notes Flashcards
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Functions of the Skeleton
Provides a supporting framework for the body.
• Provides attachment points for muscles, creating a lever system that enables body movement.
• Provides protection of vital organs.
• Blood cell formation – red bone marrow produces red and white blood cells and platelets. Bone is richly supplied with blood vessels.
• Mineral storage – calcium and phosphorus.
Structure of Bone
-major building blocks of bone are calcium carbonate, calcium phosphate, collagen fibers, and water. Collagen is a protein that is the main organic constituent of connective tissue.
-Bone tissue is composed of widely separated cells, called osteocytes, surrounded by matrix. The matrix is about 25 % water, 25 % protein, and 50 % mineral salts.
collagen
acts ad rebar
increases strength
increases flexibility
Hence the 3 major cells of bone
osteocytes: mature bone cells
osteoclasts: reabsorb or break down bone
osteoblasts: bone forming cells
bone growth
During bone growth osteocytes, around a blood vessel, lay down bone matrix (lamella) in a concentric fashion to form the basic building block of bone: the osteon.
Bone is highly dynamic and is continually being remodeled in response to mechanical stress or even absence of stress.
The remodeling is caused by a continual process of bone breakdown (resorption) via osteoclasts and bone formation via osteoblasts.
long bones
humerus
short bones
trapezoid, wrist bone
flat bones
sternum
irregular bones
vertebra
sesamoid bone
patella
Vertebral
The vertebral column provides flexible support for the trunk and protects the spinal cord.
- 33 vertebrae; 26 distinct bones
- 5 segments
- 7 cervical vertebrae
- 12 thoracic vertebrae
- 5 lumbar vertebrae
- 5 sacral vertebrae
- 4 coccygeal vertebrae
functional unit of vertebrae
The vertebrae articulate with one another by means of facets on the processes of the neural arches (synovial joint) and by means of intervertebral discs between the vertebral bodies (cartilaginous joint).
The discs function as shock absorbers and allow slight movement so that the column is flexible and resilient and the discs reduce friction. Furthermore, like the cartilage in a synovial joint, when put under impulsive forces, the cartilage prevents bone on bone contact and since bone is highly vascular and cartilage is not, you do not bleed out.
Abnormal curves:
- Scoliosis - an abnormal lateral curvature of the vertebral column.
- Kyphosis - “hump back” - an exaggerated posterior thoracic curve.
- Lordosis - “sway back” - an exaggerated anterior lumbar curve.
Sexual Differences
On average, women tend to have relatively broader hips creating a larger oval-shaped pelvic inlet whereas men have a smaller heart-shaped inlet.
Women also have a great Q angle (the angle formed from the patella between the femur and vertical).
Classification of Joints
1. Fibrous joint - immoveable
This classification system is based on anatomy. Note that when bones are joined, they actually never touch. It is the material in between that determines the anatomical classification.
-cpr without breaking rips and help to breath better
Synovial fluid
two functions
a) Lubricates the joint surfaces as they slide over each other during joint movement.
b) Supplies nutrients to, and removes waste products from, the cartilage cells which have no direct blood supply.
Ligament
fibrous connective tissue that connects bones together.
Tendon
fibrous connective tissue that joins muscle to bone.
Bursa
a small sac or cavity filled with synovial fluid and located at friction points, especially joints. Most bursae are located between tendons and bone.
Reference Planes
Frontal plane – divides body into anterior and posterior portions
Sagittal plane – divides the body into right and left sides
Transverse plane – divides the body into superior and inferior portions
terms of direction
(in lab)
relative terms
joint movements
These movements are related to the body as seen in anatomical position.
1. Flexion, extension
2. Abduction, adduction
3. Rotation - inward (medial) rotation; outward (lateral) rotation
4. Supination, pronation
5. Elevation, depression
6. Plantar flexion, dorsiflexion
Common Joint Disorders
- Sprain (not strain): three degrees of severity
-ankle inversion most common injury in sports - Dislocation
- Subluxation
- Bursitis
- Arthritis
Structural Limits To Flexibility
- Bony structure of the joint - can’t be changed by a flexibility program
- Ligaments
- Joint capsules
- Muscle-tendon unit - muscle and its fascial sheaths - the major focus of stretching exercises is the elongation of this tissue.
SOMATOTYPE
The somatotype is a quantitative description of the present structure and composition of the body. This method of physique classification was developed by W.H. Sheldon in the 1920’s to 1950’s.
The real value of somatotyping lies in its contribution toward a better understanding of the individual.
I. Body Image
Body image - the picture an individual has of her own body that she forms in her mind.
Individuals assign qualities of size, shape, and attractiveness to their bodies in terms of personalized standards that may bear little relation to actual body characteristics.
Some people love and parade their bodies; others are ashamed of their bodies and hide them.
The primary determinants of body appearance are (a) the skeleton (b) muscle (c) fat
Sheldon’s somatotype
Sheldon designated three primary components of body build:
(1) Endomorphy - refers to the relative predominance of soft roundness throughout the body.
(2) Mesomorphy - refers to relative predominance of muscle, bone, and connective tissue.
(3) Ectomorphy - refers to the relative predominance of linearity and fragility.
Sheldon rated each component on a seven-point scale to indicate it’s relative contribution to the total physique. This three numeral rating of a physique is called the “somatotype”.
First numeral = endomorphy Second numeral = mesomorphy Third numeral = ectomorphy
Most physiques are dominated by two components.
641 = mesomorphic endomorph
461 = endomorphic mesomorph
244 = mesomorph - ectomorph
333 = balanced
Male versus Female Somatotypes
On a somatoplot, the distribution of female physique types differs from the male distribution of physique types – sexual dimorphism.
Females are more endomorphic and less mesomorphic than males.
