Muscle strain occurs primarily due to which of the following?

Muscle strain primarily occurs due to forceful contraction or overstretching of the muscle fibers beyond their normal limits. When a muscle is subjected to excessive tension—either from an intense contraction, like during heavy lifting or sprinting, or from being stretched too far—microscopic tears can occur in the muscle fibers. This can lead to pain, swelling, and limited mobility, which are common signs of a muscle strain.

The other options, while they can contribute to overall muscle health and function, are not the primary causes of muscle strains. For instance, improper nutrition might affect muscle recovery and maintenance, but it does not directly cause a strain during a physical activity. Similarly, inadequate hydration can impair performance and increase the risk of injuries over time, but it is not the immediate cause of a muscle strain. Lastly, a lack of flexibility exercises can lead to tight muscles, which might predispose someone to strain if they then engage in sudden or intense activities, but the act of overstretching or forceful contraction still remains the fundamental mechanism behind the strain itself.