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The Wonderful Works of Muscles: Why did my definition influence the development of exercise physiology?
Muscle movement has always been a hot topic in physiological research, especially the mechanism of muscle contraction. Since its introduction in 1954, the sliding filament theory has become an important basis for people's understanding of muscle contraction. According to this theory, the muscle's thick filament, myosin, slides past the thin filament, actin, thereby promoting muscle contraction. This theory was proposed from the independent research of two research teams, Hugh Huxley and Rolf Niedergerke. This landmark discovery not only revealed the basic operating principles of muscles, but also had a profound impact on the development of exercise physiology.
"The sliding filament theory not only changed our understanding of muscles, but also laid the theoretical foundation for this field."
Before the sliding filament theory was proposed, there were many competing theories to explain muscle contraction, including electrical attraction, protein folding, etc. The core of sliding filament theory lies in cross-bridge theory, a mechanism that describes how muscle proteins generate movement by forming cross-bridges. The theory is that when the head of myosin binds to actin, a cross-bridge is formed that promotes muscle contraction.
Early work
The history of muscle research can be traced back to the 19th century, when German scientist Willy Kühne first extracted and named myosin in 1864. Subsequent research found that myosin has the enzymatic activity of breaking down ATP to release energy, which gave people a deeper understanding of the energy source of muscles. In 1942, the discovery of Hungarian physiologist Albert Szent-Györgyi further pointed out that ATP is the energy source for muscle contraction.
"I observed myosin B-containing muscle fibers shortening in the presence of ATP. This was the most exciting moment of my life."
Over time, Szent-Györgyi, working with Brunó Ferenc Straub, eventually identified the relationship between myosin B and another protein, actin, and named it myosin. This discovery paves the way for future theories of muscle contraction.
Development of sliding filament theory
In the 1950s, Hugh Huxley began to study muscle structure in depth after receiving his PhD from Cambridge University. During the research process, he collaborated with Jean Hanson to use electron microscopy to explore the details of muscle proteins, and finally confirmed the filamentous structure of muscle proteins.
"If we assume that the stretching process of the muscle is not due to the elongation of the filaments, but to the sliding between the two sets of filaments, then the myosin-actin linkage will be inhibited."
In the May 22, 1954 issue of Nature, Huxley, Hanson, and Niedergerke simultaneously published several articles based on the sliding filament theory they studied. Although their conclusions are similar, the experimental data and assumptions differ. Huxley and Niedergerke's research believed that during muscle contraction, actin filaments enter between myosin filaments, while Huxley and Hanson paid more attention to the structural changes of the fibers.
Acceptance and influence of theory
Although the sliding filament theory encountered a lot of skepticism in its early days, it eventually gained widespread acceptance. Hugh Huxley reformulated his theory at a conference in 1972, which brought related research into a new stage. It was not until the 1980s that scientists used advanced tools to directly demonstrate the sliding motion of muscle fibers, giving the sliding filament theory a firm foothold.
"Sliding is a fact, although I cannot explain the mechanism."
Through continuous experiments and evidence accumulation, Huxley finally formally proposed the cross-bridge model in 1969. This model not only explained the muscle contraction process, but also laid the foundation for subsequent exercise physiological research. Central to this theory lies the periodic association and dissociation between actin and myosin, which is now widely accepted as the cross-bridge cycle.
Although the sliding filament theory is widely recognized in the academic community, there are still many issues that need to be explored. This theory not only had a profound impact on physiology, but also opened up new horizons for our sports science research today. So, what other layouts will be inspired by this theory for future biomedical research?
