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WorksheetsExercise Physiology and Anatomy Quiz
Total questions: 91
Worksheet time: 46mins
According to the 'Size Principle,' which motor units are recruited first?
Large, high-threshold units
Small, low-threshold units
Intermediate units
Fast-fatigable units
How is 'Rate Coding' defined in neuromuscular physiology?
The number of muscle fibers per neuron
The speed of neural conduction
The frequency of motor unit firing
The thickness of the myelin sheath
Which muscle fiber type is characterized by the highest contraction velocity?
Type I
Type IIa
Type IIx
Type III
What happens to force production as motor unit firing frequency increases?
It decreases
It remains constant
It increases (Summation)
It fluctuates randomly
Which fiber type has the greatest resistance to fatigue?
Type IIx
Type IIa
Type I
Type IIb
Which fiber type is most likely to be recruited during a maximal vertical jump?
Type I only
Type IIx only
Both Type I and Type II
None of the above
Which characteristic is most associated with Type I muscle fibers?
High glycolytic capacity
High oxidative capacity
High peak power
Low myoglobin levels
What determines the muscle fiber type of a specific motor unit?
The load applied
The alpha motor neuron
The blood flow
The joint angle
In the context of jumping, higher rate coding primarily assists in:
Increasing fatiguability
Increasing rate of force development
Decreasing muscle tension
Improving flexibility
What is a 'Motor Unit'?
A single muscle fiber
A group of muscles
A motor neuron and all fibers it innervates
A bundle of nerves
Which fiber type has a high threshold of excitation?
Type I
Type IIx
Slow-twitch
Small motor units
As jump intensity increases from submaximal to maximal, recruitment proceeds:
From Type II to Type I
From Type I to Type II
Simultaneously
Randomly
Which protein gives Type I fibers their red appearance?
Hemoglobin
Myoglobin
Actin
Myosin
What is the primary cause of fatigue in Type IIx fibers during brief, high-intensity exercise?
Oxygen depletion
Glycogen depletion
Accumulation of metabolic byproducts
Dehydration
Which fiber type possesses the highest mitochondrial density?
Type IIx
Type IIa
Type I
Type IIb
What is the joint action at the ankle during the power phase of a jump?
Dorsiflexion
Plantarflexion
Inversion
Eversion
Which muscle is the primary agonist for hip extension during a vertical jump?
Rectus femoris
Biceps femoris
Gluteus maximus
Gastrocnemius
Which muscle group is responsible for extending the knee during takeoff?
Hamstrings
Quadriceps
Adductors
Abductors
The Gastrocnemius performs which two actions?
Knee extension / plantarflexion
Knee flexion / plantarflexion
Hip extension / knee flexion
Hip flexion / dorsiflexion
A vertical jump occurs primarily in which anatomical plane?
Frontal
Transverse
Sagittal
Horizontal
Which event directly allows myosin heads to bind to actin during excitation–contraction coupling in skeletal muscle?
Ca2+ binding to troponin C shifting tropomyosin
ATP binding to myosin causing power stroke
ADP release from myosin exposing actin sites
Pi binding to actin increasing affinity
In the cross-bridge cycle, what is the immediate effect of ATP binding to myosin?
Myosin detaches from actin
Myosin performs the power stroke
Myosin binds strongly to actin
Troponin releases Ca2+
Which structural protein primarily contributes to passive tension when a relaxed sarcomere is stretched?
Titin
Nebulin
Troponin I
Desmin
For two muscles producing the same joint torque, the muscle with greater physiological cross-sectional area (PCSA) generally has:
Greater maximal force capacity
Greater maximal shortening velocity
Lower metabolic cost at any force
Higher absolute tendon strain at a given force
Which change would most increase the rate of force development (RFD) in a ballistic contraction, assuming muscle size is unchanged?
