Bioenergetic Pathways and Energy System Contributions

A collection of vocabulary flashcards covering bioenergetic energy pathways, metabolic enzymes, event duration continuums, exercise physiology research metrics, and modulating factors.

Phosphagen (ATP-PCr) System

The fastest anaerobic bioenergetic pathway, relying on stored adenosine triphosphate (ATP) and phosphocreatine (PCr) in muscle tissue to rapidly resynthesize ATP without requiring oxygen or producing lactate, dominant in maximal efforts lasting roughly $5-15\,s$.

Creatine Kinase

The enzyme that rapidly transfers a high-energy phosphate from phosphocreatine (PCr) to ADP to resynthesize ATP when ATP is hydrolyzed to $\text{ADP} + \text{P}_i$ to power muscle contraction.

Glycolytic (Lactic Acid) System

An anaerobic pathway that breaks down glucose or glycogen to pyruvate (converted to lactate and $\text{H}^+$ under insufficient oxygen), supplying energy for high-intensity efforts lasting roughly $15\,s$ to $2-3\,\text{minutes}$.

Aerobic (Oxidative) System

The oxygen-dependent bioenergetic pathway that fully oxidizes carbohydrates, fats, and proteins in the mitochondria via the Krebs cycle and electron transport chain, offering the greatest ATP capacity for continuous efforts lasting longer than $2-3\,\text{minutes}$.

100-Meter Sprint Energy Contribution

The proportional energy breakdown during a $100\,m$ sprint running event, accounting for approximately $61-70\%$ total energy expenditure from the ATP-PCr system, $\sim 23\%$ from the glycolytic system, and as low as $9\%$ from oxidative input (Park et al., 2021; Saleh & Aga, 2025).

15-Second Sprint Energy Breakdown (Speed-Power Athletes)

The energy distribution during a $15\,s$ all-out sprint in speed-power athletes, deriving $45\%$ of energy from phosphagen, $48\%$ from glycolysis, and $7\%$ from aerobic pathways (Archacki et al., 2024).

Glycolytic Power Peak

The point during a sprint, identified at approximately $6\,s$ into the effort by Briand et al. (2025), which coincides with the transition from acceleration to deceleration.

Middle-Distance Energy Shift

The progressive decline in anaerobic energy contribution across middle distances, dropping from $62-63\%$ in $400\,m$ running to $33-39\%$ in $800\,m$, and further down to $17-20\%$ in $1500\,m$ (Hill, 1999; Saleh & Aga, 2025).

Bioenergetic Crossover Point

The maximal effort duration of approximately $75\,s$ identified by Tortu et al. (2024), where equal energy contribution ($50\%$ each) is derived from aerobic and anaerobic systems.

3000 m Run Energy Breakdown

The energy system contribution during a $3000\,m$ run, consisting of $\sim 6\%$ from ATP-PCr (via EPOC), $\sim 6\%$ from glycolysis, and $\sim 68\%$ from the oxidative system (Saleh & Aga, 2025).

Carbohydrate Oxidation Efficiency Advantage

The $7\%$ higher efficiency of aerobic ATP production from carbohydrate compared to fat, which causes fuel utilization to shift toward carbohydrate at exercise intensities approaching $80-100\%\,\text{VO}_2\text{max}$ (Hargreaves & Spriet, 2020).

Repeated Sprint Protocol Adaptation

The metabolic shift during repeated sprints where glycolytic contribution drops from $\sim 36\%$ in the first five sprints to below $7\%$ by sprints 11–15, while oxidative contribution rises to $33\%$ (Ulupınar et al., 2024).

Athlete Specialization Bioenergetic Shift

The shift in energy system contributions during a $15\,s$ sprint where endurance athletes derive $47\%$ of energy from phosphagen and $12\%$ from aerobic sources, compared to speed-power athletes who derive $45\%$ from phosphagen and $7\%$ from aerobic sources (Archacki et al., 2024).

Sex Influence on Energy Systems

The observation that sex does not significantly alter the relative proportions of energy system contribution during sprint exercise, despite differences in absolute energy expenditure between male and female athletes (Archacki et al., 2024).

Intermittent Ice Hockey Energy Contribution

The phenomenon where the oxidative system contributes $63\%$ of energy during repeated high-intensity ice hockey shifts, despite the intermittent sprint nature of the sport (Gabrys et al., 2026).