To understand what causes muscle fatigue, it’s worth looking at what exactly muscle fatigue is. If you exercise regularly, you may be accustomed to feeling a dull ache in your muscles or feel a feeling of fatigue or lack of energy that makes it difficult to perform your usual daily tasks. But it’s not just exercise that can cause muscle fatigue, several health conditions also cite muscle fatigue as a common symptom.
A study in the Journal of Physiology defines muscle fatigue as a transient or temporary decrease in the ability to perform physical actions. More specifically, “muscle fatigue” describes any reduction in the force or power that muscles can produce, which develops soon after physical activity begins.
You will surely have experienced this in your own life – whether in a reduction in your running speed, your strength when lifting weights, or simply in the fact that you find it harder to maintain the same level. performance. Not only can it be frustrating to struggle to maintain a given level of performance, but a fatigue-induced decrease in performance can lead to poorer adaptations to training, as a study from the International Journal of Sports Physiology and Performance.
In order to get the most out of your training, let’s see how best to prevent muscle fatigue. There are a handful of options (some simpler than others), from training at sub-maximal intensities to simply drinking more water. In that case, you’ll want to check out our guide to best water bottles.
What is muscle fatigue?
As mentioned before, muscle fatigue is a decrease in the force or power that the muscles involved in a given task can produce. In real terms, this manifests as the ability to lift less weight or do fewer reps, not running/cycling as fast or for as long, or the same performance feeling more difficult.
For muscle fatigue, we only consider performance reductions for the same muscles, and mostly within the same workout, or workouts in close proximity to each other; for example, being able to perform fewer reps on the bench press when doing more sets, or having more difficulty maintaining a given pace during a 5k run or races on subsequent days.
Fatigue induced over a longer period or with different muscle groups is more likely to be a feeling of systemic, central nervous system oriented fatigue, as illustrated by research on caffeine in the American Journal of Physiology.
The causes of muscle fatigue
Before we start discussing the causes of muscle fatigue, we must first understand what allows muscles to contract and work. At the most basic level, muscle contracts by individual fibers (called actin and myosin) sliding past each other and forming cross-bridges. A chemical called adenosine triphosphate (ATP) is key to allowing this to happen, and can be thought of as muscle currency – the more you have, the harder your muscles can work, as shown in Advances in Biophysics and Molecular Biology. Phosphocreatine (PCr for short) is a high-energy chemical that acts as a storehouse of phosphates to create more ATP, as shown in Muscle physiology.
One of the reasons ATP is so important is that it enables the release of calcium inside muscle cells to allow contractions to take place, and an important by-product of the creation of ATP is an accumulation of hydrogen ions, as shown in Talanta. Hydrogen ions induce fatigue by creating a more acidic environment in the muscle.
According to research results published in Sports medicine and Clinical and experimental pharmacology and physiology, muscular work can cause decreases in ATP and PCr and an accumulation of Hydrogen ions and Magnesium ions, which inhibit the release of calcium. These effects can impede cross-bridging and calcium release, leading to decreased muscle force production.
The increase in heat felt by the body during exercise is an important factor that causes muscle fatigue. Exercise-induced heat can cause physiological strain, as noted above, according to a 2015 study in Scandinavian Journal of Medicine and Science in Sportand can also lead to dehydration through sweating as the body attempts to maintain a constant, safe temperature.
Dehydration is one of the main contributors to fatigue according to a 2011 article in the Sports Science Journaland sweating can lead to significant losses of essential minerals such as sodium, magnesium and calcium, which can lead to greater muscle fatigue.
How to prevent muscle fatigue
Now that we know what causes muscle fatigue on a cellular and more general level, there are well-established practical steps we can take to help reduce muscle fatigue. First, eating carbs within a few hours of exercise can dramatically improve exercise performance, largely because carbs play a vital role in glycolysis, a primary pathway for ATP production.
Second, there are a number of tactics you can use post-workout to reduce fatigue felt during a workout. A 2018 study in Frontiers in Physiology found that immersion in water at any temperature below body temperature was very effective in reducing fatigue and muscle soreness after training.
Finally, a 2019 search in the Journal of Strength and Conditioning Research found that cooling down strategies were one of the most effective ways to maintain performance during a workout, in other words, preventing too high a core temperature helps prevent fatigue. A very effective way to help maintain a relatively low temperature is to drink cold water, an issue investigated in a 2015 meta-analysis in the Scandinavian Journal of Medicine and Science in Sportand 10 of the 14 studies compiled showed a reduction in body temperature when drinking cold water.
Points to remember and practical steps
Some degree of muscle fatigue is inevitable when exercising, as you can see now. However, there are some practical steps we can take to reduce the effect, now that we know what causes muscle fatigue. Eating carbs before training can help maintain muscle performance, and immersion in water below body temperature can also help.
Most people already drink water when exercising, but making sure it’s cold will have a big effect on protecting against muscle fatigue and helping you get the most out of your workouts. .
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