I believe it would be Dickens and Twain !! Both were social critics.
I belive it 20 years of age
Answer:
The primary fuel the body uses during a long event of low intensity exercise (like a 4-hour walk) is FAT.
Explanation:
The system that intervenes during low intensity exercise is the AEROBIC SYSTEM.
Whenever someone exercises at a low level intensity, the body uses fat as main energy source while sparing the use of blood glucose and muscle glycogen in case the exercise level of intensity increases and while the oxygen availability decreases.
While training for long periods of time, aerobic capacity expands producing an increase in the oxidation of fats.
The maximal aerobic capacity (VO2max) of an individual regulates the contribution of different fuel sources in a proportional way (muscle glycogen, intramuscular triacylclycerols, glucose and fatty acids).
I hope it helps!
