In English, ‘pain’ is simply ‘pain’. Whether we’re trying to describe the sharp sting of a paper cut, surgery, or the deep ache after a particularly intense leg day at the gym, we always use the same word.
But in many Eastern cultures, language makes a clear distinction, providing numerous words for the different feelings of pain that, in English, we just don’t have. For example, in Taiwanese, a dull, lingering muscle soreness is called ‘sng’. Similarly, in Mandarin, speakers often complain of ‘suan tong’, which is sour pain; a pain one might feel during a cold or again, after exercise. This linguistic difference isn’t just for fun; it represents a profound reality. The University of Aberdeen has a long-standing commitment to reducing chronic pain, with decades spent researching the condition, which is thought to affect between a third and a half of the population. Their latest research, in partnership with Academia Sinica in Taiwan, found that this cultural difference also reflects a difference in the physiology of pain.
In recent history, scientists have firmly believed that acid buildup in muscles, which occurs during periods of intense exercise or inflammation, activates pain-sensing nerves, known as nociceptors. For a long time, this understanding was thought to reflect the ache in fatigued muscles. However, this new study, published in Science Advances in 2025, changes this assumption.
The researchers found that the nervous system processes muscle soreness and sharp, acute pain differently; they are partially distinct sensory pathways. This changes the game for those with chronic pain, which currently often evades sufficient treatment with typical pain relief methods targeting the traditional nociceptive pathway.
So, what actually is going on inside our muscles?
It was confirmed that acid-sensing in proprioceptors may play a dominant role in chronic soreness. Proprioceptors are specialised sensory neurons located in muscles, tendons and joints; they continuously monitor your body’s position in space, tension and movement, sending real-time information to the central nervous system for balance and coordination. They allow you to have good spatial awareness without using your eyes, triggering reflexes if needed. However, the team found that this is not all they do. These neurons express a molecule called ASIC3, an acid-sensing ion channel. When muscle tissue becomes acidic, ASIC3 in the proprioceptors is activated.
This was tested using models of chronic pain, similar to fibromyalgia (a chronic disorder characterised by widespread musculoskeletal pain, fatigue and sleep disturbances). In animal studies, when they genetically removed the acid sensor from the nociceptive pain neurons, the chronic pain persisted. Yet when it was removed from the proprioceptors, the chronic pain ceased to emerge, suggesting that proprioceptors play a key role in chronic muscle soreness. Additionally, they found that activating proprioceptors could ‘prime’ the system, increasing the likelihood of chronic pain developing.
‘Sngception’ was coined by the team to refer to this new pathway of acid-induced muscle soreness, a separate feeling from nociceptive pain. Importantly, these results were confirmed in a double-blind study with healthy volunteers receiving small intramuscular acid injections, noting ‘soreness’ but not pain. One of the most compelling aspects of their results was a spinal cord injury patient who lost the ability to feel pain in a leg; however, he could still perceive this muscle soreness in the numb limb, highlighting how distinct the pathways may be.
This differentiation could be highly significant for common chronic pain conditions, including arthritis and persistent muscle pain, which are notoriously hard to treat. If new drugs can be developed to target the ‘sngception’ pathway, new treatments become possible.
Speaking to STV News, Dr Guy Bewick, the key researcher at the University of Aberdeen, said:
‘This has the potential to help the many people whose pain is currently inadequately treated’.
Whilst clinical applications remain a future possibility, this monumental shift in conceptual understanding already proves significant. It shows that the Western assumption that all pain fits under one umbrella may have been oversimplifying; muscle soreness is a fundamentally different experience. Further investigation is needed, including a wider investigation into how the animal model fully translates to a human clinical setting. However, if the success is continued, this could mark an era of drug developments that are actually targeted to treat chronic pain. Providing hope and, perhaps more importantly, relief to those affected.