2025 IB DP Sports, Exercise and Health Science 模擬試題連答案詳解

During a bicep curl, the biceps brachii is the primary muscle contracting concentrically to produce flexion at the elbow joint, making it the agonist. The triceps brachii relaxes and lengthens to allow the movement, making it the antagonist. The brachioradialis assists the biceps brachii in executing the movement, functioning as a synergist.

Award 1 mark for the correct option C.

Cardiovascular drift is characterized by a gradual decrease in stroke volume and a compensatory increase in heart rate during prolonged, steady-state exercise, especially in hot conditions. This occurs because fluid lost via sweating reduces blood plasma volume and increases blood viscosity. Additionally, more blood is directed to the skin for thermoregulation, reducing venous return and stroke volume. To maintain a constant cardiac output, the heart rate must increase.

Award 1 mark for identifying the correct physiological mechanism causing cardiovascular drift (Option B).

A floor routine is a gross motor skill because it involves large muscle groups and whole-body movements. It is a closed motor skill because the environment is stable, predictable, and self-paced. It is a serial motor skill because it links several discrete skills (such as individual flips or handsprings) together in a specific sequence.

Award 1 mark for the correct classification of the gymnast's motor skills (Option B).

A second-class lever has the load situated between the fulcrum and the effort. An example in the human body is plantar flexion (toe raise), where the ball of the foot acts as the fulcrum, the body weight acting through the tibia is the load, and the effort is exerted by the gastrocnemius. Because the effort arm is longer than the resistance (load) arm, the mechanical advantage is greater than 1, meaning it favors force production over speed or range of motion.

Award 1 mark for identifying the correct lever class example and its mechanical advantage (Option C).

Consuming low-glycemic index (GI) foods 3 to 4 hours before the race ensures a slow, sustained release of glucose into the bloodstream, avoiding rapid insulin spikes and preserving liver and muscle glycogen. Consuming high-GI foods during the race provides rapid, easily digestible glucose to maintain blood glucose levels and delay fatigue without causing digestive distress.

Award 1 mark for identifying the correct pre-exercise and during-exercise carbohydrate strategy (Option B).

Self-Determination Theory identifies three basic psychological needs: autonomy, competence, and relatedness. Competence refers to the need to feel effective, master tasks, and experience growth. A tennis player mastering a difficult serve through constructive feedback directly illustrates the satisfaction of this need.

Award 1 mark for the correct application of the psychological need for competence (Option C).

At the onset of moderate-intensity exercise, ventilation increases immediately and rapidly. This acute response is achieved by increases in both tidal volume (depth of breathing) and breathing frequency (rate of breathing) to meet the sudden increase in oxygen demand and carbon dioxide production.

Award 1 mark for identifying the correct ventilatory response at the start of moderate-intensity exercise (Option A).

In the sliding filament theory, calcium ions are released from the sarcoplasmic reticulum and bind to troponin on the actin filament. This binding causes a conformational shift in tropomyosin, exposing the active myosin-binding sites on the actin filament, which allows the myosin heads to bind and form cross-bridges.

Award 1 mark for identifying the correct role of calcium ions in muscle contraction (Option B).

During an eccentric contraction, the muscle is lengthening under tension, which causes the sarcomere to lengthen. When the sarcomere lengthens, the H-zone (the region containing only thick myosin filaments) widens, and the overlap between actin and myosin decreases as they slide past each other. The A-band, which represents the length of the thick myosin filaments, remains constant in length.

Award [1] for the correct option B. Award [0] for any other response.

At rest, the heart is under dominant parasympathetic (vagal) tone, which keeps the resting heart rate below its intrinsic rate of about 100 bpm. During the initial stages of exercise, the rapid increase in heart rate up to 100 bpm is primarily achieved by the withdrawal of this parasympathetic pathway (vagal withdrawal). Increases above 100 bpm are driven by sympathetic nervous system stimulation.

Award [1] for the correct option B. Award [0] for any other response.

