Sport Nutrition first half Flashcards
Energy use in 100m vs 800m vs marathon
PCR and ATP - Substrate level phosphorylation in 100m - glycogen store manipulation doesn’t benefit.
Glycolytic in 800m (although always cross over) - little aerobic - turned into lactate
Oxidative phosphorylation in marathon - most from carbs (85% of VO2 max for 2 hrs)
Describe Anabolism, unique for nutritionist
Anabolism
Building block precursors into synthesised end products
Uses ATP into ADP + Pi
Nutritionist not just what synthesised but also what is used (ATP) e.g. in muscle contraction
Describe Catabolism
Catabolism
Carbs, lipids, amino acids (also nutriets from diet) + O2
Into H20 and CO2
Produces ATP
Describe link between anabolism and catabolism
If someone wants to continue work (Muscular work = anabolism from contraction) they need catabolism - ATP resynthesis.
What % of energy comes from protein?
5
Describe the 3 roles of a sport nutritionalist
Educator
Translator
Bouncer
Size of stores of energy
Protein 14kg Fat 10.5 Carbs muscl glycogen 0.4 (up to 1kg) Liver 0.1kg Blood glucose (0.01)
Describe the 3 way interaction in energy balance. Increase in intake/ stores effect?
Energy intake
Energy stores
Energy expenditure
3 way interaction - increase or decrease in one impacts the other factors
Increase intake = increase stores. Increase energy intake= increase in metabolism (dietary induced thermogenesis) and can increase exercise and other components of energy expenditure. E.g. Studies show no breakfast = less PA in morning. Gives flexibility, not all excess will be adipose. Adipose tissues releases leptin which changes appetite and potentially intake Stores also affect energy expenditure e.g. High glycogen stores and running further.
Give some factors that effect energy intake
Loads of factors that affect intake- broadly envionment and lifestyle influencing cognition, reward, choice, mood, stress. Individual genetics and early life also affect at all stages.
Total energy intake
Composition of diet
Satiety issues
Amount & type of fibre
Type of foods (energy density)
Environmental/ sociological reasons e.g. Fitting in with a mate in the bar
Also normally finish a ‘mars bar’ regardless of size so mars determines intake.
Current weight and body comp
Hormonal control of appetite, fat deposition
Intake then influences energy expenditure metabolically LOOK: (nutrient sensing, muscle, liver, fat, gut) and impacts our future actions about energy intake and expenditure.
Factors that affect energy expenditure
Similar factors affect energy expenditure
Resting metabolic rate
Activities of daily living
Planned PA
Intensity of PA
Body comp
Total energy intake and composition of kcals
Genetics & inefficient energy cycles
Intake then influences energy expenditure metabolically LOOK: (nutrient sens
Difference in calculating BMR and RMR
BMR vs RMR. Rarely BMR. BMR - after sleep without walking (12 hrs). BMR = 4 hrs after,
How do TEE, DIT and RMR vary between sedentary adn very active (as a %)
Active person - rest day - proportion of RMR varies however RMR stays the same.
DIT is typically 10% of intake regardless of intake. TEE gives a challenge to expenditure which fluctuates on daily basis.
How much does RMR vary?
RMR easily predicted by height, age and body comp. (differences only 10s of calories).
calories in alcohol
7kcal/g
how to convert from kcal to KJ
x4.2
Explain how DIT varies with nutrition
Protein 25-30% is used to process protein
Carbs 6-8%
Fat 2-3%
Why is a calorie not a calorie?
DIT varies with nutritional
Protein 25-30% is used to process protein
Carbs 6-8%
Fat 2-3%
High protein diet but same calories (less calories)
Due to gluconeogenesis energy (de aminate and then convert to useful carb
Some pass straight to TCA
Straight to Acetyl CoA
Ketosis - some converted to ketones (ketogenic diet)
Interconversion processes cost energy
Contrasts to glucose - glucose ready to use
Fat some processes - e.g. B oxidation.
Relationship between effective calories and carb intake
As carbs decreases (replaced with fat and protein)
As carb decreases, effective calories decreases
Theoretical plan not real life.
Change in expenditure resultantly
x
What is energy balance?
Energy balance = dietry intake - total energy expenditure.
EB amount of dietary energy added or lost from energy stores after all the body's physiological systems have done all their work for the entire dat EB is an output from the body's physiological systems Negative = weight loss e.g. negative 2000
What is energy availability? Significance?
EA = Dietary intake - Exercise energy expenditure
Amount of dietary energy remaining after exercise training for all other metabolic functions
e.g. cellular maintenance and repair, thermoregulation, immunity, growth, reproduction
EA is an imput to the body’s physiological systems
Low energy availability should be avoided because it can impair performance and adaptation to training and may be harmful to brain, reproduction, metabolic and immune function and to bone health.
Relationship between EB and low EA?
Total energy expenditure is decreasing due to decreased metabolism - physiological systems are being suppressed e.g. Downregulate protein turnover, bone turnover, reproductive system
Low EA then dampening of physiological systems so becomes higher EB (still negative)
Why do both EA and EB need to be considered?
EA causes effects on physiological systems
Under voluntary control
EB is an effect of physiological systems, not under voluntary control, Does not indicate energy requirements for Health. EA is likely to put someone above or below EB. Both need to be considered.
Describe risks of energy deficiency in sport (women)
Causes
Women more at risk than men
Reason often unrelated to sport
Female athlete triad
Harmful effects on reproductive and skeletal health of physically active women
Often compulsive eating disorders (or exercise)
Intentional efforts to improve performance by reducing body weight and body fat
Also inadvertant
describe inadvertent failure to match EI with TEE
Exericse doesn’t affect acute Ad-libitum energy intake
Supresses relative energy intake
Via known neuroendocrine mechanisms
Describe appetite stimulant word and hormones
Orexigenic hormones: Ghrelin (appetite stimulant)
Describe appetite suppressant hormones
Anorexigenic hormones: PYY, GLP-1, PP, Leptin
effect of endurance/ Wingate test on appetite hormones and EI? Significance?
12 healthy males
3 trials - 60m rest, 60m endurance, 30min rest +5x 30s Wingate tests over 30min
Standard breakfast
Ad-libitum lunch, dinner and evening meals
Appetite hormones - ghrelin and PYY measured
All had similar total kJ (despite higher EE)
Acetylated ghrelin (hunger hormone) - same in rested Exercise decreases gherelin, decrease flow to GI tract so reduces secretion. Opposite increase in PYY (hunger suppressing) Decreased appetite in exercise over no exercise. However no difference in total intake affect - not convinced of appetite hormone intake. Increase during exercise though - inadvertent chronic deficiency. Some compensation occurs otherwise ppl would waste away but not sure of degree.
