A muscle that provides the major force for producing a specific movement.

Correct Answer: B

Rationale: The prime mover, also called the agonist, is the muscle primarily responsible for generating a specific movement. For example, in knee extension, the quadriceps act as the prime mover. Deep refers to muscle location, not function. Antagonist opposes the prime mover, while synergists assist it, neither being the main force. The prime mover's role as the dominant muscle in producing movement is a core principle in kinesiology, making it the correct answer. This term encapsulates the muscle that drives the action, distinguishing it from supporting or opposing muscles, and its significance is evident in every coordinated motion, from lifting to walking.

Correct Answer: A

Rationale: Pronation (palm down) and supination (palm up) are unique to the upper limbs, enabled by the radius rotating over the ulna, a feature absent in the lower limbs due to fixed tibia-fibula alignment. Flexion/extension (e.g., knee bending) and adduction/abduction (e.g., leg spreading) occur in both upper and lower limbs. Lateral/medial rotation happens at the hip and shoulder, not distinguishing them. Pronation and supination are the correct answer, as they're exclusive to forearm anatomy, reflecting a key functional difference between upper and lower limb mobility critical for tasks like turning a doorknob.

Correct Answer: B

Rationale: The calcaneal (Achilles) tendon connects the gastrocnemius and soleus to the calcaneus. A slight tear from training is a muscle strain, an overstretching or tearing of muscle or tendon, treated with P.R.I.C.E. (protection, rest, ice, compression, elevation) and anti-inflammatories. A sprain involves ligaments, not tendons. Repetitive strain injuries result from overuse, not a single tear. Tendon strain isn't a standard term strains encompass tendon injuries. Muscle strain is the correct answer, as it fits the Achilles injury and treatment, common in runners.

Correct Answer: C

Rationale: Ligaments are tough, elastic bands connecting bone to bone, stabilizing joints like the knee's ACL linking femur to tibia. This limits excessive movement, maintaining skeletal integrity. Cartilage-to-bone connections occur via other tissues, not ligaments directly, as cartilage cushions, not links. Muscle-to-bone attachment is tendons' job, pulling bones for motion. Tendons-to-muscles isn't accurate tendons extend from muscle to bone, not connecting to other tendons. Ligaments' bone-to-bone role distinguishes them, passively restricting joint range while allowing flexibility, unlike tendons' active force transmission or cartilage's shock absorption. This structural specificity ensures joint stability across the body, vital for posture and movement, setting ligaments apart in the musculoskeletal framework.

Correct Answer: D

Rationale: The muscular system accounts for about 50% of body weight, primarily from skeletal muscles, with smooth and cardiac adding less mass. This reflects their extensive presence over 600 muscles supporting movement and structure. Twenty percent is too low, ignoring skeletal bulk. Forty percent is close but underestimates, per anatomical data. Seventy percent overstates, leaving little for bones, organs, and fat. Fifty percent aligns with standard physiology, emphasizing muscles' role in force generation and mass, balancing the body's composition, distinct from lower or higher guesses misaligned with muscle distribution.