Higher motor unit firing rates
Lower motor unit recruitment thresholds
Lower tendon stiffness
Lower Ca2+ sensitivity of troponin
Compared with a parallel-fiber muscle of equal volume, a highly pennate muscle typically has:
Higher maximal force and lower maximal shortening velocity
Lower maximal force and higher maximal shortening velocity
Higher maximal force and higher maximal shortening velocity
Lower maximal force and lower maximal shortening velocity
If sarcomere length is increased beyond optimal on the descending limb, maximal isometric force decreases primarily because:
Myosin ATPase activity slows
Actin–myosin overlap decreases
Titin stiffness decreases
Motor neuron firing rate decreases
The 'toe region' of a tendon stress–strain curve primarily reflects:
Uncrimping and alignment of collagen fibers
Irreversible microfailure of collagen
Maximum stiffness of aligned collagen
Viscous damping due to fluid flow only
Young’s modulus (stiffness) is best described as the:
Slope of the stress–strain curve in the linear elastic region
Area under the stress–strain curve to failure
Stress at the yield point
Strain at ultimate tensile strength
The yield point on a ligament stress–strain curve indicates the onset of:
Permanent (plastic) deformation
The toe region
Maximum elastic recoil
Zero strain
Viscoelastic 'creep' refers to:
Increasing strain over time under constant stress
Decreasing stress over time under constant strain
A sudden increase in stiffness at high strain rates
Elastic rebound after unloading
Stress relaxation refers to:
Decreasing stress over time under constant strain
Increasing strain over time under constant stress
Increasing stiffness with repeated loading
A reduction in ultimate tensile strength
Hysteresis in a loading–unloading cycle indicates:
Energy loss as heat (area between loading and unloading curves)
Increased energy storage
Higher Young’s modulus
No dependence on loading rate
At higher strain rates, tendons and ligaments generally become:
Stiffer and less compliant
More compliant and less stiff
Weaker but more compliant
Unaffected due to purely elastic behavior
Compared with ligaments, tendons typically have a higher proportion of:
Type I collagen aligned in the direction of force transmission
Type II collagen for compressive load tolerance
Elastin arranged randomly
Ground substance that dominates tensile behavior
Ultimate tensile strength (UTS) is the:
Maximum stress reached on the stress–strain curve before failure
Stress where the toe region ends
Stress at which plastic deformation begins
Strain at which stiffness is maximal
In Henneman’s size principle, recruitment order is primarily determined by:
Motor neuron size and excitability (input resistance)
Muscle fiber length
Joint angle at onset
Tendon stiffness
Rate coding contributes to force production primarily by:
Temporal summation leading to unfused/fused tetanus
Increasing the number of recruited motor units
Increasing sarcomere length
Increasing muscle temperature
Compared with low-threshold motor units, high-threshold motor units generally have:
Higher recruitment thresholds and faster, more forceful twitch characteristics
Lower recruitment thresholds and slower twitch characteristics
Lower firing rates at a given force
Greater fatigue resistance
As contraction intensity increases toward maximal, the relative contribution typically shifts toward:
More motor unit recruitment early, then greater reliance on rate coding to further increase force
Less recruitment and less rate coding
Only synchronization with no firing rate changes
Only reflex activity with no voluntary drive
During fatigue at a constant force output, the CNS typically compensates by:
Increasing neural drive: higher firing rates and/or additional motor unit recruitment
Decreasing recruitment to conserve ATP
Reducing antagonist co-contraction only
Eliminating rate coding to prevent tetanus
In a ballistic movement (e.g., maximal jump), the earliest phase of force rise is most strongly associated with:
Initial motor unit discharge rate and recruitment speed
Mitochondrial density
Capillary-to-fiber ratio
Slow-twitch fiber predominance
During high-intensity exercise, what is the primary immediate buffer of ATP concentration in skeletal muscle?
Mitochondrial oxidative phosphorylation
Phosphocreatine via the creatine kinase reaction
Anaerobic glycolysis via lactate dehydrogenase
Hepatic gluconeogenesis
Which step of glycolysis is considered the major rate-limiting (committed) step in skeletal muscle during exercise?
Glucose-6-phosphate to fructose-6-phosphate
Fructose-6-phosphate to fructose-1,6-bisphosphate (PFK-1)
1,3-bisphosphoglycerate to 3-phosphoglycerate
Phosphoenolpyruvate to pyruvate
In the creatine kinase reaction (PCr + ADP + H+ ↔ Cr + ATP), an accumulation of H+ during intense exercise tends to shift the equilibrium in which direction?
Toward ATP production
Toward PCr resynthesis
No effect; H+ is not involved
Toward Cr + ADP
Using contemporary P/O ratios (NADH ≈ 2.5 ATP, FADH2 ≈ 1.5 ATP), the net ATP yield from complete oxidation of palmitate (C16:0) is closest to:
84 ATP
96 ATP
106 ATP
129 ATP
Which pair of reactions in glycolysis produces ATP directly via substrate-level phosphorylation?
Hexokinase and phosphoglucose isomerase
PFK-1 and aldolase
Phosphoglycerate kinase and pyruvate kinase
Glyceraldehyde-3-phosphate dehydrogenase and enolase
What is the single best explanation for why RER can exceed 1.0 during severe exercise?
