Module 8b - Muscle Physiology

Which of the following can produce the greatest amount of force? a) concentric contraction b) eccentric contraction c) isometric contraction d) isokinetic contraction

b) eccentric contraction (muscle lengthening) During this phase, the contractile force generated by the muscles does not need to match the external resistance; the muscle is relying on its own non-contractile components to resist the lengthening effects of gravity.

At which sarcomere length is it capable of producing the greatest amount of force? a) at 100% normal resting length b) at 80% normal resting length c) at 120% normal resting length d) at 60% normal resting length

c) at 120% normal resting length A small pre-stretch of the sarcomere optimally orients the myosin and actin proteins to generate the greatest amount of force. Stretching beyond this point results in progressive reduction of force-generating capacity. Less than 100% leads to contractile protein overlap, and thus reduced force-generating capacity

Which muscle contraction results in the gradual lengthening of the sarcomere? a) Positive contraction b) Concentric contraction c) Eccentric contraction d) Isometric contraction

c) eccentric contraction Positive contraction leads to muscle shortening, and is also referred to as concentric contraction. Isometric contraction invovles tension/force generation without changing the length of the sarcomere.

Are muscles stronger in the concentric phase or the eccentric phase?

Eccentric phase Microscopic tears occur, leading to muscle protein synthesis. The tissue absorbs energy, turning it into movement during the concentric phase

True or False? As the muscle is stronger during the concentric phase, you should emphasize this more in training.

False - muscles are stronger in the eccentric phase, so this is the phase of movement that should be emphasized.

True or False: Hydration, not movement, is critical to realigning the fascial tendrils in tissue.

False. Hydration and movement are EQUALLY important in improving mobility.

True or False: If Tiffany's training program involves longer distance runs and rides, she may experience a significant shift (>20%) of her type I fibers to Type IIa fibers.

False. Longer distances mean endurance training, which results in small shift from Type II to Type I

Should you go faster or slower in the eccentric phase?

Go slower. Spend more time in the eccentric phase to get more overload in the muscle

Do isometric contractions change the length of the muscle/sarcomere? Give examples of isometric contractions used in exercise.

Isometric contractions do not change the length of the sarcomere. This is seen in holding a weight with a 90-degree elbow bend or in holding a plank position.

Why are isokinetic contractions considered safest for the joint?

It has a constant angular speed or torque

True or False? As an example, if the biceps were hypertonic, this would inhibit the triceps, forcing the lats to assume the role of synergistic dominance when performing an elbow/shoulder extension exercise.

True

True or False? A shortened muscle demonstrates hypertonicity implying that neural stimulation to that muscle increase, which in turn stimulates greater activation of that muscle.

True. Hypertonicity implies an increase in nerve activity, which will increase activation to that muscle.

Which muscle would demonstrate hypertonicity in a person who sits at their desk for prolonged periods of time with forward-rounded shoulders? a) pectoralis muscles b) erector spinae muscles c) thoracic extensor muscles d) triceps muscles

a) pectoralis muscles Forward-rounding position will shorten the pectoralis muscle groups, making them hypertonic.

Which muscle contraction results in muscle shortening? a) positive contraction b) eccentric contraction c) isometric contraction d) isokinetic contraction

a) positive contraction, a.k.a. concentric contraction Eccentric contraction involves the opposite of concentric contraction - muscle lengthening. Isometric contraction involves generating tension, but not changing the length of the sarcomere/muscle. Isokinetic contraction involves both shortening and lengthening at a constant rate or velocity.