Integrated exercise physiology showing muscle fibers, metabolism, heart rate, and VO2 max

Energy Systems, Heart Rate & VO2 Max

Connect muscle fibers, biomechanics, energy systems, heart rate, VO2 max, and resistance-training variables into one exercise-science framework.

Athletic metabolism and energy-system pathways

Metabolism & Energy Systems for Exercise

Understand ATP and the major energy pathways that support explosive power, high-intensity exercise, endurance, and recovery.

Heart rate training zones for recovery, endurance, tempo, and high-intensity work

Heart Rate Zones: Training by Intensity

Learn how resting heart rate, maximum heart rate, heart-rate reserve, and training zones can help organize recovery, endurance, tempo, and high-intensity workouts.

ATP production and the phosphagen, glycolytic, and oxidative energy pathways during exercise

ATP & Energy Systems in Exercise

Learn how ATP powers muscle contraction and how the phosphagen, glycolytic, and oxidative pathways overlap to meet changing exercise demands.

VO2 max infographic for aerobic fitness and endurance performance

VO2 Max: Aerobic Capacity & Training

Learn what VO2 max measures, how oxygen intake, transport, and utilization work together, and how aerobic-power training can improve performance.