Effect of high carb diet on ad-libitum energy intake? Limtations to study?
Energy Intake higher in moderate than in higher carb intake (may have been related to types of foods) High carb (lower density) may be a factor. Possibly higher availability in higher carb.
Absolute intake of carb was similar despite a lower %.
Shows manipulation of diet may not yield desired effect.
Due to greater bulk and fibre content?
some compensated others are non-compensators
Compensators became progressively hungrier
How does nutrition in and around exercise influence energy intake?
Nutrition in and around exercise sessions influences subsequent energy intake.
20g protein post exercise decreases subsequent energy intake vs 20g carohydrate (isocaloric).
Guidelines for coaches/ dietitians/ nutritionists for EA and sport governing bodies
Coaches/ dietitians/ nutritionists Monitor and manage EA For carb loading/ growth: EA >45kcal/kg FFM For maintenance EA = 45kcal/lg FFM For fat loss EA = 30 -45 Never <30 - negative metabolic effects Sports governing bodies Establish rules and procedures to prevent excessively low EA
Normal EB at EA 45kcal/kgFFM/day, same at low EA?
0, can be 0 at low EA also
ACSMs 3 distinct origins of energy deficiency in athletes
Obsessive eating disorders (clinical mental illness)
Intentional and rational but mismanaged efforts to reduce body size and fatness for athletic comps
May include disordered eating habits such as fasting, diet pills, laxatives, diuretics, enemas, vomiting (often part of sport culture)
Inadvertant failure to increase energy intake with expenditure
WHy do athletes try to lose weight?
Females may also under-eat for reasons not related to sport - twice as many young women as men at every decile of body mass index percieve themselves to be overweight.
More lean women than lean men actively trying to lose weight.
More athletes report improvement in appearance over performance as a reason for losing weight.
relationship between EA and repro and bone protein synth and insulin
Low BMD may be mediated by oestrogen deficiency.
Lower EA also measns lower bone protein synth and lower insulin (aa uptake) in a linear way.
Declines abruptly <30EA
Disruption of repro function <30kcal.kg.FFM = EA Regardles of oestrogen after 5 days deficiency LH surge based on EA not intake or expenditure alone EA=30 may be sig as it approximately = sleeping MR Low EA also suppressed type 1 immunity (intracellular pathogens e.g. virus) - more common UTRI
Why do male and female athletes load glycogen differently?
Female athletes may not be able to increase glycogen stores as much as males - may be due to lower total eergy intake. Women can load glycogen like men when they eat just as much per kilo of body weight.
Implications of low EA in athletes?
Athletes should eat by discipline - specific amounts at planned times
Reconsider high % of carbs in endurance events
Bodies should make standards/ guidence for sport specific healthy weight management
What is the second law of thermodynamics? Why is a calorie not a calorie
dissipation law - in any irreversible (real) process, the entropy must increase; balance is not expected. Entropy is in fact identifiable with irreversibility. Change in energy+entropy = Gibbs free energy (predicts direction).
Second law says that no machine is completely efficient Lost as heat or internal rearrangement of chemical compounds and other changes in entropy Efficiency dependent on how it works, nature of fuel and processes enlisted by organism Second law says there is variation of efficiency for different metabolic pathways is to be expected.
Low carb or low fat for weight loss?
One study shows low carb can have 300cals more and still lead to larger weight loss
One mechanism
Gluconeogenesis for glucose to CNS and increased protein turnover could account for missing energy
Ends of a fatty acid
Methly end (n-) and carboxyl end
what do(18:1n-9) and (18:2n-6) mean?
Monosaturated (1 C=C) e.g. Oleic acid (18:1n-9) 18C atoms, bond is 9 away from methyl end
Polyunsaturated e.g. Linoleic acid (essential FA) (18:2n-6) first bond occurs 6 from (omega 6)
why are n-3 and n-6 so important?
Humans lack ability to insert C=Cbeyond C9 so have requirement for n-3 or n-6 Fas (omega 3 and omega 6)
why is there Sport nutrition interest in fat?
Major contributor to energy production during light and moderate intensity exercise
Very large energy stores
Spare finite source of carbs
Should athletes be consuming high fat diet/ fat loading?
(try to increase fat burning efficiency)
How do sources of energy differ with total energy cost?
Blood glucose from liver glycogen
Generally as exercise intensity increases Fat utilisation decreases.
Also as time increases proportion of fat for energy use increases as stores become depleted.
More and more from muscl glycogen and blood glucose
How do sources of energy differ with time?
Also as time increases proportion of fat for energy use increases as stores become depleted.
How does endurance training affect fat utilisation?
Increased fat oxidation during exercise will spare muscle glycogen
How is fat used by the body?
Break down TGs by HSL (hormone sesntive lipases)
Mobalise
In blood by albumin, free or lipoproteins
Into cells
Activated via fatty acyl-CoA
CPT1 (carnatine shuttle ) into mitochondrial
Studies look at carnatine supplement (only good with high carb)
CPT2 - fatty acycl coA
B oxidation
Krebs
Role of insulin in fat utilisation?
x Glucose - increases insulin
Inhibits activity of HSL (Hormone sensitive lipase)
Reduces breakdown of fats both IM and in adipose
Insulin changes fat/ carb utilisation in carbs
Short term carb loading or fat loading better for performance? why?
carb better due to more glycogen.
Also linked to perceived exertion - more tired with fat
Effectiveness in longer fat loading? why?
Increased fat oxidation at submax, decreased carb oxidation
Overall no difference in time trial performance
If totaly carb deplete may improve performance
what is dietary periodisation and rationale behind it?
Diet based on training/ comp.
Do positives (glycogen sparing) and negatives (lowered CHO stores) cancel each other out? If adaptation to fat (increased oxidation) are couple with short term high carb can you get benefits of both?
describe a dietary periodisation regime and does it lead to perf benefit? detriment?
5 high fat then high carb for 6 or high carb for all 6 followed by performance diet. - 120min test on day 7
Increased fat oxidation - seems to remain, not sure what aspect though? E.g. increased FFA release or increased oxidation etc? However no sig difference in time trial performance
High fat may impair training prior - also less fit pops may percieve exercise to be harder
How does fat diet affect VO2max?
INcreases as needs more O2 per energy created (less eficient)
Cases where high fat diet may be useful?
May benefit some ultra endurance athletes (very small groups)
High fat diets are particularly detrimental to what type of exercise and why?
