Nov 29 – Development of Strength and Flexibilty Chapter 16
Muscle Mass and Strength
• Those who gain muscle mass will gain strength but not gain flexibility
• Strength is the ability to exert a coordinated force to move an object.
• We develop our muscle mass in a sigmoid pattern.
• When we gain our muscle mass, we are gaining it by hypertrophy. There’s an
increase in fiber diameter.
• Women tend to have a smaller muscle mass. Men have more muscle mass in
their upper body.
• Around 20-50 years, there is a slight decrease in muscle mass
• After 50, there is more of a decline in muscle mass
Cross sectional area: the larger the muscle (the cross sectional area), the more
force a muscle can produce
Neurological factors: strength is also determined by how many fibers we can
recruit, whether we can recruit only those fibers needed. It also depends what type
of lever we are working with and where that muscle force is applied.
Class 2 levers have a long moment arm. It gives us a significant mechanical
advantage. (ex. When doing a calf raise. Ball of foot is pivot point
Class 3 levers (ex. Bicep curl) elbow is fulcrum, weight is working hand and muscle
force is working near elbow.
Strength doesn’t always change in parallel with muscle size. This is due to
neurological factors. When there is a strength change, it can be due to cross
sectional area, neurological factors, or both.
Developmental Changes in Strength
• Strength increases as children grow
• Boys and girls are similar in strength levels until 13 years old
• Peak strength increases follow peak muscle increases • Difference in size of muscle is the difference between strength of kids and
• More mature kids are stronger
Strength Increases Steadily As Children grow
• Isometric = when you exert a force but muscle length stays the same
• Iso kinetic = when you exert a force but muscle speed stays constant
• As we age, we increase amount of fibers recruited
• When we start a new training program, we don't see size increases
immediately but we will be able to recruit more fibers as we practice, making
us able to lift more
Strength In Adolescence and Young Adulthood
• In adolescence, males add more muscle mass
• Men have more cross section area (especially in arms and upper body) and
are stronger than women
• Men also have androgens such as testosterone which helps build muscle
• Size doesn’t account for all gender differences
• Cultural norms can affect motivation
• Cultural norms can affect habitual activity levels (women aren’t put in
situations where they have to exert maximal force)
• When we repeat experiments, women perform better in strength exercise
• After growth ceases, increases in muscle mass are associated with resistance
Strength in Middle and Older Adulthood
• Strength generally declines gradually after the 30s • After 50, there is an 18-20 % decline in strength
• There’s also a decline in muscle size in addition to strength. However, we lose
more strength than size as we age due to neurological issues. Our type 2
fibers decrease in size and we aren’t able to generate the same amount of
force. Not as many fibers will be recruited.
• Loss of strength may be greater than loss of muscle mass
• Theres also a decrease in the amount of capillaries
• Our eccentric contractions will be maintained, where we will see decrease in
concentric phases of movements
• We will be better at low level intensity and can produce better forces in small