hello and welcome to p.e buddy mr d here welcome to part four of our biomechanics for beginners series in the previous video we went through kinematic concepts now we're going to move on to levers so today you'll learn about first second and third class levers and how they relate to the body biomechanics sport and performance let's learn something [Music] [Applause] [Music] okay so levers are a system made up of a bar and a fulcrum okay within biomechanics and relating to the body the bars of the bones the fulcrum are the joints and the force comes from muscle contractions so let's start with first class levers we're going to use this diagram here so the blue triangle represents the fulcrum or the axis this is where the bar rotates or pivots around okay so for a first class lever you've got one side the force or the effort coming down all right that could be a push or a pull and on the other side of the bar you've got the resistance this could be the weight or the load that you're trying to move okay so within the body it might look something like this so you've got the skull here okay which is the resistance or the load or the thing that we need to move okay in the middle here represented by f is the fulcrum okay or the axis that's where it pivots around that's where the skull meets the spine then the muscle here represents the force and the muscle contracts causes movement pivoting around the point here and it causes the head to tilt backwards so this is an example of a first class lever within the body another more visual example could be a seesaw like this so as you can see when this guy comes down that is the force or the effort all right we're pivoting around our axis or fulcrum here and the weight of the other guy is the resistance when the force comes down the load goes up let's move on to second class levers this time you'll notice the fulcrum is right over to one side okay we've got our force right on the opposite side pushing or pulling up okay and the resistance is in the middle of the bar pulling or pushing down so within the body you can visualize it here we have the fulcrum down on the toes here that's where we're going to pivot from we have the resistance or the weight in the middle of the foot pushing down and then we have the force going up here so when the calf contracts the resistance will be pulled up pivoting around the fulcrum in real life an example of this is the wheelbarrow okay so the pivot point is the wheel all right the force is the guy pushing it up like that and the resistance is the weight of whatever's in the wheelbarrow pushing down finally we have our third class levers again the full criminal axis is to one side of the bar all right but this time the resistance and force are different so the force is pushed or pulled up from the center or near to the fulcrum or the axis and the resistance is right over on the other end pulling or pushing down an example of the body we can see the fulcrum here which is the elbow joint okay we can see the resistance or the weight which is the arm and forearm pulling or pushing down and we've got the force which is the bicep so as you can visualize when the bicep contracts okay pivots around the fulcrum and the arm extends up a real life example of this is fishing so you can imagine that the fulcrum is where the hands meet the fishing rod okay the resistance is at the end the fish pulling down and the force this guy needs to contract his biceps and pull up to make sure the fish doesn't pull him into the ocean you just learnt about the three types of levers first second and third class thanks very much for watching this video i hope you enjoyed it and learnt something if you did give it a like if you still have questions put them in the comment box and make sure you subscribe for our final part of this five part series launching soon this will be on equilibrium thanks guys [Music]