Training combined with a high fat diet reduces high intensity performance, likely due to changes in PDH (pyruvate dehydrogenase complex activity
(linking carb metab to citric acid cycle - rate limiting step- so fat drives instead)
Why should you start carb refeeding as soon as possible? (physiology too)
Maximise time for glycogen synth, enhanced glycogen resynth (increased insulin sensitivity and glcogen synthase activation due to depleted stores)
Large meals vs small snacks for CHO synthesis?
24hr doesnt matter. < 8h then frequent snacks
Solid or carb CHO for glycogen resynth?
Similar
GI of foods for recovery meals? why?
High GI then large glycaemic and insulinaemic response (other mechanism too)
May be malabsorbed carb in low GI foogs
2 stores of CHO in muscle
Proglucogen
Macroglycogen
Extremes of spectrum
How is CHO storage affected by increased carbs in a 24 hr period?
Positive relatonship until threshold around 7-10g.kg-1 BM in 24hrs
May need more if strenuous or eccentric as assumes passive recovery
How does eccentric exercise affect glycogen resyth?
. eccentric ecercise which can impair post-exercise glycogen resynthesis - can be partially overcome by increased CHO.
How much carb in 0-4hrs to maximise resynth?
Early carb intake of 1.2g.kg.hr in 0-4hrs - less impact over longer period
Highest storage in 1st hr
How does gender affect glycogen resynth?
Most studies on males
Menstual status may affect, greater storage in luteal than follicular
Less response in general to carb loading than males?
Effect of TEI and other nutrients on glycogen resynth? other positives?
Underpinned by total energy intake Coingestion carbs with: Protein Increase glycogen storage? - only if not optimum carb timing (>1hr) or amount Limited to 1st hr of protein intake Increases during first 40mins and 2hs compared with just carbs alone of same conc - good if short recovery periods? Cant say for sure any benefit if optimum carb Good for N balance, repair etc anyway Alcohol Impairs recovery short termx
Levels of carb for low, mod and extreme exercise
Guidelines Immediate 0-4hr 1.2kgh Daily recovery for low intensity 5-7gkgday Mod to heavy = 7-12 Extreme (4-6hr per day) = 10-12gkgday
Why is g.kg better than %?
Often athletes find hard to achieve such carb rich diets in training
Normally 50-55% not 60-70%
Not just body mass but also muscle mass should be accounted for
Energy ratio terminology should be discouraged
Is correlation between % and g.kg though but not strong in men
No relationship in females due to restricted intake in some groups
(maybe because higher %carb = less fat so less overall cals)
When may more frequent snacks be better than meals of CHO?
Early frequent carbs to avoid discomfort often associated with eating large amounts of bulky high-carbohydrate foods, but may also provide direct benefits to glycogen storage during the early recovery phase. No important if >8 hrs.
Do high carb diets really enhance training adaptations over mod carb diets?
Not clear longitudinal evidence showing increased perf from high carb in trianing outcomes
Can reduce ‘over-reaching’ syndrome (performance detriment from overtraining)
May be underpowered studies
What do a sport nutritionalist need to do
Know sport** Know culture of sport - know how to communicate e.g. Practices in history, most work accross several sports How? Watch competition and training Communicate** MDT - particularly club environment Others may have better time/ opportunity to communicate Bigger buy in if an individual Younger players follow senior players Measure dietary intake Determine energy requirements Make dietary recommendations
How to measure energy intake and strengths and limitations
1) Food frequency questionnaire
a. Lacks precision
b. Recall bias
c. Very quick and easy
d. Population level technique
2) 24hr recall
Snapshat - not normal
Quick and easy - 5 to 10 minuntes
Combined with training can get good info
3) Recorded intake (weighed, estimated, standard household measures) - most common
3-7 days typically
Recording may change behaviour (prospective)
Less likely to forget/ selectively forget
Precise
Time consuming
3 day period better with coaching on that it’s acurate
x
Problems with measuring energy intake
Energy intake is underreported
Through choice not to record
Change diet due to monitoring
Chose items not problematic to record e.g. Get readymeal
Recall
Choose not to eat items that are problematic to record
What is PAL
PAL = Physical activity level = number based on activity though the day, multiple of RMR
Sedentary = 1.4 x RMR
Argument that most athletes are sedentary
Could assume sedentary and then add on extra for exercise.
How many kcal from running/ walking?
Running easy approx 1kcal per kg per km (walking or runnning)
How to calculate TEE
Calculate weekly training, divide bye 7, add daily average to RMR xPAL
How to assess for sweat losses?
Change in body mass during exercise, corrected for volume of drink/weight of food ingested and urine/faecal losses during exercise
Sodium loss can be estimated from the volume of sweat lost and the sweat sodium concentration
How to convert mmol to g
Times relative molecular mass = mg, /1000 = g
Name the 8 essential amino acids
Isoleucine Leucine Lysine Methionine Phenylalanine Tryptophan Valine
Name the 8 oxidised amino acids
Leucine Isoleucine Valine Lysine Glutamate Aspartate Alanine Asparagine
Describe inputs to the free amino acid pool
Dietary protein into gut
Digestion - taken up across gut (high %)
Into free amino acid pool
Also from dispensable amino acid synthesis (carbon from CHO or fat and N from NH3)
Infusion of aa IV (often tracers with labeled C and or N)
Exchange with tissue protein (degradation and uptake)
Describe outputs of the free amino acid pool
Urine -N
Sweat - n
CO2 (oxidation) - c
Tissue protein - C&
Describe how the relationship between muscle mass and age in a sedentary individual
In sedentary muscle mass remains unchanged (declines above 55)
Clinical significance of sarcopenia?
Clin sig - trips and falls
Lower metabolically active tissue
Lower vol/ mass to hold/ use glucose - diabetes risk
Sendentary requirements of protein
Approx 0.8g/kg/day
How can we measure protein turnover in individuals?
Nitrogen balance techniques
Tracers techniques
Where it’s going
Gut muscle etc
Resistance exercise (usually unilateral and lower body) Manipulate post-exercise protein nutrition Infusion of trace amounts of labelled aas in combination with blood tests and muscle sampling to determine protein synth (how much is uptaken into muscle) Done in both control and experimental groups Labell infused aas - muscle biopsy at different periods look at how much is uptake
Describe fluctuations in protein balance
Larger fluctuations in synthesis Smaller flucturations in breakdown BAsed on protein intake which decreases MPB and increases synthesis Overall net = 0 normally Normally balance with breakdown.
How does exercise affect protein balance?
Superimpose exercise
Increase in muscle protein synthesis
Drives positive increase
Smaller dips below breakdown (periods of negative NPB) and larger peaks with protein
Relationship between resistance exercise, NPB, synthesis and breakdown. Changed by feeding?
