Lecture 32 - Physical Activity II Flashcards
Muscle Spindle
Monitor length or change in length in a muscle (eg. stretch). It does this by eliciting a muscle contraction to protect the muscle from damage caused by a rapid stretch
What is the pathway of sensory-motor integration
1) Muscle fiber stretch
2) Stretch of muscle spindle in central region
3) Extent/quickness of stretch sent to the spinal cord via primary afferent (Ia) pathway
4) Afferent neuron synapses with alpha motor and adds excitatory stimuli to alpha motor neuron that summates with voluntary stimulus for movement that comes from higher centers of brain
5) At the same time a branch of the sensory neuron stimulates an inhibitory neuron that innervates the alpha motor neuron of the antagonist muscle group (reciprocal inhibition)
GTO
Produce an inhibitory reflex action in the muscles
What is the process of how a GTO works
1) Detect changes in tension in single muscle fiber
2) Primary (Ib) afferent sensory endings are used to act on agonists to inhibit motor unit recruitment
3) This results in decreased force production (autogenic inhibition)
Joint Receptors
Transmit sensory information relating to positions, velocities, and accelerations that occur at the joints
What are the 3 characteristics of Type I fibers
What are the 4 characteristics of Type IIa fibers
What are the 3 characteristics of Type IIx fibers
What are the 6 muscle fiber types and their endurance and force rating
T or F: Muscle fibers do not transition
F, they do transition although proportions of muscle fibers are genetically determined
Pattern of muscle stimulation leads to
specific intramuscular signaling
What are the most observed fiber-type transitions
Type IIX and IIA from resistance, sprint, plyometric and endurance training
Muscle Contraction
When the muscle is producing tension within the fibers of the motor units recruited
What are 4 influencing factors on muscle contraction
1) Muscle action
2) Length-tension relationship
3) Force-velocity relationship
4) Stretch-shortening cycle
Muscle changes depend on concentric, eccentric, and isometric muscle contraction, but which is responsible for greater gains in muscle size
Eccentric muscle contractions (should be emphasized in training
Describe the 3 core principles’ of the length-tension relationship
1) there is an optimal length for the greatest amount of force that a muscle fiber can produce.
2) The relationship between the length of the fiber and force production is a function of the overlap between the thick and thin filaments of the sarcomeres during muscle contraction
3) For greatest force production, the length of the fiber should allow the greatest amount of cross-bridge attachment to take place
Explain the concentric muscle action of the force-velocity relationship
Inability of the cross-bridge cycle to keep with the shortening sarcomere resulting in slower shortening velocities which allow for greater number of cross-bridge attachments meaning that a maximal force is produced at slowest shortening speeds
T or F: There is an inverse relationship between force produced and velocity of shortening
T
As velocity of contraction or shortening of the muscle [increases/decreases], the ability of the muscle to produce force greatly [increases/decreases]
decreases, increases
Describe the force-velocity relationship in terms of isometric contractions
Isometric contractions produce greater forces than concentric actions because zero velocity allows adequate time for cross-bridge cycling to take place
Describe the force-velocity relationship in terms of eccentric contractions
1) Eccentric contractions exceeds isometric contractions by 50-100%
2) Greater force must be applied to the muscle to detach the cross-bridges during the lengthening of the sarcomere
Image of actin and myosin in relaxed, partially contracted, and fully contracted state
Describe the stretch-shortening cycle
Muscle functions by repeatedly stretching (eccentric) followed closely by shortening (concentric)
What mechanisms and activities are involved in the stretch-shortening cycle
Mechanisms: Neuromuscular pre-activation, stretch-reflex contributions, and recoil of elastic energy stored in tendons
Activities: Walking, running, hopping and jumping
Neuromuscular Fatigue
It is a prominent factor in declining performance capabilities during exercise because there is a reduction in the ability of the muscle to maintain force or power
What are the 3 causes of neuromuscular fatigue (chemically)
1) Lack of blood glucose (hypoglycemia): Disturbs muscle function and motor output of cerebral cortex
2) Release of ammonia by active muscle: Alters cerebral blood flow, energy metabolism, synaptic transition, and regulation of neurotransmitters
3) Conscious perception: Sense of effort (person’s subjective judgment of the intensity of the outgoing motor command associated with performing a submaximal contraction)
Described delayed-onset muscle soreness cause and time duration
Cause: Tissue injury from excessive mechanical force (mainly eccentric) on muscle and connective tissue
Duration: Appears 24-48 hours and peaks 2 and 3 days after strenuous exercise. Subsides 1-2 days after peak soreness
What are 2 key factors to change contractile strength
1) Muscle size
2) Neural properties
Muscle fibers with the greatest surface area produce
the most force
T or F: You can increase strength without noticeable increase in cross-sectional area
T
Initial gains in muscular strength without the increase in cross-sectional area (rehab feature) are related to
Neural adapations
When does connective tissue adapt
When progressively overloaded by increased stress
Mechanical stress is defined by
Internal force observed/cross sectional area of the connective tissue structure
T or F: Greater mechanical stress placed on connective tissue when cross sectional area increases per level of force encountered
F less mechanical force
What 2 ways allow connective tissue to increase tolerance for loading?
