Module 1: General Nutrition Principles and Bioenergetics/Energy Systems During Exercise Flashcards
Why is energy important?
- The body needs a constant supply of energy to move and perform everyday tasks
- The more activity a person does, the more energy that is required
What two things impact how energy is provided?
Energy and intensity play an important role in the way energy (in the form of ATP) is provided. E.g. sitting versus running you are using different energy systems
What is ATP?
- Adenosine Triphosphate is the usable form of energy in the body
- The energy from foods that we eat has to ultimately be converted into ATP before the potential energy can be used
- An ATP molecule consists of adenosine and 3 phosphates
What occurs when ATP is broken down?
- Energy is released from ATP by breaking down the bonds that hold this compound together
- Enzymes are used to breakdown ATP
- ATPase is the enzyme used to break down ATP into ADP and a single phosphate
- This type of reaction is exothermic - generates energy
What is ATP Re-synthesis and where is ATP stored?
- Small amounts of ATP are stored with muscle fibres
- Stored ATP is used up very quickly (2-3 seconds) and therefore needs to be replenished immediately for movement to continue
- For ATP to be rebuilt an endothermic reaction has to occur. This is a chemical reaction which absorbs energy
- Re-synthesis of ATP is done through joining of ADP and single phosphate. This energy regeneration is only possible through one of three energy systems
- Nutrition provides the foundation for the sunstrates that generate energy in the body
What are the 3 energy systems that regenerate ATP?
- ATP-PC System - Also called Phosphagen System
- Glycolytic System - Also called Anaerobic Glycolysis
- Aerobic System
- The systems are not exclusive of each other
- All the systems are active and ready to engage at all times
- Dependent on intensity/type of activity
- Can train energy systems
What is the energy continuum of physical activity?
- The point at which an athlete moves from one energy system to another is known as a threshold. This depends on the exercise intensity and fuel available
When will the aerobic system be utilized?
- Activity that is performed at a low to moderate intensity over a sustained or prolonged period of time is supported by the Aerobic System
- ## The intensity of activity is moderate enough and performed over enough time to allow the more complex Aerobic System to generate sufficient ATP
Explain the ATP-PC System
- The body has very small, finite stores of ATP in muscle. There so we can move quickly
- Depleted ATP stores trigger the release of the enzyme, creatine kinase, which causes phosphocreatine (PC) that is stored in skeletal muscle to be broken down anaerobically
→PC is also known as Creatine Phosphate (CP)
→ PC acts as a substrate for the formation of ATP
What is PC produced by?
PC is produced by the body in the liver and kidneys from dietary creatine sourcess (meat, fish, poultry) and dietary souces of arginine, glycine, and methionine
How long does stored ATP last?
Stored ATP can provide the energy to support powerful muscle contractions but only 2-3 seconds
Explain the pathway of Cr in the body
(ATP-PC System)
- Non-phosphorylated creatine (Cr) is released from the liver into the blood stream and transported to muscle cells
- Once inside muscle cells, it is transformed into phosphocreatine by the enzyme complex creatine kinase
- PCr can anaerobically donate a phosphate group to ADP in muscle to form ATP and generate the energy needed to support movement
- System has received a lot of interest in terms of supplementation (i.e. Creatine)
When is ATP-PC System used
This rapid availability of PC is important for providing contractions of high power, such as in the 100m run OR a short burst of intense activity during a longer game. E.g. A fast break in basketball
Can PC be replenished?
- There is only enough PC to last for up to 10 seconds and it can only be replenished when the intensity of the activity is sub-maximal
What is the ATP-PC/Glycolytic Threshold?
- The point at which the ATP-PC energy system is exhausted and the glycolytic system takes over
- E.g. A soccer midfielder needs to make an abrupt, 3 second sprint to get free or beyond a defender (ATP-PC System) who, after passing the ball, has to run back to help defeng (Glycolytic System)
- These switches are noticeable for people
What are the advantages and disadvantaages of the ATP-PC System?
What are the claims about phosphocreatine?
