Adolescence: Understanding Physiological Changes During Exercise

Transcription

1 Adolescence: Understanding Physiological Changes During Exercise Heather Nettle, MA, ACSM EP-C Exercise Physiologist Health and Wellness Director Paul and Carol David YMCA YMCA of Central Stark County Adolescents Are Not Tiny Adults Adolescents are specialized population Differences in physiology Cardiovascular Strength Growth Potential Should be considered in programming Physiological and psychological considerations Presentation Title l October 27, 2016 l 2 Distinctions in understanding physiology Maturity level Gender Activity level Experience with exercise Presentation Title l October 27, 2016 l 3 1

2 Tanner stages of development Presentation Title l October 27, 2016 l 4 Hormonal Impact of Exercise Presentation Title l l 5 Physiological Considerations Recent studies have indicated hormones play a role in exercise metabolism: Hormones can influence ventilation, metabolism, and thermoregulation. Studies indicate menstruating females burn more fat and fewer carbohydrates at a specified intensity than males. Thermoregulation is influenced by cycle timing. Studies to determine why are difficult. Difficult to control for variables (apples to oranges). Lack of studies in kids and females Further studies are needed. Presentation Title l l 6 2

3 Estrogen and Progesterone Estrogen: Studies indicate estrogen increases lipid oxidation and decreases carbohydrate oxidation. Decreased rate of glycogen use during exercise. Glycogen sparing can occur. Decreased CHO oxidation may be secondary to estrogen induced FFA availability and oxidation. Progesterone: Appears to decrease fat metabolism. May be due to uploading the translocation of GLUT-4 glucose transport proteins Progesterone and estrogen appear to have an inverse relationship with exercise metabolism. Presentation Title l l 7 Questions on Hormonal Influence in Menstruating Females Animal studies are more conclusive than humans. Age influence Insulin resistance and hormone influence Variation in cycles Unknown mechanism Primary decrease in glucose availability or uptake by the muscle Secondarily in a response to an increase in FFA availability Progesterone s role is less well known than estrogen Presentation Title l l 8 Testosterone Biological effects include increased muscle growth Promotes protein synthesis Suppresses protein degradation Mechanism is modulated through the interaction of testosterone with the intracellular androgen receptor (AR) Presentation Title l October 27, 2016 l 9 3

4 Hormone Roles in Adolescent Males Until puberty, children do not experience an increase in testosterone with strength exercise At puberty, boys begin to show increases, but girls do not. Testosterone levels do not increase enough to warrant hypertrophy until Tanner Stage 4 Age can be dependent on individual Cardiovascular Exercise in the Adolescent Most ranges for maximal VO2 in children have been calculated based on formulas determined from adult physiology They do not account for several errors Children typically have a higher heart rate response and have a wider range of response than adults Cardiovascular Exercise in the Adolescent Error in estimations 26% in girls 23% in boys VO2 Plateaus vs. Maximal VO2 Children do not typically show a plateau in VO2 to exhaustive exercise Different from adults Maximal tests are determined by child s perception of exhaustion Limiting testing indicates children s heart rate response decreases to approximately 95% by the time exhaustion is reached 4

5 Adolescent Strength Training Changes In Attitude Historically, strength training has been considered unhealthy for adolescents. Recent research indicates that strength training can be beneficial to adolescent individuals. Support for Adolescent Strength Training American College of Sports Medicine National Strength and Conditioning Association American Orthopaedic Society for Sports Medicine Among others What does Strength Training consist of? It is a specialized method of physical conditioning that involves the progressive use of a wide range of resistive loads to enhance or maintain one s ability to exert or resist force. JOPERD 5

6 Previous fears and misconceptions for strength training have been resolved through safety. Previous Misconceptions: Damage to the spine and/ or growth plates Stunted growth Acute and chronic musculoskeletal injuries Loss of flexibility Increases in blood pressure of hypertensive adolescents Refuting Previous Evidence Most epiphyseal injuries that had previously been reported with skeletally immature individuals occur in the wrists and spine. Now they are relatively uncommon and can be prevented by: The use of proper technique Knowledgeable supervision Avoidance of maximal lifts. Refuting Previous Evidence Research now shows that linear growth is not affected by strength training. Increases in motor recruitment may aid in the prevention of injuries due to improved coordination. Whether increases in strength prevent injuries is inconclusive in adolescents. 6

7 Refuting Previous Evidence Flexibility loss can be combated with the addition of stretching exercises after strength training. Increases in blood pressure can be seen during the isometric lift, however, dangerous spikes can be minimized with proper breathing. What forms of strength training are appropriate? Machine weights (low weight) Free weights (low weight) Calisthenics Bands Ball Exercises Pilates Prevalence of Injury in Maximal Lifting Limited data suggests that adolescents may be more prone to injury while lifting maximal weight During growth, the epiphyses appear to be especially vulnerable to injury at this time Appropriate age for maximal lifting should be based on physical maturity 7

8 Maximal and Power Lifting Resistance training should gradually increase muscular strength and use high repetitions. The goal of maximal and power lifting is to lift a maximal amount of weight a few times. Maximal and Power lifting should not be permitted by adolescents. Free Weights and Machine Weights According to the American Academy of Pediatrics and the American Orthopaedic Society of Sports Medicine: Intense free weight and machine weight training should be avoided until Tanner stage 5 (near physical maturity) Those younger than stage 5 will most likely not be able to use high weights until later because of the complexity and size of the machines Strength and Hypertrophy Children and young teens do not typically gain significant size or tone in the muscle. Increases in strength are attributed to the gradual increase in muscular recruitment. 8