Blocked practice is a practice schedule in which one skill or movement is practiced repeatedly before moving on to practice another skill. In this scenario, the gymnast performs multiple repetitions of each movement sequentially in distinct blocks.

Award [1] for the correct option B. Award [0] for any other response.

According to the principle of conservation of angular momentum, angular momentum (\(L = I \omega\)) remains constant when no external torque acts on the body. By tucking their limbs closer to the axis of rotation, the high-jumper decreases their moment of inertia (\(I\)). To conserve angular momentum, their angular velocity (\(\omega\)) must increase.

Award [1] for the correct option B. Award [0] for any other response.

Lipids (fats) have the highest energy density among the macronutrients, yielding approximately 37 kilojoules per gram (kJ/g). Carbohydrates and proteins yield approximately 17 kJ/g.

Award [1] for the correct option B. Award [0] for any other response.

A strain is an injury to a muscle or tendon, whereas a sprain is an injury to a ligament. A Grade I strain involves microscopic tearing of muscle or tendon fibers, resulting in mild pain, minimal swelling, and minimal or no loss of muscle strength.

Award [1] for the correct option A. Award [0] for any other response.

Self-Determination Theory (SDT) posits that human motivation is driven by three basic, innate psychological needs: autonomy (the need to feel in control of one's actions), competence (the need to feel effective in interactions with the environment), and relatedness (the need to feel connected to others).

Award [1] for the correct option A. Award [0] for any other response.

Associative attentional focus (association) involves focusing internal attention on physiological and bodily sensations, such as respiration, muscle fatigue, and biomechanical feedback, to monitor and optimize performance. In contrast, dissociative focus involves deliberately directing attention away from bodily pain and fatigue toward external distractors.

Award [1] for the correct option C. Award [0] for any other response.

Type I (slow-twitch) muscle fibers are designed for aerobic endurance activities. They contain high levels of myoglobin (giving them a red appearance) and have a high capillary density to support oxygen delivery. Additionally, they have high oxidative capacity but low glycolytic capacity compared to fast-twitch fibers.

Award [1] mark for the correct answer (A).
- Reject other options: Type I fibers do not have low myoglobin or low capillary density, nor do they rely primarily on high glycolytic capacity.

During prolonged exercise in a warm environment, sweating causes a loss of body water, leading to a decrease in plasma volume. This reduction in blood volume decreases venous return and stroke volume. To maintain a constant cardiac output (
\(Q = \text{HR} \times \text{SV}\)), the heart rate must progressively increase.

Award [1] mark for the correct answer (B).
- Option A is incorrect as plasma volume decreases, not increases.
- Option C is incorrect as venous return decreases.
- Option D is incorrect because stroke volume decreases.

Kayaking down a rapid river is an open skill because the environment is constantly changing and unpredictable. It is a gross skill because it involves large muscle groups of the upper body and core. It is a continuous skill because the movement cycle is ongoing without a distinct, defined beginning and end.

Award [1] mark for the correct answer (C).
- A handstand (A) is closed and static.
- A penalty kick (B) is closed and discrete.
- Archery (D) is closed and discrete.

Plantar flexion is an example of a second-class lever in the human body. In a second-class lever system, the load (body weight acting through the ankle joint) is situated in the middle, between the fulcrum (ball of the foot/metatarsophalangeal joints) and the effort (contraction of the gastrocnemius and soleus muscles pulling upwards on the calcaneus).

Award [1] mark for the correct answer (B).
- Option A describes a first-class lever with incorrect effort placement.
- Option C describes a third-class lever.
- Option D incorrectly pairs a second-class lever with the effort in the middle.

Consuming a high glycemic index meal shortly before exercise causes a rapid spike in blood glucose levels, prompting a large release of insulin. Once exercise begins, the muscle cells take up glucose rapidly due to contraction, which—combined with high insulin levels—can lead to rebound hypoglycemia and premature fatigue.

