WorksheetsExercise Physiology Quiz
Total questions: 66
Worksheet time: 33mins
The primary immediate defense against hypoglycemia during prolonged exercise in healthy individuals is:
Increased renal glucose excretion
Increased insulin secretion
Increased glucose production via glucagon and catecholamines
Reduced hepatic glucose output
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 FFAs
Directly increasing muscle protein synthesis
Blocking hepatic glucose output
Which change would most increase the rate of force development (RFD) in a ballistic contraction, assuming muscle size is unchanged?
Lower Ca2+ sensitivity of troponin
Lower motor unit recruitment thresholds
Lower tendon stiffness
Higher motor unit firing rates
The Gastrocnemius performs which two actions?
Hip flexion / dorsiflexion
Knee extension / plantarflexion
Knee flexion / plantarflexion
Hip extension / knee flexion
Compared with ligaments, tendons typically have a higher proportion of:
Type II collagen for compressive load tolerance
Type I collagen aligned in the direction of force transmission
Ground substance that dominates tensile behavior
Elastin arranged randomly
As muscle contraction intensity increases toward maximal, the relative contribution typically shifts toward:
Only reflex activity with no voluntary drive
Only synchronization with no firing rate changes
More motor unit recruitment early, then greater reliance on rate coding to further increase force
Less recruitment and less rate coding
This hormone plays a role in minimizing the extent of water loss during heavy sweating and hard exercise:
Insulin
Antidiuretic hormone (ADH)
Erythropoietin
Calcitonin
The increase in a-vO2 difference during incremental exercise is primarily due to:
Reduced capillary density
Lower arterial O2 content
Reduced hemoglobin concentration
Greater O2 extraction by working muscles (lower venous O2 content)
Rate coding contributes to force production primarily by:
Increasing muscle temperature
Increasing sarcomere length
Temporal summation leading to unfused/fused tetanus
Increasing the number of recruited motor units
Viscoelastic 'creep' refers to:
Decreasing stress over time under constant strain
Increasing strain over time under constant stress
Elastic rebound after unloading
A sudden increase in stiffness at high strain rates
Compared with a parallel-fiber muscle of equal volume, a highly pennate muscle typically has:
Higher maximal force and higher maximal shortening velocity
Lower maximal force and higher maximal shortening velocity
Lower maximal force and lower maximal shortening velocity
Higher maximal force and lower maximal shortening velocity
A progressive rise in core temperature during exercise in the heat is most likely to cause:
Decreased skin blood flow
Reduced heart rate at fixed workload
Increased sweating and cutaneous vasodilation
Increased plasma volume
Which protein gives Type I fibers their red appearance?
Actin
Hemoglobin
Myosin
Myoglobin
Which muscle group is responsible for extending the knee during takeoff?
Abductors
Adductors
Hamstrings
Quadriceps
Which metabolic pathway is primarily responsible for producing glucose from lactate during recovery?
Pentose phosphate pathway
Cori cycle (hepatic gluconeogenesis)
Ketogenesis
Glycogenolysis
Which characteristic is most associated with Type I muscle fibers?
High glycolytic capacity
Low myoglobin levels
High peak power
High oxidative capacity
Ballistic and high power movements use what type of recruitment strategy?
Inhibit slow-twitch MU
Slow-twitch MU predominance
Recruit slow MU then fast MU
Recruit fast MU then slow MU
During steady-state submaximal exercise, mean arterial pressure (MAP) typically:
Falls to the level of diastolic pressure
Decreases substantially due to vasodilation
Increases modestly because systolic pressure rises significantly while diastolic pressure is stable or drops slightly.
Remains unchanged because cardiac output and total peripheral resistance do not change
Failure point is the:
Stress at which plastic deformation begins
Strain at which stiffness is maximal
Maximum stress reached on the stress–strain curve before failure
Stress where the toe region ends
If ventilation increases disproportionately to VO2 during incremental exercise, this most directly reflects:
A decrease in chemoreceptor sensitivity
Increased buffering of H+ producing additional CO2 and stimulating ventilation
A sudden drop in arterial O2 content at low workloads
A reduced need to eliminate CO2
In the cross-bridge cycle, what is the immediate effect of ATP binding to myosin?
Myosin binds strongly to actin
Myosin performs the power stroke
Troponin releases Ca2+
Myosin detaches from actin
Which event directly allows myosin heads to bind to actin during excitation–contraction coupling in skeletal muscle?
