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Physiology & Rehabilitation MCQs

Practice Set 10 of 26

This practice set contains high-yield board review questions covering key concepts in Physiology & Rehabilitation. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 181

Topic: Physiology & Rehabilitation

A 28-year-old weightlifter feels a sudden 'pop' in his axilla while performing a heavy bench press. He presents with extensive ecchymosis and loss of the anterior axillary fold. If a complete rupture of the pectoralis major occurred, which portion is typically the first to fail due to maximal eccentric stretch?

. Clavicular head at the muscle belly
. Sternal head at the humeral insertion
. Clavicular head at the humeral insertion
. Sternal head at the costochondral junction
. Abdominal head at the sternum

Correct Answer & Explanation

. Clavicular head at the muscle belly

Explanation

Pectoralis major ruptures commonly occur at the humeral insertion during eccentric contraction (e.g., bench pressing). The sternal head inserts deep and proximal to the clavicular head, placing it under maximal tension when the arm is extended and externally rotated, causing it to tear first.

Question 182

Topic: Physiology & Rehabilitation

Which type of muscle contraction generates the highest peak force and is most commonly associated with muscle strain injuries?

. Isometric contraction
. Concentric isotonic contraction
. Eccentric contraction
. Isokinetic contraction
. Tetanic contraction

Correct Answer & Explanation

. Isometric contraction

Explanation

Eccentric contractions, where the muscle lengthens while contracting against a load, generate the highest peak forces. Due to these high forces and mechanical tissue disruption, eccentric loading is the primary mechanism for muscle strains.

Question 183

Topic: Physiology & Rehabilitation

During the swing phase and normal walking, the primary mechanism of lubrication in the human hip joint, where the articular surfaces are separated by a continuous dynamic fluid film, is best described as:

. Boundary lubrication
. Elastohydrodynamic lubrication
. Weeping lubrication
. Squeeze-film lubrication
. Hydrostatic lubrication

Correct Answer & Explanation

. Boundary lubrication

Explanation

Elastohydrodynamic lubrication is a type of fluid-film lubrication occurring during joint motion, where the pressure of the fluid film physically separates and elastically deforms the opposing articular surfaces, minimizing wear.

Question 184

Topic: Physiology & Rehabilitation

During the single-leg stance phase of gait, using a cane in the contralateral hand reduces the hip joint reaction force primarily by:

. Increasing the abductor muscle moment arm
. Decreasing the body weight moment arm
. Generating a counter-moment that reduces the required abductor muscle force
. Shifting the center of gravity laterally over the stance leg
. Increasing the joint contact area in the acetabulum

Correct Answer & Explanation

. Increasing the abductor muscle moment arm

Explanation

A cane in the contralateral hand provides an upward force at a large distance (long moment arm) from the hip center. This counter-moment significantly reduces the force required by the hip abductors, thereby reducing the total joint reaction force.

Question 185

Topic: Physiology & Rehabilitation

During normal gait, the peak joint reaction forces acting on the hip joint occur during which phase of the gait cycle?

. Initial contact (heel strike)
. Mid-stance
. Terminal stance (heel off)
. Pre-swing (toe off)
. Mid-swing

Correct Answer & Explanation

. Initial contact (heel strike)

Explanation

Peak joint reaction forces across the hip often reach 2.5 to 3 times body weight and occur primarily during the mid-stance phase of gait. This is driven largely by the strong contraction of the hip abductor muscles necessary to stabilize the pelvis.

Question 186

Topic: Physiology & Rehabilitation

Which of the following characteristics best describes Type I (slow-twitch) skeletal muscle fibers?

. High glycolytic capacity and rapid fatigue
. Low myoglobin content and fast twitch speed
. High oxidative capacity and resistance to fatigue
. Low mitochondria density and high force production
. Anaerobic metabolism and high glycogen stores

Correct Answer & Explanation

. High glycolytic capacity and rapid fatigue

Explanation

Type I muscle fibers are 'slow-twitch' fibers that rely on aerobic metabolism. They are rich in mitochondria and myoglobin, granting them high oxidative capacity and significant resistance to fatigue.

