Muscle Fatigue: Why do muscles get tired and weak after exercise?

What causes muscle fatigue, muscle tiredness and muscle weakness after a work out? Why do our muscles get fatigued, tired, weak, sore, burn and hurt after exercise? What causes our muscles to fatigue to the point where there is a physiological inability to contract, and why does it take time to recover from muscle fatigue?

Our Muscles get weak, tired and fatigued after use, but the reason for this is unclear. This video gives the reasons and three main hypotheses as to why we get muscle weakness and fatigue after use / workout / exercise, and explains the underlying physiology. This includes the impacts on Excitation-Contraction Coupling, Lactic Acid and wastes, the biochemistry, and energy causes. A better understanding of why our muscles get tired after a workout or exercise can also help you understand what's required in order to obtain an effective recovery.