Award [1] mark for the correct answer (B).
- Option A describes the behavior of a low GI meal.
- Option C is incorrect as high insulin levels inhibit fatty acid oxidation.
- Option D is incorrect as high GI intake does not directly reduce lactic acid accumulation.

The Inverted-U hypothesis states that the optimal level of arousal varies depending on the task and individual. Fine, high-precision motor skills requiring intense concentration (such as pistol shooting) are best performed at lower levels of arousal. Conversely, gross skills involving high force and power (such as a rugby tackle) require higher levels of arousal to achieve peak performance.

Award [1] mark for the correct answer (C).
- Option A is incorrect because pistol shooting is a low-force, high-precision task.
- Option B is incorrect because rugby tackles benefit from high arousal.
- Option D is incorrect because optimal arousal is task-dependent.

A sprain is specifically an injury to a ligament, which is the fibrous connective tissue connecting bone to bone. A strain is an injury to a muscle or a tendon, which connects muscle to bone.

Award [1] mark for the correct answer (B).
- Option A reverses the definitions of sprain and strain.
- Options C and D are incorrect classifications of the injury types and locations.

Self-Determination Theory (SDT) posits that three innate, universal psychological needs must be met for optimal psychological growth and intrinsic motivation: Autonomy (the need to feel in control of one's own behaviors), Competence (the need to produce desired outcomes and experience mastery), and Relatedness (the need to feel connected to others).

Award [1] mark for the correct answer (A).
- Options B, C, and D contain concepts from other psychological motivation models (such as McClelland's achievement theory or general self-efficacy concepts), which are not the three core components of Self-Determination Theory.

During the downward phase of a squat, the quadriceps act as agonists to control the speed of descent against gravity. Since the knee is flexing and the quadriceps are lengthening under tension, this is an eccentric contraction.

Award 1 mark for the correct answer (B). All other options are incorrect.

During prolonged exercise in a warm environment, fluid is lost through sweat, which reduces plasma volume and venous return. This reduction in venous return causes stroke volume to decrease. To maintain a constant cardiac output, calculated as \(\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}\), the heart rate must progressively increase.

Award 1 mark for identifying the correct physiological changes of cardiovascular drift (B).

A learning curve shows performance on the vertical axis and time/practice on the horizontal axis. A positively accelerated learning curve starts with a shallow slope (slow progress at first) and becomes progressively steeper (rapid improvement later), which matches the swimmer's progress.

Award 1 mark for identifying the correct learning curve (C).

When a ball has backspin, the top surface rotates in the same direction as the relative airflow, accelerating the air over the top. According to Bernoulli's principle, an increase in air velocity leads to a decrease in air pressure. Thus, a low-pressure zone is created on top of the ball and a high-pressure zone on the bottom, generating an upward lift force (Magnus effect).

Award 1 mark for the correct answer (A).

Glygogen is stored primarily in the liver and skeletal muscles. Liver glycogen can be broken down into glucose and released into the blood stream to maintain normal systemic blood glucose levels. Skeletal muscle glycogen, however, is used locally by the contracting muscle fibers because muscles lack the enzyme necessary to release glucose into general circulation.

Award 1 mark for the correct option (B).

Fleishman categorizes motor abilities into perceptual-motor abilities (which involve sensory and motor integration, such as control precision, multi-limb coordination, and reaction time) and physical proficiency abilities (which are structural and physiological traits, such as dynamic strength, extent flexibility, and explosive strength). Therefore, dynamic strength is a physical proficiency ability.

Award 1 mark for the correct option (D).

(a) An isometric contraction is a muscular contraction where the tension increases but the muscle length remains constant and there is no joint movement. Example: Holding a plank position, or holding a rugby scrum.

(b) During the concentric phase of a bicep curl:
- Agonist: The biceps brachii acts as the agonist; it contracts concentrically (shortens) to produce elbow flexion.
- Antagonist: The triceps brachii acts as the antagonist; it must relax and lengthen to allow the elbow flexion to occur.
- Stabilizer (Fixator): Muscles like the rotator cuff or anterior deltoid act as stabilizers, contracting isometrically to anchor the shoulder joint, preventing unwanted movement and ensuring a stable base.