Question 187

Topic: Physiology & Rehabilitation

During the normal human gait cycle, which muscle group undergoes an eccentric contraction during the initial contact (heel strike) to loading response phase to prevent foot slap?

. Plantar flexors
. Dorsiflexors
. Quadriceps
. Hamstrings
. Hip abductors

Correct Answer & Explanation

. Plantar flexors

Explanation

The ankle dorsiflexors, primarily the tibialis anterior, contract eccentrically after heel strike to lower the foot smoothly to the ground. A failure of this mechanism results in an audible foot slap.

Question 188

Topic: Physiology & Rehabilitation

A 45-year-old female presents with persistent lateral hip pain and a Trendelenburg gait after a fall. MRI reveals an isolated avulsion of the gluteus medius tendon. Which aspect of the greater trochanter is the primary footprint for the gluteus medius?

. Anterior facet
. Superoposterior and lateral facets
. Posteromedial facet
. Lesser trochanter
. Intertrochanteric crest

Correct Answer & Explanation

. Anterior facet

Explanation

The gluteus medius inserts on the superoposterior and lateral facets of the greater trochanter. The gluteus minimus primarily inserts on the anterior facet.

Question 189

Topic: Physiology & Rehabilitation

The popliteus muscle acts to unlock the knee from a fully extended position. What is its specific action on the tibia during early knee flexion in an open kinetic chain?

. External rotation of the tibia
. Internal rotation of the tibia
. Anterior translation of the tibia
. Varus angulation of the tibia
. Valgus angulation of the tibia

Correct Answer & Explanation

. External rotation of the tibia

Explanation

In an open kinetic chain, the popliteus internally rotates the tibia on the femur to unlock the extended knee, initiating flexion. In a closed kinetic chain, it externally rotates the femur on the fixed tibia.

Question 190

Topic: Physiology & Rehabilitation

A 30-year-old male strikes his head on the bottom of a pool while diving. He sustains a C5 flexion teardrop fracture. Examination shows bilateral complete loss of motor function, pain, and temperature sensation below the injury, but proprioception and vibratory sense remain intact. What is his diagnosis and expected prognosis for motor recovery?

. Central cord syndrome; good prognosis
. Central cord syndrome; poor prognosis
. Anterior cord syndrome; good prognosis
. Anterior cord syndrome; poor prognosis

Correct Answer & Explanation

. Central cord syndrome; good prognosis

Explanation

The patient exhibits Anterior Cord Syndrome, characterized by loss of the anterior spinothalamic and corticospinal tracts with preservation of the dorsal columns. This syndrome carries the worst prognosis among incomplete spinal cord injuries, with very low rates of motor recovery.

Question 191

Topic: Physiology & Rehabilitation

Which of the following statements regarding the role of calcium in muscle contraction is FALSE?

. Calcium is stored in the sarcoplasmic reticulum.
. Calcium binds to troponin C, initiating the conformational change.
. Calcium release into the sarcoplasm is triggered by an action potential.
. Calcium directly binds to myosin heads to facilitate cross-bridge formation.
. ATP is required for calcium reuptake into the sarcoplasmic reticulum.

Correct Answer & Explanation

. Calcium is stored in the sarcoplasmic reticulum.

Explanation

Calcium does not directly bind to myosin heads to facilitate cross-bridge formation. Instead, calcium binds to troponin C, which then causes a conformational change in the troponin-tropomyosin complex, exposing the myosin-binding sites on the actin filaments. Myosin heads then bind to actin, initiating the power stroke. All other statements are correct regarding the role of calcium in excitation-contraction coupling.

Question 192

Topic: Physiology & Rehabilitation

A competitive long-distance marathon runner sustains an acute hamstring strain. Biopsies of the uninjured hamstrings in this athlete would reveal a predominance of muscle fibers characterized by which of the following physiologic profiles?

