diff --git a/src/adam/model/tree.py b/src/adam/model/tree.py
index e8447871..0b72dd4e 100644
--- a/src/adam/model/tree.py
+++ b/src/adam/model/tree.py
@@ -1,4 +1,6 @@
 import dataclasses
+import logging
+
 from typing import Dict, Iterable, List, Tuple, Union
 
 from adam.model.abc_factories import Joint, Link
@@ -89,32 +91,65 @@ def reduce(self, considered_joint_names: List[str]) -> "Tree":
                 if joint.name not in considered_joint_names
             }
         )
-        # TODO: neck_2, l_wrist_1, r_wrist_1 don't get lumped
-        while nodes_to_lump != []:
-            node = self.graph[nodes_to_lump.pop()]
-            parent_node = self.graph[node.parent.name]
-
-            # lump the inertial properties
-            parent_node.link = node.parent.lump(  # r_hip_1
-                other=node.link,  # r_hip_2
-                relative_transform=node.parent_arc.spatial_transform(0),
-            )
-
-            # update the parent
-            node.parent = parent_node.link
 
-            # update the children
-            if node.name in parent_node.children:
-                parent_node.children.remove(node.name)
-                parent_node.children.append(node.children)
-
-            # update the arcs
-            if node.parent_arc.name not in considered_joint_names:
-                parent_node.arcs.remove(node.parent_arc)
-                parent_node.arcs.append(node.arcs)
+        relative_transform = (
+            lambda node: node.link.math.inv(
+                self.graph[node.parent.name].parent_arc.spatial_transform(0)
+            )
+            @ node.parent_arc.spatial_transform(0)
+            if node.parent.name != self.root
+            else node.parent_arc.spatial_transform(0)
+        )
 
-            # remove the node
-            self.graph.pop(node.name)
+        last = []
+        leaves = [node for node in self.graph.values() if node.children == last]
+
+        while all(leaf.name != self.root for leaf in leaves):
+            for leaf in leaves:
+                if leaf is self.graph[self.root]:
+                    continue
+
+                if leaf.parent_arc.name not in considered_joint_names:
+                    # create the new node
+                    new_node = Node(
+                        name=leaf.parent.name,
+                        link=None,
+                        arcs=[],
+                        children=None,
+                        parent=None,
+                        parent_arc=None,
+                    )
+
+                    # update the link
+                    new_node.link = leaf.parent.lump(
+                        other=leaf.link,
+                        relative_transform=relative_transform(leaf),
+                    )
+
+                    # update the parents
+                    new_node.parent = self.graph[leaf.parent.name].parent
+                    new_node.parent_arc = self.graph[new_node.name].parent_arc
+                    new_node.parent_arc.parent = (
+                        leaf.children[0].parent_arc.name if leaf.children != [] else []
+                    )
+
+                    # update the children
+                    new_node.children = leaf.children
+
+                    # update the arcs
+                    if leaf.arcs != []:
+                        for arc in leaf.arcs:
+                            if arc.name in considered_joint_names:
+                                new_node.arcs.append(arc)
+
+                    logging.debug(f"Removing {leaf.name}")
+                    self.graph.pop(leaf.name)
+                    self.graph[new_node.name] = new_node
+            leaves = [
+                self.get_node_from_name((leaf.parent.name))
+                for leaf in leaves
+                if leaf.name != self.root
+            ]
 
         return Tree(self.graph, self.root)