1
Q
how many chromosomes does each human cell have?
A
46 chromosomes in 23 pairs, one pair of these chromosomes are sex chromosomes
2
Q
what is a chromosome?
A
a chain of DNA contained within the nucleus of all human cells
3
Q
gametes
A
- ovum (produced by ovaries) and the sperm produced by the male testicles
- contain only 23 chromosomes each
- ensures that when the egg and sperm get fertilized to form a baby, it contains 23 pairs and restores the total chromosomal count to 46
4
Q
chromosomes of gametes
A
- females have XX chromosomes while males have XY chromosomes
- males can generate sperm with either X or Y chromosomes
- ovum contain only an X chromosome
- the presence of the Y chromosome is responsible for trigger male development; in the absence of a Y chromosome, the fetus will undergo female development
5
Q
biological sex
A
- a scientific description of the reproductive anatomies that have evolved to fulfil the function of sexual reproduction
- sex is fundamentally defined by male and female reproduction anatomy called phenotypic sex, independent of humans and society
- for over 99.9% of people, the sex of a person as female or male is clear, determined at conception, and observable whether prior to birth (by chromosomal analysis or sonogram) or at birth
- in any individuals, reproductive anatomy is almost always unambiguously male or female and observed correctly at birth, regardless of ultimate sexual function or dysfunction
- does not meet the defining criteria for a spectrum
6
Q
disorder of sexual development (DSD)
A
- conditions in which chromosomal sex (XX or XY) is inconsistent with phenotypic sex (reproductive organs) or in which the phenotype is not classifiable as either male or female, occurs in 0.018% of population
- sometimes referred to as intersex
- most of these disorder are male or female-specific and do not cause ambiguous biological sex
- some individuals have reproductive anatomies with both male and female features; here, biological sex classification is a complex process with input from medical professionals and parents
7
Q
gender
A
a social construct
8
Q
prenatal development
A
- early development is controlled by genes, either follows normal development or inherited abnormal development
- the embryo or fetus is sensitive to extrinsic factors such as nutrients, viruses, drugs and physical activity
- a healthy fetus has the best chance of reaching its full genetic potential, including its potential for skill performance
- view physical growth and development as a continuous process that begins at conception
- individuals are, in part, products of the factors that affected their prenatal growth and development
9
Q
embryonic development
A
- period from conception to 8 weeks
- differentiations of cells to form specific tissues and organs
- limbs formed and heartbeat begins at 4 weeks
- human form noticeable at 8 weeks, eyes, ears, nose, mouth, fingers and toes are formed
- size of a bean by 8 weeks
10
Q
fetal development
A
- called a fetus
- period from 8 weeks to birth
- continued growth by hyperplasias (increase in cell number), and hypertrophy (cell size)
- cephalocaudal growth (head to toe), head and facial structures grow fastest, followed by the upper body and then by the relatively slow-growing lower body
- proximodistal (near to far), the trunk tends to advance, then the nearest parts of the limbs and finally the distal parts of the limbs
11
Q
fetal nourishment
A
- oxygen and nutrients diffuse between maternal and fetal blood in the placenta
- placenta will filter out some potentially harmful chemicals, viruses, but can’t filter out it all
- poor maternal health status can affect the fetus
12
Q
abnormal prenatal development
A
- congenital anomalies - a wide range of abnormalities of body structure or functions that are present at brith and are of prenatal origin
- the source of abnormal development can be genetic or external
- genetic: trisomy 21, aka down syndrome
- structural: congenital heart defects, often no clear cause, could be genetic, exposures, diet, or maternal disease
- external exposures: a teratogen is an agent or fact that causes abnormal prenatal development upon exposure, eg. Rubella virus, early exposure can lead to miscarriage, harmful is exposed during first 4 weeks
13
Q
external causes of abnormal development
A
- the placenta screens some substances (eg. large viruses) but not all harmful ones
- harmful environmental factors include pressure, temperature, X rays, pollutants
- tissues undergoing rapid development at time of exposure are most vulnerable
14
Q
physical growth
A
a quantitative increase in size
15
Q
development
A
- a continuous process of change in function capacity
- the ability to move, live and excel in the real world
- humans are always developing, but change may be more or less noticeable at certain points
16
Q
maturation
A
- the developmental process leading to a state of full function
- an adult like state
- maturation implies progress toward physical maturity, the state of optimal functional integration of an individual’s body systems and the ability to reproduce
17
Q
concepts of maturation
A
- two children of the same age can be dramatically different in maturation status, with one being an early maturer and the other being a late maturer
- two children of the same size can be different ages
- it is difficult to infer maturity from age alone, from size alone or even size and age considered together
- an individual child can appear small and slight of build but may be relatively mature for their chronological age
18
Q
postnatal development
A
- anthropometry is the science of the measurement of the human physical form
