Sports Nutrition Flashcards
Average daily energy required
2000-3000Kcal
Define RMR
Resting metabolic rate
The energy spent existing - doesn’t change
Define DIT
Dietary induced thermogenesis- energy spent on food intake
Define TEE
Thermic effect of exercise - energy expended on exercise
Order of energy stores used up
- Carbs
- Fats
- Protein
How are carbs stored in the body?
Liver + muscle glycogen + blood glucose
Relatively little stored but easy to access
Most important aspect of an athletes diet
ENERGY!
Consequences of low energy availability
Impaired performance
Relative energy Defiecency in sport/ Female athlete triad
Describe female athlete triad
Menstrual dysfunction, low bone density,+ disordered eating that occurs when a girl goes to extremes in dieting and exercise
Describe relative energy deficiency in sport
Condition arising from low energy availability leading to dysfunction in multiple body systems
List some consequences of REDS
Inc CVD risk due to unfavourable lipid profile + endothelial dysfunction
Psychological + mental illness
Inc risk stress fractures
Reduced immunity
Sleep disturbances
Reasons for underfuelling
Compulsive eating disorders
Intentional effort to improve performance by decreasing weight
Some sports eg Gymnastics unrealistic body expectations
Inadvertent failure to match requirements with intake
Define energy balance
Dietary intake - Total energy expenditure
Output from bodies physiological systems
Define energy availability
Dietary intake - exercise energy expenditure
Energy left after exercise to to anything else required
Weight gain energy requirements
> 45Kcal/kg lean body mass
Weight maintenance energy requirements
40-45kcal/kg lean body mass
Weightloss energy requirements
30-45kcal/kg lean body mass
Never go below 30
Exercise + appetite
Exercise suppresses ghrelin therefore reducing appetite so net energy intake is typically reduced with exercise
What happens if exercise is increased but energy intake remain the same
Other body systems compensate + use less energy which can lead to REDS
What is normal daily variation of water?
<=1% body mass
How can you measure body water
Use tracer technology eg Deuterium
- Take urine sample and measure concentration of heavy hydrogen
- Give known dose of heavy hydrogen
- Wait 5-10 hours, take another urine sample + measure conc of heavy hydrogen
How much of total body water is intracellular?
2/3rd
(28L in average 70kg male)
How much of total body water is extra cellular?
1/3rd (14L in average 70kg male)
How much total body water is interstitial
75% of extra cellular water
(10.5L in average 70kg male)
How much of total body water is intravascular?
25% of extra cellular
(3.5L in average 70kg male)
Methods of fluid intake
Drinking water/fluids
Food
Metabolic water (end product of respiration)
Causes of fluid loss
Urine, Faecal, sweat (sensible)
Skin, expired air (insensible)
Define Hyperhydration
State of sustained increase in H2O
Define Euhydration
Body mass within 0.2% of normal in temperate climate or within 0.5% of normal in hot climates/ in exercise
Define dehydration
Process of losing water
Define hypohydration
State of sustained decrease in H2O
Define plasma osmolality
Measure of different solutes in plasma
Regulated in range 280-290
What do osmoreceptors respond to
2-3% change in plasma osmolality
What do baroreceptors respond to
10% change in BP/ blood volume
Describe regulatory mechanisms of water balance
Thirst mechanism - sweat hypotonic relative to plasma - blood more concentrated- Inc plasma osmolality- thirst
Release of Argenine vasopressin - Inc water reabsorption from kidney
Key point in optimising rehydration
Need to make sure fluid intake is retained in the body - therefore need argenine vasopressin to be released.
Decreased urine output = Inc drink retention
Importance of mouth in rehydration
Drink needs to taste nice or it won’t be drunk
What suggests athletes start training hypohydrated
High prevalence of urine hyper osmolality at the start of training sessions
Key body areas in optimising hydration
Mouth
Stomach
Intestines
Circulation
Effect of rapid replacement with plain water
No release of vasopressin, prompt diuresis therefore difficulty with water balance and rehydration
How does rate of drinking affect rehydration
Slower intake is better as more H2O absorbed and ADH still released
Effect of sodium content on rehydration
Inc sodium content = dec urine output = better rehydration
Positive fluid balance is maintained, impacting plasma osmolality to prevent ADH levels from dropping
Impact of potassium on rehydration
Addition of K+ may aid overall water retention by regulating levels of intracellular fluid
Impact of carbohydrates on rehydration
Addition of carbs, particularly glucose enhances post exercise rehydration, potentially by influencing fluid balance mechanisms.
But only v high carb had a significant effect (>10%)
How does alcohol affect rehydration
Known diuretic but some studies suggest it’s effect is blunted when hypohydrated
Still wouldn’t recommend tho
Impact of milk protein on hypohydration
Appears beneficial- possibly as it slows delivery of nutrients and water as it clots in the stomach, allowing fluid balance to be maintained.
