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accommodation     According to Piaget, a facet of adaptation in which the individual attempts to adjust existing thought structures to account for, or accommodate, new experiences.

accommodation     Related to vision, the process of the human eye changing shape that maintains a clear retinal image in the presence of varying light conditions.

activities of daily living (ADLs)     Regular self-care activities that are fundamental for functioning (e.g., eating, getting out of a chair or bed, dressing, bathing).

adaptation     According to Piaget, the process by which cognitive development occurs involving adjusting to the demands of the environment and the intellectualization of that adjustment through two complementary acts, assimilation and accommodation.

adiposity rebound     The upward trend in BMI that occurs after the low point on the BMI percentile curve.

adolescent awkwardness     A temporary disruption in motor performance during the period characterized by peak height velocity, the period during the growth spurt when height is increasing at its maximum rate.

age of menarche     The age at which the menstruation begins, useful for estimating maturation in girls occurring close to the completion of female peak growth height.

ageism     Negative stereotypes concerning older adults that can lead to discrimination and the exclusion of older adults from social interaction.

age-related macular degeneration (AMD)     A loss in visual acuity that occurs in dry form resulting from the breakdown of the light-sensitive cells in the macula, as well as in wet form in which new blood vessels behind the retina leak and cause deterioration of the macula.

aggregate stage     A stage in the development of the drawing product in which the child not only combines figures and shapes but does so in combinations of three or more.

alcohol-related birth defects (ARBD)     Birth defects resulting from the consumption of alcohol during pregnancy.

alcohol-related neurodevelopmental disorders (ARND)     Neurodevelopmental disorders resulting from the consumption of alcohol during pregnancy.

alpha-fetoprotein test     A blood test performed at approximately 15 to 20 weeks into a pregnancy that measures the amount of alpha-fetoprotein (AFP) in the blood low levels of which may signal a chromosomal disorder such as Down syndrome.

amenorrhea     Absence of a menstrual cycle for more than 3 months.

amniocentesis    A procedure that employs a thin needle to remove amniotic fluid drawn from around the fetus to determine the presence of some disorders.

Amsler grid    A test used to screen for wet age-related macular degeneration.

anabolic steroids     Androgens, such as testosterone, that are taken to aid in the development of muscle mass.

androgens     Sex hormones.

anti-D IgG immunoglobulin     In cases of Rh incompatibility between parents, an injection mothers receive after their first delivery that protects subsequent children’s fetal red blood cells from being destroyed by the mother’s antibodies.

appositional bone formation     A postnatal increase in the diameter of a long bone as a result of bone deposition rate being greater than the rate of reabsorption.

appropriate for gestational age (AGA)     A birth weight classification indicating the child’s size is within normal range for its gestational age.

assimilation     According to Piaget , a facet of adaptation in which humans attempts to interpret new experiences based on their present interpretation of the world.

associative play     A level of play behavior in which two or more children exhibit an awareness of each other and begin to exchange toys with no group goal.

asymmetric tonic neck reflex     A reflex elicited when a baby is prone or supine and the head is turned to one side or the other, causing the limbs on the face side to extend while the limbs on the opposite side flex.

auditory perception     The process whereby auditory stimuli are received, selected, organized, and interpreted.

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Babinski reflex     A reflex in which, to elicit a response, the bottom or lateral portion of the foot is stroked, resulting in a downward turning of the great toe and sometimes all the toes of the stimulated foot.

balance     A state of equilibrium in which the desired body posture is maintained. Sometimes referred to as postural control.

balance     The ability to control the body’s position in space for the purpose of maintaining a static position or engaging in a dynamic action.

biacromial/bicristal ratio     A measure of proportional growth relating biacromial breadth, a measure of shoulder width and the distance between the right and left acromial processes, with bicristal breadth, a measure of hip width and the distance between the right and left iliocristales (hipbones).

binocular vision     Coordinated eye movement in which both eyes move in unison so that each focuses the desired image on its macula.

blindness     A loss in vision ranging from total loss of vision to an 80 percent loss of vision.

Bod Pod     A method for measuring body composition based on the displacement of air.

body building     A competitive sport in which participants use resistance training to develop muscle size, body symmetry, and muscle definition.

body composition     The percentages of fat, bone, water, and muscle tissue in an individual.

body mass index (BMI)     A valuable measurement of body weight and height associated with the prediction of future health risks that is found by the measurement of body weight in kilograms divided by the square of the height in meters.

body scaling     Selecting equipment that is sized appropriately for the performer’s body dimensions.

bone remodeling     Changes in bone shape, size, and density that are a response to forces acting on bone.

