behaviors were recorded at 1 frame-per-second using a handheld video camera. Percentage of specificity and sensitivity provides a measure of the percentage of classification agreement between each accelerometer brand and video observation

^(a) Sensitivity is defined as the proportion of classifications that are correctly classified as the actual physical activity type or posture, in agreement with the criterion measure (video observation)

^(b) Specificity is defined as the proportion of classifications that were correctly identified as NOT belonging to the physical activity type or posture of interest, in agreement with the criterion measure (video observation)