System Engagement Explained: How Much Is Left in the Tank?

In this episode of The Athletes Compass, Paul Warloski, Dr. Paul Laursen, and Marjaana Rakai explain Athletica’s Workout Reserve and the new Systems Engagement feature. Workout Reserve is described as a battery-like metric that shows how close an athlete is to their historical best across different durations, from short sprint efforts to long aerobic performances. The team discusses how athletes can use it in real time through Velocity or Garmin, how negative values can signal breakthrough efforts, and why good historical data is essential. They also explain how Systems Engagement helps athletes and coaches see which physiological systems were stressed in a workout or race, making it easier to reverse engineer training toward the actual demands of an event.Key episode takeawaysWorkout Reserve acts like a “battery” showing how much capacity an athlete has left relative to their recent historical bests.A value near 100% suggests the athlete is fresh relative to that effort, while 0% means they are approaching a known personal limit. Negative values indicate new, uncharted territory.Workout Reserve can be viewed retrospectively in Athletica, live in Velocity sessions, or through the Garmin Workout Reserve data field.Systems Engagement shows which energy systems were stressed during a workout or selected segment, such as neuromuscular sprint, anaerobic, VO2 max, threshold, or aerobic systems.A 30/30 interval session may engage both VO2 max and threshold systems, which matches the expected training adaptations.The tool is most useful when athletes have enough valid historical data, including power or pace tests such as FTP tests, 5K tests, or sport-specific calibration sessions.Workout Reserve and Systems Engagement are based on external load, such as pace or power, not internal load measures like heart rate, lactate, or RPE.Coaches can use Systems Engagement to check whether an athlete actually trained the intended system.Race analysis can help athletes identify which physiological systems were most taxed, then design training to target those demands.Not every session should push Workout Reserve to zero or negative; easy aerobic sessions still have a purpose.How a ProTour cycling coach uses Athletica Workout ReserveWorkout Reserve: A New Way to Understand Performance with Dr. Andrea ZignoliScientific Paper in Sports EngineeringRace Analysis - Volta ValencianaGarmin Connect IQ | HomeTrain and Race with WR on GarminAthletica Workout Reserve | HomePaul Warloski - Simple Endurance CoachingMarjaana Rakai | Nordic Performance Lab