Module 2: Macronutrient Recommendations for Athletes Flashcards
1
Q
___________ are the primary fuel for muscle contraction
A
Carbohydrates
2
Q
Consuming carbohydrates will…
A
- Maintain high rates of carb oxidation
- Reduce ratings of perceived exertion
- Increase endurance capacity
- Delay the onset of fatigue
- Prevent hypoglycemia
3
Q
What should be your goals in regards to blood glucose levels during sport?
A
- To keep BG levels as stable and as close to the normal range as possible during exercise
- Less variation = constant availability of CHO to fuel activity = stable performance (ATP substrate present)
- Some variation will occur BUT adequate nutrition during training and before, during, and after activity can help to limit the magnitude of BG fluctuations
- To prevent hypoglycemia
- To spare glycogen
- The longer you can keep glucose levels maintained and glycogen storage the longer you will be able to go
4
Q
What do carb stores at rest look like?
A
- 4g in blood, a lot stored in muscle
- Based on diet, if not eating carb rich will pull glycogen and BG levels drop
5
Q
What do carb stores after 1 hr of exercise look like?
A
- Reduction in muscle glycogen
- Reduction in liver glycogen
- BG levels same
6
Q
What do carb stores after 2 hours of exercise look like?
A
- Greater reductions in liver and muscle glycogen than hour 1
- Slight reduction in BG
7
Q
What do carb stores after 3 hours of exercise look like?
A
Greater reductions in everything compared to hour 1 and 2
8
Q
What do carb stores after 4 hrs of exercise look like?
A
All stores are depleted and hypoglycemic
9
Q
______________ influences the size of glycogen stores
A
Diet
- Want to maximize glycogen stores to prolong activity
- High carb diet = more glycogen storage
10
Q
What is hypoglycemia?
A
Abnormally low levels of glucose in blood. <3.3mmol/L
11
Q
What does hypoglycemia trigger?
A
- Triggers the release of counter-regulatory hormones to prevent further declines in BG levels and promote gluconeogenesis:
- Epinephrine/norepinephrine
- Glucagon
- Cortisol
12
Q
What are the adrenergic manifestations of hypoglycemia?
A
- Shakiness, anxiety, nervousness (distracted)
- Palpitations, tachycardia
- Pallor, coldness, clamminess
- Dilated pupils (mydriasis), blurred vision
- Feeling of numbness “pins and needles” (paresthesia)
- Fatigue, weakness, incoordination
- Impaired judgement
13
Q
What are the glucagon/cortisol manifestations of hypoglycemia?
A
- hunger
- Nausea, vomiting, abdominal discomfort
- Headache
14
Q
What impact does hormonal response to hypoglycemia have on sport?
A
None of the symptoms associated with cortisol/glucagon/epinephrine hormones allow for strong sport performance. Need to be eating before performance
15
Q
When there is a decline in serum glucose what will result?
(Feedback loop)
A
16
Q
What are the 4 major hormones involved in regulation of blood glucose? What do they stimulate and what is their action?
A
17
Q
How can you prevent hypoglycemia in athletes?
A
- Adequate CHO intake on a daily basis → promotes glycogen storage and euglycemia
- CHO rich, pre-training or pre-event meal or snack BEFORE activity → ensures the athlete’s BG levels are within normal range at the onset of activity
- CHO feeding DURING prolonged activity → Tops up blood glucose levels and spares glycogen
- CHO rich re-feeding AFTER activity → Promotes repletion of glycogen stores used to fuel activity
18
Q
When should athletes eat before performance and what should they eat?
A
- > 1 hr carb feeding to top up
- Should be in the form of glucose that is readily available (gummies, gatorade) rather than starch but it depends on the person
- Some drinks like biosteel do not provide CHO so not helpful during
19
Q
Why might someone need a bedtime snack?
A
Glycogen stores may be broken down in the middle of the night because they are undereating. By breakfast have broken down glycogen and not hungry. Need a bedtime snack!
20
Q
What is reactive hypoglycemia in athletes?
A
- Condition in which low BG levels are induced by a combo of:
1. The timing of an athlete’s intake of CHO-rich foods/beverages +
2. The time of the start of activity - Excessive glucose intake by an athlete whose BG levels are marginally acceptable in the hour befor activity can trigger an excessive release of insulin before exercise promotes SM glucose uptake
- Exercise ( muscle contraction) also stimulates glucose uptae
- The result = hypoglycemia
21
Q
How can you prevent reactive hypoglycemia?