May also be a role of increasing plasma albumin and thus oncotic pressure but needs more research
Impact of whey protein on hypohydration
No benefits
Important factors for post exercise hydration
Drink palatability, volume, composition, rate of drinking
How much do you need to drink to rehydrate
More than the amount you’re hypohydrated by to account for ongoing losses
Problems with studies investigating impact of hypohydration
Blinding is difficult- expectant changes (doesn’t account for placebo/nocebo effect)
Methods to induce hypohydration are uncomfortable- that may also affect performance
Impact of hypohydration on endurance exercise performance
Hypohydration equivalent to 2-3% body mass impaired performance in the heat, where there is little fluid intake
Impact of repeat exposure to hypohydration on performance
It may mitigate some of the negative performance effects
Athletes may benefit from training in competition hydration conditions to familiarise themselves
Physiological responses to hypohydration
Decreased muscle and cerebral blood flow
Inc HR + cardiovascular strain
Low mood
Thirst mechanism
Heat syncope, heat exhaustion
Define pre-existing hypohydration
Start exercise in a state of hypohydration
Common in athletes with multiple training sessions in a day
May be used in weight category sports to purposefully lose weight
Define exercise induced hypohydration
Lose more fluid in exercise than you take in
Impact of temperature on hypohydration
Greater environmental temperatures exacerbate negative effects of hypohydration- blood vessels vasodilate therefore Inc blood flow to skin and dec blood flow to muscles
Why are faster runners more hypohydrated
Inc losses - more metabolic heat and higher sweat rate
Less comfortable and less time to drink
Hypohydration is theoretically ergogenic so less weight to be carried
Hypohydration and strength performance
Strength performance is only impacted at higher levels of hypohydration, when compared to endurance, accuracy and concentration
Consequences of low blood glucose
Fatigue
Inability to concentrate
Syncope
High carb diet v high fat diet impact on exercise
3-7 days high carb allowed for 210 mins of exercise compared to 88 mins for high fat
Energy source in high intensity exercise
Muscle glycogen- rapid + efficient release
Energy source if muscle glycogen used up
Fat (if no energy intake during exercise)
List 7 sources of carbs
Monosaccharides- glucose, fructose, galactose
Disaccharides- sucrose, maltose, lactose
Oligosaccharises - Maltodextrin (sports drinks)
Polysaccharides- amylopectin, amylose
Describe glucose metabolism in fasted state
No uptake from small intestine
Low insulin + high glucagon levels
Increased fatty acid oxidation by skeletal muscle + liver
Release of glucose via gluconeogenesis from liver to maintain blood glucose
Describe glucose metabolism in the fed state
Elevated glucose levels trigger release of insulin from pancreas
Increased glucose uptake, storage and oxidation in peripheral tissues using GLUT transporters
GLUT transporters can be insulin dependent or independent
What is the majority of fat intake
95% intake is Triglycerols
What is a TAG
Triacylglcerol
Glycerol backbone + ester link + 3 fatty acids
How are fatty acids classified
Based on number of carbon atoms + number + position of dbl bonds
Saturated fat = non double bonds
Monounsaturated fat - 1dbl bond
Describe relationship between exercise capacity and pre-exercise muscle glycogen content
Linear relationship- increased muscle glycogen = increased exercise capacity
Athlete carb requirements
Dependant on exercise intensity
Low intensity 3-5g/kg/day
High intensity6-10g/kg/day
V high intensity 8-12g/kg/day
Impact of short term fat loading
3 day high fat diet showed impaired performance compared to 3 day high carb diet
Impact of longer fat loading
Adaptation to inc fat oxidation during submaximal exercise within 5 days, decreased carb oxidation
No difference in performance
Describe dietary periodisation
High fat diet decreases muscle glycogen + decreases rate of muscle glycogen use so higher level fat oxidation.