1976 – 1978 Canadian data. Refer to page in 3-18 in Laboratory Manual. Average somatotypes for males and females aged 15 to 60 years:
Males: 3.9 – 5.2 – 1.9
Females: 4.7 – 4.0 – 2.2
Physical Performance and Somatotype
Both male and female athletes are more mesomorphic and less endomorphic than non-athletes of the same age.
There are characteristic somatoplot distributions for each sport. The higher the level of sport the lower the variation in somatoplot distribution.
Some sports are more tolerant of somatotype variation than other sports.
A high mesomorphy is positively correlated with physical fitness tests and endomorphy is negatively correlated.
Strength and speed-dependent athletes are more mesomorphic and less ectomorphic than distance-dependent athletes.
Very seldom do men and women low in mesomorphy succeed at a high level in sports.
Methods of Determining Somatotypes
Several systems of somatotyping have been developed. The Sheldon method and the Heath-Carter method have been the most widely used.
The Heath-Carter method has been extensively used on samples of athletes.
In the Heath-Carter method, the rating scale was opened at the top end, from 7 to 12, to accommodate extreme body types.
The somatotype doesn’t tell you anything about a person’s height, or about body proportionality - trunk length vs leg length, etc.
Physiognomy
is a theory based upon the idea that the assessment of the person’s outer appearance, primarily the face, may give insights into one’s character or personality.
body composition
two-component model - the amount of fat and fat-free mass of which the body is composed. Fat-free mass is primarily composed of bone, muscle, vital organs, and connective tissue.
Four-component model - fat, protein, mineral, water
Anthropometry
quantitative measures of selected human landmarks.
Why assess body composition?
•Suitable body composition is important for health.
•Establish reasonable fatness ranges for athletes in various sports
•Accurate measures of body composition are needed to develop sound weight reduction programs
•Knowledge of bone mineral content in women and children is important.
•Monitor changes in body composition associated with disease.
I. Essential Fat vs. Storage Fat
Essential fat - fat that is required for normal physiological functioning - structural components of cell membranes, required for the synthesis of certain hormones, transport of fat-soluble vitamins, etc.
Storage fat - fat that is stored in adipose tissue for energy supply purposes. It is located underneath the skin, in the abdominal cavity, and around certain organs.
different levels of BC measurement
level ll: molecular
level lll: cellular
level lv: tissue
level v: whole body
Body Composition of Males vs Females
The average male is taller, heavier, has a larger muscle mass, and a lower total body fat content.
Female has sex specific fat depots in the breasts, pelvic and thigh regions, and probably other areas.
For reference male and female, age 20 - 24:
Storage fat
- female = 15%
- male = 12 %
Essential fat -
female = 12 %
- male = 3 %
“male type”
obesity - excess fat is deposited on the upper torso and around the abdomen. Male type obesity appears to be associated with higher health risks.
“female type”
obesity - excess fat is deposited below the waist in the thighs, hips, and buttocks, i.e., pear shape.
obesity facts
Weight gain and obesity occur when energy intake exceeds energy expenditure.
Data from overfeeding experiments with identical twins demonstrate that some individuals are more at risk than others to gain fat when energy intake surplus is maintained at the same level for everyone and when all subjects are confined to a sedentary lifestyle.
NEAT – non-exercise activity thermogenesis. It is the energy expended by physical activities other than planned exercise – sitting, standing, walking, fidgeting, etc. In a recent research study, obese participants were seated for 164 minutes longer per day than were lean participants.
Common Techniques For Assessing Body Composition
Direct methods - chemical analysis of human cadavers
Indirect methods - noninvasive techniques used on living persons
Height - Weight Tables
Desirable weight with regard to the lowest death rates is predicted from tables that have been developed by insurance actuaries.
Criticisms:
(1) These tables do not consider body composition.
(2) Most of the data in the 1983 Metropolitan Life Insurance Height-Weight tables come from white, middle-class, U.S. adults aged 25 to 59 years. This is not a representative sample of the general North American population.
(3) No accepted method has been devised for determining frame size.
diet quality
structural plants + reproductive plants + animal plants
DQ is proportionate to brain metabolic rate
The brain is about 2 % of body weight yet accounts for about 20 % of resting metabolic rate
using less energy on the rest of the body and feeding our brain
Body Density and Volume Measurements
Density = mass/volume. Body density will vary with the amount of body fat.
After body density has been determined using one of the above methods, use an equation to determine percent body fat.
These equations make two basic assumptions:
(1) The human body has two compartments - fat and nonfat
(2) Each of these compartments has densities which are known constants. Assume that fat has a density of 0.90 g/mL and nonfat a density of 1.10 g/mL.
hydrostatic weighing
For decades hydrostatic weighing has been used as a universal method for validating skinfold caliper formulae and all other methods, i.e., it has been used as the “gold standard”.
Problems:- cadaver studies (Brussels cadaver study, 1984) have shown that the density of the nonfat compartment varies as a function of age, sex, and racial group.
Therefore, a nonfat density value of 1.10 g/mL is not universally applicable.
Conclusion - densitometry should not be used as a universal criterion for prediction of percent fat. Equations based on four component models are preferred.
Weight - Height Indicies
Body Mass Index (BMI) - used as an indicator of obesity. This index uses the body mass (kg) divided by the height (meters) squared.
Recent research evidence indicates that these BMI cut-off points may need revision because the relationship between BMI and body composition, and between indices of fat distribution and the actual amount of visceral fat may differ across ethnic groups. For example, Asian populations have a higher body fat percentage at a lower BMI compared to Caucasians.
Criticism - BMI does not differentiate body composition.
BMI of Mike Tyson = 31
Classification system for adults (20-70 years old):
BMI less than 18.5 = underweight
BMI of 25.0 to 29.9 = overweight
BMI of 30 or 34.9 = obese class 1
BMI of 35 or 39.9 = obese class 2
BMI of 40 and higher = extreme obesity
The prevalence of overweight and obesity amongst Canadian children and adults has increased significantly in the past 20 years. From 1981 to 1996, the prevalence of obesity in children tripled from 5 % to 15.5 %.
