Question

In which type of exercise would fat reserves be used to create ATP? a strenuous, short hike with many steep climbs a moderate, but long hike over gently rolling hills

Answer 1

The second option. The longer the walk the more fat reserves used.
Hope this helps!

Answer 2

The right answer is the second option.

ATP is synthesizes in glycolysis, and through citric acid cycle.

In case of glucopenia (lack of sugars, after a long-term excerice), fat mobilization from adipose tissue is observed, followed by hydrolysis to fatty acids and glycerol.

Glycerol is used as a precursor in glucose recycling via gluconeogenesis: this accelerated gluconeogenesis requires energy.

Fatty acids are oxidized by beta-oxidation, pass through L-carnitine through the mitochondrial membrane (carnitine molecular shuttle) and via AcCoA into the citric acid cycle and even bring more energy that glucose burning but in the long run.