Page 48 - Sember, Vedrana, and Shawnda A. Morrison. 2018. The Mind-Body Connection. Koper: University of Primorska Press.
P. 48
Physical Activity Research
produces voltage as a function of geometric deformation (Chen &
Bassett, 2005). Accelerations are then transferred to a lower resolu-
tion called epoch. Epoch is calibrated to a known criterion measure
(e.g., oxygen consumption, doubly-labelled water). Most of existing
calibration studies are then presented in unitless intensity metric
called ‘counts’ (Freedson et al., 2012). When we have physical activ-
ity in counts, we can modify this unitless intensity to different levels
of physical activity and energy expenditure. Acceleration is change
in velocity over given period of time; therefore, intensity, frequency
and duration of measured physical activity can be assessed (Ridgers
& Fairclough, 2011). Compared to measures of oxygen consumption
and METs most of accelerometer show a wide range of correlations
(r = 0.45 to 0.93) (Trost, McLever, & Pate, 2005), which corresponds
to a number of protocol-related variations such as accelerometer
placement (hip, wrist, wrinkle, trunk) and investigation activities
(ambulatory, non-ambulatory).
There are uni-, bi-, and triaxial accelerometers. Uniaxial accelero-
meter measure accelerations in one direction, biaxial in vertical and
horizontal directin and triaxial in three directions: anteroposterior,
mediolateral and vertical direction. Triaxial accelerometers provide
more information and show the best relationship to activity-related
energy expenditure (Bouten, Westerterp, Verduin, & Janssen, 1994).
In physical activity research the most commonly used acceleromet-
er is uniaxial. Researchers found comparable results between uni-
axial, biaxial and triaxial accelerometers, because physical activity
research prevails in vertical acceleration and this type of accelero-
meter is cheaper and easier for data processing (Kumahara, Tanaka,
& Schutz, 2004).
Accelerometers can be placed on different body parts: ankle,
thigh, chest, wrist, upper or lower back, hips or belly button. In
terms of reliability and validity of the data, literature encourages
wearing accelerometer on the hips or in the lower back because of
the proximity of the center of gravity of the body (Ekelund et al.,
2000).
Accelerometer collects and stores data in intervals called epochs,
which is usually possible to adjust on 5, 15, 30, 45 and 60s or cus-
46
produces voltage as a function of geometric deformation (Chen &
Bassett, 2005). Accelerations are then transferred to a lower resolu-
tion called epoch. Epoch is calibrated to a known criterion measure
(e.g., oxygen consumption, doubly-labelled water). Most of existing
calibration studies are then presented in unitless intensity metric
called ‘counts’ (Freedson et al., 2012). When we have physical activ-
ity in counts, we can modify this unitless intensity to different levels
of physical activity and energy expenditure. Acceleration is change
in velocity over given period of time; therefore, intensity, frequency
and duration of measured physical activity can be assessed (Ridgers
& Fairclough, 2011). Compared to measures of oxygen consumption
and METs most of accelerometer show a wide range of correlations
(r = 0.45 to 0.93) (Trost, McLever, & Pate, 2005), which corresponds
to a number of protocol-related variations such as accelerometer
placement (hip, wrist, wrinkle, trunk) and investigation activities
(ambulatory, non-ambulatory).
There are uni-, bi-, and triaxial accelerometers. Uniaxial accelero-
meter measure accelerations in one direction, biaxial in vertical and
horizontal directin and triaxial in three directions: anteroposterior,
mediolateral and vertical direction. Triaxial accelerometers provide
more information and show the best relationship to activity-related
energy expenditure (Bouten, Westerterp, Verduin, & Janssen, 1994).
In physical activity research the most commonly used acceleromet-
er is uniaxial. Researchers found comparable results between uni-
axial, biaxial and triaxial accelerometers, because physical activity
research prevails in vertical acceleration and this type of accelero-
meter is cheaper and easier for data processing (Kumahara, Tanaka,
& Schutz, 2004).
Accelerometers can be placed on different body parts: ankle,
thigh, chest, wrist, upper or lower back, hips or belly button. In
terms of reliability and validity of the data, literature encourages
wearing accelerometer on the hips or in the lower back because of
the proximity of the center of gravity of the body (Ekelund et al.,
2000).
Accelerometer collects and stores data in intervals called epochs,
which is usually possible to adjust on 5, 15, 30, 45 and 60s or cus-
46
