An abundant and continual supply of atp is necessary for all living cells. active muscle cells require an extraordinary amount of atp to permit strenuous exercise for prolonged periods. toxins, reduced blood flow, and a compromised respiratory system can interfere with the transport of oxygen to active cells. a runner in a marathon faces multiple obstacles to continue to produce sufficient atp to remain competitive. when oxygen delivery becomes insufficient to support a runner's aerobic metabolism, cells switch to an emergency mode in which

Explained.

Explanation:

When oxygen delivery becomes insufficient to support a runner's aerobic metabolism, cells switch to an emergency mode in which ATP is insufficiently produced and is lactic acid is produced as by product. Thus the runner finds difficult to remain competitive in the race because of lack energy.

To overcome this state the runner needs to increase his/her oxygen in take. This why it is advised to breath deeply.

there is not 1 highest source of protein, but there are many; meats, fish, poultry, seafood, cheese, eggs, yogurt and milk. the only non complete animal food that is beneficial is gelatin.

sorry if this did not , have a great day!