Skinfold Measurements
Rationale - a relationship exists between the fat located in the depots directly beneath the skin and internal body fat and body density.
There are basically two ways to use fatfolds:
(1) Use the sum of a number of skinfolds as an indication of relative fatness among individuals. Also compare “before” and “after” in the same individual.
(2) Use fatfolds in conjunction with equations or tables to predict percent body fat.
Skinfold caliper formulae to predict percent fat are site and sample specific.
Assumptions in using skinfold measurements to predict percent fat:
(1) Constant densities in a two-compartment model
(2) Proper identification of measurement site and proper measurement technique
(3) Constant compressibility of the skinfold
(4) Fixed adipose tissue patterning
(5) Fixed proportion of internal to external fat
There are two types of body composition prediction equations:
1) Population specific equations - developed from relatively small, homogeneous (age, sex, state of training, fatness) samples. Their application is limited to that subsample.
Example – Sloan, Yuhasz
(2) Generalized equations - developed from large, heterogeneous samples. These equations have a wider application in terms of age, and fatness. However, these equations should be used cautiously with unique populations such as extremely obese individuals and professional football players.
Example - Jackson and Pollock, Durnin & Womersley, Peterson, Wang
Even when the correct equation is used and the measurements are performed correctly, prediction of percent fat from skinfold measurements has an error of about 3-4 %.
BMI is good because?
Used by CDC, WHO, etc
Many relations to health
Used also for growth and development
Measures are easy to take
Measures are cheap
Measures are reliable
Measures are objective
It is reasonably independent of height
Canadian Physical Activity, Fitness and Lifestyle Appraisal
This method requires the consideration of three different indicators for a comprehensive assessment of body weight, adiposity, and fat distribution.
(1) Body mass index – is the subject overweight?
(2) Sum of 5 skinfolds - triceps, biceps, subscapular, iliac crest, and medial calf. Is the subject over-fat?
(3) Waist girth – is the subject high in visceral adiposity – male type obesity?
O-Scale System
Adiposity rating, proportional weight rating, stanine scale
Bioelectrical Impedance Analysis
Electrical impedance units are used to measure the electrical resistance of the body.
Impedance is greater in adipose tissue (14 - 22 % water) than in bone and muscle (71 - 75 % water).
Attach electrodes to the subject. A low level electrical current (500 to 800 microamps at 50 kHz) is passed through the subject’s body. The higher the electrical resistance, the more fat the subject has.
Near-Infrared Interactance (NIR)
NIR is still in the developmental stages and there is much skepticism surrounding the use of NIR to assess body composition.
Principle - the degree of infrared light absorbed and reflected is related to the composition of the tissues. Optical densities are linearly related to subcutaneous and total body fat.
The biceps is the best single site for estimating body fat using this method.
Other Procedures for body measure
- Dual energy X-ray absorptiometry – widely used for performing bone mineral density measurements
- Total body water – hydrometry
- Ultrasound
- Magnetic resonance imaging
- Computerized tomography
- Total body potassium
These laboratory methods are reasonably accurate but they are expensive, cumbersome and require highly trained technicians.
Conclusion - results of estimation of body composition should be interpreted cautiously
Body Composition and Aging
Changes associated with aging in western society:
• increased fat mass (creeping obesity)
• decreased muscle mass - sarcopenia
• decreased bone mass
These changes can be slowed down by a regular exercise program and proper dietary habits.
Recent evidence indicates that skeletal fragility in elderly women is related to failure to obtain an optimal level of bone mass during childhood.
sarcopenia: banishing flesh, the older you get, the less flesh you have
Co-morbidities/Complications Associated With Obesity
Type II diabetes mellitus
Hypertension
Coronary artery disease
Stroke
Sleep apnea: stop breathing for 20-40 secs
Gallbladder disease
Osteoarthritis of the weight-bearing joints
Gout
Reduced fertility
Impaired obstetric performance
Reduced physical agility
Co-morbidities/Complications Associated With Excessive Thinness
Fluid-electrolyte imbalances
Osteoporosis
Bone fractures
Muscle wasting
Cardiac arrythmias and sudden death
Peripheral edema
Renal disorders
Reproductive disorders
Growth
“the progressive development of a living being or part of an organism from its earliest stage to maturity, including the attendant increases in size”.
maturity: how close we are to the endpoint
Nature of Growth
Growth involves a series of changes not just the addition of material to achieve an increase in size. These changes involve a differentiation of various parts of the body to perform different functions.
-Not all parts of the human body grow at the same rate, nor do they all stop growing simultaneously.
-The body does not retain the same proportions throughout growth and the relative weights of given tissues and organs do not remain constant.
-the brain at birth is about 24 % of its adult weight, whereas the neonatal body is only about 6 % of its adult weight.
-Extremely rapid growth of the brain continues, so that by the time the child is five years old the brain has reached 90 % of its adult weight, whereas its body weight is only 25 % of its eventual adult weight.
-The reproductive organs, on the other hand, remain at less than 10 % of their final weight until the onset of puberty.
Stages of Postnatal Growth
- Neonatal Period - extends from birth to the end of four weeks.
- Infancy - extends from the end of the neonatal period at four weeks until two years of age. Infancy is characterized by tremendous growth, increased coordination, and mental development.
- Childhood - the period of growth and development extending from infancy to adolescence, at which time puberty begins. The chronological duration of childhood varies because puberty begins at different ages for different people. Childhood years are a period of relatively steady growth until preadolescence when there is a growth spurt.
- Adolescence - the period of growth and development between childhood and adulthood. It begins around the age of nine in girls and the age of eleven years in boys. The end of adolescence is approximately 17-18 years, but it is not clearly delineated.
- Adulthood - the period of life beyond adolescence. An adult has reached maximum physical stature as determined by genetic, nutritional, and environmental factors.
Growth Curves
Distance curve - measurements taken at intervals are plotted against time to produce a graph of progress.