“Improves muscle performance, promotes strength, recovery, and performance”
- Statements not evaluated by FDA
- Thought if you max out creatine in nutrition you will have more to rely on
- Research skewed towards young males
- Children/youth susceptible to claims like these. See others doing it and want to do it as well but not good evidence base for kids
How does PCr impact sport performance?
- Maximal body stores of creatine have been linked to enhanced exercise capacity
- Diet alone provides about 1-2g/day of creatine resulting in muscle creatine stores at 60-80% maximal saturation.
→ Supplementation to max out that extra 20% - A large body of evidence now indicates that creatine supplementation can produce full saturation of creatine stores which, in turn has been linked to increase acute exercise capacity
- Helps with short term, high intensity. E.g. lifting more because don’t tire as easility. Sprints, lifting
- Dependent on athlete
What is the theoretical basis behind creatine supplementation?
- Physiology: PCr stores limit maximal ATP production and performance during high intensity, short time activity (e.g. sprinting)
- Theory: Supplementation with PCr will increase cellular PCr levels and enhance exercise performance
What do we know based on the research of creatine supplementation?
- Hundreds of studies and review of PCr supplementation have been published
- The consensus finding is that creatine supplementation can increase muscle creatine content, improve exerise capacity, and sport performance
- Creatine monohydrate most studied
Other than sport performance, what can creatine supplementation help with?
- Creatine supplementation may also offer clinical therapeutic health benefits to individuals suffering from:
- Creatine deficiency syndromes
- Myocardial ischemia (Heart attack) and/or stroke
- Neurodegenerative diseases
What are the ergogenic effects of creatine supplementation?
- Increases in performance and strength in short-duration, maximal-intensity exercises. E.g. I-repetition maximum, muscular power, number of repetitions, muscular endurance, speed, and total force
- Increases in lean body mass (through recovery and repetition)
- May prevent loss of strength as a result of aerobic activity when combined with anaerobic activities in recreational activity
What individuals are less likely to derive benefit from creatine supplementation?
(Why are some people responders vs non-responders?)
- Individuals with higher baseline level of creatine before supplementing compared to those with low baseline levels
- Explains why some athletes appear to be responders to supplementation versus nonresponders
- Can be a game changer for people with low creatine
What is the creatine supplementation protocol?
- Helps to eat within physical activity to bring all nutrition stores up
- Better to take it after because you are setting yourself up for the next workout (replenish)
- Same ratio for males as well
What are the potential side effects of creatine supplementation?
- Muscle cramps
- Over-use injuries (recover faster so inclined to train more)
- Impaired hydration status and fluid retention
- Doping violations - off label additions of WADA banned substances may be within supplements
- Decreased focus on healthy eating and other critical aspects of HIIT performance
- Long term data not well known
- Consistency in training is key - regardless of supplementation
Explain the glycolytic system
- Once PC is depleted (at around 10 seconds) the Glycolytic system takes over and regenerates ATP from the breakdown of glucose
- The glycolytic system is also known as anareobic glycolysis
- Produces pyruvic acid which can form lactic acid
- The process of glucose breakdown in the absence of oxygen is called anaerobic glycolysis and causes the production of pyruvic acid
- The longer exercise continues the higher the rise in lactic acid and lower pH levels. Slowly inhibits enzyme activity causing fatigue and eventually Onset of Blood Lactate accumulation (OBLA)
- More lactic acid produced when high intensity and long duration. This inhibits glycolysis and causes fatigue (self-protective)
Why is the Cori Cycle necessary?
- During intense activity (approaching the Lactate or Anaerobic threshold), actate accumulates in working muscles. At the same time, the body cannot produce ATP quickly enough to meet its needs
- The body adopts an alternate metabolic route to get rid of the lactate, and keep producing energy anaerobically. This process is called the Cori Cycle
What is the Cori Cycle?
- A process for transporting lactate from cells that are undergoing anaerobic metabolism to the liver where it is used to provide glucose back to the cells
- The end product is glucose
- Lactate produced by the muscles is converted to glucose by the liver and ged back to working muscles to serve as a substrate for ATP synthesis
The ________ intensity of activity, the _________ relative accumulation of lactate
Higher; greater
What is OBLA?
