Exercise physiology in Pediatrics
Age group: 0-22
Growth, Development and
GROWTH: Refers to an increase in size of the body or
any of its parts.
DEVELOPMENT: Refers to differentiation of cells along
specialized lines of function (e.g., organ systems), so it
reflects the functional changes that occur with growth.
MATURATION: or functional adulthood refers to the
process of taking on an adult form and becoming fully
functional, and is defined by the system or function
being considered like for e.g., skeletal maturity, sexual
Period of Life
The period of life from birth to start of adulthood is divided
into three phases:
Infancy: is defined as the first year of life.
Childhood: spans the period of time between the end of
infancy and the beginning of adolescence and is usually
divided into early childhood (preschool) and middle
childhood (elementary school).
Adolescence: its onset is generally is defined as the onset of
puberty. For most girls, adolescence ranges from 8 to 19
years and for most boys from 10 to 22 years.
BODY COMPOSITION: GROWTH AND
DEVELOPMENT OF TISSUES
Height and Weight
The child reaches about 50% of adult height by the age 2.
Then just before puberty, the rate of change in height
increases markedly. The peak rate of growth in height occurs
at approximately 12 years in girls and 14 years in boys.
Growth in weight follows the same trend as height. The
peak rate of weight increase occurs at age 12.5 in girls and
age 14.5 in boys.
Girls mature physiologically about two years earlier than
Exercise, along with an adequate diet, is essential for proper
bone growth. Exercise affects primarily bone width, density,
and strength but has little or no effect on length.
The increase in muscle mass with growth and development is
accomplished primarily by hypertrophy of individual muscle
fibers through increases in their myofilaments and myofibrils.
Muscle mass peaks in girls between ages 16 and 20 and in
boys between ages 18 and 25, although it can be increased
through diet and exercise.
At physical maturity, the body’s fat content reaches
approximately to 15% of total body weight for males and 25%
for females. The differences are caused primarily by higher
testosterone levels in males and higher estrogen levels in
Myelination of nerve fibers must be complete before fast
reactions and skilled movements are fully developed because
myelination speeds the transmission of electrical impulses .
Balance, agility and coordination improve as children’s
nervous system develops.
Pulmonary and Cardiovascular Systems
Development of the pulmonary and cardiovascular
systems allow for greater capacities to perform both
aerobic and anaerobic exercises.
All lung volumes increase until the growth is complete.
Development of alveoli is complete by 6 years of age.
Throughout childhood and adolescence, growth in lung
size increases the available surface area for gas exchange
such that the arterial blood gas values in children are
similar to those for adults.
The maximal minute ventilation of a child increases
from 30 to 40 L/min at age 6 to 100 to 140 L/min by
Heart volume, relative to body size is larger in children than
Resting heart rate is higher in children than in adults because
the resting heart rate is generally negatively related to the
Blood pressure at rest and during exercise is lower in
children than adults because children have lower peripheral
resistance than adults.
Heart size is directly related to body size, so children have
smaller hearts than adults. As a result of this, and a smaller
blood volume, children have smaller stroke volume capacity.
A child’s maximum heart rate can only partially compensate
for this lower stroke volume capacity, and thus maximal
cardiac output is lower than that of equally trained adult.
To maintain the same VO2 with the lower O2 delivery due
to the lower cardiac output, the arterial to venous difference
is greater in a child.
Maximal O2 consumption (VO2 max) increases throughout
childhood and adolescence. Boys generally have higher VO2
max than girls because they are usually larger than girls.
At puberty the aerobic capacity for boys continues to rise,
but the rate of increase is diminished for girls due to
increased muscularity in boys and increased adiposity in
girls after puberty along with decreased hemoglobin
concentration following the onset of menses.
Both strength and power output increase from age 6 to
18 for both genders.
Boys demonstrate greater anaerobic capacities than girls
due to increase in male hormone production with the
onset of puberty.
