Analyse the three energy systems (ATP-PC, anaerobic glycolysis, aerobic) and the training types that target each, with reference to specific sporting contexts

A 5-mark distinguish needs all three dimensions contrasted.

Anaerobic glycolysis. Substrate: muscle glycogen and blood glucose broken down without oxygen; by-product: lactate and H+ ions that contribute to fatigue; duration: dominant from about $10$ seconds to $2$ minutes.

Aerobic system. Substrate: carbohydrate and fat (and protein at extreme durations) oxidised in the mitochondria; by-products: carbon dioxide, water and heat, cleared continuously; duration: dominant beyond $2$ minutes and sustainable.

Markers reward (1) substrate for each, (2) by-product for each, (3) duration for each, with a clear contrast.

An 8-mark justify needs a named athlete, the dominant system, matched training, and reasoning.

Choose a 400m runner

Dominant system is anaerobic glycolysis (race around $45$ to $50$ seconds).

Training and ratios

Repeated $200$ to $300$m intervals near race pace with a work-to-rest ratio of about $1:2$ to $1:5$ to develop lactate tolerance, plus maximal sprints (ATP-PC, ratio about $1:5$ to $1:12$) for top-end speed and an aerobic base for recovery.

Justify

Tie each choice to the substrate and by-product profile (H+ accumulation tolerance for lactic work, CP resynthesis for ATP-PC work).

Markers reward (1) the dominant system identified, (2) training types with correct work-to-rest ratios, (3) the justification linked to the energy-system physiology.

• ATP-PC system: dominant for about the first 10 seconds of maximal effort.
• Anaerobic glycolysis (lactic): dominant from about 10 seconds to 2 minutes (peak contribution near 30 seconds).
• Aerobic system: dominant beyond about 2 minutes and sustainable thereafter.

Marking criteria: 1 mark for each system correctly named AND paired with its approximate dominant duration. A system named without a duration (or with the wrong duration) earns nothing for that line.

• ATP-PC: substrate = stored ATP and creatine phosphate (CP); by-product = none of consequence (alactic).
• Anaerobic glycolysis: substrate = muscle glycogen and blood glucose (broken down without oxygen); by-product = lactate and H+ ions.
• Aerobic system: substrate = carbohydrate and fat (protein at extreme durations), oxidised in the mitochondria; by-products = carbon dioxide, water and heat.

Marking criteria: up to 3 marks for a correct substrate for each system, up to 1 further mark for correctly naming the by-products (especially lactate/H+ for glycolysis and CO2/water for aerobic). Saying anaerobic glycolysis produces CO2 is a substrate/by-product error.

ATP-PC

Highest power output of any system but the smallest store; dominant only ~10 seconds; no fatiguing by-product (alactic); ~50 percent of CP restored in ~30 seconds, near-complete in 2 to 3 minutes.

Anaerobic glycolysis

High but lower peak power than ATP-PC; dominant ~10 seconds to 2 minutes; produces lactate and H+ that drive local fatigue; lactate cleared over minutes to hours.

Why long recoveries for a sprinter

A 100m race (~10 to 11 seconds) is almost entirely ATP-PC. To train top-end speed the athlete must repeat near-maximal sprints at full quality, which requires CP to be largely resynthesised between reps. A work-to-rest ratio of about 1:5 to 1:12 (e.g. a 6 second sprint with 60 to 90 seconds rest) allows CP restoration so each rep stays maximal, rather than degrading into a fatigued, lactic effort.

Marking criteria: 1 mark each for a correct contrast on power, duration, by-product and recovery (max 4), plus 1 mark for linking CP resynthesis to the long work-to-rest ratio and maintained sprint quality. A bare "they need rest" without CP resynthesis caps the final mark.

• Start (0 to ~5 seconds): the ATP-PC system fuels the explosive acceleration out of the blocks using stored ATP and CP.
• Middle (~5 to ~40 seconds): as CP depletes, anaerobic glycolysis takes over, supplying ATP rapidly from glycogen but accumulating lactate and H+.
• Back straight (final ~7 seconds): with glycolytic by-products rising, the aerobic system makes an increasing relative contribution and helps clear lactate, though power falls (the classic 400m "rigor").

Dominant system. Anaerobic glycolysis, because the bulk of the 47 second effort falls in the 10 second to 2 minute band where glycolysis supplies most ATP, and the characteristic finish-line fatigue is the H+ accumulation it produces.