Velocity curve - increments in growth are plotted against time to show the variation in the rate of growth with time.
Longitudinal data - growth curve is derived from a single individual or from repeated measurements on the same group of individuals over a period of many years.
Cross-sectional data - measurements are made of several children in each age group, and these are then combined to form a cross-sectional picture of the various age groups in the community at the time of the investigation.
Growth In Height
Growth is a regular process, it doesn’t proceed by stops and starts.
From birth to maturity, the most important difference between boys and girls is in the rate of maturity. Girls grow up faster than boys - they reach 50 percent of their adult height at an earlier age (1.75 vs. 2.0 years), enter puberty earlier, and cease growing earlier. Half way through the foetal period, the skeleton is already three weeks more advanced in girls; at birth, the difference is four to six weeks of maturation; at puberty, the difference is two years.
Before the adolescent growth spurt
there is little difference between the average height of boys and girls. Because the spurt begins earlier in girls, there is an age (approximately 9-10 years) at which girls become taller and heavier than boys of the same age. This balance is redressed by age 14.
The mean growth takeoff age (i.e., the onset of growth acceleration) in children in North America growing at an average rate is approximately 12 ± 1.5 years in boys and 10 ± 1 year in girls. The age at takeoff correlates highly with pubertal stage.
During the spurt, boys add approximately 20 cm to their height mostly because of growth of the trunk while girls gain about 16 cm in height.
peak height velocity
Peak height velocity in boys – 14 years
Peak height velocity in girls – 12 years
The standard deviation for age at peak height velocity is slightly less than one year. The peak height velocity is highest in early-maturing children and lowest in late-maturing children.
Since the peak height velocity may occur as much as two years earlier or later than the average within each sex, a six year difference in the event between an early maturing girl and a late maturing boy is quite possible.
The conclusion of the growth spurt
The conclusion of the growth spurt is followed by a rapid slowing of growth. In USA cross-sectional studies, boys with a mean takeoff age of 12 years reached their final heights by 17-18 years of age, and girls with a mean takeoff age of 10 years reached their final heights by 14-15 years of age. However, there is a wide variation around these means - plus or minus two years.
Boys end up being taller than girls because they have two more years of growth before the growth spurt. During these two extra years of prepubertal growth in boys, the legs are growing relatively faster than the trunk. Thus the average male has relatively longer legs than the average female.
Height can also be sued as a proxy for living standards through decades or centuries. As living standards have improved so has the average height of the population. Usually true unless there is a confounding factor of a higher death rate amongst small babies.
Growth In Weight
Weight of ovum —> birth - 3 X 109
Birth —> maturity (20 years) - 20 X
Birth —> 2 years - 4 X, then steady increase of 2 - 3 kg per year until growth spurt.
During the growth spurt, boys may add 20 kg to their weight, and girls 16 kg.
The peak velocity for the spurt in weight lags behind the peak velocity for height by about 3 months - child shoots up and fills out later.
Osteoporosis
a condition of the bones where they become thin and brittle due to decreased mineral content, which makes them susceptible to fracture.
Bone Mineral Content in Adolescence as Related to Osteoporosis in the Elderly
For all bone sites in both boys and girls, peak velocity in bone mineral content occurs approximately one year after peak height velocity. This suggests that there could be a transient period of relatively long bone weakening during the adolescent growth spurt, resulting in an increased fracture risk following peak height velocity.
The need for calcium during peak linear growth is substantial. An adequate level of vitamin D in the body is also important – effects of sunshine and diet. Vitamin D deficiency is not uncommon among children and adolescents, particularly during the dark seasons of the year.
As much bone mineral will be laid down during the four adolescent years surrounding peak height velocity as most people lose during all of adult life. Peak bone mineral density of the lumbar spine and hip is achieved around the age of 20 years.
Adolescence is a critical time for bone mineral accumulation
More than 90 % of adult bone mineral is present by the end of skeletal maturation and any gains in bone mass after growth has ceased are minimal. Fifty percent of the variability in bone mass in the elderly can be accounted for by peak skeletal mass attained during the years of growth and maturation. Therefore, the prevention of osteoporosis depends not only on reducing the rate of bone loss during adult life, but also on the maximization of bone mineral accrual during the growing years.
Changes in Body Proportions and Composition
The relation between one part and another of the growing body is not a consistent one, but changes with age.
Shape of the Infant
Large head - ratio of head height to total height equals 1:4 in the infant, 1:7.5 in the adult.
Lower limbs are much less well developed at birth than upper limbs - ratio of leg length to total height equals 1:3 in infant, 1:2 in adult.
Changes in Shape With Growth
At all ages the dimensions of the head are in advance of those of the trunk, and at all ages more peripheral parts of the limbs are in advance of the more central parts - foot –>
calf–> thigh.
The bones of the face grow faster than those of the cranial vault - “at adolescence the face emerges from underneath the skull”. In the later stages of the adolescent spurt, there is laterality of growth rather than linearity.
Puberty
refers to the period at which the testes, prostate gland, and seminal vesicles or the breasts, uterus and vagina, suddenly enlarge.
This is the time of greatest sex differentiation since the early intra-uterine months – sexual dimorphism. There are changes in reproductive organs and secondary sex characteristics, in body size and shape, and in relative proportions of muscle, fat, and bone.
males vs female puberty
Studies conducted in the USA have indicated that there are no differences in various stages of pubertal development in African American boys and white boys. However, these studies have shown a significant difference between African American girls and white girls at every stage of development.
The average age of occurrence in North America is 12.8 - 13.0 years in white girls and 12.2 to 12.5 years in African American girls. There is a standard deviation of plus or minus one year. The 95 percent range is 11.0 - 15.0 years.
All girls start to menstruate when the height velocity is falling. The development of mature ova follows menarche by as much as two years; therefore puberty is not complete in females until sexual maturity has been attained.
