Sport Nutrition first half Flashcards
(220 cards)
1
Q
Energy use in 100m vs 800m vs marathon
A
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)
2
Q
Describe Anabolism, unique for nutritionist
A
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
3
Q
Describe Catabolism
A
Catabolism
Carbs, lipids, amino acids (also nutriets from diet) + O2
Into H20 and CO2
Produces ATP
4
Q
Describe link between anabolism and catabolism
A
If someone wants to continue work (Muscular work = anabolism from contraction) they need catabolism - ATP resynthesis.
5
Q
What % of energy comes from protein?
A
5
6
Q
Describe the 3 roles of a sport nutritionalist
A
Educator
Translator
Bouncer
7
Q
Size of stores of energy
A
Protein 14kg Fat 10.5 Carbs muscl glycogen 0.4 (up to 1kg) Liver 0.1kg Blood glucose (0.01)
8
Q
Describe the 3 way interaction in energy balance. Increase in intake/ stores effect?
A
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.
9
Q
Give some factors that effect energy intake
A
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.
10
Q
Factors that affect energy expenditure
A
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
11
Q
Difference in calculating BMR and RMR
A
BMR vs RMR. Rarely BMR. BMR - after sleep without walking (12 hrs). BMR = 4 hrs after,
12
Q
How do TEE, DIT and RMR vary between sedentary adn very active (as a %)
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.
13
Q
How much does RMR vary?
A
RMR easily predicted by height, age and body comp. (differences only 10s of calories).
14
Q
calories in alcohol
A
7kcal/g
15
Q
how to convert from kcal to KJ
A
x4.2
16
Q
Explain how DIT varies with nutrition
A
Protein 25-30% is used to process protein
Carbs 6-8%
Fat 2-3%
17
Q
Why is a calorie not a calorie?
A
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.
18
Q
Relationship between effective calories and carb intake
A
As carbs decreases (replaced with fat and protein)
As carb decreases, effective calories decreases
Theoretical plan not real life.
Change in expenditure resultantly
x
19
Q
What is energy balance?
A
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
20
Q
What is energy availability? Significance?
A
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.
21
Q
Relationship between EB and low EA?
A
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)
22
Q
Why do both EA and EB need to be considered?
A
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.
23
Q
Describe risks of energy deficiency in sport (women)
A
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
24
Q
describe inadvertent failure to match EI with TEE
A
Exericse doesn’t affect acute Ad-libitum energy intake
Supresses relative energy intake
Via known neuroendocrine mechanisms
25
Describe appetite stimulant word and hormones
Orexigenic hormones: Ghrelin (appetite stimulant)
26
Describe appetite suppressant hormones
Anorexigenic hormones: PYY, GLP-1, PP, Leptin
27
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.
28
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
29
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).
30
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
```
31
Normal EB at EA 45kcal/kgFFM/day, same at low EA?
0, can be 0 at low EA also
32
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
33
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.
34
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
35
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.
36
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
37
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.
38
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
39
Ends of a fatty acid
Methly end (n-) and carboxyl end
40
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)
41
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)
42
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)
43
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
44
How do sources of energy differ with time?
Also as time increases proportion of fat for energy use increases as stores become depleted.
45
How does endurance training affect fat utilisation?
Increased fat oxidation during exercise will spare muscle glycogen
46
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
47
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
48
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
49
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
50
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?
51
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
52
How does fat diet affect VO2max?
INcreases as needs more O2 per energy created (less eficient)
53
Cases where high fat diet may be useful?
May benefit some ultra endurance athletes (very small groups)
54
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)
55
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)
56
Large meals vs small snacks for CHO synthesis?
24hr doesnt matter. < 8h then frequent snacks
57
Solid or carb CHO for glycogen resynth?
Similar
58
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
59
2 stores of CHO in muscle
Proglucogen
Macroglycogen
Extremes of spectrum
60
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
61
How does eccentric exercise affect glycogen resyth?
. eccentric ecercise which can impair post-exercise glycogen resynthesis - can be partially overcome by increased CHO.
62
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
63
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?
64
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
```
65
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
```
66
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)
67
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.
68
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
69
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
```
70
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
71
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
72
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.
73
How many kcal from running/ walking?
Running easy approx 1kcal per kg per km (walking or runnning)
74
How to calculate TEE
Calculate weekly training, divide bye 7, add daily average to RMR xPAL
75
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
76
How to convert mmol to g
Times relative molecular mass = mg, /1000 = g
77
Name the 8 essential amino acids
```
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Tryptophan
Valine
```
78
Name the 8 oxidised amino acids
```
Leucine
Isoleucine
Valine
Lysine
Glutamate
Aspartate
Alanine
Asparagine
```
79
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)
80
Describe outputs of the free amino acid pool
Urine -N
Sweat - n
CO2 (oxidation) - c
Tissue protein - C&
81
Describe how the relationship between muscle mass and age in a sedentary individual
In sedentary muscle mass remains unchanged (declines above 55)
82
Clinical significance of sarcopenia?
Clin sig - trips and falls
Lower metabolically active tissue
Lower vol/ mass to hold/ use glucose - diabetes risk
83
Sendentary requirements of protein
Approx 0.8g/kg/day
84
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
85
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.
