Muscle Fatigue, Stiffness & Exercise
Do you feel like your muscles just don’t have the endurance and strength to get through the day? Admittedly, your profound sense of exhaustion could be partly due to changes in the brain. But you can’t ignore your muscles as a source of fatigue because overworking them makes your symptoms escalate.
Morning stiffness is another common symptom that can’t be brushed off as a problem with the brain. How could you wake up each morning feeling like roadkill? When the brain is asleep, the body rejuvenates. With fibromyalgia, you wake up feeling at least 10 years older.
Morning stretches reduce stiffness and muscle cramps, but each day starts anew. The moment you open your eyes, you are greeted by a body that is tight as shoe-leather and feels like it was a punching bag all night. You probably have a fitness program too, but if you stop it, your body forgets how to move (it’s like fibrofog of the muscles). What could be causing so many roadblocks?
Working Triggers
Fibromyalgia patients have an average of 12 to 15 active myofascial trigger points (MTPs) in which the muscle fibers are bunched together like knots.1 In another dozen muscles, people with fibromyalgia have latent MTPs that are smaller than the active ones but they have not yet evolved into serious pain generators. Could all of these MTPs contribute to why your muscles get tuckered out so easily?
The relationship between accelerated muscle fatigue and MTPs was investigated by Hong-You Ge, M.D., Ph.D., and his team in Denmark.2 He used healthy, young subjects with just one latent MTP in the upper trapezius (the triangular muscle on each side that covers your shoulder blades). If a single latent MTP alters trapezius muscle performance in fit people, it may explain why your MTP-loaded body gets exhausted easily.
Participants performed a sustained contraction of both trapezius muscles by holding their arms straight out from their sides (forming a T) and making contact with a bar above their arms. One side contained a latent MTP while the other didn’t, allowing Ge to measure the impact of the trigger point during the contraction.
A tiny needle was inserted into the muscle near the MTP to pick up the electromyographic (EMG) signal throughout the contraction period. As muscles fatigue, the EMG signal dwindles. A surface EMG probe was placed one inch away to detect if nearby muscle fibers had to pitch in during the contraction. Muscle and surface EMG probes were put in the same place on the non-MTP side for comparison.
The pain produced by the 7-minute contraction was double on the MTP side. In addition, the presence of the MTP caused a dramatic drop in force output from the muscle and many more fibers were recruited to do the same job.
“We used objective EMG measures in this study to quantify muscle fatigue and showed it occurs approximately four times faster near latent MTPs,” says Ge. “This suggests that fibromyalgia patients are quickly getting tired and fatigued due to the existence of a large amount of MTPs (both active and latent). They are not faking their perceived exertion ratings.”
MTP Vortex
If muscle fibers harboring an MTP cannot maintain a constant energy output, healthy fibers in other areas of the muscle get sucked in to doing the work. This may cause an overload of the recruited muscle fibers up to an inch away and could lead to the development of new MTPs. “As a result, MTP-related pain spreads within a muscle and the power output from it further decreases,” says Ge.
Spreading the “MTP love” is the fact that muscles must work in pairs. When you contract a muscle, the spinal cord neurons tell the opposite muscle in the pair to relax. However, when a muscle harbors an MTP, the relaxation signal going to the other muscle is weakened.3 “This means the contracting muscle has to work harder to achieve the same movement, leading to muscle overuse and fatigue,” says Ge.
MTPs cause muscle tug-of-wars that quickly wear you out!
No Trade-Offs
Rest breaks, shifting positions, and changing tasks occur in everyday life. A similar “sharing the load” phenomenon governs the way muscles should work as well, but MTPs interfere with this process.
Holding any muscle in a contracted state, even for 30 seconds at a time, involves shiftwork or rotations within a small subpopulation of fibers. Some subsets of fibers work for a period of time and then stop, while others take their place. This trade-off of activity is a healthy way to prevent burnout within a muscle.
“When one or more MTPs are in a muscle,” says Ge, “the motor units are firing all of the time; they never stop. The normal shifting mechanism is lost, leading to premature development of muscle fatigue.”
Not only do latent MTPs (which don’t generally hurt) prevent muscles from sharing the workload, pain interferes with this process as well.4 When healthy women were injected with a pain-producing substance in their upper trapezius muscle, the shifting mechanism disappeared. However, the comparison group of fibromyalgia patients showed more rapid muscle exhaustion, thought to be partly due to reduced capillary blood flow.