A
- Low glycemic index, CHO rich, pre-training or pre-event meal or snack BEFORE activity → ensures the athlete’s BG levels are within the normal range at the onset of activity (prevents reactive insulin trigger)
- High glycemic index, CHO feeding DURING prolonged activity → Tops up, BG levels quickly and spares glycogen
- High Glycemic index, CHO rich re-feeding AFTER activity → Promotes repletion of glycogen sotes used to fuel activity
22
Q
What should athletes eat prior to sport performance and throughout rest of the day?
(Carbohydrates)
A
- To support immediate sport performance, (pre/during/post exercise) the focus should be on quickly oxidized CHO
- Throughout the rest of the day athletes should focus on nutrient-rich sources of CHO, regardless of oxidation rate, including fruits and vegetables, whole grains, and legumes (All keep BG levels steady)
23
Q
What is the recommended fiber intake from food
A
25-30g/day
24
Q
What should athletes be aware of for zero calorie drinks?
A
- Zero calorie = zero energy
- Provide fluids and electrolytes but do not provide CHO!!
25
Why is daily CHO intake for athletes so high?
- Due to additional energy demands of training, CHO recommendations for athletes are higher than the general population
- The recommendations are meant to support CHO availability for the muscle and central NS based on the demands of the sport
- To support energy demands, recommendations are based on body weight
26
How should you determine CHO intake for athletes?
- Determining the right amount is an art and a science - choose a starting point based on recommendations, and then alter within the range based on how the athlete feels
- Based on type of activity
27
What are the recommendations for CHO intake?
28
What are the recommendations for CHO intake with strength training?
- 4-7g/kg/day
- CHO may increase the total amount of work an athlete is able to complete during longer duration, high volume training sessions
- Athletes should consume an amount of CHO that they can tolerate and makes them feel energized during their workout
29
What amounts of CHO should endurance athletes have according to recommendations? Why?
- 6-10g/kg/day - moderate training
- 8-12 g/kg/day - heavy training
- Fatigue in an endurance athlete is often due to depleted muscle glycogen and low levels of BG. Need big glycogen stores justifying need for increased CHO intake
30
What is another name for Carb loading?
Glycogen super-compensation
31
What is carb loading? How has the theory changed over time?
- Ergogenic dietary strategies designed to maximize glycogen stores in endurance athletes
- Involved dietary manipulations - CHO intake
- Evidence base on HOW to approach CHO loading has changed since it's first trials in the 1970s
- Contemporary CHO loading protocols are significantly different than what was recommended at the time that this approach was first conceived
32
What is the theoretical basis behind CHO loading?
- Low CHO diets deplete glycogen stores
- High CHO diets are known to increase muscle glycogen stores in trained individuals
→ More glycogen = more substrate for aerobic metabolism = reduced risk for "Hitting the Wall"
- Acutely increasing CHO intake in the days before an event will increase or super-compensate glycogen stores and enhance endurance
33
What was the original CHO protocol?
Originally, CHO loading protocols involved:
1. Eliminating all high CHO foods for 5-7 days before a race or competition to "empty" glycogen stores PLUS
2. Hard training to further deplete glycogen stores PLUS
3. Eating a large amount of CHO rich foods the night before the event to enhance glycogenesis
- This offered some performance gains but has been replaced by a newer, better approach
34
What is the modern carbohydrate loading protocol?
- Athletes should follow a CHO rich training diet most of the time to ensure sufficient pre-competition glycogen stores
- One week before the race or competition:
1. Increase CHO intake gradually: peaking one day before the race or competition
2. Decrease fat intake at the same time to allow for more CHO rich foods
3. At the same time, decrease or taper training across the week leading up to the race or competition to build up glycogen stores
- Target:
→ 36-48 hr of 10-12 g/kg body weight/24 hr
→ Athletes may choose CHO rich sources that are low in fibre/residue (too filling) and easily consumed
35
How do the classical and moderate glycogen supercompensation models differ>
36
What are the side effects of CHO training?
