As explained in the post maximizing fat utilization the product of the amount of energy utilized and the percentage of that energy derived from fat sources needs to be maximized.
In a laboratory we can utilize expired air analysis to accurately determine how much oxygen a person is using and the amount of carbon dioxide they are expiring in order to determine a “respiratory quotient” a measure of the sources of energy they are utilizing.
In the gym I use a polar heart rate monitor (model M61) to give an approximation of the respiratory quotient. Further I simultaneously use a Polar S610i to record and evaluate heart rate throughout the session.
The monitor calculates the amount of energy used based upon heart rate and factors such as your age, sex, weight, height activity level and current fitness level.
Based on the amount of time spent in each heart rate zone, it calculates a both the amount of energy expended (in kilocalories) and the percentage of that energy derived from fat sources.
These two factors can be multiplied, (their product) to produce the amount of energy derived from fat (in kcal). This product can then be divided by 9 (the amount of energy liberated from each gram of fat metabolized) to show the number of grams of fat used in the session.
Maximizing fat utilization requires four processes,
- Assessing the original workout
- Stage 1 : Increasing fat utilization
- Stage 2 : Maximizing fat utilization
- Stage 3 : Increasing time spent
The discussion outlined will represent a typical female, late 20's, 60 kg, 166-175cm, moderately active.
The original workout utilizes approximately 400 kilocalories of energy, 35% of which is derived from fat.
400 x 35% = 140 kcal fat. This represents approximately 16 grams of fat used (140/9=15.56)
Generally they work too intensely, represented by heart rate ranges in the 160-170 bpm range. Often the initial high intensity period is followed by a period of weight training of moderate to low intensity.
Although a lot of energy is utilized, little of it is derived from fat sources.
Stage 1 involves increasing the percentage of energy derived from fat. This generally involves reducing the intensity of the session.
As the intensity of the session is reduced, so too will the total amount of energy used.
Within the 60 minute session, 320 kcal are used, but a higher percentage of it comes from fat, say 50%.
This equates to 160 kcal of fat (320 x 50%), which equals approximately 18 grams of fat.
Stage 2 refines this process over the next 3-10 sessions.
The intensity of aerobic activities is further maximized and the session re-arranged to include two (or more) sets of weights between each aerobic exercise.
This allows the total energy expended to increase back to the original rate 400kcal and improves the percentage fat use to 55% (or even 60%) .
This results in 400 X 55% = 220 kcal of fat which equates to approximately 24 grams of fat utilized.
By Stage 3, we've maximized the amount of fat utilized through a continuous process of refinement.
At this stage we try to slightly increase the time of the session.
By increasing the session length by 25% we can expend more energy, getting us to our objective slightly faster.
So let's look at the changes effected. An initial workout of 60 minutes which used 16 grams of fat has been evolved into a 75 minute workout which uses 31 grams of fat.
As can be seen from the chart, that's an investment of a 25% increase in time resulting in a 96% increase in fat utilized. This effectively doubles the return for investing just 25% more time, essentially halving the time it takes to reach any objective.
***For more posts relating to fat loss see fat loss articles)***
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Regards Kym
