diff --git a/ShoulderCase/@Muscle/measureAndSaveCentroid.m b/ShoulderCase/@Muscle/measureAndSaveCentroid.m
index eef08fa..d04222c 100644
--- a/ShoulderCase/@Muscle/measureAndSaveCentroid.m
+++ b/ShoulderCase/@Muscle/measureAndSaveCentroid.m
@@ -1,8 +1,11 @@
 function measureAndSaveCentroid(obj)
   muscleContour = obj.loadMask("Contour");
-  centroidIndices = round(regionprops(muscleContour).Centroid);
   muscleCentroid = false(size(muscleContour));
-  muscleCentroid(centroidIndices(1), centroidIndices(2)) = true;
+  centroidIndices = round(regionprops(muscleContour).Centroid);
+  % centroidIndices(2) is the vertical top->down index
+  % centroidIndices(1) is the horizontal left->right index
+  % kind of opposite to the matlab array indexing...
+  muscleCentroid(centroidIndices(2), centroidIndices(1)) = true;
   obj.saveMask(muscleCentroid, "Centroid");
   obj.centroid = obj.getMaskCoordinates("Centroid");
 end
\ No newline at end of file