(c) Distinctions between Type I and Type IIb muscle fibers:
- Fatigue resistance: Type I fibers have high fatigue resistance, allowing for long-duration performance, whereas Type IIb fibers have low fatigue resistance and fatigue rapidly.
- Capillary density: Type I fibers have a high capillary density to maximize oxygen delivery, while Type IIb fibers have a low capillary density.
- Primary fuel source: Type I fibers rely primarily on lipids (fats) and aerobic metabolism, whereas Type IIb fibers rely mainly on glycogen and creatine phosphate via anaerobic pathways.

(a) Award [1] for correct definition (tension increases, no change in muscle length or joint movement) and [1] for an appropriate sporting example (e.g., plank, wall sit, rugby scrum).

(b) Award up to [4] for explanation of roles:
- [1] for identifying biceps brachii as agonist and explaining it shortens to cause flexion.
- [1] for identifying triceps brachii as antagonist and explaining it relaxes/extends to allow movement.
- [2] for identifying stabilizer (e.g., rotator cuff or deltoid) and explaining its role in stabilizing the shoulder girdle/preventing unwanted movement.

(c) Award up to [4]:
- [1] for distinguishing fatigue resistance (Type I high vs Type IIb low).
- [1] for distinguishing capillary density (Type I high vs Type IIb low).
- [1] for distinguishing primary fuel source (Type I fats/aerobic vs Type IIb glycogen/phosphocreatine/anaerobic).
- [1] for clear structured comparison using comparative language.

(a) 1. Cognitive stage: The beginner attempts to understand the task, uses trial and error, has highly inconsistent performance, and relies heavily on external feedback.
2. Associative stage: The practice phase where movement becomes more consistent, errors are fewer, and the learner begins to detect their own performance errors using internal feedback.
3. Autonomous stage: Skill is performed automatically with high efficiency and minimal conscious control, allowing the performer to focus on environmental cues and tactics.

(b) Intrinsic feedback is sensory information available directly to the performer through internal receptors (proprioception, feeling the movement, kinesthesis). Extrinsic feedback is augmented information provided by external sources (e.g., coach's comments, video feedback, stopwatch).

(c) Massed practice involves continuous practice with little to no rest intervals, while distributed practice involves practice sessions interspersed with rest or alternative activities.
For a beginner learning a complex motor skill (tennis serve):
- Massed practice allows rapid repetition of the skill, which can help establish basic movement patterns. However, it can lead to physical and mental fatigue, increasing injury risk and degrading performance quality. Beginners may also lose motivation.
- Distributed practice provides rest intervals which allow for physical recovery and cognitive rehearsal (consolidation of memory), reducing fatigue and maintaining high concentration levels. This is highly effective for complex tasks where cognitive load is high.
- Evaluation: Distributed practice is generally superior for beginners learning complex skills to ensure safety, quality of movement, and cognitive consolidation.

(a) Award [1] per stage correctly described: Cognitive (understanding/trial-and-error), Associative (practice/refining/internal detection), Autonomous (automatic/consistent/tactical focus). [3 max]

(b) Award [1] for describing intrinsic feedback (self-sensed, proprioceptive) and [1] for describing extrinsic feedback (augmented, external source like coach/video). [2 max]

(c) Award up to [5] for evaluation:
- [1] for defining/contrasting massed and distributed practice.
- [1] for explaining how massed practice causes fatigue/loss of focus, impairing learning for a beginner.
- [1] for explaining how distributed practice offers physical recovery/cognitive rest.
- [1] for explaining that distributed practice allows mental rehearsal/feedback processing between trials.
- [1] for a clear concluding judgment (e.g., distributed practice is more appropriate for beginners learning complex skills).