Without feeding
Breakdown>synthesis
Both breakdown and synthesis increase with exercise
Increase in synthesis is larger than increase in breakdown after exercise
Causes less negative effect on protein balance
Net balance become less negative
Balance is still negative without protein intake
Remains 48hrs in untrained individuals
How long do the effects of resistance training on NPB last in non-trained individuals?
48hr
Amount of post exercise protein to maximise muscle protein synthesis
increased effect on NPB up to 20gs of protein unilater leg curl
Another: Did whole body exercise- one cannular in each arm - one for blood and one for protein trace
Uncomfort in test
Whole body exercisee- larger amount needed to maximise?
No effect of body size
What you’ve done not weight that determines weight
40g why protein increased MPS to a greater extent than 20g
Is 20g protein appropriate for athletes?
Depends on body weight/ size
In this study 80-85kg males
Amount of muscle mass activated
Are there any sex differences in NPS?
No sig difference using 25gs post work out (lower body resistance)
Milk vs soy vs casein as a post exercise protein intake? underlying mechanism?
Whey>soy>casein
Milk >soy
Leucine key to switching on pathway
Higher concs in whey then soy then casein
Whey highest protein response then soy then casein
post exercise only - after 120 mins leucine concs were the same
Whey given slowly (pulse) to mimic response of casein
Bolus = greater protein synthesis (fast delivery) Both had equal amounts of Leucine and essential aa delivery but bulus was ealier.
Is milk really superior to soy?
Maybe milk is maximised but soy protein just needs more?(non max plant based protein at 20-25gs)
Consume additional plant protein you can get same effects.
Milk vs whey?
80% of milk is casein so how does this make sense?
Milk protein similar effects to whey
Effect of co-ingestion of carb and mps?
High carb increases insulin response
No difference in muscle protein synthesis
Carb seems to have no effect post workout
At both 0.15 and 0.6g CHO/kg.h
Though that the increase form aas triggers a maximal response of insulin
Benefit of protein intake during exercise and pre exercise?
Pre exercise?
One study shows positive, most show none
During exercise?
Might “prime the pump”
May enhance MPS during resistance exercise and early recovery
Effect of timing of protein intake post workout?
1hr vs 3hrs - same response
(in this study used protein with carb)
No anabolic window.
“window of opportunity” may be better phrase as eating straight away means they can wait 3hr to resensitise and potentially gain an extra meal.
3hr resensitise period between meals.
No much benefit if each then have meal 1 hr later.
Optimum distribution of protein intake
40g every 6hr 20 every 3hr 10g every 1.5hr 20g of protein every 3 hours (intermediate) was the best vs bolus and pulse Maximised MPS
When may a 40g protein bolus be appropriate
40g casein increase protein balance overnight, increased MPS
Over a long 12 week period, how did Milk/soy/carb post exercise vary in untrained individuals? How was this different in females?
All groups gained weight - milk then soy then carb
Milk group lost fat mass
Fat and bone free mass, much more in milk
Same study in females - chronic effects Just with milk or carb Greater gains in lean mass with milk vs carb However large loss in body fat post resistance exercise , more than boys Roughly same weight overall Female gained strength (males didnt really)
Measures to maximise NPB
Exercise is vital Consume high quality protein (milk) Consume at least 20-25g every 3h >0.3g/kg Consume 40g protein before bed (casein) 0.5g/kg
Describe the structure of an amino acid
Amine group
Carboxyl group
H bond
R group (side chain) - 20 different
Limitation of nitrogen balance?
Normally calculated on nitrogen balance which is limited - requirements that are too low come from this technique.
Calculated from implausibly high retentions of nitrogen at high protein intakes
Physiology of how aa ingestion promotes MPS. Difference in endurance and resistance
Exercise and aa ingestion promotes increases in MPS
Due to :
Gene transcription
Protein signalling
Translation initaltion
Very complex
Resistance - postivie protein balance = increased muscle protein accretion and hypertrophy
Endurance - maybe mitochondrial protein synthesis? (oxidative capacity)
Protein triggers both
Effect of endurance exercise on leucine oxidation
Increased = more requirement assumed
How to tell benefit of protein from endurance athletes
Difficult. Mixed MPS (Myofibrillar protein fraction and mito protein synthesis together) may not capture the feeding induced enhancement
Could pre exercise feeding hamper recovery?
Pre exercise feedining unlikely to increase MPS, also unlikely to hamper benefit
Describe the protein digestibility corrected amino acid score (PDCAAS)
Protein digestibility corrected amino acid score (PDCAAS)
High quality PDCAAS = 1 or close
Animal protein is most high quality
Soy also 1
Milk proteins have scores of 1.2 but are truncated at 1
Milk protein superior possibly due to richness in lecine
Why in leucine good?
Activate cell singalling in the protein kinase B-mammalian target of rapamycin (mTOR) pathway responsible for translation initiation.
Role of non-leucine aas
“leucine trigger” hypothesis
To sustain after initial leucine mediated activation need other EAA in particular the BCAAs
Effects of high carb diets with low fat? - comp of weight loss
Many conventional diets are high carb (50-55%) with 15% protein and <30% fat, - reductions in dietary fat and increases in dietary fibre being favoured. (reduced energy density) - low satiety and poor adherence over long periods
Comp of weight loss here 70-80% adipose, 20-30% lean tissue
Better ways than high carb diets and why?
Reducing intake of dietary carbs is critically important in promoting greater weight loss and greater loss of body fat
Possibly due to
Lower daily blood glucose and insulin
Inhibits lipolysis, storage not release
Another strategy is to lower the GI carb sources not quantities
Difficult for endurance athletes - need full recovery of glycogen stores
A higher protein or fat intake can also compromise performance
Optimal way for athletes?
What to replace carb with? (lower carb = <40%)
Higher protein better (still moderate protein diets - twice RDA- 20-30% intake) for preventing lean small loss
Resistive exercise also limits lean mass loss (synergistic)
Protein appears to have a greater satiety effect than carbs and fat.
Higher thermic effect.
Does insulin enhance/ suppres mPS/ MPB?
None found it enhanced MPS or MPB
Physiological requirements for althetes recovering from exercise
Hydration
Restoration of metabolised carb
Restoration/ repair of damaged proteins
Remodelling proteins
RDA guidelone enough for what? how may more benefit
Athletes may require protein for more than just alleviation of the risk for deficiency, inherent in the dietary guidelines, but also to aid in an elevated level of functioning and possibly adaptation to the exercise stimulus.
Van Loon, number to maximise protein synth and how often?
