Kin 432 W4: Powering High Performance: CHO and Fats

metabolic pathways

Carbs are king
Protein: not used much as fuel (2%)

In athletes: We’re maximizing availability, storage and feed for performance

What’s an issue with high fat, low CHO diets for performance?

They downregulate access to the CHO

Best fuel for start-stop, athletes?

Carbs and creatine

Role of CHO in exercise and performance

• Prolonged exercise

  • Supports endurance by maintaining glycogen

• Intermittent-intensity exercise (soccer, basketball):

  • Provides quick energy for high-intensity bursts

• High-intensity exercise:

  • Immediate energy needs for optimal performance

• For recovery in sport:

  • replenish glycogen for subsequent training

  • aids muscle repair when combined with protein

where can we find carbs in our body

• Muscle: 3-400g

• Liver: 75-100g

• Blood: 4.5g (maintains blood glucose 3.9-5.5 mmol/L

how much in liver? what does it do? how does it get depleted?

75 - 100g

Supports blood glucose level at rest and during exercise

Depleted by overnight fast to <20g

how much in muscle? what does it do? how does it get depleted?

300 - 400g (Level varies slightly with diet. higher with high-CHO diet, and large muscle mass)

• Supplies glucose for muscle - lacks G6P

• Use increases with exercise intensity

• Depletion: depends on exercise intensity

how much in blood? what does it do? how does it get depleted?

~4-5g maintain blood glucose 3.9 - 5.5 mmol/L

• Used by brain (and exercising muscle, as muscle glycogen becomes depleted)

image of glucose in cell

at rest: carbs broken down to glucose. insulin released in response. insulin receptor attaches to insulin on surface of cell. GLUT4 mobilization from centre of cell to surface. allows glucose molecules to enter cell

at rest, not using that glucose much so they are chained together to form glycogen

exercise: break down glycogen.

Can we use muscle glycogen to keep our blood glucose high?

Muscle glycogen depletion is proportionally to duration and intensity.

But, muscle glycogen is only used locally for muscle contraction. It lacks the G6P enzyme needed to convert glycogen to glucose

Liver glycogen does have G6P which allows it to control blood glucose

Rest: insulin → GLUT4 → glucose uptake → glycogen storage
Exercise: glycogen → glucose → ATP

Why should i eat carbs as an athlete?

• Sustain daily training, health and wellbeing

• Replenish liver and muscle glycogen stores - post training and sleep

  • liver depleted during night to replenish blood

  • no more than 20g available in the morning

Carb cycling based on menstrual cycle

bs

Carb Requirements vary depending on

training intensity and duration

how often to eat carbs

Should be consumed throughout the day

Should be altered day by day to reflect training load

training load can vary between

Light / Skill-based ( <1 hour/ day):

• 3-5 g/kg/d

Moderate (~1 hr/d):

• 5-7 g/kg/d

High Endurance (1-3hr/d):

• 6-10 g/kg/d

Very High / Extreme(>4-5 hr/d)

• 8-12 g/kg/d

Strength training (3-5 sessions/week):

• 4-7 g/kg/d

Intermittent sports (1-2 hours per session several days/week):

• 5-7 g/kg/d

key takeaways.

1. High glycogen availability improves

exercise capacity and performance

2. Depletion of glycogen stores can lead to

fatigue and decreased performance, particularly in endurance sports

We have limited capacity to store carbohydrate so

exogenous (external) carbohydrate must be consumed if exercise is to continue at a high intensity - or we will need to switch to a different fuel source which will slow the rate of exercise down

Athletes need to pay particular attention to the

recovery window and think ahead to the subsequent exercise / performance bout in order to start the session with adequate glycogen stores

Carbohydrate reserves are about

~500 g - 2000 kcal

CHO reserves vs fat reserves

~500g (2000 kcals) vs almost unlimited!