1 day high Carb restores muscle glycogen
No significant difference in performance but data may be skewed by 1 individual
Results of low CHO high fat diet in elite race walkers
3 weeks of isoenergic diet either high carb, periodised carb or high fat low carb
3 day testing before and after
High fat diet less efficient and had negative impact on performance
Why periodise CHO intake
Allows for molecular adaptations
Increases PGCL-1 alpha which increases mitochondria biogenesis
Limitations of periodising CHO intake
May Inc risk injury or illness
May compromise training intensity
Summarise high fat v high carb diet benefit
High carb diets preferred for high intensity activity- athletes likely to benefit from fuelling to meet demands of exercise
High fat diets increase fat use during exercise and spare muscle glycogen
Recommended amount of carbs to eat before exercise
1-4g/kg carb 1-4 hours before endurance exercise lasting >60 mins
(Not v specific open to interpretation based on activity you are doing
Optimal time to eat before exercise
4hrs as that’s when muscle glycogen peaks
Effect of eating carb breakfast on performance
Psychological benefits to eating breakfast as both carb breakfast and placebo had faster times than water alone
Effectiveness of pre-exercise feeding
No difference in performance between carbs 4hrs before +water during vs placebo before and carbs uring
Aims of exogenous carbs
Provide additional source of fuel
Maximise oxidation rates
Prevent GI distress
Maximise performance
Benefits of exogenous carbs
Maintain plasma glucose - complete higher intensity exercise for longer
No placebo effect - 11% difference in performance between placebo + carbs
What is the rate limiting factor in exogenous carb consumption
Intestinal CHO absorbtion - maximum of 1.2g/min of glucose
Describe carb absorption
SGLT1 Transporter allows monosaccharides to cross brush border from intestinal lumen to circulation by active co-transport
Fructose transported instead by GLUT5
Why fuel with glucose + fructose
Allows you to absorb more carbs (0.6g/min fructose +1.2g/min glucose) so higher combined oxidation rate
As fructose uses GLUT5 transporter instead of SGLT1
Recommended carb intake during exercise
30-75 min exercise = mouth rinse
1-2hrs exercise = 30g/hr
2-3hrs exercise = 60g/hr of carbs that can be rapidly oxidised
Pros + cons of mouth rinse
Appears to improve performance compared to placebo
Avoids GI discomfort
But difficult to use during performance
Summarise the use of carbs during exercise
CHO feeding during exercise maintains plasma glucose conc
Carb intake improves exercise performance in events >45min
Exogenous CHO oxidation with single source limited to 1.2g/min but this can be increased to 90g/hr if use multiple sources
Describe glucose uptake by skeletal muscle
Glucose diffuses from cappillary to muscle surface membranes
Transported across membrane by facilitated diffusion
Irreversibly phosphorylated in myocyte by hexokinase (G to G6P) provided there is a glucose concentration gradient
Increased insulin increase uptake into myocyte through GLUT 4 translocation
Factors that affect glucose uptake
Supply - muscle perfusion, blood glucose concentration
Transport - glucose gradient, surface membrane GLUT abundance, GLUT activity
Metabolism- hexokinase activity, substrate flux
When to fuel after exercise
ASAP - wan to ensure muscle + liver glycogen stores are restored
Guidelines for fuelling post exercise
1-1.2g/kg/hour of carb for 2-4hours post exercise
How does the addition of protein affect post exercise fuelling
Addition of protein can enhance muscle glycogen re synthesis when carb ingestion is not maximised
As more insulin is released
Define state of energy balance
Individuals who maintain their body weight over a sustained period
What are the types of adipose tissue
Subcutaneous- just under skin
Visceral - deep in abdo cavity surrounding organs - major RF for CVD +T2DM
Obesity prevalence
Is increasing
2015 26.9% adults in England were obese
25% 4-5 year olds overweight or obese
White European BMI ranges
<18.5 underweight
18.5-24.9 ideal weight
25-29.9 overweight
30-34.9 obese
35+ morbidly obese
Asian BMI ranges
<18.5 underweight
18.5-23 ideal
23-27.5 overweight
27.5+ obese
Why are BMI ranges different for Asians and Europeans
Asians have higher body fat % at lower BMI
+ have increased visceral fat at lower overall body fat levels
Relationship between BMI + mortality
J curve
Significantly underweight has higher mortality
Healthy BMI lowest mortality
Than as BMI increases so does mortality
Nadir optimal range BMI
23.5 - 24.9 males
22-23.4 females
Comorbidites associated with obesity
T2DM, HTN, Liver disease, CVD, Mood disorders, repro disorders, dyslipidemia, cancer (breast + bowel in particular)
BMI limitations
Doesn’t distinguish between muscle weight and excess fat weight
Health risks of obesity are linked to fat distribution
Age/sex/ethnicity/muscle mass can influence interpretation
BMI benefits
Simple, inexpensive, non invasive
Good for tracking and identifying trends across a population
Benefits of waist circumference
Simplest measure of abdominal obesity
As waist circumference increases intrabdominal adiposity increases
Ethnic waist circumference thresholds
European male 94 female 80
Asian male 90 female 80
Define metabolic syndrome
Central obesity + 2 of raised triglycerides (>150), dec HDL (<40 males, <50 females), Inc BP, Inc fasting plasma glucose/T2DM
Puts you at increased risk CVD/T2DM
Influences on obesity
Food production, food consumption, societal influences, biology, individual psychology, individual activity, activity of environment
Define food environment
Physical, economic + social conditions that affect food choices - includes availability, accessibility + affordability of healthy + unhealthy food
Define food desert
Little access to foods that promote health + wellbeing
Importance of healthy food environment
Exposure to healthy food environments is a stronger driver of healthy eating than health promotion or education alone
Role of food in obesity
Eating out - more sugar, fat, salt + bigger portion sizes
Food outlets cluster near schools
Inc availability and consumption UPFs Inc obesity
Why do UFPs lead to obesity
Engineered to have supernormative appetite- excess eating
Tend to eat more calories when eat UFPs
Describe NOVA group 1
Unprocessed/ minimally processed foods
Fruit + veg, meat, fish, legumes, grains
No substances are added, processes include removal of unwanted/inedible parts
Describe NOVA group 2
Processed culinary ingredients
Plant oils, animal fats (lard, cream), maple syrup, sugar, salt
Derived from group 1 foods or nature by processes including pressing, refining, grinding + drying
Describe NOVA group 3
Processed foods
Canned veg or meat, cheese, beer, wine, cider
Processing of foods from group 1 or 2 with the addition of salt/sugar/oil by means of canning, pickling, smoking or fermenting
Describe NOVA group 4
Ultra processed foods
Sugar, sweetened beverages, sweet + savoury packaged snacks, ice cream, chicken nuggets
Formulations made by series of processes including chemical modification
Describe results of study investigating 2 wk UPF diet v 2 wk unprocessed diet
UPF Inc energy intake - 500kcal
UPF - faster eating rate
UPF significant weight gain
Impact of UPF on appetite
No significant difference in subjective findings
But studies showed increased PYY (appetite suppressing hormone) in unprocessed diet and decreased ghrelin
Why is improving populations diet an important govt focus
Diet plays significant role in burden of disease
Poor diet has big impact on health
Poor diet contributes to health inequalities
Define DALY
Disability adjusted life years
Measure of the burden of disease = years lived with disability, illness and injury
1DALY= loss of 1 year full health
What are the largest contributors to overall disease burden
Un healthy diet
Smoking
Inc BP
Inc BMI
Describe health inequalities due to diet
Much lower healthy life expectancy in most deprived areas compared to least due to less access to healthy diet for a variety of reasons
Describe health inequalities due to diet
Much lower healthy life expectancy in most deprived areas compared to least due to less access to healthy diet for a variety of reasons
Describe the hierarchy of research
1.Metaanalysis + systematic reviews
2.Intervention studies
3.Observational studies
4.Non human studies
How are govt guidelines on nutrition made
Based on evidence from independent expert committees eg scientific advisory committee on nutrition.
