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UNIT_4 - MAJOR PRINCIPLES OF TRAINING TRAINING 1 Overload...

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Unformatted text preview: MAJOR PRINCIPLES OF TRAINING TRAINING 1 Overload Principle: A system does not system improve until it is forced to perform above and beyond the normal/usual daily demands. beyond • Overload can be accomplished by increasing Overload Intensity, Frequency, or Duration either alone or in combinations. or Frequency Overload Frequency The effect on an untrained VO2max 25 % Change in VO2max 20 15 10 5 0 0 1 2 3 4 5 Exercise Frequency (days per week) Duration Overload Duration The effect on an untrained VO2max 25 % Change in VO2max 20 15 10 5 0 0 15 30 45 Exercise Duration (minutes per workout) Intensity Overload Intensity The effect on an untrained VO2max 35 % Change in VO2max 30 25 20 15 10 5 0 0 40 70 80 Exercise Intensity (% VO2max) MAJOR PRINCIPLES OF TRAINING TRAINING 2 Specificity of Training: The only system Specificity that improves is the system which is overloaded. overloaded. (Multi-dimensional activities require variety in the training programs) variety Specificity of Training Specificity Cyclists Running VO2max Cycle VO2max Arm VO2max Rowers Runners 0 50 100 Specificity of Training Specificity Endurance Training Sprint Training Endurance Training Sprint Training 0 5 10 0 5 10 % Change VO2max % Change in ATP-PC System MAJOR PRINCIPLES OF TRAINING TRAINING 3 Heredity The success of a training program is The limited by genetic endowment. limited e. g. Body type, gender, initial system e. levels, adaptation capacity, adaptation rate, etc. rate, MAJOR CONSIDERATIONS IN DESIGNING TRAINING PROGRAMS PROGRAMS Which System(s) Do I Train? – Performance is composed of several factors Factors Affecting Performance Most activities require the use of several systems of Immediate & Glycolysis 0 %Anaerobic 100 10 90 20 80 30 70 40 60 50 50 60 40 Oxidative 70 30 80 20 90 10 100 0 %Aerobic I---------I--------I--------I-------I--------I--------I--------I--------I--------I---------I I Distance (m) 100 Time (min:sec) 0:10 I 200 0:20 I 400 0:45 I 800 1:45 I 1.5k 3:45 I 3.2k 9:00 5k I 14:00 I 10k 29:00 I Marathon 135:00 Training Considerations Training Neuro-Muscular System Desired Result: Improved power Desired generating ability generating 1. Hypertrophy or hyperplasia? 2. Fast or slow myosins? Training Considerations Training Metabolic Systems Desired Result: Reduced rate of fatigue Desired (increased rate of ATP resynthesis. (increased 1. Increased number of metabolic system enzymes. 2. Increased availability of energy substrates. * 3. Increased removal of metabolic by-products 3. (e.g. NH3, lactate, CO2)* (e.g. * need help from improved cardio-respiratory system Training Considerations Training Cardio-Respiratory Systems: Desired Result: Improved delivery and removal Desired systems. (Note: If one improves VO2 max this result systems. will occur) will 1. Increase stroke volume 1. 2. Alter blood factors (e.g. #RBC, plasma volume, etc) 2. 3. Increase a-v O2 difference (need to improve metabolic 3. systems) systems) BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Immediate System 1. Increased muscular 1. stores of ATP and CP stores Percent Increase 40 35 30 25 20 15 10 5 0 ATP CP Typical increase seen in Typical untrained following > 8 wk of training ===> wk BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Immediate System 2. Increased concentration 2. and activity of system enzymes (e.g. CPK & MK) enzymes Typical increase seen in Typical untrained following > 8 wk of training ===> wk 40 35 Percent Increase 30 25 20 15 10 5 0 MK CPK BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Immediate System 3. Altered myosin type 3. and cross-bridge numbers and Typical relative fiber areas of Typical selected athletes ======> selected Distance Untrained Middle Middle Distance Distance Jumpers Shot & Discus Sprinters 0 20 40 60 80 Percent Slow-Twitch Fiber Area BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Muscle glycogen g/Kg muscle) Glycolytic System 1 Increased Glycogen Increased storage (>2x) storage 20 weeks of intense 20 training ===> training 35 30 25 20 15 10 5 0 Before After BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Glycolytic System 2 Increased concentration Increased and activity of glycolytic enzymes. enzymes. HK PFK 0 20 40 60 80 100 120 Percent Increase BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Glycolytic System Percent Increase 28 24 3 Increased concentration Increased and activity of gluconeogenic enzymes. gluconeogenic Increased conversion into Increased glucose ===> glucose 20 16 12 8 4 0 Alanine Lactate BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Oxidative System Percent Increase 150 1 Increased Glycogen Increased storage. storage. 2 Increased muscular Increased stores of triglycerides. stores 100 50 0 Glycogen TRIGLY BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Oxidative System Myoglobin 3 Increased myoglobin. 4 Increased concentration Increased and activity of pyruvate handling enzymes. handling 5 Increased concentration Increased and activity of betaand oxidation enzymes. Pyr-enz Beta-Ox 0 20 40 60 80 100 120 Percent Increase BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Oxidative System 6 Increased Lipolysis. After Before 0 2 4 6 7 Increased hormone Increased sensitivity. Improvement Range = 25%-200% sensitivity. Lipolysis Rate BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Oxidative System Number 8 Increased mitochondria Increased number. number. 9 Increased mitochondria Increased size. size. 10 Increased concentration 10 and activity of oxidative enzymes. enzymes. Size Enzymes 0 20 40 60 80 100 120 Percent Increase after 20 weeks BIOCHEMICAL CHANGES IN SKELETAL MUSCLE FOLLOWING METABOLIC SYSTEM FOLLOWING SPECIFIC TRAINING Oxidative System 11 Improved substrate 11 transport mechanisms. transport (e.g. Carnitine enzymes) (e.g. Carnitine Enzymes 12 Increased concentration 12 and activity of hydrogen shuttles. shuttles. G-P Shuttle 0 10 20 30 40 50 Percent Increase Changes in the C-V system following training (esp. endurance training) (esp. 1. Bradycardia (lowered Heart Rate) (lowered a. Increased a. Parasympathetic drive. Parasympathetic b. Decreased sympathetic b. drive. drive. c. Lower Intrinsic Heart c. Rate (a.k.a. atrial rate) Rate M Untrained F Untrained F Runners M Runners 0 20 40 60 80 Resting Heart Rate (bpm) Changes in the C-V system following training (esp. endurance training) (esp. 2. Increased 2. Stroke Volume Stroke M Runners F Runners M Untrained F Untrained 0 40 80 120 Resting SV (ml) Changes in the C-V system following training (esp. endurance training) (esp. 2. Increased SV because: M Runners a. Increased blood volume F Runners M Untrained F Untrained 0 2 4 6 8 Blood Volume (liter) Changes in the C-V system following training (esp. endurance training) (esp. 2. Increased SV because: M Runners M Anaerobic Athletes b. Increased heart size and b. volume volume F Runners M Untrained F Untrained 0 11 22 33 44 55 L Ventricle Size (mm) Changes in the C-V system following training (esp. endurance training) (esp. 2. Increased SV because: M Anaerobic Athletes M Runners c. Increased contractility c. (i.e. thicker walls = more x-bridges) (i.e. F Runners M Untrained F Untrained 0 2 4 6 8 10 12 14 Ventricle Wall (mm) Changes in the C-V system following training (esp. endurance training) training 2. Increased SV because: d. Increased distensibility e. Increased venous tone f. More rapid filling of the ventricles Changes in the C-V system following training (esp. endurance training) (esp. M Runners 3. Increased Hemaglobin F Runners M Untrained F Untrained 0 250 500 750 1000 Hemaglobin (g) Changes in the C-V system following training (esp. endurance training) training 4. Increased number of capillaries per muscle cell. 8 7 6 Untrained Trained Capillary # 5 4 3 2 1 0 Type I Type Iia Type Iib How training adaptations increase fat utilization and spares glucose. spares