- **Weight gain/fluid retention**
→ The body stores 3-4g of water with every 1g of glycogen it stores
→ Much of this weight is extra water, but if it can create a heavy, sluggish feeling that can hamper performance (especially in large muscle groups
- **Digestive discomfort**
→ CHO rich foods are often high in fibre and dramatic increases in fibre intake can lead to gassy cramps, bloating, and diarrhea in some athletes
- **Blood sugar changes**
→ CHO loading can cause dynamic, predictable changes to blood sugar levels, especially in athletes with diabetes, reactive hypoglycemia or other endocrine conditions
37
Why would benefits of CHO loading only be accrued by athletes competing in events lasting longer than 90 minutes?
In longer durations would use glycogen stores whereas sports with shorter durations such as sprinters will not use glycogen stores for sport performance though training it may be necessary
38
How many CHO should athletes who are active for >1 hour consume?
- 30-60g/hr of easily digestible, quickly oxidized CHO (to stabilize BG levels)
- This is a time that fast CHO sources in the right amounts, are appropriate choices
39
What are good CHO sources **during sport**?
- Fluid replacement beverages containing CHO
- Sport Gels
- Sport Bars
- Sport Beans or Gummies
- Dried fruits (high in fructose not glucose)
40
What should athletes do if trying a new food?
Athletes should trial ANYTHING they want to eat or drink during sport (besides water) **in training** to assess tolerance
41
What is the purpose of carbohydrate mouth rinse? Has it been effective?
- CHO feeding during moderate intensity endurance exercise is well known to delay fatigue and improve performance
- A growing number of studies have now shown that routinely **rinsing the mouth (not drinking)** with a CHO containing solution for 5-10s during sport is associated with improved high intensity endurance during exercise performance
- Brain imaging studies have identified areas of the brain activated when CHO is in the mouth, and it is likely that mouth rinsing CHO results in afferent signals capable of modifying motor output and **perceptions of effort**
- Does not change glucose levels!
42
What is the practicality of CHO mouth rinsing?
- Athletes using the mouth rinse technique have to spit out the rinse - **it is not swallowed**
- This is messy, and potentially a vector for the spread of disease
- Many coaches and trainers oppose mouth rinsing as a result
- These practical issues need to be considered before attempting to implement this strategy
43
Is taken fructose during sport beneficial?
- Some athletes take fructose tablets or drink fructose rich beverages during sport out of a **mistaken** belief that fructose is a superior energy source
- Fruit juice blends, defizzed coke
- Lower GI
- Research has shown that fructose ingestion is associated with GI distress, higher perceived exertion ratings, higher serum cortisol levels, and decreases in BG levels compared to ingestions of glucose or sucrose
44
What are the pros and cons of liquid versus solid sources of CHO during sport?
45
When trying new liquid CHO sources what should athletes do and why?
- Athletes should trial fluid and CHO replacement beverages during training
- GI distress is a common complaint:
- For the fastest absorption of sports drinks its total concentration of electrolytes and CHO (osmolality) should be lower than the plasma osmolality (275-290mOsmol/Kg)
→ The osmolality of a beverage can influence the rate of gastric emptying
→ Hypertonic solutions slow gastric emptying and can promote GI distress (or too diluted will not have an impact)
46
How much CHO should be consumed after training and competition?
- Short Recovery Time
→ An athlete should consume 1-1.2g of CHO/kg/hr (0.45-0.55g/lb/hr) every hour for the first 4-6hrs post-exercise
→ Then resume regular dietary habits in order to quickly replenish glycogen stores
- Greater amount of recovery time
→ Meeting daily CHO needs should be adequate to restore muscle glycogen
→ Muscle glycogen stores can generally be normalized within 24 hours
→ More time may be needed if an athlete follows a low-carb diet
47
Put it all together - what are the CHO recommendations prior, during, and after exercise?
48
Why is protein important for the body?
- Structure
- Movement
- Immune function
- Transport
- Hormones
- Enzymes
- Cell signaling
49
What are the protein requirements for most people >18 yrs?
0.8g/kg/day
50
What are the protein daily intake guidelines for athletes?
- More muscle to maintain and protein needed to repair injury so increased protein need depending on sport
51
How are free amino acids formed and where do they go?