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carbon monoxide     A pharmacological byproduct of tobacco smoke known to interfere with hemoglobin’s oxygen-carrying and oxygen-releasing capabilities and, therefore, to increase the risk of fetal hypoxia.

cardiac output     The amount of blood that can be pumped out of the heart in 1 minute.

cardiorespiratory fitness     The efficiency of the heart, lungs, and vascular system in delivering oxygen to the working muscle tissues so that prolonged physical work can be maintained.

cataracts    A clouding of the eye’s lens that results in the loss of visual acuity.

catching     The action of bringing an airborne object under control by using the hands and arms.

catch-up     The human power “to stabilize and return” to a predetermined behavior or growth pattern “after being pushed off trajectory” (Tanner, 1978, p. 154).

cephalocaudal     The development or growth of the human being from the top of the body, the head, downward toward the “tail”, or the feet. Literally meaning “from the head to the tail.”

choice reaction time     Reaction time when any one of several stimuli may appear with requiring a response that may differ based on which stimulus appears.

chorionic villus sampling (CVS)     A prenatal tool that can be administered between 10 and 12 weeks of gestation so that any atypical characters can be detected earlier (Elias & Simpson, 2000).

chronological age     The length of time from birth that is generally used to denote a person’s level of maturity but fails to address individual variation in rate of maturation.

ciliary muscle     A muscle that, when contracted, changes the shape of the human eye’s lens.

clinical method     Piaget’s system of collecting data in question-and-answer sessions to understand more fully a child’s process of thinking about the world. (Newman & Newman, 2015).

coincidence-anticipation     The process behind the coordinated interception of a moving object.

combine stage     A stage in the development of drawing that begins with the construction of basic geometric shapes, continues with more precise figures, and culminates in drawing shapes in combination with others to form simple familiar objects.

commotio cordis     Nonpenetrating chest trauma that can potentially cause sudden death from ventricular fibrillation.

compensation period     A period of motor development involving a nullifying of or adaptation to the effects of some type of negative influence.

competence motivation theory     A theory that posits that individuals experience a positive effect with high levels of perceived successful competence or a negative effect with low levels of perceived competence in various achievement areas.

concrete operational stage     Piaget’s third major stage of cognitive development, spanning from approximately 7 to 11 years of age, that is characterized by children gaining an enhanced ability to decenter attention from one variable in a problem-solving situation to other important aspects.

concussion     Mild or traumatic brain injury.

cones     A photoreceptor dominant in the retina’s macula that makes color vision and acuity possible.

congenital rubella syndrome (CRS)     A birth defect as a result of the mother contracting rubella, which can cause significant fetal defects.

conservation     An ability that allows a person to understand that certain characteristics of an object may remain the same when the object’s appearance is rearranged (Shaffer & Kipp, 2014).

constraints     Factors that limit, contain, or help shape the development of movement.

contact/collision sport     Sport in which individuals repeatedly run into one another.

content validity     A form of validity where the content of the attribute being measured is adequately assessed by the measurement process.

context-specific period     A period in the Mountain of Motor Development in which proficiency in certain skills is applied to different specialized areas.

contextual perspective     A perspective recognizing that factors other than age have effects on intellectual change across time, i.e., situational factors.

contralateral     A creeping pattern in which the movements of the limbs oppose each other—as the right arm and left leg go forward, the left arm and right leg go backwards.

contralateral     Movement in which limbs on opposite sides of the body work together.

correlation coefficient     A quantitative measure indicating the magnitude and direction of the relationship between two sets of scores used to determine reliability and objectivity.

crawling reflex     A reflex in which, to elicit a response, the baby is placed prone on the floor or table, and the soles of the feet are stroked alternately, causing the legs and arms to move in an action similar to crawling.

crawling     An early stage in locomotion in which the infant tries to travel by thrusting the arms forward and flexing while the legs are flexed and re-extended for propulsion.

creeping     An early stage of locomotion in which the infant elevates the body from the supporting surface with the legs flexed into a position beneath the body.

criterion-referenced (CR) assessment instruments     Instruments that evaluate the “quality” of a person’s performance by using a predictable sequence of milestones of human development, allowing the observer to determine where a person’s performance lies on this continuum.

critical periods     Times in which specific conditions are required for optimal, or even typical, development to ensue (Bailey & Gariepy, 2008).

crossed-lateral dominance     A condition in which an individual is either right-eyed and left-handed or left-eyed and right-handed.

cutaneous system     The system that provides tactile sensitivity receiving information from the skin consisting of at least four senses: pressure, coldness, warmth, and pain.

cystic fibrosis (CF)     An inherited disease that causes thick, sticky mucus to be secreted within the lungs, causing reoccurring bouts of pulmonary infection clogging the pancreas and interfering with typical digestion.

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declarative knowledge     Factual information or an awareness of something like an event, an object, or even an idea.

deprivation dwarfism     A condition occurring as a result of infants being significantly under stimulated emotionally or socially that can cause listlessness, apathy, depression and even delayed growth and physical ailments.

deprivation     A lack of early stimulation (e.g., emotional attachment, social interaction, nourishment, intellectual stimulation).

development     Changes in the human being across time that are a function of genetics as well as environmental adaptations throughout life.

developmental age     Age indicated by landmark parameters tied to physiological events that occur in all people.

developmental perspective     A method of studying human movement in which an awareness of developmental change is emphasized with a primary interest in understanding what movement was and will be, and how and why it was and will be.

developmentally appropriate     Using knowledge and awareness of developmental change to tailor programs to meet the needs of children, rather than expecting children to adjust to the demands of a specific program.

diabetes mellitus     An endocrine disease that can result in complications during pregnancy for infants born to mothers with the disease. These infants can be large for their gestational age.

diabetic retinopathy     A complication of diabetes that can cause the vessels of the retina to hemorrhage, which in turn discolors the eye’s interior gel and can cause the retina to detach the retina.

diaphysis     The shaft or center of a long bone.

differentiation     The progression from gross, immature movement to precise, well-controlled, intentional movement as segments of the body develop a unique duty or specialization in a movement.

distance curve     A graphic used to plot an individual’s accumulated growth over time.

disuse atrophy     The wasting away of muscle mass that is the direct result of physical inactivity, occurring when an individual simply does not use the muscles sufficiently.

double support phase     A phase in walking in which both feet are in contact with the supporting surface.

