What the researchers did
The researcher chose 15 healthy women with a trigger point in their upper trapezius muscle, and matched them 15 similar women without such trigger points. These women were asked to stand upright with their arm slightly forward (shoulder flexed) holding a cable attached to a weight. The women were instructed that when they heard the audio stimulus (a sound) they were to lift their arm holding the weight to shoulder height as fast as possible.
What was measured
Signals to the muscles
The lifting of the weight from a standing position requires the coordinated effort of many muscles. Because of this the researchers used surface electromyography (EMG) to detect signals to the following muscles:
- anterior deltoid
- upper trapezeus
- lumbar paraspinal
- cervical paraspinal
The action of the muscles
In order to detect the action of muscles various sensors were used such as one attached to the cable, force pads in the platform subjects stood on, and others monitoring muscle action in the body.
What they found
The reaction time of muscles is made up of two parts. “Pre-motor” is the time from receiving the stimulus to when the nerves delivered their impulse to the muscles. “Motor” is the time taken from when the muscle receives the nerve impulse to the actual generation of force.
The researchers found that for those with trigger points the pre-motor times were unchanged. That is, the trigger points had no effect on the time taken to detect and interpret the stimuli then transmit the signals to the muscles.
On the other hand, the presence of trigger points was shown to slow the motor time for all muscles except the gastrocnemius. That is, the nerves delivered their impulses in a timely manner, but the muscles were slow in responding and developing force.
Discussion of the results
A trigger point is part of a muscle in a pathophysiological state. It is not surprising that a muscle in such a state would receive a nerve impulse but would be a bit slow to react and generally under perform. However, other muscles not said to be any different to the comparison group received impulses in a timely manner but also reacted slowly. Why did they under perform as well?
The researchers measured timing, but made no mention was made of the strength of the impulses detected by the EMG. Understanding the role the central nervous system (CNS) plays in controlling and coordinating the body it seems the likely explanation is that the CNS detected the state of the upper trapezius muscle and reduced the strength of the impulses to other muscles in compensation. This would mean that trigger points in any muscles could cause the whole body to under-perform.
Screening and treating trigger points
The detriment of a sports person having trigger points in their muscles is clearly demonstrated. An in depth discussion of their treatment is found in a separate research summary, however, most professional sports people have good access to professional masseurs who regularly examine for and treat them. This can be very time consuming and expensive, making it unpractical for ordinary people. A solution is self or home massage under appropriate professional advice. There are several ways to do this, but when used appropriately DrGraeme massagers can deliver professional quality massage enabling average people to benefit from practically unlimited professional quality massage, just like the professional sports people get.
We recommend the best way to get these benefits and keep trigger points at bay is to be examined and advised by a professional who deals with musculoskeletal conditions then implement regular self/home use. This is analogous combining regular dental checkups with daily brushing and flossing.
Yassin, M., et.al. Arm Flexion Influence on Muscle Reaction Time in Females with Active Myofascial Trigger Point. British Journal of Applied Science and Technology, 2015 11(1): 1-9
Samples and practitioner orders
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