How training adaptations decrease lactate production and make it easier to maintain blood pH. make Changes in Maximal Work Induced by Training Changes 1. Increase in VO2max Increased Cardiac Output 1. Increased Stroke Volume 2. Increased max Heart Rate? -Most efficient HR~187 bpm -training brings max HR closer or keeps it closer to 187 (slower decline with age) Increased a-v O2 difference 1. Increased mitochondria 2. Increased myoglobin 3. Increased hemaglobin 4. Increased capillaries Changes in Maximal Work Induced by Training Changes 1. Increase in VO2max Changes in Maximal Work Induced by Training Training Increased Lactate Production --increased amount of the glycolytic enzymes --increased amount of stored muscle glycogen Changes seen during sub-maximal exercise following training 1. No change in sub-max VO2 at a given workload. -- Energetic need to perform a set workload never changes. 2. No change in sub-max Q at a given workload. 3. Increased stroke volume -- increased heart volume & increased contractility, etc. 4. Decreased heart rate -- decreased sympathetic drive & decreased atrial rate. 5. Increased oxygen extraction. -- slower blood flow per mass of active muscle. Changes seen during sub-maximal exercise following training 6. Decreased lactic acid accumulation -- increased mitochondria -- increased FFA utilization -- increased usage of lactate as a fuel -- decreased use of glycogen & glucose OVERTRAINING (staleness): OVERTRAINING Imbalance between high volume (duration and/or frequency) and/or high intensity training and adequate recovery/nutrition. (i.e. The person does not let the body have adequate to recover form the exercise before exercising again.) Frequently happens in individuals who have reached their genetically determined maximum. Overtraining results in reduced performance, improper biologic functions, increased injury, and depression Symptoms of Overtraining Symptoms DETRAINING: DETRAINING: Loss or reduction in body structure and/or functions caused by a reduction or stoppage of current training program. DETRAINING: DETRAINING: Metabolic pathways a. The greatest loss (~50%) is seen in the first week of detraining. b. Return to pre-training levels occurs in ~4-6 weeks Detraining Loss of Strength/Muscle atrophy: Muscle atrophy varies with fiber type with slow fibers atrophying sooner than fast. Strength gains are lost slowly (only complete inactivity, i.e. bed rest, casting, space flight, causes fast losses). Most individuals can maintain strength gains for up to 8 weeks. After 12 weeks studies report ~30% loss After 31 weeks strength is still above baseline values. HEART MUSCLE: Detraining (bed rest) for one week caused a 25% decreased in muscle mass. 50% loss occurred after about 4 weeks. Retraining does not occur as fast as Detraining. 100 90 % Change 80 70 60 SDH LDH Max VO2 Run Time 0 Detraining 15 Retraining 30 The body does not respond favorably to cycles of Training/Detraining/Retraining Training/Detraining/Retraining % Change in VO2max 120 115 110 105 100 95 0 2 4 7 9 11 14 16 18 21 Weeks Maintenance of current levels requires training at the usual intensity/duration at least every 3 days (twice per week) 130 Max VO2 105 95 85 Sub-max Lactate 2 day/wk 1 day/wk 0 day/wk 120 % Change 110 100 2 day/wk 1 day/wk 0 day/wk 0 Training 75 65 0 8 12 16 90 8 12 Maintenance 18 Influence of Gender: Influence Men and women respond similarly to training programs. programs. 14 12 % Gain in VO2 10 8 6 4 2 0 Male Female Exercise and Menstrual Disorders Amenorrhea – Cessation of menstruation – Due to multiple factors • Amount of training • Psychological stress • Low body fat Why does Low Body Fat lead to Why Amenorrhea? Amenorrhea? 1. Fatty acids are used to make cholesterol. 2. Cholesterol is used to make gonadal hormones. 