9 Benefits of Resistance Training Increased Muscle Strength Increased Bone Mineral Density Improved Blood Lipid Profile Improved Body Composition Possible Increased Resistance to Injury Enhanced Psychosocial Well Being Improved Attitude Towards Lifetime Fitness Initiation of Positive Training Habits Decrease in Blood Pressure (In hypertension) Improved Preparation for Athletic Activity Variability of Fitness Programs to Prevent Boredom Improved Neuromuscular Coordination Obese and Overweight Adolescents In the last decade, juvenile obesity has risen to 20% 50% of obese children are likely to become obese adults Instances of chronic disease in youth are increasing Obese and Overweight Adolescents Strength training can increase lean tissue in sedentary children Cardiovascular exercise can help improve body composition and cardiovascular conditioning Increased activity increases caloric expenditure Ensures healthy habits for reduction of instances of adult obesity 9

10 Reducing the Health Risks of Obese and Overweight Adolescents Exercise can improve the metabolism of sedentary children. It can delay or prevent the onset of Type II Diabetes. It can prevent or aid in lowering hypertension. It can aid in the lowering of cholesterol. It can decrease the risk of heart disease. A variety of different exercises should be included to hold the interest of previously sedentary youths. Diet intervention is critical Psychological and environmental aspects should be considered Psychological Effects of Fitness Children become more confident in their physical abilities. They are more likely to try other sports and physical activities. They show an enhancement in well being. They have a sense of accomplishment and pride (strength gains are easily seen). Psychological effects improve linearly with long term commitment to fitness. What to Avoid 1. Do not compare one adolescent to another: they all will train and show gains differently. 2. Do not allow for an adolescent to train too frequently. 3. Do not allow an adolescent to train without supervision. 4. Do not allow adolescents to increase work loads until you feel they are ready. 5. Do not criticize an adolescent s ability to do the exercise. 10

11 Helpful Guidelines 1. Provide simple and clear verbal instructions. 2. Provide precise exercise demonstrations. 3. Supervise attentively for each session. 4. Encourage proper technique and posture. 5. Keep parents informed of progress and performance. 6. Keep training fun, but stress the seriousness of the activity. 7. Children should be able to describe and demonstrate each activity. 8. Vary the types of exercise to avoid boredom. 9. Keep track of progress. 10. Progress from simple to complex exercises. 11. Provide positive reinforcement. The Purpose Exercise should concentrate on learning proper form and positive habits. Strength, initially should not be the primary goal. Mechanics and posture should be mastered before increasing weight and attempting to build strength. Detraining Adolescents lose the strength gains more quickly than adults. After 6 weeks of cessation of resistance training, gains are lost, and the body has returned to baseline. Children maintain cardiovascular conditioning at a better rate than adults. Flexibility can be variable dependent upon growth. Neurological adaptations can vary dependent upon development and previous fitness history. 11

12 References ACSM s Guidelines for Exercise Testing and Prescription, 6 th ed. Lippincott, Willams and Wilkins; 2000: Philadelphia. ACSM s Resource Manual for Fuidelines for Exercise Testing and Prescription, 4 th ed. Lippincott, Williams, and Wilkins; 2001: Philadelphia. Armstrong, Neil, and Joanne R. Welsman. "Assessment arid Interpretation of Aerobic Fitness in Children and Adolescents." Exercise and sport sciences reviews 22.1 (1994): Benjamin, H J, Glow, K M. Strength Training for children and adolescents. Physician and Sports Medicine; Sep 2003, v31 i9, p19 (8). D Eon, T. and B. Braun. The Roles of Estrogen and Progesterone in Regulating Carbohydrate and Fat Utilization at Rest and During Exercise. Journal of Women s Health and Gender Based Medicine. 2002: v. 11, No. 3, pp Emaus, A., M. B. Veierod, A.S. Furberg, S. Espetvedt, C. Griedenreich, P.T. Ellison, G. Jasienska, L.B. Andersen, and I. Thune. Physical Activity, Heart Rate, Metabolic Profile, and Estradiol in Premenopausal Women. MSSE: 2008, v. 40, no. 6, pp Faigenbaum, A, Zaichkowsky, L D. Psychological effects of strength training on children. Journal of Sport Behavior; Jun 1997, v20 i2, p 164 (12). References Faigenbaum, A. Strength training and children s health. The Journal of Physical Education, Recreation, and Dance; Mar 2001, v72 i3 p 24 (12). Faigenbaum, A, Miliken, LA, LaRosa Loud, R, Burak, B, Doherty, CL, and Westcott, W. Comparison of 1 and 2 days per week of strength training in children. Research Quarterly for Exercise and Sport; Dec 2002, v73 I4 p416 (9). Watts, Katie, et al. "Exercise training in obese children and adolescents." Sports Medicine 35.5 (2005): Marshall, William A., and James M. Tanner. "Variations in pattern of pubertal changes in girls." Archives of disease in childhood (1969): 291. Marshall, William A., and James M. Tanner. "Variations in the pattern of pubertal changes in boys." Archives of disease in childhood (1970): McKinney, K., C. Radecki Breitkopf, and A. B. Berenson. Association of Race, Body Fat, and Season with Vitamin D Status Among Young Women: A Cross Sectional Study. Clinical Endocrinology. 2008: 69, pp Nettle, Heather, and Elizabeth Sprogis. "Pediatric exercise: truth and/or consequences." Sports medicine and arthroscopy review 19.1 (2011): Vingren, Jakob L., et al. "Testosterone physiology in resistance exercise and training." Sports medicine (2010): Thank You! 12