Increase in muscle size due to training is called

Correct Answer: C

Rationale: Hypertrophy is muscle size increase from training, as resistance stress thickens fibers via protein synthesis, enhancing strength and mass, like in weightlifting. Atrophy is size loss from inactivity, opposite to training's goal. Fatigue is temporary exhaustion, not size change. Hyperplasia, fiber number increase, is rare in humans, unlike hypertrophy's fiber growth. This adaptation reflects muscle's response to mechanical overload, distinct from shrinkage, energy depletion, or theoretical cell addition, central to exercise-induced development.

Correct Answer: D

Rationale: Biceps brachii flexes the elbow, bending the forearm toward the arm, while triceps brachii extends it, straightening it. Abduction and adduction involve lateral movement, not their primary elbow focus. Flexion-extension defines their antagonistic pair, distinct from side motions, key for arm bending and straightening.

Correct Answer: D

Rationale: Muscular dystrophy encompasses genetic disorders like Duchenne, progressively weakening muscles via protein defects, leading to loss of function. Sprains are ligament injuries. Fibromyalgia is pain without degeneration. Tendonitis inflames tendons. Muscular dystrophy's degenerative nature distinguishes it, impacting muscle integrity over time.

Correct Answer: B

Rationale: The acromion process is a bony projection on the scapula, forming the shoulder's highest point where it articulates with the clavicle at the acromioclavicular joint. This structure stabilizes the shoulder girdle and anchors muscles like the deltoid. The ilium, part of the pelvis, supports hip muscles, not shoulder features. The humerus, the upper arm bone, articulates with the scapula at the glenoid cavity, not bearing the acromion. The ulna, a forearm bone, connects to the humerus distally, unrelated to shoulder anatomy. The scapula's acromion is distinct, critical for shoulder movement and stability, unlike pelvic, arm, or forearm bones, aligning with its role in the musculoskeletal framework.

Correct Answer: C

Rationale: ATP (adenosine triphosphate) is the immediate energy source for muscle contraction, directly fueling myosin cross-bridge cycling by hydrolyzing to ADP and phosphate, releasing energy to pull actin filaments. Glucose, a fuel, must be metabolized via glycolysis or respiration to produce ATP, not an instant source. ADP, a product of ATP breakdown, needs rephosphorylation to become usable ATP. AMP, further down the energy chain, isn't a primary energy carrier. ATP's ready availability in muscle cells ensures instant contraction energy, distinguishing it from substrates requiring processing or depleted molecules, critical for rapid muscle action.