The chapter discusses exercise metabolism and several key concepts:
1. During rest, ATP is produced aerobically, while during exercise transitions ATP is initially produced anaerobically through the phosphocreatine and glycolysis pathways due to a lag in oxygen uptake.
2. The lactate threshold occurs when blood lactate levels rise systematically during incremental exercise, around 50-60% of VO2 max in untrained individuals, and is likely due to low muscle oxygen levels and accelerated glycolysis.
3. Fuel selection during exercise is dependent on intensity and duration, with low intensity exercise relying more on fat oxidation and high intensity relying more on carbohydrates due to faster fiber recruitment and increased epinephrine levels.