1) Increase size
2) Alter structural properties
What are the 3 types of mechanical stress and describe them
Which type of stress is more injurious athletically
Depends on the sport (but mainly shear)
Stress
Level of force encountered by a tissue
Strain
Magnitude of deformation that takes place in proportion to the amount of stress applied
Linear Strain
Results from compressive and tensile stresses. Tissues (tendon, ligaments) change length and expressed as a percentage relative to resting length
Shear Strain
Results in the bending of tissues (bone) and quantified by the angle of deformation
Where do you find connective tissue stiffness on the stress-strain relationship
Slope of the line in the linear region
Stiffness
Resistance to a change in length, force transmitted per unit of strain
Stiffness is directly related to
The connective tissue structure -> cross-sectional area, collage, and ECM protein composition (glycosaminoglycan and proteoglycan content)
Compare the stress-strain relationship of bones, tendons, ligaments, and cartilage
What is the property that allows connective tissue to return to its original length after being strecthed
Elasticity
What is the term for chronic stretching to a tissue that can cause transient or permanent deformation where the tissue remains at least partially elongated and does not return entirely to its original length
Plasticity
T or F: Plasticity can be an advantage or disadvantage
T
Describe tendon adaptations based on regions
Regional difference within the same tendon occur where the region closest to the bone is much stiffer than myotendinous junction (where tendon collagen fiber are woven with skeletal muscle fibers)
High tension, slow velocity injury regards what part of the tendon
Bone-tendon junction
High-tension, fast-velocity injuries regard what part of the tendon
the tendon belly
Describe the 3 tendon responses to mechanical loading
1) Resting state
2) Mechanical loading
3) GF-receptor interaction increase collagen synthesis
Describe the 3 affects of acute exercise on tendon adaptation
1) Initially results in collage degradation, but increases significantly in subsequent days
2) Increased [metalloproteinases] which can aid in repairing damage collagen and ECM remodeling following exercise
4) Training intially increases type I collagen turnover while prolonged training increases tendon cross-sectional area
Describe the 5 affects of resistance training on tendon adaptation
- Tendon stiffness increases
2) Collagen cross-linking increases increasing tendon strength initially
3) Heavy loads = increased tendon stiffness (light load do not)
4) Resistance training >70% MVC is sufficient to increase tendon stiffness and cross-sectional area
5) Regional adaptations within tendon take place in response to overload with respect to ECM and cross-sectional area components
Describe the schematic representation of the mechanostat point for tendons (tendon adaptation)
Describe the schematic representation of re-calibration of the mechanostat point for tendons following stress deprivation or overload (tendon adaptation)
How many hours of mechanical loading can reduce articular cartilage thickness by up to 57% with 1/3 of the deformation taking place during the first 8 minutes
4 hours
T or F: Cartilage deformation naturally occurs during most types of exercises
T
What are 3 biomarkers and their function for cartilage adaptions
- Cartilage Oligomeric Matrix Protein (COMP) and Lubricin: Lower body resistance exercise returning to baseline 30-mins after intense running, cycling, walking, and vertical drop landings
- Hyaluronan: Increases with rising intensity and stabilizes the matrix
Regular exercise can aid with what 3 aspects of knee cartilage
1) Preserve knee cartilage volume and thickness
2) Increase proteoglycan content
3) Reduce cartilage defects
Training can help in what ways for cartilage adaptations
- Maintain cartilage thickness and prevent age/hypoactivity declines
- Improve joint stability and load absorption by structurally changing articular surfaces
- Reduce cartilage degradation
What 3 causes can result in joint degradation
- Joint injuries
- Excess mechanical stress
- Highly repetitive intense exercise on injured or improperly healed joints
What are 6 causes that result in cartilage adaptation
- Abnormal joint anatomy
- Previous joint injury/surgery
- Joint instability
- Heavy bodyweight
- Inadequate muscle strength
- Altered muscle innervation
What is the best way to safeguard cartilage from age-related degeneration
Moderate-to-vigorous exercise
Long-term training increases bone _____ and ______.