- growth is predictable and consistent but not linear
- overall growth follows a sigmoid (S-shaped) patterns: rapid growth after birth, followed by gradual but steady growth during childhood, then by rapid growth during early adolescence, and finally by levelling off
- anthropometric sex differences are minimal in early childhood, with boys begin very slightly taller and heavier
19
Q
height
A
- height follows a sigmoid pattern
- girls: peak height velocity occurs at 11.5 to 12 years, growth in height tapers off around 14, end around 16
- early maturing girls tend to be initially taller, but girls who mature later have a longer growth period and tend to consequently be taller in adulthood, similar tend occurs in boys
- average height girls: 5’3”, boys: 5’9”
- boys: peak height velocity occurs at 13.5 to 14 years, growth in height tapers off around 17, ends around 18
- long period of growth of males contributes to absolute height differences, they have an additional 2 years of growth
20
Q
weight
A
- weight follows a sigmoid pattern
- it is susceptible to extrinsic factors, especially diet and exercise
- people grow up and then fill out
- peak weight velocity follows peak height velocity ( by 2.5-5 months in boys, 3.5-10.5 months in girls)
21
Q
relative growth
A
- head-heavy, short-legged form at birth, some body parts need to grow faster
- in girls, shoulder and hip breadth increase at about the same rate
- in adolescence, boys increase in shoulder breadth
22
Q
menarche
A
- the first menstruation
- girls as a group mature at a faster rate than boys; they enter their adolescent growth spurt sooner and their secondary sex characteristics appear sooner
- in the past several decades, the average age of menarche has decreased to between 12 and 12.5 years, it was 16-17 years in the mid-1800s
- diet, sedentary behaviour, and low physical activity are thought to contribute by causing elevated estrogen levels
- higher income is associated with lower early menarche rates, but higher rates for late menarche
- factors that contribute to early menarche include risky sexual behaviour, obesity, diabetes, cardiovascular disease and breast cancer
23
Q
male puberty
A
- boys have no landmark comparable with girls’ menarche for puberty; the production of viable sperm is a gradual process
- age at voice break and age of first conscious ejaculation, which are late markers of puberty, occurring between ages 13.3 and 14.5
- age at peak height velocity (PHV), are alternative markers of puberty
- measurement of reproductive hormones in serum, urine or saliva
- existing data regarding the impact on obesity of puberty in boys are conflicting, some research shows delayed puberty seen in very lean as well as very obese boys
24
Q
Tanner and Marshall Scale
A
- scale assessing stage of male development
- stage 1: before any physical signs of puberty appear (age 9-10 average)
- stage 2: 11 years
- stage 4: 14 years, puberty obvious
- stage 5: 15 years
25
extrinsic influences on postnatal growth
| catch-up growth
- during periods of rapid growth, such as just after birth and in early adolescence, growth is particularly sensitive to alteration by environmental factors such as breastfeeding and nutrition
- catch-up growth: rapid physical growth of the body to recover some or all potential growth lost during a period of negative extrinsic influence, occurs once the negative influence is removed
- whether the child recovers some or all of the growth depends on the timing, duration, and severity of the negative environmental condition
26
play
- important to healthy brain development
- allows children to create a world they can master, address fear, and practice adult roles
- undirected play allows children to learn how to work in groups, to share, to negotiate, to resolve conflicts, and to learn self-advocacy skills
- encouraging unstructured play will increase physical activity levels in children
27
sex differences throughout childhood and maturation
| brain development
- the prefrontal cortex matures 2 years later in boys, responsible for impulse control planning, self-regulation, decision-making and judgement
- cerebellum reaches full size for girls at 11 and boys at 15, modulates emotional, cognitive, and regulation capacity, in addition to balance/coordination
- chronological age is not the same as developmental age
- certain traits are more associated with one sex or the other
- distributions overlap look at the average expression of a trait in one gender, the biggest difference are at the tails of these distributions
- environment and culture matter greatly
- these difference have a relatively small impact on day-to-day life in the 21st century, we motivate people and development differently these days
28
maturation and movement
- maturation status is a structural constraint influencing movement
- individuals who are more mature are likely to be stronger and more coordinated than those who are less mature, even at the same chronological age
- it is tempting to infer movement performance potential from size or age alone, but maturation status is a powerful predictor of performance potential
- periods of motor incoordination or "adolescent awkwardness," may occur during the adolescent growth spurt, last approx. 6 months
29
assessment of physiological maturation
- compare measurements with group norms
- the appearance of secondary sex characteristics or menarche
- skeletal changes and status
30
skeletal maturation
- ossification is the hardening of the bones
- by comparing an x ray of skeletal maturations with a set of standards, developmentalists can assign individuals a skeletal age