```
86
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
87
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
88
How long do the effects of resistance training on NPB last in non-trained individuals?
48hr
89
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
90
Is 20g protein appropriate for athletes?
Depends on body weight/ size
In this study 80-85kg males
Amount of muscle mass activated
91
Are there any sex differences in NPS?
No sig difference using 25gs post work out (lower body resistance)
92
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.
93
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.
94
Milk vs whey?
80% of milk is casein so how does this make sense?
| Milk protein similar effects to whey
95
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
96
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
97
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.
98
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
```
99
When may a 40g protein bolus be appropriate
40g casein increase protein balance overnight, increased MPS
100
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)
101
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
```
102
Describe the structure of an amino acid
Amine group
Carboxyl group
H bond
R group (side chain) - 20 different
103
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
104
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
105
Effect of endurance exercise on leucine oxidation
Increased = more requirement assumed
106
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
107
Could pre exercise feeding hamper recovery?
Pre exercise feedining unlikely to increase MPS, also unlikely to hamper benefit
108
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
109
Why in leucine good?
Activate cell singalling in the protein kinase B-mammalian target of rapamycin (mTOR) pathway responsible for translation initiation.
110
Role of non-leucine aas
"leucine trigger" hypothesis
| To sustain after initial leucine mediated activation need other EAA in particular the BCAAs
111
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
112
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
113
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.
114
Does insulin enhance/ suppres mPS/ MPB?
None found it enhanced MPS or MPB
115
Physiological requirements for althetes recovering from exercise
Hydration
Restoration of metabolised carb
Restoration/ repair of damaged proteins
Remodelling proteins
116
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.
117
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.
118
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
119
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
120
Benefits of protein during exercise?
No difference, no significant effect of performance
121
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
122
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
123
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
124
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.
125
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
```
126
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)
127
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
```
128
Normal relationship between kcal intake and protein intake.
Normally linear relationship between kcal and protein
| Whey supplements may disrupt this
129
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.
130
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)
131
Could gastric emptying limit glycogen storage rate?
Gastric emptying rrate is unlikely to limit rate
132
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
133
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.
134
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)
135
How much protein minimum for insulinaemic properties
Protein should be in excess of 0.3g/kg/h
136
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)
137
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)
138
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
139
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
140
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
141
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
142
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
143
Max rate of exogenous carb absorption and ultisation?
max rate of 1-1.5g per minute
144
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
145
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
146
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
```
147
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
148
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
149
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
150
Performance benefit of glucose and glucose +sucrose
Glucose over placebo extra 10%
Glucose and fructose extra 8% over glucose
Power
151
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
152
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
153
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
154
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
```
155
CHO recommendation in sport
1.0-1.2 g/min (60-70 g/hour) during exercise
156
Times to restore CHO
General
2-4h prior - restore liver after night
1h prior
Post exercise recovery
157
How much muscle TAG?
Muscle TAG = 0.3kg
158
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.
159
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
160
What is glycogen sypercompensation
One leg cycling
Lots of carb
Depleted leg- supercompensation increased muscle glycogen above resting levels showing some trainability
161
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
162
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
163
High CHO team sport?
Football - high vs low for 3 days prior to a match
| 1.8km difference, intensity less too
164
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
165
Do high high CHO diet improve general sport performance?
Varying duration and CHO intake per day
| May be maximal is already me
166
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
167
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.
```
168
Risks of hypo from pre exercise feeding
Ingestion of glucose decreases blood glucose after CHO initially
Due to insulin and muscles
169
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
170
Why are muscle more receptive to glycogen 0-10hr after exercise?
increased GLUT 4
171
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
172
Potential limitations of training low glycogen
educed self-regulated training vol
Increased risk of injury when depleted
Increased risk of illness - URTI
173
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
```
174
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
175
Is a depletion phase necessary to maximise glycogen storage in trained individuals?
Nope not in trained just 24-36hr high carb intake and rest
176
Optimum carb load schedule for ultra endurance event
10-12g.kg/24hr for 36-48h
177
What is meant be general fuelling up?
What is meant by "general fueling up"
| Prep for events <90 min with 7-12g
178
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
179
Descibe speedy refuelling
<8hrs then 1-1.2g//kg/hr
| Benefits of small nacks
180
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
```
181
Burke, how is female glycogen storage different from males?
Small diff with menstrual cycle, females can store glycogen as well as males
182
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
183
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.
184
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
185
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
186
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
```
187
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
```
188
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
```
189
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
```
190
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
191
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
```
192
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
193
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
194
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?
```
195
Urine conc for hypohydration
Below 700mosmol/kg urine hypohydrated definitely
| Below 900 = hypohydrated according to Lewis
196
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
197
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)
198
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
199
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)
200
4 overall factors that affect hydration status
Drink palatability, volume, composition and rate of drinking
201
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
202
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
203
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
204
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.'
205
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
206
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
207
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
208
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
209
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
210
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
211
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
212
Best index for hydration status?
Plasma osmolality best index of hydration from sweat losses
213
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)
214
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
215
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
216
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.
217
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
218
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
219
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
220
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
