3339 Midterm 2

How does the muscle contract?

• Nerve signal: the signal reaches the neuromuscular junction, releasing Ach

• Calcium is released: signal travels along sarcolemma and t-tubules, causing Ca2+ to releases from the SR

• Calcium binds to troponin: tropomyosin moves, exposing the myosin-binding sites on actin

• ATP powers contraction: myosin interacts with actin, using energy from ATP hydrolysis to produce contraction

• Relaxation: ATP allows myosin to detach from actin, and ATP also powers Ca2+ reuptake so the muscle can relax

What is ATP and why is it so important?

• food (carbs, proteins, fats)—> metabolic reactions (release and transfer energy)—> ATP (immediately usable energy for cellular work)

What is free ATP and CP?

• O2 required: no

• Location: cytosol

• ATP Yield/ Glucose: immediate re-synthesis

• Activity duration supported: seconds—> sprints or heavy lifting

What is Anaerobic Glycolysis?

• O2 required: no

• Location: cytosol

• ATP Yield/ Glucose: 2-3 ATP

• Activity duration supported: up to 1-2 minutes

What is Aerobic Glycolysis/ Oxidization?

• O2 required: yes

• Location: mitochondria

• ATP Yield/ Glucose: 36-38 ATP

• Activity duration supported: extended sustained activity

What are the 5 Intramuscular energy stores?

• ATP

• CP

• Triglycerides

• Glycogen

• Carbon skeletons from amino acids

What happens to fuel use with higher intensities?

• CHO becomes more important

• oxygen becomes limiting so we’re relying on anaerobic glycogen which pushes glycogen more

• the amount of plasma glucose increases because of CHO demand

• shift to intramuscular fuel

When your body breaks down food, what are the 3 important molecules?

• ATP

• NADH

• FADH2

What are the estimated fuel stores for fat and glucose?

• fat fuel stores: 90,000kcal- 110,000 kcal

• glucose fuel stores: 2,00kcal

What is intramuscular triglycerides?

• fat stored inside muscle

What is TG in lipoprotein complexes?

• fat transported in the blood

What is free fatty acids?

• fatty acids released from adipose tissue

What is transamination?

• transferring an amino group from one molecule to another

What is anaplerosis?

• helping refill substances used in the TCA cycle so it can keep operating

What is the glucose- alanine cycle?

• helps move material from the muscle to liver and supports glucose production

Why does the shift from lipids to glucose happen?

• Reduced blood flow to adipose tissue 

• Leads to reduced availability of FFAs to muscle 

• Reductions in lipid transport (Into the muscle and mitochondria)

• Reductions in intramuscular TG hydrolysis 

What is the cori cycle/ fate of pyruvate?

• the fate of pyruvate determines how much energy your muscles produce.. your cells either choose slow or fast and make its routing choice based on oxygen

• during a light jog: oxygen goes into mitochondria and extra a lot of energy

• during a sprint: oxygen drops and the engine stalls causing a build up of pyruvate, as an emergency pressure valve, the cell converts pyruvate build up into lactate straight into the bloodstream whee it then gets carried to the liver to rebuilt fresh glucose

What are the endurance training effects on metabolism?

• reduction in RER

• reduced glycogenesis

• increased fat oxidization

Why does RER decrease?

• your body has two fuel tanks

  • when you become endurance trained, your RER decreases at the same absolute workload because they use more fat and less CHO to maintain same running speed

Why is there reduced glycogenolysis?

• with endurance training, your body becomes better at using fat, so it doesn’t need to breakdown as much stored glycogen at the same workload

Why is there increased fat oxidation?

• your body becomes better and breaking down fat and using it for energy

What are the resistance training effects on metabolism?

• increased muscle energy stores including ATP, creatine phosphate and glycogen

• muscle adapt to energy demands (MPS)

What is muscle protein synthesis and how does it differ for trained and untrained individuals?

• MPS is the process of building new muscle protein

• volume and intensity matters!!

• too little= no increase in MPS

• too much= reductions in MPS (depending on diet)

When does MPS peak for trained vs untrained individuals?

• Trained

  • peaks at 2-3 hours

  • quickly returns to baseline

• Untrained

  • peaks at 16 hours

  • slowly returns to baseline

Why is fluid so important during exercise?

