This is a difficult question to answer definitively for two main reasons. First, answering what is "most important" can run more into personal opinion, than fact. Second, the skill of Taekwondo that ultimately result in success for self defense is a mutual combination of many muscle groups throughout the entire body working simultaneously.
The initial response might be to say that the most important is the "brain," however the brain is anatomically not a muscle. However, it could be viewed as the most important organ since this is the command center for controlling the muscles and other organs, as well as being responsible for learning, memory, and decision making.
Organs such as the heart and lungs should not be overlooked, since the lack of cardiovascular conditioning can cause the best fighter to lose steam, become fatigued, and fail to perform to maximum potential. In fact, the overall health of all organs, muscles, and tissue of the body is often viewed as the most important aspect of training. Be healthy - be strong - be prepared.
As for the anatomy of the body, one of the primary muscle groups responsible for generating power is the abdominal region. However, all the muscles of the body are used in unison to maximize the force delivered to a target, so none can be singled out as the most important. The chain is only as strong as its weakest link.
The most important muscle in your body is your heart. Everyone should know that.
diaphram
the diaphragm is the muscle(s) that are most important muscle used in inspiration (inhalation)?
Your heart is by far the most important muscle in your body without it none of the others would work.
Name of the muscle is Trapezius.
Diaphragm
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tae kwon doA+
The heart is the most important muscle because it has to pump blood constantly thru out the body
hamstrings
muscle tone
muscle is one of the most important tissue in your body.you need muscle to move drink blink and everything else u eount bbe a ble to walk either.