Post-Natal Growth: Distance vs Velocity Curves

Objectives of Post-Natal Growth Study

• The goal is to understand how age, sex, and maturity influence somatic growth after birth.
• Analyzing how growth and maturation impact health and physical performance is important.

Distance vs. Velocity Curves

• Distance and velocity curves are used to track and analyze growth patterns

Distance Growth Curve

• Height in centimeters is recorded at each age (in years).
• The cumulative distance in kilometers is tracked versus time in hours, similar to a road trip analogy.

Distance Curve: Driving Analogy

• This curve plots cumulative distance (km) against time (hrs) to represent growth over time.

Distance Growth Curve (Stature)

• The shape of the curve is consistent for both height and weight in both sexes.
• Males are typically taller than females once they achieve full maturity.
• Males are slightly taller at all stages except between 11-13 years, when females experience peak growth.
• An average person reaches approximately half (50%) of their adult stature by age 2

Distance Growth Curve (Body Mass)

• The form of the weight for both sexes is the same.
• A lag in body weight growth is noticeable during the pre-natal stage of development.
• Individuals achieve about 20% of their total adult weight by just 2 years old.

Distance Growth Curve

• Stature and weight curves differ in shape and magnitude, especially during adolescence

Distance Curves

• Distant curves for height depict infancy, childhood, and adolescence
• There are a total of 3 distinct growth curve segments

Velocity Curve

• TO represents the take-off point.
• PHV is the peak height velocity.

Velocity Curve: Driving Analogy

• Displays the velocity (km/hr) against the time (hrs), capturing the rate of change in distance.

Distance vs. Velocity: Driving Analogy

• Distance (km) and velocity (km/hr) plotted against time (hrs)

Velocity Growth Curve

• A deceleration occurs predominantly until mid-childhood growth spurt.
• Males show longet (+2 yrs) appendicular growth with a rate of 5.5 cm/yr.
• The amplitude of the boys' growth spurt is bigger (common in nearly all boys).

Mid-Childhood Growth Spurt

• This is the individual growth curve, not population based.
• Occurs around 6-8 years old.
• Magnitude of velocity is around 1 cm/yr increase.
• Females experience the spurt, around 1 year earlier than males.
• Occurs more commonly in males, approximately 80% versus 33% for females.
• The velocity of the pubertal growth spurt is far lesser than this velocity.

Distance vs. Velocity Growth Curve

• The distance curve displays a steady accumulation of height against age including adolescence
• The velocity curve displays the rate of height change during these periods

Velocity Curves

• It is important to recognize when the slope changes
• Slope changes represents changes in growth rate
• Sex-differences can be gathered from changes in timing and magnitude

Growth Contributions to Sex Differences in Adult Stature

• Adult sex difference in height is around 13 cm.
• Pre-puberty is prolonged in boys.
• Boys have an additional two years of pre-adolescent growth around 5 cm/yr resulting in +10 cm
• Pubertal growth spurt is ~3 cm greater for boys

Timing and Sequence of Growth in Children

• Compared using Longitudinal samples of North American and European subjects
• Take off for girls is around age 9 and boys age 11
• PHV occurs at 11.5 for girls versus 13.5 for boys.
• PHV is 8 cm/year for girls compared to 9.5 cm/year for boys.
• Age at take off, and PHV occurs about 2 years earlier in girls.
• Pubertal PHV is a relatively early event that occurs ~1 year prior to menarche
• The intensity that girls go through their growth spurts is less intense for girls versus males

Growth Velocity Calculations and Interpretations

• Growth velocity calculations and interpretations explained

Graphing Parameters: Growth Velocity

• Age Increment = Age2 - Age1
  • Example: 8.4 - 7.5 = 0.9 years
• Height Increment = Height2 – Height1
  • Example: 128.5 - 124.0 = 4.5 cm

Graphing Parameters: Growth Velocity cont.

