Estimation of GM-MTU length change from Knee/Ankle JA

Using equation from Grieve et al., 1978 Percent length change (strech and shorten) of gastrocnimius medialis muscle tendon unit is estimated

%%Equation from Grieve et al.,1978: Prediction of gastrocnemius length from knee and ankle joint posture

%%Definition of angle

%%Ankle joint: Neutral position as 90 degree

%%Knee joint: Neutral (Fully extended) position as 0 degree

%%Data import

JA_Ankle = imread(data1) %Here for ankle joint angle data

JA_Knee = imread(data2) %Here for knee joint angle data

Lower_leg_length = 38.0 %Here for participant's lower leg length data

%%Estimation of percent length change

L_Ankle = -22.18468 + 0.30141*(JA_Ankle) + -0.00061*(JA_Ankle).^2;

L_Knee = 6.46251 + -0.07987*(JA_Knee) + 0.00011*(JA_Knee).^2;

%%This is the relative change of gastrocnemius medialis

MG-MTU_Percent_Change = L_Ankle + L_Knee;

plot(MG-MTU_Length_Change,'k')

xlabel('Time')

ylabel('%Segment length')

%%By multiplying with lower leg length data, you can get estimated length change data

MG-MTU_Length_Change = (L_Ankle + L_Knee)*Lower_leg_length;

plot(MG-MTU_Length_Change,'k')

xlabel('Time')

ylabel('Segment length change')