3. Therefore, no fat no hormones. Note: Low body fat leads to low testosterone in males. Low testosterone is not as obvious as Amenorrhea. Exercise in Environmental Extremes Extremes Exercise at Altitude Exercise 1. Barometric pressure and air temperature are lower at 1. altitude. This results in altitude. A. Lower PO2 B. Lower air density B. 2. Exercise Performance is Altered A. Lower air density = greater performance in throwing and A. short sprints short B. Lower PO2 = poorer distance/endurance performance Effect of Altitude on Running Performance Performance 25 % Decrease at 4k m (13k ft) 20 15 10 5 0 440 880 1 mile 2 mile Environmental Extremes Terminology Accommodation: The acute changes in body systems caused by exposure to environmental extremes. Acclimatization: The chronic adaptations made by body systems to overcome the effects of extreme environments. Accommodation To Altitude 1. Increased VE CO2 production doesn’t change, thus the amount of CO2 increases (Dalton’s Law) of increases Increased VE causes increased pressure in the lungs which means greater O2 Hb binding lungs Lower PO2 means more breaths are needed to get the same amount of O2 the Accommodation To Altitude 1. Increased VE Accommodation To Altitude 2. Decreased arterial O2 content Note: Decreased atmospheric O2 will lead to a decreased a-v O2 will difference at maximum work. difference Accommodation To Altitude 2. Decreased arterial O2 content 100 Blood O2 Content 90 Rest Exercise 80 70 0 4k 8k Feet Accommodation To Altitude 3. Decreased plasma volume Acute altitude exposure causes diuresis. The decreased fluid volume results in a The concentration of RBCs and Hb. concentration This results in more O2 per ml of blood. Accommodation To Altitude 4. Decreased blood volume If plasma volume is decreased then blood If volume is also decreased. volume Accommodation To Altitude 5. Decreased stroke volume A decrease in blood volume leads to a decrease decreased venous return which leads to a decreased ejection fraction which yields a decreased stroke volume. decreased Accommodation To Altitude 6. Increased resting and sub-max 6. heart rate heart Any given workload maintains its O2 requirement at all altitudes. Therefore the submax VO2 at remains unchanged. remains VO2 = HR x SV x a-v O2 difference. SV decreases and a-v O2 difference decreases. Therefore HR must increase. Accommodation To Altitude 6. Increased resting and sub-max heart 6. rate rate Accommodation To Altitude Altitude 7. Decreased maximal Heart Rate Elevation (feet) 0 5K 10K 15K 20K 25K Percent Decrease 0 5 10 15 20 25 30 35 max HR Accommodation To Altitude 8. Decreased Q Q = HR x SV HR Max HR decreases Max SV decreases Accommodation To Altitude 9. Decreased max VO2 VO2 = HR x SV x a-v O2 difference. Max HR decreases SV decreases a-v O2 difference decreases Accommodation To Altitude Altitude 9. Decreased max VO2 Elevation (feet) 0 5K 10K 15K 20K 25K Percent Decrease 0 10 20 30 40 50 60 70 max VO2 Accommodation To Altitude 10. Increased catecholamine production. 11. Increased blood pressure. 12. Increased lactate production at sub-max work. 13. Decreased lactate production at max work. 13. 14. Anorexia (increases as elevation increases) 14. Especially evident above 15k ft (4.5k m) due to: due Decreased energy intake Decreased Increased use of amino acids for fuel Malabsorption in the GI tract (esp > 18k ft) High Altitude Acclimatization High (1-4 weeks of exposure) 1. Adaptations are improved if altitude exposure is 1. done in steps (i.e. go up 2000 ft every 4-6 months). done 2. Adaptations are more pronounced when exposure 2. happens during the developmental years. happens Adaptations include: 1. Increased number of RBC and Hb. High Altitude Acclimatization High (1-4 weeks of exposure) 2. Increased O2 binding by Hb. (higher in trained than untrained) 3. Increased elimination of bicarbonate in the urine. 4. Increased muscle and lung capilliarization. 5. Increased myoglobin. 6. Increased mitochondria and oxidative enzymes. 