diff --git a/src/core/Common.js b/src/core/Common.js
index e7aac42..0738e86 100644
--- a/src/core/Common.js
+++ b/src/core/Common.js
@@ -323,7 +323,8 @@ module.exports = Common;
      * - 2 = Info
      * - 3 = Warn
      * - 4 = Error
-     * @property Common.logLevel
+     * @static
+     * @property logLevel
      * @type {Number}
      * @default 1
      */
diff --git a/src/core/Engine.js b/src/core/Engine.js
index 20176a2..4b8e600 100644
--- a/src/core/Engine.js
+++ b/src/core/Engine.js
@@ -107,13 +107,12 @@ var Body = require('../body/Body');
         var allBodies = Composite.allBodies(world),
             allConstraints = Composite.allConstraints(world);
 
-        // update the detector bodies if they have changed
+        // if the world has changed
         if (world.isModified) {
+            // update the detector bodies
             Detector.setBodies(detector, allBodies);
-        }
 
             // reset all composite modified flags
-        if (world.isModified) {
             Composite.setModified(world, false, false, true);
         }
 
@@ -232,7 +231,9 @@ var Body = require('../body/Body');
      * @param {body[]} bodies
      */
     Engine._bodiesClearForces = function(bodies) {
-        for (var i = 0; i < bodies.length; i++) {
+        var bodiesLength = bodies.length;
+
+        for (var i = 0; i < bodiesLength; i++) {
             var body = bodies[i];
 
             // reset force buffers
@@ -243,20 +244,21 @@ var Body = require('../body/Body');
     };
 
     /**
-     * Applys a mass dependant force to all given bodies.
+     * Applies a mass dependant force to all given bodies.
      * @method _bodiesApplyGravity
      * @private
      * @param {body[]} bodies
      * @param {vector} gravity
      */
     Engine._bodiesApplyGravity = function(bodies, gravity) {
-        var gravityScale = typeof gravity.scale !== 'undefined' ? gravity.scale : 0.001;
+        var gravityScale = typeof gravity.scale !== 'undefined' ? gravity.scale : 0.001,
+            bodiesLength = bodies.length;
 
         if ((gravity.x === 0 && gravity.y === 0) || gravityScale === 0) {
             return;
         }
         
-        for (var i = 0; i < bodies.length; i++) {
+        for (var i = 0; i < bodiesLength; i++) {
             var body = bodies[i];
 
             if (body.isStatic || body.isSleeping)
@@ -269,14 +271,16 @@ var Body = require('../body/Body');
     };
 
     /**
-     * Applys `Body.update` to all given `bodies`.
+     * Applies `Body.update` to all given `bodies`.
      * @method _bodiesUpdate
      * @private
      * @param {body[]} bodies
      * @param {number} delta The amount of time elapsed between updates
      */
     Engine._bodiesUpdate = function(bodies, delta) {
-        for (var i = 0; i < bodies.length; i++) {
+        var bodiesLength = bodies.length;
+
+        for (var i = 0; i < bodiesLength; i++) {
             var body = bodies[i];
 
             if (body.isStatic || body.isSleeping)
diff --git a/src/core/Sleeping.js b/src/core/Sleeping.js
index ad22242..e431c57 100644
--- a/src/core/Sleeping.js
+++ b/src/core/Sleeping.js
@@ -25,8 +25,7 @@ var Common = require('./Common');
      */
     Sleeping.update = function(bodies, delta) {
         var timeScale = delta / Common._timeUnit,
-            timeScaleSquared = timeScale * timeScale,
-            motionSleepThreshold = Sleeping._motionSleepThreshold * timeScaleSquared;
+            motionSleepThreshold = Sleeping._motionSleepThreshold * timeScale * timeScale;
         
         // update bodies sleeping status
         for (var i = 0; i < bodies.length; i++) {