Unit 2 Flashcards
Explain what happens to force/generation potential when that muscle/muscle fiber/sarcomere is taken out of its ideal resting position. Why?
Page 55 Think of it as a muscle. More tension is generated. The ability to generate tension decreases. To remove from resting period is to lengthen or shorten the muscle. The muscle is weakest at its extremes of ROM. When the muscle is really short, there are few crossbridges. When the muscle is really long, there is no crossbridging between actin and myosin.
Explain how tension is created in muscle that is lengthening passively.
- Highest tension. Non-contractile elements are stretched to where they cannot be lengthened anymore.
Epimysium, around muscle. Parimesium, full length. Endomesium…
Connective Tissue…generate tension.
!!!Muscle can generate tension even when it cannot create contractile force.!!!!
How do elasticity and viscosity relate to passive-length tension curve in a muscle?
Elasticity–Tension does not begin until slack is gone. Once tension disappears, the tissue rebounds.
Viscosity–property of material…fluid or liquid…where changes of shape is not immediate. Internal resistance to flow of fluid or material. Properties of a fluid or liquid where it does not change its shape immediately. Time dependent. Tension is generated by the liquid resisting change–especially if done quickly.
Describe a muscle that can produce its greatest force.i.e. What is its length? What does its actin/myosin filament alignment look like?
When the optimum** number of actin/myosin crossbridges are occuring. Generally in the resting mid-range length, but different for each muscle.
What happens when grip strength testing occurs at different length of grip? Where is the strength the strongest?
Starts low, ends somewhat low, peaks in the middle. Optimum crossbridges are at #2. Typically 2 and 3 are the largest value.
According to the Total Length Tension Curve, when are active vs passive tension components contributing to the total force generation of the muscle using muscle length?
The graph represents an eccentric contraction. Only isolated active muscle tension occurs before resting length. Isolated Passive tension only occurs at the extreme long end of ROM. In between, the two forces sum together to generate tension. Non-contractile forces contribute to total muscle force. Which produces a greater contractile force? Concentric or Eccentric? Possibly eccentric.
Discuss what the bell shape of the bicep internal torque-joint angle curve indicates about a muscle or muscle group’s length (physiological) and moment arm as factors in producing force.
Bicep curve. It shows what muscle length and moment arm length coincide together to create the greatest force….(resting length of bicep is a little less than 90degrees. More like 65.) Muscle arm began short, lengthened, and possibly shortened again. Fig 3-13. Bicep moment arm is longest at 90, but the torque would be less due to physiology of the muscle. The muscle shortens and loses torque after 65 faster than the moment arm can make it up? Therefore, the relationship is paramount between torque and moment arm.
Discuss what the negative slope of the hip abdcutor’s internal torque-joint angle curve indicate about the muscle or muscle group’s length (physiological) and moment arm as factors in producing force.
Hip abductors. The shorter the muscle length, the less torque produced, or longer muscle, greater torque. In this muscle group, muscle length is more important than moment arm because the moment arm does not change throughout this range of motion.
What is the effect of muscle force production from an increased moment arm for the hip abductors
Muscle torque would increase because of the moments arm’s increased length. How does the moment arm for the hip lengthen or shorten? It can. Pg 505 Coxa vara and coxa valga. It all has to do with the relationship in the angle of the pelvis, head and neck of femur, and femur. …Sometimes the muscle length and moment arm,and sometimes the muscle length is the primary factor in producing a torque. If the hip continued to adduct, the slope would eventually begin to decline in order to create the bell curve similar to the bicep curve.
What is the effect on grip strength with the wrist in flexion? extension?
Finger flexors shorten as the wrist is flexed. 41lb. Grip strength decreased at flexion. 45 lb. at Extension. Did not have the optimum actin myosin crossbridges for both. too long and too short.
What is the relationship between muscle load and maximum contraction velocity for concentric contractions of a muscle?
If the load is really low, the velocity of contration will be very fast. If the load is really heavy and can’t be moved, the velocity will be 0 (isometric). If the load is really heavy and can be moved, the speed of shortening will be very slow.
How do internal torque-joint angle curve shapes relate to functional activities?
Greatest external torque needs to be countered by greatest internal torque. Where the physiological and moment arm factor have to work together, works to our advantage. We need these joints to be their strongest in the range where we need them for everyday activities and loads. Good design.
In reviewing the theoretic force-velocity curve, what does the graph indicate for the torque of a high speed concentric muscle contraction?
High speed = Low force/Load
In reviewing the theoretic force-velocity curve, what does the graph indicate for the torque of a high speed eccentric muscle contraction?
High speed = High force/Load
What does one interpret about muscle accelerator and decelerator functions a force-velocity curve?
Concentric contractions at low load have acceleration properties. and Eccentric contractions have a deceleration property.
