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| Question | Answer |
| What factors affect fuel metabolism in humans? (5) | Intensity Duration Gender Nutrition Training Status |
| Why is it important to understand fuel utilisation? | If we can quantify it we can apply this to optimise nutritional strategies and training interventions to improve health and performance |
| Name 4 ways we can measure substrate oxidation | Indirect Calorimetry Douglas Bags Metabolic Cart Respiratory Chamber |
| What does indirect calorimetry do? | Provides a measure of whole body fuel metabolism |
| What do Douglas bags do? | Measure the concentration of O2 and Co2 Measure the volume of expired air Calculates VO2 and VCO2 |
| What do metabolic carts do? | Has a fast response real time O2 and CO2 analyser Can view data on a minute by minute basis Is the most up to date |
| What does a respiratory chamber do? | Is a sealed room which can be used for a long time Is the most accurate IC method. |
| State the respiratory quotient (RQ) | Co2/O2 |
| What does the RQ represent? | The O2 and CO2 exchange, representative of combustion processes occurring in oxidative tissue (eg. muscle) |
| State the glucose RQ formula | |
| What does an RQ = 1 indicate? | All oxidation has been CHO fuelled not fat fuelled. |
| State the fatty acid RQ formula. | |
| What does an RQ of 0.7 indicate? | All oxidation has been fueled by fatty acids not CHO |
| When does the RQ become invalid? | Over 85% VO2 max |
| Why does the RQ become invalid? | Hyperventilation leads to excess CO2 being produced which was not derived metabolically. Lactic acid accumulation occurs during high intensity exercise leading to increased buffering with bicarbonate, this leads to CO2 being produced. |
| How do you calculate whole body CHO oxidation? | CHO oxidation (g/min) = (4.21 x VCO2) - (2.962 x VO2) |
| How do you calculate whole body fat oxidation? | Fat oxidation (g/min) = (1.695 x VO2) - (1.701 x VCO2) |
| Where is Carbohydrate stored and in what form? | |
| Where are fatty acids stored and in what form? | |
| Where is blood glycerol in what form? | |
| What is the advantage of measuring blood metabolite concentration? | It is easy to repeat sample and measure |
| What are the disadvantages of measuring blood metabolite concentrations? | Doesn't give information about flux or what happens within the muscles. Only gives you a baseline measure. eg. provides a measure of glucose in blood plasma but not how much is utilised by the muscle. |
| What is anterio-venous blood sampling? | It measures the net glucose balance across the leg. Net balance = (arterial concentration - venous concentration) x blood flow |
| What are the advantages of anterio-venous blood sampling? | Provides information about net uptake or release across an organ/tissue |
| What are the disadvantages of anterio-venous blood sampling? | It is very invasive - requires a probe inserted in the femoral artery and femoral vein The probe can move - difficult to measure blood flow AV differences are difficult to detect Provides NO information about what happens IN the tissue. |
| Name the three needles that can be used to take a muscle biopsy? | Bergstrom needle Micro-biopsy (gun) needle Conchotome needle |
| What is the biochemical process to analyse muscle substrates? | 1) Immerse the sample in an isotonic homogenisation buffer 2) Grind the tissue 3) Centrifuge the sample 4) Intact cells, nuclei, membrane fragments and mitochondria will sink, supernatant will float. |
| What information does biochemical analysis of a muscle sample provide? What does it not take into account? | Substrate concentrations within skeletal muscle (mmol/kg muscle) Muscle fibre type differences |
| What is the Immunohistochemical analysis of muscle protocol? | 1) Muscle Biopsy 2) Freeze Sample 3) Cryosection Muscle 4) Stain Muscle Sections |
| How does muscle staining work? | Apply primary antibody at saturating concentrations Wash off excess antibody Apply fluorescently labelled secondary antibodies. |
| What is GLUT 4? Where is it found? | A protein encoded in humans that is responsible for transporting glucose. Adipose tissue & striated muscle |
| During exercise what happens to GLUT 4? | It moves towards the cell membrane to allow glucose into the muscle |
| What does electron microscopy allow us to do? | Consider the use of substrates from difference sub-cellular locations |
| Where is glycogen stored? | Distinct sub-cellular pods which are fibre type dependent. Subsarcollemal 5-15% Intramyofibrillar 5-15% Intermyofibrillar 75% |
| What is the advantage of analysing muscle biopsies? | Provides information about substrate/protein concentrations within skeletal muscle |
| What are the disadvantages of analysing muscle biopsies? | 1) It is invasive 2) Only gives information about concentrations (snapshot in time) 3) Changes over time require repeated sampling 4) Only analyses a limited number of fibres. |
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