ADVANCED BIOMECHANICS - KINES 484 Spring Semester, 2002 Summary of Review Questions INTRODUCTION TO AREA OF STUDY (Topics 1-2) Topic 1 - What is biomechanics? 1. What are biomechanical investigations concerned with? 2. Outline the contribution of one researcher to the history of biomechanics. Topic 2 - The Scientific Method 1. Outline the sequence of events, which describes the scientific method. 2. How is support for a theory developed? 3. Outline some of the potential roles of ligaments in human movement. WHAT ARE RELEVANT MECHANICS? (Topics 3-6) Topic 3 - Basic Mechanics I 1. Give the units for Linear displacement Angular displacement Linear velocity Angular velocity Linear acceleration Angular acceleration 2. What is a rigid body? 3. What do we mean by mechanical degrees of freedom? 4. How many coordinates are required to describe the location of A) a point in two-dimensional space B) a ball in three-dimensional space Topic 4 - Basic Mechanics II 1. State Newton s three laws. 2. What is the difference between mass and weight? What are their respective units? 3. What is the source of the ground reaction force? 4. What is drag? What factors influence the drag experienced by an object? Topic 5 - Work/ Energy/ Power 1. For the human body list the fractional sources of energy, which account for the total work done. 2. Strain energy can be useful to human movement, list possible sites of storage of this energy. 3. What are the problems when trying to compute the efficiency of human movement? 4. Using a work-energy approach compute for a 60 kg gymnast who jumps from the ground 1 m high! their maximum potential energy
! their initial vertical take-off velocity! their landing velocity (Assume the acceleration due to gravity is 10 m.s -2.) Topic 6 - Allometric And Geometric Scaling 1. For an object, which scales geometrically state the relationships between length, area and mass. 2. A father who is 1.80 m tall and weighs 80 kg has a young son who is a perfect isometric scale of the father. If the son is 1.20 m tall how much does he weigh? 3. What uses could geometric scaling be when comparing athletic performance? HOW WE MEASURE (Topics 8-10) Topic 8 - Force Measurements 1. State the sampling theorem. 2. Explain what happens if a signal is not sampled at a sufficiently high sample rate. 3. What is the source of the ground reaction force? 4. What are the problems when using a force plate? 5. What applications can be force plates be used for? 6. Sketch the vertical ground reaction force you would obtain for vertical jumping and for a foot making contact with the ground during either walking or running. Topic 9 - Motion Analysis 1. What is measurement noise? How can it be reduced in sampled data? 2. What geometric shapes can be used for the modeling of human body segments? What are the relative merits of the different geometric solid models of the human body? 3. What other methods are available for determining body segment inertial parameters? 4. Leonardo da Vinci (1452-1519) wrote It is impossible for any memory to preserve all the aspects and changes of the parts of the body. How do modern motion analysis systems seek to circumvent this problem? Topic 10 - Combining Measurement and Error Propagation 1. Define accuracy, precision, and resolution. How might you numerically quantify accuracy, precision, and resolution? 2. If trying to compute derivatives from displacement data what measures should be taken to ensure these estimates are as accurate as possible? 3. What do we mean by error propogation? Why is it important to consider the influence of error propogation when analyzing human movement? 4. What do we mean by spatial temporal resolution?
RESULTANT JOINT MOMENTS (Topics 12-16) Topic 12 - Computation of Resultant Joint Moments 1. Write the equation which describe the relationship between all the forces applied to a segment and the acceleration of that segments center of mass. 2. Write the equation, which describes the relationship between all the moments applied to a segment and the angular acceleration of that segment about its center of mass. 3. The resultant joint moment is a result of a number of different forces applied to a segment, what are these forces? 4. Define a parameter and variable, then list the parameters and variables required to compute a resultant joint moment. How can these parameters and variables be computed? Topic 13 - Resultant Joint Moments: What do they mean? 1. What assumptions are made so that the resultant joint moment can be considered to be the muscle moment? List some situations under which these assumptions may not be valid. 2. What is meant when the musculo-skeletal system is said to be redundant? 3. What is co-contraction? When might a co-contraction be advantageous? 4. What is the convention for the direction of a moment to be positive? Draw a simple limb with two joints, on one joint mark the direction of flexion and the sign of the moment required to produce it, for the other joint mark the direction of extension and the sign of the moment needed to produce it. (Assume the moments do not occur simultaneously.) Topic 14 - Muscle Forces - Electromyography 1. List the measures to consider when collecting data using an EMG system. 2. What is the theoretical relationship between EMG activity and muscle force? What is obtained in actuality? 3. What is electromechanical delay? What implications does this have for human movement? 4. How does the EMG signal change with fatigue? Why is this? Topic 15 - Muscle Forces - Optimization 1. What is meant by optimization? 2. Write an objective function, equality constraint(s), and inequality constraint(s), which could be used to estimate muscle forces. 3. What options are available for validating optimization based routines for estimating muscle forces? 4. Suggest three objective functions which could be used in estimating muscle forces. 5. What is the difference between static and dynamic optimization? Topic 16 - Degrees of Freedom Problem 1. Describe the various levels of Bernstein s degrees of freedom problem. 2. Give an example for each level of how we control the freedom. 3. What is Henneman s size principle? 4. What feasible ways are there of controlling all of these degrees of freedom for human movement?
MUSCLES (Topics 18-21) Topic 18 Basic Properties of Muscles 1. Explain the source of the maximum isometric force a muscle can produce. 2. What is the shape of the force-length relationship of isolated muscle fibers? What is this caused by? 3. What is the shape of the force-velocity relationship of isolated muscle fibers? What is this caused by? 4. What are the nature of the time delays due to muscle activation? What is the significance of these delays? 5. What are the key properties of tendon? 6. What are isometric, isokinetic, and isotonic contractions? How is it possible to produce an isometric contraction? Topic 19 - Architecture Influences 1. Describe what is meant by the term physiological cross-sectional area. 2. Explain how the moment arm of a muscle influences the moment at the joint and the motion of the joint it crosses. 3. Describe muscle pennation. 4. How can the moment arm of a muscle be computed? 5. Imagine two muscles Muscle A consists of three sarcomeres in series Muscle B consists of three sarcomeres in parallel Rank the two muscles on the following properties Contraction Time Maximum Force Range of Motion Maximum Velocity Maximum Power (Your answer should be in the form Energy Use Muscle A < Muscle B) Topic 20 - SEC Influences 1. What is meant by the term SEC? What are the potential sites of SEC in human muscle? 2. Explain how you can deduce the relative role of tendon and muscle fibers in the stretch shortening cycle. 3. How might tendon make stretch shortening activities more efficient? 4. Give four examples of the stretch shortening cycle in human movement. 5. What implications does the SEC have for the control of human movement? Topic 21- What happens in vivo? 1. Roberts et al. (1997) in their study of running turkeys described the role of the muscle fibers being to work as rigid struts. Explain what they mean by this and what the implications are of such a mechanism. 2. What does it mean if the SEC is said to be tuned to the nature of the activity? Consider the analysis of Morgan et al. (1978) of kangaroo hopping. 3. Lutz and Rome (1994) examined the mechanics of frog muscle during jumping. Describe their findings. 4. The study of Amis et al. (1987) described an aspect of muscle tendon function in man. What did they describe and what implications does it have for movement in man?
5. Gregor et al. (1991) measured the force transmitted via the Achilles tendon in cycling. What mechanisms of muscle function could be investigated given such analyses in man.