- in early maturers, skeletal age is older than chronological age, and in late maturers skeletal age is younger than chronological
31
adulthood and aging
- some measures of body size can change in adulthood
- these changes reflect the aging of tissue, and probably to a greater extent, the influence of extrinsic factors
- height is stable in adulthood but may decrease in older adulthood due to compression of cartilage pads and osteoporosis
- the average adult starts gaining weight in the 20s
- older adults sometimes lose weight due to inactivity and a consequent loss of muscle tissue, and loss of apetite
32
jump height and maturation of developmental system
- specific systems of the body can create unique structural constraints
- height is a factor and a product of the body's skeletal system
- strength is a factor and product of the muscular system
- the amount of adipose tissue influences body weight and thus how easily one can jump up
- the nervous system must coordinate the muscles to produce the jumping movement
33
skeletal system
- defines an individual' structure
- not hard and static; it is living tissue, there are 206 bones
- it undergoes considerable change over the lifespan and reflects the influence of both genetic and external factors
34
muscular system
- allow skeletal movement
- more than 200 muscles permit a vast number of movements and positions
- changes over the lifespan under the influence of genetic and external factors
35
adipose system
- adipose tissue plays a vital role in energy storage, insulation and protection
36
endocrine system
- control over specific cellular functions through hormones such as metabolism, energy levels, reproduction, growth, and response to injury, stress and mood
37
nervous system
- no single system is as much the essence of an individual
- the nervous system controls movement and speech, it is the site of thinking, analysis and memory
- its development is important for social, cognitive and motor development
38
rate-limiting constraints
- a system that lags in development can be a developmental rate limiter
- muscular: ability to hold ourselves up
- skeletal: bone strength to support ourselves
- adipose: provide energy for activity
- endocrine: manage metabolism
- nervous: coordination of movement
39
prenatal development: skeletal system
- prenatally, the embryo has a cartilage model of the skeleton
- ossification begins at primary centres in the mid portions of long bones, at around week 6 or 7 in the womb
40
prenatal development: muscular system
- prenatal growth involves hyperplasia and hypertrophy
- muscles increase in diameter (hypertrophy) and length by the addition of sarcomeres
41
muscle fibre type
- adult muscle is composed of type I (slow-twitch) and type IIA, IIX, and IIB (fast-twitch) fibres.
- at birth, 15-20% of fibres are undifferentiated.
- by age 1, distribution of muscle fibre type is similar to adult distributions: 50% ST and 50% FT
- exact proportions vary among individuals due to genetics and activities they engage in
42
prenatal development; adipose system
- adipose tissue first appears in the fetus at about 3.5 months
- adipose tissue increases rapidly the last two prenatal months
- adipose tissue accounts for only about 0.5kg of body weight at birth
43
prenatal development: endocrine system
- the interaction of hormones, genes, nutrients and environmental factors begins in utero
- the placenta produces its own hormones and serves as a barrier to prevent the mother's hormones from flooding the fetus' system
44
prenatal development: nervous system
- the central nervous system includes the brain and spinal cord, contains neurons which act as messengers
- the peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body
- neurons use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system
- genes direct the development of structures, but the extrinsic factors fine-tune the system
- neurons proliferates in the early prenatal period at an astonishing rate of 250,000 per minute
- immature neurons are formed, made into a general types, and migrate to their final location, they proliferate at a rapid pace and most are formed by the 4th prenatal month
- recent research shows that mass migration occurs up to 3 months after birth, happening at the same time as the infant begins to interact with the environment
45
childhood and adolescence: skeletal system
- intramembranous ossification occure to create the flat bones of the face, most of the cranial bones, and the clavicles
- compact and spongy bone develops directly from sheets of connective tissues, the area where the flat bone is to come
- on a baby, those spots are known as fontanelles, they are soft and spongy, helps to protect and cushion brain from impacts
- growth in bone length occurs at secondary ossification centres at the ends of bones called epiphyseal plates, growth plates or pressure epiphyses
- thin layers of cartilage disc entrapped at the distal ends of long bones
- endochondral ossification - when these areas of cartilage are replaced with bone, closing the plate
- increase in bone girth is called appositional growth
46
cessation of bone growth
- bone growth stops at different times for different bones
- all typically close by age 18 or 19
- closure occurs at a younger age in girls, for example on average, the epiphysis at the head of the humerus closes in girls between 12 and 16 years but in boys 14 and 19 years
47
childhood and adolescence: muscular system
- postnatal growth mainly involves hypertrophy
- muscle growth follows a sigmoid pattern
- differences between the sexes become marked in adolescence, especially in upper body musculature
