could you summarize this in the most non echnical language?

All these energy systems are interconnected, and all three are operating at all times.
However, the intensity and duration of activity dictates which energy system dominates
energy production at any moment in time.
Anaerobic and aerobic metabolism happen simultaneously during exercise according to
the energy system overlap. During low-intensity, long-duration exercise, aerobic metabolism
supplies the body with energy, and fatty acids are the primary substrate used. During highintensity exercise, the body relies on both anaerobic and aerobic energy systems, and
carbohydrates are the preferred energy substrate for high-intensity, short-duration exercise.
However, these ratios change based on dietary intake.
Amino acids are oxidized when muscle glycogen is used up and quickly used carbohydrates
are a limited fuel source. When amino acids are depleted, the body must still maintain blood
sugar to fuel the nervous system and other working cells. Gluconeogenesis is the backup
fuel generation system for low- to moderate-intensity activity.
People in peak physical condition can use more fatty acids as a primary energy substrate
(yielding more ATP), but their bodies may use higher amounts of protein via gluconeogenesis.
HYPOGLYCEMIA:
The condition of lower-thannormal blood glucose.
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0 10 20 30 40 50 60
Running Time (seconds)
Energy Contribution (%)
120 180 240 300 360
ATP/CP System
Glycolytic System
Aerobic System
ATP/CP System
• 0-10 seconds
• 100m sprint
Glycolytic System
• 10-120 seconds
• 400m swim
Aerobic System
• Over 2 minutes
• Marathon
Figure 6.7 Energy System Overlap
Consider a resistance training workout where a client is executing an exercise at a moderate
intensity and the exercise lasts for 60 seconds. The client then takes a 2-minute rest before
completing the next set. During the first set of activity, they will likely be relying on energy
produced during glycolysis—the anaerobic energy system that dominates for activities lasting
1 to 2 minutes. Then during their rest of approximately 2 minutes, the energy demand is
relatively low, and the oxidative energy system will dominate during this time.
Similarly, sitting quietly to read this textbook does not require a lot of immediate energy. The
body is using the oxidative energy pathway and, in most cases, relying on fatty acid oxidation
for energy. If the reader was to quickly stand up and begin sprinting, the dominant energy
system will shift based on the duration of the sprint and the body’s immediate energy need.
A 10- to 15-second sprint will rely on the ATP/CP energy pathway while a 90-second sprint will
likely rely on anaerobic glycolysis.
Steady-State versus Intermittent Exercise Metabolism
Aerobic metabolism is a more efficient means of energy production—meaning it yields more
ATP per substrate used. In addition, the by-products, carbon dioxide and hydrogen, are more
easily eliminated from the body than the by-products of anaerobic processes. However, in
the first moments of exercise, aerobic metabolism is minimally active and cannot meet
immediate energy needs. Therefore, all activity draws energy first from stored ATP, then from
the phosphagen energy pathway, then glycolysis. When the anaerobic threshold is achieved,
the body uses the aerobic or oxidative system as its primary output.
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CHAPTER 06 | E M
During steady-state exercise, in which the level of exertion stays constant from start to
finish, the body reaches an aerobic plateau. Here aerobic metabolism remains the primary
source of energy. When exercise stops, oxygen consumption remains elevated for a short
time to return the body back to its resting metabolic state. This is known as excess
postexercise oxygen consumption (EPOC) or oxygen debt. EPOC helps replenish ATP stores
used up during exercise and eliminates waste products via respiration. When ATP has been
restored and waste products eliminated, the body returns to baseline respiratory rate,
temperature, and heart rate.
During most team sports, energy demands are intermittent, that is, lasting for short periods
of time with frequent rests, such as football, basketball, and baseball. When energy demands
are great, such as during a sprint down the field, energy is provided anaerobically. When
the body stops or slows, oxygen consumption stays high to restore ATP. This cycle happens
continuously. If high-intensity bouts are short, recovery time is short. If bouts are longer, then
recovery will also take longer. Eventually, aerobic energy metabolism kicks in to supply energy
for continued short, intense, intermittent activity