Rio 2016: The Science of Usain Bolt's Speed - Part 1
Published on August, 8th 2016
By Dr. Greg Wells
This information first appeared in my book Superbodies: Peak Performance Secrets from the World’s Best Athletes.
With the Olympics in Rio underway I thought it would be cool to explore some of the physiology of the most legendary athletes. Usain Bolt certainly fits into this category. He’s aiming for 3 gold medals in 3 consecutive Olympics. Now, while you might normally think that his performance is powered by his muscles (and it is), there is one deeper level of physiology we can explore that will help you to appreciate how incredible his performances are. Let’s take a look at the what happens to the nervous system during the 100 m dash.
Let’s look at Usain Bolt’s world record 9.58-second 100-metre dash. Exploring “the start” is fascinating when we consider the lighting storm of electrical activity involved. There are three steps to the start: the “On Your Mark,” “Get Set” and “Go” steps. Let’s take a look at each of these steps.
Photo (c) copyright Dr. Greg Wells, 2016. All Rights Reserved.
ON YOUR MARK!
When Usain Bolt approached the blocks and placed himself in the position to start the race, he was still physically relaxed, but his brain was actively preparing to run. The parietal and frontal lobes of the brain were preparing the appropriate physical activities and making decisions about the motor activities about to happen. The prefrontal cortex was making plans about how to execute the start and to run a world-record race. The frontal cortex was receiving information from axons (which are connected to the parietal lobe) regarding the spatial orientation of all the muscles, limbs and joints in the body. The activation of the motor areas of the brain occurred because of the nerve impulses coming through sensory nerves from the ears and eyes, which provide information about the environment. The crowd noises stimulated the auditory nerves, and the sights of the stadium activated the visual nerves and related areas of the brain. This information was synthesized to determine the best reactions to plan and execute. Further, at this point the sympathetic nervous system— which acts to dilate blood vessels, increase heart rate and breathing, and pump glucose into the bloodstream—was being activated.
As soon as the starter said “Set,” the premotor areas of the brain, located in the back of the frontal lobe, built the exact strategies for the movement in preparation for the upcoming execution of the start. The brain made calculations about the coordinates of the starting blocks, the track and the finish line, and worked with the cerebellum to plan and calibrate the required movements. The cerebellum is the air-traffic controller for signals related to movements that pass from the back of the frontal lobes (areas where motor function and movements are controlled) to and from the spinal cord. There are so many neurons in the cerebellum that, although it makes up only 10% of the brain’s total volume, it accounts for more than 50% of its neurons. The cerebellum also acts as a learning center for movement patterns. As it receives (from the proprioceptors) input on the joints and muscles of the limbs, it constantly compares the actual movements made by the body with the planned movements that were called for by the brain before the initiation of the movement. So the movement patterns that we execute— such as throwing a baseball or, in this case, running—get calibrated over time and become increasingly refined.
For the beautiful movements of sports to happen, the brain, nerve pathways and muscles must all work in a coordinated and sequenced manner. The integrated signals from the brain through to the muscle contraction that create movement are called a motor pattern. Well-developed mo- tor patterns that have been refined over years of practice are why great athletes make sports look so easy. Each movement—and there are no extra ones—is perfectly programmed and re- fined. Think of a world-class diver repeating the same exacting, fluid movements thousands of times throughout a career in order to compete at the highest level. The performance appears effortless, but only because years of training have refined the motor patterns that are stored in the brain and coordinated in the cerebellum so that movements are fluid and efficient. The cerebellum learns how to calibrate the signals that it commands to the muscles to control the duration and strength of the stimulus and, thus, the precision of the movement. As Usain Bolt holds his start position in the blocks, motor patterns that have been programmed through thousands of repetitions over years of practice and training are about to be activated.
As soon as the starter’s gun goes off , a flurry of activity begins. Mo- tor commands from the motor cortex at the back of the frontal lobe are considered by the cerebellum. The final movement commands are then sent down the spinal cord
and from there to the peripheral nervous system and the motor neurons.
The fundamental component of the brain and the nervous system is the neuron. This is a specialized cell that consists of three main components—the dendrites, the cell body and the axon. The dendrites are branches of the neuron that connect to other neurons and receive signals, which they carry back to the cell body. The cell body, which is the main part of the neuron, contains the nucleus, DNA and mitochondria, among other
components. The axon carries electrical signals from the cell body to other neurons or to target organs such as muscle cells. Axons vary in size, from microscopic lengths in the brain to nearly two metres long if they run all the way to the legs.
Although signals can pass through their own dendrites and axons at extremely high speeds (from 3 to 300 kilometres per hour), communication between neurons (or target organs) hap- pens chemically at a much slower pace. When the electrical signal arrives at the junction be- tween neurons or between the neuron and the muscle (called a nerve terminal), it triggers a series of events that result in the release of neurotransmitters into the space between the originating nerve and the target organ. This space is called a synapse.
When signals pass across the synapse, the signal from the originating nerve can (1) trigger a new nerve impulse if it is a neuron-to-neuron connection; (2) trigger a muscle contraction if it is a nerve-to-muscle connection; or (3) trigger the release of a hormone from an endocrine gland if it is a nerve-to–endocrine gland connection. Neurotransmitters carry the signal between the originating nerve and the adjacent nerve or target organ.
The actual contraction of the muscle fibres is initiated by the release of the neurotransmitter acetylcholine into the synaptic gap in the neuromuscular junction. The acetylcholine travels across the synapse and binds to receptors on the muscle fibre. This action triggers channels in the membranes of the muscle to release calcium, which diff uses into the myofibrils and initiates the binding of actin and myosin filaments—and, thereby, muscle contraction. At that point, Usain Bolt is off and running to a world record.
More coming in tomorrow’s post!
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