- Onset of Blood Lactate Accumulation
- The exercise intensity at which the blood concentration of lactate begins to increase rapidly
Can you train your lactate threshold?
Yes in lactate threshold training athletes can clear lactate using the Cori Cycle more effectively than untrained individuals
What is the lactate threshold? Is it the same as OBLA?
- If lactate synthesis exceeds the body’s ability to clear lactate via the Cori Cycle, lactate and H+ ion accumulate in muscle causing fatigue and a reduction in performance
- The lactate threshold is the pount after which lactate synthesis > lactate clearance
- The lactate threshold is preceded by OBLA (2 different things)
At what point will people reach the lactate (anaerobic) threshold?
- Higher intensity will increase lactate accumulation, may reach threshold
- Dependent on people, can train to increase threshold
How long does the glycolytic system last and how can it be supported nutritionally?
- Glycolytic ATP re-synthesis will continue for up to 3 minutes but peaks at 1 minute. E.g. Goal off the bench in hockey
- The body must have adequate CHO available to support glycolysis - either as blood glucose or glycogen
- No CHO = No Fuel Generation via Glycolysis (Atkins won’t work for athletes - fat burns in the flame of carbohydrate)
- Key system for high intensity, intermediate time activity
What is the glycolytic/aerobic threshold?
- The point at which the intensity of activity begins to decline (but not stop) and plateau and the rapid energy production of the glycolytic system is no longer needed
- Sufficient oxygen will be available throughout to allow for ATP resynthesis
What are the advantages and disadvantages of the glycolytic system?
How can training help with glycolytic energy production?
- Hydrogen ions produced reduce muscle pH
- Improving the buffering capacity of the muscle to better handle the changes in pH helps promote anaerobic energy production
- High-intensity interval training increases muscle buffering capacity and high-intensity exercise performance
How can nutrition help impact muscle pH?
- Bicarbonate loading can improve performance during exhaustive exercise lasting between 1-7 minutes. GI distress has limited the use of bicarbonate, but repeated doses over several days prior to competition may reduce the problems
- Beta-alanine can improve muscle buffering capacity and high-intensity exercise performance
- Creatine not only provides substrates to ATP-PCr system but improves buffering capacity
What does improved performance via nutrition to buffer hydrogen ions indicate?
Increasing buffering capacity demonstrates that the acidosis associated with high glycolytic rates is an important factor in fatigue
What is bicarbonate loading?
Use it as an ergogenic aid. Orally loading with bicarbonate (baking soda) has been proposed as a way to limit the fatigue generated by production of lactic acid and H+ ions in muscle during high intensity activity fueld by glycolysis
What is the theoretical basis for bicarbonate loading?
- Orally loading with bicarbonate will, in turn, temporarily increase blood bicarbonate to acutely enhance extra-cellular buffering of the efflux of H+ ions coming from contracting muscle
- Though to reduce the fatigue and exercise capacity drop off associated with intense activity where there is production of large amounts of H+ ions via anaerobic glycolysis
What does research show about bicarbonate loading?
- Bicarbonate loading is associated with enhanced performance (~2% gain) during short-term, high-intensity sprints lasting ~60s in duration, with a reduced efficacy as the effor duration exceeds 10 minutes
→ Drop off in benefits seen as early as 4 minutes - The duration and intensity of exercise have a critical impact on the performance gains driven by supplementation with NaHCO3
What is sodium bicarb loading protocol?
- Single acute NaHCO3 dose of 0.2-0.4g/kg consumed 60-150 minutes prior to exercise
- Split doses (E.g. several smaller doses giving the same total intake) taken over a time period of 30-180 min prior to exercise
- Serial loading with 3-4 smaller doses per day for 2-4 consecutive days prior to an event
What are the potential side effects of bicarb loading?
- Profound GI distress (nausea, explosive diarrhea, pain) are commonly associated with use of the supplement
What strategies can be used to minimize side effects of bicarb loading?