CHO: can’t access that fat. stored with water so can’t store too much. Have to top it off constantly

Fat: It is a compact way to store energy!

What are the fuel contribution changes with duration? intensity?

As duration increases:

1. > 2 hours: don’t have CHO left over, so we turn to fats

2. 30-90 mins: Majority of ATP fueled by muscle glycogen and plasma glucose

Increased intensity = Increased CHO use

Summary of CHO vs FAT use for fuel during exercise

CHO: fast, limited, essential for intensity

FAT: slow, abundant, useful for low/moderate intensity

In-session fuel for exercise. what kind of fat

mobilized storage forms (IMTG, FFAs), not the fat on your plate that day

intramuscular triglycerides = IMTG

What are the fat recommendations for athletes?

do not change hugely from healthy population:

20-35% of total energy intake from fat

<10% of energy from saturated fat is typically advised

Is taking less than the recommended amount of fat (20-35%) okay

Very low fat intakes (<15-20%) are not recommended because they can compromise essential fatty acid intake, fat-soluble vitamin absorption, and hormone production

considerations in setting daily carbohydrate intake targets for athletes

Range is 3-10g/kg/day of CHO depending on what you’re doing

carbohydrate intake based on training volume/CHO range recommendation best practices

CHO range is a guiding point but also rely on athlete feedback in order to meet their needs

what range of carbohydrates does a 75kg runner running for 2 hours need

Requires 6-10g CHO/kg body mass per day

• Weight = 75kgs

• Carbohydrate = 450 – 750g per day

CARBOHYDRATE RECOMMENDATIONS BASED ON TRAINING (g/kg/day).

already covered

Light / Skill-based 3-5

Moderate (~1 hr/d) 5-7

High Endurance (1-3 hr/d) 6-10

Very High / Extreme (>4-5 hr/d) 8-12

how about resistance training?

intermittent/team sports?

Strength Training 4-7 g/kg/d

Intermittent / Team Sports 5-7 g/kg/d

SUMMARY SO FAR

1. In the majority of athletes, low glycogen stores will

bring activity to a premature end OR result in lowered intensity

3. Carbohydrate guidelines for athletes are calculated based on (3)

frequently and based on number of hours, intensity and type of sports

4. Carbohydrate guidelines are calculated based on

kg body mass - which assumes athletes have reasonable body fat %

THE PRE-EXERCISE MEAL

Purpose

1. Restore liver glycogen after an overnight fast in morning

   1. drops to 20g from 75-100g

   2. breakfast is important if you skip dinner!

2. Increase / replenish muscle glycogen

3. Prevent hunger and provide energy during exercise

4. Psychological boost

pre exercise meal guideline

main meal 2-3 hours before exercise lasting >60 min

Provide ~1 - 4g CHO/kg before exercise

Contain fluid

Avoid very high fat and spicy foods

Moderate in protein

30 - 60 minutes before exercise top up with high GI carbs

rational: main meal 2-3 hours before exercise lasting >60 min

To allow for gastric emptying before exercise

rational: Provide ~1 - 4g CHO/kg before exercise

Restore liver glycogen. Increase / replenish muscle glycogen

rational: contain fluid

Contribute to hydration; some athletes may prefer liquid meals

rational: avoid very high fat and spicy foods

Facilitate gastric emptying; minimize GI distress

rational: moderate in protein

filling?

can lower it if cant meet carb target.

rational: 30 - 60 minutes before exercise top up with high GI carbs

Quick source of glucose

image of pre exercise meal high and low in sugar

when to have low sugar?

low 2-3 hours before training/games with high fiber

like wholewheat pasta, multigrain bread, sweet potato, brown rice, oatmeal...

when high sugar?

high 30-60 min before with low fiber

banana, jellies, dried fruits, sport drink, fruit juice

CHO during exercise GUIDELINES

During exercise: 

Brief exercise < 45 mins: no top up need after big meal 

High intensity exercise 45 - 75 mins: mouth rinse for 10s

mouth rinsing

Evidence for maltodextrin based carb oral rinse

Rinse for 10 s with isotonic drink

Practical application: mouth rinsing

• weight category sports

• Athletes with GI upset

• Remember - ideally athletes ingest carbohydrates

CHO During Exercise:

already covered brief and sustained high intensity

Intermittent “start stop” sports

Duration: 1-2.5 hours.