Fat oxidation produces more CO2 than O2 consumed
Increased protein oxidation elevates CO2
Bicarbonate buffering of H+ generates additional CO2 independent of mitochondrial oxidation
O2 uptake is capped, forcing anaerobic CO2 release from lactate
The lactate produced in fast-twitch fibers is best described as:
A metabolic dead-end that must be excreted
A substrate that can be oxidized in other tissues and fibers
A toxin that directly inhibits actin-myosin binding
The primary cause of delayed-onset muscle soreness
A decrease in mitochondrial coupling efficiency during exercise most directly implies:
Less O2 consumption for the same ATP production
More ATP produced per NADH oxidized
More O2 consumption for the same ATP production due to proton leak
Complete inhibition of the TCA cycle
Which regulatory change most directly increases carbohydrate oxidation at a given workload during acute exercise?
Inhibition of pyruvate dehydrogenase (PDH)
Activation (dephosphorylation) of PDH
Inhibition of glycogen phosphorylase
Inhibition of PFK-1 by AMP
When oxygen delivery is suddenly reduced at a fixed workload, which variable typically changes first to maintain ATP resynthesis?
Mitochondrial density
Rate of ATP utilization
Contribution from anaerobic glycolysis
Hemoglobin concentration
Skeletal muscle GLUT4 translocation is increased mainly via:
Insulin signaling only (PI3K-Akt)
Contraction-mediated pathways involving AMPK and Ca2+ signaling
Cortisol receptor activation
Thyroid hormone receptor activation
Which hormone is most directly responsible for counterregulation of falling blood glucose during prolonged exercise (especially in individuals with type 1 diabetes)?
Leptin
Glucagon
Calcitonin
Aldosterone
IL-6 released from contracting skeletal muscle is best characterized as:
An adipokine that suppresses lipolysis
A myokine that can increase hepatic glucose output and lipolysis
A neurotransmitter that reduces ventilation
A steroid hormone from the adrenal cortex
The baroreflex 'resetting' observed during exercise is most consistent with:
Complete inactivation of baroreceptors
A shift of the operating point to defend a higher arterial pressure
Loss of sympathetic control of HR
Permanent reduction in vascular resistance post-exercise
Cortisol’s acute metabolic role during prolonged exercise is best described as:
Promoting glycogen synthesis in muscle
Supporting gluconeogenesis and mobilization of amino acids and fats
Blocking hepatic glucose output
Directly increasing muscle protein synthesis
Which second messenger is most directly increased by beta-adrenergic receptor activation in muscle and liver?
cAMP
IP3
cGMP
NADPH
According to the Fick principle, whole-body VO2 equals:
HR × SV
Q × (CaO2 − CvO2)
MAP ÷ TPR
SV ÷ HR
At maximal exercise, the largest contributor to increased cardiac output in untrained individuals is typically:
Increased stroke volume only
Increased heart rate only
Equal increases in HR and SV across all intensities
Reduced preload
The primary mechanism for increased venous return during rhythmic dynamic exercise is:
Reduced skeletal muscle pump
Increased blood viscosity
Skeletal muscle pump and respiratory pump
Decreased sympathetic venoconstriction
Functional sympatholysis refers to:
Sympathetic activation causing vasodilation in skin
Local metabolic vasodilation blunting sympathetic vasoconstriction in active muscle
Parasympathetic dominance at high intensities
Complete loss of vasomotor tone after exercise
Which local factor is most directly associated with exercise-induced vasodilation in active skeletal muscle?
Endothelin-1
Adenosine and increased K+ / H+ / CO2
Increased angiotensin II
Decreased nitric oxide
During steady-state submaximal exercise, mean arterial pressure (MAP) typically:
Decreases substantially due to vasodilation
Remains unchanged because Q and TPR do not change
Increases modestly because Q rises more than the fall in TPR
Falls to the level of diastolic pressure
The increase in a-vO2 difference during incremental exercise is primarily due to:
Lower arterial O2 content
Greater O2 extraction by working muscles (lower venous O2 content)
Reduced hemoglobin concentration
Reduced capillary density
A key reason stroke volume can plateau at higher intensities is:
Increased preload time due to longer diastole
Reduced venous return from muscle pump
Reduced ventricular filling time from high HR (shortened diastole)
Elimination of sympathetic inotropy
With upright dynamic exercise, cutaneous blood flow generally:
Falls continuously as intensity increases
Increases early, then may plateau or fall at very high intensities
Is unchanged because skin is not active tissue
Always exceeds muscle blood flow
The 'crossover concept' in exercise metabolism refers to:
Switching from aerobic to anaerobic metabolism at VO2max
A shift from predominantly fat oxidation to predominantly carbohydrate oxidation with increasing intensity
The point at which lactate equals pyruvate concentration
The transition from type I to type II fiber recruitment only
At the same absolute workload, endurance-trained individuals generally exhibit a lower RER because of:
Higher reliance on amino acid oxidation
Greater fat oxidation and reduced carbohydrate reliance
Lower mitochondrial content
Reduced capillary density
Glycogen depletion during prolonged exercise most strongly contributes to fatigue by:
Blocking lipolysis in adipose tissue
Reducing the rate of carbohydrate-derived ATP resynthesis at higher intensities
Increasing blood pH
Preventing oxygen from binding hemoglobin
Which scenario most increases net lactate appearance in blood during incremental exercise?