1.3-1.8 g · kg(-1) · day(-1) consumed as 3-4 isonitrogenous meals will maximize muscle protein synthesis
experienced athletes would require less, while more protein should be consumed during periods of high frequency/intensity training.
Van Loon, protein during caloric deficit
Elevated protein consumption, as high as 1.8-2.0 g · kg(-1) · day(-1) depending on the caloric deficit, may be advantageous in preventing lean mass losses during periods of energy restriction to promote fat loss
How is protein used by the body? Significance?
Increase hypertrophy/ muscle mass
Mainly for resistance athletes
In fact amount laid down in muscle is relatively little compared to excess
How much protein to water % in muscle?
20-25% of muscle is protein (chicken breast)
3kg = 240g ish (10g a day is previous study - where men gained 4kg lean mass with milk)
Energy
BCAAs oxidised increases during exercise (even at 30% VO2 max) from Wolfe
Not much at rest
<5% of energy use - relatively small
Can be up to 15% in some situations with severe carb depletion
Mitochondrial biogenesis
Therefore athletes have increased requirements
Benefits of protein during exercise?
No difference, no significant effect of performance
How does post exercise protein (instead of some carb) influence glycogen resynthesis? threshold value?
Increasing CHO ingestion increases glycogen resynthesis (until 1.4g/hg/h)
At lower CHO, additional protein improves resynthesis (increases calories)
May around 1.4g/kg/h - 1.0
If you eat low carbs, consuming some protein can increase glycogen
Protein effective <0.8/kg/h more commonly
Practicle significant of substituting carb for protein in endurance athlete
Carbs alone may be difficult to achieve, adding protein may be more useful
More achievable and realistic - people don’t just eat carbs
Other benefits of protein and carb mix after exercise?
One carb and one carb+milk protein with same weight
Less urine produced with milk protein
Additional milk protein to enhance rehydration
Also adaptation benefits
Describe how with training protein synthesis responses become exercise specific
Untrained - increases in both Myofribillar FSR and Mitochondrial with resistance. Increases in mito with edurance - become specific when trained (10 weeks).
Higher turnover in resistance exercise in MSFR, no diff to mitochondrial.
How can carb/protein intake post exercise effect adaptation to endurance exercise?
16 men and 16 women Carb protein (CM) Carbohydrate (C) Placebo Untrained Drinks immediately and 1h after each training session Increased VO2 max, relative and absolute (larger in relative) with CM, carb was same as placebo Carb protein enhances adaptation Adaptation better for training Perf for competition
How does alcohol effect MPS? way to limit?
Alcohol and MPS
Intermittent running (like team sport)
Followed by 12 shots of vodka in 3hrs
Decreases muscle protien synthesis
Sig difference between CHO and PRO when combined with alcohol.
If drinking then ensure adequate protein intake (25g in this study)
Describe athletic protein requirements
thletic protein requirements Sedentary = 0.8g/kg Endurance athletes = 1.2-1.6g/kg Strength athletes = 1.2-1.7g/kg 3000 kcal/day (12-15% protein) 90-113g/day (1.3-1.6g/kg for a 70kg athlete) When they consume is important Distribution over the day is important Increasing requirement during energy restriction 2g/kg Reduces lean tissue loss
Normal relationship between kcal intake and protein intake.
Normally linear relationship between kcal and protein
Whey supplements may disrupt this
How can carb type affect glycogen synthesis and why?
igh GI for high insulin over first 6 hrs, benefits may not be there >=20hrs
Combined glucose and fructose (lowerGI) may ooptimise resynth of muscl and liver glucogen - preferential hepatic synthesis of glycogen from fructose and also as different absorption from intestine.
How may low GI foods be beneficial?
Lower GI may improve capacty for continual exercise later on
Due to
Increased oxidation of lipid during exercise following feeding
Reduces reliance on carbs
Explains why no benefit in HIIT (reliance on carbs)
Could gastric emptying limit glycogen storage rate?
Gastric emptying rrate is unlikely to limit rate
Advantage of liquid protein over solid?
Liquid supplements can however simulataneous contribute to rehydration
Osmolarity may effect - high molecular weight glucose polymers may be better
How does beggining level of glycogen affect glycogen storage
Begging level of glycogen (capacity for glycogen availability) mediates glycogen storage - although less pronounced with higher carb.
Which aas are dependent for glycaemic/ insulinaemic response. - how does this effect glucose/insulin concs
Certain aas increase
Synergistic with carbs
Dependent on leucine, phenylalanine and tyrosine
Hydrolysed protein with certain EAAs increases insulin the most - e.g. hydrolysed whey, with glucose
Co ingestion is an effective means of increasing plasma insulin concs during a 3-hr post exercise recovery period
Protein should be in excess of 0.3g/kg/h
Co ingestion measns smaller glucose conc but higher insulin conc (makes sense as less carb and more insulin both which lower glucose - increasing uptake from insulin)
How much protein minimum for insulinaemic properties
Protein should be in excess of 0.3g/kg/h
Is glycogen synthesis all about insulin?
Increased FFAs (from muscle glycogen depletion) stimulates hepatic glucose production (gluconeogensis) and insulin (from carbs) doesn’t stop this.
Howeverm increased insulin can increase muscle glycogen resynth following exercise
Greater rate found with protein as well as carb alone (may be due to increased energy)
Summary of carb/ protein recommendation for glycogen resynthesis from Betts and Williams
> 1 of CHO
Or smaller carb with >0.3 again recommended (if below 0.8)
Other benefits of post exercise protein from Betts and Williams
Increased hepatic glucose with protein may be significant factor as well as increased glycogen resynth in general.
Also may have protective effect agains exercise-induced muscle damage e.g. reduces conc of myoglobin and activity of CK and LD but controvocy - individual variability e.g. CK
May restore contractile functioning.
During exercise:
Increases performance independent of insulin levels still - muscle glycogen spared with CHOPro mixture?
Increased central drive for exercise?
Anaplerotic replenishment of TCA intermediates
Can postone fatigue during exhaustive exercise and improve ‘late-exercise time-trial performance’
Other studies show no increase in time to fatigue/ performance time to complete etc
May be due to if carb fraction is lower than maximal levels for oxidative requirements
Increase glycogen storage may not be the cause of increased performance
During recovery
Improved fatigue time due to prolonged maintainence of euglycaemia from increased oxidation of extramuscular carb sources during exercise (exogenous and hepatically derived) Explains why carbpro may be better during latter stages of prolonged exercise or when pro is added to moderate quantities of carbs (when carb availablity is compromised) Fluctuating glucose availability is recognised by CNS and leads to fatigue
How many g of CHO stored where?
