Thammasat University students interested in allied health sciences, physiology, medicine, nursing, sports science, clinical biomechanics and related subjects may find it useful to participate in a free 5 June Zoom webinar on Muscle failure: the role and mechanisms of energy in skeletal muscle fatigue.

The event, on Wednesday, 5 June 2024 at 4pm Bangkok time, is presented by the Institute of Advanced Studies (IAS), Loughborough University, Leicestershire, the United Kingdom.

The TU Library collection includes several books about different aspects of muscle fatigue.

Students are invited to register at this link:

https://us06web.zoom.us/webinar/register/WN_TEIXPiH4TDytXIffcnG7ZA#/registration

The speaker will be Professor Niels Ørtenblad, who teaches sports science and clinical biomechanics at the University of Southern Denmark, Odense (SDU).

The event announcement notes:

Skeletal muscles have an impressive force and power-generating capacity. However, with intense or prolonged activation, muscle function is reduced. Despite the broad interest of the scientific community, fundamental questions remain unsolved about how activation is affected by exercise or disuse and how metabolism affects muscle regulation.

Professor Ørtenblad will discuss metabolic factors contributing to impaired force-generating capacity, particularly focusing on the role of muscle glucose stores (glycogen).

Muscle fatigue: general understanding and treatment, an article posted on the website of Experimental & Molecular Medicine, suggests:

Abstract

Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.

Introduction

Fatigue is a common non-specific symptom experienced by many people and is associated with many health conditions. Often defined as an overwhelming sense of tiredness, lack of energy and feeling of exhaustion, fatigue relates to a difficulty in performing voluntary tasks.1 Fatigue accumulation, if not resolved, leads to overwork, chronic fatigue syndrome (CFS), overtraining syndrome, and even endocrine disorders, immunity dysfunction, organic diseases and a threat to human health.

There are many different fatigue classification methods. According to its duration, fatigue can be classified into acute fatigue and chronic fatigue. Acute fatigue can be quickly relieved by rest or life-style changes, whereas chronic fatigue is a condition defined as a persistent tiredness lasting >months that is not ameliorated by rest.2, 3, 4 Fatigue can also be classified as mental fatigue, which refers to the cognitive or perceptual aspects of fatigue, and physical fatigue, which refers to the performance of the motor system.1

Muscle fatigue is defined as a decrease in maximal force or power production in response to contractile activity.5 It can originate at different levels of the motor pathway and is usually divided into central and peripheral components. Peripheral fatigue is produced by changes at or distal to the neuromuscular junction. Central fatigue originates at the central nervous system (CNS), which decreases the neural drive to the muscle.5, 6 Muscle fatigue is a commonly experienced phenomenon that limits athletic performance and other strenuous or prolonged activity. It is also increases and restricts daily life under various pathological conditions, including neurological, muscular and cardiovascular disorders, as well as aging and frailty. This review primarily focuses on muscle fatigue, particularly during intense exercise, to provide a basic understanding and potential therapies for muscle fatigue.

Factors that affect muscle contraction and fatigue

The production of skeletal muscle force depends on contractile mechanisms, and failure at any of the sites upstream of the cross-bridges can contribute to the development of muscle fatigue, including nervous, ion, vascular and energy systems.7 Specifically, metabolic factors and fatigue reactants during the process of contraction, such as hydrogen (H+) ions, lactate, inorganic phosphate (Pi), reactive oxygen species (ROS), heat shock protein (HSP) and orosomucoid (ORM), also affect muscle fatigue. […]

Nutritional supplements

Several nutritional factors that may limit exercise performance have been identified, thus leading to the widespread use of nutritional strategies. Nutritional supplementation is regarded as legal by the International Olympic Committee (IOC) and, therefore, has gained popularity as a way to achieve performance enhancement. Nutritional supplements can be grouped into dietary supplements (for example, multivitamins, fish oils and glucosamine sulfate/chondroitin), ergogenic aids (for example for example, protein powder/amino acids and creatine) and sports foods (for example, sports drinks and meal replacement). The most commonly used products are sports drinks and vitamin/mineral supplements, followed by creatine and protein supplements.

Vitamins and minerals

Despite their relative paucity in the diet and the body, vitamins and minerals are key regulators of health and function, including work performance. They are not direct sources of energy but facilitate energy metabolism. Water-soluble vitamins include B vitamins (thiamin, riboflavin, niacin, pyridoxine, folate, biotin, pantothenic acid, vitamin B12 and choline) and vitamin C. Fat-soluble vitamins include vitamin A, D, E, and K. Vitamin A, C and E are also antioxidants. Twelve minerals are designated essential nutrients. Magnesium, iron, zinc, copper and chromium have the potential to affect physical performance. Researchers have shown that vitamin and mineral deficiencies may result in decreased physical performance, and their supplementation improves physical performance in persons with preexisting deficiencies. For example, severe deprivation of folate and vitamin B12 result in anemia and decrease endurance work performance. Iron supplementation improves progressive fatigue resistance in iron-depleted, nonanemic women. However, the use of vitamin and mineral supplements does not appear to improve performance in people consuming adequate diets.142 Dietary supplementation in athletes at the Australian Institute of Sport for up to 8 months, including vitamins B1, B2 (riboflavin), B6, B12, C, E, A, folate and copper, magnesium, zinc, calcium, phosphorus, as well as aluminum, has not been found to improve athletic performance.

Fish oil

Fish oil, a dietary supplement, has been shown to have beneficial effects on performance. Fish oil is rich in omega-3 fatty acids, specifically docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which have been found to improve cardiac energy efficiency, fat metabolism and immunomodulatory responses. The consumption of fish oil (containing 1050 mg EPA+750 mg DHA) for 3 weeks in 20 healthy subjects has been found to decrease the body fat percentage and improve exercise performance and physiological recovery after exercise. […]

Conclusions

Muscle force production involves a sequence of events, extending from cortical excitation to motor unit activation to excitation–contraction coupling, and ultimately leading to muscle activation. Changes at any level in this pathway, including changes in the nervous, ion, vascular, and energy systems, impair force generation and contribute to the development of muscle fatigue. Metabolic factors and fatigue reactants, such as H+, lactate, Pi, ADP, ROS, HSP25 and ORM, also affect muscle fatigue. Site-specific stimulation via non-invasive techniques provides a method to gain systemic insight into the fatigue process under physiological conditions. Although there is a lack of consensus, a sex- and age-specific distribution in muscle fatigue has been observed, in which children, older adults and males are more resistant to fatigue than adults and females. Biomarkers of ATP metabolism, oxidative stress and inflammatory reactions are helpful for the diagnosis of muscle fatigue. Despite the lack of official or semi-official recommendations, muscle fatigue has been reported to be improved by some nonspecific treatments, including CNS-exciting drugs, natural products and nutritional supplements. More potential mechanisms, biomarkers, targets and related drugs for muscle fatigue— for example, ORM—still need to be explored in the future.

(All images courtesy of Wikimedia Commons)