Findings from different levels of research are then integrated and translated into guidelines and recommendations
SACN carb recommendation
Carb intake should be maintained at 50% of total energy intake
Total carb intake is neither beneficial or detrimental to cardiometabolic, oral or colorectal health
Define free sugars
All sugars added to foods and beverages by the manufacturer, cook or consumer plus sugars naturally present in honey, syrups and fruit juices
Difference between added sugar and free sugar
Added sugar doesn’t include sugars naturally present in honey/syrup/fruit juice
Guidelines now use free sugar, as these should also be limited
What DOESNT count as a free sugar
Lactose when naturally present in milk
Sugars contained within cellular structure of food
Risk of high consumption of free sugar and sugar,sweetened beverages
Inc risk dental cavities
Inc risk T2DM
Inc BMI + weight gain
SACN recommendations free sugars
Average intake of free sugars should not exceed 5% total dietary energy intake from 2yrs +
Consumption of sugar sweetened drinks should be minimised in children + adults
Benefits to NHS of everyone reaching maximum free sugar recommendations
Save estimated £500 million per year by year 10
As have decreasing costs associated with obesity and dental cavities
How is the govt trying to reduce free sugar intake
Sugar tax
Considering mandatory sugar content levels
Stricter advertising laws
SACN fibre recommendation
Increase population fibre intake to average of 30g per day
Benefits of high fibre diets
Associated with decreased incidence of CVD, T2DM,Colorectal cancer
Decreased intestinal transit times, Inc faecal mass
Benefits of inc intake of oat bran + isolated B glucans
Lower total cholesterol and LDL cholesterol
Lower triglycerol concentration
Lower BP
How much fibre in bread, potatoes, oats and weetabix
1 slice brown bread - 2g
1 potato Inc skin - 2g
Half cup rolled oats - 9g
2 weetabix - 3g
Why reduce intake of saturated fatty acids
Dec risk CVD + CHD events (but doesn’t dec risk of mortality if do have CVD /CHD Event)
Dec total + LDL cholesterol
Improved indicators of glycemic control
Vegetable oils v plant fats
Vegetable oils - mainly unsaturated fatty acids, liquid at room temp
Plant fats - mainly saturated fats, solid at room temp
SACN saturated fats recommendations
Average contribution of SFA to total dietary energy should be no more than 10%
Try to substitute SFA for unsaturated fats
Describe DIVAS study
Replaced SFA with MUFA /PUFA totalling approx 9.5% total dietary intake
Lowered fasting total cholesterol + LDL cholesterol which corresponds to approx 17-20% decreased risk of CVD mortality
Define immunity
Ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitised wbc
List pathogen exposure factors that affect immunity
Abrasions + cuts
Crowds
Sick contacts
Foreign travel
Poor hygiene
Vulnerability to pathogens- factors affecting immunity
Psychological stress - nerves + anxiety
Physiological stress - exercise, dehydration
Poor diet
Environmental stress - too hot/cold
Impact of exercise on immunity
Intense exercise may initiate a transient immune depression
The number of immune cells available to fight pathogens is decreased in the 2hrs post exercise
Why is there debate as to whether exercise affects immunity
The reduction in immune cells is due to redistribution, it is unknown whether this impacts immunity
Why is diet important for immunity
Different components have effects in the innate and acquired immune pathways. Omitting a macronutrient also has a knock on effect for micronutrients
Impact of carbs on immunity
Important in innate immunity
1st response relies on glucose to function
Low carb diets increase cortisol (stress hormone), Inc cortisol = dec immune activation
Theoretically how does carb intake during exercise affect immunity
Theoretically in exercise carb intake helps maintain plasma glucose therefore attenuating normal rise in stress hormone + counteracting negative immune changes
Study results for carb intake during exercise effect on immunity
Decreased inflammation when carb was consumed
But little evidence that decreased immune disturbances translates to dec illness
May only be beneficial in prolonged exercise
Effect of protein on immunity
Important in adaptive immunity
AA glutamine is an important energy source for leukocytes in the innate and adaptive immune systems
What increases glutamine levels
Short duration high intensity exercise
What decreases glutamine levels
Prolonged low intensity exercise
Infection, acute or chronic fatigue
Effect of glutamine supplements
Studies show no benefit on immune parameters or illness incidence