Liver - 80-100g (not trainable)
Muscle glycogen - larger and sensitive to training with glycogen synthase 2-300g to 800-1kg
How does liver output, muscle glycogen utilisation, plasma FFA and other fat sources (IMTG) use relate to intensity. What is rate limiting?
Liver output of glucose increases proportional to intensity
Muscle glycogen ultilasation increases with intensity
Plasma FFA stays the same
Other fat sources vary with intensity
Always lots of fat (even if very lean)
Reduction in IMTGs at high exercise intensities
Glycogen stores are rate limiting in endurance
How quickly is glycogen depleted?
Depletion causes fatigue
31% VO2max - still lots at 180
64% habitual - still normally 30%
84% VO2 max - availibily becomes limiting in 60mins (half marathon)
If 120% then matter of minutes
Higher intensity then quicker the decline
how can CHO feeding during a race aid maximal distance and 40km time trial performance?
3hr cycle
Glucose decreases - hypo at 3 hrs, carb oxidation rates decreases and so does muscle glycogen
90g carb given an hour
Glycogen muscle still falls
Rate of breakdown is still in excess of what can be digested and absorbed -
However athlete can still perform for 1 hr extra
40km time trial performance - (60minish)
Loss of 1 min *sig difference
Still useful
Max rate of exogenous carb absorption and ultisation?
max rate of 1-1.5g per minute
Describe the liver sparing actions of glucose
Always providing blood glucose 10-15umol/kg/min
Lo-glu drink - less from liver
High- glu (22% (very conc)) - none from liver
Describe exogenous glucose limiting factor and clin sig
Not much benefit in amunt oxidised by increasing glucose intake
More in stomach (difference between ingested and emptied
Vomiting potential
Bigger difference between emptied and oxidised
More in lower intestine - limiting factor = absorption?
GI stress , vomiting or defecation
Not muscle glucose uptake - IV this isn't an issue
How can we measure ultilisation of exogenous carb?
Can calculate how much ingested carb is used Labell drinks with carbon13 Ingestion occurs Followed by exercise Digestion absorption oxidation Collect breath samples Analysis of 13CO2/12CO2 ratio Isotope ratio mass spectromer
Relationship between exogenous oxidation rate and carb ingestion
Always oxidise less than amount ingested
Linear relationshop between amount of carb ingested and used around 1g/min
Limiting rate of oxidiaion around 1g/min
Glucose and fructose transporters in the intestine
SGLT1 - in intestine (glucose and galactose with Na)
Overwhelmed with increased glucose
Fructose via facilitated GLUT5
Use if glucose overwhelmed to increase blood sugar further
2 separate pathways
combination of glu, malt, suc and for for biggest benefit?
Sucrose as good as fructose (unless high)
MD as good as glucose
Glu+suc+fruc and glu+fruc can produce highest oxidation rates
Performance benefit of glucose and glucose +sucrose
Glucose over placebo extra 10%
Glucose and fructose extra 8% over glucose
Power
Why might findings of a performance benefit not be entirely accurate?
Know its water vs drink
Another study - told it was a performance drink - same as water and found similar results - 6% CHO was still 11% diff on TT cycling perf
Food vs drink carb ingetion?
Felt more full with bar
Only slight reduction in exogenous CHO oxidation
Only slight reduction in exercise
Convinience of sports drink
Other additive supplements to take during exercise for performance benefits
4 trials
Water
Placebo
Glucose
Glucose plus caddeine
105min stead state at 62% VO2 max/ 190W and 45min time trial
Double blind
Caffeine no effect on substrate metab with ingested CHO
4.6% better than GLU and 9% better than placebo
Potential mechanism for caffeine performance benefits?
Caffeine is lypolytic if fasted - may stay off carb Glycogen - limits lypolysis via insulin Same relative metab effect Power output increased Not via metabolic patterns
CHO recommendation in sport
1.0-1.2 g/min (60-70 g/hour) during exercise
Times to restore CHO
General
2-4h prior - restore liver after night
1h prior
Post exercise recovery
How much muscle TAG?
Muscle TAG = 0.3kg
How is pre muscle glycogen content related to exercise capacity
Intermittent bike performance
Pre muscle glycogen content linearly related to exercise capacity
High CHO prior to exercise = higher capacityand higher pre exercise glycogen, more than controls with mixed diet and low CHO diet.
Low vs high CHO replacement of glycogen training 2hrs a day
High CHO replaces glycogen in 24h window from 2h exercising, low CHO does not, increasingly declines
What is glycogen sypercompensation
One leg cycling
Lots of carb
Depleted leg- supercompensation increased muscle glycogen above resting levels showing some trainability
How recent carb intake to maximise muscle glycogen?
Eating high carb 1+2 days prior after 3 days of low carb just as good as eating higher carb after mod carb for same time period
Effect on time to exhaustion at 100% VO2 max high carb
3 days on high or low CHO
Higher exercise time with high carb diet
High CHO team sport?
Football - high vs low for 3 days prior to a match
1.8km difference, intensity less too
General guidlines for carb intake
Low intensity = 3-5g/kg/day
Mod = 1 a day = 5-7
High = 1-3hr MVPA= 6-10
Very high = 4-6 = 8-12
Do high high CHO diet improve general sport performance?
Varying duration and CHO intake per day
May be maximal is already me
Can pre exercise CHO be effective?
1-4hr before comp - 1-4g/kg/hr
Ambiguity
Only diff 0g vs 312g, not between 46 v 156g
Resp exchange ratio (closer to 1 = carb)
More carb in 312
Pre vs during feeding of CHO?
2 x 30km meals During and pre similar M = before C = during During may have more effect if Longer Opposite blood glucose levels.
Risks of hypo from pre exercise feeding
Ingestion of glucose decreases blood glucose after CHO initially
Due to insulin and muscles
CHO better than placebo during exericse?
No difference between CHO and gloopy drink as a pre exercise drink
Both better than water
Affect pacing strategy etc
Why are muscle more receptive to glycogen 0-10hr after exercise?
increased GLUT 4
Training with low glycogen vs high glycogen
Muscle glycogen and time to exhaustion improved from low training
Low trained resulted in greater increase in citrate synthase (CS)
Trend for increased haloacid-dehalogenase (HAD) activity
Both key in oxidative metabolism
Training with low muscle glycogen reduced self-selected training intensity
Potential limitations of training low glycogen
educed self-regulated training vol
Increased risk of injury when depleted
Increased risk of illness - URTI
From Burke how to optimise performance benefit from carbs on given carb amount
High molecular weight glucose polymers However reduces nutrient density Co- ingestion of large amounts of caffeine Sleep disturbance Creatine loading Weight gain Add protein
Describe the term “carb availibility” and why it is better than % carbs
Adequate supply for muscle and CNS (high avail)
Limiting the daily exercise programme (low availability)
Amount needed depends on
Exercise/ energy cost
Muscle mass
Accounts for energy restricted diets, low intensity activities, large size
Is a depletion phase necessary to maximise glycogen storage in trained individuals?
