Which one of the following statements is incorrect about muscles in human body?
- AMuscles can only push the bone.
- BMuscles work in pairs.
- CMuscles become shorter, stiffer and thicker when contracted
- DMore than one of the above
- ENone of the above
Show answer and explanation
Correct answer: (a) Muscles can only push the bone.
Explanation
Muscles can only pull bones, never push them, so the statement that they only push is incorrect; a joint moves back because a second muscle pulls the other way.
Muscles act in antagonistic pairs – one contracts (agonist) while the other relaxes (antagonist), e.g. biceps and triceps.
On contraction the sarcomere shortens, making the muscle shorter, stiffer and thicker; on relaxing it becomes longer and thinner.