- Co-ingestion of NaHCO3 with a small, CHO rich meal (~1.5g/kg BM CHO)
- Use of sodium citrate as an alternatve to NaHCO3
- Split dose or stacking strategies to dosing
- Given the very high potential for GI distress, thorough investigation into the best individualized strategy is recommended prior to use in a competition setting
If an athlete comes to you and is interesting in ergogenic aids what should you do?
- Start with low hanging fruit like sleep, eating well consistently, and spending that money on coaching
- Can then go with competition eating and finally ergogenic aids
Explain the aerobic system
- The aerobic system of energy production needs oxygen to function
- Sufficient oxygen availability to support aerobic metabolism occurs when the intensity of activity is low-moderate. The duration of activity may be very long
- The complete oxidation of glucose can produce up to 38 molecules of ATP and has 3 distinct stages
- This system provides maximal energy return BUT the conditions of activity (moderate intensity/long duration) must be present for this system to perform
What are the 3 stages of the aerobic system?
- Glycolysis
- Krebs/Citric Acid Cycle
- Electron Transport Chain
Explain the first step of the aerobic system
- Glycolysis
- This process is the same as anaerobic glycolysis but occurs in the presence of oxygen. Lactic acid is not produced and the pyruvic acid is converted into a compound called acetyl coA
- Acetyl CoA moves to the mitochondria within the muscle cell where the remaining stages of aerobic metabolism are activated
Explain the second stage of the aerobic system
- Krebs/CAC cycle
- Once the pyruvic acid diffuses into the matrix of the mitochondria a complex cycle of reactions occurs in a process known as the Krebs cycle
- The reactions produce two molecules of ATP and carbon dioxide
- Hydrogen is taken to the electron transport chain
Expain the third stage of the aerobic system
- Electron Transport Chain
- Hydrogen is carried to the ETC by hydrogen carriers
- This occurs in the cristae of the mitochondria. The hydrogen splits into hydrogen ions and electrons and these are charged with potential energy
- The hydrogen ions are oxidized to form water, while providing energy to resynthesize ATP. Throughout this process, 34 ATP molecules are formed
How does training impact the body?
(Think energy systems)
- Training enhances the body’s ability to utilize the available energy systems
- What is moderate intensity for a trained athlete may be extremely intense for an active individual or impossible to manage for someone who is sedentary
Can fats be used in the aerobic system?
- Fats can also be used as an energy source in the aerobic system
- The krebs cycle and the ETC can metabolize fat as well as CHO to produce ATP
What produces more energy: fat or glycogen? When is this source utilized?
- More ATP can be made from one molecule of fatty acids than from one molecule of glycogen but the intensity MUST be low
- This is why in long duration exercise, fatty acids will be the predominant energy source
When is the aerobic system utilized?
After 10 seconds start to use more of aerobic system and goes for long duration
What are the advantages and disadvantages of the aerobic system?
What is glycogenesis?
Process of converting excess glucose into glycogen
Where is glycogen stored?
- Can be stored in the liver and in the muscle in limited capacit
- Muscle glycogen (~460-520g) only used by the muscle for energy
- Liver glycogen (~80g) can leave the liver as BG to be used by the brain and other tissues
- Glycogen = back up fuel tank
Where is fat stored and what form can it be in?
- Fat can be stored in several locations throughout the body including subcutaneous adipose, visceral adipose, and muscle
- Intramuscular Triglycerides (IMTG) are a source of fuel for muscles to generate ATP, primarily during endurance exercise
→~200g (1800kcal) stored in the muscle - The breakdown of IMTG provides free fatty acids for aerobic metabolism
How does exercise training effect glycogen storage?
- An adaptation that occurs with exercise training, particularly endurance exercise training, is an improved capacity to store glycogen
What is carbohydrate loading?