48
sex differences in muscular system
- muscle mass increases rapidly in boys up to about age 17 and ultimately accounts for 54% of men's body weight
- girls add muscle mass only until age 13, average and muscle mass make up 45% of women's weight
- the large sex differences in muscle mass involve upper body musculature more than leg musculature
- the rate of growth in arm musculature is nearly twice as high for males as for females, but the difference in calf muscle growth is relatively small
49
childhood and adolescence: adipose system
- some fat is needed for energy storage, insulation and protection
- fat increases rapidly until age 6 months, then gradually until age 8
- in adolescence, girls increase fat more dramatically than boys do
- growth is by hyperplasia and hypertrophy, the latter more dramatic in adolescence
- individual variability is great
- individual fatness varies widely during infancy and early childhood
- a baby with a large amount of adipose tissue will not necessarily become a fat child
- after 7 to 8, it is more likely that individuals maintain their relative fatness
- an overweight 8 year old has a high risk of becoming an overweight adult
50
fat distribution
- body fat distribution changes with growth
- children have more internal (visceral) than subcutaneous fat
- subcutaneous fat increases from age 6-7 until age 12-13 in boys and girls
- subcutaneous fat then continues to increase in girls
51
endocrine system and important hormones
- this complex system plays a role in regulating growth and maturation through hormone
- excess or deficiency can alter growth
- major hormones involved in growth include:
- growth hormone, produced by pituitary gland
- thyroid hormone, in addition to growth also regulate weight, energy, temperature and metabolism
- two gonadal hormones, androgens and estrogen
- these hormones stimulate tissue building
52
location of endocrine glands
- organs that make and release hormones that do a specific job in your body
- endocrine glands release the substances they make into your blood stream
- pituitary gland is located in the brain
- thyroid gland is located in the neck
- testes and ovaries located in the abdomen
53
growth hormone
- growth hormone is secreted by the anterior pituitary gland
- it is necessary for normal growth
- deficiency can result in growth abnormality
54
thyroid hormones
- these are secreted by the thyroid gland
- they influence whole body skeletal growth
55
gonadal hormones
- influence on growth, sexual maturation (sex organs and secondary sex characteristics) through growth plate closure, fat accumulation, and muscle mass
- androgens: a group of hormones, most common testosterone
- more in males, associated with male reproduction
- secreted by the testes (boys), adrenal glands (boys and girls), and ovaries (girls)
- estrogen: secreted by the ovaries (girls) and adrenal cortex (boys)
- more in females, associated with female reproduction
56
childhood and adolescence: nervous system
- brain growth increases rapidly after birth, at birth brain is 25% of adult weight, by age 4 it is 80% of adult weight
- growth involves these factors:
- increase in size of neurons
- prolific branching to form synapses
- increases in glial cells for support and nourishment of neurons
- increases in myelin to insulate neurons
- stimulation of learning increases the number of synaptic connection
57
susceptibility to extrinsic factors
| impact of stimulation and learning
- rats raised with much stimulation grew significantly more synapses than those raised without stimulation
- learning is one the the most significant extrinsic factors influencing postnatal development of the nervous system
- we now know that the brain restructures itself with learning
- from the early weeks of life and continuing over the lifespan, neural connections and pathways that are stimulated are strengthened whereas those not used are weakened
58
susceptibility to extrinsic factors: nutrition
- poor nutrition in the first 1,000 days can cause irreversible damage to a child's growing brain
- long-term affects school, income, and poverty cycle
- it can also set the stage for later obesity, diabetes, and other chronic diseases
59
the first 1,000 days and the nervous system
- the brains window of opportunity
- how well or how poorly mothers and children are nourished and cared for during this time has a profound impact on a child
- a child who is read to, talked to, sung to, played with, is not only happier today, but will have a better cognitive capacity, better chance to live a fuller, more productive life
- violence, neglect, and traumatic experiences produce high levels of cortisol - a hormone that trigger the "fight or flight" response
- when cortisol levels remain high for too long, they produce toxic stress, which limits brain connectivity in children
60
first 1,000 days video
- affection, attachment, learning, stimulation
- if these are missing in the first 1000 days, there is a strong connection to long-term health issues such as chronic and infectious disease
- long-term cost for that child and society in healthcare and criminality
- the link between poverty and adverse child growth and development are high
- poverty of finance, love and support
61
saving brains
| first 1000 days, stimulation, catch-up growth and types of stress
- 1/3 of world's children never reach full potential, stunted growth
- genes are important, but growth changes with experiences, especially during first 1000 days
- ripple effect of brain connectivity, better academic success
