Muscle fatigue is defined as a temporary loss of muscle strength (muscle contraction) caused by physical activity. It is more about the disruption to muscle function, and it should not be confused with a feeling of tiredness after sport. Muscle fatigue, which is the result of medium intensity aerobic exercise, is not necessarily connected to a feeling of tiredness; it is more likely that it is expressed as a reduced ability to develop strength and performance. This acute muscle fatigue is usually at its worst immediately after exercise.
The speed and time needed for recovery, i.e. a return to original performance levels, are caused by the physiological and genetic properties of the muscle fibres with regard to physical fitness, gender and the presence of a hidden illness.
The mechanism of muscle fatigueThe production of skeletal muscle strength is dependent on the body’s contractile mechanisms. It includes a sequence of events ranging from internal impulse to activation of the muscle motor unit, to finally leading to their activation. Changes at any level of this pathway (including changes to the nervous, vascular or energy systems) disrupt the formation of strong and contribute towards the development of muscle fatigue.
Metabolic factors and fatigue reactants, such as reactive types of oxygen (ROS, free oxygen radicals), hydrogen ions, lactate, inorganic phosphate, and heat shock proteins affect muscle fatigue. Free oxygen radicals (ROS) are usually found to a lesser extent in skeletal muscle even at rest, but the amount of them increases in response to contractile activity (physical exertion). ROS products lead to the oxidation of protein, fat and nucleic acids, which are accompanied by a significant reduction in antioxidant capacity which subsequently causes muscle fatigue. Many antioxidant enzymes take part in their removal and maintain balance in the body.
If there is higher ROS production and unbalancing, i.e. oxidative stress, minor damage in the muscles as well as in other cells of the body can occur. A large amount of ROS occurs in particular with intense or long-lasting exercise. Regular training leads to adaptation of the body to the increased production of free oxygen radicals by activating antioxidant and detoxifying enzymes in the body. Maintaining the required balance in the body is also helped by antioxidants from food.
Treatment and prevention of muscle fatigueThere are currently no official recommendations for the treatment of muscle fatigue. However, some natural products and dietary supplements have shown a positive effect in alleviating or delaying the symptoms of it in pilot studies.
- Among natural products, the best have proven to be certain varieties of ginseng – particularly Asian ginseng – which can limit oxidative stress and improve mitochondrial function (like cellular power stations) in skeletal muscle. There is also Rhodiola Rosea, which demonstrably increased muscular performance capacity, and garlic, which delays the onset of muscle fatigue. Chinese yam was less effective for muscle fatigue, as were bitter orange, Ginkgo biloba, and Siberian ginseng extracts.
- Of the nutritional supplements with demonstrably positive effects on muscle fatigue, the best were iron, fish oil, creatine and carnitine. Very strong effects were also recorded with caffeine, which not only reduces muscle fatigue but also significantly increases sporting performance.
- Warning: Even if you use natural substances, you should follow the recommended dosage and usage with regard to your physical condition, age and gender; if you do not, these substances may be dangerous for the human body. We recommend consulting your general practitioner (GP).