7. Catecholamine levels return to sea level values. High Altitude Acclimatization High (1-4 weeks of exposure) 8. Very little change seen in (stay near the altitude 8. accommodation levels): accommodation VE HR Q plasma volume stroke volume blood pressure blood blood volume max VO2 Training at Altitude Training Even though the adaptations to altitude are similar to those seen with Even endurance exercise, training at altitude does not provide an not additional benefit to sea level performances. additional 2 mile run Day 3 after return to sea level VO2 max Day 3 after return to sea level Day 18 of altitude exposure Day 18 of altitude exposure Day 3 of altitude exposure Day 3 of altitude exposure 85 90 95 100 75 80 85 90 95 100 Percent Sea Level Performance Percent Sea Level performance Why doesn’t training at altitude provide any additional benefit? benefit? You can not training at the same level of intensity. Therefore, even though you are training hard you are actually Therefore, detraining detraining Workout Intensity (% of maximum) 100 90 80 70 60 50 40 30 0 4K 8K 10K 12K Altitude (feet) Exercise in Hyperbaric Environments: Breath Holding Diving 1. As you descend the hydrostatic pressure increases -- hyperbaria Depth Pressure Sea level 1 atm 10 m 2 atm 20 m 3 atm 30 m 4 atm Exercise in Hyperbaric Environments: Breath Holding Diving Lung volumes decrease proportionally to increases in atm pressures ATM Lung Volume 1 100% 2 50% (1/2) 3 33% (1/3) 4 25% (1/4) Diving Problems and Concerns 1. Divers Diuresis Increased hydrostatic system increases SBP & DBP (more pressure on vessels) Reduce pressure by reducing blood volume (i.e. fill up bladder) Note: reduced blood volume = decreased stroke volume = increased heart rate Diving Problems and Concerns 2. Lung Barotrauma “Lung Squeeze” On descent, lung air volumes decrease faster than blood volumes within lung. This causes differing pressures between capillaries and alveoli. Thus, blood & fluid enter alveoli. Alveolar Rupture: too much blood in alveoli, and diver “drowns” in his own fluids. Pneumothorax: Lung tissue ruptures, air escapes into thoracic cavity, & collapses lungs. Diving Problems and Concerns 3. Middle-ear squeeze: This can happen in depths of 2-3 ft On descent, Eustachian tube closes (collapses) quickly. This prevents the equalization of air pressure between middle-ear and the outside. Pressure can only be maintained by rupture of the eardrum. Note: NEVER WEAR EARPLUGS!! Diving Problems and Concerns 4. Sinus Squeeze On descent, sinus and nasal passages close (collapse) quickly. Pressures and air volumes in sinuses and nasal cavities cannot equalize. Nasal tissues rupture -- Bloody nose. Note: This happens most often with clogged sinuses (colds, etc). Diving Problems and Concerns 5. Nitrogen Narcosis On descent, nitrogen gets dissolved in the tissues. Increased nitrogen acts as an intoxicant causing euphoria, overconfidence, poor judgement, slow reaction time. (similar to being drunk) Diving Problems and Concerns 6. Gastrointestinal barotrauma On ascent, gas volumes in GI Tract expand quickly leading to severe discomfort and pain unless belching and flatulence occurs. Note: To prevent this it is recommended that carbonated drinks and legumes are not consumed prior to the dive, and no gum chewing during the dive. Diving Problems and Concerns 7. Alterobaric vertigo (ABV) On ascent, air pressure increases quickly in middle ear. If pressure is not equalized quickly (“popping your ears”), the high pressure causes vertigo (dizziness). Vertigo can cause panic which leads to drowning. Diving Problems and Concerns 8. Air embolisms On rapid ascents, if air is not expelled from lungs, large air bubbles occur. Air bubbles can leave lungs and enter blood stream. These bubbles can cause heart attacks, strokes, and hemorrhaging. Diving Problems and Concerns 9. Bends -- Decompression sickness On rapid ascents, nitrogen bubbles form in all tissues causing: blockage & rupture of blood & lymph vessels, rupture of cell membranes, joint problems, compartment syndrome (muscle tissue expands but fascia doesn’t -- destroys muscle cells), skin rashes, etc. Exercise in Hot or Cold Environments Environments Critical Body Temperatures 39oC = Heat Exhaustion 43oC = Death Methods of Heat