Friday 25 November 2022

Human Movement - Part One

All external physical actions that we as humans, or indeed any animal, make revolves around movement. Movement is a kinetic chain that is made up of three core components: the nervous system, muscular system and skeletal system. This article will deal with the first aspect: the nervous system.

Table of contents

The nervous system

Your nervous system is a communication network from the brain to the rest of your body. Without it your body would fail to function in any capacity. The brain sends electrical impulses in the form of neurons throughout the body via the nervous system for specific functions to be carried out such as the recruitment of muscles, movement patterns and digestion of food. The three main functions of the nervous system are:

  • Sensory function: where the nervous system senses changes in the internal or external environment of the body, for example when you go from a more stable surface onto an more unstable surface.
  • Integrative function: where the nervous system analyses the sensory input and interprets how to deal with it allowing for an appropriate response to it.
  • Motor function: the neuromuscular response to the sensory input, such as alterating your walking pattern when going from a stable to unstable surface.

Another key component of the nervous system, especialy in regards to movement, is proprioception. This is the body's ability to determine the relative position and movement of the body at any given time. Improving your proprioception improves your balance and cordination and helps your body to unconsciously adapt to to its surroundings. It helps ensure proper movement patterns are learnt to maximise and enchance your performance as well as help lessen the chance of injury from improper movement.

Proprioception, the art of balance and co-ordination. Image from Kind PNG.

(Back to top)

Nervous system sub-divisions

The nervous system can be divided into two core components:

  • Central Nervous System (CNS): Composed of the brain and spinal cord. It controls the activities of the body.
  • Peripheral Nervous System (PNS): Composed of the nerves that connect the CNS to the rest of the body. It sends sensory input to the CNS and relays the corresponding response.
The CNS and PNS. Diagram from Cleveland Clinic.

(Back to top)

Autonomic and somatic nervous system

The peripheral nervous system is made up of twelve cranial nerves, thirty-one pairs of spinal nerves and sensory receptors. The Peripheral Nervous System consists of two parts:

  • Autonomic: Responsible for the control of involuntary bodily functions such a breathing and digestion. It is further divided into the:
    • Sympathetic: Prepares the body for stress-related acitivies, producing localised and reflex adjustments, such as increased heart-rate, sweat, increased breathing rate and blood pressure. Effectively the "fight or flight" response.
    • Parasympathetic: Restores the body to its normal pre-stress level allowing for rest and recoevery from the stress.
  • Somatic: Responsible for voluntary movements such as movement.
The Autonomic and Somatic nervous systems. Diagram from Wikipedia.

(Back to top)

Sensory receptors

For the peripheral nervous system to operate properly it requires specialised sensory receptors to receive environmental stimuli and convert it into sensory information for the central nervous system to receive and produce a response to. The four categories of these sensory receptors are:

  • Chemoreceptors: Responds to chemical stimulus such as smell and taste.
  • Nocieceptors: Responds to pain.
  • Photoreceptors: Found in the retina, they respond to light, converting it into an electrical signal for the brain to process stimulating physiological processes such as sight.
  • Mechanoreceptors: Responds to external mechanical stimuli such as touch, pressure, stretching, motion and sound waves. It enables the brain to detect touch, sounds, proprioception and physical movement.

(Back to top)


Of all the sensory receptors, mecahnoreceptors are the most relevant for exercise as they pertain to movement. These receptors can be found in muscles, ligaments, tendons and joint capsules. Mechanoreceptors can be broken down into:

  • Golgi tendon organs (GTOs): Found where muscle fibers insert into tendons, these sense changes in muscular tension and the rate of it. When activated it helps prevent injury or excessive stress by causing the muscle to relax.
  • Joint receptors: Found in joint capsules, they respond to acceleration, deceleration and pressure of a joint. They help inform the CNS of extreme joint positions and help avoid injury, and can also initiate a reflexive inhibitory response.
  • Muscle spindles: These run parallel to muscle fibers and inform the CNS of the length of the muscle fiber and its rate of change. It helps prevent muscular injury by signalling the muscle to contract if the muscle is over-stretched.
Location of a muscle spindle and the Golgi Tendon Organ and the output and input to and from the spinal cord. Diagram from UESCA.

(Back to top)

Impact of training

So, how does training impact these receptors, your nervous system and indeed movement? The majority of improvements, or "gains", made after embarking on training result from adapations within your nervous system. This is because by performing a movement such as an exercise, especially a new one, and consistently performing it over a period of time, the nervous system adapts to the new stimulus and improves your response to it. This is all achieved by the various receptors listed above providing continual feedback for the brain to process and respond to. Hence the more you practice a new movement, the better you will get over time as your brain refines your responses. There is a reason why they say practice makes perfect!

(Back to top)

Part Two to follow.

Lyle Richardson,
Gym Pal - Your Friend In Fitness


Post a Comment