- Calculator (1)
- Tape measure (1)
- Skin pencil (1)
- Text (1 copy of each)
- Kendall, F.P., McCreary, E.K., & Provance, P.G. (1993). Muscles: Testing and Function (4th ed.). Baltimore: Williams & Wilkins.
- Smith, L.K., Weiss, E.L. & Lehmkuhl, L.D. (1996). Brunnstrom's Clinical Kinesiology (5th ed.). Philadelphia: F.A. Davis.
Sections that relate to the week's lecture material on muscle anatomy and function include pages 69-75, 87-90, and 126-129. Pages 76-87, while optional, are a helpful review of material you learned in human physiology. Revisiting the sections that relate to using vectors to visualize forces, pages 20-27 and 53-63, will help you with this week's lab problems.
Pages 266-279 introduce you to the hip joint. Just as with the material that relates to the knee, you will likely read this material several times over the next few weeks.
- Anatomy text of your choice
- transparencies and erasable markers provided by lab instructors
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Reexamine the procedure for a resistive test of the medial hamstrings (Kendall, McCreary, & Provance, 1993, p.208), for which you constructed a vector diagram during last week's lab. Add the following information to your diagram.
- Use published anthropometric data (Smith, Weiss, & Lehmkuhl, 1995, p.55) to estimate gravity's force on the moving segment, that is, the moving segment's weight.
- Assume that the examiner applies a force of 5 pounds.
- Estimate the location of the knee joint's lateral axis (Smith, Weiss, & Lehmkuhl, 1996, Fig. 9-3, p. 305).
- Draw and estimate the length of the moment arm for each of your diagram's three force vectors. You may use a tape measure on a member of your lab group as he or she assumes the test position, or you may examine a laboratory skeleton.
After determining the magnitude (in pounds) of gravity's force on the moving segment, and the force's moment arm (in inches) with respect to the knee joint's lateral axis, calculate the moment that gravity's force produces around the knee joint's lateral axis. Do the same for the force that the examiner produces. Verify that both forces produce knee extensor moments. Calculate the magnitude of each moment (in inch-pounds). Because both moments are in the same direction (extension), you may add them to arrive at a "net" extensor moment.
Finally, use the equation for rotational equilibrium to estimate the force that the muscle produces during the resistive test. Assume that the semitendinosus is the only muscle active during the test.
- Repeat the process that you practiced in the previous problem by analyzing a resistive test of the gluteus maximus (Kendall, McCreary, & Provance, 1993, p.226). Trace or redraw the figure and use it to perform a vector analysis in the sagittal plane. Draw separate vectors to represent the three forces applied to the moving segment by (1) gravity, (2) the gluteus maximus, and (3) the examiner's resistance. Estimate forces and moment arms by using published anthropometric data (Smith, Weiss, & Lehmkuhl, 1995, p.55), laboratory skeletons, tape measures, and other tools. Assume that the examiner applies a force of 5 pounds at the posterior thigh.
After determining their magnitudes (in pounds) and moment arms (in inches), calculate the moments (in inch*pounds) that the forces of gravity and of the examiner produce around the hip joint's lateral axis. Verify that both forces produce hip flexor moments, and calculate the magnitude of the two moments.
Examine a laboratory skeleton to estimate the muscle's moment arm. Finally, use the equation for rotational equilibrium to estimate the force that the muscle produces during the resistive test. Assume that the gluteus maximus is the only muscle active during the test.
- Gain further practice in vector analysis by examining a closed-chain activity. Diagram the effects of gravity and muscles, in the sagittal plane, as one of your lab partners sits on a surface like a chair or a bedside commode. Focus on one ankle (talocrural) joint.
- Use your diagram to predict whether gravity produces ankle dorsiflexion or plantar flexion as the person sits.
Hint: Your lab partner can maintain stability while he or she sits only if the center of gravity's location is over the base of support. The person is most stable when the center of gravity lies over the center of the base of support. - Predict what muscles are active.
- Choose one of the muscles, and diagram its force, taking care to depict its point of application on the appropriate segment in this closed-chain activity.
- Use your diagram to predict whether gravity produces ankle dorsiflexion or plantar flexion as the person sits.
- Repeat the sagittal plane analysis of sitting with respect to the knee joint's lateral axis.
An additional problem to help you develop your skills in analyzing human motion: - For either of the analyses of sitting that you performed for the ankle or knee, find the point in the range of motion where the muscle must produce the largest 's force is the greatest. Use the idea of rotational equilibrium to estimate the the muscle's force at that point in the range of motion.
How would the force requirements on this muscle change if your lab partner sat on an elevated surface, like a four-inch cushion or a raised toilet seat.