diff --git a/sources/reactphysics3d/body/BodyState.cpp b/sources/reactphysics3d/body/BodyState.cpp
index 143675ec..e251acee 100644
--- a/sources/reactphysics3d/body/BodyState.cpp
+++ b/sources/reactphysics3d/body/BodyState.cpp
@@ -38,7 +38,7 @@ BodyState::BodyState(const BodyState& bodyState)
           : position(bodyState.position), linearMomentum(bodyState.linearMomentum), orientation(bodyState.orientation),
             angularMomentum(bodyState.angularMomentum), linearVelocity(bodyState.linearVelocity),
             angularVelocity(bodyState.angularVelocity), spin(bodyState.spin), inertiaTensorInverse(bodyState.inertiaTensorInverse),
-            massInverse(bodyState.massInverse), force(bodyState.force) {
+            massInverse(bodyState.massInverse), externalForce(bodyState.externalForce) {
 }
 
 // Destructor
@@ -90,7 +90,7 @@ void BodyState::computeAtTime(const Time& timeStep, const DerivativeBodyState& l
 // time (like Runge-Kutta 4 integrator)
 Vector3D BodyState::computeForce(Time time) const {
     // TODO : Implement this method (we want that the user of the library could define this method)
-    return force;
+    return externalForce;
 }
 
 // Return the torque on the body at time
@@ -98,5 +98,5 @@ Vector3D BodyState::computeForce(Time time) const {
 // time (like Runge-Kutta 4 integrator)
 Vector3D BodyState::computeTorque(Time time) const {
     // TODO : Implement this method (we want that the user of the library could define this method)
-    return torque;
+    return externalTorque;
 }
diff --git a/sources/reactphysics3d/body/BodyState.h b/sources/reactphysics3d/body/BodyState.h
index 1efdab3e..acda2d6f 100644
--- a/sources/reactphysics3d/body/BodyState.h
+++ b/sources/reactphysics3d/body/BodyState.h
@@ -40,8 +40,8 @@ class BodyState {
         Vector3D linearMomentum;                // Linear momentum of the body
         Quaternion orientation;                 // Orientation quaternion of the body
         Vector3D angularMomentum;               // Angular momentum of the body
-        Vector3D force;                         // Current force on the body
-        Vector3D torque;                        // Current torque on the body
+        Vector3D externalForce;                 // Current external force on the body
+        Vector3D externalTorque;                // Current external torque on the body
 
         // Secondary values
         Vector3D linearVelocity;                // Linear velocity of the body
@@ -70,11 +70,12 @@ class BodyState {
         Vector3D getAngularVelocity() const;                                    // Return the angular velocity
         Quaternion getSpin() const;                                             // Return the spin of the body
         void setMassInverse(Kilogram massInverse);                              // Set the inverse of the mass
+        Matrix3x3 getInertiaTensorInverse() const;                              // Get the inverse of the inertia tensor
         void setInertiaTensorInverse(const Matrix3x3& inertiaTensorInverse);    // Set the inverse of the inertia tensor
-        Vector3D getForce() const;                                              // Return the current force of the body
-        void setForce(const Vector3D& force);                                   // Set the current force on the body
-        Vector3D getTorque() const;                                             // Return the current torque of the body
-        void setTorque(const Vector3D& torque);                                 // Set the current torque of the body
+        Vector3D getExternalForce() const;                                      // Return the current external force of the body
+        void setExternalForce(const Vector3D& force);                           // Set the current external force on the body
+        Vector3D getExternalTorque() const;                                     // Return the current external torque of the body
+        void setExternalTorque(const Vector3D& torque);                         // Set the current external torque of the body
         Kilogram getMassInverse() const;                                        // TODO : Delete this
         void recalculate();                                                                 // Recalculate the secondary values
                                                                                             // of the BodyState from the primary ones
@@ -150,29 +151,34 @@ inline void BodyState::setMassInverse(Kilogram massInverse) {
     this->massInverse = massInverse;
 }
 
+// Get the inverse of the inertia tensor
+Matrix3x3 BodyState::getInertiaTensorInverse() const {
+    return inertiaTensorInverse;
+}
+
 // Set the inverse of the inertia tensor
 inline void BodyState::setInertiaTensorInverse(const Matrix3x3& inertiaTensorInverse) {
     this->inertiaTensorInverse = inertiaTensorInverse;
 }
 
-// Return the force over the body
-inline Vector3D BodyState::getForce() const {
-    return force;
+// Return the external force on the body
+inline Vector3D BodyState::getExternalForce() const {
+    return externalForce;
 }
 
-// Set the force over the body
-inline void BodyState::setForce(const Vector3D& force) {
-    this->force = force;
+// Set the external force on the body
+inline void BodyState::setExternalForce(const Vector3D& force) {
+    this->externalForce = force;
 }
 
-// Return the current torque of the body
-inline Vector3D BodyState::getTorque() const {
-    return torque;
+// Return the current external torque on the body
+inline Vector3D BodyState::getExternalTorque() const {
+    return externalTorque;
 }
 
- // Set the current torque of the body
-inline void BodyState::setTorque(const Vector3D& torque) {
-    this->torque = torque;
+ // Set the current external torque on the body
+inline void BodyState::setExternalTorque(const Vector3D& torque) {
+    this->externalTorque = torque;
 }
 
 
diff --git a/sources/reactphysics3d/body/RigidBody.h b/sources/reactphysics3d/body/RigidBody.h
index 0e8493a5..f435ee22 100644
--- a/sources/reactphysics3d/body/RigidBody.h
+++ b/sources/reactphysics3d/body/RigidBody.h
@@ -31,6 +31,9 @@
 // Namespace reactphysics3d
 namespace reactphysics3d {
 
+// TODO : Check if it is possible to put all the attributes from BodyState class in the RigidBody class (to do this, the
+//        class RungeKutta have to be changed a lot
+
 /*  -------------------------------------------------------------------
     Class RigidBody :
         This class represents a rigid body of the physics