- positive stress - occurs in context of healthy support, helps them learn to cope with life's stress
- extraordinary stress - tolerable, unexpected death, serious illness, still buffered by support system
- toxic stress - child abuse, neglect, maternal depression, no buffering by social system, much weaker platform to grow from
- stimulation - develop cognitive and social skills, developing secure attachment, create platform for more brain growth
- providing nutrition and stimulation caught up with peers growth curves, half the drop out rate, generate 25% more income
- babies with skin to skin contact has shorter hospital stays, less death and better growth curves
- starting early combo of play and connection with infants, children and teens can change outcome, its never too late
62
adulthood: skeletal system
- bone undergoes remodelling throughout the lifespan
- old bone is absorbed; new bone is formed
- in adulthood, bone growth slows, fails to keep up with reabsorption
- bone becomes more brittle in older adulthood
63
skeletal structure in adulthood
- structure itself changes little unless one has osteoporosis
- osteoporosis leads to rib cage collapse, stooped posture, and reduced height
- extent of bone loss is influenced by hormone levels, diet and exercise
64
adulthood: muscular system
| muscle mass
- loss of muscle mass is minimal until age 50
- by 80, on average 30% of muscle mass is lost. The extent of loss varies greatly, individuals who maintain a good diet and participate in resistance exercise lose far less muscle than others do
- the heart's ability to adapt to an increased workload declines. This might relate in part to degeneration of the heart muscle, a decrease in elasticity, changes in the fibres of the heart valves due to the build up of calcium deposits
65
adulthood: adipose tissue
- both men and women tend to gain fat during adulthood, but this is not inevitable
- the average weight gain from adipose tissue is 1.1 -2.2 pounds per years from early to middle adulthood for an average of 22 pounds for women and 19 pounds for men
- increases in trunk fat are notable, abdominal fat is associated with many diseases
66
adulthood: endocrine system
- imbalances may develop
- thyroid disorders are more prevalent:
- a long-term increase in thyroid hormone levels can be related to congestive heart failure
- insufficiency of thyroid hormone, or hypothyroidism, is associated with acceleration of aging systems
- older adults need to be screened
- decreasing gonadal hormone levels are associated with loss of bone and muscle tissue -> hormone replacement therapy to manage symptoms and reduce impact
67
adulthood: nervous system
- traditional view is that aging brings about loss of neurons
- new imaging techniques document neurogenesis
- exercise and stimulation promotes improved cognitive function
- regular vigorous exercises maintains the level of blood flow to the brain, lessens the loss of dendrite, stimulates neurogenesis, and promotes new synaptic connections
68
big picture implication of aging
- aging has an impact on all human systems and is a factor that constrains movement, both structural and functional constraint
- environmental and individual- functional constraints make a huge difference
69
strength and flexibility
- strength and flexibility are big constraints to movement
- leg strength is a rate limiter for infant standing
- older adults who have difficulty climbing stairs after they have lost leg strength
- gymnasts and high jumpers work on their flexibility to perform skills
- senior golfers sometimes exhibit swings that reflect a loss of flexibility
- athletes are at their best when they are strong and supple
- training that promotes increased muscle mass at the expense of flexibility puts athletes at risk of injury
- muscle balance is the goal of training today, functional strength training
- muscle strength should be build for all directions of joint movement, and flexibility through the appropriate and full ROM should be fostered
70
muscle mass and strength
- strength is the ability to exert force
- muscle mass growth follows a sigmoid pattern: rapid growth followed by a plateau and rapid growth again
- strength increases as muscles grow, but it is not a perfect 1:1 relationship
- neurological factors are also involved: what muscles are recruited? Firing the correct muscles to contract? In what order?
71
developmental changes in strength
- strength increases as children grow
- boys and girls are similar in strength levels until ~13 years of age
- boys experience a spurt of increased strength in adolescence, whereas strength increases steadily in girls
- peak strength increases follow peak muscle increases
- among same-size children of different ages, more mature children are stronger
- endocrine function probably influences strength -> increasing hormone levels positively effect muscle fibres
- neural factors likely exert influence, including improved motor unit activation with maturation
72
strength in adolescence and young adulthood
- males add more muscle mass in adolescence
- males are generally stronger, especially in the arms and shoulders
- size does not account for all gender difference: cultural norms can affect motivation and habitual activity levels
- after maturation, increases in muscle mass are solely associated with resistance training
73
strength training in children
- prepubescent children can increase strength with training, even without an accompanying increase in muscle size
- improves neuromuscular coordination plays a role: the CNS' ability to fully activate the muscles
- youths should be monitored to avoid injuries
74
should kids do strength training?
