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Exercise Physiology In Pediatrics

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Exercise Physiology In Pediatrics

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