Final answer:
The correct answer about barbells is 4) All of the above, as they can be used in most strength training exercises, allow adjustable weights, and are considered free weights.
Step-by-step explanation:
What is true about barbells? The correct answer to this question is 4) All of the above.
Barbells are versatile pieces of exercise equipment that can indeed be used in a wide range of strength training exercises. It is possible to adjust the weight on most barbells by adding or subtracting weight plates on either end, depending on the user's strength level and training requirements. Barbells fall under the category of free weights, which means they are not attached to a machine and require the user to stabilize the weight while lifting, engaging a broader range of muscles for improved strength training.
For example, a powerlifter might be lifting a barbell with multiple weights attached on each side, and the challenge involves correctly balancing and lifting the barbell to work on muscular strength and endurance.