- Pool of amino acids in our body, need enough free amino acids to synthesize
- Dietary intake and de novo synthesis forms free amino acids which can be used for excretion/oxidation/non-protein pathways
- Can degrade and lose in skin/hair/feces or can be used for synthesis
52
Amino acids can go through muscle ____________ and muscle ____________
Muscle protein synthesis/Muscle protein breakdown
= Turnover
53
In hypertrophy and atrophy what predominates?
54
What is mTOR and its function?
- Mammalian target of rapamycin
- TOR proteins are found in all eukaryotes
- mTOR is a key driver of anabolic reactions in the human body
- Activated by nutrition and exercise
- Considered the "master regulator" of anabolism and MPS
55
What downregulates mTOR?
Cortisol! Athletes need to get enough sleep because lack of sleep increases cortisol levels so they cannot have as muscle synthesis
56
What are the two ways in which MPS is stimulated?
1. Protein ingestion - specific kinds of AAs
2. Muscle damage/exercise
57
Why do we get into NEGATIVE protein balance?
- Periods of negative protein balance are typically les than or equal to periods of positive protein balance
- Can induce negative protein balance by:
1. Caloric restriction
2. Bed rest/hospitalization
58
What are the effects of amino acids and exercise on MPS?
Amino acids and resistance exercise act **synergistically** to increase MPS BUT the types of AAs are relevant
59
What is the importance of **type** of amino acids in MPS?
- Increasing total protein intake with non-essential AAs (NEAA) does NOT increase MPS
- Want essential amino acids!!
60
What amino acid is the primary driver of MPS?
- Leucine!!
- Taking foods with high leucine content has been shown to have the best MPS
- With feeding alone and with feeding + exercise, 6g of whey protein with added leucine resulted in similar stimulation of MPS to 25g of whey protein alone
- Thus leucine is abe to drive the increase in MPS in the absence of elevated levels of other EAA
61
What foods are rich in leucine?
62
When increasing protein intake for MPS what is important to keep in mind?
- Limit to how fast muscles may increase in size and strength
→ Consuming excess amounts of protein will not cause muscle growth to occur at a faster rate
→ Need consistency
- Gains tend to decrease over time even with consistent training (Law of diminished returns)
- **Protein alone does not increase muscle mass!**
→ Effects of training and genetics (Ectomorph, endomorph, mesomorph)
63
What is the law of diminished returns?
- Gains tend to decrease over time even with consistent training
- Noticeable gains when starting and begin to plateu (point of diminishing returns)
- Point of maximum yield where more training can lead to negative consequences
64
Can protein be used as a fuel source during exercise?
- Occurs very infrequently in well nourished athletes
- Occurs when glucose or fatty acids are limited
- Body breaks down tissue proteins to use the AAs for glucose
- Results in **muscle wasting** - loss of weight and reduction in BMR
65
When is protein used as a fuel source during exercise?
- Can happen during prolonged exercise where carbs are not supplied throughout the exercise period (e.g. during the ironman, ultra-marathon)
- Can occur when athlete is undernourished
66
Why are fats important?
- Fuel for contracting muscles
- Absorption of fat-soluble vitamins
- Cell-membrane structure
67
At what intensities is fat utilized?
- Fat is the primary fuel at low-moderate exercise intensities
- As exercise intensity increases aboce ~60-65% VO2 max there is a shift in energy substrate utilization wherein fat oxidation decreased and carb oxidation increases
68
What two things influence when fat is being used?
- Exercise duration
- Exercise intensity
69
At what duration is fat utilized?
- Exercise duration also influences substrate metabolism
- As exercise duration increases the contribution of fat to total energy expenditure increases
70
Why do we want to utilize fat metabolism during exercise?
- FA metabolism during exercise yields more ATP than CHO metabolism on its own, but O2 is needed, which puts stress on the CV system
- At the same time, we know that high intensity exercise is absolutely limited by CHO availability:
→ Glucose
→ Glycogen
- This has created an interest in ways to spare muscle glycogen by increasing FA oxidation during exercise
71
What strategies can be used to spare glycogen?
- Medium Chain Triglyceride (MCT) feedings
- Fat loading
- Supplements such as caffeine
72
What is the theory/function of medium chain triglyceride feedings?
