In this vlog I want to build on the ideas in my previous vlog by looking at the three big bio motor units as they move through the transformational zone. My focus will be on the reaction of muscles and joints to the forces of gravity, ground reaction, mass and momentum as they capture kinetic energy and fuel chain reaction movement in all three planes of motion. Logic dictates that I start at the foot/ankle complex as the first big bio motor unit in upright function.
The Foot/Ankle complex.
This complex comprises 28 bones and 33 joints but for simplicity, our focus will be the ankle and subtalar joints and the metatarsal bones in each foot. The two joints act together to enable motion in all three planes and manage the processes of shock absorption and rigid propulsion in forward motion. It’s maybe necessary to understand a little more biology to understand what the complex does in upright function.
Most of us know that the ankle joint acts as a hinge, allowing the foot to flex up and down, shown as dorsi and plantar flexion in the illustration. Motion in the other two planes, side to side and rotation, is enabled by the subtalar joint. In addition it acts as a torque converter, as well as enabling the mobile adapter process.
The subtalar joint is the space between the calcaneus(heel bone) and the talus which sits above it. The articulating surfaces of both bones are uniquely shaped to cause the talus to move sideways and down towards the big toe, unlocking the metatarsals for shock absorption and converting the physical forces into internal rotation in the leg bones above.
You can feel this for yourself by just stepping forward and experiencing the give or spread in the foot to absorb shock. You should also experience a forward, sideways and down movement towards the big toe. This motion is converting the forces into internal rotation moving up the chain and also brings the bones in the foot together to form a rigid propeller for forward motion.
Having understood the biomechanics of the foot/ankle complex, we now need to understand how it drives the chain reaction in any human movement in upright function and where the energy that drives that work (motion) comes from.
The Physical Sources of Forces.
Force/energy for human movement is captured when the initial movement under the force of gravity meets ground reaction force and is transformed into energy, the capacity for work (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 body’s mechanism?
The Biological Mechanism.
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 lower limb muscles in the chain reacting by lengthening, to decelerate the down force. In the transformational zone they contract to capture those forces (gravity and ground reaction) and accelerate the combination as energy for work further up the chain, in upright function in all three planes of motion.
Put more simply, it’s the lengthening to load and contracting to explode of muscles and joints in the foot/ankle complex that capture the energy, the capacity for work (motion). It’s an elastic recoil action in the transformational zone, that fuels motion, in any purposeful human movement in upright function, in all three planes of motion.
Hopefully you now understand the biomechanics of the foot/ankle complex and can see how it captures energy to fuel the chain reaction movement necessary to complete any task . The subsequent capture and distribution of this kinetic energy up the chain will be covered in following posts on the hip and shoulder complexes.
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.
The applications in playing and training.
The foot/ankle complex does all the things mentioned but you may ask what does it mean for my tennis as a player or my coaching others to play? Ask yourself, if this is the design for human movement, what are the outcomes for not working with the design?
- Less than optimal performance at your level.
- Slower less safe performance gain.
- Higher acute injury risk
- Developing chronic dysfunction anywhere in the chain.
Split Step/Unit Turn
In tennis the split step and unit turn are terms we have all heard of and, to varying degrees, we understand as preparatory stages. In my experience, at the recreational level, it is seen as a ready position rather than a means of capturing energy for a stroke.
It’s part of the arm dominant method prevalent in the recreational players who fail to appreciate the importance of footwork in a game played from the ground upwards. You can and should ask your coach why it’s importance is not stressed and should more time be spent on it in your lessons?
Now that you can appreciate the role of the foot/ankle complex in capturing the kinetic energy for authentic motion, you can begin to see why the split step and unit turn are vital parts of the chain reaction in a tennis stroke.
Look at these three clips to see Justine’s perfect example and Tom’s before and after footwork..
You can play and have success at any level without loading the body according to it’s design, but you will know from experience that ignoring design in mechanical processes, inevitably leads to sub optimal performance and frequent breakdown.
In conclusion, I hope you have a better understanding of the first of the three big bio motor units you have and how to use the foot/ ankle complex more effectively in your play.
You can see the frequent and vital use of the split step and unit turn not just in the ready position but throughout movement in play. in these clips. I have separated them for clarity but in reality, at the professional level, they merge into one move in reaction to the greater ball speeds:
Vaughan Ebrahim, LTA accredited Level 4
Gray Institute movement specialist, CAFS 2013, 3DMAPS 2017, FGS and FT 2023.