Module 7: Children, Adolescents, and Biological Sex in Exercise and Sport

Question 1

Define growth:

Answer 1

Changes in the size of an individual, as a whole or in parts. This occurs as a result of three physiological processes:
1. Hyperplasia = increase in the number of cells, significant contribution to prenatal growth
2. Hypertrophy = increase in the size of cells, contribution steadily increases when transitioning to infancy, childhood, and adolescence
3. Accretion = increase in intracellular substances

Question 2

Define maturation:

Answer 2

Progressive achievement of adult status. Characterized by two components:
1. Timing (when)
2. Tempo (rate)

Question 3

What is the major distinction between growth and maturation?

Answer 3

All children reach the same adult maturity, whereas adult size and body dimensions are variable

Question 4

With regards to height, what years does the fastest growth tend to occur?

Answer 4

First 2 years of life

Question 5

What age do girls and boys reach 50% of their adult height?

Answer 5

Girls: 18 months
Boys: 2 years

Question 6

By adulthood, which population tends to be taller and by how much?

Answer 6

Males: ~13 cm taller than females

Question 7

What are the two key observations that can be made when analyzing the typical height velocity curve for girls and boys?

Answer 7

1. Similar pattern of linear growth over time
2. Girls mature ~2 years earlier than boys, however, boys experience a tremendous growth spurt relative to girls (greater peak height velocity - point at which 92% of adult height has been reached)

APHV (Age of Peak Height Velocity) in girls: 11, boys: 13

Question 8

What happens to body composition (fat mass and fat-free mass) in boys and girls as they grow?

Answer 8

Up to approximately 10 years of age, boys and girls have a similar % of fat mass. However, beyond that girls have more - At the age of 5 we can see this slight increase come into play

Up to the age of peak height velocity, boys and girls have a similar % of fat-free mass. However, beyond that, boys have more

Question 9

What happens to one’s absolute (L/min) aerobic fitness with age?

Answer 9

Boys and girls both experience an increase with age

Question 10

What happens to one’s relative (ml/kg/min) aerobic fitness with age?

Answer 10

For boys, it is unchanged with age. For girls, decreases with age.

Question 11

What are the two ways in which CV responses are measured?

Answer 11

1. Indirectly: ultrasound (uncomfortable for children), gas collection (VO2, CO2 rebreathing) - both are limited to children >7
2. Direct: arterio-venous catheterisation

Question 12

Changes in CV responses to exercise in children over time can be classified into two categories:

Answer 12

1. Size-dependent: changes that result as a child grows - stroke volume will increase as the heart gets larger
2. Size-independent: changes that are not heavily dependent on age or size - HR

Maximum HR for children = ~195 to 200 bpm (220 - age equation only works for adults)

Question 13

What are the three main CV responses to exercise?

Answer 13

At the onset of exercise, an increase in muscle contractions = increased demand for O2

Demand is met by:
1. Increased vasodilation in active tissues accompanied by a decrease in resistance
2. Increase in sympathetic drive = increased HR, myocardial contractility, blood pressure
3. Skeletal muscle pumps = increased venous return

Question 14

What is the effect of exercise on heart rate: children vs adults

Answer 14

The pattern of response is similar in both populations

In children: Increase in HR with acute exercise

• The rate of increase in HR relative to exercise intensity is higher than in adults (steeper slope)
• Maximum HR achieved is greater than the adults
• Similar response in boys and girls: girls have a slightly higher HR for a given exercise intensity
• HR recovery is quicker in children than in adults

Adult population:
A greater difference in HR: women will have a greater HR for a given exercise intensity

Question 15

What is the effect of exercise on stroke volume (amount of blood ejected with every contraction of the heart): children vs adults

Answer 15

The pattern of response is similar in both populations

In children: Minimal or small increase in SV with acute exercise

• Lower SV compared to adults - due to the smaller heart size and lower blood volume
• Similar response in boys and girls: girls have a slightly lower SV for a given exercise intensity

Adult population:
A greater difference in SV: men will have a greater SV for a given exercise intensity

Question 16

How does cardiac output (Q) compare in children vs adults?

Answer 16

Children have a lower Q

Question 17

How does total peripheral resistance (TPR) compare in children vs adults?

Answer 17

Children have a greater TPR

Question 18

How does end-diastolic volume (EDV) compare in children vs adults?

Answer 18

Adults have a higher EDV

Question 19

What do we know about ventilation responses to exercise in children?

Answer 19

Largely size-dependent

Question 20

What is the general consensus that has been reached with regard to ventilation in children vs adults?

Answer 20

Children hyperventilate compared with adults at both rest and during exercise.

Question 21

What happens to the overall pattern of ventilation responses to exercise with age?

Answer 21

Breathing frequency:
As exercise duration increases, there is an increase in breathing frequency for both children and adults. However, the breathing frequency of children is substantially higher than that of adults

Minute ventilation:
As exercise duration increases, there is an increase in minute ventilation for both children and adults. The increase is much steeper in children at the onset of exercise relative to adults, suggesting that children display faster ventilatory kinetics during exercise.

However, the minute ventilation of children is substantially lower than that of adults

EXPLANATION:
Minute ventilation or ventilation rate: tidal volume x breathing frequency
Although children hyperventilate (take more breaths per minute), their tidal volume is lower due to smaller lung size which is why it tends to lower in children than adults

Question 22

How does the ventilatory equivalent (VE/O2 - the amount of air an individual must breathe to get a unit of oxygen in) differ in children vs adults in response to exercise?

Answer 22

Over a duration of exercise, boys will have a greater ventilatory equivalent than men. Thus, the conclusion can be made that children ventilate out of proportion to metabolic demand (have to breathe more to get in the same amount of oxygen).

Question 23

Is ventilation a limiting factor during exercise for healthy children?

Answer 23

No

Question 24

Why is RER lower in females than males during exercise?

Answer 24

Females utilize more fats than carbs:
1. They have lower glucose release from the liver
2. Lower muscle glucose uptake
3. Lower glycogen use during exercise (glycogen sparring: occurs to a greater extent in the luteal phase of a females menstrual cycle) - 25% greater utilization of muscle glycogen during moderate-intensity exercise in men

Differences in fuel utilization can be associated with estrogen - a study placed men on estrogen supplements and found a decrease in glucose oxidation and an increase in fat oxidation

Question 25

At the same absolute exercise intensity (i.e. 50W), how do the HR, SV, and Q of females compare to males?

Answer 25

1. Higher HR
2. Lower SV - attributed to the fact that females have a smaller heart and lower blood volume -> lower EDV -> lower SV
   Frank starlings law
3. Same Q

Question 26

At the same relative exercise intensity (i.e. 60% of VO2 max), how do the HR, SV, and Q of females compare to males?

Answer 26

1. Slightly higher HR
2. Lower SV
3. Lower Q - attributed to the fact that females are working at a lower absolute workload which requires less O2

Question 27

How does O2 carrying capacity differ in females relative to males?

Answer 27

Females tend to have lower Hgb (haemoglobin) content = lower oxygen-carrying capacity

The equation for calculating the content of O2 in arterial blood:
CaO2 = [Hgb] x 1.34 x % sat

Will result in a lower CaO2, thus a lower A-VO2 difference (CaO2 = CvO2)

Ultimately, it will result in a reduced capacity to increase the A-VO2 difference

Question 28

What are the two key reasons as to why the average VO2 max is lower in females than males?

Answer 28

1. Absolute VO2 max (L/min) is going to be lower due to a smaller body size
2. Relative VO2 max (ml/kg/min) is going to be lower due to the fact they have more body fat and less muscle mass compared to males