## Problems

Problem 1.1. Consult an anatomy book to identify the primary functions of muscles and other anatomical structures of the shoulder, arm, forearm, thigh, and leg. Problem 1.2. Build a model of a spinal column using a nylon string, beads, rubber bands, and corks. How does the bead shape affect the curvature of the model spine? Is it possible to construct a column using beads of spherical shape? Note that the rubber bands, if they were to simulate muscles, would have to be prestretched before being hooked onto the beads.

Problem 1.3. The primary component of the shoulder girdle, the scapula, is not connected to any bone in the human body but it is positioned by a number of muscles acting on it. Take a piece of cardboard or styrofoam and position it in space by using hooks and strings. How many different strings do you need to fix the position of an object in space? Could you fix the object in space by attaching all the strings to the same point? Note that the position of a point in space can be defined by specifying its three coordinates. The spatial configuration of a solid body can be specified in terms of three space coordinates of any one particle of the body and the three angles that determine the orientation of the body in space. Thus, a solid body that is free to move in space is said to have six degrees of freedom.

Problem 1.4. Consult an anatomy book to reason why the upper arm and thigh contain a single bone each (humerus and femur) whereas the forearm and the leg have two bones: radius and ulna of the forearm, and tibia and fibula of the leg, respectively.

Problem 1.5. Consult an anatomy book to explain the functions of various neck muscles.

Problem 1.6. Think of analogies between human body structures and suspension bridge cables, beams, columns, domes, arches, styrofoam packing material, heel cups prescribed by orthopaedists, tent sheets, and corsets.

Problem 1.7. Suppose a parallel muscle of the arm such as the biceps weighs 4 kg and the total length of the muscle-tendon complex is 32 cm. Explain how the muscle force and the extent of shortening depend on the length of tendon. Note that the longer is the tendon, the shorter is the muscle and the bulkier it is at the midsection. Assume that the maximum tension exerted by the biceps is proportional to the maximum diameter of this muscle in the resting state.

Problem 1.8. Search the anatomy literature for a discussion of the types of synovial joints. Provide definitions for plane (gliding), condyloid, and saddle joints, and cite examples.

Problem 1.9. Summarize the mechanism of the sliding filament theory of muscle contraction. What are the basic data supporting this theory? Why haven't researchers been able to obtain photomicrographs of cross-bridges pulling on actin filaments at sequential instances of time? Summarize Hill's force-velocity relation of skeletal muscle. Why is this relation called phenomenological?

Problem 1.10. Why is the sole of the foot covered by a thick fatty connective tissue (pad)? Which bones are subjected to the greatest impact force during running?

Problem 1.11. Identify biarticular muscles of the leg. Speculate what roles they would play during vertical jumping.

Problem 1.12. Which muscle group of the upper arm do we use to get out of a armchair?

Problem 1.13. When a muscle shortens while producing movement, it is said to contract concentrically. If the muscle extends while contracting, it is contracting eccentrically. Determine which phase of the push-ups (upward phase or downward phase) the triceps contract concentrically.

Problem 1.14. Which biarticular muscle group of the thigh controls the lowering forward of the trunk?

Problem 1.15. A tendon can withstand tensile forces of 10,000 N/cm2 of cross-sectional area without tearing. The tendon is thicker than it needs to be to transmit muscle force to the bone. Why do tendons grow so thick? In his book entitled The Human Machine, R. McNeill Alexander attributes this to the elastic properties of the tendon and uses the analogy of bicycle brakes. If the cables that work the bicycle brakes were made of rubber rather than steel wire, one would have to move the brake levers a long way before stopping, resulting in longer braking times. Discuss this topic within the context of the tendons of the hand muscles and playing piano.

## Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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