Exercise nutrition

Question 1

What are the four sources of energy?

Answer 1

First two are vast but produce ATP slowly
1. Oxidation of fat
2. Oxidation of carbohydrate
Anaerobic glycolysis and phosphocreatinine are smaller stores but produce ATP more quickly
3. Anaerobic glycolysis
4. Phosphocreatinine

Question 2

What does phosphocreatine fuel?

Answer 2

Any intense movement performed over a few seconds

Question 3

What is phosphocreatine metabolism like?

Answer 3

Phosphate is liberated from PCr and used to make ATP in the following reaction:
PCr + ADP -> Cr + ATP, ATP is energy required for movement

Question 4

What is glycolysis?

Answer 4

Conversion of a 6C molecule into 2x £c fragments of pyruvic acid and 2 ATP- very fast

Question 5

Where does glucose in glycolysis come from?

Answer 5

Glycogen stored in muscle

Question 6

What else does glycolysis produce?

Answer 6

Lactic acid as a by-product which makes the muscle acidic (6.5 pH) after about 20s of maximal exercise, this in turn inhibits the enzymes of the pathway

Question 7

How long does the action of phosphocreatinine and glycolysis last?

Answer 7

Both the anaerobic processes only provide enough energy to keep muscles working maximally for about 3-40 seconds

Question 8

How is energy mainly stored?

Answer 8

Much more stored as fat than carbohydrate

Question 9

How are carbohydrates stored?

Answer 9

As liver glycogen, muscle glycogen and glucose in bodily fluids

Question 10

How are fats stored?

Answer 10

Subcutaneously and intramuscularly

Question 11

What are fats metabolised into?

Answer 11

Glycerol and fatty acids. Fatty acids undergo beta oxidation and glycerol can be used to form glucose/glycogen in glycolysis

Question 12

What are carbohydrates metabolised into?

Answer 12

From glycogen/glucose into pyruvate via glycolysis, a by-product of which is lactic acid. Pyruvate also forms acetyl-coA and enters TCA cycle to produce ATP, CO2, NADH and FADH2. NADH and FADH2 then enter the electron transport chain which produces ATP and H2O with the addition of oxygen

Question 13

During light exercise what is the majority of energy from?

Answer 13

Burning of fat

Question 14

What happens as energy intensity increases?

Answer 14

Use of CHO as an energy source increases.

Question 15

When does CHO become the dominant fuel source?

Answer 15

At 60% VO2 max

Question 16

What is hitting the wall?

Answer 16

Limit of fat oxidation- carbohydrate reserves have run out, maximal fat oxidation is only 0.7g/min which is much slower

Question 17

What percentage of dietary calories should be from CHO in a normal diet and athletes diet?

Answer 17

50% in normal
70% in adults
Recommended amount is 6-10g CHO/kg body weight

Question 18

How much carbohydrate should be consumed during exercise?

Answer 18

Carb drinks shown to be effective but there is maximum ingested carbohydrate oxidation rate of about 1g/min which is reached at ingestion rate of 2g/min. If higher, GI issues can occur with excess CHO in intestine due to limited number of CHO transporters

Question 19

How is the rate of protein synthesis measured?

Answer 19

Patient drinks a radiolabelled drink with 13C labelled phenylalanine so that there is a known circulating amount of this circulating amino acid. Muscle biopsies can be taken to determine how much of the labelled amino acids have been incorporated into the muscle fibre. The more that has been incorporated, the more synthesis that has taken place.

Question 20

When do muscle protein levels increase?

Answer 20

When there is net muscle protein synthesis

Question 21

What influences synthesis and breakdown of muscle?

Answer 21

It changes diurnally and is highly influenced by feeding. After a meal, there are more amino acids in the pool and therefore higher synthesis

Question 22

What are the guidelines for an appreciable increase in muscle mass?

Answer 22

8-12 reps at 70-80% of 1-RM, 3 days per week

Question 23

How can the anabolic response be maximised?

Answer 23

Ingest more protein so that more amino acids are in the muscle pool.

Question 24

What is the maximal effective dose of protein for stimulating post-exercise MPS rates?

Answer 24

20g- increasing above this to 40g didn’t show any further increase in muscle fractional synthetic rate, just an energy source for liver

Question 25

How does muscle mass change with age?

Answer 25

20-30 year male- 50% of body weight is muscle mass

75-80 year male- 25% of body weight is muscle mass

Question 26

How does muscle synthetic response change with age?

Answer 26

Elderly have anabolic resistance to dietary protein- their muscle synthetic response is attenuated.

Question 27

Give summary of the lecture?

Answer 27

Resistance exercise and protein feeding increase muscle protein synthesis
Maximal effective dose of protein for stimulating post-exercise muscle protein synthesis rates is 20g
Elderly individuals have anabolic resistance to both exercise and protein intake compared to the young
Protein supplements don’t further increase muscle mass after resistance training in adults unlike young adults