. High glycogen content, rapid fatigue, and extremely high myosin ATPase activity
. Low myoglobin content, preferential anaerobic metabolism, and large fiber cross-sectional diameter
. High mitochondrial density, preferential aerobic metabolism, and slow contraction velocity
. Fast twitch velocity, high oxidative capacity, and low surrounding capillary density
. Rapid calcium release from the sarcoplasmic reticulum coupled with low resistance to fatigue

Correct Answer & Explanation

. High glycogen content, rapid fatigue, and extremely high myosin ATPase activity

Explanation

Endurance athletes like marathon runners have a predominance of Type I (slow-twitch) muscle fibers in their continuously acting skeletal muscles. Type I fibers are uniquely adapted for prolonged, sustained contractions. They are characterized by a high density of mitochondria, high myoglobin content (giving them a 'red' appearance), abundant capillary supply, preferential aerobic (oxidative) metabolism, and slow contraction speeds that resist fatigue.

Question 193

Topic: Physiology & Rehabilitation

During the normal human gait cycle, the peak force across the hip joint can reach up to 2.5 to 3 times body weight. During which specific phase of the gait cycle does the maximum joint reaction force across the hip occur?

. Heel strike (Initial contact)
. Mid-stance
. Terminal stance (Heel off)
. Initial swing
. Terminal swing

Correct Answer & Explanation

. Heel strike (Initial contact)

Explanation

The maximum joint reaction force at the hip occurs during the late stance phase, specifically terminal stance (heel off). During this phase, the hip abductor muscles contract forcefully to stabilize the pelvis as the body's center of mass accelerates forward over the supporting limb, creating the highest compressive forces across the joint articulation.

Question 194

Topic: Physiology & Rehabilitation

During a prolonged, low-intensity orthopedic rehabilitation exercise (such as endurance cycling), which muscle fiber type is predominantly recruited, and what is its primary metabolic pathway for energy production?

. Type I fibers; Anaerobic glycolysis
. Type I fibers; Oxidative phosphorylation
. Type IIa fibers; Creatine phosphate
. Type IIb fibers; Anaerobic glycolysis
. Type IIb fibers; Oxidative phosphorylation

Correct Answer & Explanation

. Type I fibers; Anaerobic glycolysis

Explanation

Type I muscle fibers are 'slow-twitch' fibers characterized by high endurance, abundant mitochondria, and high myoglobin content. They are fatigue-resistant and recruited primarily during prolonged, low-intensity activities. Their primary source of ATP is aerobic metabolism via oxidative phosphorylation. Conversely, Type IIb fibers are 'fast-twitch', fatigue quickly, and rely mainly on anaerobic glycolysis for rapid bursts of power.

Question 195

Topic: Physiology & Rehabilitation

During normal human gait on a level surface, sufficient knee flexion during the swing phase is critical for foot clearance. What is the approximate maximum degree of knee flexion achieved during normal level walking?

. 15 to 20 degrees
. 40 to 45 degrees
. 60 to 65 degrees
. 80 to 85 degrees
. 100 to 110 degrees

Correct Answer & Explanation

. 15 to 20 degrees

Explanation

During normal gait on level ground, the knee reaches its maximum flexion of approximately 60 to 65 degrees during the initial to mid-swing phase, which is required for adequate foot clearance. During the stance phase, maximum knee flexion is much smaller, roughly 15 to 20 degrees (loading response). Ascending and descending stairs require greater flexion (up to 90-105 degrees).

Question 196

Topic: Physiology & Rehabilitation

A patient is undergoing physical therapy 12 weeks following operative repair of an Achilles tendon rupture. The therapist incorporates exercises in which the gastrocnemius-soleus complex lengthens while actively generating tension. This specific type of muscle contraction is classified as:

. Isometric
. Isokinetic
. Concentric
. Plyometric
. Eccentric

Correct Answer & Explanation

. Isometric

Explanation

An eccentric contraction occurs when a muscle develops tension while it is lengthening. This type of contraction is essential for energy absorption, deceleration, and tendon remodeling during rehabilitation. In contrast, a concentric contraction involves muscle shortening under tension, and an isometric contraction involves generating tension without a change in muscle length.

Question 197

Topic: Physiology & Rehabilitation

A 5-year-old boy is brought to the orthopedic clinic due to delayed motor milestones, frequent falls, and difficulty climbing stairs. The physical examination is notable for enlarged, firm calf muscles and a positive Gowers' sign. Serum creatine kinase levels are markedly elevated. A genetic mutation is identified in a gene located on chromosome Xp21. The mutated protein is normally responsible for which of the following cellular functions?

