Validity Of Three Axis Accelerometer(Hip And Wrist) In Physical Activity Monitoring

Objective:Using the measured value of K4b2 energy consumption as the standard,the effectiveness of the three axis accelerometer on the energy consumption of different parts of GT3X+ was discussed in order to find out the most suitable site for monitoring the physical activity of GT3X+.Methods:Through voluntary registration,20 adults aged 22.30 + 2.48 were selected as research subjects,including 14 boys and 6 girls.It was required to wear a portable gas metabolism analyzer(Cosmed K4b2),and a three axis accelerometer(Actigraph GT3X+)at the right hip and right wrist.Each participant was slow walking(3km/h),easy walking(4km/h),normal walking(5km/h),fast walking(6km/h),jogging(7km/h)and positive.Physical activities such as uphill walking(10% slope,5km/h),5min of each physical activity type,and at least 5min intervals between two adjacent activities.The software Actilife(V6.12.0)equipped with GT3X+ and the software K4b2(b9.1)equipped with the gas metabolic analyzer(b9.1)are used to collect the data of physical activity,and use the metabolic equivalent in K4b2 to divide the strength of each person’s physical activity when running,and the data is arranged and analyzed by Excel 2013 and SPSS 20.Results:(1)The basic parameters of the three axis accelerometer are compared with the strength of different physical activity: high strength > middle and high strength >middle strength;under the same physical activity intensity,the basic parameters of different parts are compared.There is no significant difference in the vertical axis activity count(P>0.05),except for the high strength physical activity(GT3X+).Significant difference(P<0.05).(2)When the three axis accelerometer GT3X+ is worn on the hip or wrist,the activity count of the vertical axis and the count of the integrated vector activity count with the K4b2 energy metabolism index oxygen uptake(ml/min),the relative oxygen uptake(ml/min/kg),the metabolite equivalent,and the energy consumption(Kcal/min)in the middle intensity physical activity and the medium and high strength physical activity.It is highly sexual and highly correlated(r 0.4).(3)The correlation coefficient between the energy consumption prediction value of the three axis accelerometer GT3X+ and the measured value of K4b2 energy consumption at the hip is 0.691,0.551 and 0.751 respectively when the strength,high strength and medium strength physical activity in the middle strength,and the correlation coefficient between the energy consumption prediction value and the measured value of K4b2 energy consumption when the GT3X+ is worn on the wrist is in the middle strength,high strength and middle height The intensity of physical activity was 0.664,0.421 and 0.662 respectively.(4)The results of the three axis accelerometer GT3X+ energy consumption prediction value and the measured value Bland-Altman scatter plot show that when the GT3X+is worn on the hip,the mean value of the difference between the predicted and the measured values is 1.78,2.69 and 2.15 respectively in the middle strength,high strength and medium strength physical activity,and the standard deviation of the difference values are 1.33,5.67 and 1.47 respectively.The 95% confidence interval ranges from(-3.83 to 4.39)and(-0.29 to 5.17)respectively.(-0.73 to 5.03),when GT3X+ was worn at the wrist,the mean values of the difference values between the predicted and the measured values were-0.19,-1.67 and-0.78 respectively,and the difference values were 2.72,4.89 and 3.80 respectively,and the 95% confidence interval ranges were(-5.52,5.14),(-11.25,7.91),respectively.-8.22,6.13).Conclusion:(1)Whether the three axis accelerometer GT3X+ is worn on the hip or wrist,the vertical axis activity count(Axis1)and the integrated vector activity count(VM)have good correlation with the K4b2 energy metabolism index(Mei Tuo,oxygen uptake,relative oxygen uptake and energy consumption),and can be used as the independent variable of the energy metabolism of the pre measured physical activity.(2)When the energy consumption of the three axis accelerometer GT3X+ is worn on the hip,the measured value of energy consumption should be underestimated.The energy consumption forecast value when wearing the wrist will overestimate the measured value of energy consumption.(3)The three axis accelerometer GT3X+ is recommended for wearing in the hip when monitoring strength and high and medium intensity physical activity.