V high protein diet + immunity study results
Decreased incidence of URTI in v high protein diet
But 3g/kg per day difficult to achieve
List water soluble vitamins
C, B6, folic acid, B12
Vit C + immunity
Some evidence Vit c decreases illness + immune disturbances
Linked to its antioxidant capacity
Vit D + immunity
Important for upregulating various cells that fight infection
Recent studies suggest Vit d supplements can dec URTI symptoms in general population
Probiotics + immunity
Often given but little evidence to support their benefits
List 8 essential amino acids
Leucine
Lysine
Isoleucine
Valine
Tryptophan
Methionine
Phenylalanine
Threonine
What is an essential amino acid
Can’t be synthesised in body so must be consumed in diet
List 8 amino acids oxidised for fuel
Alanine
Asparagine
Aspartate
glutamate
Isoleucine
leucine
lysine
valine
Describe AA structural
Central C atom
Carboxylic acid group (COOH)
H atom
Amino group (NH2)
R group
Net protein balance formula
Net protein balance = muscle protein synthesis - muscle protein breakdown
List different proteins in the body
Structural muscle proteins
Membrane proteins
Glycoproteins
Enzymes
Hormones
Describe protein turnover
All body proteins are in a state of constant turnover
Skeletal muscle is completely replaced every 3-4 months
In sedentary individuals with stable muscle mass - require 0.8g/kg/ day protein
What do you need to inc muscle mass
Net positive protein balance
Inc protein
Exercise as stimulus (typically resistance)
How do studies typically measure muscle protein synthesis
Participants do resistance exercise (often unilateral lower limb)
Manipulate post exercise protein nutrition
Take blood samples and muscle biopsy’s in combination with the infusion of labelled amino acids
Able to calculate rate of synthesis and breakdown
Why is Inc muscle breakdown good
Results in Inc synthesis + new muscle is better able to respond to stimuli
Effect of resistance training on mps
Resistance training had Inc breakdown and synthesis for the 1st 48 hrs post execercise in non trained athletes and 24hrs in trained athletes
How much protein should you intake to maximise muscle protein synthesis
Some studies showed 20g protein was maximal
But whole body training showed that 40g increased MPS further
Factors affecting amount of protein you should intake to inc MPS
Body size - no effect
Number of activated muscles - more muscles = more protein needed
Sex - no effect
Factors affecting amount of protein you should intake to inc MPS
Body size - no effect
Number of activated muscles - more muscles = more protein needed
Sex - no effect
Which protein source is best for MPS
Milk>soy>casein
Suggests it is protein quality/composition of AA that affects benefits
Impact of having protein in the evening (post exercise)
It increases overnight MPS
Recommended to have 30-40g protein before bed
Chronic effects of protein
Milk enhanced body composition changes
Milk slightly increased fat loss in males, bigger increase in females
No significant difference in overall body mass
Milk protein significantly increased lean mass
Effect of whey protein supplements over 9 months of training
Increased training induced gains
BUT
majority of gain was in first 3 months
Effect of protein supplements
Small but significant increase in 1RM strength, fat free mass and muscle size
How does energy deficit affect protein requirements
Increased protein requirements = 2g/kg/day, in order to reduce lean tissue loss
Why is protein requirement increased in endurance exercise
Some AAs oxidised in exercise (typically 5% energy but can Inc to 15%).
Required for mitochondrial biogenesis
Types of protein synthesis
Myofibrillar - Inc turnover in resistance exercise
Mitochondrial- Inc turnover in endurance exercise
Effect of alcohol on protein synthesis
Large amounts alcohol dec protein synthesis
But having both alcohol + protein post exercise has increased synthesis to rest alone
Protein + carb intake post exercise benefits
Amplifys glycogen synthesis
But ceiling of 1.2g/kg/hour
Enhances adaptation to endurance training - Inc gains in VO2 max
Daily protein requirements
Sedentary- 0.8g/kg
Endurance 1.2-1.6g/kg
Strength 1.2-1.7g/kg
What is sodium bicarbonate
NaHCO3
alkalinising agent
Baking soda
Energy production in >30s maximal exercise
Anaerobic glycolysis
Describe anaerobic glycolysis
Produces large amounts lactic acid (fatiguing metabolite)
Causes decreased PH
Lactic acid builds up in muscle causing fatigue.
To delay fatigue shuttle metabolites to blood
Hb + bicarbonate are buffers in blood that normalise H+ build up
But in intense exercise their capacity to excrete H+ is exceeded.