. Autosomal dominant; anchors the actin cytoskeleton to the extracellular matrix
. Autosomal recessive; regulates calcium release from the sarcoplasmic reticulum
. X-linked recessive; regulates calcium release from the sarcoplasmic reticulum
. Mitochondrial; produces ATP required for muscle contraction
. X-linked recessive; anchors the actin cytoskeleton to the extracellular matrix

Correct Answer & Explanation

. Autosomal dominant; anchors the actin cytoskeleton to the extracellular matrix

Explanation

The clinical presentation describes Duchenne Muscular Dystrophy (DMD). DMD is an X-linked recessive disorder caused by nonsense or frameshift mutations in the DMD gene, leading to absent or severely truncated dystrophin protein. Dystrophin serves a critical structural role by linking the intracellular actin cytoskeleton of the muscle fiber to the extracellular matrix through the dystrophin-glycoprotein complex located at the sarcolemma, preventing membrane damage during muscle contraction.

Question 198

Topic: Physiology & Rehabilitation

During the rehabilitation of an anterior cruciate ligament reconstruction, closed kinetic chain exercises frequently emphasize eccentric muscle contractions. At the cellular level, what occurs within the skeletal muscle fibers during a purely eccentric contraction?

. They shorten while generating maximum tension.
. They actively lengthen while generating tension.
. They maintain a constant length while generating tension.
. They exhibit a decrease in tension as shortening velocity increases.
. The I bands shorten while the A bands remain the same length.

Correct Answer & Explanation

. They shorten while generating maximum tension.

Explanation

During an eccentric contraction, the muscle actively generates tension while the overall muscle-tendon unit is lengthening. This happens when the external force applied to the muscle exceeds the internal force generated by the cross-bridges. Eccentric contractions are capable of generating the highest amount of force compared to isometric or concentric contractions, but they are also most strongly associated with ultrastructural muscle damage and delayed-onset muscle soreness (DOMS). Concentric contraction involves shortening, while isometric involves no change in length.

Question 199

Topic: Physiology & Rehabilitation

Skeletal muscle fibers are broadly classified based on their metabolic properties and contractile speeds. Compared to Type IIb fibers, Type I muscle fibers are characterized by which of the following?

. Higher concentration of glycogen stores
. Faster rate of contraction and relaxation
. Higher susceptibility to fatigue
. Metabolism is predominantly oxidative
. Rely primarily on anaerobic glycolysis

Correct Answer & Explanation

. Higher concentration of glycogen stores

Explanation

Type I muscle fibers (slow-twitch) are specialized for endurance and continuous, low-intensity contraction. They have a rich capillary supply, high myoglobin content, and a high density of mitochondria, allowing them to rely predominantly on oxidative (aerobic) metabolism. They are highly fatigue-resistant. In contrast, Type IIb fibers (fast-twitch) are optimized for short, powerful bursts. They have high glycogen content, fewer mitochondria, rely heavily on anaerobic glycolysis, and fatigue rapidly.

Question 200

Topic: Physiology & Rehabilitation

A 24-year-old recreational soccer player sustains an acute anterior cruciate ligament (ACL) rupture. During a subsequent gait analysis assessment, which of the following kinematic adaptations is most characteristic of a classic ACL-deficient 'quadriceps avoidance gait' during the stance phase?

. Increased peak knee flexion angle
. Decreased peak knee flexion to minimize anterior tibial translation
. Increased internal rotation of the tibia
. Excessive varus thrust during mid-stance
. Prolonged heel strike phase

Correct Answer & Explanation

. Decreased peak knee flexion to minimize anterior tibial translation

Explanation

Patients with an ACL-deficient knee often adopt a 'quadriceps avoidance gait' to dynamically stabilize the knee. Because contraction of the quadriceps pulls the tibia anteriorly, the patient unconsciously decreases peak knee flexion during the stance phase, relying more on hip extensors and hamstrings to prevent the tibia from subluxating anteriorly.

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