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Is the tensing of muscles equivalent to stretching them? I am trying to understand what tensing of the muscles means.

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closed as unclear what you're asking by rg255, March Ho, James, fileunderwater, WYSIWYG Mar 15 '16 at 6:47

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Do you mean to ask the sarcomeric state of the muscle while maintaining posture? $\endgroup$ – Polisetty Mar 6 '16 at 22:30
  • $\begingroup$ Stretching of muscle means muscle getting relaxed while "if you tense your muscles, or you or your muscles tense, they become tight and stiff, especially because you are not relaxed" (oxfordlearnersdictionaries.com/definition/english/tense_3). So, tensing can be called a consequence of stretching of muscle. $\endgroup$ – another 'Homo sapien' Mar 7 '16 at 11:53
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    $\begingroup$ The course-work tag is nonexistent. Please don't put it back. Edits made by hi-rep users are often made for a reason. $\endgroup$ – AliceD Mar 9 '16 at 8:19
  • $\begingroup$ @WYSIWYG et al; what is not clear in this question? $\endgroup$ – AliceD Mar 16 '16 at 8:18
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    $\begingroup$ @Christiaan That's the point. This question can have multiple interpretations. 1. what you said 2. whether tensing/extending involve same molecular mechanisms 3. whether they are mechanically equivalent... and many more so. That's why I VTCed this as unclear. Plus OP did not respond to comments requesting clarification, for more than a week. Moreover "What happens when our muscle tense" is basically a homework type of question. $\endgroup$ – WYSIWYG Mar 16 '16 at 8:26
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Muscles are designed to contract i.e., when they tense they get shorter. Their stretch is a passive process, typically facilitated by antagonist muscles in case of skeletal (striated) muscles. Consider the biceps and triceps antagonists in the upper arm in Fig. 1:

arm
Fig. 1. Left: The biceps actively contracts to bend the arm and is called the agonist. The triceps is inactive and is passively stretched by the biceps, called the antagonist. Right: To stretch the arm, the reverse happens, i.e. the triceps contracts and is now called the agonist. The biceps is now inactive and is called the antagonist and it is passively stretched by the triceps. Source: Pilates Studio

At the molecular level, the tensing of muscles can be readily seen as contraction, as opposed to stretching (Fig. 2):

molecular muscle
Fig. 2. Muscle fibers contract actively and stretch passively. The passive stretched state is depicted in the upper panel. Under the influence of ATP (active part) the muscle fibers condense and the muscles contracts. source: Emaze Presentations.

Further Reading
- Do both ends of a muscle contract?

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