Explain the process of gaseous exchange between the lungs and pulmonary capillaries at rest and during exercise.

Compare and contrast the characteristics of the lactic acid and aerobic system.

Describe the characteristics associated with the three phases (stages) of learning, with reference to the progression from novice to skilled performance.

Outline why sports science students must be careful when interpreting the correlation between two variables.

At rest:
differences in the partial pressures of the gases in the alveoli and blood create a «pressure» diffusion gradient across the respiratory membrane ✔

gases move from an area of higher pressure to one of lower pressure ✔

the amount and rate of gas exchange that occurs across the membrane depends on the partial pressure of each gas
OR
Fick’s Law ✔

the «pressure» diffusion gradient for CO₂ is less than for oxygen exchange ✔

PO₂ at the alveoli is 105mm Hg/higher and PO₂ of the blood in the pulmonary capillaries is 40mm Hg/lower ✔

PCO₂ in blood in pulmonary capillaries passing beside alveoli is 46mm Hg/higher and air in the alveoli has a PCO₂ of 40mm Hg/is lower ✔

oxygen/O₂ enters the blood and carbon dioxide/CO₂ leaves it ✔

CO₂ crosses the alveolar membrane more readily than oxygen without a large pressure gradient ✔

gases move randomly across the membrane when at equilibrium, but the net movement stays the same
OR
the number of particles moving across the membrane in one direction is equal to the number moving in the opposite direction ✔

During exercise:
oxygen diffusion capacity increases as one moves from rest to exercise ✔

greater arterio-venous difference facilitating O₂ exchange ✔

exercise increases CO₂ production and facilitates CO₂ removal ✔

Award [4 max] if there is no reference to changes during exercise.

Award [1 max] per row.

Award [4 max] for contrasting only.

For duration accept within the range of 15s–120s for lactic acid system and 55s–infinite time.

Cognitive/verbal (early phase):
learning occurs through verbal labels/physical demonstrations, videos, films, reading information or listening to a description of the skill
OR
to aid memory learning occurs through trial and error ✔

Associative/motor phase (intermediate phase):
a performer practices the task and can associate their movements with the mental image of the skill ✔

a performer begins to “feel” what a good performance is like kinaesthetically
OR
a performer begins to detect and correct errors in their performance ✔

Autonomous phase (final phase):
reaction time is shorter as motor programmes are well learnt «stored in long-term memory» ✔

skills appear automatic as attention is focused elsewhere «for example on tactics, the move or pass or shot and on using fakes» ✔

a performer judges his/her own performance and make changes without external feedback from a coach ✔

Progression novice-skilled performer:
a novice performance will typically occur during the «early» cognitive and associative phase ✔

a performer will gradually get more skilled in their performance as they get closer to the autonomous phase ✔

Award [1 max] if the three phases are stated and not explained.

Award [3 max] 1 mark per description per phase.

Award [3 max], 1 mark for correctly relating novice and/or skilled performance to each phase.

correlational research is where we observe what naturally goes on in the world without directly interfering with it ✔

the only way to infer causality is through comparison of two controlled situations «one in which the cause is present and one in which the cause is absent» ✔

these situations should be identical in all senses except the presence of cause ✔

with ecological validity it can be difficult to ensure identical situations ✔

a confounding variable «third-variable»
OR
causality between two variables cannot be assumed because there may be other measured or unmeasured variables affecting the results ✔

correlation coefficients say nothing about which variable causes the other to change ✔

the inductive approach has a logical flaw eg although night and day are perfectly correlated, neither causes the other «both are caused by an external factor – the spinning of the Earth in relation to the Sun» ✔

Most candidates scored high marks on this question. They were able to correctly identify the flow of gases, how this occurred and the changes that occur during exercise.

Some candidates demonstrated excellent examination techniques and placed this information into a table. Many candidates struggled to compare the two systems and only accessed the contrasting marking points. Candidates lacked specific knowledge of the number of ATP molecules produced in each system and this requires further revision and clarification. Many candidates were able to identify some by-products but lacked depth in their answer and rarely scored more than 3 marks for this question.

Most candidates were able to refer to the changes from novice to skilled performer across the three stages of learning. Generally, most candidates correctly identified the stages of learning; however few candidates could accurately describe the stages in enough detail to allow them to access the full marks.

Candidates had a strong understanding that correlation does not mean causation; however they struggled to apply this further to gain more than 2 marks for this question.