energy expenditure Flashcards
calories
amount of energy needed to raise 1g of water by 1c
measure of energy/heat
estimating energy expenditure
calorimeter- used to estimate how many calories a food contains- food in sample is oxidised, water around sample is heated and calculated how much the temp was raised
why measure EE
assess metabolic needs- work out how much someone needs to eat
fuel utilisation
thermic effects of food- digestion is an energy hungry process
nutritional interventions for performance and recovery
insight into demands of exercise
assessment of economy - how efficient we are
estimating EE
expired gas analysis - douglas bag indirect calorimetry
direct calorimetry involves analysing amount of heat from an individual whilst exercising by using a whole room
pros- direct measure of heat, accurate steady state measures
cons- expensive, slow to genrate results, few in operation, not accurate for dynamic changes
indirect calorimetry
RER= ratio between o2 consumed and co2 produced
RER for 1 mole of glucose= 1.0= 6o2 consumed and 6co2 produced
RER for 1 mole of palmitic acid= 0.7(fat) 23o2 consumed and 16co2 produced
IC pros
can detect chnages durinf exercise with breath by breath systems
no longer affected by heat of equipment
easy to administer
fairly accurate for aerobic measures
direct assessments of gas exchange
IC limitations
assumes body’s o2 content is constant and co2 exchange in lung is proportional to release from cells
but co2 released in lungs may not be representative of co2 released by working cells, body has o2 stores not directly refelcted in pulmonary measures
assumes little contribution from protein during exercise
but protein conrtributes up to 5% of total energy in prolonged exercise
RER values >1 wont proivide a valid estimate of energy expenditure (even values approaching 1)
gluconeogenesis from catabolism of fat and AA produces RER <0.7
caloric equivalents for o2
most energy per g- fat= 9kcal/gram
carb=4kcal/gram
most o2 per kcal- fat= 5kcal per L o2 consumed
basal metabolic rate
2-3% decrease in metabolic rate per decase
decrease in fat free mass
depression of metabolic activity of lean tissues
altered by change in body comp (increase FFM)
altered by physical activity- indepdendent of change in body comp
resting metabolic rate
energy expenditure in resting conditions- less tightly controlled vs BMR
MET
metabolic equivalent of a task
MET= multiples of RMR
1 met= 3.5ml/kg/min
VO2= 200ml/min for average sized woman
(=57kgx3.5ml/kg/min)
activity at 7ml/kg/min would be 2 MET
fat max
facilitation of fat metabolism is important to health and performance
exercise intensity at which maximal fat oxidation is observed as Fatmax
explained by lower availability of plasma FFA and reduced entry of fatty acids into mitochondria
EE for performance
slower recreation runners will run at 60-65% vo2 max
RER= 0.9
faster athletes will run at 70-75% vo2 max
RER= 0,95
elite runners will run at 80-90% vo2 max
RER=1
mechanical efficiency
external work accomplished/energy expenditure
average value for cycling, running and walking = 20-25%
swimming is less efficient due to drag at <20%
running economy
relationship between vo2 max and performance is not evident in homogenous groups of runners but is a relationship between running economy and performance
changes in vo2 max are not great over a number of years but running economy changes, meaning speed at same vo2 max increases
=lower cost of o2 but running faster
(graph in notes)