- study: prepubescent boys were observed for 2 years, a twice-weekly resistance-training program, only one minor injury occurred, and there were no different in height compared with the non-training group
- close supervision of training programs is prudent, especially programs using free weights
- no loss of flexibility with resistance training
- benefits with little risk if done right
- resistance exercise has become a common part of curricula in some elementary schools
75
exercise design for children
- kids often lack motivation to strength train the way adults do
- need to gamify it for children to enjoy it
76
strength in middle adulthood
- strength generally declines gradually after the 30s
- associated with muscle atrophy and loss, called sarcopenia, caused by malnutrition, age, lack of physical activity, and genetics
77
strength in older adulthood
- increased sarcopenia
- muscular coordination factors might be involved in declining strength
- some older adults do not lose strength
- loss of strength is greatly affected by exercise and activity levels
78
development of strength: summary
- childhood is a period of steady increase in strength
- adolescent girls continue a steady increase
- adolescent boys experience a large spurt of growth in strength at around 13
- strength levels are stable in young adulthood
- strength declines in older adulthood, gradually at first
- training can improve strength throughout the lifespan
- strength is related to muscle mass and neurological factors
79
flexibility
- flexibility is the ability to move joints through a full range of motion
- it can benefit sport and dance performance
- limited flexibility can be a factor in injury
- flexibility is specific to each joint, athletes tend to increase the flexibility of joints they use in their sports, whereas people with professions who spend much of their time in one posture may lose flexibility in some joints
80
developmental changes in flexibility: infant and childhood
- infants and toddlers are very flexible
- babies have more flexible cartilage in the body
- as the child grows, some of the cartilage hardens and turns to bone, and some bones fuse together. A child's bones are more flexible because their chemical composition is different than that of adults bones
- kids are also more active and go through a wider range of motions daily
- studies show that declines in flexibility being in childhood
81
developmental changes in flexibility: gender differences
- girls as a group are more flexible than boys
- flexibility exercises are socially acceptable for girls
- girls participate in activities stressing flexibility
- greater joint laxity in adolescent girls after they enter puberty
- in adolescence, flexibility is variable; some people lose a significant degree. Increased body mass reduces flexibility for some or addition of muscle mass
82
flexibility in adulthood
- adults gradually lose flexibility, especially in little used joints and after age 50
- adults who maintain training for flexibility maintain their levels
83
flexibility training
- training can maintain range of motion in those with full range
- training can improve range of motion in those with limited range
84
flexibility, stretching, and injury
- it is routinely accepted that poor flexibility is related to increased injury risk and stretching is widely recommended as an injury prevention practice
- stretching is not significantly associated with a reduction in total injuries, can lead to an increase in certain injuries
85
stretching and flexibility
- many methods - all can increase flexibility
- passive, static, dynamic, and proprioceptive neuromuscular facilitation (PNF)
- passive and PNF techniques require a second person
- PNF most effective for increase in ROM
- static and passive more effective for overall flexibility than dynamic, dynamic better for pre-exercise and range of motion
- for many people, stretching is a great way to maintain healthy range of motion and posture
86
does stretching improve performance?
- evidence is sport specific
- some evidence that stretching can reduce performance in certain sports
- temporary stretching deficit - reduces explosive force
- sprinting and jumping
- primarily static stretching
- sport activities requiring increased flexibility require pre-exercise stretching to optimize the level of performance such as gymnastics, dance, ice skating or diving
- sports with limited or slower requirements of muscle stretching, such as jogging or cycling, show no positive effect of stretching on performance, injury prevention or recovery
87
does stretching reduce injuries?
- high levels of flexibility can result in increased injury risk
- there is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates
- seniors benefit from flexibility for injury prevention
- warm-ups are good for preventing injuries
- warm-ups and stretching are also done together most often
88
cardiorespiratory fitness and children
| current trends
- the worldwide trend is toward reduced fitness
- a high percentage of children in Western societies have risk factors for heart disease
- cardio endurance reflects the ability to sustain vigorous activity
- many activities demands vigorous exertion
- many children today cannot sustain vigorous physical activity
89
physiological response to prolonged exercise: aerobic
- aerobic exercise: exercising at an intensity in which you're able to take in enough or more oxygen than you need
- continuous movement fuelled by oxygen from the air you breathe
- body uses oxygen to make ATP, a molecule your cells use for energy
- glucose reacts with oxygen to form ATP, and also CO2 and water
- body uses oxygen to make ATP to fuel muscles to move you
- increasing cardiac output increases the ability to sustain exercise
- training increase your cardiac output
90
how can some people sustain more aerobic exercise than others?