How does ergogenic sodium bicarbonate supplements works
Buffer H+ in blood (not muscle but will have a knock on effect) to help normalise pH levels.
Impact of sodium bicarbonate supplements in sport
Increased peak power output in repeated sprint performance
Best for events 1-7 mins long
No effect on strength but improvements in endurance
Optimal dose of sodium bicarbonate
0.2-0.4g/kg 60 to 120 mins pre-exercise
Downsides + alternative of sodium bicarbonate
GI side effects are common
It’s proposed sodium citrate has the same benefits without GI disturbance but not well supported research
What is caffeine
CNS stimulant, occurs naturally in plants
Increases alertness and delays onset of fatigue by blocking adenosine receptors
Mechanisms why caffeine improves performance
Not entirely known
1970s study - caffeine Inc fatty acid oxidation in aerobic exercise (but later studies showed improved performance without Inc oxidation)
Likely related to being a stimulant + making exercise feel easier
Might Inc Ca2+ release to enhance muscle force production
Caffeine optimal dose
3mg/kg
Effects of caffeine
Greater improvements in aerobic exercise compared to anaerobic
High individual variability in improvement levels
Increased fatty acid oxidation
Caffeine side effects
Tremor, bradycardia + palpitations, disrupted sleep, disrupted sleep, GI disturbances, irritability
Who gets benefits from caffeine
Both habitual and occasional coffee (caffeine) drinkers
Coingestion of natural ergogenic aids
Little evidence as research v time-consuming
Suggests sodium bicarbonate + beta alanine are beneficial as well as beta alanine and creatine
Where is creatine
95% in skeletal muscle
V little in brain despite having good impact on concussions
How is creatine excreted
1-2% degraded to creatinine daily + then excreted in urine
Where does creatine come from
50% from various foods
50% synthesised from argenine, methionine + glycine
How does creatinine works
In muscle contraction ATP is broken down to ADP + P
Therefore limited ATP supply in muscle
Creatine donates P to ADP allowing re synthesis of ATP leading to more energy for muscle contraction
Glycolysis and oxidative phosphorylation can re synthesise creatine
How much creatine do people store
Huge variation between individuals stores higher in meat eaters than veggies
Seems to be an upper limit/ceiling at 155mmol/kg
How to dose creatine
Loading dose 4x5g for 7 days - to maximise stores
Followed by 2g day maintenance dose
Take alongside carb to inc creatine (due to insulin spike alongside creatine transport)
Can also do 3g day over 28days will gradually reach max creatine levels
Creatine impact on muscle glycogen
Causes bug increase in muscle glycogen
Not sure on mechanism
Creatine + exercise capacity
Bigger increase in creatine = bigger Inc in exercise capacity- can maintain exercise intensity for longer.
Potential secondary mechanism for how creatine improves exercise
A H+is consumed in the reaction
H+ + pCr + ADP -> Cr + ATP
So may have a role as a buffer
Why do we need a buffer when exercising
Anaerobic glycolysis causes build up of lactate and H+ ions
Causes decrease in pH, can lead to fatigue
Need to buffer muscle + blood
Types of buffering
Physio-chemical - muscle
Dynamic - blood
Describe carnosine as a buffer
Carnosine synthesised from beta alanine and histidine
Helps use up H+, slowing down the decrease in pH
Why is beta alanine used as the supplement
Much less beta alanine in system than histidine so beta alanine is the rate limiting component
Beta alanine + carnosine have same results but beta alanine is cheaper
Describe diminishing returns of beta alanine supplements
Same dose has less impact as weeks go on
Muscle carnosine increased 60% over 4weeks but only 80% over 10 weeks
Beta alanine effect on performance
<0.5min no effect
0.5 - 10 min small but significant improvement
>10 min tendency for v small improvement
Nitrate background
Traditionally considered pollutant with negative effects on health
WHO set acceptable daily intake of 3.7mg/kg body mass
But recent research suggests it may be cardioprotective
Where is nitrate found
In most body tissues - blood, saliva, muscles, urine
Large levels in Breast milk
60-80% dietary nitrates in veg particularly beetroot + leafy greens
How much nitrate in veg
2 beetroot shots or 200-300g leafy greens=>500mg NO3
stored in plant vacuoles so boiling releases NO3 reducing levels up to 50%
Nitrate - nitrite - nitric oxide pathway
- ingest orally as NO3
- Some goes through digestive system so retaken to oral cavity where oral bacteria break it down to NO2
- Hypoxia + acidity of stomach allow further break down to NO
Effect of nitrate
NO leads to vasodilation
Decreased intramuscular perturbation- so slower decrease in ATP
Inc expression of calcium handing proteins - used in cross bridge formation + muscle contraction
Effect of nitrate on BP
Meta-analysis suggests average of 4.4mmHg decrease in systolic BP
Effect of nitrate on performance
3% increase in performance
But lower in elite athletes - potentially because mitochondrial pathways already optimised through other mechanisms
Factors affecting nitrate metabolism
Dietary sources - how veg is cooked/type of veg
Affinity for transport - smoking status
Oral - hydration, tongue brushing (good), mouthwash, recent use abx (bad)
Environmental temp,
Analytical conditions - tourniquet use, vacutainers, centrifugaion
Describe affinity for salivary uptake order
Perchlorate
Thiocyanate
Iodide
Nitrate
Things that may reduce salivary uptake of nitrate
Smokers - higher levels of thiocyanate in plasma and saliva
Brassica vegetables- contain thiocyanide
Impact of salivary flow rate on nitrate
Greater salivary flow rate = greater uptake of nitrate into oral cavity
Impact of temperature on salivary flow rate
Inverse relationship- cooler the temperature higher the flow rate
Nitrate ingestion blunts Inc in BP during cool air exposure
Nitrate rich beetroot juice is more effective at increasing salivary flow rate + plasma NO2 in cool conditions compared to normothermic conditions
Nitrate circadian rhythm?
