Midterm 2 nutrition

Signal Transmission overview (contraction)

• nerve impulse (AP) travels from motor neuron to NMJ

• At the NMH: ach is released into synaptic cleft

• Ach binds to receptors on the sarcolemma

• Na+ channels generate new AP in the muscle fiber

• AP runs along sarcolemma and into T tubules

T-tubules (muscle contraction)

The electrical signal in the t-tubules triggers the SR to release calcium into the sarcoplasm

Contraction (CA is released into sarcoplasm)

• Ca binds to troponin

• tropnin pulls tropomyosin away from myosin-binding sites 

• Myosin attaches and cross-bridges are formed

• ATP is hydrolysed into ADP and Pi

• the myosin head pivots, and actin is pulled inwards 

• Shortening=contraction

Detachement and reactivation

After first CB cycle, atp binds to new head

if ca is present cycle will continue

If CA is not available

• nerve signal ends

• Ach is broken down

• Co2+ is pumped back into SR

• muscle relaxes

Glycogen (net atp)

3 atp

Glucose net atp

2 net

PFK inhibited

• atp levels are increased

• glycolysis is inhibit 

PFK is activated

decreased levels of atp in body

• allows glycolysis

fate of pyruvate

becomes lactate or can entre the TCA

what keeps the tca going

oxaloacetate

lactate produced by glycolysis

trained people are good at clearing lactate

• can go to the cori cycle in the liver

anaplerosis

a metabolic process involving chemical reactions that synthesize intermediates for the Citric Acid Cycle (TCA cycle). (protein support)

Chemical energy is stored

in the bonds of nutrients (CHO, protein, fats)

chemical energy is released

released through

• metabolic pathways

• manageable energy bursts

extracted energy becomes

ATP

immediate enrgy

• Atp and creatine phosphate 

• creatine is 4-6x greater than atp

• lasts only for a few seconds

increased energy means increased use of

• intramuscular components

• increased carbohydrate use 

intramuscular energy

• muscular glycogen

• intramuscular triglycerides 

muscle glycogen

• stored CHO

• rapid ATP source 

• used locally in muscle

• important for high intensity, prolonged workout

intramuscular triglycerides

• stored fat in muscle fibers

• used for oxidative, anaerobic processes 

How is glucose stored and why

glucose is stored as part of a glycogen ball, so we can store more and decrease osmolarity issues.

glucose is a highly soluble molecule and increases osmotic pressure, meaning storing glucose chains would be inefficient 

what triggers glycogenphosphorylase 

glucagon

epinephrine

glucagon

• activates liver glycogenolysis

• triggered by low blood glucose 

epi and glycogenolysis

• activates glycogen phosphorylase in the in muscle and some liver

cleaving glycogenolysis (stored glycogen balls)

• glycogen phosphorylase removes glucose from glycogen branches at the end

• glycogen phos removes glucose and hexokinase turns in immeditaley into G-6-p

muscle and g6p

• g6p enters glycolysis to make ATP 

• it cannot leave as glucose 

• will be g6p forever 

liver and G6P

NADH (aerobic vs anaerobic conditions)

• can help with continuing glycolysis (anaerobic)

• can also (under aerobic conditions) can be transformed into ATP through the ETC

the ETC

• NADH/FADH (from gly/tca) passes through complexes

• energy is released, pumping H+ from mitochondrial matrix into the intermembrane space

• H+ accumulates in intermembrane space (creating conc/electrical gradient)

• H+ needs to flow back into matrix through ATP synthase which means ATP is created 

fuel from lipids is plentiful

• estimated 90 000-110 000 kcal

• compared to glucose at 2000 kcal (not enough for long period/high intensity)

Adreanline and fat

• stimulated during exercise

• triggers the mobilization of energy stores 

• lipolysis

lipolysos

releases free fatty acids and glycerol into the blood stream

lipid usage

• adrenaline activates hormone-sensitive lipase

• fatty acids are taken up by the muscle cell (mediated by lipoprotein lipase)

• fatty acids are transported into the mitochondria (limiting step, transport)

Hormone sensitive lipase

• breaks fown stored triglycerides into glycerol and 3 FFA

sources of lipids

• intramuscular TG

• TG in lipoprotein complexes

• FFA from adipose tissue 

Beta oxidation creates

• creates acetyl coa

• each cycle = 1 NADH and FADH (5 ATP)

• Acetyl CoA goes to crebs and produces more NADH/FADH 

Acetyl coa is formed by

cleaving of 2 C from FA

oxaloacetate must be available for

acetyl coa to enter the krebs cycle (limiting step)

Lipid - glucose shift

• reduced blood flow to adipose tissue (reducsed ffa to muscle)

• reductions in lipid transport

• reduction in intramuscular tg hydrolysis due to decrease in hormone sensitive lipase (due to energy shift)

Protein usage in energy

Protein contributes very little to energy

can play a role in breakdown and TCA

Transamination

anapleurosis

glucose-alanine cycle 

transamintaion

changing available amino acids into keto acids to make the AA we need

• some AA we can’t make

free AA pool

small and comes from liver and non-contractile muscles

training effects on metab — endurance

• reduction in rer

• reduction in glucogenolysis

• inc lactate clearance

• inc fat oxidation

reductions in rer

• downward shift at the same absolute workload

• RER shifts towards 0.7 (fat usage)

• Rer is the ratio  of vco2 and co2

why see reductions in glycogenolysis with metabolism training

increase in # of oxidative fibers

reductions in adrenaline spike

• decrease glycogenphosphorylase activity 

• increase fat burn 

inc lactate clearance

lactate can be filtered to supply muscles by making glu/gly

inc training inc lactate clearance

athlete paradox

• athletes often have increased levels of intramuscular fat because their body stores and uses it so efficiently 

resistance exercise- metabolic change

• inc glycogen stores

• anaerobic increases 

• increase in storage and maximized glycogen levels

• inc in muscle protein synthesis after exercise (depending on vol and freq)