MCT:
- Normally present in our diet in very small quantities
- Few naturally occurring food sources
- Usually synthesized from coconut oil
- 8 to 10 carbon molecules
- Liquid at room temperature
- MCT's are quickly absorbed. After digestion, MCT's travel to the liver where they are immediately used for energy
- Theoretically, this means that MCT's could help to spare glycogen in athletes by providing a rapidly available substrate for aerobic metabolism
→ Don't have to be carried by chylomicrons and are transported very rapidly to the muscle
73
Coconut oil - What does evidence in the general population show?
Coconut oil is a source of MCTs and touted as health promoting
- Evidence (Non-Athlete populations) - Meta analysis:
→ Coconut oil increases total cholesterol by about 15 points, LDL by 10 points, and HDL by 4 points
→ No significant effect on body weight, waist circumference, or body fat percentage
→ Coconut oil contains as many calories and total fat as other fat sources, about 120 calories and 14 grams of fat per Tbsp (15mL)
- The american heart association has issued a scientific advisory cautioning the public to limit their intake of coconut oil due to cholesterol increases
74
How does coconut oil/MCT contribute to sport performance based on evidence?
- Ingestion of MCT (30g dose) does not spare muscle glycogen contributes less than 10% energy generation
- MCT< even when oxidized well, does not add much energy
- Ingestion of larger amounts of MCT results in dose dependent, gastrointestinal distress
75
Should athletes take MCT oil?
- Claims on bottles have not been substantiated
- Little evidence to show improvement
- Costly and not likely to cause benefits. Should spend money elsewhere
76
What does evidence on fat loading diets show?
- Researchers have explored the potential for high-fat, low CHO diets to enhance sport performance by forcing the body to oxidize fats at a higher rate, which would potentially spare glycogen and enhance endurance
- To date, the evidence to support this hypothesis has not offered strong support for fat loading/high fat diets for athletes
- High fat/low CHO diets reduce metabolic flexibility (availability of other fuel sources) by reducing CHO availability and capacit to use carbs effectively as an exercise substrate
- Athletes should not attempt fat loading or a high fat/low carb diet as this approach has the potential to sacrifice their ability to undertake high-quality training or high-intensity efforts during competition
77
What can caffeine do?
**Pharmacological ergogenic aid** (not nutritional) that has been shown to:
- increase time to exhaustion (TTE) - go longer, e.g. overtime
- Alter the perception of effort as a result of its impact on the CNS
- Alter levels of key enzymes in SM to down regulate CHO breakdown
- Enhance fat oxidation and decreasing CHO utilization (spares glycogen)
78
Caffeine __________ TTE During Sport
Increases
(unless too much then will see drop off)
79
How does caffeine, decaf, coffee, and placebo beverages impact finishing time of races?
Shorter races with coffee and caffeine!
80
Caffeine alters perception of __________
Pain
81
How does caffeine enhance sport peformance?
- The mechanism underpinning performance benefits are complex
- Benefits most likely involve caffeine's capacity to bind to adenosine receptors
- Adenosine receptors help regulate many physiological, neurological, and immunological processes which may lead to alterations to the perception of effort or fatigue, as well as direct effects on the circulatory system and SM
82
Does caffeine dose impact response and sport performance?
- There is no evidence of a dose-response relationship to caffeine
- More is not better
- Trial in training and use the lowest possible caffeine dose that maximizes performance potential. Over-loading has negative effects
- 250mL of chocolate milk may be enough for atheltes who not drink coffee or tea
- If always have it before practice, don't change for a game! Could experience withdrawal
83
What is hydroxycut?
- Popular weight loss supllement that claims to burn fat in part through caffeine action
- Interest by athletes due to claims related to leanness and body composition
- Claims to have 4-5x the weight loss than diet and exercise alone
84
What is the hydroxycut dosage?
4 capsules per day with water in conjunction with a calorie-reduced diet and regular exercise program
85
What are the ingredients in hydroxycut?
High caffeine levels, more than is recommended for caffeine
- High doses of caffeine can suppress appetite and promote diuresis
86
What are the dietary fat intake recommendations for athletes?
- Fats have many important functions in the human body and should NOT be excluded from the diet
- Intake of fat by athletes should be in accordance with public health guidelines and should be individualized based on training level and body composition goals
- 20-25% of total energy intake to support carb requirements
