The correct answer is Both a and b. Key Points The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. This theory was put forward by Huxley and Niedergerke in 1954. Hence the correct answer is Both a and b. Important Points The Sliding Filament Theory In 1954, scientists published two groundbreaking papers describing the molecular basis of muscle contraction. Using high-resolution microscopy, A. F. Huxley, and R. Niedergerke (1954) observed changes in the sarcomeres as muscle tissue shortened. (A sarcomere is a complicated unit of striated muscle tissue.) These observations led them to propose the sliding filament theory, which states that the sliding of actin past myosin generates muscle tension.