The source of power for human movement in a chain reaction, in all three planes of motion, in upright function.

I’ve just watched an insight into the source of power in the serve, from a provider on YouTube. I was impressed with his subscriber number at 28,000 and the 540 likes he got for his post. His vlog was informative and his movement terminology was good. He compared the arm action in a seated position with a standing one and concluded that up to 90% of the power in a serve was in the arm action alone and he guessed,  “standing only added about another 20%.” Not sure about his Maths! His conclusion was not based on speed measurement and he made no reference to the origin and transmission of energy in the seated position. Rather than continue to critique his post, I want to show you in this vlog, the origins of force and how it is transformed into power for outcomes, moving up the chain in all three planes of motion, to complete a task. It is not my intention to comment on the considerable achievements of wheelchair players, as that is outside the scope of this vlog.

Let’s start with a glossary of terms to aide understanding.

The Physical and Biological Sciences.

  • Kinematics, a branch of physics and a subdivision of classical mechanics concerned with the geometrically possible motion of a body or system of bodies without consideration of the forces involved (i.e., causes and effects of the motions). A chain reaction fits this description. 
  • Kinetics is the study of how forces and torques affect the motion of objects, bodies and systems. The forces that drive the chain reaction.
  • First Law of Thermodynamics  states that energy can neither be created nor destroyed, but it can be transformed from one form to another or transferred between systems. The capture of energy from the physical forces.
  • The biological sciences. Muscles react to the forces of movement. They lengthen to load and contract to explode. Transforming the forces into energy, the capacity for work.
  • Transmission of energy within the system.  The effects of mass and momentum and torque conversion. Distributing energy in a chain reaction.

To begin to understand the forces that act on and within a body in human movement, it’s necessary to picture the movement and try to see it in terms of what we know about how bodies are designed to move.

The clip below shows the full action, with some stills that highlight motion as a chain reaction of integrated segments, that require force/energy  to complete the task, in upright function:

 

A chain reaction is a kinematic description of how integrated segments (muscles bones and joints) in the human body move, which we have covered extensively, but the focus is now on why they move which  is the study of Kinetics.

Kinetics  is the study of the energy a body captures in movement. The amount of kinetic energy captured by a moving object depends on the mass of the object and its momentum (speed) The greater the mass and the speed of the object the greater its kinetic energy.

What you need to know from these sciences.

In the following headings it is not necessary to understand the physical and biological sciences in full , but rather to know how these laws apply to all human movement in upright function. Coaches and coach educators must see them as vital in training and coaching human movement in upright function, for safe performance gain.

The Physical Sources of Forces.

Force/energy for human movement is captured from the initial movement under the force of gravity which when its meets ground reaction force transforms into energy, the capacity for motion, referenced by the first law of thermodynamics,  That law states that energy is the capacity for doing work, that cannot be created or destroyed only transformed. That still leaves the question of how it is  accomplished in human movement in upright function. What is the mechanism?

The Biological Sources of Forces.

We know that gravity forces us down and we now know that we can begin to capture and transform that down force, by the reaction of our muscles and joints, as we meet the ground. It’s the muscles reacting by lengthening to decelerate this down force. They then contract, together with the joints in the foot/ankle complex, capturing that force and accelerating the combination of both forces, as energy for work further  up the chain, in upright function in all three planes of motion.

It’s the lengthening to load and contracting to explode of muscles and joints that capture the energy, the capacity for work,. It’s an elastic recoil motion in the transformational zone, in any purposeful human movement in upright function. Complete loading at a joint is in all three planes of motion and involves flexion, adduction and internal rotation but it can be partial loading, in one or two planes only, as the particular activity dictates.

Again, it’s not necessary that you understand these physical and biological laws, only that they are the processes that transform force into kinetic energy, that drives human movement in all three planes of motion, in upright function.

My Progress as a Coach

I started from what I knew and what was self evident in movement, adding what I had learnt experientially over 30 years in tennis.  I gradually added levels of understanding of function and chain reaction, from both my study and my more informed coaching practice.

As coaches we are called to teach and problem solve to help our players. In my experience players at all levels have a range of barriers to learning, but the most common barrier I find, is a physical inability, to perform the task, no matter the quality of verbal and visual instruction. This is true in almost any situation whether you find yourself working with young athletes or recreational players of any age.

