Physical and Motor Development

1
Physical and Motor Development

• Implications for Training
• Michael Horvat

2
Physical and Motor Development

• Children do not grow at a constant rate and there
  are individual differences in physical
  development at any given chronological age
• Group of 14-year-olds can have height differences
  as great as 9 in. and 40 lbs. 11 yr old girl may
  be taller and more physically skilled than 11 yr
  old boy
• Differences correspond to variations in timing
  and magnitude of growth during puberty (girls
  8-13, boys 9-15)

3
(No Transcript)
4
(No Transcript)
5
Physical and Motor Development

• Maturity assessment can be used to evaluate
  growth and development patterns in children and
  can be used to measure fitness including muscular
  strength and motor fitness for fitness testing
  and athletic competition.
• Sensitivity to individual differences in
  abilities and past experiences important for
  training adaptations i.e. in early or late
  maturing children
• Training age or length of time in training can
  influence adaptation to training and magnitude of
  gain

6
Physical and Motor Development

• During peak height velocity (12 in girls and 14
  in boys) children are at an increased risk for
  injury.
• Relative weakening of bone, muscle imbalances
  between the flexor and extensor groups around a
  joint and relative tightening of muscle tendon
  units spanning rapidly growing bones are risk
  factors for overuse. Emphasize flexibility,
  correct imbalances, decrease volume and intensity
  of training

7
Learning Activity

• Preadolescent children can improve strength with
  resistance training. Neurological factors as
  opposed to hypertropic factors are responsible
  for these gains

8
Physical and Motor Development

• Muscle and bone growth
• Prenatal by hyperplasia (number of cells)
• hypertrophy (size)
• I year little difference in fiber distribution
• Undifferentiated prior to 30 weeks gestation
• Type I 40 at birth, Type II 45 at birth
• fiber size increases at 2 years max rate at
  10-16 years
• Sarcomeres (length)
• Muscle mass-minimal during childhood increases
  in boys 17-20, 54 of weight increases in girls
  13-16, 45 of weight

9
Physical and Motor Development

• At birth 25 muscle mass 40 in adulthood peak
  mass 16-20 in girls and 18-25 in boys
• Puberty a tenfold increase in testosterone
  production in boys and increase in muscle mass
  Girls increase is estrogen causes increase in
  body fat, breast development widening of hips
• Muscle increases in hypertrophy not hyperplasia
• Mass is affected by exercise and diet or both
• Fiber size and number decrease in aging from
  neural factors, vascular changes, collagen, motor
  end plates and isotonic twitch

10
Physical and Motor Development

• Bone formation occurs in diaphysis (central shaft
  of long bone) and growth cartilage (located at
  epiphyseal or growth plate, joint surface and
  apophyseal insertions of muscle tendon units
• When epiphyseal plane becomes ossified long bones
  stop growing. Bones typically fuse during early
  adolescence with girls 2-3 yrs before boys

11
Physical and Motor Development

• Particular concern is vulnerability of growth
  cartilage to trauma and overuse-disrupt blood and
  nutrient supply and permanent disturbances
• Trauma from falls or excessive repetitive stress
  may result in a ligament tear or epiphyseal
  plate fracture. Peak incidence occurs at peak
  height velocity

12
Learning Activity

• Growth cartilage in children is located at the
  epiphyseal plate the joint surface, and
  apophyseal insertions. Damage to the growth
  cartilage may impair growth and development of
  affected bone

13
Physical and Motor Development

• Skeletal Growth
• 2 month primary ossification centers
• Postnatal- growth of epiphyseal plate
• Layers of epiphyseal plate
• zone of resting cells
• proliferative zone
• hypertropic zone
• calcified cartilage zone
• Osteoblasts
• Bony skeleton 14 of wt97 of ht.
• Functions
• protection of vital organs
• support of body weight
• storage of minerals
• structural leverage for movement
• bone marrow storage

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Physical and Motor Development

• Structure, stiffness, strength gt function
• Aging losses-women 30, men 50
• Bone mass in third decade men half of women
• Appositional growth( laying down new bone on
  outer surface of the bone and is absorbed from
  the inner surface. Continues throughout life. In
  childhood and adolescence formation greater than
  absorption