Down syndrome (DS)     A birth defect in which the child has three number 21 chromosomes instead of the usual two that causes mild to severe cognitive delay.

dribbling     A movement in which a person bounces a ball by using the hand to push the ball repeatedly downward.

drusen     Small yellow deposits in the retina that are an early sign of age-related macular degeneration.

dual-energy X-ray absorptiometry (DEXA)     A noninvasive radiologic technique that differentiates body weight into three components: lean soft tissue, fat soft tissue, and bone.

dynamic balance     The ability to maintain desired body position when the body is in motion.

dynamic balance     Balance that occurs when the supporting surface and the center of body mass move.

dynamic force     A muscular force exerted against a movable object with a change in the length of the exercised muscle.

dynamic systems theory     A theory positing that developmental systems are complex, coordinated and self-organizing with reduced emphasis placed on more traditional elements (such as the performer’s age or genetics) and increased value placed on environmental interaction.

dynamic tripod     The mature grasp of an implement in which the thumb, middle finger, and index finger function as a tripod for the writing implement, enabling the child to perform small, highly coordinated movements of the implement.

dynamic visual acuity     The ability to see detail in moving objects.

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earthbound     An individual who lacks the necessary strength needed to launch the body from a supporting surface.

ectoderm     A zygote’s outer layer of cells that subdivides to become the basis for the development of the nervous system, sensory receptors, and skin features.

ectomorphic     A component used by Sheldon in his method of rating physique to indicate a tall and thin body.

endochondral bone formation     A process in the postnatal development of the bone in which the bones lengthen at the epiphyseal cartilage discs or secondary ossification centers.

endoderm     A zygote’s inner layer of cells that provides the groundwork for the development of both the digestive system and the respiratory system.

endomorphic     A component used by Sheldon in his method of rating physique to indicate a round and soft body.

energy availability     Dietary energy intake minus exercise energy expended; it indicates the fuel available for other body functions, including growth, cellular maintenance, thermoregulation, and reproduction.

epiphyseal plate     A cartilage plate found at the end of long bones that ossifies as a sign of maturity.

erythroblastosis fetalis     A condition caused as a result of Rh-positive offspring being exposed to an Rh-negative mother’s antibodies, causing anemia, an increased number of immature red blood cells in circulation, generalized edema, and jaundice.

exercise–aging cycle     A proposed cycle during adulthood depicting the gradual disengagement from physical activities, causing declines in motor ability and physical declines—including percent fat increases, muscular atrophy, and energy level reductions—resulting in a cyclical decrease in physical activity.

exergaming     A format of interactive video gaming that requires physical participation.

explicit memory     Deliberate and effortful remembrance that is tested by traditional tests of recall or recognition.

exploratory play     A level of play behavior in which children often examine and explore the detailed characteristics of objects, such as toys, in their environment.

exploratory procedures     Hand movements related to haptic procedures in which a child gathers information about an object via touch.

extrinsic causes     Factors surrounding a fall that are linked to the environmental situation (e.g., darkness, environmental obstacles, medication, alcohol or drug use).

eye dominance     The tendency of one eye to lead the other in tasks involving visual tracking and visual fixation.

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female athlete triad     Three related disorders most prevalent in female athletes composed of (1) an eating disorder that leads to (2) amenorrhea (absence of a menstrual cycle for more than 3 months), which in turn leads to osteopenia (low BMD), resulting in (3) osteoporosis.

fetal alcohol spectrum disorders (FASDs)     An umbrella term that includes the range of possible effects associated with alcohol consumption during pregnancy.

fetal alcohol syndrome (FAS)     A disorder caused by alcohol consumption during pregnancy that results in altered facial features, mental retardation, attention deficit disorder with hyperactivity, and retarded physical growth in stature, weight, and head circumference.

fine motor     Movements predominantly produced by the smaller muscles or muscle groups of the body.

fine movement     Movement governed primarily by the small muscles or muscle groups.

flexibility     The range of movement within a person’s joints.

flight phase     A phase in running in which the body has been thrust into the air by the vigorous extension of the support leg.

formal operational stage     Piaget’s final (fourth) stage of development beginning at around 11 or 12 years in which the individual is able to consider ideas not based on reality and no longer confined to ideas about observable objects or experience-based thoughts.

fragile X syndrome (FXS)     A leading cause of autism that comes as a result of a mutation in the FMR1 gene.

frailty     A complex health state of increased vulnerability to stressors due to impairments in multiple systems.

functional fitness     A measure of an individual’s physical capability in upper- and lower-body functioning.

fundamental patterns period     A developmental period beginning in infancy in which a young child establishes an array of movements that enable a quantity and quality of movement skill in later life.

