PainSci commentary on Ge 2012: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.
Ge et al. found a dozen health volunteers with one (latent, painless) trigger point in the trapezius muscle on one side, but not the other. Then they subjected them to a bit of a torture test: holding their arms up for as long as possible, with EMG needles stuck in their shoulders (EMG can measure muscle fatigue, with some caveats, see Cifrek, Arabadzhiev, González-Izal).
So, how long can you hold your arms straight out the sides? They did fairly well, about seven minutes, but it got uncomfortable. On a pain-scale of 10, the subjects rated the non-trigger point side just over a 2 … but much higher on the trigger point side, at about 6.5.
And the EMG results demonstrated that muscles with trigger points show clear signs of greater fatigability. Specifically and most importantly, the trigger point side showed significant decreases in mean power frequency, which correlates with muscle ischemia, or poor oxygenation (a suspected biological feature of trigger points).
These results suggest that muscle tissue around a clinically defined trigger point is different from other muscle tissue in an objectively verifiable way.
~ Paul Ingraham
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
OBJECTIVE: Muscle fatigue is prevalent in acute and chronic musculoskeletal pain conditions in which myofascial trigger points (MTPs) are involved. The aim of this study was to investigate the association of latent MTPs with muscle fatigue.
DESIGN: Intramuscular electromyographic (EMG) recordings were obtained from latent MTPs and non-MTPs together with surface EMG recordings from the upper trapezius muscles during sustained isometric muscle contractions in 12 healthy subjects.
OUTCOME MEASURES: Normalized root mean square (RMS) EMG amplitude and mean power frequency (MNF) were analyzed. The rate of perceived exertion and pain intensity from MTP side and non-MTP side were recorded.
RESULTS: Pain intensity on the MTP side was significantly higher than the non-MTP side (P < 0.05). Intramuscular EMG from latent MTPs showed an early onset of decrease in MNF and a significant decrease at the end of fatiguing contraction as compared with non-MTPs (P < 0.05). Surface EMG from muscle fibers close to latent MTPs presented with an early onset of the increase in RMS amplitude and the increase was significantly higher than that from non-MTPs at the end of sustained isometric contraction (P < 0.05).
CONCLUSIONS: A latent MTP is associated with an accelerated development of muscle fatigue and simultaneously overloading active motor units close to an MTP. Elimination of latent MTPs and inactivation of active MTPs may effectively reduce accelerated muscle fatigue and prevent overload spreading within a muscle.
- “Surface EMG based muscle fatigue evaluation in biomechanics,” Mario Cifrek, Vladimir Medved, Stanko Tonković, and Sasa Ostojić, Clin Biomech (Bristol, Avon), 2009.
- “Interpretation of EMG integral or RMS and estimates of "neuromuscular efficiency" can be misleading in fatiguing contraction,” Todor I Arabadzhiev, Vladimir G Dimitrov, Nonna A Dimitrova, and George V Dimitrov, Journal of Electromyography & Kinesiology, 2010.
- “Electromyographic models to assess muscle fatigue,” Miriam González-Izal, Armando Malanda, Esteban Gorostiaga, and Mikel Izquierdo, Journal of Electromyography & Kinesiology, 2012.
- “Microscopic features and transient contraction of palpable bands in canine muscle,” D G Simons and W C Stolov, Am J Phys Med, 1976.
- “Endplate potentials are common to midfiber myofacial trigger points,” David G Simons, Chang-Zern Hong, and Lois Statham Simons, Am J Phys Med Rehabil, 2002.
- “Two-dimensional ultrasound and ultrasound elastography imaging of trigger points in women with myofascial pain syndrome treated by acupuncture and electroacupuncture: a double-blinded randomized controlled pilot study,” Cristina Emöke Erika Müller, Maria Fernanda Montans Aranha, and Maria Beatriz Duarte Gavião, Ultrason Imaging, 2015.
- “Induction of muscle cramps by nociceptive stimulation of latent myofascial trigger points,” Hong-You Ge, Yang Zhang, Shellie Boudreau, Shou-Wei Yue, and Lars Arendt-Nielsen, Exp Brain Res, 2008.
- “Assessment of myofascial trigger points (MTrPs): a new application of ultrasound imaging and vibration sonoelastography,” Siddhartha Sikdar, Jay P Shah, Elizabeth Gilliams, Tadesse Gebreab, and Lynn H Gerber, Conf Proc IEEE Eng Med Biol Soc, 2008.
- “Uncovering the biochemical milieu of myofascial trigger points using in vivo microdialysis: an application of muscle pain concepts to myofascial pain syndrome,” Jay P Shah and Elizabeth A Gilliams, Journal of Bodywork & Movement Therapies, 2008.
- “Ability of magnetic resonance elastography to assess taut bands,” Qingshan Chen, Jeffrey Basford, and Kai-Nan An, Clin Biomech (Bristol, Avon), 2008.
- “Identification and quantification of myofascial taut bands with magnetic resonance elastography,” Qingshan Chen, Sabine Bensamoun, Jeffrey R Basford, Jeffrey M Thompson, and Kai-Nan An, Archives of Physical Medicine & Rehabilitation, 2007.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Exercise and education versus saline injections for knee osteoarthritis: a randomised controlled equivalence trial. Bandak 2022 Ann Rheum Dis.
- Association of Lumbar MRI Findings with Current and Future Back Pain in a Population-based Cohort Study. Kasch 2022 Spine (Phila Pa 1976).
- A double-blinded randomised controlled study of the value of sequential intravenous and oral magnesium therapy in patients with chronic low back pain with a neuropathic component. Yousef 2013 Anaesthesia.
- Is Neck Posture Subgroup in Late Adolescence a Risk Factor for Persistent Neck Pain in Young Adults? A Prospective Study. Richards 2021 Phys Ther.
- Sudden amnesia resulting in pain relief: the relationship between memory and pain. Choi 2007 Pain.