ATP binding to myosin causing power stroke
Ca2+ binding to troponin C shifting tropomyosin
ADP release from myosin exposing actin sites
Pi binding to actin increasing affinity
As jump intensity increases from submaximal to maximal, recruitment proceeds:
From Type II to Type I
Simultaneously
Randomly
From Type I to Type II
Which fiber type has the greatest resistance to fatigue?
Type IIa
Type IIx
Type IIb
Type I
Glycogen depletion during prolonged exercise most strongly contributes to fatigue by:
Blocking lipolysis in adipose tissue
Reducing muscle and live glycogen ability to resynthesize ATP
Preventing oxygen from binding hemoglobin
Increasing blood pH
The acute rise in epinephrine during exercise primarily promotes:
Suppression of heart rate
Increased insulin secretion from pancreatic beta cells
Hepatic glycogenolysis and adipose lipolysis
Increased muscle glucose uptake independent of GLUT4
Which hormone is most directly responsible for counter-regulation of falling blood glucose during prolonged exercise?
Leptin
Aldosterone
Glucagon
Calcitonin
Load relaxation refers to:
A reduction in ultimate tensile strength
Increasing strain over time under constant stress
Decreasing stress over time under constant strain
Increasing stiffness with repeated loading
The fast component of EPOC is most closely related to:
Long-term increases in mitochondrial enzymes
Muscle fiber hypertrophy
Resynthesis of phosphocreatine and re-oxygenation of myoglobin/hemoglobin
Glycogen supercompensation
For two muscles producing the same joint torque, the muscle with greater physiological cross-sectional area (PCSA) generally has what characteristic?
Lower metabolic cost at any force
Higher absolute tendon strain at a given force
Greater maximal shortening velocity
Greater maximal force capacity
What chemical changes are associated with vasodialation in active skeletal muscle during exercise?
Increased H+ & CO2
Decreased nitric oxide
Endothelin-1
Increased pH
Exercise-associated hyponatremia is most commonly caused by what?
Too little sweating
Excessive intake of hypotonic fluid relative to sodium loss
High altitude exposure
Too much sodium intake
A decrease in mitochondrial coupling efficiency during exercise most directly implies what?
Less O2 consumption for the same ATP production
Complete inhibition of the TCA cycle
More O2 consumption for the same ATP production due to proton leak
More ATP produced per NADH oxidized
What is the primary cause of fatigue in Type IIx fibers during brief, high-intensity exercise?
Dehydration
Oxygen depletion
Glycogen depletion
Accumulation of metabolic byproducts
What happens to force production as motor unit firing frequency increases?
It fluctuates randomly
It decreases
It increases (Summation)
It remains constant
Which fiber type is most likely to be recruited during a 1-RM?
Type IIx only
All fibers
Type 1 only
Type IIa only
Compared with low-threshold motor units, high-threshold motor units generally have what characteristics?
Lower recruitment thresholds and slower twitch characteristics
Higher recruitment thresholds and faster, more forceful twitch characteristics
Greater fatigue resistance
Lower firing rates at a given force
If sarcomere length is increased beyond optimal on the descending limb, maximal isometric force decreases primarily because of what?
Motor neuron firing rate decreases
Titin stiffness decreases
Myosin ATPase activity slows
Actin–myosin overlap decreases
How is 'Rate Coding' defined in neuromuscular physiology?
The speed of neural conduction
The frequency of motor unit firing
The number of muscle fibers per neuron
The thickness of the myelin sheath
At the same absolute workload, endurance-trained individuals generally exhibit a lower RER because of:
Reduced capillary density
Greater fat oxidation and reduced carbohydrate reliance
Higher reliance on amino acid oxidation
Lower mitochondrial content
According to the Fick principle, whole-body VO2 equals:
HR × SV
Q × (CaO2 − CvO2)
MAP ÷ TPR
SV ÷ HR
The 'crossover concept' in exercise metabolism refers to:
Switching from aerobic to anaerobic metabolism at VO2max
The transition from type I to type II fiber recruitment only
A shift from predominantly fat oxidation to predominantly carbohydrate oxidation with increasing intensity
The point at which lactate equals pyruvate concentration
Lactate threshold is typically expressed as:
The percentage of maximal oxygen uptake at the intensity or workload it occurs.
