355 Midterm 2

what does a distance growth curve show you?

height (cm) at each age (years), analogy (road trip driving distance, cumulative distance vs time)

what are the characteristics for distance growth curves in terms of stature?

common shape for both sexes for both height and weight, males typically taller at full maturity, males slightly taller than females at all stages except 11-13 years when females attain peak growth, half of adult stature by age 2

what are the characteristics for distance growth curves in terms of body mass?

same shape for weight for both sexes, lag in growth in body mass relative to height, ~20% of full adult weight size at 2 years

are the shapes of stature and weight curves the same for distance growth curves?

different

what are the growth curve segments?

infancy, childhood, adolescence

what is To and PHV in a velocity ccurve?

take off, peak height velocity

what does a velocity growth curve show you?

mostly deceleration until mid-childhood growth spurt, boys have prolonged (+2 years) appendicular growth at rate of 5.5cm/year, larger amplitude of spurt in boys (common in almost all boys and girls)

what are the characteristics of mid childhood growth spurt?

individual growth curve - occurs between 6-8 years, magnitude of velocity ~1cm/year increase, occurs earlier in girls by ~1 year, more common in boys ~80% vs 33%, much lower velocity compared to velocities during pubertal growth spurt

when does the slope change in velocity curves?

what information on sex differences in growth can we gather from velocity curve graphs?

consider timing and magnitude of changes (take off- initiation of growth spurt),

what are the characteristics of timing and sequence of growth?

age at take off and PHV ~2 years earlier in girls, PHV is relatively early pubertal event in girls (~1 year before menarche), girls have slightly less intense growth spurt vs boys, but individual variation is considerable

what is the average age at take off for girls?

9

what is the average age at take off for boys?

11

what is the average age at PHV for girls?

11.5

what is the average age at PHV for boys?

13.5

what is the average PHV for girls?

8cm/year

what is the average PHV for boys?

9.5cm/year

how do we calculate age increment?

age2 - age1

how do we measure height increment?

height2 - height1

how do we measure whole year velocity?

height increment/age increment

how do we calculate age centre?

(age2 + age1)/2

what do velocity growth curves show you in terms of body mass?

early acceleration, then deceleration followed by acceleration at 2-3 years, pubertal growth spurt is period of sex dichotomy in body composition (boys >lean mass, girls >fat mass), age at peak weight velocity (PWV) usually later than PHV ~6 months

what are the primary factors that account for changes in stature and body mass?

endocrine, timing, age, maturity, genetics, sex

how do age and sex differences contribute to post-natal growth?

largely due to genetics, taller and heavier with increasing age, at adulthood 913cm difference in stature, 12kg difference in weight)

how does genetics influence adult stature?

twin model used to infer genetic affects, dizygotic-fraternal, monozygotic-identical, DZ 50% common, MZ 100% common

how does maturity influence stature?

moderate to strong genetic influences on timing and amplitude of maturity, maturation itself doesnt affect final growth outcome just timing and tempo of growth

what are the diurnal effects of timing influencing growth?

tallest upon waking, shorter as day progresses

what are the seasonal effects of timing influencing growth?

typical growth pattern for canadian children, seasonal rate may vary by population and region, uncertain cause of seasonal variations (hormones)

what are the secular trends in how timing factors influence growth?

influenced by social conditions (socioeconomic status, employment status), children measured in 1891 were born during depression of the 1870s, shift towards increased growth status in recent history

how do shape and body proportions change with post natal growth?

changes continually from conception throughout lifespan

what is the general pattern of growth

infancy (rapid), early childhood (rapid), mild childhood (steady), adolescent spurt (rapid), into adulthood (slow)

what is the cephalocaudal principle?

top to bottom across growth, early fetal stage (head grows fastest), infancy (trunk accelerates), childhood (legs accelerate)

what is the distal to proximal rule in growth?

maturity gradient, during adolescence (feet and hands, leg length, trunk length)

what factors impact patterns of growth and how?

genetic factors (determine general pattern of growth), environmental factors (determine whether genetic potential is reached - disease, nutrition), hormonal factors (specific to growth period)

what is stature and its cahracteristics?

sitting height + leg length, trunk is typically longer than legs (s-shaped curve for trunk), relatively greater sex difference in leg length vs sitting height (more noticeable size difference when standing vs sitting), both SH and LL increase with age, but the ratio changes during growth

what are characteristics of the sitting height/stature ratio?

dominance of trunk in infancy, progressively greater contribution from legs with age, decrease in ratio pre-puberty, increased trunk length during puberty increases ratio, trunk typically longer than legs, after puberty female have relatively greater trunk length (males greater leg length)

what are the characteristics of timing of segmental growth spurts?

later growth spurt in boys for all segments, growth progresses in a distal to proximal fashion during puberty

what are the effects of differential timing of growth spurts on different somatic tissues?

long bones grow in length first (distal to proximal), muscle mass increases after (LBM in plot), bone mass increases after (BMC in plot), muscle strength increases after muscle mass and size, relative weakness of limb during growth spurt, awkward and uncoordinated movements, prone to injury (clinical trainign and coaching implications, kids grow long before they grow strong)

what is the timing of growth related to peak height velocity?

first peak leg length velocity, stature (PHV), peak trunk length velocity, peak body weight/lean mass velocity, peak bone mass/strength velcoity

What are the age/maturity effects on physiological and practical consequences of changing body proportions?

fairness of competition (unfair for younger kids to compete with older kids or adults, early maturers may have temporary advantage in some sports), susceptibility to certain injuries during the growth spurt depending on location of growth

What are the sex effects on physiological and practical consequences of changing body proportions?

advantage to boys when competing with girls of equal height post puberty, when relative limb length changes are important, advantage to girls during puberty in some sports (earlier growth), advantage/disadvantage depends on type of sport, age, and maturity, a great coach/doctor/teacher takes advantage of this knowledge