Isometric exercise strengthens muscles without __________.

• A. changing muscle length
• B. producing lactic acid
• C. using oxygen
• D. increasing heart rate

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of isometric exercise. Isometric exercises involve muscle contraction without movement of the joint or change in muscle length. Examples include planks or wall sits.
2. Step 2: Analyze the options provided. The correct answer should align with the definition of isometric exercise, which focuses on maintaining a static position rather than dynamic movement.
3. Step 3: Evaluate the first option, 'changing muscle length.' Since isometric exercises do not involve joint movement or muscle length change, this option is relevant to the definition.
4. Step 4: Consider the other options: 'producing lactic acid,' 'using oxygen,' and 'increasing heart rate.' While these may occur during exercise, they are not defining characteristics of isometric exercises.
5. Step 5: Conclude that the correct answer is the option that directly relates to the defining feature of isometric exercise, which is maintaining muscle contraction without changing muscle length.