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gait cycle     The distance covered by two heel strikes of the same foot, consisting of the swing phase and the support phase.

gait     Walking patterns.

gallop     A motor pattern consisting of a forward step followed by a leap onto the trailing foot.

gender role identity     The degree to which an individual identifies himself or herself with a particular gender.

genitalia maturity     The stages of pubertal development based on the development of male and female genitalia used as an ancillary method for rating maturation.

giardia     A parasite found in contaminated soil, food, or water that, when ingested, can develop into cysts in the intestinal tract and can cause low-grade fever, chills, distended abdomen, and severe diarrhea.

glaucoma     An eye disease resulting from fluid being plugged in the eye’s anterior chamber, causing loss in peripheral vision that can rapidly progress to affect central visual acuity and damage the optic nerve.

global self-worth     The overall value that a person places on himself or herself as a person.

golgi tendon organs     Small stretch receptors located near the junction of the muscle and the muscle’s tendon.

gross movement     Movement primarily controlled by the large muscles or muscle groups.

growth     The quantitative and structural (physical) increases that occur with age.

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haptic perception     The active manipulation of the hands in holding and exploring an object to acquire information (e.g., temperature, size, hardness, weight, shape, texture) about the object.

head- and body-righting reflexes     In the head-righting reflex, when the body is turned while the baby is supine or prone, the head follows by returning to a front-facing position relative to the shoulders. In the body-righting reflex, when the head is turned to one side or the other, the body follows and turns to align the shoulders in a front facing position with the head.

head circumference     A measurement used to indicate the relationship of head length to overall body length in body proportion measures.

heart rate (HR)     The number of times the heart beats each minute.

heterozygous     A genetic trait carried on one of two chromosomes.

homolateral     A creeping pattern characterized by the limbs on the same side simultaneously moving forward or backward in opposition to the arms and legs on the other side of the body.

homolateral     Movement in which limbs on the same side of the body work together.

homozygous     A genetic trait carried on both of two chromosomes.

hopping     A form of jumping in which the propelling force is generated in one leg and the landing is accomplished on the same leg.

horizontal jump     A jump in which the body is propelled both upward and forward.

human immunodeficiency virus (HIV)     A virus that affects the immune system and that can be passed on to a child during a woman’s pregnancy or through breast milk.

human motor development     Changes that occur in the ability to move and movement in general as people proceed through their lifespan, as well as a field of study examining changes in human movement across the lifespan and the processes that affect those changes.

hydrostatic weighing (HW)     The “gold standard” for determining a person’s body composition based on the displacement of water.

hyperglycemia     High blood sugar.

hyperopic     A condition in infancy in which light entering the eye focuses behind the retina resulting from the eye being shorter at birth than at maturity.

hypertrophy     An increase in the size of muscle.

hypoglycemia     Low blood sugar.

hyponatremia     A condition occurring when an individual ingests so much water that the body’s electrolytes are reduced and the kidneys cannot filter the excess fluid and that can cause reduced sodium serum levels, loss of consciousness, reduced core temperature, and seizures

hypothermia     A condition that occurs when the body temperature falls significantly below normal with symptoms including numbness in the extremities, fingers or lips turning blue, and, in more extreme cases, confusion or disorientation.

hypothetical-deductive reasoning     A problem-solving style in which the individual generates and systematically considers possible solutions to a problem.

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implicit memory     Memory that is unintentional, automatic, or without awareness.

information-processing theory     A theory that suggests the human mind functions much like a computer.

instrumental activities of daily living (IADLs)     Regular self-care activities that are less fundamental for function than ADLs but necessary to maintain independent living (e.g., cooking, shopping, doing laundry).

integration     An ability to employ various muscle systems simultaneously; a synonym for coordination.

interpersonal play     Play with one or more others.

interpropositional thought     The enhanced level of cognitive ability that allows children to relate one or more parts of a proposition or a situation to another part to arrive at a solution to a problem or an understanding of a proposition or a problem.

interrater reliability     Also known as objectivity, the degree of accuracy to which a test is scored.

intrinsic causes     Causes of a fall directly related to the inherent physiology or cognitive ability of an individual (e.g., disease, reduced flexibility or strength, fatigue, visual impairment).

isometric force     Force exerted against an immovable object with no or very little change in the length of the exercised muscle.

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jumping     A fundamental movement in which the body is projected into the air by force generated in one or both legs and the body lands on one or both feet.

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kicking     A form of striking in which the foot is used to give impetus to a ball.

knee height     A recumbent measurement of the knee’s height of the distance from under the heel to over the anterior portion of the thigh used for older adults or individuals with disabilities to determine stature.

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labyrinthine reflex     A protective reflex crucial for survival in which the baby “rights” or elevates the head in response to being placed in a prone position, allowing for the baby to move the head to a position more conducive to breathing and allowing the baby to survive. A second version of the labyrinthine reflex that results in a tilting of the head in the opposite direction of a tilting of the body; for example, when the body is tipped to the right, the head tips back to the left.

large for gestational age (LGA)     A birth weight classification indicating the child’s size is greater than the 90th percentile for its gestational age.

last-in-first-out hypothesis     A hypothesis suggesting that the neural and muscular capability to perform simple movement acts developed early in life are relatively resistant to decline with aging and that the more coordinated, goal-oriented, or complicated movements developed later in life begin to decline earlier.

law of specificity     States that improvements as a result of training are specific to the component being trained.

leap     A form of jumping in which the propelling force is generated in one leg and the landing is accomplished on the nonpropelling leg.

level of fixity     The degree to which a skill is established when it is discontinued.

lifespan reflexes     Reflexes, like a knee jerk, that endure throughout the lifespan in typically developing and healthy individuals.

locomotion     A category of voluntary movement of infancy that includes movements such as creeping, crawling, walking, and running, moving from one point in space to another, and their variations.