A research study reported in the April 1997 issue of “Pediatrics” indicated that girls in the United States mature sexually earlier than previously expected
Menarche
refers to the onset of menstruation. It occurs relatively late in puberty.
Indices of Maturity
It is important to be able to assess how far an individual child has progressed towards maturity. The chronological age of a child is an unreliable guide since children mature at very different rates and measurements of height and weight are only partially useful.
Radiological (Skeletal) Age
During growth, every bone goes through a series of changes which can be recorded radiographically. The times of appearance of primary and secondary centers of ossification can be observed and the progressive enlargement of the ossified portion of an epiphysis can be followed in detail. The radiological examination allows one to determine how far the skeleton of a child has progressed toward the adult condition. The wrist and hand are most commonly used for this purpose because, in this region, there is a large number of centers of ossification.
At every chronological age up to full maturity, the radiological age of girls is in advance of that of boys by a factor of about 20 percent or more.
Dental Age
The deciduous dentition erupts from six months to two years of age and can be used during that period. The permanent dentition provides a measure from six to 13 years of age.
Skeletal maturity and dental maturity are not closely related in the individual.
Growth Curves
The timing of the peak height velocity and the peak weight velocity are useful maturity indicators.
Sexual Age
The secondary sex characteristics can be used as a method of rating maturational development. Ratings can be made of stages in pubic hair development, stages in breast development, and stages of genital development. These indicators have limited applicability over the growth span, in contrast to skeletal maturation, which can be monitored from infancy into young adulthood.
The “Tanner” stages of sexual maturity are used as the universal standard for classifying sexual maturity.
The age at which menarche occurs is an important indicator of maturation status in females. Menarche is more closely related to radiological age (12 - 14.5 years) than to chronological age (10 - 16 years).
Neural Age
In spite of the large size of the central nervous system at birth, much of it is incompletely functional and requires considerable time to develop to the stage at which it can be fully utilized.
Girls are ahead of boys throughout the phase of motor and sensory development - on the average, girls learn to walk earlier, control their bladders earlier, and are ahead in the use and understanding of speech. They are also first in the development of skills which need fine movements and coordination, such as tying bows.
Early and Late Maturing Children
Five types of skeletal development have been recognized.
(1) Average children
(2) Early maturers - tall in childhood but not as adults
(3) Early maturers and genetically tall
(4) Late maturers - small in childhood, average as adults
(5) Late maturers and genetically short
mental and psychological developments relations
There is good evidence that, in European and North American school systems, children who are physically advanced towards maturity score, on average, slightly higher on most tests of mental ability than children of the same age who are less physically mature.
It is very likely that mental and psychological developments are much more closely related with radiological age than with chronological age.
Mesomorphic boys
on average, tend to mature earlier than others and have an early adolescent growth spurt. Late maturing boys are greatly handicapped in competition with early maturing boys. Late maturing boys may be deselected from age-class sports too early, while early maturing boys may develop unrealistic expectations and have difficulty adjusting to their loss of sports advantage when their late maturing peers catch up.
Factors Influencing Growth and Maturation
Genetic Control
Nutrition
Secular/Historical Trends
Season and Climate
Differences Between Races
Saltation and Stasis
Catch-up Growth
Genetic Control
Both genetic and environmental factors influence growth, and the progress of any given child is the result of a complex interaction of many different factors.
Studies of twins have shown that body shape and size, deposition of fat, and patterns of growth are all more closely related to nature than to nurture.
Heredity affects not only the end result of growth, but also the rate of progress toward it.
Nutrition
Malnutrition delays growth. Children subjected to an episode of acute starvation recover more or less completely provided that the adverse conditions are not too severe and do not last too long.
Adult size is affected by a less severe level of under-nutrition than adult body proportion (i.e., leg length versus trunk length, etc.)
Secular/Historical Trends
Paleontologists etc have dug up enough bones on this planet to estimate the size of humans over time. About 9,000 years ago human height decreased. This is attributed to a nutritional change to a more grain-based diet. Some vitamins and mineral important for growth would be substantially reduced.
Between 1880 and 1950, the average height of American and West European children between the ages of five and seven years increased by more than 1/2 inch per decade for a total of more than four inches. Children are now growing faster and stopping growing earlier.
There has been an upward trend in adult height of one centimeter per decade since 1880.
In Western European countries, the average age of menarche decreased from 16 years in 1880 to 13 years in 1960.
Season and Climate
There is quite a close correlation between the linearity of people as adults and the average annual temperature of the area where they live or from which they migrated in historical times. The long limbs of the Africans enable them to lose more heat per unit volume than the European, and the thick-set body and short limbs of the northern Asiatics are similarly adaptive in Arctic regions.
Contrary to popular opinion, climate has, at most, a very minor effect on age of menarche. People living in tropical countries frequently have a late menarche because their nutritional status is low.
Studies done on West European children indicate that season of the year may exert a considerable influence on velocity of growth. The children grew faster in height in spring and summer than in autumn and winter. Weight gain was faster in the autumn than in the spring.
Differences Between Races
Populations differ in their average adult size and their tempo of growth as well as their shape.
Consider three population groups - European, African, and Asiatic
Height - Asiatic boys and girls are shorter
Body proportions - compared to Europeans, Chinese have relatively longer trunks and shorter legs. Africans are the opposite. Compared to Europeans and Asiatics, Africans have slimmer hips for a given shoulder width. Africans have more muscle and heavier bones per unit weight, at least in males, together with less fat on the limbs in proportion to fat on the trunk.
Tempo of growth - well off Asiatic and African children are ahead of European children in skeletal age and dental maturity.
Saltation and Stasis
Growth occurs in a series of rapid rates interspersed by long periods of stasis. In essence, this is a synchronous display of cartilaginous tissue going through a cell, or rather, a tissue cycle.
Catch-up Growth
Catch-up growth is a remarkable phenomenon in which significantly reduced growth perturbations can be completely alleviated by proper corrective action such correcting diet or hormone deficiencies. This demonstrate the underlying genetic control of human height.