Increased lactate clearance with unchanged production
Unchanged production with increased clearance
Production rises faster than clearance capacity
Clearance rises faster than production
The fast component of EPOC is most closely related to:
Resynthesis of phosphocreatine and re-oxygenation of myoglobin/hemoglobin
Muscle fiber hypertrophy
Long-term increases in mitochondrial enzymes
Glycogen supercompensation
The 'fatmax' intensity is best defined as the exercise intensity at which:
Total fat mass decreases fastest
Absolute rate of fat oxidation is maximal
RER equals 0.85 exactly
Lactate begins to accumulate
During prolonged endurance exercise, a rise in circulating free fatty acids (FFA) typically causes:
Increased PDH activity and carbohydrate oxidation
Decreased carbohydrate oxidation via Randle cycle mechanisms
Complete inhibition of beta-oxidation
Immediate depletion of liver glycogen
Which metabolic pathway is primarily responsible for producing glucose from lactate during recovery?
Glycogenolysis
Cori cycle (hepatic gluconeogenesis)
Pentose phosphate pathway
Ketogenesis
Ammonia accumulation during high-intensity exercise is most directly linked to:
Deamination during amino acid transamination only
ATP breakdown and AMP deamination (purine nucleotide cycle)
Beta-oxidation of fatty acids
Lactate oxidation in mitochondria
The carnitine shuttle is essential for:
Transport of glucose into muscle fibers
Transport of long-chain fatty acyl-CoA into the mitochondrial matrix
Export of lactate from muscle to blood
Transport of pyruvate into mitochondria
Which signaling kinase is a key energy sensor activated by increases in AMP/ATP ratio during exercise?
mTORC1
AMPK
JNK
PKA
A primary downstream transcriptional coactivator associated with endurance training-induced mitochondrial biogenesis is:
PGC-1α
NFAT
p53 (tumor suppressor) only
HIF-2α
Mechanical tension from resistance exercise most directly activates protein synthesis through:
AMPK inhibition of mTORC1
mTORC1 activation via mechanosensitive pathways (e.g., phosphatidic acid)
Inhibition of insulin receptor substrate
Activation of glycogen phosphorylase
The acute rise in epinephrine during exercise primarily promotes:
Increased insulin secretion from pancreatic beta cells
Increased muscle glucose uptake independent of GLUT4
Hepatic glycogenolysis and adipose lipolysis
Suppression of heart rate
The primary extracellular buffer system for H+ during exercise is:
Phosphate buffer
Hemoglobin buffer
Bicarbonate buffer
Protein buffer in muscle only
During heavy exercise, the largest immediate source of metabolic acidosis in muscle is best attributed to:
Lactate directly releasing H+
ATP hydrolysis and associated reactions increasing H+ availability
Ketone body production
Urea cycle activation
A progressive rise in core temperature during exercise in the heat is most likely to cause:
Decreased skin blood flow
Increased sweating and cutaneous vasodilation
Increased plasma volume
Reduced heart rate at fixed workload
Cardiovascular drift during prolonged exercise in the heat is characterized by:
Decreasing HR and increasing SV
Increasing HR and decreasing SV at a constant workload
Increasing SV and Q with stable HR
No change in HR or SV
Exercise-associated hyponatremia is most commonly caused by:
Too little sweating
Excessive intake of hypotonic fluid relative to sodium loss
Too much sodium intake
High altitude exposure
During repeated high-intensity contractions, extracellular K+ can rise. The immediate functional consequence most associated with this is:
Improved membrane excitability indefinitely
Reduced action potential propagation and force production
Increased myosin ATPase activity
Increased calcium sensitivity of troponin
The most direct mechanism for maintaining plasma osmolality during dehydration is increased secretion of:
Insulin
Antidiuretic hormone (vasopressin)
Calcitonin
Erythropoietin
Metabolic heat production during exercise is primarily determined by:
Mechanical efficiency and total metabolic rate
Only ambient temperature
Only sweat rate
Only body fat percentage
If ventilation increases disproportionately to VO2 during incremental exercise, this most directly reflects:
A reduced need to eliminate CO2
Increased buffering of H+ producing additional CO2 and stimulating ventilation
A sudden drop in arterial O2 content at low workloads
A decrease in chemoreceptor sensitivity
The primary immediate defense against hypoglycemia during prolonged exercise in healthy individuals is:
Increased insulin secretion
Reduced hepatic glucose output
Increased hepatic glucose production via glucagon and catecholamines
Increased renal glucose excretion
