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,” Cifrek et al, Clin Biomech (Bristol, Avon), 2009.
- “Interpretation of EMG integral or RMS and estimates of "neuromuscular efficiency" can be misleading in fatiguing contraction,” Arabadzhiev et al, Journal of Electromyography & Kinesiology, 2010.
- “Electromyographic models to assess muscle fatigue,” González-Izal et al, Journal of Electromyography & Kinesiology, 2012.
- “Microscopic features and transient contraction of palpable bands in canine muscle,” Simons et al, Am J Phys Med, 1976.
- “Endplate potentials are common to midfiber myofacial trigger points,” Simons et al, 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,” Müller et al, Ultrason Imaging, 2015.
- “Induction of muscle cramps by nociceptive stimulation of latent myofascial trigger points,” Ge et al, Exp Brain Res, 2008.
- “Assessment of myofascial trigger points (MTrPs): a new application of ultrasound imaging and vibration sonoelastography,” Sikdar et al, 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,” Shah et al, Journal of Bodywork & Movement Therapies, 2008.
- “Ability of magnetic resonance elastography to assess taut bands,” Chen et al, Clin Biomech (Bristol, Avon), 2008.
- “Identification and quantification of myofascial taut bands with magnetic resonance elastography,” Chen et al, 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:
- Inciting events associated with lumbar disc herniation. Suri 2010 Spine J.
- Prediction of an extruded fragment in lumbar disc patients from clinical presentations. Pople 1994 Spine (Phila Pa 1976).
- Characteristics of patients with low back and leg pain seeking treatment in primary care: baseline results from the ATLAS cohort study. Konstantinou 2015 BMC Musculoskelet Disord.
- Effectiveness and cost-effectiveness of universal school-based mindfulness training compared with normal school provision in reducing risk of mental health problems and promoting well-being in adolescence: the MYRIAD cluster randomised controlled trial. Kuyken 2022 Evid Based Ment Health.
- Is there a relationship between throbbing pain and arterial pulsations? Mirza 2012 J Neurosci.