So I put . after so each elements of the list are squared instead of matrix multiplications. Also using plot() after the changes made it work .
rad=pi/180; %To convert degress into radiant
deg=180/pi; %To convert radiant into degrees
C1=0.088*H+0.03;
C2=0.036*H+0.04;
C3=0.02*H;
C4=0.153*H;
teta1=360-118-90-atan(C1/C4)*deg-atan(C2/C3)*deg;
teta2=360-80-90-atan(C1/C4)*deg-atan(C2/C3)*deg;
PO=sqrt(C1.^2+C4.^2);
AO=sqrt(C2.^2+C3.^2);
L1=sqrt(PO.^2+AO.^2-2*PO.*AO.*cos(teta1*rad));
L2=sqrt(PO.^2+AO.^2-2*PO.*AO.*cos(teta2*rad));
SpringDisplacement=L2-L1;
H=1:0.01:1.9; %Min height of person is 1m, maximum height is 1.9m
plot(SpringDisplacement,H)
The values from the plot seem to correspond with what I am looking for so I am assuming it is right