Stiff Goings
What could be causing you to feel so stiff, even if you haven’t overdone it? Ge says, “Each tight muscle band (a bundle of muscle fibers) is in a state of contraction no matter whether you are active or at rest. Muscle fibers with MTPs are working all the time and are always in a tensed state.”
MTP blood flow is reduced and adds to muscle fatigue by limiting the supply of energy nutrients. But MTPs also contribute to stiffness because when the muscle is vibrated, these areas lack fluidity like the rest of the muscle.5 The drop in blood flow at the MTPs is due to too many signals traveling from your spinal cord out to these muscle regions.
The sympathetic branch of your nervous system in your tissues is responsible for cranking down on blood flow. In general, fibromyalgia patients have a hyperactive sympathetic system, which may help sustain your MTPs. Your parasympathetic system works in opposition to your sympathetic branch, but it is not as active as it should be in people with fibromyalgia.
The parasympathetic branch relaxes your muscles and expands blood vessels to increase flow. Anything that you can do to increase the parasympathetic “calming” effect should improve muscle blood flow and reduce muscle stiffness. For example, try incorporating deep, relaxation breathing exercises into your daily activities, such as those taught for yoga and similar mind-body movements.
If you wake up in the morning feeling like your muscles are made from dried leather, Ge explains: “Chronic pain from MTPs worsens sleep and poor sleep leads to sympathetic dominance over the parasympathetic system. The sympathetic imbalance aggravates the muscle fibers containing MTPs, so that they fire all night long (e.g., calf cramps during sleep). The muscle fibers become so terribly taut and stiff by morning because they were busy working all night.”
“Fibromyalgia patients may experience some good days after a sound night of deep sleep when the parasympathetic system dominates,” says Ge. “Likewise, warm water or a hot shower activates the parasympathetic activity. This increases blood flow, reducing MTP activity and muscle stiffness.”
Oxygen Debt
Near-infrared devices used to check your blood oxygenation are commonplace. Just place your finger in a small clip and the results are quickly generated. Adopting similar technology, a customized machine was engineered by Guoqiang Yu, Ph.D., at the University of Kentucky, to assess blood flow and oxygen use in the exercising thigh of fibromyalgia patients and matched healthy controls.6
The same fatiguing set of contractions was done by each group and a test ensured that all subjects performed the same workload. As a muscle contracts, the hemoglobin in the blood releases its oxygen through the small capillaries and breathing replaces the oxygen used. The oxygen is used by the muscle mitochondria to make energy fuel for the exercising muscle.
The fibromyalgia patients differed in two ways: the amount of oxygen consumed by the exercise (but same workload) was less and there was a time delay for the hemoglobin to fill back up with oxygen. It’s as though the muscles continued to consume oxygen after the exercise stopped in the fibromyalgia group. In other words, an oxygen debt occurred because there was not enough supplied during exercise.
Muscle biopsies in the same subjects were examined in a second study.7 “The most pronounced difference in muscle between subjects with fibromyalgia and healthy controls in this study was reduced capillary density in fibromyalgia,” says Yu. In addition, the number of smaller-sized muscle fibers was greater and the enzyme needed to consume oxygen was less. All these factors enhanced the exercise-induced fatigue in fibromyalgia.
Reducing Burnout
Use warm water to reduce MTP-related tension and increase muscle blood flow. The heat coupled with any daytime medications you take for discomfort should improve the shift-work processes within your muscles so they do not wear out as quickly. However, eliminating your MTPs will produce the best results.
What can you do about the reduced number of capillaries and oxygen debt in your muscles? Take lots of breaks during very mild aerobics to accommodate the lag in oxygen delivery. To build stronger muscles and more capillaries, try lots of repetitions with next to no resistance. As you will read in the section on strengthening, you can then move up to using elastic strips.
- Alonso-Blanco C, et al. Clin J Pain 27:405-13, 2011.
- Ge HY, et al. Pain Med 13:957-64, 2012.
- Ibarra JM, et al. J Pain 12:282-8, 2011.
- Falla D, et al. J Electromyogr Kinesiol 20:457-64, 2010.
- Sikdar S, et al. Arch Phys Med Rehabil 90:1829-38, 2009.
- Shang Y, et al. Arthritis Res Ther 14(6):R236, 2012.
- Srikuea R, et al. Arthritis Rheum 65(2):519-28, 2013.