Lesson_03_Commentary

Lesson_03_Commentary - Growth Spurt Muscle Mass and Body...

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Growth Spurt: Muscle Mass and Body Fat x Rapid acceleration in height and weight; significant boost in muscle and body fat x By the end of puberty, the muscle to fat ratio is: ± Boys = 3:1 ± Girls = 5:4 x Boys gain muscle at a faster rate than girls x Girls gain fat at a faster rate than boys, especially just before the start of puberty x Girls start puberty slightly earlier than boys x Between ages 10-12, girls generally experience greater gains in both muscle mass and fat; weight gain is usually greatest during this time, gaining nearly 18 pounds per year on average x Boys generally have greatest proportional weight gain between the ages of 13-14, gaining approximately 20 pounds per year x Total weight gain for both sexes equivalent to about half of their adult weight
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Growth Spurt: Changes in Height x At peak height and velocity, which is the point at which the growth spurt is at its maximum rate, the annual growth will be on average: ± Girls will grow 3.5 inches ± Boys will grow 4.1 inches x Cumulative Growth vs Per year Growth (see graph) ± Peak occurs 1-2 years earlier in girls ± Girls tend to be taller between ages 11-13 ± By age 17, girls have reached 98% of their total adult height; boys don't reach this point until they are close to 18 Clumsiness x Adolescent body grows in an asynchronous pattern known as the distal-proximal trend ± Growth usually starts in hands and feet, then legs and arms, then to the center of the body and torso x Areas of the brain such as the cerebellum can't keep up, especially around the time of the peak height velocity x 10 and 15 year old boys much better at keeping balance x 13 year olds lost balance twice as many times as older or younger boys x 13 year olds grow the fastest; as much as 2 inches in 6 months; feet grow first x Puberty in boys occurs at 10-14 years old; most start by 13 but not all
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Culture and Pubertal Timing: The Secular Trend x Norway, 1870: average age of menarche was 17; today it between 12-13; similar results found in the US (secular trend) x x Within developing nations, onset of menarche is still much later x Secular trend of menarche slowing down. We may be experiencing a floor effect in which we are nearing a lower biological barrier. However, we are still seeing trends of early pubic hair growth and breast development.
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Influences on Timing x Age of onset of puberty is largely something that is inherited x Monozygotic (identical) and dizygotic (fraternal) twins x Correlation of timing is reduced as twins get older as they have fewer shared influences Influences on Puberty x High levels of chronic exercise can delay the onset of puberty; probably due to the reduction of stored energy (fat) x Exercise in moderation; is recommended x Energetics Theory: chronic malnutrition will not only contribute to late onset of ouberty but also leads to slower overall growth and a smaller adult size; energy will be used for basic mantainence
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Lesson_03_Commentary - Growth Spurt Muscle Mass and Body...

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