Final answer:
Respiratory fatigue in healthy individuals can occur at high exercise intensities (>80%-85% peak oxygen consumption) and is generally experienced in accessory ventilatory muscles, not the oxidative nature of the diaphragm muscle, which has high endurance. Extended submaximal workloads are less likely to cause respiratory fatigue. a) may occur with high (>80% to 85% peak oxygen consumption) exercise intensities
Step-by-step explanation:
In healthy individuals, respiratory fatigue may occur with high exercise intensities and is usually due to the increased demand on the respiratory system to meet the oxygen needs of the body. Notably, during high-intensity exercise, typically at levels greater than 80% to 85% of peak oxygen consumption, the respiratory muscles have to work harder to accommodate the increased rate and depth of ventilation, known as hyperpnea. In this situation, respiratory fatigue generally occurs in the accessory ventilatory muscles, which include the neck muscles like the scalenes during forced inspiration, and muscles of the abdomen such as the obliques during forced expiration, in addition to the internal intercostals that help to compress the rib cage.
It's important to note that respiratory fatigue is less common due to the oxidative nature of the diaphragm muscle, as it is highly resistant to fatigue. During extended submaximal workloads, fatigue of the respiratory muscles is not typical. The diaphragm, being the primary muscle of respiration, has a high endurance and can sustain prolonged periods of activity without fatigue, which makes sense considering the vital role of breathing in sustaining life. In contrast, the accessory ventilatory muscles, which are not typically used as much as the diaphragm in breathing, may fatigue more readily when they are recruited during high-intensity or forced breathing activities.