_ ''r"'"""\\"I _ .. __._ 3. Concept Application A. During sporting activities muscles contract to do work. However, depending on the movement, the work performed may be positive or negative. There may also be instances where, despite a muscle contraction, no work is performed. Using the knee joint as a guide, describe a scenario where: - The muscles crossing the knee joint contract to do positive work: - Concentric contraction is where there is positive work done - The muscle contracts and points of attachment move in the direction of the pull - The muscles crossing the knee joint contract to do negative work: - Eccentric contraction is where negative work is done - Muscle contracts and points of attachment move in opposite direction of muscle force - The muscles crossing the knee joint contract, but no work is performed: - Isometric contraction is where there is no change, no work is performed - Muscle contracts and its points of attachment do not move relative to each other I B. We have already used pole vaulting as an example of applying biomechanics to analyze sports movement. This is a great example for applying principles of conservation of energy. If you do not remember the pole vault video we saw in class some examples from that same vaulter can be found at the following link: htmmnvyoutubeconwatchW=Jh1AFslt144g Using what you see in these videos and the principle of conservation of energy, briey discuss the following using either words or images. - Explain why the velocity of the athlete right before they leave the ground is a major determinant of the nal height they will achieve. - Explain why the manner with which the athlete interacts with the pole (bends the pole) strongly inuences the energy they get back from the pole later in the jump. C. Power output is an important metric for optimizing sports performance. There are many ways it can be manipulated. For instance: - cyclists can use a large gear and turn the pedals over very slowly or a small gear and turn the pedals over rapidly. - Rowers can use long slow strokes where they pull really hard or use quicker shorter strokes where they do not pull as hard - Runners can use a low turnover (long stride) with large propulsive forces on each contact or a very quick turnover (short stride) with lower forces on each step. Often the combination for optimizing performance is somewhere in the middle of these extremes. Pick one of the three examples above and use words or images to explain why this is so