Concept (read first)

Lesson Focus:
Running speed determines which energy system contributes the most energy. As speed increases, the primary energy contribution shifts from Aerobic Metabolism to Anaerobic Glycolysis, and at very high speeds to ATP-PC (PCr).

Multiple energy systems can contribute simultaneously. ‘Primary’ refers to the largest contributor. Some systems, like ATP-PC, are only active while their immediate stores are available.

• Aerobic Contribution: Uses oxygen to meet energy demand. When this system is primary, energy levels remain stable.
• Oxygen Deficit: When running speed exceeds aerobic capacity, oxygen supply cannot fully meet demand.
• Anaerobic Supplement: Any shortfall is covered by anaerobic systems drawing from a finite reserve (W′ Balance), causing energy to decline.

Trial B — Concept (read first)

Carbohydrate energy/fuel: isn’t instant; the body needs time to use it. During high-intensity, anaerobic-dominant exercise, glucose is broken down by glycolysis to make ATP, and if oxygen can’t keep up, pyruvate is converted to lactate—so early fueling can increase lactate without improving performance. Proper timing helps sustain effort and manage fatigue.

Fuel Timing Optimization: Fuel must be taken before fatigue becomes excessive, because once metabolic by-products accumulate, the body cannot efficiently restore usable energy. Waiting too long limits the performance benefit of fuel and increases the risk of rapid decline.

Crash Condition: Lactate reaching 100% ends the trial immediately, even if time remains or energy is sufficient.

Learning Goals:

• Observe how energy drains under anaerobic conditions.
• Understand how fuel timing can maintain W′ energy without causing lactate to reach the crash threshold.
• Recognize the trade-off between energy restoration and lactate accumulation.

Trial Guide Overview

VO₂ Max (Aerobic Capacity): In this lab, this represents the subject’s modeled oxygen budget—the maximum sustainable oxygen supply available to support running.

The Total VO₂ Cost: When running, total oxygen demand is modeled as the sum of:
- Resting Metabolic Rate (3.5 ml/kg/min): Baseline oxygen cost required to sustain basic physiological function (≈1 MET).
- Work VO₂: The additional oxygen required to perform the mechanical work of running.
- Oxygen Deficit: If Total VO₂ Cost > VO₂ Max, energy demand exceeds aerobic supply and energy is supplemented by the finite W′ Balance.

Trial B — Overview

In Trial B, the subject is operating entirely above their aerobic ceiling (Roma - 6.8 mph/Roman - 6.4), so anaerobic glycolysis is the primary energy system. The trial introduces the Lactate Proxy to visualize metabolic waste and demonstrates how fueling affects energy and lactate accumulation.

• In Trial A, oxygen delivery matched demand, so lactate was negligible.
• In Trial B, the system is stressed: oxygen supply is insufficient, and lactate begins to accumulate.

Trial A — Aerobic Metabolism

Goal: Find the highest speed at which the subject completes a 300 s trial without crossing into Anaerobic Dominance (remaining at or above 60% energy).

The 60% Threshold (Lab-Defined): In real physiology, the transition to anaerobic dominance occurs at an individual-specific threshold (commonly 50–90% of VO₂ max). In this lab, 60% is used as a standardized simulation threshold and is not a universal biological constant.

1. Calculate the "Oxygen Budget" (VO₂ Max)
Formula: VO₂max ≈ 15.3 × (HRmax / HRrest)
Model Info: Roma (34), Roman (43). HRrest: 72. HRmax: (220 - age).

2. Calculate the "Oxygen Cost"
Lab-Adjusted Formula: Total Cost = ((MPH × 26.8) × 0.2) + 3.5

3. The Forensic Test
Compare Total Cost to Oxygen Budget: If Cost > Budget, energy will drain. If Cost ≤ Budget, energy remains stable. The speed slider should be set to the highest MPH where the calculated cost is equal to or less than the budget.

Trial B — Anaerobic Metabolic Investigation

Module Instructions: Set the speed slider to 6.8 (Roma) or 6.4 (Roman) mph for the full 3-minute trial.

Pre-Test (Optional): Run a short pre-trial to observe how early vs. late fueling affects W′ energy recovery, Lactate accumulation, and Timing of fuel pulses.

Official Trial:

• Begin the 3-minute trial at 6.8 mph (Roma) or 6.4 mph (Roman) and maintain throughout.
• Monitor Energy and Lactate bars.
• Apply exactly 1 fuel pulse (+10 each) strategically to:
  • Keep W′ energy above 0% before the timer runs out.
  • Avoid Lactate reaching 100%.
  • Decide when to apply the fuel - when it is most optimized.