Transfer or Heat Loss Loss 1. Conduction -- Heat exchange accomplished Heat through contact between two substances of different temperatures. (i.e. Touching a hot item.) different 2. Convection -- Heat transference accomplished 2. by a moving fluid (air or water). (i.e. The body warms the adjacent air and water molecules which then rise and make room for others.) which Methods of Heat Transfer or Heat Loss Loss 3. Radiation -Heat transference accomplished by means of electromagnetic radiation. (i.e. The way the earth and things thereon are warmed by the sun.) 4. Evaporation -- Heat loss accomplished through the loss of energy needed to convert a liquid to a gas. (i.e. Why alcohol feels cold when rubbed on the body.) The primary method of heat loss during exercise is by evaporation. is Sweating is not always enough to maintain body temperature. (i.e. a high humidity lowers evaporation) evaporation) The most important consideration when exercising in the heat is to maintain body water balance. balance. Rectal Rectal Temperature oF 102.5 102 101.5 101 100.5 100 99.5 99 98.5 1 hr 2 hr 3 hr 4 hr No water Ad Libitum Regular Intake Work time Guidelines for Fluid Intake during Exercise in the Heat in 1. Increased sodium levels in the body cause an increased plasma 1. volume. volume. 2. Fluid replacement should equal at least one-half of fluid lost via 2. sweat. sweat. 3. Fluids should be palatable (taste good) to encourage more 3. consumption. consumption. 4. Fluid should be cool (15-22oC or 59-70oF) to encourage gastric F) emptying. emptying. 5. Fluids should only contain 4-8 g/L of glucose. a. more than 8g = slower gastric emptying b. fructose can cause stomach cramps, nausea, and/or diarrhea 6. Make sure you are completely hydrated 24 hrs before (clear 6. urine) the activity. urine) Guidelines for Fluid Intake during Exercise in the Heat Exercise 7. Specific Recommendations Activities lasting < 1 hr Cool plain H2O equal to at least one-half sweat rate is all that is equal needed. needed. Activities lasting 1-3 hrs 1. drink 300-500 ml 1-2 hrs pre-event 2. drink 100-200 ml every 15 minutes 3. athletes will benefit if each 100-200 ml contains 0.5-1.0 g 3. glucose. glucose. 4. athletes will benefit if each 100-200 ml contains 20-50 mg 4. sodium. sodium. Guidelines for Fluid Intake during Exercise in the Heat Exercise 7. Specific Recommendations (cont.) Activities lasting >3 hrs Same as 1-3 hrs except: 4. athletes will benefit if each 100-200 ml contains 4. 50-75 mg sodium. 50-75 Post Exercise 1. Plain water is not recommended unless taken 1. with a meal with 2. Fluids should contain 2-3 g/L of sodium to 2. encourage fluid retention. encourage Physiologic Responses to Exercise in the Heat the 1. Max VO2 usually not effected (too short an exercise period) 2. Submaximal heart rate increases PRIMARY REASON: a. Increased sweating ==> Vasodilation in Skin ==> Reduced blood to a. muscles ==> Need increased cardiac output ==> Increased heart rate muscles Secondary reasons (activity must be long duration 1+ hrs): a. Increased sweating ==> Decreased blood volume ==> decreased a. stroke volume ==> Increased heart rate stroke b. Increased core temperature ==> Heat inactivation of mitochondrial b. processes ==> Decreased a-v O2 difference ==> Increased heart rate processes Physiologic Responses to Exercise in the Heat the 3. Trained individuals respond better than 3. untrained untrained 4. Women in luteal phase are more susceptible 4. to heat injuries (Core temperature rises in the luteal phase.) luteal 5. The greater the thickness of the 5. subcutaneous fat layer (internal insulation) the greater the heat stress due to a greater heat storage. heat Exercise in the Heat is harder on Children than Adults than 1. More inefficient movement patterns = greater heat 1. production production 2. Children have increased heat gain (increased 2. heat loss in cold). Smaller size cooks quicker!! heat 3. Lower Cardiac Output (smaller Stroke Volume & 3. Blood Volume) = increased difficulty to get blood where its needed where 4. Smaller sweat glands = lower sweat output 5. Slower sweating response time = longer time to 5. sweating onset sweating 6. Slower sweat rate. Heat Acclimatization Heat 1. Decreased Heart Rate during sub-max work. 2. Slower response time for sending blood to the 2. skin. skin. 3. Decreased blood flow to the skin (in dry heat). 