Table 3.

Guideline table to determine the needed number and placement of the wearable accelerometer for each task.

Task	Most accurate combination	Most accurate single placement	Most efficient combinationa
Sedentary activity detection (balanced accuracy)	All 5 placements (0.78)	Hip (0.73)	Hip (0.73)
Locomotion activity detection (balanced accuracy)	All 5 placements (0.98)	Hip (0.98); ankle (0.98)	Hip (0.98)
Lifestyle activity detection (balanced accuracy)	Ankle+upper arm+hip+wrist (0.92)	Upper arm (0.87); wrist (0.87); hip (0.87)	Wrist (0.87)
Individual activity recognition (accuracy)	All 5 placements (0.57)	Wrist (0.42)	Hip+wrist (0.51)
MET value estimation (root mean square error)	Ankle+upper arm+hip+thighb (0.87)	Hip (0.91); thigh (0.91)	Hip+wrist (0.89)

^aThe most efficient combination was defined as the fewest number of sensors that provide a similar performance to the most accurate combination while considering usability. Similar performance was defined as a difference ≤10% of the most accurate combination. We considered the most-to-least usable placements to be wrist>hip>ankle>arm>thigh. Thus, if the performance difference was less than 10%, then the most usable placement was chosen as the most efficient. Best and worst performance refer to best and worst performance according to their balanced accuracy (best: highest balanced accuracy; worst: lowest balanced accuracy).

^bThe performance of the combination with the best performance (0.87) was very close to that of the combination with all 5 placements (0.88).