APK 3110C Lecture Notes - Lecture 11: Motor Neuron, Myocyte, Myoglobin
APK 3110
Week 11
Chapter 22 Part 2: Muscle Strength
Factors regulating muscle mass
• Genetics
• Nervous system activation
• Environmental factors
• Endocrine influences
• Physical activity
• Nutritional status
Physical activity and nutritional status are the main two factors that you can control that
regulates muscle mass
Training Sensitive factors
• Strength increases the most and eventually levels off unless you’re using steroids
• Hypertrophy increases but not as much as strength and eventually levels off unless using
steroids as well
• Neural increases and then levels off once the neurons get used to the reps
• As you gain your neural aspect decreases and you get an increase in muscle size
Neurological Arousal/Mental Aspect of Performance
• Theory:
o We usually aren’t able to reach maximal strength capacity
▪ Strength capacity is based on muscle CSA, fiber type and mechanical
arrangement of bone and muscle
o But, if you reduce the neural inhibition (that's holding you back) you get closer to
maximal strength
▪ May get optimal motor neuron recruitment
▪ Reducing your neural inhibition could be:
• Overcoming fear of injury
• Taking dis-inhibitory drugs
• Hypnosis
• Psyching yourself up
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Muscle Hypertrophy
• Hypertrophy - increase in muscle mass
• Muscle hypertrophy is not required for increase in strength and power (neurological
factors)
• An increase in the size of your muscle fibers leads to an increase in muscle size
(hypertrophy)
• To get gains your rate of protein synthesis needs to be greater than the protein that's being
broke down.
• More efficient Mrna translation usually means more protein synthesis
• After you exercise you injure or cause damage to muscle fibers which activates protein
synthesis
• Myofibrils thicken and increase in number
• New sarcomeres form
• Increase in intramuscular ATP, PCr, and glycogen allows you to produce more anaerobic
energy
• Increase in contractile protein and energy generating compounds occur which decreases
the ratio of mitochondrial volume and/or enzyme concentration to myofibrillar volume
• Adults usually need more stimuli for anabolic resistance
• Adults have lower protein and energy intake
Myostatin
• Myostatin – negative regulator of skeletal muscle mass
• If you knockout myostatin then you get an increase in hypertrophy
Metabolic Adaptations in Muscle Fibers
• Endurance training:
o Increase oxidative capacity of fast-twitch fibers to almost equal slow twitch of
untrained person
o Some conversion of type 2b to 21 (more aerobic)
o Increases in mitochondria size and number
o Increase in total quantity of TCA and ETC enzymes
• Resistance training
o Type 2x gains 2a characteristics
o Volume of fast twitch fibers increase
o Hypertrophy in fast twitch predominates
o Improved glucose transport
• Skeletal muscle quality improved independent of changes in muscle mass
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Factors regulating muscle mass: genetics, nervous system activation, environmental factors, endocrine influences, physical activity, nutritional status. Physical activity and nutritional status are the main two factors that you can control that regulates muscle mass. Increase in intramuscular atp, pcr, and glycogen allows you to produce more anaerobic energy. Increase in contractile protein and energy generating compounds occur which decreases the ratio of mitochondrial volume and/or enzyme concentration to myofibrillar volume: adults usually need more stimuli for anabolic resistance, adults have lower protein and energy intake. Myostatin: myostatin negative regulator of skeletal muscle mass. If you knockout myostatin then you get an increase in hypertrophy. Intense endurance exercise can also inhibit performance in muscular strength activities performed after it: could impair ability to overload muscle during workout which could impair strength gains. Resistance training: does age matter: total work output was similar in older and younger men.