(a) Dehydration causes a decrease in plasma/blood volume. This leads to a decrease in stroke volume (the amount of blood pumped per beat). To maintain cardiac output (\(\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}\)), heart rate must increase, causing cardiovascular drift. Additionally, reduced blood volume decreases blood flow to the skin, which impairs sweating and heat dissipation (evaporative cooling), leading to an elevated core body temperature and compromised thermoregulation.

(b) High GI carbohydrates (e.g., glucose, sports drinks) are rapidly digested and absorbed, causing a rapid and sharp rise in blood glucose levels. Low GI carbohydrates (e.g., oats, brown pasta) are digested and absorbed slowly, providing a gradual, sustained release of glucose into the bloodstream.
Timing recommendations:
- Pre-event (2–4 hours before): Low GI foods are recommended to provide sustained energy release without causing rapid insulin spikes that could lead to rebound hypoglycemia.
- Immediately before/during the event: High GI carbohydrates are recommended to provide rapid energy, spare muscle glycogen, and maintain blood glucose levels.
- Post-event (recovery): High GI carbohydrates are beneficial to rapidly replenish depleted muscle and liver glycogen stores during the immediate recovery window.

(a) Award up to [4] for explanation:
- [1] for stating dehydration reduces blood/plasma volume.
- [1] for explaining the reduction in stroke volume and compensatory increase in heart rate (cardiovascular drift) to maintain cardiac output.
- [1] for explaining that reduced blood flow to skin impairs sweating / evaporative cooling.
- [1] for linking impaired heat dissipation to increased core body temperature.

(b) Award up to [6] marks total:
- [2] for distinguishing: High GI causes rapid rise in blood glucose / rapid digestion [1]; Low GI causes slow/gradual rise in blood glucose / slow digestion [1].
- [4] for discussion of timing (must include pre, during, or post recommendations with justification):
- [1] Pre-event (2-4 hours): Low GI recommended to ensure sustained energy/prevent hypoglycemia.
- [1] During event: High GI recommended for rapid absorption/immediate energy.
- [1] Post-event: High GI recommended to optimize rapid glycogen resynthesis.
- [1] Supporting scientific justification linking GI properties to physiological demands of the athletic timeline.

Part (a) Cardiovascular responses during submaximal exercise:
- Heart Rate (HR): The elite athlete will have a significantly lower heart rate during submaximal exercise compared to an untrained individual.
- Stroke Volume (SV): The elite athlete will have a much higher stroke volume compared to the untrained individual.
- Cardiac Output (\(Q\)): At a given absolute submaximal workload, cardiac output remains relatively similar between both individuals because the oxygen demand for the same task is comparable, though the elite athlete may have a slightly lower cardiac output due to superior mechanical efficiency.
- Arteriovenous Oxygen Difference (\(a-vO_2\) diff): The elite athlete will have a higher arteriovenous oxygen difference, meaning their active muscles can extract oxygen more efficiently from the blood.

Part (b) Mechanisms regulating blood flow redistribution:
- Sympathetic Nervous System (SNS) Activation: The transition to exercise triggers the sympathetic nervous system, causing widespread vasoconstriction of arterioles.
- Adrenergic Receptors: Vasoconstriction occurs predominantly in non-essential organs (such as the kidneys, stomach, liver, and intestines) via alpha-adrenergic receptors, reducing blood flow to these areas.
- Local Autoregulation (Vasodilation): In active skeletal muscle, local chemical changes (metabolic byproducts) override the sympathetic vasoconstriction (a process called functional sympatholysis). These triggers include decreased oxygen levels, increased carbon dioxide, increased hydrogen ions (lower pH), increased lactate, increased potassium, and increased local temperature.
- Nitric Oxide (NO) Release: Shear stress on vascular walls stimulates the release of nitric oxide from endothelial cells, which induces relaxation of smooth muscle in the arterioles supplying active muscles, leading to vasodilation.
- Precapillary Sphincters: Precapillary sphincters in the capillary beds of active skeletal muscles relax, opening up massive capillary networks to increase local perfusion.
- Thermoregulation: As body temperature rises, the sympathetic system eventually vasodilates cutaneous (skin) blood vessels to facilitate heat loss through radiation and convection.