Nope not in trained just 24-36hr high carb intake and rest
Optimum carb load schedule for ultra endurance event
10-12g.kg/24hr for 36-48h
What is meant be general fuelling up?
What is meant by “general fueling up”
Prep for events <90 min with 7-12g
Describe pre-event fuelling
Before exericse >60min 1-4g.kg 1-4hrs before exercise
Avoid high fat/ protein/ fibre to avoid GI ISSUES
Low GI may provide more sustained if cannot consume during
Pre exercise Low may be better as attenuated hyperglycaemia and insulin which reduces suppression of FFA oxidation. Also leads to better maintenance of plasma glucose
Must studies fail to find performance benefit
In exercise feeding negates this so may only be beneficial if unable to feed
Descibe speedy refuelling
<8hrs then 1-1.2g//kg/hr
Benefits of small nacks
Describe intra-exercise carb requirements during different exercise scenarios
<45min none 45-75min Small amounts e.g. mouth rinse No benefit with IV though Both sweet and nonsweet carbs 1.0-2.5hr 30-60g.h Ultra-endurance exercise >2.5-3h up to 90g.hr If combined with fructose Above problems of GI comfort, opportunity to consume 2:1 ratio of glucose:fructose
Burke, how is female glycogen storage different from males?
Small diff with menstrual cycle, females can store glycogen as well as males
Difference in training with low glycogen between trained and untrained
In untrained training with low glycogen can improve exercise capacity. Unclear in well trained
Not clamped training procedure (same every day)
Many ways/ characteristics of application and study
No evidence to relate to sporting performance
Different methods of training low
High fat -May reduce the chronic adaptations to training and impair carb utilization and ability to sustain high intensity exercise
Can use training to endure low carb, work after overnight fast, consuming water during prolonged workout, withholding carb after workout and restricting carb below fuel requirements of training load.
Describe variation in body water content
Variation between individuals both absolute and relative
Related to differences in body composition
Mainly a function of adipose tissue content
From CT and dispersed in adipose
Larger adipose mass, reduced % of water
40% in adipose
70% in well trained adult
Proportionally most abundant molecule = water
How can water content be measured
Dilution technique
Take sample e.g. urine, saliva, blood
Idea of background tracer levels
Given heavy water- deuterium oxide
Next day take sample again (urine take second sample)
Greater the change in deutrium concentration between samples means lower the body water
From change in comp can calculate body water composition as rest has diffused across the body
How can water turnover be measured? why is this faster in athletes?
On serial days can work out rate at which they are turning over water normally 2L per day but higher in adults Faster in athletes Sweating Other routes More intake
Describe the distribution of water in the body
70kg at 60% water = 42L (average) In the ICF and ECF 2/3 = ICF 1/3 =ECF 1/4 is Intravascular IVF (1/12 total) 3/4 is intersistial ISF
Describe the components of water balance
Fluid intake 1.6l Fluid intake food 1L Metabolic water 400ml Losses Insensible Skin loss Sweat loss? Expired air Sensible Urine (most) Faecal loss Sweat loss? (recognise or not) Exercise increases loses in expired air May limit fluid and food May increase metabolic water Normally Increases and decreases in exercise balance each other Urine is how we regulate
Describe euhydration, hyperhydration and hypohydration. Differ from dehydration and rehydration?
Euhydration - state of water balance Wave - never completely stable Plasm osmolality 280-290mosmol/kg (/l) Urine osmolality <700mosmol/kg Urine specific gravity <1.020 Hyperhydration - loads of water Dehydration not at below just is process of losing water Hypohydration (loss of 1% of body weight) - physiological state Back up = rehydation
Describe the regulation of plasma osmolality
Regulated via exretion by kidneys and intake via thirst mechanism
Control centres in hypothalamus/forebrain
Osmorecetops - 2-3% change in plasma osmolaltiy
= change in response e.g. kindey
Baroreceptors - 10% change in blood volume/pressure
Renal excretion - can only reduce losses, cannot correct deficit
Thirst - most intake is habitual rather than due to physiological needs
Hyperhydration
Decreased plasma osmolality Osmoreceptors Decreased thirst Decreased AVP/ ADH Decreased intake and increased excretion Increase in osmolality
Hypohydration
Increased plasma osmolality Sensed by osmorecptors Increase thirst Increase Argenine Vasopressin hormone (ADH) Less urinary exretion Water retained Decreased plasm osmolality
Composition of ECF and ICF
ICF ECF Sodium 12 140 Potassium 150 4 Calcium 4 2 Magnegium 3 1 Chloride 4 104 Bicarb 12 29 Inorganic phosphate 40 1 Total mosmol 285 285
Describe water balance during exercise
.5-2.5% mass loss
Bigg diff in fluid intake and sweat loss
Independent - sweat more doesn’t mean drink more
Describe maximising post exercise rehydration theory
What they drink affects AVP and rehydration
Most water will come back out
Effect of the post exercise drink on AVP affects retention
More AVP/ADH then the more retention
Euhydrated = low AVP
Increases with exercise x2-4
Drink/ rehydration = drop in AVP (as drop in osmolality)
If decline in AVP with intake is less then decrease urine output and increase drink retention
Desribe the process of rehydration
Mouth - (drink ingestion) Important for chosing how to drink Taste affects how much you have too Choice of flavour Temperature also affects Stomach Regulates gastric emptying How quickly uptaken into circiculation Key for water (unlike carbs) Small intestine Intestinal absorption Circulation Retention - stays or in bladder?
Urine conc for hypohydration
Below 700mosmol/kg urine hypohydrated definitely
Below 900 = hypohydrated according to Lewis
Describe the effect of rate of drinking on hydration status
Insufficient previous rehydration?
Euhydrated group- increased more than they lost
Hypo- consumed 2/3 of what they lost
Describe vol of fluid to rehydrate and Na effect
Without sodium
100% -of loss - still neg FB
Doesn’t even acount for losses after exercise
150% needed to rehydrate
(no advantage of 200)
High NA - increases NFB at all 3 levels and retention of a more positve NFB (less gradual decline)
Relationship between NA conc mmol/l and urine production
150% rehydration vol with 0,25,50,100mmol/l Na
Lowest urine production with 100mmol/l, dose response
How does carb content affect hydration status?
