2013-06-21 / Columnists

Rockaway Walks Fitness Column

Bioenergetics: Exercise Intensity and Fuel Selection (Energy)
by Steven C. McCarthy IPO, HSW MS

Exercise and diet are essential part of achieving health related fitness. During rest our energy requirements are almost 100% of Aerobic (oxygen rich blood; oxidative phosphorylation) metabolism, blood lactate levels are low, and resting oxygen consumption is about .25L/min or 3.5ml/kg/min (metabolic equivalent =1 MET). Upon increase physical demand the body shift oxygen rich blood from organs to working muscles and utilization of oxygen by the muscles during exercise. The cardiorespiratory function is the ability of the heart, lungs, and circulatory system to supply oxygen and nutrients efficiently to meet the demand and recovery to maintain homeostasis or steady state (task specific). In addition the body has the ability to respond to fight or flight (emergencies) with stored fuel/energy. This source of energy is Anaerobic (without free oxygen). Short (5-10 seconds) high intense resistance/strength training up to 60 seconds improves metabolism Anaerobically. Just as intense endurance training (Interval, Long slow distance, high intensity) greater than 3 minutes improves your Aerobic metabolism. Best practices in exercise prescription for optimal strength or endurance gains require training on alternate days. Remember men and women respond similarly to training programs. Training is always greater in individuals with lower initial fitness (so let’s get started). Genetics plays an important role in how a person responds to training.


Contrasting recommendations for Health vs. Fitness vs. Performance are as follow: (1) Health (Lowers risk of health problems), moderate intensity (55-69% Maximum Heart Rate), and 5-7 days/week, and accumulate 30 min/day (30 minutes most days). (2) Fitness (Cardiovascular fitness), 70-80% maximum heart rate, at 3-5 days/week, 20-60 min/session (about 3 miles 3 times/week). Thirdly Performance (running performance), Greater than 70% maximum heart rate, at 7 plus times a week, greater than 60 min/session (about 50-90 miles per week). Review The WAVE article on Eating Healthy Foods: Exercise to Improve Flexibility, Strength & Endurance: Daily Estimate Energy Requirement (EER) or Health & Fitness Benefit to Cardio Endurance Training.


Five factors affecting your performance are Diet (carbohydrate and water), Central Nervous System (arousal and motivation), Strength/Skill (Practice, Natural endowment and Muscle-fiber type), Environment (Altitude, Heat, Humidity), and Energy Production.


 If you participate in low, moderate to vigorously intense exercise outlined in this article then you need to know about bioenergetics how foodstuffs in your diet of Fat, Protein and Carbohydrates are metabolized (processed) and converted into fuel/energy. Fat (Fatty acids stored as triglycerides) and Carbohydrates (glucose stored as glycogen) are primary fuel/energy source. We have three types of fuel selections that take place during exercise they are from Fat, Carbohydrates and the “Crossover” between both. Fat burns in the shadow of Carbohydrates (during prolong exercise there is a shift from Carbohydrates towards Fat metabolism). Fats are the primary fuel utilization during low exercise intensity at 30% oxygen uptake (or 56% Maximum Heart Rate). Carbohydrates are the primary fuel utilization during high exercise intensity 70% oxygen uptake (or 82% Maximum Heart Rate). The third selection process “Crossover” concept describes the shift from fat to Carbohydrate metabolism as exercise intensity increases due to recruitment of fast muscle fibers and increase blood levels of epinephrine. Simply if your goal is to loose weight then an exercise prescription design would include moderate intense activity (metabolic equivalent 3-6 MET’s or 40-60% oxygen uptake or 63-75% maximum heart Rate or RPE /Rate of Perceived Exertion 12-13) for a prolong period (30-60 minutes) to utilize Fat as fuel/energy. Protein is not an energy source during exercise (2%) and may contribute up to 15% during prolong periods.


The Energy/Fuel currency of the body is ATP (Adenosine Triphosphate). The body forms ATP during Anaerobic and Aerobic pathways. Anaerobic (process without oxygen (1) Phosphocreatine, found in vertebrate muscle, where it serves to store phosphate ester of creatine to provide energy for muscular contraction (movement). Also (2) Glycolysis provides anaerobic energy by the breakdown of glucose by enzymes, releasing energy and pyruvic acid.) With Aerobic sources (process with oxygen: Adenosine Triphosphate (ATP) Oxidative Phosphorylation (Krebs cycle and Electron transport chain), ATP is found in living tissue when the bond is broken forms Adenosine Diphosphate (ADP), ADP which provide energy for muscular contraction (flex). Energy production starts at the Mitochondria).


Starting with ultra short-term activities/ performances that last less than 10 seconds the primary energy source is anaerobic (Phosphocreatine). During short-term activities/performance that last 10 to 180 seconds start shifts from Anaerobic (70% at 10s) to Aerobic (60% at 180s) the primary energy source is Anaerobic shifting to Aerobic. Now during moderate-length activities/performance that last 3-20 minutes increase reliance is on aerobic energy production (3min at 60% ATP generated aerobically and 20 min at 90% ATP supplied aerobically) altitude and anemia my influence oxygen delivery. During intermediate activity/performance that last 21-60 minutes in this phase the energy source is predominantly aerobic usually conducted at less than 90% oxygen uptake, important environmental factors heat, humidity and state of hydration. For Long-term 1-4 hours performance environmental factors are important (ability to deal with heat and humidity), Muscle and liver glycogen (maintain rate of carbohydrate utilization; Crossover shifts carbohydrate to fat), and diet and fluid ingestion influence performance.


The more fit, the greater ability your body is able to re-synthesis ATP and higher oxygen uptake (VO2 max) ability to consume and process oxygen (ACSM guidelines 40/50-85% maximum oxygen uptake and 55/65%-90% maximum heart rate). After 4 weeks improvement will be seen in cellular activity. There should be more mitochondria for energy production provided for the electron transport chain. The ph levels would be more stable and not reach high lactic levels by becoming acidic. Therefore your have less muscle fatigue and you have more energy to stay physically active. Common mistakes in training are: Overtraining, undertraining, performing non specific exercises, failure to schedule a long-term training plan, and failure to taper before performance (short term reduction in training load prior to competition, and not allowing the muscles to resynthesize glycogen and heal from training-induced damage/ Delay Onset Muscle Soreness DOMS).


To learn more go to www.walkprograms.com on how you may become Ambassadors in Partnership with Healthy Lifestyle Changes, Inc. The 2013 7th annual Rockaway Walks fitness free exercise program begins June 29, threw August 31. Location Beach 19th street on the boardwalk at 8 am. Open to the public.


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