Individuals maximal oxygen uptake
Plateau in the rise in oxygen uptake during exercise
The workload when RER is >1.0
A key reason stroke volume can plateau at higher intensities is:
Increased preload time due to longer diastole
Reduced ventricular filling time from high HR (shortened diastole)
Reduced venous return from muscle pump
Elimination of sympathetic inotropy
Hysteresis in a loading–unloading cycle indicates:
Energy loss as heat (area between loading and unloading curves)
No dependence on loading rate
Higher Young’s modulus
Increased energy storage
The primary mechanism for increased venous return during rhythmic dynamic exercise is:
Reduced skeletal muscle pump
Decreased sympathetic venoconstriction
Increased blood viscosity
Skeletal muscle pump and respiratory pump
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 Cr + ADP
Toward ATP production
Toward PCr resynthesis
No effect; H+ is not involved
Total energy yield of ATP from oxidation of carbohydrate can be:
32 ATP
5-6 ATP
22 -24 ATP
3 ATP
What is the single best explanation for why RER can exceed 1.0 during severe exercise?
Increased protein oxidation elevates CO2
O2 uptake is capped, forcing anaerobic CO2 release from lactate
Bicarbonate buffering of H+ generates additional CO2 independent of mitochondrial oxidation
Fat oxidation produces more CO2 than O2 consumed
At maximal exercise, the largest contributor to increased cardiac output in untrained individuals is typically:
Equal increases in HR and SV across all intensities
Reduced preload
Increased stroke volume only
Increased heart rate only
The metabolic "sweet spot" for training is:
Lactate begins to accumulate significantly
RER equals 0.85 exactly
Where the body burns the highest amount of fat for fuel while preserving CHO
Total fat mass decreases fastest
During fatigue at a constant force output, the CNS typically compensates by:
Decreasing recruitment to conserve ATP
Increasing neural drive: higher firing rates and/or additional motor unit recruitment
Eliminating rate coding to prevent tetanus
Reducing antagonist co-contraction only
Which fuel sources contributes relatively little to energy production
fat
protein
CHO
All contribute equally
An electrical signal that triggers muscle contraction is:
ACh
Calcium
Action Potential
None of the above
Which structural protein primarily contributes to passive tension when a relaxed sarcomere is stretched?
Nebulin
Troponin I
Titin
Desmin
What determines the muscle fiber type of a specific motor unit?
The joint angle
The blood flow
The alpha motor neuron
The load applied
Which second messenger is most directly increased by beta-adrenergic receptor activation in muscle and liver?
cAMP
IP3
cGMP
NADPH
During repeated high-intensity contractions, extracellular K+ can rise. The immediate functional consequence most associated with this is:
Increased myosin ATPase activity
Reduced action potential propagation and force production
Increased calcium sensitivity of troponin
Improved membrane excitability indefinitely
The 'toe region' of a tendon stress–strain curve primarily reflects:
Uncrimping and alignment of collagen fibers
Irreversible microfailure of collagen
Viscous damping due to fluid flow only
Maximum stiffness of aligned collagen
During high-intensity exercise, what is the primary immediate buffer of ATP concentration in skeletal muscle?
Hepatic gluconeogenesis
Anaerobic glycolysis via lactate dehydrogenase
Mitochondrial oxidative phosphorylation
Phosphocreatine via the creatine kinase reaction
A vertical jump occurs primarily in which anatomical plane?
Frontal
Transverse
Horizontal
Sagittal
According to the 'Size Principle,' which motor units are recruited first?
Small, low-threshold units
Large, high-threshold units
Fast-fatigable units
Intermediate units
Which muscle is the primary agonist for hip extension during a vertical jump?
Gastrocnemius
Rectus femoris
Biceps femoris
Gluteus maximus
Cardiovascular drift during prolonged exercise in the heat is characterized by:
Increasing HR and decreasing SV at a constant workload
Increasing SV and Q with stable HR
Decreasing HR and increasing SV
No change in HR or SV
Which fiber type has a high threshold of excitation?
Type IIx
Type I
Slow-twitch
Small motor units
During heavy exercise, the largest immediate source of metabolic acidosis in muscle is best attributed to:
Urea cycle activation
ATP hydrolysis and associated reactions increasing H+ availability
Lactate directly releasing H+
Ketone body production