Components of Health-Related Physical Fitness
- Cardiorespiratory endurance - aerobic power
- Strength
- Muscular Endurance
- Flexibility
- Body Composition
Objectives of Physical Fitness Testing
- To assess the status of individuals entering a program.
- To aid in prescribing or limiting activity of certain individuals.
- To evaluate an individual’s progress.
- To increase individual motivation for entering and adhering to an exercise program.
- To evaluate the success of a program in achieving its objectives
Medical Clearance and Human Rights
The subject’s human rights are respected - Informed Consent Form. The subject is given a thorough explanation of the purpose of the test, possible risks, benefits, etc.
Characteristics of a Good Physical Fitness Test
Measurement error makes the observed value of a measure differ from the true value.
- Validity
- Reliability
- Objectivity
- Accuracy
- Norms
- Economy
- Validity
a valid test is one that measures effectively what it is supposed to measure.
Compare the test results to a criterion measure or reference standard - there should be a high relationship
- Reliability
are the results consistent and reproducible? A highly reliable test yields the same or approximately the same scores when administered twice to the same individuals, provided conditions and subjects are essentially the same.
Error – the deviation of a measurement, observation, or calculation from the truth.
Random errors influence the results in a random (statistically unpredictable) manner. They cause the results to spread in both directions (positive and negative) about the true value.
If a result is not repeatable –> random errors –> repeat the measurement several times and take the mean
There will always be a certain amount of random error - due to a combination technical error and biological variation in performance.
Test administration should be rigidly controlled - standard instructions to the subjects, standard practice or warm-up procedures, standard order of test items and recovery times between items, standard environmental temperature and humidity, and standard equipment and equipment calibration procedures.
Skills that require a high proficiency of coordination and reaction should be tested before any tests that may cause fatigue and decrease performance.
- Objectivity
the level to which multiple testers agree on the scoring of tests. To optimize objectivity, it is best to use trained testers, a predetermined scoring system, and if possible, one designated tester.
- Accuracy
A measure of how close a result is to the “true” value. The accuracy with which things are measured, or with which differences are perceived, depends first upon the precision of the measuring instruments.
All measuring instruments have their limitations.
Systematic errors - errors that systematically shift the measurements in one direction away from the true value. They can be caused by instrumentation errors or by the use of incorrect measurement techniques.
Gain versus offset errors
Systematic errors caused by a measuring instrument can be estimated by comparison with a more accurate and reliable instrument - calibration of instruments.
- Norms
allow a relative rating or classification of the subject’s performance. They describe a person’s position in a population.
If the only information available about a subject’s test performance is the raw score, interpreting it meaningfully can be difficult.
A norm describes a subject in relation to a large number of people who have taken the test.
Norm charts should be evaluated to determine their quality. The following questions should be asked:
a) Were the sampling procedures for the construction of the norms based on a wide distribution of the population?
b) Was a large sample size used to construct the norms?
c) Are the norms being used for the specific groups for which they were prepared?
Percentile – a point or a position on a theoretical scale of 100 divisions such that a certain fraction of the population of raw scores lies at or below that point.
Median – the 50th percentile, the score that divides a distribution so that 50% of the scores are above this point and 50% fall below.
- Economy
consider two factors:
a) money costs and
b) time required of subjects and testers
Other things being reasonably equal (validity, reliability, accuracy), choose a test that meets your objectives and requires little in money and time.
Laboratory tests – typically require specialized equipment and specialized training for the test administrator. They are usually administered to only one person at a time.
Field tests – require no expensive equipment and little, if any, specialized training. These tests can be administered to a group of individuals at the same time, and they are usually less precise than laboratory tests.
skeletal muscle- structure and function
Muscle cells (fibers)
are the only cells in the body that have the property of contractility, which allows them to shorten and develop tension.
- 3 types
Skeletal muscle
attaches to and moves the skeleton. The contractile molecules are very organized giving skeletal muscle a striated pattern, hence the name, “striated muscle”. It is under voluntary control.
Skeletal muscle comprises about 36 % of the total body weight in women and 42 % in men. 75 percent of skeletal muscle is water, 20 % is protein, and the remainder consists of inorganic salts, pigments, fats, and carbohydrates.
Smooth muscle
found in the walls of hollow organs and blood vessels. The contractile molecules are not aligned in a set pattern like skeletal muscle, hence the name smooth muscle. This muscle is under involuntary control.
Cardiac muscle
the contractile tissue of the heart wall. This muscle has characteristics of both smooth muscle and skeletal muscle. The contractile molecules are organized very much like skeletal muscle. Like smooth muscle, it is also under involuntary control.
Criteria Used To Name Muscles
- Shape - deltoid (triangular), trapezius, rhomboid, latissimus (wide)
- Action - various muscle names include the terms flexor, extensor, adductor, or pronator.
- Location - tibialis anterior, intercostals, pectoralis major
- Divisions - triceps brachii, quadriceps femoris
- Size relations - gluteus maximus, gluteus medius, gluteus minimus. Several names include the terms “brevis” (short), and “longus” (long).
- Direction of fibers - transversus (across), rectus (straight)
Skeletal Muscle Shapes
A fascicle is a bundle of muscle fibres that are encased by perimysium.
Fasciculi may run parallel to long axis of muscle (great range of motion, little strength) or insert diagonally into a tendon running the length of the muscle (small range of motion, greater strength).
- Unipennate - all fasciculi insert on one side of a tendon - semimembranosus
- Bipennate - fasciculi insert on both sides of tendon - rectus femoris
- Multipennate - convergence of several tendons - deltoid
- Longitudinal (strap) - fasciculi run parallel to the long axis of the muscle - sartorius, rectus abdominus
- Radiate - fibers fan out from a single attachment - pectoralis major
Muscle Actions
Most movements require the cooperative action of several muscles functioning as a group.
- Prime mover - a muscle whose contraction is primarily responsible for a particular movement.