Other factors responsible for higher anaerobic capacities
for both the sexes are related to rapid glycolysis as the
glycolytic enzyme capacity is lower in children than
Lactate production, the lactate threshold and the ability
to buffer lactic acid are all lower in children than in
Muscle ATP concentration is the same in children and
adults, but the smaller muscle mass in children greatly
reduces the power of output of children.
Evaluating fitness and Physical Activity in
The science underlying fitness assessment and activity
monitoring in children is not as advanced as with adults.
Traditional fitness tests have been criticized as being
evaluations of athletic ability rather than health-related
Questions related to the physiologic responses of
children to various types of exercise remain unanswered
because fewer scientists are studying children and
exercise than are studying adults and exercise.
Measuring health related fitness in children, on the other
hand , is difficult because most hypokinetic diseases are
not manifested until adulthood.
Fitness testing of Children
The two most common physical test batteries come from the
President’s council on physical fitness and Sport
(President’s challenge) and the Cooper Institute in Dallas ,
The President’s challenge, a physical fitness awards
program that recognizes children for their levels of physical
fitness, consists of five fitness tests:
1. Curlups or partial curlups,
2. Shuttle run,
3. Endurance run/walk,
4. Pull-ups, right angle pushups, or flex-arm hang and
5. V-sit reach or sit and reach.
PRESIDENTIAL PHYSICAL FITNESS AWARD STANDARDS (85TH PERCENTILE)
FITNESSGRAM TEST items are as follows:
Aerobic capacity (select one)
• The pacer, a 20-m progressive, multistage shuttle run set to music
• One mile walk or run
• Walking test (secondary students only)
Body composition (select one)
• Percent body fat calculated from triceps and calf skinfold measures.
Upper body strength (select one)
• 90-degrees pushups
• Flexed arm hang
• Modified pullups.
Flexed (select one)
• Sit and reach
• Shoulder stretch
Trunk extensor strength and flexibility
• Trunk lift.
Physical activity guidelines for infants, toddlers,
Guidelines for Infants
Infants should interact with parents and/or caregivers in
daily physical activities that are dedicated to promoting the
exploration of their environment.
Infants should be placed in safe settings that facilitate physical
activity and do not restrict movement for prolonged periods
Infants' physical activity should promote the development of
Infants should have an environment that meets or exceeds
recommended safety standards for performing large muscle
Individuals responsible for the well-being of infants should be
aware of the importance of physical activity and facilitate the
child's movement skills.
Guidelines for toddlers and preschoolers
Toddlers should accumulate at least 30 minutes daily of
structured physical activity; preschoolers at least 60 minutes.
Toddlers and preschoolers should engage in at least 60
minutes and up to several hours per day of daily,
unstructured physical activity and should not be sedentary
for more than 60 minutes at a time except when sleeping.
Toddlers should develop movement skills that are building
blocks for more complex movement tasks; preschoolers
should develop competence in movement skills that are
building blocks for more complex movement tasks.
Toddlers and preschoolers should have indoor and outdoor
areas that meet or exceed recommended safety standards for
performing large muscle activities.
Individuals responsible for the well-being of toddlers and
preschoolers should be aware of the importance of physical
activity and facilitate the child's movement skills.
PHYSIOLOGICAL RESPONSES TO ACUTE EXERCISE
Submaximal Exercise: to maintain adequate oxygen uptake during
these submaximal levels of work, the child’s arterial mixed venous
oxygen difference, increases to further compensate the lower stroke
• The increase in the arterial mixed venous difference is most likely
attributable to increased blood flow to the active muscles- a greater
% of the cardiac output goes to the active muscles.
Maximal Exercise: Maximum heart rate (HRmax) is higher in
children than in adults. But decreases linearly with age.
• Children under age of 10 frequently have maximum heart rates
exceeding 210 beats/min, whereas the average 20-year old has a
(Hrmax) of approximately 195 beats/min.