Bone mass and strength
T or F: Stress must reach a certain level for bones to adapt
T
Minimal Essential Strain
Minimal threshold stimulus (volume and intensity) that is needed to form new bone
What needs to be sufficient intensity and volume to elicit increases in bone mass, bone mineral content, and bone mineral density
Exercise
What is the key t increasing bone strength
Dynamic, high-intensity loading
T or F: Weight bearing exercises are less effective than non-weight bearing for increasing bone mineral density
F, they are more effective
Compare a humerus cross-section between a humerus for a playing arm of a nonplaying arm and a professional tennis player arm
Bone turnover (remodeling) increases in
states of disuse (left image) and overuse (right image)
How long does it take to see an improvement in joint ROM following flexibility training
Immediate improvement and chronic change after 3-4 weeks of regular stretching 2-3x a week
List 2 outcomes of flexibility training
1) improve postural stability and balance
2) Minimizes mobility deficits experienced with aging
What are 4 types of flexibility training
- Ballistic methods or bouncing stretches
- Dynamic or slow movement stretching
- Static stretching (active or passive)
- Proprioceptive Neuromuscular Facilitation (PNF)
What types of stretching are most effective with warm muscles and should not be performed prior to exercise?
Static, ballistic or PNF
Active Stretching (static)
Holding the stretched position using the strength of the agonist muscle (common in yoga)
Dynamic stretching
Gradual transition from one body position to another and a progressive increase reach and ROM as movement is repeated several times
What are 4 characteristics of dynamic stretching
- Elevates core temp (increase muscular conduct and compliance)
2) Short sessions (<30s) does not affect performance
3) Prolonged sessions (>30s) can facilitate performance
4) Recommended before vigorous exercise and adjunct to higher sports performance
Flexibility recommendation in accordance to FITT
How many seconds should discontinuous flexibility exercise occur per joint
90s
What is the difference in time of stretch for younger vs older adults
Younger: 10-30s to point of tightness/discomfort
Older: Hold stretch for 30-60 s
What does increasing volume during stretching (time/reps/frequency) improve
ROM in regards to static and PNF stretching
When should you include static stretching in pre-event warm-up
When combined with aerobic activities, dynamic stretching and dynamic sport
Stretching routine according to FITT should be completed in
<10 minutes
T or F: Negative psychological effects occur with added static stretching to a full dynamic warm-up
F, positive psychological affects
Achilles tendon loading example
Describe the average achilles tendon stress during heel-raising and lowering exercises
Describe the average ankle ROM during heal-raising and lowering exercise
Key points from the achilles tendon loading example
PF - plantar flexion
DF - Dorsiflexion
B - Bilateral
U- Unilateral
AT - Achilles Tendon
Describe how resistance training aids in bone adaption to exercise
Describe how jump training aids in bone adaption to exercise
Describe different exercise outcomes and their findings in related to bone adaptation from jump and resistant training