Part (c) Physiological adaptations after 12 weeks of aerobic training:
Cardiovascular Adaptations (Max 6 marks):
- Cardiac Hypertrophy: The left ventricle chamber size increases (eccentric hypertrophy), allowing for greater volume of blood (preload) to fill the ventricle.
- Stroke Volume (SV) Increase: Stroke volume increases significantly at rest, submaximal, and maximal exercise due to increased blood volume and contractility.
- Resting and Submaximal Heart Rate Decrease: Resting bradycardia occurs due to increased parasympathetic (vagal) activity and reduced sympathetic drive, alongside the larger SV.
- Maximal Cardiac Output (\(Q_{max}\)) Increase: While resting and submaximal cardiac output remains unchanged, maximal cardiac output increases substantially to support higher maximal oxygen consumption (\(VO_2\) max).
- Blood Volume Expansion: Plasma volume and total red blood cell count increase, improving venous return (Frank-Starling mechanism) and overall oxygen-carrying capacity.
- Increased Capillarization: Capillary density in active skeletal muscles increases (capillary-to-fiber ratio), lowering diffusion distance and increasing transit time for oxygen exchange.

Respiratory Adaptations (Max 4 marks):
- Increased Maximal Minute Ventilation (\(VE_{max}\)): Driven by increases in both maximal tidal volume (\(TV\)) and maximal breathing frequency.
- Increased Pulmonary Diffusion Capacity: Improved perfusion of the lungs and increased alveolar-capillary surface area enhance gas exchange at maximal intensities.
- Improved Respiratory Muscle Efficiency: The diaphragm and intercostal muscles adapt to become more aerobic (increased mitochondrial/capillary density), reducing their oxygen demand during exercise and delaying fatigue.
- Submaximal Ventilation Efficiency: Submaximal minute ventilation decreases or remains stable, meaning the body requires less ventilatory effort (breathing is more efficient) for a given workload.

Part (a) [4 marks max]
- Award [1] for lower submaximal heart rate in elite athletes.
- Award [1] for higher submaximal stroke volume in elite athletes.
- Award [1] for explaining that cardiac output (\(Q\)) remains similar/slightly lower in elite athletes at a given absolute workload.
- Award [1] for identifying higher arteriovenous oxygen difference (\(a-vO_2\) diff) in elite athletes.

Part (b) [6 marks max]
- Award [1] for mentioning sympathetic nervous system (SNS) stimulation causing vasoconstriction of arterioles.
- Award [1] for specifying vasoconstriction in non-essential organs (e.g., kidneys, gastrointestinal tract).
- Award [1] for explaining local vasodilation/autoregulation in active skeletal muscles.
- Award [1] for listing local chemical triggers of vasodilation (e.g., high \(CO_2\), lactate, \(H^+\), low \(O_2\), high temperature).
- Award [1] for explaining the role of Nitric Oxide (NO) in relaxing vascular smooth muscle.
- Award [1] for mentioning relaxation of precapillary sphincters in active muscle beds.
- Award [1] for noting cutaneous vasodilation for thermoregulation.

Part (c) [10 marks max]
Cardiovascular Adaptations (Max [6]):
- Award [1] for left ventricular hypertrophy (increased chamber volume).
- Award [1] for increased stroke volume (SV) across all states (rest, submax, max).
- Award [1] for bradycardia / lower resting and submaximal HR.
- Award [1] for increased maximal cardiac output (\(Q_{max}\)).
- Award [1] for increased plasma/blood volume.
- Award [1] for increased capillarization/capillary density in working muscles.

Respiratory Adaptations (Max [4]):
- Award [1] for increased maximal minute ventilation (\(VE_{max}\)).
- Award [1] for increased pulmonary diffusion capacity.
- Award [1] for structural/metabolic adaptations of respiratory muscles (diaphragm, intercostals).
- Award [1] for improved efficiency/lower minute ventilation at submaximal workloads.