18
Physical and Motor Development

• Osteoporosis
• Osteopenia, ostemalacia
• Other terms
• epiphyseal plate-growth zone composed of hyaline
  cartilage
• metaphysis-wider part of shaft of long bone
• diaphysis-shaft of long bone formed by primary
  centers
• epiphysis-ends of long bone formed by secondary
  centers

19
Physical and Motor Development

• Developmental Changes in Strength
• Increases in muscle mass throughout
  preadolescence and adolescence increase
  strength. Growth curves are similar to muscle
  mass.
• In boys peak gains in strength occur about 1.2
  yrs after peak height velocity and 0.8 years
  after peak wt. velocity with weight being primary
  indicator. This pattern suggests that during
  periods of rapid growth, muscle increases in
  mass, then strength.
• In girls, peak gains is strength also occur after
  peak height velocity although there is more
  variation in strength

20
Physical and Motor Development

• The relationship of strength to height and weight
• Although strength is essentially equal in boys
  and girls during preadolescence, hormonal
  differences during puberty are responsible for
  the acceleration of strength development in boys
  and the continuation of approximately the same
  rate of strength development of girls during
  preadolescent years
• On average peak strength is attained by 20 yrs in
  untrained women and 20-30 in untrained men
• An important factor in the expression of muscular
  strength in children is the development of the
  nervous system

21
(No Transcript)
22
Physical and Motor Development

• If myelination of nerve fibers is absent or
  incomplete, fast reactions and skilled movement
  cannot be successfully performed and high levels
  of strength and power not possible.
• As the nervous system develops, children improve
  in skills that require balance, agility, strength
  and power.
• Since myelination of many motor nerves areare
  incomplete until sexual maturation children
  should not be expected to respond to training in
  the same way or reach the same skill level until
  they reach neural maturity.

23
Physical and Motor Development

• Early maturing child has an advantage in strength
  compared to a later maturing child with less
  muscle mass
• Physical differences and body proportions also
  give some children advantages.
• Although late matures tend to catch-up, many
  other factors such as motivation, coaching and
  ability will contribute to success

24
Physical and Motor DevelopmentImplications for
Training Children

• Changes in neuromuscular functioning are at least
  partially responsible for exercise induced
  adaptations in children. Changes in hypertrophy
  can significantly impact training-induced
  strength gains in adolescents and adults but
  unlikely for preadolescents due to inadequate
  levels of circulating testosterone
  (preadolescence 20-60 ng/100 adolescence
  600ng/100 in males and females unchanged)
• It appears that preadolescents have more
  potential for an increase in strength due to
  neural factors such as increases in motor unit
  activation, recruitment and firing. Also
  intrinsic muscle adaptations, improvements in
  motor skill performance and coordination of
  involved muscle groups, muscle synergy can aid
  strength performance in preadolescence

25
Learning Activity

• A parent approaches you about beginning a
  strength training program for his 10-year-old
  son/daughter. What advice would you give him?

26
Physical and Motor Development

• Potential Benefits
• Program interventions have potential to influence
  many health and fitness related measures
• May help reduce injuries in sport and recreation
  activities
• Regular participation may decrease fatness among
  obese children and adolescents
• Regular participation has a favorable influence
  on growth at any stage of development and has
  been shown to enhance bone density in children
  and adolescents

27
Physical and Motor Development

• May also increase a young athletes resistance to
  acute and overuse injuries
• Aid in preparing young athletes for demands of
  sport competition and overcome sedentary life
  styles
• In contrast to early sport specialization the
  development of fundamental fitness and motor
  skills aid in sport success
• Elimination of injuries is unrealistic but aids
  young athletes in handling the duration and
  magnitude of forces in practice and competition

28
Physical and Motor Development

• Concerns
• Biggest concern is potential injury to the
  epiphyseal plate
• Also concerns for repetitive use of soft tissue
  injuries to lower back, shoulder, and arm

29
Physical and Motor Development

• Program Design
• Resistance training
• Plyometrics
• Prehab exercise to base and core movements

30
(No Transcript)
31
(No Transcript)