In an isotonic contraction, the muscle ________.

• A. relaxes completely after a brief contraction
• B. does not generate any force
• C. remains the same length while the tension increases
• D. changes length while the tension remains constant

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of isotonic contraction. Isotonic contractions occur when a muscle changes its length while maintaining constant tension. This is different from isometric contractions, where the muscle length remains the same while tension increases.
2. Step 2: Break down the options provided in the problem. Analyze each one to determine if it aligns with the definition of isotonic contraction.
3. Step 3: Evaluate the first option: 'relaxes completely after a brief contraction.' This does not describe isotonic contraction, as isotonic contraction involves sustained tension while the muscle changes length.
4. Step 4: Evaluate the second option: 'does not generate any force.' This is incorrect because isotonic contractions involve force generation to move or resist a load.
5. Step 5: Evaluate the third and fourth options. The third option, 'remains the same length while the tension increases,' describes isometric contraction, not isotonic contraction. The fourth option, 'changes length while the tension remains constant,' matches the definition of isotonic contraction and is the correct answer.