• Whole Year Velocity = Height Increment / Age Increment
  • Example: (128.5-124.0) / (8.4-7.5) = 4.5/0.9 = 5.0 cm/yr

Graphing Parameters: Growth Velocity cont.

• Age Centre = (Age2 + Age1)/2
  • Example: (8.4 + 7.5)/2 = 15.9/2 = 7.95 years

Growth Data: Example

• Example data includes Age, Height, Age Increment, Height Increment, Height Velocity, and Age Center for each data point
• Displayed in a table on the x and y axis of each graph.

Growth Data: Example cont.

• Growth data can be used to plot lines on a graph

Growth Data: Example cont.

• The goal is to know is to graph each set of data on a graph

Velocity Growth Curve: Body Mass

• Includes Early acceleration then deceleration following acceleration in about 2-3 years time.
• Pubertal growth spurt includes sex dichotomy when regarding body composition
  • Boys have increased levels of lean mass.
  • Girls present with fat mass.
• Age at peak weight velocity (PWV) usually later than PHV around six months.

Factors that Affect Post-Natal Growth

• Considers the various factors that account for changes in stature and body mass.

Factors that Affect Post-Natal Growth Cont.

• Primary factors in changes of Stature and Body mass are
  • Endocrine, Age, Timing, Sex, Genetics and Maturity

Age and Sex Differences

• Age and sex differences in the population are largely based on genetics
• Males tend to be taller and heavier with increasing growth over females
• Maturity occurs around 13 cm difference in the male versus female stature
• Males also tend to weigh around 12kg more than females

Genetic Influence on Adult Stature

• Twin model used is used to infer specific genetic effects and influence when determining adult stature
  • Known as DZ or dizygotic which regards fraternal twins.
  • MZ or monozygotic regards identical twins.
• DZ has around 50% in common when regarding genetic traits , MZ has 100 % in common

Maturity Influence on Stature

• Moderate to strong genetic influences can determine amplitude of maturity
• the Maturation itself does not affect individual growth outcome other than only the speed and tempo of growth

Timing Factors Influencing Growth

• In Diurnal effects include
  • Being Tallest upon waking
  • Shorter when as day is progressed and closer to an end
• Seasonal effects also affect growth
  • Typical growth pattern regarding the Canadian population
  • Seasonal rate may vary by population and region where one is

Timing Factors Influencing Growth cont.

• Secular trends are
  • Influenced regarding one social condition (e.g socioeconomic status and employment)
  • Shift regarding those with increased growth status after history

Changes in Shape and Body Proportions

• the Human Body shape may change continually
• Changes may come due to conception throughout one's lifespan

Changes in Shape and Body Proportions cont.

• General patterns of growth can greatly impact change

General Patterns of Growth Can Impact Changes Such As

• RAPID Growth of Infancy
• Early Childhood : RAPID
• Mid Childhood steady/slow incline
• Adulthood slow decline

Patterns of Growth

• Considers Cephalocaudal from one is top, and the next is bottom
• Principle, that is across general growth
• Early fetal stage accounts for head fast growth

Patterns of Growth cont.

• Distal to proximal rule based regarding the gradient
• Occurs at the time of adolescence
• Consisting of - Feet & hands - Leg length - Lastly Trunk length

Patterns of Growth cont.

• Considers General genetic patterns for general growth
  • Pattern that may consist of : Environmental and Hormonal

Sitting Height and Leg Length

• Stature = sitting height (SH) + leg length (LL)
• Trunk is longer, and S shaped
• Sex differences are relatively greater relating to leg length
• Noticeable differences relating to height with either setting or standing
• Both SH and LL may increase based on certain points with the change during their personal growth

What Does This Tell You About the Height Difference?

• Pertains to athletic difference regarding height

What Does This Tell You About the Height Difference Cont.

• Points out dominance relating to trunks during initial infancy
• Considers the progressively greater contribution from legs based on the age of one