I have found that my study of movement science has added a number of additional tools to my toolbox for the benefit of my players and which also made my work far more enjoyable. See My Testimonials

Human movement is  complex  but a desire to understand what is known by scientific study and what can be applied, is essential for all those involved in the movement Industry. The 3DMAPS process is a distillation of that study from the Gray Institute and makes it simpler to understand the methodology and to incorporate it’s exercise matrices in your coaching toolbox. 3DMAPS provides the coach with the tools for analysis and the easy to follow processes for safer performance gain, which is what our players expect:

Back to the vlog, In the clip above you can see the loading motion in Justine’s back leg as the muscles begin to lengthen in flexion, as gravity forces her down and her back and knees continue to bend, The subtalar joint in her back leg continues that loading by acting according to it’s design, as a torque converter of the down force into eversion(frontal plane adduction) and internal rotation. This acts to complete the loading at the foot/ankle complex, in all three planes of motion.  Torque conversion is an idea many of us understand from our motor cars: the energy created by the up down action of the pistons is mechanically converted into rotation to drive the wheels. It’s the same principle at the subtalar joint which transforms the up down forces into internal rotation of the leg. Click for more on  the motion at the foot/ankle complex.

In the clip below you can see  the beginnings of motion in the opposite direction of each plane as the energy that has been captured by the transformation of the down force meeting ground reaction, is now driving the capacity for motion up the chain in the opposite direction of all three planes, extension, abduction and external rotation:

 

Mass and Momentum

As her body continues to move, her weight or mass and the speed of her movement create a momentum or greater kinetic energy, for movement in all three planes of motion. It’s a chain reaction in upright function, driven by kinetic energy.

I said I wouldn’t continue to critique the seated position video which I described in my introduction , but I must. By sitting you take out the lower limbs and their interaction with the ground, but the arms and the upper body are not floating in space.

The biggest actor for motion of the three, in our musculoskeletal system, is the hip complex, which in a seated position will still load into the chair surface under gravity capturing the forces and transforming them into the kinetic energy, for the arm action of a serve from that seated position.

I also said I wouldn’t comment on the self evident success of wheelchair tennis  and can only say that when I tried it myself at a course, I struggled to control the movements of the wheelchair as I tried to execute strokes. The kinetics do not change but the kinematics do and are beyond the scope of this vlog.

If you manage to view the video I referred to in my introduction, or any of the many others, who try to persuade you of the arm’s dominance in any tennis stroke, beware and be aware that your arms act in a coordinated whole body chain reaction, in all three planes of motion in upright function. I make no apology for the repetition of self evident truth:

The front leg, is now energised by the motion driving up the chain to the hips enabling  them to slide forward to begin the move to rotate the upper body.  The hips are the crossroads of the body and with it’s large rear musculature, act as a torque converter for the energy driving into the trunk and shoulders.

The torque conversion at the hip is unlike that at the subtalar as it now appears to convert the rotational movement moving up into the hips to a rotational movement from the hips, initially driving the torso backwards with the left shoulder dropping down, and then reversing  with a move rotationally forward and up, seen clearly by the position of the chest. Another complex aspect of human movement.

The racket arm having dropped down the back is now being driven upwards towards contact. Both of these motions evidence lengthening and shortening of the muscles in a recoil motion which is a continuation of the kinetic energy being driven up the chain. The kinetic energy evident in this motion is the same energy that has surged up the chain from its initial capture at the base of the chain, as the feet enter the ground.

Conclusion.

I have shown you the Source of the Force, the kinetic energy that the body captures for movement and have illustrated these principles at the Foot/Ankle and Hip complexes. I will leave the third big actor in human movement , the Shoulder Complex for my next vlog .

There is some controversy in tennis circles about the motion of the shoulder in the service action. Internal shoulder rotation is the subject under debate but as it is part of loading it must happen. I’m not sure what others are saying as you have to subscribe to them to find out, but I can only assume they are confusing motion at the shoulder between real bone motion and relative joint motion, another complex human movement made easier to understand and apply with the 3DMAPS process

For now, I hope you have understood a little more of the body’s design for movement, both in the kinematic sense, the chain reaction of integrated complex segments and the kinetic sense, capturing of the energy needed for a chain reaction, in all three planes, in upright function.

Functional training methods based on the 3DMAPS process as a teaching module is under way.

Vaughan Ebrahim LTA accredited Level 4.

Gray Institute, CAFS 2013, 3DMAPS 2017, FGS 2023