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macrosomia     Birth weight above the 90th percentile for gestational age or greater than 8.8 lb. (4,000 g), making a vaginal delivery difficult. A common occurrence in mothers with diabetes mellitus.

macula     An area in the center of the retina that predominantly house the cones of the eye.

manipulation     A category of voluntary movement of infancy that involves the voluntary use of the hands, such as the entire progression of movements leading to the attainment of a mature reaching, grasping, and releasing ability.

manipulation     A general term referring to hand use, mostly reaching and grasping.

maturation     Qualitative and functional changes that occur across time.

maturational period     A period in motor development history dominated by the maturational philosophy, a theory that held that biological processes were the main influence in shaping human development.

maximal oxygen consumption (VO2max)     The largest amount of oxygen that a human can consume at the tissue level.

mechanoreceptors     Sensory receptor cells that respond to changes in joint angles, changes in the lengths and tension relationships of muscles, and movements of the head and that are activated by mechanical deformation.

meiotic nondisjunction     A lack of chromosomal separation resulting in one sperm or egg cell containing two members of a particular chromosome, causing a new individual to possess 47 chromosomes.

mesoderm     A zygote’s outside layer of cells of which the circulatory system, muscles, bones, excretory system, and reproductive system are all outgrowths.

mesomorphic     A component used by Sheldon in his method of rating physique to indicate a muscular body.

midgrowth spurt     A sudden acceleration of growth in height experienced by some children between 6.5 and 8.5 years of age.

Mobility Consequences Model     A model demonstrating how a repeated series of events, beginning with a decline in physical or mental abilities, leads to a decline in mobility that reduces the scope of an individual’s activities and leads to a further decline in physical or mental abilities.

Moro reflex     A reflex that is a form of a startle reflex in which the stimuli cause the baby’s arms, fingers, and legs to extend abruptly.

motion hypothesis     The idea that individuals must attend to objects that move in order to develop a normal repertoire of visual-spatial skills, such as depth perception.

Mountain of Motor Development     Clark and Metcalfe’s representation (metaphor) of human motor development that combines a description of the expected changes in motor development across the lifespan with explanations for how these changes may ensue. Change in movement behavior across the lifespan is represented as an ascent (progression) or descent (regression) up a mountain.

movement time     The period of time from the beginning of a movement until its completion.

muscle spindles     Cigar-shaped structures that are attached in parallel with the muscles’ largest fibers and that gauge the amount of tension within the muscle and stimulate the skeletomotor neurons, contracting the muscle.

muscular strength     The ability to exert muscular force.

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National Standards for Youth Sports     A set of standards intended to provide a quality framework for the design and execution of youth sport programs.

neonatal abstinence syndrome (NAS)     Withdrawal symptoms in babies during the neonatal period that include tremulousness, hyperactivity, and irritability.

nicotine     A byproduct of tobacco smoke that can contribute to fetal hypoxia by causing the adrenals to release epinephrine, a hormone capable of constricting the placenta’s blood vessels.
norm A societal set of expectations about behavior.

normative/descriptive period     A period in motor development history that emphasized norm-referenced standardized tests for measuring motor performance.

normoglycemia     An acceptable level of blood sugar.

norm-referenced (NR) assessment instruments     Quantitative evaluations designed to compare an individual‘s skills and abilities with those of others from similar age, gender, and socioeconomic groups.

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obesity     In adults, having a BMI greater than 30 kg/m2 and/or waist circumference exceeds 102 cm (40 in) in men or 88 cm (35 in) in women (ACSM, 2014)

object play     Play involving interaction with toys or tangible objects.

object-control skills     A category of object manipulation skills that includes overarm throwing, one- and two-handed catching, and striking objects both with and without an implement.

objectivity     Also known as interrater reliability, the degree of accuracy to which a test is scored.

osteoblast     A bone building cell that lays down new bone on older bone.

osteoclast     A bone removing cell that reabsorbs old bones.

osteopenia     The condition of low bone mass density (BMD) that results in osteoporosis.

osteoporosis     A disease characterized by a loss of bone mineral to the point that it renders a bone susceptible to fracture.

otolith organs     A subsystem of the inner ear that is primarily responsible for detecting linear acceleration, providing information concerning the body’s position in relation to the force of gravity.

overuse injuries     Injuries that occur as a result of placing the muscular and skeletal system under repeated stress over long periods.

overweight     A BMI in adults between 25.0 kg/m2 and 29.9 kg/m2.

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palmar grasp reflex     A reflexive response to tactile stimulation of the palm of the hand that causes all four fingers of the stimulated hand to flex or close.

palmar mandibular reflex     A reflex elicited by applying pressure simultaneously to the palm of each hand, eliciting all or one of the following responses: the mouth opens, the eyes close, and the neck flexes, tilting the head forward.

palmar mental reflex     A reflex that elicits a facial response, an opening and closing of the mouth, when the base of the palm of either hand is scratched.

parachuting reflexes     Reflexes that occur when the infant is tipped off balance in any direction stimulating a protective movement of the arms in the direction of the potential fall.

parallel play     Play involving two children playing side by side but interacting very little though they may display an awareness of each other and may even subtly copy each other’s play behavior through observation and imitation.

peak height velocity (PHV)     The maximum rate of growth in body height.

peak weight velocity (PWV)     The maximum rate of growth in body weight.