Muscle protein synthesis 

dependent on vol/freq

• too little = no inc

• too much = reductions in MPS

MPS peak

trained

• 2-3 peak, quick revert to baseline

untrained

• peaks at 16 hours, and reverts back to baseline slowly 

two most important factors of optimizing nutrition for performance

• fluid and fuel

fluid factors

• #1 thermoregulation

• cognitive fx can decrease with 1% dehydration 

• water is the medium where everything takes place 

sweat rate

• cools us down

• highly individual 

• decrease water, blood vol, blood to skin and cooling

loosing high amounts of water and salt decreases

perfusion

how much we need to drink is determined by

sweat rate

determining sweat rate

• determined by change in body weight before and after an activity 

• ideally, no weight loss (ideally no more than 1.5-2% BW) loss

• need to be as close to nude weight as possible

arrive to activity

hydrated

before exercise adults drink

500-700ml (3 cups)

• 60-90 min before 

before exercise athletes drink

5-7 ml/kg 4 hr before

• if urine is dark/MIA need another drink of 3-5ml/kg 2 hr before 

• (won’t calcualte for the average adult or rec athlete)

children drink before exercise

• 400 ml of fluid the night before 

Drink regardless of thirst

• urine gets lighter with hydration

• thirst mechanism 2/3 of the way and then turns off

After exercise Hydration

• intake to replenish BW

• 1-1.2kg/bw loss

• hydration should be as early as tolerated

• should account for epoc

accounting for epoc in hydration

• increased sweat rate after exercise

• add 30-50% to calculated intake 

methods for rehyrdation

• bolus

• metered

Bolus

• replenish all at once

• drink it all in an hour

• most won’t tolerate

metered

• drink over 4-5 hours

• more effective than bolus

• more tolerated

Dehyrdation and env

• heat is bad

• cold env equipment can trap sweat and decrease cooling

hydration during activity

• drink enough to prevent body weight loss (150-350 ml/fluid every 15-20 min)

• consider tolerance, temp and workload 

training the gut

• gut will adapt

• gastric empting

• receptors in the gut can change

• during exercise BF is diverted, and stuff is not absorbed and digested as well but this can be trained.

heat stroke

• body temp = 40c or higher

heat stroke signs and symptoms

• altered mental state (confusion/agitation/seizures/irritable

• Alteration in sweating (hot weather, skin is hot and dry) (strenuous, skin is hot and moist)

• Nausea and vomiting

• flushing

• rapid and shallow breathing

• inc hr

• headache

if heatstroke what to do

call 911, cold compress, layers, shade

rhabdomyolysis

Condition where muscle breakdown leads to accumulation of CK and Heme in the muscle 

caused by overexertion and dehydration 

typically in inactive person

symptoms

• soreness, swelling, weakness

• dark urine  

• Kidney failure

why kidney failure and rhabdomyolysis

• dehyrdation means we are no longer producing urine, or producing a shit ton less 

• bad shit then accumulates in the liver. 

electrolytes

maintainable in a diet, but we can consider supplementing in ultra athltetes

• sweat rate and salt intake makes this highly variable

electrolytes depending on

• length of exercise

• temperature 

Hypotranemia

increased sweating but only replacing the sweat with water

too much water and too much sweat

Hypotranemia symptoms

• cramps, dizzy, weak, vomiting, fatigue, decreased appetite

fuel with serious athletes

heavy carb reliance (85%+)

Athletes need 5-7g/kg of carbs per day

1.2-2g protein

Muscle glycogen

• liver gets first dibs on gly/glu coming into the body, and then filters the rest out to muscles

• unless there is an emergency and very low levels in the muscle

fueling for exercise carbs and fluid

• consumed until exercise

• carbs should get more simple as game gets closer 

• dec volume and how complex they are

protein and fuel for exercise

until 30 min- 1hr before

fats fuel for exercise

1-2 hours before

gold standard fluid status

• isotope/total body water

• plasma osmolarity (blood test) (euhy level = 285 Mosm/kg)

Simple measurements for fluid status 

• urine (lags response to hypovolumia/euhydration)

• BW

• plasma conc of sodium

• BIA 

• Saliva

• Symptoms 

field test and fluid status

-whole body sweat test (loss of bw, account fluid in and out)

local sweat Na2 conc

Gatorade/sport beverages

• not designed for electrolytes

• meant to drive thirst and CHO intake

thirst mech and fatorate

• sometimes water only will turn off mechanism early, and when we start balancing water and salt after sweat. 

• Adding salt to our fluid will extend thirst mechanism

CES studies and intake

• Studies support that ces drives people to drink more/hydrate

• better net fluid balance

rehydration agents

• better in hydration terms 

• 1g salt lost/L sweat, CES = 400mg/L

• can use medical rehydrants 

Blood glucose supplied by

• liver glucose

• external sources

• gluconeogenesis

liver glycogen

• Liver glycogen gets way low overnight

• so need to replenish in the morning so the liver gets first dibs 

how to slow/stop Gluconeogenesis

need to supply enough CHO so protein isn’t broken down

muscle glycogen can take up to

18 hours to replenish

fueling during 45-60 min

• not required unless high intensity (75% vo2)

• wouldn’t be necessary for completion, just would increase performance

Activities 30-75 min (fuel during)

• could do a salivary rinse

• activates salivary amylase

Activities 1-2 hours, fuel during activity

• not required but will enhance performance 

• 30g of carb

activies 2-3 hours plus

• should fuel prob

• 60g