• During maximal exercise the child’s smaller heart and blood volume
limit the maximal stroke volume that he or she can achieve. Less
oxygen delivery limits the performance in activities other than those
in which the child merely needs to move his or her body mass, such
• Until physical maturity , maximal ventilatory capacity
and maximal expiratory ventilation increase in direct
proportion to increase in body size during maximal
• Aerobic capacity (VO2max) when expressed in L/min is
lower in children than in adults at similar levels of
training. This is attributable primarily to the child’s
lower maximal cardiac output capacity. When (VO2max)
values are expressed to normalise for the differences in
body size between children and adults there is little or
no difference in aerobic capacity.
When expressed relative to the body weight, a child’s
(VO2max) is similar to an adult’s, yet in activities such as
distance running, a child’s performance is far inferior to
adult performance because of basic differences in
economy of effort.
Running economy is lower in children compared with
adults when VO2 is expressed relative to body weight.
One factor has been identified to explain this difference
i.e. the difference between children and adults in stride
frequency for same fixed –pace run.
• Anaerobic capacity is lower in children than in adults,
which may reflect children’s lower concentration of the
key rate limiting enzyme phosphofructokinase or lactose
• Children have lower lactate concentrations in both blood
and muscle at maximal and supramaximal rates of work.
• Children cannot attain high respiratory exchange ratios
during maximal or exhaustive exercise, suggesting less
Children have always been perceived to be energetic ,
fit and strong because they are young.
Conditioning and Exercise
Strength training is a key component of sports conditioning
aimed at preventing potential injuries and increasing skill
Supervised strength training programs have been
researched in the pediatric population and have been
found to be effective in increasing dynamic strength and
safe for growing muscles, bones and growth plates.
A pre participation athletic examination is helpful for identifying
adolescents at risk of orthopaedic injury, and guidelines developed
by the American Academy of Pediatrics provide the most
current source on which conditions disqualify athletes from
Studies done by Blimkie CJR on Resistance training in
pre adolescence: issues and controversies and
Resistance training in pre and early puberty: efficacy,
trainability , mechanisms and persistence in the year
1993 and 1992 respectively; state that The
physiological mechanism for strengthening may not
be muscle hypertrophy as it is in adults. Neural
adaptation of motor unit activation and intrinsic
muscle function measured in twitch torque appear
to produce positive changes in motor skill and co-
ordination resulting in improved strength tests.
Neural adaptation occurs when there is an increased ability to
activate and coordinate the relevant muscles as opposed to
muscular adaptation where there is an increase in muscle size and
Research performed on children participating in specific sports
such as running studied aerobic capacity and found only a 6%
improvement in measured ventilatory oxygen uptake after a 12-
week supervised program. The expected improvement from a
similar program in the adult population is 18% to 20%.
Physiological differences in children, such as smaller organs in
proportion to body size and less efficient metabolism and heat
transfer, may contribute to lower training effects. The physical
benefits of exercise include increased bone density, decreased
lipid profiles, healthy body composition, improved posture and
reduced injury occurrence.
Psychological benefits for children and adolescents include
improved self-concept, mental discipline, acquisition of
social skills and improved lifestyle attitudes.
The question regarding the psychological effects of
exercise usually centers around the issue that competitive
sport may create unhealthy stress in children.
Stress in sport can be divided into the categories of
State anxiety, Trait anxiety and Burn-out. State anxiety
refers to a stress reaction that occurs during sport
participation. Trait anxiety refers to the intrinsic
personality characteristics of the child that may be
compounded in situational stress. Burn-out is a reaction to
the stresses of training and competition that manifests as
emotional exhaustion, withdrawal and decreased physical
Exercise prescriptions for children should
take into consideration the attention span of
the child as well as the extent to which the
parent(s) provide appropriate role models.
Prescribed activities should be enjoyable and
relatively nonspecific, with increased
movement as the initial goal, especially if the
child has a long history of physically
Benefits of Exercise Testing
Documenting any impairment in cardiac or pulmonary
Detecting and managing exercise-induced asthma.
Detecting myocardial ischemia.
Assessing physical work capacity.
Assessing the results of rehabilitation programs.
Documenting functional changes during the course of a
Providing indications for surgery, therapy, or additional
Assessing cardiac rate and rhythm as well as blood
Assessing exercise-related symptoms.