peer group     A social group, especially important during late childhood and adolescence, in which members seek approval and feel attachment and comfort. The group exerts a strong influence on members and their life decisions.

periodization     Variation in training volume and intensity.

peripheral vision     Vision to the sides of the eyes resulting in a visual field that covers slightly over 180 degrees.

phase I reaching and grasping     Infant reaching behavior that occurs in the first few weeks of life and reoccurs at around 4 months and that is characterized by simultaneous reaching and grasping, one-handed reaching, and visual initiation of the reach and the grasp.

phase II reaching and grasping     Infant reaching behavior generally beginning around six months of life that is characterized by two handed reaching, a visually initiated and guided reach, and tactile control of the grasp.

phenylketonuria (PKU)     A birth disorder caused by a disturbance in amino acid metabolism as a result of inheriting a gene that suppresses the activity of the liver and which can cause significant delays in motor milestones.

physical working capacity     The human body’s ability to sustain physical work for extended periods directly related to its ability to transport oxygen to the working muscle tissue.

physiological functioning capacity (PFC)     The capacity to undertake the physical tasks of daily life with success and with a given level of ease.

pictorial stage     A drawing stage characterized by increasing precision and complexity of a child’s pictures.

place kicking     Kicking in which the ball is placed either on the ground or on a kicking tee.

plantar grasp reflex     A reflex evoked by applying slight pressure to the ball of the foot, causing all the toes of that foot to flex.

play     An activity that is usually enjoyable and that the participant cherishes. It is a major socializing force and crucial to learning the rules of society.

play-based assessment     A type of informal assessment that often involves either unstructured or structured motor play.

polypharmacy     The use of multiple drugs simultaneously and often an overmedication of an individual that results in a negative interaction among drugs, such as dizziness or difficulty in balance.

postformal operations     A hypothetical or proposed fifth stage of development for Piaget’s stages of cognitive development that continues into later adolescence and adulthood and is characterized by a more flexible, logical, and complex form of thought.

postural control     Also known as balance, a state of equilibrium in which the desired body posture is maintained.

postural reflexes    Reflexes believed to be related to the development of later voluntary movement like crawling, standing, or walking.

postural sway     A balance related phenomenon characterized by a nearly imperceptible back-and-forth motion that assists the body in maintaining an upright or standing position.

power lifting     A sport that involves performing maximum lifts, such as the squat, bench press, and dead lift.

preadapted period     A period in human motor development in which infant reflexive behavior is being integrated into functional voluntary movement like reaching and grasping, head and neck control, sitting, standing, and independent walking.

precursor period     A period in motor development history in which descriptive observation was established as a method for studying human development.

prehension     The act of grasping, including approaching, grasping, and releasing objects that is critical to the development of a multitude of hand movements used throughout the lifespan.

preoperational stage     Piaget’s second major stage, beginning at around 2 years and spanning the next 5 years in which the child becomes more imaginative in play and recognizes that everyone views the world from a slightly different perspective. Language development is one of the most important characteristics of this stage.

presbyopia     The inability to focus clearly on near objects.

pretend play     A type of play in which children create imaginary representations with objects in the environment.

Primitive Reflex Profile     A tool designed to examine the status of the infant reflexes that allows the examiner to quantify of the level of presence or strength of primitive reflexes.

primitive reflexes     The infant reflexes that serve predominantly for survival through protection and nutrition.

procedural knowledge     Understanding a procedure or knowing how to do something.

process approach     An investigational approach to motor development that emphasizes the movement itself (technique) over attention to the movement’s outcome.

process-oriented assessment     Assessment more concerned with the process or technique used to accomplish a task than the final outcome of performance (how far was the ball thrown).

process-oriented period     A period in motor development history characterized by a return to studying the processes underlying motor development rather than simply describing change.

product approach     An task-oriented approach to measuring movement that emphasizes the end result or outcome of movement over the process or technique of the movement.

product-oriented assessment     Assessment concerned more with performance outcomes (how far was the ball thrown) than the technique used to perform a task.

pronate grasp     An immature handwriting hand position where all four fingers and the thumb wrap around the writing implement in a palm down position; a more mature technique than the supinate grasp.

proprioceptive system     A group of sensory receptors located in the joints, muscles, tendons, and labyrinth of the inner ear that makes it possible for people to be aware of their own movements and to perceive the location of their body parts in space without visual reference to them.

proximodistal     A developmental direction in human growth and motor development proceeding from central portions of the body outward toward the periphery of the body (e.g., out to the fingers and down to the toes) Growth or development proceeding from those points close to the body’s center to those points close to the periphery, or farthest from the body’s center.

psychometric     The quality of being derived from statistical procedures.

psychomotor     Voluntary or volitional movements initiated by an electrical impulse from the higher brain centers (i.e., brain’s cortex), excluding involuntary movements initiated in the lower brain centers or the central nervous system (e.g., reflexive behavior).

pull-up reflex     A reflex elicited by placing the infant in a supported standing or sitting position, holding the baby’s hands, and carefully tipping the child in any direction, causing the supporting arm(s) to flex or extend in an apparent effort to maintain the upright position.

punting     Kicking in which an airborne ball is struck with the foot.

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quantitative evaluations     Evaluations determined through data collection and the use of statistics.

