Transcription
Hello everyone. You are watching Physical Classroom channel. And in today's video, I am going to share with you all a very simple and effective way of learning the human gait biomechanics. After watching this video, the physiotherapy students will find it very easy to understand the human gait kinetics and kinematics.
Now, we all must have gone through the different tables in our biomechanics book which describes the kinetics and kinematics of various phases of gait cycle. A student often finds it difficult to learn all the tables of the gait cycle just because he or she doesn't know the concept behind the kinetic analysis. So, let's start today's video by first understanding how to determine the type of muscle work that is required for producing a movement.
So, the first step in learning biomechanics is always to analyze the motion or do motion analysis. Motion analysis is also referred to as the kinematics. So, let's take a simple example. Suppose I want to lift my hand like this into forward elevation. So, I have to observe the movement that has taken place. So, in the starting position, my hand was neutral and it was beside the body. When I performed this movement, I have brought my shoulder into 90 degrees of flexion. So, my motion analysis tells me that the shoulder has moved into 90 degrees of flexion.
The second step in learning the biomechanics is to identify the direction of motion or movement with respect to the gravity. Now, there are three options that can happen. First is that the movement is taking place against the direction of the gravitational pull. The second option could be that the movement is taking place towards the direction of the gravitational pull. And the third option could be that the joint has stabilized itself at a particular location and no movement is taking place, so that that gravitational pull has been counteracted.
Now, depending on these three situations, we have to do our kinetic analysis. So, let's understand this. Now, in kinetic analysis, we have to always remember that whenever the movement is produced against the gravitational pull, then it has to be brought about by the concentric contraction of the agonist group of muscles. Now, this means that if we have to work against gravity, then the direction in which we are going to move, the same direction muscles are going to produce that movement by concentric contraction. Like in this case, I was doing shoulder flexion. So, this has to be brought about by the concentric contraction of the anterior fibers of the deltoid.
Now, let's take up the second situation for kinetic analysis. Now, if I have to bring my hand down from this position. So, now again, I have to first analyze the motion. So, the motion now is extension from 90 degree flexion to neutral. So, I have moved my shoulder into 90 degrees of extension. Now, I have to identify the direction of the movement with respect to the gravitational pull. Was my movement against gravity or was my moment towards gravity? So, when I was lowering my shoulder like this, my movement was taking place towards the gravity.
So, the second important point to be noted for doing kinetic analysis is that whenever the movement is taking place towards the gravity, then it need not to be produced but controlled. So, what I mean to say is, if I am moving my joint against the gravity, I need to produce this motion. But if I am lowering my joint and moving it towards the gravity, then I need to control the motion. So, now the muscle work, concentric and eccentric, both have different purposes. Concentric work is done to produce the motion, that means the joint is going to move against gravity. And eccentric work is done to control the motion, that is when we have to lower our joint or a body part towards the gravity in a controlled manner.
So, as in this case, if we look to the motion, the motion I described was the 90 degrees of extension that took place in the direction of the gravity. So, lot of time students say because the motion is extension, so it is the posterior fibers that needs to contract. But this is wrong. Why? Because I don't want to produce the motion towards the gravity, I want to control it so that my hand comes down slowly. So, how can I control it by doing the eccentric contraction from the anterior fibers of the deltoid? So, the second important point for kinetic analysis to be noted is that whenever the movement takes place towards the gravity, then always the antagonist muscles contract eccentrically.
So, let me summarize again. Whenever the movement takes place against gravity, it needs to be produced by the concentric contraction of the agonist. And whenever the movement has to take place towards the gravity, it needs to be controlled, not produced, by the eccentric contraction of the antagonist. So, the motion in this case was extension. So, the antagonist muscles are the flexors of the shoulder. So, they have to control this motion of shoulder extension by contracting eccentrically.
Now, in the third situation, whenever the joint is being held stationary against the pull of the gravity, then it has to be produced by the isometric contraction of the agonist group of muscles. So, if I am holding my shoulder in ninety degree flexion, this has to be produced by isometric work from my anterior fibers of the deltoid. So, they are working in an isometric manner, not allowing any movement towards the direction of the gravity.
So, now let's apply this knowledge to learn gait biomechanics by taking few examples from different phases of the gait cycle. All we will be doing is answering two important questions. That is, where to first identify the moment that is taking place in a joint. And then we are going to relate the movement with respect to the gravitational pull. If the movement is taking place against gravity, then we know it has to be brought about by the concentric contraction of the agonist. And if the movement is taking place towards the gravity, then we know it has to be brought about by the eccentric contraction of the antagonist. And if no movement is taking place in a joint and it is stabilized, then it will be brought by the isometric contraction of the agonist.
So, let's take up the first example from the heel strike to foot flat phase. And let's try to determine the muscle work at the ankle joint during this phase of the gait cycle. So, at heel strike, the ankle joint is neutral. There is neither dorsiflexion nor plantar flexion. And at foot flat, the ankle joint or the foot goes down and touches the ground. So, that 15 degrees of plantar flexion takes place in the ankle joint. So, the first thing that we have determined is that plantar flexion movement has taken place in the ankle joint. So, I am going to write here plantar flexion.
Now, the second thing that I have to determine is the relation of this movement with respect to the gravitational pull. So, the plantar flexion movement has taken place towards the direction of the gravity. That means this movement need not to be produced but controlled by the muscles. And therefore, we can conclude that to control the plantar flexion movement taking place towards the gravity, I would require the eccentric work from the antagonist group of muscles, which are the dorsi flexors. So, I hope the students are now understanding how to perform the kinetic analysis. So, for this plantar flexion moment at the ankle, this movement was taking place towards the gravity. And so, I know that the antagonist needs to contract eccentrically. Therefore, I will write here that the dorsi flexors muscles will work eccentrically to produce this particular motion.
So, now let's take another example from the foot flat to mid stance phase. And this time, we are going to do the analysis for the knee joint. So, at foot flat, the knee joint is 15 degree flexed. And at mid stance, it achieves 5 degree of flexion. So, the net movement that has taken place is 10 degrees of extension. So, the movement that is taking place at knee joint is extension. Now, we have to determine whether this movement needs to be produced or controlled. So, we can again easily conclude that the knee movement of extension is taking place against the gravity. So, that means this movement needs to be produced by the agonist contraction of the concentric group of muscles. So, I have to write here that the quadriceps muscle is going to contract concentrically during this phase to produce this motion.
So, by utilizing this concept and answering two important questions regarding the joint movement that has taken place during a particular phase of gait cycle and the relation of that movement with respect to gravity, the physiotherapy student will be very easily able to determine and perform the kinetic analysis of all the phases. Do try and utilize this concept and again go through all the tables of these sagittal plane analysis and even the frontal plane analysis for the gait cycle. And you are going to find it very easy now to conclude and give reasoning for the different types of muscle work occurring during the different phases of gait cycle. Concentric for producing the motion, eccentric for controlling the motion, and isometric for stabilizing the motion.
So, I sincerely hope that the information shared by me in this video is going to be helpful for you all. Do not forget to share Physical Resume videos with your friends, colleagues, seniors, and juniors. Do keep motivating us with your comments and feedback. See you all in our next video. Till then, keep learning, keep sharing, and stay connected.