Explain the phenomena of oxygen deficit and oxygen debt for an individual hiking 20 km in mountains.

During the 20 km hike, the hiker stops briefly to have a sandwich for lunch.

Discuss the effects of insulin and exercise on glucose uptake in the hiker’s leg muscles.

Describe the structural features of the hiker’s femurs.

During the weeks of training prior to the journey, the hiker’s leg muscles increased in size.

Outline four other general characteristics which are common to muscle tissue.

oxygen deficit:
as exercise commences the breathing rate increases/an oxygen deficit is incurred ✔

oxygen deficit may further increase as a result of walking up inclines and vice versa ✔

ATP will be supplied via anaerobic pathways ✔

at a steady submaximal level there will be a plateauing of breathing rate and heart rate ✔

PC stores can be resynthesized during steady state ✔

oxygen debt:
at the end of the hike, the walkers breathing rate <and heart rate> remains elevated
OR
at the end of the hike, excess post-exercise oxygen consumption occurs
OR
oxygen deficit is paid back after exercise/oxygen debt ✔

the greater the oxygen deficit the greater the oxygen debt✔

ATP/ PC stores are replenished <in the muscles>✔

myoglobin/ hemoglobin are reoxygenated ✔

phosphagen stores and myoglobin stores can be replenished within a few minutes of recovery <alactacid/fast component> ✔

aerobically metabolize lactic acid
OR
resynthesize lactate to glycogen ✔

replacement of muscle/liver glycogen stores ✔

the recycling/removal of lactate and replenishment of glycogen stores may take several hours after exercise <lactacid/slow component> ✔

Award [4 max] from oxygen debt OR oxygen deficit.

Accept a suitably annotated drawing.

eating will stimulate the release of insulin / glycogenesis✔

insulin increases the uptake of glucose to be stored as glycogen ✔

muscle contraction / 20 km hike will stimulate the uptake of glucose ✔

the pathway via exercise is different / phosphorylases the glucose / allows for the glucose to be used rather than stored ✔

the effects of the muscular contractions during the hike will persist into early post-exercise in order to restore glucose stores ✔

exercise inhibits the release of insulin ✔

Award [3 max] for insulin or exercise.

diaphysis:
the long shaft of the long bone / femur ✔

compact bone:
type of bone found in the shaft / solid bone structure ✔

epiphysis:
found on the ends of the long bone / femur ✔

spongy bone / cancellous bone:
bone tissue found on the ends / honeycombed in appearance ✔

articular cartilage:
tissue found on the ends of the femur where it will articulate with other bones / joints ✔

bone marrow:
found inside the shaft / in spongy bone ✔

marrow cavity:
found in the hollow region of the shaft ✔

blood vessel:
bone is living tissue and is supplied by blood through vessels ✔

periosteum:
outer skin of bone ✔

muscle contractility:
the ability of a muscle to contract forcefully ✔

extensibility:
a muscle can be stretched beyond its normal resting length ✔

elasticity:
the ability of a muscle to recoil back to its original resting length after stretching ✔

atrophy:
a decrease in size due to a lack of exercising a muscle group ✔

a decrease in size is primarily due to a decrease in the number of myofibrils and sarcomeres inside the muscle fibre ✔

controlled by nerves:
enable movement to occur / send sensations back to the brain to inform tension and angles ✔

fed by capillaries:
these supply nutrients / oxygen and remove wastes✔

Characteristic does not need to be named; description is sufficient.

Very few students achieved full marks with this question. They generally understood that oxygen deficit occurs at the start and that the debt is at the end but beyond that they struggled with these phenomena.

Candidates were seldom aware that insulin affects the uptake of glucose differently during exercise, so full marks were elusive in this question.

A good number of candidates managed this question well.

A good number of candidates managed this question well.