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reaction time     The time it takes for an individual to respond to a stimulus.

readiness     The establishment of the minimum characteristics necessary for the acquisition of a particular human behavior.

recumbent length    Total body length as measured in the supine position.

reflexive period     A period of motor development that occurs during the last third (approximately three months) of the prenatal state, as well as the initial weeks following birth, during which the infant reflexes develop and are critical to the child’s survival and serve as a necessary stepping stone to both cognitive (intellectual) and motor development.

releasing     Relaxing the muscles in the arm sufficiently to permit the release of an in-hand object and one of the final acquisitions in the infant reaching, grasping, and releasing progression.

resistance training     Training that involves the use of various resistance exercises to enhance physical fitness or to increase muscular strength, muscular endurance, and power for sports participation.

retina     The eye’s light-sensitive tissue.

Rh factor     An antigen protein contained in red blood cells that is incompatible with Rh-positive cells.

rods     Photoreceptors within the eye’s retina that make colorless night vision possible.

role conflict     An emotional trauma that may develop out of the mismatch between the gender role that the adolescent considers appropriate or desirable and the gender role that the relevant society views as appropriate.

Romberg’s sign     A disease that causes varying degrees of damage to the sensory receptors, usually those in the soles of the individual’s feet.

rubella     A highly contagious virus characterized by swollen lymph nodes, mild fever, headache, aching joints, and a pink rash on the face, body, arms, and legs that can cause damage to a developing fetus.

running     A form of human locomotion characterized by an alternate support phase and an airborne or flight phase; the airborne phase distinguishes walking from running.

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saccadic eye-movement system     A component of the ocular-motor system in which the eye makes jerky movements and detects and corrects differences between a projectile’s location and the eye’s fixation.

saccadic movements     The micro-adjustments that the eyes make in order to work together as they scan a line of words on a written page or sweep across a horizontal or vertical landscape.

sarcopenia     An “age-related, involuntary loss of skeletal muscle and the corresponding strength” that can occur as a result of disuse but may also occur as a result of typical biological (e.g., hormonal) changes that accompany older age (Walston, 2012, p. 1).

scribbling stage     The first stage in the acquisition of the hand–eye coordination necessary for drawing and characterized by no apparent objective in the writing or drawing process or product.

search reflex     A reflex elicited by softly stroking the area of the face surrounding the mouth causing a turn of the head in the direction of the stimulus.

self-esteem     The degree to which a person believes himself or herself to be competent, successful, significant, and worthy.

semicircular canals     A vestibular apparatus consisting of fluid-filled ducts that lie at right angles to one another that are capable of registering changes in head motion.

semimental functioning     Piaget’s term for cognitive development, which enables the replacement of “thinking with the body” by thinking with the mind.

senile miosis     A restriction of light caused by a decrease in the pupil’s resting diameter.

senile ptosis     A drooping of the upper eyelid that decreases field of vision.

sensorimotor stage     Piaget’s first stage of cognitive development, which spans the first two years of life, in which knowing and thinking emerge as a result of action that occurs via bodily movement.

seriation     The ability to arrange a set of items by certain characteristics like length.

sickle-cell disease (SCD)     A disease that occurs when offspring inherit two defective genes for hemoglobin, which causes red blood cells to change from a doughnut shape to a sickle shape resulting in anemia, impaired blood supply to organs, and enlargement and fibrosis of the spleen.

sickle-cell trait (SCT)     A genetic disorder of the red blood cells caused by a mutation in the parental gene for hemoglobin. SCT is generally asymptomatic.

simple reaction time     How quickly an individual responds to one stimulus.

sit-and-reach test     A flexibility test of the hamstring, back, and hip.

sitting height     The height of an individual measured from the vertex and their sitting surface.

skeletal age     The most widely accepted measure for determining stage of maturation that uses predictable changes in bone structure.

skinfold calipers     A tool used to estimate body composition indirectly.

skip     A movement consisting of a forward step followed by a hop on the same foot with an alternating leading leg.

slide     A movement consisting of a sideways step followed by a leap onto the trailing foot.

small for gestational age (SGA)     A birth weight classification indicating the child’s size is 2 standard deviations below their expected birth weight for length of gestation.

smooth ocular–motor pursuit system     A component of the ocular–motor system capable of matching eye-movement speed to the speed of a projectile, thus maintaining a stable retinal image.

Snellen eye chart     A chart that is used to determine static visual acuity, the most common technique being an individual reading the smallest letters possible on the chart.

social role     “A special position an individual possesses within a network, which indicates his or her behaviours, expectations, and responsibilities” (Abnar, Takaffoli, Rabbany, & Za¨ıane, 2014, p. 289).

socialization     “A process of learning and social development which occurs as we interact with one another and become familiar with social worlds” (Coakley, 2015, p. 52).

somatotype    Heath and Carter’s (1967) modification of Sheldon’s approach to classifying physique to include not only photographic but also anthropometric procedures.

speed/accuracy trade-off     A form of compensation in which individuals are willing to sacrifice speed for accuracy.

stability     A category of voluntary movements that includes a wide range of movements, from head control to the eventual attainment of upright posture.

stage     A particular time in the human lifespan characterized by behaviors that are thought to be unique to that time period.

stair climbing     Movement typical to infants at roughly 13 months of age in which they are able to ascend and descend stairs without assistance.

standard deviation     A linear measure of variability that measures the degree to which the scores vary about the mean of the distribution.

startle reflex     A reflex that can be elicited by a rapid change of head position or striking the surface that supports the baby, as well as most any unexpected and abrupt stimulus causing the arms and legs to flex immediately.

