APK 3110C Lecture Notes - Lecture 9: Motor Neuron, One-Repetition Maximum, Glycogen
6 May 2018
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APK 3110
Chapter 22: Muscular Strength
Muscular Strength and Training
• Initial changes in muscle strength after starting a training program are from neural
factors instead of structural changes within the muscle
• Familiarization of exercise performance increases strength measured
Neural Adaptations
• Neural adaptations increase strength initially
• Enhanced motor neuron output largely accounts for rapid and large strength increases
observed early in training, often without an increase in muscle size and CSA
o Increased muscle fiber recruitment at a given time
• Structural changes at NMJ
• Reason for large improvements in elderly that begin a resistance training program
Gender Differences in Muscle Strength
• Muscle CSA:
o When you control for muscle size (CSA) then the force produced by men and
women are similar
• Absolute muscle strength as total force exerted
o Absolute = total force in pounds or kg
o Men > women
▪ Women have 50 % less upper body strength and 30 % less lower body leg
strength
o Coincides with gender differences in muscle mass distribution
o Exceptions
▪ Strength trained track and field athletes
▪ Body builders who have strength trained for many years
• Relative muscle strength indexed to estimates of body composition
o Create a ratio score this usuall eliminates the differences between Men and
women
▪ Strength measured/Reference value (FFM, CSA, limb volume)
▪ Muscle quality may be similar if strength ratios are similar; differences in
absolute strength would indicate differences in muscle quantity
o However, if men and women have the same weight or body composition, men
will usually be stronger
▪ Larger differences in sedentary people
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Training Muscles to Become Stronger
• Strength increases when training near current max force generating capacity which
means that muscle overload must be induced
o Overload intensity is more important than what machine/device you use to
provide the resistance
o Overload intensity – amount of tension placed on muscle
o Overload – a muscle acting against a resistance normally not encountered –
unaccustomed stress
• 3 primary training modalities to increase strength
o progressive resistance weight training
o isometric training
o isokinetic training
Isometric
• isometric or Static = muscle activated without observable change in muscle fiber length
o muscle generates force and tries to shorten but cannot overcome the external
resistance
o no external work produced
Dynamic Movements
• Dynamic muscle action – produces movement of a skeletal body part such as trunk or
upper or lower limb
o 2 Types:
▪ Concentric – muscle shortens, joint moves as tension develops
• Example – bicep curl
▪ Eccentric – muscle lengthens while it develops tensions; weights lowers
against gravity
• Sarcomeres/muscle fibers lengthen to control speed of lowering
weight
o Usually both phases in weight lifting exercise
• In general improvements with strength training depend on training status prior to
program
o 40% = untrained improvement
o 20% = moderately trained
o 15% = trained
o 10% = advanced
o 2% = elite athletes
PRE: Progressive Resistance Exercise
• Training method that applies overload principle
o Progressive increase in stress placed on body to cause adaptations
▪ Frequency, volume, duration
• Basis of most resistance training programs
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Initial changes in muscle strength after starting a training program are from neural factors instead of structural changes within the muscle: familiarization of exercise performance increases strength measured. Neural adaptations: neural adaptations increase strength initially, enhanced motor neuron output largely accounts for rapid and large strength increases observed early in training, often without an increase in muscle size and csa. Increased muscle fiber recruitment at a given time: structural changes at nmj, reason for large improvements in elderly that begin a resistance training program. Isometric isometric or static = muscle activated without observable change in muscle fiber length: muscle generates force and tries to shorten but cannot overcome the external resistance, no external work produced. In general improvements with strength training depend on training status prior to program: 40% = untrained improvement, 20% = moderately trained, 15% = trained, 10% = advanced, 2% = elite athletes.
