Well your heart is used for breathing it's a cardiac muscle by the way :-()
These would be the abdominal muscles.
Breathing out in crocodiles is a passive process. As the muscles used for inhalation relax, the chest cavity naturally decreases in size causing air to be expelled from the lungs. Crocodiles do not have a diaphragm like mammals to actively control their breathing.
Breathing is the process that would be adversely affected, as these muscles contract and relax when you breathe in and out.
Diaphragm
On average, humans use about 5-10% of their daily energy expenditure on breathing. The energy is mainly used for the muscles involved in the breathing process and to warm, filter, and humidify the air we breathe.
Muscles are used for picking things up, breathing, seeing, and/or doing a physical activity, such as walking.
Ribs are for protection i think and diaphragm is the muscle controlling inhaling and exhaling. Also: the rib muscles can help the breathing process, which is useful when the diaphragm is weak, constricted, or to get an extra-big breath. Breathing from the diaphragm makes the belly move in and out as the lungs extend downwards. Breathing from the rib muscles makes the chest expand and rise.
The diaphragm, the external intercostal and the interchondral portion of the internal intercostal muscles are the main muscles that control breathing. Other muscles are sometimes used, but only if the person has a breathing disorder or if the body needs energy very quickly.
external intercostals and the diaphragm
1. diaphragm 2. external intercostal muscles 3. internal intercostal muscles (only in forceful exhalation such as coughing not relaxed breathing)
These are diaphragm and externa intercostal muscles in quiet breathing and sternocliedomastoid ,sclene muscles,anterior serrati in heavy breathing
Forced breathing, or active breathing, involves the use of additional muscles to increase the volume of air inhaled or exhaled, typically during vigorous activities or exercises. In contrast, quiet breathing, or passive breathing, relies primarily on the diaphragm and intercostal muscles, functioning without conscious effort. During forced inhalation, accessory muscles such as the sternocleidomastoid and scalene muscles are engaged, while forced exhalation may involve the abdominal muscles and internal intercostals to expel air more forcefully.