How can some people persist playing a sport without realising that they have broken a bone, while in another situation a paper cut can be excruciating?
Firstly ALL pain experiences are a normal human response to what your individual brain perceives is a threat or potential threat. Pain is subjective.
The intensity of pain that you experience in not an accurate reflection of an amount of tissue damage.
The International Association for the Study of Pain IASP defines pain as:
“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”. 1.
Acute pain is defined as; “pain of recent onset and probable limited duration. It usually has an identifiable temporal and causal relationship to injury and disease”.
Chronic pain “commonly persists beyond the time of healing of an injury and frequently there may not be any clearly identifiable cause”. 2.
Many varied sensory signals from the periphery of the body contribute to the experience of pain. They may be from mechanical, temperature or pH (acid/ alkali) sensors.
These signals of threat or potential threat are not PAIN. They are called nociception and convey information to the brain via the spinal chord.
The central nervous system responds to this information by activating neural and chemical processes that regulate and control body functions.
Even before a child is taught that a stove is hot humans have a reflex protective mechanism that rapidly withdraws the hand from a noxious heat source before serious damage is able to occur. This enables us to survive dangerous situations.
Plasticity is exhibited by both sensory nerves and the brain, whereby their properties or behaviour change in response to nociception signals. The sensitivity of sensory nerves is a dynamic process of modulation whereby sensitivity can be increased or decreased.
Body tissues have remarkable ability heal after injury, yet sometimes memories of pain persist in the brain and can alter the sensitivity of perception of pain. Sometimes we even anticipate pain when repeating an action that triggered a painful experience in the past. Part of “pain memory” includes thoughts, beliefs and emotions, which in turn become nerve impulses which contribute to the threat level perceived by the brain. Our brain is like an amplifier that has the ability to turn the volume of pain either up or down by releasing different chemicals that affect our nerves’ sensitivity. Some of these chemicals excite the nerves alerting to an increased sense of danger and other chemicals calm the nerves down, signalling that there is not a threat. The brain is continually assessing danger levels and influencing nerves and chemicals accordingly.
Sometimes the brain becomes so bombarded with signals that it gets stuck in threat mode. The central nervous system has become sensitised. This can result in persistent pain (long after tissues have healed); increase in pain intensity; pain in other locations and even minor movements are perceived as painful.
A thorough examination, history and diagnosis by a qualified clinician are important in order to address all contributing factors so that solutions can be found.
1. International Association for the Study of Pain IASP Classification of chronic pain descriptions of chronic pain syndromes and definitions of pain terms. Second Edition1994 Editors: Merskey and Bogduk
2. Ready L and Edwards W. The management of acute pain a practical guide 1992 IASP.
3. Butler D and Moseley L. Explain Pain. Noigroup Publications 2003