state anxiety     A transient emotional state characterized by feelings of apprehension and physical responses such as increased heart rate, rapid breathing and sweaty palms that can occur as a result of achievement-oriented activities, such as sports or academics.

static balance     The ability to maintain a desired body posture when the body is stationary.

static balance     Balance that occurs when the base of support remains constant and only the center of body mass moves.

static force     Force exerted against an immovable object with no or very little change in the length of the exercised muscle.

static visual acuity     Visual acuity when both the target and the performer are stationary determined by the Snellen eye chart.

stature     The measurement of total body length as standing height, the distance between the vertex and the floor.

stepping reflex     A reflex elicited by holding the infant upright with the feet touching a supporting surface putting pressure on the bottom of the feet. The stimulus on the bottom of the feet results in a walking-like action of the legs.

stereotypies     Rhythmical, patterned, seemingly centrally controlled infant movements (e.g., fingers, arms, legs, feet, torso, mouth) believed to be relatively intrinsic like reflexes; however, unlike reflexes the stimulus for the movement is unknown.

stimulation     Efforts by caregivers and society to enhance aspects of children’s development through methods, products, and programs.

strabismus     An eye condition common at birth in newborns that causes both eyes to move at random, which should not persist beyond the first year.

strategic compensation     A series of unique compensatory steps older adults may take to improve the safety of their driving.

stress     The physical and emotional tension felt as a result of a person facing challenges.

striking     A fundamental movement in which the performer uses a designated body part or some implement to project an object.

stroke volume (SV)     The volume of blood that is ejected from the left ventricle into general circulation via the aorta.

subcortical     Below the level of the cortex of the brain.

subcutaneous adipose tissue     Fat tissue found directly below the skin.

sucking reflex     A sucking response elicited when the lips are stimulated, such as by the touch of the mother’s breast or a finger. This stimulation evokes both the creation of a negative intraoral pressure as the sucking occurs. The tongue also applies a positive pressure; it presses upward and slightly forward with each sucking action.

sudden infant death syndrome (SIDS)     The death of an infant in its sleep due to cessation of breathing.

supinate grasp     An immature handwriting technique where all four fingers and the thumb wrap around a writing implement with the palm up; a less mature technique than the pronate grasp.

support phase     A phase in walking or running when balance is maintained on only one foot.

swimming reflex     A reflex elicited when the baby is held horizontally causing the movement of the arms and legs in a well-coordinated swimming-type action.

swing phase     A phase of the gait cycle in which the foot or toes of one leg leave the supporting surface and ends when the heel or foot of the same leg contacts the ground again.

symmetric tonic neck reflex     A reflex elicited by placing the baby in a supported sitting position and tipping the infant backward far enough that the neck eventually extends, causing a corresponding symmetrical extension of the arms and flexion of the legs. However, if the baby is tipped forward until the neck is fully flexed, the arms flex and the legs extend.

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teratogen     An environmental agent that causes harm to the embryo or fetus.

test battery     A group of tests designed for a specific purpose, e.g., to assess the physical fitness of older adults.

test reliability     An indicator of the consistency of measurement.

testosterone     A steroid hormone that develops male secondary sexual characteristics.

thalidomide     A tranquilizing drug responsible for more than 5,000 malformed births in West Germany affecting the tissue or organ system that was growing and developing the fastest at the time of exposure.

throwing     An object control skill in which an object is propelled through the air via the hand and arm.

toxoplasma gondii     A protozoan parasite that infects the fetus and causes mental retardation and convulsions.

tracking     Visually following a projectile in order to gain information regarding the object’s height.

transductive reasoning     A characteristic of the preconceptual substage of Piaget’s preoperational stage of development in which the child assumes that a cause-and-effect relationship exists between two events occurring simultaneously.

triple marker     Three substances (human chorionic gonadotropin, unconjugated estriol, and alpha-fetoprotein) produced by the mother’s placenta and fetus that can be screened in order to identify Down syndrome.

Type I muscle fibers     Slow-twitch muscle fibers.

Type II muscle fibers    Fast-twitch muscle fibers.

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ultrasound     A test administered by placing a small transmitter on the abdomen of a pregnant woman in order to provide details about the baby and show the placement and structure of the placenta.

unilateral dominance     A characteristic of individuals who are right-eyed and right-handed or left-eyed and left-handed.

upright bipedal locomotion     Locomotion characterized by a progressive alternation of the leading leg and continuous contact with the supporting surface.

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velocity curve     A graphical measurement that plots increments of change in growth per unit of time.

vertex     The highest point on the skull.

vertical jump     A jump in which the body is projected upward into the air by force generated in one or both legs.

vestibular apparatus     A system located in the inner ear that is responsible for registering head motion and accompanying body motion.

visual acuity     The ability to see detail in an object.

visual cliff     The platform used in Gibson and Walk’s 1960 study that created the appearance of a drop-off or cliff and demonstrated that infants are capable of organizing depth clues during the first year of life.

visually guided reaching     Reaching that is both visually initiated and visually controlled.

voluntary movement     Movement that appears after the fourth postnatal week that is not governed by reflexes and is performed a result of conscious or volitional effort.

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walking     Locomotion characterized by a progressive alternation of the leading leg and continuous contact with the supporting surface.

weight lifting     A sport that involves performing maximum lifts, such as the snatch, clean, and jerk.

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