• it helps maintain cognitive and physical performance

• it helps thermoregulation (body temp)

What happens when you sweat during exercise?

• losing water and salt which leads to reduced blood volume (loss of fluid overall) and reduced cooling ability (less blood circulation)

How much dehydration is too much?

• 1% body weight loss: negative impacts on performance

• 1.5-2% body weight loss: aim to stay below

• 2%+: noticeable symptoms of dehydration

What is mild vs severe dehydration?

• Mild Dehydration

  • loss of <5% body weight

  • thirst

  • rapid pulse

  • fainting

• Severe Dehydration

  • loss of >5% body weight

  • confusion

  • rapid, shallow breathing

  • coma; death

What are the hydration recommendations BEFORE exercise?

• arrive to your activity properly hydrated

• adults: 500-700mL, 60-90 minutes before

• serious athletes: 5-7mL/kg 4 hours before

• kids: 400mL; 60-90 minutes before

*If the serious athlete is still dehydrated (not producing urine or dark urine) then you add another 3-5mL/kg 2 hours before

What are the hydration recommendations DURING exercise?

• maintain hydration

• 150-350mL of fluid every 15-20 minutes (approximately a cup every 15 mins)

• others factors must be considered:

  • tolerve

  • temperature

  • exercise or physical activity workload

*for children, regular breaks every 15-20 minutes should be provided for fluid consumption, regardless of thirst

What are the hydration recommendation AFTER exercise?

• enough to replenish what you lost

• approximately 1-1.5L/kg body weight loss

• timing should be immediately and as tolerated

• rehydration rate of 130-150% of your body mass loss

What is important about the timing for rehydration ingestion?

• doing it in a spread out way (metered) is best

What are considerations about electrolytes?

• salt drives thirst

• Palatable

• May stimulate fluid retention

**combining glucose and sodium has increased fluid intake

What is hyponatremia?

• low sodium concentration in the blood and too much water consumption

• symptoms

  • fatigue

  • nausea

  • cramps

What is heat stroke?

• body temperature becomes dangerously high (40+)

• symptoms

  • seizures

  • vomiting

  • rapid pulse

  • rapid, shallow breathing

• hot weather= hot and dry skin

• strenuous activity= hot and moist skin

What should you do for a heat stroke?

• 1: Call 911

• 2. Move the person to cool area/ shade

• 3. remove excess clothing or equipment

• 4. begin cooling through cold compress (ex: neck)

What is rhabdomyolysis?

• breakdown of muscle tissue caused by overexertion and very intesne exercise

• symptoms

  • muscle swelling

  • muscle weakness

  • dark urine

• treatments

  • IV

  • dialysis

  • rest and recovery

What are the general recommendations for fuel- PRE ACTIVITY?

• main focus is on carbs and fluids

  • already broken down such as juices

• we tend to diminish fat and protein intake because they take longer to digest

What are the general recommendations for fuel- DURING ACTIVITY?

• When?

  • >60 mins

  • > 2-3 hours

  • 40-60 minutes but high intensity (75% of VO2 max)

• Amount?

  • CHO: 30-60g/ hour

• Why?

  • spares both liver and muscle glycogen and can be readily absorbed for muscles and brain

• *protein and fat aren’t typically required

What are the general recommendations for fuel- POST ACTIVITY?

• for recreational athletes a healthy diet is good enough

• for serious athletes

  • <8 hours between practice/ competition

  • 1-1.2g/kg CHO

  • 20-25g of protein

Why does protein and CHO have good recovery?

• best glucose storage overtime

• CHO + protein= less CHO to oxidize and more to store which allows for a faster recovery

• more isn’t better, 1.2g is peal

How much net ATP does glycolysis produce from blood glucose?

• 2 net ATP

How does net ATP does glycolysis produce from muscle glycogen?

• 3 ATP

What are the RQ values for fat, mixed fuels ad carbohydrates?

• 0.7—> fat

• 0.85—> mixed fat and CHO

• 1.0—> carbs

How long can muscle protein synthesis remain elevated after resistance exercise?

• approximately 24-48 hours

How much fluid should you drink before exercise- audlts?

• 500-700mL, 60-90 minutes before

How much fluid should you drink during exercise?

• 130-350mL evert 15-20 minutes

How much fluid should you replace after exercise per kg of body weight loss?

• 1-1.5L per kg lost