Marking criteria: 1 mark for each system's contribution correctly placed in time (max 3), 1 mark for naming anaerobic glycolysis as dominant, 1 mark for justifying it via the duration band and the lactate/H+ fatigue signature. Treating the systems as switching cleanly on and off (rather than overlapping) caps at 3.

(a) Trend

Peak power falls progressively across the six sprints, from 1200 W to 920 W - a drop of 280 W, or about 23 percent, with the largest single drop early (sprints 2 to 4). The decline is monotonic but appears to flatten slightly by sprint 6.

(b) Explanation

Each 6 second sprint is fuelled mainly by the ATP-PC system. With only 24 seconds of recovery (work-to-rest 1:4), CP is only partially resynthesised between reps (about 50 percent returns in ~30 seconds), so each sprint starts with less available CP. As CP runs short, the athlete leans more on anaerobic glycolysis, accumulating H+ that impairs contraction - so peak power falls.

(c) Recommendation

Lengthen the recovery to roughly 60 to 90 seconds (work-to-rest ~1:10 to 1:15). Justification: this allows near-complete CP resynthesis between reps, so each sprint can again be fuelled predominantly by the ATP-PC system at full power, preserving sprint quality and training top-end speed rather than lactate tolerance.

Marking criteria: (a) 1 mark direction, 1 mark quantified (the ~280 W / ~23 percent fall). (b) 1 mark CP partial resynthesis with the short rest, 1 mark shift to glycolysis and H+ fatigue. (c) 1 mark for a longer recovery / higher work-to-rest ratio, 1 mark for justifying it via CP resynthesis and maintained ATP-PC power. Describing the data with no energy-system link caps at 2.

Continuous training. Steady, uninterrupted moderate effort (20 to 60 minutes at about 60 to 75 percent VO2max). It develops the aerobic base - capillary density, mitochondrial enzymes and fat oxidation. Priority for a marathon runner building aerobic mileage.

Interval training. Repeated work bouts separated by timed recovery, with duration, intensity and rest set to target a chosen system (e.g. short maximal sprints for ATP-PC, or 2 to 5 minute efforts at 85 to 95 percent VO2max for VO2max and lactate buffering). Priority for a 400m runner or team-sport athlete developing repeated high-intensity capacity.

Marking criteria: 1 mark for a correct description of each method (max 2), 1 mark for an appropriate matched sporting context for each (max 2). A vague "interval training is on-off" with no intensity/duration detail caps at 1 for that method.

This is an 8-mark justify. Markers reward a named athlete, the correct dominant system, matched training types WITH work-to-rest ratios, and reasoning tied to substrate/by-product physiology.

Band 6 PLAN.

• Thesis: choose a 400m runner; the race (~45 to 50 seconds) is dominated by anaerobic glycolysis, so the program must overload glycolytic flux and H+ tolerance while supporting it with ATP-PC speed and an aerobic recovery base.
• Argument line 1 - lactic (priority): repeated 200 to 300m intervals at or faster than race pace, work-to-rest ~1:2 to 1:5, to train the muscle to keep producing ATP and contracting despite rising lactate and H+ (lactate tolerance).
• Argument line 2 - ATP-PC (support): maximal sprints up to 60m with long recovery, work-to-rest ~1:5 to 1:12, so CP resynthesises between reps and top-end speed is trained at full quality.
• Argument line 3 - aerobic (support): continuous and threshold running to raise lactate clearance and speed recovery between hard reps and sessions, even though the event itself is anaerobic.
• Synthesis: justify the ratio CHOICES by the by-product/substrate profile - short rests keep the lactic system loaded; long rests protect CP-fuelled quality - and weight the macrocycle towards the lactic work because that is the dominant race system.

Model paragraph (lactic line). The core of a 400m program is repeated 200 to 300m intervals run at or slightly above race pace with only partial recovery, a work-to-rest ratio near 1:3. The short recovery is deliberate: it keeps blood and muscle lactate elevated between reps, so the athlete trains to keep producing ATP through glycolysis and to keep contracting despite a rising H+ load - the exact demand of the final 100m of a 400m race. Because the limiting by-product is H+, not fuel depletion, the adaptation we want is improved buffering and lactate tolerance, which is why the ratio is kept tight rather than the long recoveries used for pure speed work.

Marker's note: top-band answers (1) name a specific athlete and the correct dominant system, (2) give training types WITH numeric work-to-rest ratios, (3) JUSTIFY each ratio through substrate/by-product physiology (CP resynthesis vs H+ tolerance) rather than just listing sessions, and (4) keep the supporting systems in proportion. A program that prescribes sessions without justifying the ratios, or that ignores the dominant system, stays mid-band.