Most movements are the result of the contraction of more than one muscle, and frequently a single muscle contributes to the production of two or more movements. - Antagonist - muscles that oppose one another upon contraction - biceps and triceps. Antagonists are located on opposite sides of a joint.
- Fixators/stabilizers - muscles that immobilize a bone or joint near the origin of the prime mover so that the prime mover can act more efficiently.
Note that a few muscles in our body have no real function. The plantaris muscle which flexes all our toes is exceptionally functional for primates but no longer even reaches our toes and is actually absent in about 10 % of the population.
Gross Anatomy
Tendons are extensions of connective tissue membranes beyond the end of the muscle.
Origin - less movable end of a muscle, usually proximal.
Insertion - more movable end of a muscle, usually distal.
Belly - widest portion of a muscle, between its origin and insertion.
Not all muscles insert on bone. Most of the muscles controlling facial expression originate from bone and insert in the skin.
Connective Tissue
The three layers of connective tissue,
endomysium,
perimysium,
and epimysium, surrounding muscle fibers, bundles of muscle fibers (fasciculi), and whole muscle, respectively, serve in part to maintain intramuscular pressure thereby augmenting force production.
Tendons are extensions of connective tissue membranes beyond the end of the muscle. Tendons transmit the force of contractile tissue to bone. Tendons are much stronger than muscle and as such can receive force from a large number of muscle fibers (with a much larger total cross-sectional area than the tendon) and insert on to a small area of a bone such as a tuberosity.
Blood Supply
Because muscle tissue can increase its metabolic rate 100x, it has an abundant blood supply. On average, there are about 3-4 capillaries surrounding each muscle fiber of a sedentary person. Training can induce capillary angiogenesis, resulting in up to 7 capillaries per muscle fiber.
Muscles require a good supply of blood for continued force generation. The problem is when muscle force increases, so does intramuscular pressure. The increase in intramuscular pressure can exceed that of blood pressure thus restricting blood flow within the muscle. In general, this can start to occur at about 15-20 % of maximum muscle force and completely halt blood flow at about 50 % of maximum force.
Microanatomy of Skeletal Muscle
A muscle cell is a muscle fiber. Within each muscle cell/fiber are many myofibrils. Each myofibril consist of a large array of contractile proteins arranged repeatedly in series. This gives skeletal muscle its striated pattern of light and dark areas or bands. Each repeated array of contractile proteins is called a sarcomere.
The two major contractile proteins of the sarcomere are actin (thin filament) and myosin (thick filament). Myosin has cross-bridges extending from its thick central core. The most prominent theory of muscle contraction is the sliding filament theory. This theory suggests that, when the muscle is activated, the protruding cross-bridges on myosin attach to actin and, with the aid of ATP, the cross-bridge microstructure can “rotate” thus causing the thin actin filament to “slide” over myosin. This causes the sarcomere to shorten.
maximal shortening is about 20%
The sequence of events is as follows:
sliding filament theory
-A motor neuron in the spinal cord is stimulated
-A nerve action potential travels to the muscle
-Muscle cells are stimulated
-A muscle action potential moves across the muscle membrane and down into the t-tubules
-Sarcoplasmic reticulum (SR) is stimulated to release calcium
-Calcium binds to troponin
Actin binding sites are exposed
-Myosin heads attached to the actin binding sites forming a cross bridge (XB)
-Myosin heads ‘flip’ and myosin dissociates from actin
-Myosin is recharged with ATP
-Binding and sliding continues
-With no more nerve stimulation, calcium is pumped back into the SR
-Actin binding sites get covered again by tropomyosin
-No calcium equals no tension
Function of Skeletal Muscle
Activation of a muscle fiber can, in the extreme, produce either maximum force or maximum velocity. In between these extremes, a muscle fiber creates a combination of force and movement.
Force related to…. cross bridges
Speed related to ….
slow speed, more cross-bridges
fast speed, skip cross-bridges
The Motor Unit
A motor unit is the functional unit of a muscle. It consists of a motor neuron (alpha) and all the muscle fibers that motor neuron innervates. The cell body of a motor neuron is located in the spinal cord. The axon of that motor neuron extends from the spinal cord to the target muscle which may be a few millimeters away or a few feet away. When the axon is close to the muscle it separates many times (bifurcates) to innervate all the muscle fibers of that particular motor unit. For an average motor unit the motor neuron will innervate about 200 muscles fibers. The range is from 2-3 muscle fibers per motor unit for muscles capable of very fine movements to 2000 fibers per motor unit for large muscles that perform only gross movements.
If the cell body of the motor neuron receives a strong enough stimulus, an action potential is generated. This action potential travels along the axon and all its bifurcations to stimulate each and every muscle fiber in that particular motor unit. This is known as the all-or-none law.
Types of Motor Units
Motor units can be classified in two ways on the basis of speed of contraction (slow twitch & fast twitch), and in three ways on the basis of metabolic characteristics:
Slow twitch oxidative (SO) – also called “type I”
Fast twitch oxidative-glycolytic (FOG) – also called “type IIa”
Fast twitch glycolytic (FG) – also called “type IIb”
motor units in humans
Men, women, and children generally have 45 to 55 % slow twitch fibers in their arm and leg muscles. However, there can be considerable variation in fiber type distribution from muscle to muscle and from person to person.
All of the muscle fibers in a given motor unit will have identical contractile and metabolic properties.
Endurance athletes have higher than average proportions of slow twitch muscle fibers in the muscles used in their sport, while power athletes have high proportions of fast twitch muscle fibers.
Slow twitch fibers and fast twitch fibers can’t be inter-converted by physical training. However, FOG and FG fibers can be inter-converted by physical training.
Current research indicates that genetic factors largely determine a person’s predominant muscle fiber distribution.
Force Control of a Motor Unit.
