T = readtable(fname,'Sheet','Segment Position');
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
h1 = scatter3(T, ["RightUpperArmX","RightForearmX","RightHandX"] ...
, ["RightUpperArmY","RightForearmY","RightHandY"] ...
, ["RightUpperArmZ","RightForearmZ","RightHandZ"]);
xlabel("x",'FontSize',12,"FontWeight","bold",'Color','r')
ylabel("y",'FontSize',12,"FontWeight","bold",'Color','b')
zlabel("z",'FontSize',12,"FontWeight","bold",'Color','g')
legend("UpperArm","ForeArm","Hand")
myLength = size(h1(1).XData,2);
myMarker = {"o",">","<"};
[h1.Marker] = myMarker{:};
mySize = [200,repmat(50,1,myLength-1)];
[h1.SizeData] = deal(mySize);
myRed = cat(1,[0,0,0],repmat([1,0,0],myLength-1,1));
myBlue = cat(1,[0,0,0],repmat([0,0,1],myLength-1,1));
myGreen = cat(1,[0,0,0],repmat([0,1,0],myLength-1,1));
myColor = {myRed,myBlue,myGreen};