| factors impacting cardiac output
- cardiac output (SV x HR) - how much blood (litres) your heart can pump out in a minute
- supplies muscles, tissues, and brain oxygen to work
- average healthy person at rest is 5L/min
- during exercise, your body needs a higher cardiac output, because your muscles need more oxygen
- stroke volume (SV) - the amount of blood your heart sends to your body in one heartbeat
- increase stroke volume by 1. pumping more forcefully, or 2. increasing the amount of blood that fills the left ventricle before it pumps it out
- left ventricle gets larger and stronger with aerobic exercise, so can fill with more blood and contracts more forceful
- heart rate (HR) - the number of heartbeats per minute
- well-trained athletes can achieve higher heart rates during exercise, and will have lower resting heart rates than the average person
- your body can change its cardiac output by adjusting your heart rate and stroke volume
- cardiac output may increase to 35 L/min in highly trained athletes
91
physiological responses to short-term exercise: anaerobic
- during brief intense activity, oxygen reserves and energy sources are depleted quickly, you cannot get enough oxygen to the muscle to do the high-demand exercise
- a high-intensity movement is fuelled by energy stored in the muscles, produces ATP by breaking down glucose through glycolysis, doesn't use oxygen
- this system provides enough ATP for 1-3 minutes of intense activity when adequate oxygen isn't available
- as exercise period lengthens, the anaerobic system contributes less, and the aerobic system takes over
- ex. 100m sprint, heavy weight low rep weight lifting, plyometric, 800m race
92
children have a smaller output of absolute anaerobic power
- children have less anaerobic power output than adults
- muscle mass is smaller
- absolute quantities of energy reserves are smaller
93
developmental changes in anaerobic performance with growth
- energy reserves increase, muscle mass increases
- tolerance of by-products of metabolic process (lactic acid)
improves
- anaerobic power improves
94
individual differences in anaerobic performance
- more mature children have better anaerobic performance
- improves coordination contributes to improved performance of anaerobic actitvities
95
changes in aerobic performance during childhood
- children have smaller stroke volume and thus smaller cardiac output
- children compensate in part with higher heart rates
- children have lower concentration of hemoglobin, the blood protein that carries oxygen
- children have an efficient system but cannot exercise for as long as adults can
- with growth and maturation the following occur: heart size increase and hemoglobin concentration increases
- ability to sustain exercise is related to body size and maturity level
- by late adolescence and into adulthood, trained men have an advantage over trained women
96
anaerobic and aerobic training responses in children
- significant influences of training status being evident for aerobic or anaerobic outcomes
- the magnitude of these influences is considerably smaller than is typically reported in adults
- overload principle: posits that the amount of exercise performed in a training program must exceed what the participant is accustomed to in order for adaptation to occur
- the influence of training status is independent of maturity stage, suggesting that significant effects of training can be elicited even before puberty
- undetermined if commencing intensive training during pre-puberty is associated with greater benefit during adulthood than commencing intensive training at a later maturity stage
- any potential benefit would need to be balanced with the increased chance of burnout or injury which is associated with intensive training at a young age
97
anaerobic performance in adulthood
- improvement reflects training alone
- in older adulthood, a loss of muscle mass and type II muscle fibres can result in declining anaerobic performance
98
aerobic performance in adulthood
| maximal oxygen uptake
- without training - average maximal oxygen uptake per kg of body weight falls about 1% per years after the 20s, decrease in maximum heart rate and muscle mass
- adults benefit from aerobic training because it minimizes the decline in performance that would otherwise accompany aging
99
cardiovascular structure and function
| changes occurring in adulthood
- changes occur in structure and function in adulthood:
- loss of cardiac muscle
- loss of elasticity in cardiac muscle
- thickening of left ventricle
- fibrotic changes in valves
- loss of elasticity in major blood vessels
100
long-term training effects
- research is limited, especially longitudinally
- women with more physical education/activity in their youth exercised more frequently in adulthood
- youth sport participation predicts young adult activity levels, earlier participation in aerobic predicts aerobic function later in life: possibly through maintenance of the plasticity of physiological systems and lifestyle choice
101
almost all motor acts are perceptual motor skills
- human movement is based on information about the environment and one's position or location in it
- ex. a softball infielder sees the location of the pitch, the batter striking the ball, and the ball bouncing on the ground, hears the hit, and perhaps sees a runner on the base path, and feels the position of her body and arms
- the infielder uses this information to decide where and when she can intercept the ball, where to move and how to position her body
102
sensation vs. perception
- sensation occurs when sensory receptors detect sensory stimuli
- perception involves the organization, interpretation, and conscious experience of those sensations
103
sensory systems
- function as individual constraints
- visual, kinaesthetic, and auditory senses
104
acuity
- acuity is the sharpness of sight, enables us to distinguish shapes and details of objects
- in the first month, acuity is 20/400, 5% of the adult level making it difficult for babies to see edges of objects and distinguish shapes
- infants can differentiate facial features at 20 inches
- acuity is approx 20/30 by age 5, and 20/20 by age 10
105
visual development: sensation
- vision plays a major role in most skill performance
- by 6 months of age, vision is adequate for locomotion through the environment