Consume: 30-60 g/h to spare muscle glycogen and maintain blood glucose levels

CHO During Exercise

Covered: brief, sustained high intensity, stop start sports.

Ultra Endurance Events

Duration: >2.5-3 hours.

Can oxidize up to 90g/h

Use of different intestinal transporters may increase overall CHO absorption

• maltodextrin : fructose

• glucose : fructose

• glucose : sucrose : fructose

Note: recommendations based on oxidation rates not total CHO content of real food - so consuming slightly more to tolerance may be advantageous e.g. 100 - 120g/h = ~90g/hr oxidized

What is important to remember for ultra endurance CHO composition during ultra endurance?

Diff types of sugar needed for the diff types of receptors to maximize absorption

image of absorption sites inside intestine.

• SGLT1:

• transports glucose and galactose

• has limited capacity

• GLUT5 transports fructose

FUELING DURING ACTIVITY. soccer player that is 75 kg

Pre-game, 30 mins before game, During 90 minutes game

Pre game meal:

• 75 – 300g before exercise

30 mins before game

• Sips from sports drink

• During 90 game

• 45 – 90g carbs

example from protein module: athlete weight is 92kg.

how much protein per day? per meal? how many eating occasions per day?

92 x 1.6 = 147 g

92 x 0.3 = 28 g

147 / 28 = about 5 eating occasions per day

CHO sport nutrition products

designed for elite athletes.

specially formulated to allow maximal carbs to be absorbed. easy for athletes to get down quickly...

CHO after exercise:

What can be done to facilitate recovery between glycogen depleting training sessions?

It is critical for is for people training twice in a day, especially if < 4 hours between sessions

if 100 min run in morning (depletes glycogen stores), and then a bike ride later in the day. it is critical that they follow a plan. need to aggressively consume carbs between sessions

Guidelines for CHO after exercise when next session < 4 hours away

1-1.2g CHO/kg/hr for the first 0-4 hours after exercise.

• may not need to be as aggressive when they have a longer rest period and enough time to eat a few meals and replenish those stores.

• Prioritize liquids and high GI food

• Adding protein might be advantageous

when building a nutrition plan (CHO), you must (7 steps)

1. Calculate approximate energy expenditure per day

2. Examine current food diary - 4 to 7 days

3. Select appropriate carbohydrate range per day

4. Focus first on fueling pre, during and post exercise - usually med - high GI foods during and immediately post

5. Subtract what has been used for these events and build remaining meals / snacks using this value

6. Work with individuals gi comfort, tastes and lifestyle

7. Work at meeting overall needs and smarter choices for better health

example:

70 kg

endurance athlete. 1-3 hr/d mod-high intensity

6-10g/kg so 420-700g

summary now

Carbohydrate is important particularly for

endurance sport - reserves are limited, and when depleted, performance at intensities >65% VO2max decline

• Recommended daily carbohydrate intakes for elite athletes are based on

body weight, training intensity and duration with many fluctuations during training cycle

• The pre-exercise meal should have:

CHO (1-4 g/kg, 2-3 hrs pre-exercise) and fluid

• Carbohydrate requirements during exercise will differ depending on

exercise duration and use of clinical judgment and expertise is critical

• Carbohydrate refueling post exercise is a high priority particularly when the next

glycogen depleting session is ≤ 4 hours away

• Sports foods rich in carbohydrate can and likely should strategically be used in

high performance sport

BELOW THIS WAS NOT COVERED IN CLASS, NOT IN MIDTERM