Evaluating the effects of therapy.
Increasing confidence, in the child and parents, in the
ability of the child to exercise safely.
STRENGTH, RESISTANCE AND
Parents and physicians have traditionally been concerned
about growth plate fractures and the risk of growth
The literature suggested that epiphyseal fractures
occurred more often in pubescents and post-pubescents
than in pre- pubescents .
Micheli in his 1986 study indicated that prepubescent
growth plates may be less prone to fracture because they
may be stronger and more resistant to sheer stress than
growth plates in the later stages of development where
the hormone activity level is higher.
The majority of injuries appear to be preventable
when conditioning techniques, equipment and rate of
exercise progression are supervised.
Movements such as improper lifting techniques,
excessive loading, rapid progression of weight and
ballistic movements all result in greater sheer forces
at the joint.
Guidelines from Committee on Sports Medicine
in Pediatrics stated that children are encouraged to
strength train using submaximal weights but should
avoid any practice of weight lifting, power lifting and
body building until they have reached a level of
Tanner stage 5 in developmental maturity.
STRENGTH AND WEIGHT TRAINING
Guidelines for safe strength training include the
components of frequency (how many times per week),
intensity (number of exercises and repetitions), type
(method of resistance and scope of exercise) and time
(length of session and progression).
This is referred to as the FITT formula.
Some of the key differences between adults and children
include: lower number of repetitions, submaximal weights,
exercising through the full range of motion and only doing
a resistance program two to three times per week.
Exercise prescription for children and adolescents
FREQUENCY INTENSITY TIME TYPE
Two to three times
Choose 4-5 muscle
groups and use 8-12
repetitions of each
group in 1 to 3 sets.
Start with no weight. Submaximal
At least one rest day
Choose 4-6 muscle
groups, use 9-15
repetitions of each
group in one to three
Add weight gradually to an
initial max of 6 rep, add 1-2
reps per training session
to a max of 12 to 15 reps.
Increase weight by 0.5 to 1
kg. Increments every third
No maximum lifts.
Each session should be of
20 to 30 mins.
Use the full range of
DYNAMIC RESISTANCE TRAINING
Dynamic resistance training involves concentric and
eccentric contraction of the muscle group performed
against a constant or variable resistance.
This type of training is suitable for developing muscular
fitness of both sexes including children.
TYPE INTENSITY REPS SETS FREQUENCY NO. OF EXE.
70-80% 1 RM 8-12 >1 2-3 8-10
60-75% 1 RM 10-15 >1 1 MIN 8-10
CHILDREN 70-80% 1 RM 8-12 1-2 2 8-10
1. Multijoint exercises are recommended for children and older
2. Programs for children and adolescents should be supervised
closely by instructors.
Guidelines for Resistance Training (ACSM 2000)
ORDER OF EXERCISES
A well rounded exercise program should include at least one
exercise for each of the major muscle groups in the body. In
this way, muscle balance – that is, the ratio of strength between
opposing muscle groups (agonists vs. antagonists, contralateral
muscle groups (right vs. left side), and upper and lower body
muscle groups can be maintained.
Order the exercises so that you first execute multi-joint
exercises such as the seated leg press, bench press, and lat pull
down – that involve larger muscles (e.g., gluteus maximus,
pectoralis major, and latissimus dorsi) and more muscle groups,
before progressing onto the single joint exercises for smaller
To avoid muscle fatigue in novice weight lifters, arrange the
exercises so that successive exercises do not involve the same
muscle group. This allows time for the muscle to recover.
Children with an illness or a disability should be
encouraged to exercise on a regular schedule and with
The fitness program components do not change but
the intensity, progression and choice of equipment
may need to be modified. Good exercise programs are
available for children with asthma, obesity and
developmental special needs.
The once taboo subject of weight training in children has
been researched and shows that safe exercise
programs can be prescribed. The key to success lies in
the exercise technique, proper progression and safe
equipment. Supervision is a vital component. Training
can serve to improve performance in many daily
activities such as socialization, school performance and