EXS101 Energy Systems Activity

Energy Systems: Working Together

Change the demand and duration of activity to see how the phosphagen, glycolytic, and oxidative systems work together to continually regenerate ATP.

The systems overlap. Their contribution depends on the demand, elapsed time, and exercise conditions.

Open the simplified demo

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Explore Different Demands

ATP is needed for cellular work all the time—not only during exercise. Choose an activity and explore how ATP demand and pathway roles change. Activity settings are illustrative examples, not individual predictions.

Slow Walking

ATP Demand Scenario
Phosphagen
Glycolytic
Oxidative
Start

All three bars show schematic changes in pathway roles. Bar lengths are illustrative, not measured ATP rates, energy percentages, or values to add together. Phase boundaries organize the display; they are not measured crossover times. See Research Evidence below.

Experiment: Change One Variable

Hold one variable constant while changing the other. Predict the changed condition, then compare the visual results to isolate the relationship.

Held constant: 30 seconds

Only intensity changes. Duration stays the same.

Reference Condition

Easy continuous • 30 sec

Your Changed Condition

How pathway roles change across the effort

Build Your Own Exercise Demand

Set the intensity and duration. Your visualization will run right here using the demand you created.

Rest / ongoing daily activity → Easy continuous → Sustained exercise → Vigorous effort → Brief maximal effort
Duration options are limited for brief maximal and vigorous scenarios. Limits are teaching constraints, not physiological cutoffs.

Your Activity

ATP Demand Scenario
Phosphagen
Glycolytic
Oxidative
Start
Try this: Can you create a demand where phosphagen contribution becomes especially large?
Try this: Can you create a demand where oxidative metabolism makes a large relative contribution?
Try this: What combination makes glycolytic contribution particularly important?

About This Model

This qualitative tracker is an instructional interpretation of research [1]. The three moving bars visualize broad patterns of overlap: rapid phosphagen support, rapid glycolytic activation, and increasing oxidative support. Their drawing coordinates and time constants are chosen for illustration, not fitted to research data. It is not a validated equation. It describes pathway roles at selected moments; it does not report ATP production rates, percentages, or total energy across the bout. Exercise mode, training, pacing, prior activity, and measurement method affect the balance. Glycolysis and oxidative metabolism are connected processes, not independent switches.

View research evidence and references

Published findings below are whole-bout estimates under specific study conditions. They are not values assigned to the activities above.

30-second maximal cycling [2]

Smith and Hill studied six men completing modified Wingate tests. Estimated whole-bout contributions were phosphagen 28%, glycolytic 56%, and aerobic 16%. Phosphagen power peaked in the first 5 seconds, glycolytic power at 10–15 seconds, and aerobic power in the final 5 seconds. These are study findings, not universal crossover times.

Simulated running events [3]

Spencer and Gastin studied 20 highly trained athletes. Estimated whole-bout aerobic contributions were 29% for 200 m, 43% for 400 m, 66% for 800 m, and 84% for 1500 m. A pathway's contribution at one moment differs from its accumulated contribution across the whole activity.

  1. Baker, McCormick & Robergs (2010). Interaction among Skeletal Muscle Metabolic Energy Systems during Intense Exercise. Review supporting overlap, rapid onset responses, and capacity limits.
  2. Smith & Hill (1991). Contribution of energy systems during a Wingate power test. DOI: 10.1136/bjsm.25.4.196.
  3. Spencer & Gastin (2001). Energy system contribution during 200- to 1500-m running in highly trained athletes. DOI: 10.1097/00005768-200101000-00024.