Oral nitrite production found to be higher in afternoons in study of swimmers
Salivary pH also peaked in afternoon suggesting potential circadian rhythm
But other studies didn’t detect circadian rhythm in either nitrite production or salivary pH
Impact of biological sex on nitrates
Women typically have higher nitrate levels before + after beetroot juice
Women have Inc oral bacterial NO3 Reducing capacity
Women have greater NO3 reabsorption by kidneys
But women have lower salivary flow rates
Is there variability in response to dietary NO3 supplementation between males, eumenorrheic females and hormonal contraceptive users
Plasma NO2 higher in mid luteal phase than early follicular phase, but no differences in plasma NO2 delta change between groups
Pill users had biggest drop in BP - May benefit more?
Is nitrate supplementation affected by time they are taken
No differences in plasma nitrate/nitrite concentrations across morning, afternoon + evenings
Benefits of dietary nitrate supplements
Dec BP
improved exercise tolerance
What are micronutrients
Vitamins and minerals found in foods and supplements
Needed in much smaller amounts than macronutrients
Which vitamins can be synthesised in body
D and K
Describe thiamin (B1)
Whole grain, nuts, lean pork
Part of co-enzyme to aid utilisation of energy
Describe riboflavin (B2)
Milk, yoghurt, cheese
Part of co-enzyme involved in energy metabolism
Describe Niacin
Lean meat, fish, poultry and grains
Facilitates energy production in cells
Describe B6
Lean meat, vegetables,whole grains
Absorbs and metabolises protein
Aid RBC formation
Describe pantothenic acid
Whole grain cereals, bread, dark green veg
Aids metabolism of carbs, fat, protein
Describe Folic acid
Green veg, whole wheat products, beans
Coenzyme in nucleic acid synthesis + protein synthesis
Describe B12
Only in animal products
Nucleic acid synthesis + RBC formation
Describe Biotin
Egg yolk, dark green veg
Co enzyme in synthesis of glycogen and fatty acids
Describe choline
Beef liver, chicken, codfish, cauliflower
Cell membrane integrity and signalling + nerve transmission
Describe Vit C
Citrus fruits, green pepper, tomatoes
Intracellular maintenance of bone, capillaries and teeth
Describe Vit A
Carrots, sweet potatoes, butter, liver
Vision, formation + Maintenon skin and mucous membranes
Describe Vit D
Eggs, tuna, liver, fortified milk
Aids growth and formation of bones and teeth, aids Ca absorbtion
Describe minerals
Inorganic compounds essential in many body reactions + processes
Can be divided into macro minerals and micro minerals (trace elements)
Don’t provide any energy but assist in metabolism, growth and develop
List microminerals
Iodide
Zinc
Copper
Manganease
Selinium
Molybdenum
Fluorine
Chromium
Cobalt
Iron
Describe calcium
Milk, sardines, dark green veg
Bones, teeth, clotting, nerve and muscle function
Describe chlorine
Salt
Nerve and muscle function, water balance
Describe magnesium
Nuts, seafood, whole grains, leafy veg
Bone growth, nerve, muscle, enzyme function
Describe phosphorus
Meats, poultry, seafood, eggs, milk
Bones, teeth, energy transfer
Describe potassium
Fresh veg, bananas, citrus fruit
Nerve and muscle function
Describe sodium
Salt
Nerve and muscle function
Water balance
Describe chromium
Meats, liver, whole grains, dried beans
Glucose metabolism
Describe fluoride
Fluoridated drinking water, fish, milk
Bone and teeth growth
Describe iodine
Iodised salt
Seafood
Thyroid hormone formation
Describe iron
Red meat, liver, eggs, beans, leafy veg
O2 transport in RBC, Enzyme function
Describe manganese
Whole grain, nuts, fruits, veg
Enzyme function
Describe molybdenum
Whole grains, organ meats, peas, beans
Energy metabolism
Describe selenium
Meat, fish, whole grains, eggs
Works with Vit E
Describe zinc
Meat, shellfish, yeast, whole grains
Enzyme function, growth
Importance of micronutrients in relation to athletic function
- Growth+ building new tissues
- Oxygen transport
- Co factors in enzyme catalysed reactions
- Immune function
- Antioxidants
Important micronutrients in growth
Calcium important in bone formation, Vit D helps calcium absorption
P important for cell membranes
Fluorine important for tooth decay
Important micronutrients in oxygen transport
Hb + myoglobin need iron
Folic acid RBC production
Phosphorus-encourages O2 release into local capillary networks
Important micronutrients as cofactors in enzyme catalysed reactions
Niacin + riboflavin important for NAD + FAD production
Zinc - coenzyme in energy metabolism
Magnesium- synthesis of enzymatic antioxidants
Important micronutrients in immune function
Vit ACE - dec free radicals
B12, Folic acid - WBC production
Zinc - antioxidants
Selenium- synthesised production of antioxidant glutathione enzymes
Why are antioxidants useful