With 2 vs 10% glucose - takes longer through stomach - drip feeding and takes longer. Sig benefit to NFB
Milk protein more rehydration
Same reason
No improvement with whey protein (fast protein)
4 overall factors that affect hydration status
Drink palatability, volume, composition and rate of drinking
Describe differences in those that start eu/hypo hydrated?
Insufficient previous rehydration?
Euhydrated group- increased more than they lost
Hypo- consumed 2/3 of what they lost
Consensus on the effect of dehydration on aerobic exercise
Dehydration (incorrect term) >2% BW degrades aerobic exercise performance in temperate-warm-hot environments. Greater levels of dehydration will further degrade aerobic exercise performance
Most finish >2% dehydrate Not so much rugby Sport dependent
Describe different causes of dehydration
Types of dehydration
Pre existing hypohydration
Generally caused by inadequate rehydration from previous exercise
Many start (1/3)
Exercise induced hypohydration
Loss of sweat > intake
More prevalent in prolonged exercise >1h
Hot/ humid conditions, limited convective cooling
Limited drinking oppertunities e.g. Half time in football, less oportunities to rehydrate
Describe sports where risks of dehydration are higher
Fluid intake - swimming (open water), often only one drinks stop, must stop swimming to drink but much lower sweat rate.
Runners typically dehydrate themselves running
Convective cooling outside for cyclists increases cooling so lower sweat response
2% reduction in body weight from 24hrs of no fluid.
Often in athletes that have to make weight
Many US colleigic athletes, majority Hypo (cut off at 900)
S hYp definitely hypo - 12%
Cyclists have 2 bottle cages - runners less opportunity to rehydrate
Slower runners tend to carry fluid - completly changes biomechanics
Fluid intake - swimming (open water), often only one drinks stop, must stop swimming to drink but much lower sweat rate.’
How does hydration stutus affect 5km endurance performance and edurance capacity?
5km treadmill running performance
Hypohydrated by fluid restriction and exercise
2% hypohydrated = 6% greater time
Change in performance of 1% = a meaningful change
Range of 2-11% change
Unsure why
Some people more susceptible than others
Endurance capacity
Run to exhaustion at 70% VO2max
Fluid ingested or restricted (cross over trial so got both)
25% reduction if no fluid
How does temperature and hydration status combined affect performance. Why?
4 groups of 10,20,30,40 deg C Manipulated hydration status in evening Started 0 or 4% dehydrated Hydration status affected performance Also interaction with environmental Hotter it was, greater decrease Shown by % decrement from EU Only stat sig in 30C, anomaly at 20 20deg onwards impaired perf from hypo
Greater environmental temperature exacerbates the negative effects of hypohydration As environmental temperature increases, greater demand for skin blood flow, less blood available for cerebral and muscles, with hypo (lower blood volume) limits SV and CO. - affect on thermoregulation too- more delaterious at 40deg C
How does dehydration affect strength performance
Adequate fluid vs 2% hypohydrated
Max voluntary strength/ force production and resistance exercise performance (Cumulative total work completed - 2.5%) impaired with hypoperformance
Non voluntary the same
Not muscle that changes but ability to activate maximally
Change in hydration may be implicated in injury?
To do with contaction of muscles counteracting
Submax contraction may be RF for injury
How does hypohydration affect skill performance?
Before and after exercise 1h exercise in the heat Bowler performance Line and length negativly affected Velocity the same Shuttle run performance negatively impaired, impairment greater after exercise in hypohydrated
Simulated basketball Impaired shots on move but not on line At 2-4% sig, 1 not sig but mean lower
Link between endurance performance and hydration status
Why?
More weight loss, faster the performance
Massive individual variability
Top 10, everyone else but one lost >2.5% water loss from 3 different races
Higher metabolic rate, higher sweat rate Less comfortable to drink - access to fluid e.g. Picking up is hard Less time available to drink
Flaw in hydration status literature?
Previous data forces people to do things they dont want to do - often uncomfortable / psychological affects from dehydration protocol
Familirisation trials x4 before 45 min at 75%VO2max and then a TT
Performace worse initially
After familirisation, hypo results similar to euhydrated (trend still to be slightly worse), everyone improved
Change in performance between groups went from 6% to 1%ish
RPE - much lower after familirisation
Potential benefits of hypohydration?
Hypohydration in running is theoretically erogogenic - reduces weight
Some finish 8-10% body mass lost
Familiarisation attenuates Endurance training may do this
Best index for hydration status?
Plasma osmolality best index of hydration from sweat losses
Difference in hypohydration from sweat loss vs diuretics
Sweat loss sees greater loss in plasma vol from hypohydration than with furosemide (more comes from ECF). (isoosmotic sweat loss)
What threshold of % body mass loss affects aerobic perormance and cognitive function, mood, readiness, psychomotor function?
Hypohydration of >=2% of body mass loss degrade aerobic perf
Particularly if warm
1-2% reduction is generally tolerated if <90 min in 20-21C
2-3% neg effects sport specific skills
2-3% no effect on sprint performance
Dehydration (<3%) unlikely to reduce cognitive function, psychomotor function, mood and mental readiness, higher levels may make worse. Heat stress augments
why might a higher % body weight loss be worse/ affect performance more in some individuals than others?
Lean body mass = 74%, fatter then smaller total. Fatter people a % reduction means a greater reduction in total body water/ more sever hypohydration.
Heat aclimation state and aerobic/non aerobic components of sport also afffect performance.
Variability in effect on performance.
Smaller effects not identified by research
Why is hydration literature difficult to compare?
Research complicated by variation in fluid provision, exercise test, training status, heat acclimation status, environmental condition, nutritional status, drinking schedule and temperature of drinks. Often absence of familiarisation trials - may affect pacing.
How is percieved effort affected by hydration?
Sensation of effort increased with hypohydration
Effort also increases with temp
May be more significant in health setting
Describe the optimum consumption of fluid and electrolytes for performance
Should drink enough to limit to 2%.
Include sodium if high sweat losses (3-4g or especially >2hrs)
Don’t drink enough so that weight gain occurs.
Afterwards consume water and NA greater than loses Sodium only beneficical electrolyte Before exercise Na can help retain water
How can fluid and electrolytes aid thermoregulation
Cold fluid (0.5C) attenuates rises in temp in certain scenarios May improve performance by 10%
Na needed to reestablish ECF and replace sweat depletion
How does hydration and heat affect the brain?
Largely unknown:
How does the brain sense effort of exercise?
May be temperature?
May be changes to permeability of blood brain barrier by hyperthermia/ dehydration
Unclear
Fluid can prevent rise in S100B - brain protein
