A trigger point (TrP) is a small nodule of irritation located in the belly of a muscle or the surrounding fascia, which restricts muscle action(1). It has been found in human studies that the presence of a TrP in a muscle significantly reduces muscle strength(2). TrPs can be identified by palpation, especially when feeling across the muscle fibres.
When a trigger point is compressed, it can result in a jump (involuntary movement), a localised twitching of the muscle, or pain(3,4,5,6). The localised twitching is a brief, visible contraction which happens as an involuntary spinal reflex. The pain response is thought to be because the trigger point contains sensitive areas which contain pain (nociceptive) receptors(1).
Trigger points in humans, and also animals, have been found to arise due to:
muscle tension or overuse (resulting in micro-trauma)
lack of exercise
not stretching
insufficient rest / sleep disturbance
nervous system over exertion
poor circulation
compensatory movement
ageing
injury
bad posture
joint problems(7)
There are different types of TrPs including:
Primary: found in the middle of a muscle belly, when palpated they cause severe pain. They can be caused by either macro-trauma (e.g. an injury) or micro-trauma (e.g. chronic incorrect muscle use)(8)
Secondary: develop in muscles away from the initial problem area and occur in response to pre-existing TrPs or other diseases(9)
Active: causes tenderness and referred pain when palpated
Latent: does not cause spontaneous pain, only local pain when compressed firmly(10)
Trigger points in animals can be treated by a veterinary physiotherapist using an assortment of techniques, including:
Heat applied to the affected area
Massage, e.g. effleurage to improve blood flow and circulation
Direct pressure over the TrP until it releases
Light movement
To avoid the formation of TrPs, the influencing factors need to be addressed, for example: posture retraining, passive stretching, massaging and strengthening exercises. The research mentioned in this blog highlights the importance of identifying TrPs, treating them and reducing the chance of developing them in the first place by correct and careful management.
References
Hong, CZ. 1996. Pathophysiology of myofascial trigger point. Journal of the Formosan Medical Association, 95(2), pp.93-104.
Celik, D. and Yeldan, I. 2011. The relationship between latent trigger point and muscle strength in healthy subjects: A double-blind study. Journal of Back and Musculoskeletal Rehabilitation, 24(4), pp. 251-256.
Simons D.G., and Travell J.G. 1998. Travell & Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual: Volume 1: Upper Half of Body. Philadelphia: Lippincott Williams and Wilkins.
Alvarez D.J. and Rockwell P.G. 2002. Trigger points: diagnosis and management. American Family Physician, 65(4), p.653.
Davidoff R.A. 1998. Trigger points and myofascial pain: toward understanding how they affect headaches. Cephalalgia, 18(7), pp.436-48.
Vázquez Delgado E., Cascos-Romero J. and Gay Escoda C. 2009. Myofascial pain syndrome associated with trigger points: a literature review.(I): Epidemiology, clinical treatment and etiopathogeny. Medicina Oral, Patología Oral y Cirugia Bucal, 14(10), pp.494-498.
Wauters, S. 2023. Trigger Points. Physiopedia. Available at: https://www.physio-pedia.com/index.php?title=Trigger_Points&oldid=328301
Jaeger, B. 2013. Myofascial trigger point pain. Alpha Omegan, 106(1), pp.14-22.
Niel-Asher S. 2014. The concise book of trigger points. Berkeley: North Atlantic Books.
Fernández-de-Las-Peñas C., and Dommerholt J. 2018. International consensus on diagnostic criteria and clinical considerations of myofascial trigger points. Pain Medicine, 19(1), pp.142-50.
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