Human Growth and Development: Curves, Rates, and Somatotype Classification

Understanding Human Growth Curves and Body Types

4.1. The Emerging Growth Curve

Each variable of interest (weight, height, etc.) can be related to different ages, defining what is called the emerging growth curve. This curve is intended to gain insight into the process of the acquisition of some variables over the years.

4.2. The Velocity Curve: Measuring Physical Growth Rate

The velocity curve (or physical growth curve) shows the amount gained (rate) each year (e.g., in cm, g, or kg). In a typical curve of growth rate, specific moments are expressed:

• Slowdown
• Stability
• Acceleration
• Culmination point of growth (peak velocity)
• Final growth stage

4.3. Body Proportions and Differential Growth Rates

In the study of human growth, the body and its parts do not grow all at the same time or in the same proportion. For example, head size is larger than the trunk or limbs in infancy, and sexual organs remain dormant until around age 10. Based on these findings, we can speak of different growth rates across various tissues and body parts.

Differential Growth Patterns by Tissue Type

Analysis of growth curves indicates distinct patterns:

• Cephalic/Neural: One of the fastest growing parts, housing the brain.
• Lymphoid Tissue: Demonstrates the highest increase between ages 7 and 18, corresponding to periods where the chances of disease exposure are higher (related to the immune system).
• Reproductive: Grows rapidly during the years of puberty to reach the adult stage.
• General Body Parts: Other parts of the body (external dimensions, respiratory system, muscles, etc.) show a typical progression, with moments of acceleration, stability, and further acceleration (puberty).

Kahn's Findings on Neonate vs. Adult Proportions (1943)

Kahn (1943) stated that the neonate, compared with the adult, experiences differences in body proportions following an arithmetic progression:

1. The head increases 2 times from birth to the adult stage.
2. The trunk increases 3 times.
3. The superior limbs increase 4 times.
4. The lower extremities increase 5 times.

4.4. Body Types and Related Concepts

Several concepts are used to classify and describe the physical characteristics of an individual:

CONSTITUTION

All inherited and acquired factors that determine the physical and mental makeup of an individual.

BIOTYPE

Characteristics of the organism, according to different classifications (e.g., physiological or morphological).

SOMATOTYPES

Refers to the specific classification system used to categorize body types (e.g., Endomorph, Mesomorph, Ectomorph).

MORPHOLOGY

The characteristics of body shape and structure.

TYPE (Biological Definition)

A branch of biology that studies living beings and applies statistical methods, probability calculation, and mathematical analysis principles.

TYPE (Phenotypic Analysis)

Analysis of differential rates that a species presents in its morphological, biological, psychological, and sociological features (phenotypic characteristics).