- An ergogenic approach used by Sport Dietitians to take advantage of the phenomena that you can enhance ability to store glycogen
- To fully take advantage of this adaptation, athletes must consume adequate CHO
Define “hitting the wall” and the symptoms associated
- If adequate CHO to fuel either anaerobic or aerobic metabolism is not available, the athete can experience the phenomenon known as “Hitting the Wall” or “Bonking”
- Situation where the body can no longer generate sufficient ATP owing to a lack of glucose
→ Glycogen and blood glucose - Characterized by glucose depletion (blood levels and glycogen) which in turn produces severe hypoglycemia
- Ends activity until the athlete can replete their energy stores
- Symptoms include: severe fatigue, dizziness, light-headedness, tunnel-vision, disorientation, anxiety, nervousness, irritability, hostility, seizures, coma
What substrate is limiting in aerobic metabolism?
- CHO is the limiting substrate in aerobic metabolism
- fat burns in the flame of CHO
- You cannot complete the beta oxidation of fats and the full aerobic system without first completing glycolysis
- Enough fat is stored in the body, even in a lean individual, to provide energy. But ATP production from fat alone is too slow to sustain performance
How can hitting the wall be prevented?
Training diet and pre-event eating strategies are designed to prevent
What is EPOC?
- Excess Post Exercise Oxygen consumption
- Following intense physical activity, the body continues to consume high levels of oxygen and reflect heightened levels of metabolism even though the activity has ceised
- Reflects the work of the body to repair and repenish itself and return to its pre-exercise state
- EPOC helps the body to recover
What is EPOC also called?
Afterburn/oxygen debt
What are the effects of EPOC?
After intense activity, EPOC support the following functions:
- Production of ATP to replace the ATP used during the workout
- Re-synthesis of muscle glycogen from lactate via the Cori Cycle
- Restoration of oxygen levels in venous blood, skeletal muscle blood and myoglobin
- Repair of muscle tissue damaged during the workout
- Restoration of body temperature elevations to normal/resting levels
- Increased metabolic rate and an elevation of resting energy expenditure
What 5 factors effect the magnitude and duration of the EPOC?
- Exercise Intensity
- Duration of Exercise
- Training Status
- Gender
- Intermittent vs. Single bouts of exercise
How does exercise intensity influence EPOC?
- High intensity = higher EPOC
- The intensity of exercise appears to be the most significant factor in boosting post-exercise metabolism
- Activity at levels approaching the athlete’s Anaerobic threshold
How does duration of exercise influence EPOC?
- Given sufficient aerobic exercise intensity, exercise duration is an important factor influencing EPOC
How does training status influence EPOC?
The magnitude of EPOC in trained individuals may be smaller than in un-trained individuals. Several studies have reported a more rapid fall in EPOC and a shorter duration of EPOC in trained subjects
- Choose lower intensity and duration if untrained
How does gender influence EPOC?
- Research shows that energy expenditure with women at rest and during exercise varies with the menstrual phase
- Typically, resting EE is lowest one week before ovulation and highest during the 14 day luteal phase following ovulation, thus accordingly affecting EPOC
- Few controlled studies have been conducted to compare EPOC in men and women. Therefore, the gender effect on EPOC is not fully understood
How does intermittent vs. Single bouts of exercise effect EPOC?
Several studies have concluded that intermittet aerobic exercise bouts elicit a greater EPOC response when compared to continuous exercise bouts
What is considered the most effective way to stimulate the EPOC effect?
High intensity interval training (HIIT)
What adaptations occur during HIIT?
- ATP is produced by the anaerobic pathways during HITT. Once that ATP is exhausted, the ATP must be replenished for the athlete to continue
- During the rest interval of a HIIT workout, the body reverts to aerobic metabolism and tries to replace its ATP losses
- This works to some degree - enough to complete the next interbal - but the body will remain (overall) in a state of oxygen debt or deficit
What is oxygen deficit? How does it effect EPOC?
- The oxygen deficit is the difference between the volume of oxygen consumed during exercise and the amount that would be consumed if energy demands were met through only the aerobic energy pathway
- The larger the oxygen deficit the greater the EPOC and its effects
What are the recommendations for CHO loading?
- No benefit to sprinter not using that energy system
- Enhance endurance for athletes in sports putting them at risk of glycogen depletion (Longer than 2 hours)
- Carbohydrate rich diet for other people
- Do it in days right before they compete, and slow training so glycogen stores can fill and max out
