Which of the following is not an effect of a muscle strain?

The choice indicating "pain and swelling causing restricted use" does not accurately represent a non-effect of a muscle strain. Instead, it is a well-known and common symptom associated with muscle strains. When a muscle is strained, it typically leads to pain and swelling in the affected area, which can indeed result in restricted mobility or use of that muscle, as the body instinctively guards against further injury.

In contrast, the other listed effects are more characteristic of acute muscle strains or injuries. For instance, swelling and bleeding between ruptured muscle fibers represents the physical damage caused at a cellular level during a strain, which can happen depending on severity. Instant pain, lack of mobility, stiffness, and weakness also reflect typical responses to a muscle strain, indicating immediate impact and subsequent functional impairment. Lastly, sudden pain, along with feelings of instability in the joint and the appearance of swelling, aligns closely with more severe strains or other musculoskeletal injuries.

Thus, the core aspect of the original choice is that it incorrectly states a symptom that is intrinsic to the effects of muscle strains, while other options more accurately depict various conditions and symptoms that arise from such injuries.