- Multiple Motor Unit Summation. A large muscle may contain up to 2,000 motor units. A skeletal muscle can increase force production by activating more motor units. A low force requires the activation of a small number of motor units while a higher force requirement progressively enlists more motor units.
- Frequency or Wave Summation. If a single action potential travels down a motor neuron axon, the motor unit response is a twitch. If many action potentials travel down the axon at a rate faster than the twitch response time of the motor unit, then the mechanical force response will summate. At high motor neuron firing rates (i.e., many action potentials in a short period of time) this effect can generate on average about 5x the force of a single twitch.
When all motor units are activated, and they are all activated at a high firing rate, then the muscle is maximally activated.
Size principle of motor unit recruitment
there is a recruitment order of motor units as exercise intensity increases. As the muscle force requirement increases, motor units with progressively larger axons are recruited. Slow twitch motor units with the lowest activation threshold are selectively recruited during light to moderate effort. More rapid, powerful movements progressively activate FOG motor units and then FG motor units.
- Muscle Length-Tension Relation
An isolated muscle can exert its maximal force or tension while in a resting stretched position. As the muscle shortens, less tension can be exerted.
When a muscle is stretched or shortened, the length of each individual sarcomere also increases or decreases, respectively. Within the range of sarcomere lengths there is an optimal length at which provides for the greatest possible number of cross-bridge formations. Longer or shorter than this optimal length, the number of cross-bridge formations is reduced and thus active force production is reduced.
Muscles must be stretched from their resting length for most effective action.
Example - flexing the knee, hip, and ankle joints before jumping.
In a movement such as vertical jumping, preparatory counter movement shifts the force-velocity curve to the right, thus causing the leg extensor muscles to exert much higher forces at any angular velocity of the knee in the concentric phase.
The enhancement of performance in this “stretch-shortening” cycle can be attributed to restitution of elastic energy and stretch reflex potentiation of muscle.
- Muscle Force-Velocity and Power-Velocity Relations
When maximally activated, the faster a muscle shortens the less force it produces. When the velocity of shortening is zero, this is defined as an isometric contraction (i.e., no change in muscle length). If the velocity is negative, then the muscle is lengthening when it is activated. This is an eccentric contraction. An example of an eccentric contraction is when you slowly lower the barbell after doing a biceps curl. You are still using your biceps, but your muscle is lengthening. In this condition it is possible for the biceps to generate more force than at the opposite speed while shortening. This eccentric type contraction is what is targeted when performing the training technique of plyometrics. Remember, the curve defining the force-velocity relation is based on maximal activation. The vast majority of muscle activations we use are of the submaximal variety and are located well underneath the maximum curve.
Power is not an independent factor influencing force, rather power is the product of force times velocity. In many athletic endeavours, it is power that is the most important variable determining success. The graph of the relation of power with velocity shaped like an upside down ‘U’, hence the name the “inverted U hypothesis” is sometimes used when describing this relation (see Fig. 11-5 in Lab Manual). This inverted U type relation occurs because on the left of the graph, when velocity is zero, power must be zero. As with the force-velocity curve, most of our muscle activations are well below the maximum curve
power is force times velocity
The peak torque generated by a muscle decreases with increasing velocities of movement. Maximum power output occurs at approximately one half of maximum velocity and one third of maximum concentric force.
Angle of Muscle Pull
In the intact human body, the muscles act on the bones about the joints to form a lever system.
When a muscle is pulling at an angle of 90 degrees to a bone, all of the muscle contractile force is acting to rotate the bone around the joint.
At angles greater than 90 degrees, the magnitude of the rotational component of the muscle pull force decreases while the magnitude of the stabilizing component of the force increases.
In summary, three factors that affect the expression of strength by a muscle are:
- Speed of shortening.
- The initial length of the muscle fibers.
- The angle of pull of the muscle on the bony skeleton.
Muscular strength
the greatest amount of force that muscles can produce in a single maximal effort.
Power
work per unit time = force X velocity.
Power involves strength and speed.
Types of Muscular Contraction
- dynamic (isotonic) contraction
-concentric contraction
-eccentric contraction - isometric contraction
- isokinetic contraction
- eccentric loading
- plyometric loading
- Dynamic (isotonic) contraction
the bony levers move through a range of motion when the appropriate muscles perform work.
Concentric contraction - the muscle shortens with varying tension as it lifts a constant load.
Eccentric contraction - the external resistance exceeds the muscle force and the muscle lengthens while developing force. Eccentric contractions are usually used in resisting gravity.
- Isometric contraction
static contraction. Tension is developed but there is no change in the angle of the joint or the length of the muscle.
- Isokinetic contraction
the muscle is shortened at a constant velocity determined by instrumentation which allows a person to exert maximal force throughout the full range of motion.
- Eccentric Loading.
Any exercise that can be performed concentrically can also be performed eccentrically. For example, in the bench press exercise pushing the bar from the chest to the finish or arms extended position involves a concentric contraction of the pectorals major, anterior deltoid, and triceps muscles. Lowering the bar back to the chest involves an eccentric contraction of the same muscle groups. In eccentric loading for the bench press exercise one would start with a heavy weight in the arms extended position and then slowly lower the bar to the chest. A partner would then help to get the bar up again. Several studies have shown that this is an effective means of gaining strength, although it is not superior to other isotonic techniques. One drawback of eccentric training is that it creates more muscle soreness (delayed onset muscular soreness; DOMS) than other methods, especially for anyone not used to the movement. Eccentric loading is not widely practiced by strength athletes except as an adjunct to other training methods.
- Plyometric Loading (aka depth jumping or stretch-shortening cycle).
In plyometric loading the muscles are loaded suddenly and forced to strength before they can contract and elicit movement. Plyometric drills include bounds, hops, jumps, leaps, swings, twists, and other movements. Plyometrics is one of the best ways to develop explosive power for sports. It is a very vigorous form of exercise. In order to avoid injury to muscles (DOMS), tendons and joints, it is very important to establish a good base level of strength before using plyometric training methods.