4. Increased blood volume. 5. Lower sodium concentration in sweat. 6. Increased sweat rate. 7. More rapid onset of sweating. 8. Increased evaporation. Preventing Heat Stress In addition to maintaining fluid balance, precooling the body prior to heat exposure will increase the body’s ability to withstand heat stress. Pre-cooling usually involves cold water (<60o F) immersion or cold showers for 10 minutes. Pre-cooling keeps heart rate lower and slows the increase of body temperature. Determining Exercise Heat Risk Determining Heat Risk is determined by Heat using a 3 thermometer device. This allows for the measurements of solar radiation (black globe), air temperature (dry bulb), and relative humidity (via wet bulb). wet The combination of the three The gives the wet bulb globe temperature or WBGT. temperature Determining Exercise Heat Risk Determining WBGT 50o 50 50o to 65o 50 65o to 73o 65 73o to 82o 73 WBGT INDEX Heat Risk low heat risk low but cold?? but low moderate high Determining Exercise Heat Risk Determining WBGT (oF) = (0.7 x wb) F) + (0.2 x g) + (0.1 x db) (0.2 Baton Rouge - 6:30 am (Aug) wb = 83o (RH = 90%) db = 86o g = 86o (sun not up yet) WBGT = 84o risk = Very HIGH Where Where wb = wet bulb temp wb g = black globe temp db = dry bulb temp Predisposing Factors leading to Dangerous Levels of Heat Stress Individual Physiological Limitations 1. Underlying Illness 2. Low Physical Fitness 3. Dehydration 4. Sleep Deprivation (especially <3 h in the last 24 h) 5. Overweight (BMI > 25 kg/m2) 6. Improper acclimatization Environmental Factors 1. Heavy Heat Load 2. High Solar Radiation Organizational Factors 1. Physical effort unmatched to physical fitness 2. Improper work/rest cycles 3. Improper rehydration regimen 4. Absence of proper treatment devices 5. Training in the Hottest hours (10:00-17:00) Hypothermia: The main risk from exercise in the cold. exercise Work Intensity helps determine the chance for Hypothermia for clo = the insulation quality of clothing (i.e. the amount of clothing required for warmth) Staying Dry is the most important consideration for preventing hypothermia preventing Heat loss is 25x faster in water than air!! ACCOMMODATION TO EXERCISE IN THE COLD 1. Increased submaximal VO2 (enhanced thermogenesis). 2. Decreased exercise capacity in water (fast heat loss). 3. Increased VE (increased catecholamine release). 4. Reduced skin blood flow (cold induced vasoconstriction). 5. Lower lipid use (reduced blood flow to adipose tissue). 6. Increased glycogen use (#5 and increased catecholamines). 7. Increased lactate concentrations (see #6). 8. Increased central blood volume (see #4). 9. Frozen tissues in body extremities a.k.a. frost bite (fingers, toes, nose, etc) (see #4, #8, and also greater convective heat loss). 10. Decreased muscle strength & endurance (decreased enzyme activity both myosin & metabolic). 11. Increased resting blood pressure (increased catecholamine release and vaso-constriction). 12. Increased diuresis (see #11) Cold Acclimatization Cold 1. Increased non-shivering thermogenesis A. Higher hormone response B. Increased metabolic pathway inefficiency C. Increased amount of brown fat (not completely proven) C. 2. Improved blood flow to extremities. 2. 3. Increase in subcutaneous fat (not completely proven) 3. (Note: These chronic changes involved different physiologic systems than heat acclimatization. Thus, you can acclimatize to heat and cold simultaneously!) ...
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This note was uploaded on 11/18/2009 for the course KIN 3515 taught by Professor Nelson during the Fall '09 term at LSU.

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