- nearsightedness more common than farsightedness meaning its easier to see things up close than far away, causes image to be focused behind retina
106
visual changes with aging
- declines in vision have implications for skill performance and everyday living tasks, such as driving and reading
- presbyopia affects ability to see nearby images, can be corrected with lenses, becomes clinically significant at around age 40
- older adults need more light to see clearly in dim environments
107
visual perception
involves perception of space, object, and movement
108
perception of space
- space perception requires perception of depth and distance
- cues about depth and distance in our environment are often derived from the two eyes being in different location or from movement of the head
- eyes view different images and your brain combines them to form a single image
- as your head moves left, closer objects move right (opposite direction of head), while farther objects move left (same direction of your head)
108
development of space perception
- by 6 months, infants perceive depth
- children may err in judging depth until near-adult levels are reached in early adolescence
- the number of older adults who fail depth perception tests is greater than the number of young adults
109
perception of objects
- a process where visual input is assigned a meaningful interpretation that is available to perceptual awareness
- object attributes are size, shape and motion
- perception is base on information about edges, helps us extract an object or figure from the background environment, distinguish whole objects from parts of an object
110
distance and object perception interact
with adequate visual perception, perceived objects retain size even if retinal image size changes because of change in distance from observer to object
111
perception of motion
- infants perceive motion
- perception of direction and velocity of motion improve during infancy, some animals predominantly sense movement
- rhinos can't differentiate between a human and a tree at 15ft away
- crucial to motor development
112
kinaesthetic system
- the kinaesthetic sense gives us "body sense"
- it is vital our ability to position ourselves, move in our environment and identify the objects we contact
- kinesthesis also provides our sense of force, heaviness, and effort
- to know the importance of kinaesthesis, you need only recall walking through a fun house at a fair, where you visual system and your kinaesthetic system are given conflicting information
113
kinesthetic development: sensation
- kinesthesis arises from proprioceptors, collective name of the various kinesthetic receptors located in the body
- there are two overlying types of proprioceptors:
- somatosensors: located under the skin, in the muscles, at muscle-tendon junctions, and in joint capsules and ligaments, they are what makes us feel touch, pain, temperature
- vestibular apparatus: houses the apparatus located in the inner ear, allows us to detect the position and movement of our head in space, enable hand-eye coordination, posture, equilibrium
114
kinesthesis in infancy
- receptors probably function prenatally
- newborns respond to touch and can locate touches to the face, necessary for breastfeeding
- the vestibular apparatus functions by 2 months, if not earlier
115
kinesthetic changes with aging
- kinaesthetic sense declines with age
- some older adults experience loss of touch sensitivity
116
kinaesthetic perception
- involves perception of these elements:
- tactile localization, manipulation and movement, moving our hand to touch and/or manipulate something, and identifying what it is
- body awareness
117
tactile localization
- the ability to identify without sight the exact spot on your body that has been touched
- newborns can feel touches, needed for breastfeeding
- perception of touch location improves in early childhood
118
manipulation and movement
- in infants manipulation is more accidental than purposeful
- manipulation becomes more methodical around 6 years
- object recognition, and speed of recognition improve in childhood
- between 5 and 8 years, there is great improvement in perception of the extent of a movement
119
body awareness
| identifying body parts and preferences
- identifying body parts: children improve in labelling, 2/3 of 6 year olde can identify the major body parts and mistakes are rare in all typically developing children after age 9
- preferring one eye, ear, hand, or foot over the other, infants show preferences, handedness is established around age 4
- pure dominance: favoured side is the same for all body parts
mixed dominance: favoured side is not consistently the same
120
handedness advantage in sport
- in many sports left handedness is an advantage
- negative frequency-dependent selection (NFDS) effect
- left-handed people have high health risks, including breast cancer and psychotic disorders
- fighting hypothesis: maintained in the population because they have an advantage in fights
- unfamiliarity: can catch right-handers off guard or by surprise
- time-constrained sports and reaction time: baseball, cricket, table tennis, tennis and volleyball
121
kinaesthetic changes with aging
- some sensitivity may be lost
- proprioceptive acuity declines, eg. ability to sense joint position, discriminate movement of limbs individuals and relative to each other
- impairments in lower limbs might play a role in loss of balance
122
audition in infancy
- the absolute threshold is about 60 db higher for a newborn than for an adult, so a newborn can only detect an average speaking voice when an adult can detect a whisper
- rapid improvement is seen in the first week
- at 3 months, infants hear low-frequency sounds well
123
auditory changes with aging
- hearing loss is more frequent in older adults
- some loss due to physiological deterioration, changes to auditory nerve and inner ear
- some loss might result from lifelong exposure to environmental noise
- exposure in childhood to loud and chronic noise can cause hearing loss for life
- individuals are born with a fixed number of cochlear hair cells, they do not regenerate and are killed by excessive noise exposure at any point in the lifespan resulting in permanent hearing loss
- hearing amid a noisy background is more difficult
KIN 280
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