Body forms free radicals which damage cells and alter their function
Anti-oxidants stabilise free radicals by donating their spare electron
Do athletes require increased intake of micronutrients
No
Recommended level can be gained from healthy balanced diet
Too high levels may have toxic or negative performance effects
Situations where increased micronutrients may be required
Hot humid environments + prolonged exercise- prolonged sweating
Increase uptake of Mg, Zn, Fe and Na in days before and during exercise
Situations where micronutrient supplements may be required
Weight category sports - dec energy intake, but still want to meet micronutrient guidelines
Vegans - B12 only absorbed from meat, red meat best source of Fe
Possible rationale for Vit C + E supplements
Severe exercise induced muscle damage
Produces more free radicals
So antioxidants Vit c + e help reduce number of these - less pain (DOMS)
Force produced at optimal level of free radical production- performance may be negatively effected if too many produced
N-acetyl L-cysteine benefits
Antioxidant
Study’s suggest it decreases fatigue
Important aspects of endurance exercise fuelling
Fuel during exercise- intake carb
Fluid requirements- maintain euhydration + electrolyte imbalance
Post exercise recovery- fuel ASAP for Inc glycogen formation
Causes of fatigue during prolonged exercise
Substrate depletion (muscle glycogen) - Inc stores before + during event
Accumulation of metabolic by products
Loss of body fluid
Hyperthermia- cold drinks can prevent this
Carb intake for v high exercise (4-5hrs day)
8-12g/kg/day
4hrs post exercise- 1-1.2g/kg/hr
Peripheral effects of carb supplementation
Maintenance of blood glucose
Maintenance of CHO oxidation
Glycogen sparing
Why are carbs before exercise important (morning)
Liver glycogen decreases overnight as it constantly supplies the brain, therefore need to replenish liver glycogen
Impact of carb intake during endurance exercise
Beneficial
Cycling TT performance increased 11% compared to placebo (not psychological improvement)
Key nutritional considerations in strength sports
Energy balance
Daily protein intake
Strength sports energy requirements
Absolute requirements typically greater than endurance athletes but relative requirements lower (due to greater body mass)
Strength sports protein intake
20-25g per meal usually sufficient Inc to 40g post exercise
Whey>Soy>casein
Timing not particularly important
Why is nutrition important in injury
Lower energy expenditure so need to decrease energy intake, but still need to ensure add intake of nutrients key for recovery
Common athlete focuses nutrients goals
Achieve and maintain correct physique
Meet energy demand of training and competition
Promote adequate hydration
To recommend a specific nutrition strategy need to understand demands and goals of event
IOC supplement definition
A food, food component, nutrient or non food compound purposefully ingested in addition to habitually consumed diet with the aim of achieving specific health or performance benefits
Types of supplements
Isolated/ concentrated products- protein powder
Functional/ enriched food eg water with fluorine
Sports foods - carb gels
Multi ingredient products
Describe isolated product supplements
Ergogenic aids
Don’t consume adequate amount in diet to optimise performance- pills needed
Creatine, beta alanine, bicarbonate, caffeine, nitrate
Describe sports foods supplements
Essentially food
Could just consume in diet, but supplements may be easier or more practical
Some crossover eg nitrate is in beetroot - but realistically not gonna eat that much beetroot
Why do people use supplements
Correct/prevent nutrient deficiencies
Convinience
Direct performance effect
Indirect performance effect - prevent injury/illness, enhance recovery, amplify training response
Financial
Insurance policy - just in case
Believe others are using it - herd mentality
Greenhaffs rules for evidence based supplement use
Sound rationale for use
Know what biochemical/physiological function it targets
Does it reach target tissue
Does it meaningfully change tissue concentration
Meaningfully alter physiological function
Meaningfully alter performance/ trading adaptations
Good supplements for marathon runner
CHO
Water
Caffiene
Nitrate
Good supplement for 800m runner
Creatine
CHO loading
Nitrate
Sodium bicarbonate
Beta alanine
Good supplements for fat loss (in a rugby player)
Protein
Creatine
Caffiene
Why use supplement testing
Several cases of athletes blaming positive doping tests on supplements
14.8% of supplements contained WADA banned steroids or pro hormones - cross contamination
Just 2.5ug is enough to cause a positive test
How to know if a supplement is ok to use (doping wise)
Only use supplements with informed sport sticker
Been officially tested
