Capacity to handle physical and mental challenges on that day, based on nervous system balance and recovery.  Spren learns each user's unique baseline over time and adjusts continuously to guide training, recovery and personal lifestyle.

Baseline mental stress load, and risk for burnout.

Comparison of HRV, Recovery, and activity data collected via wearables/APIs to gauge if activity level is too low, ok, or too high.

Autonomic nervous system balance.  Shows whether the nervous system is leaning sympathetic (fight or flight) or parasympathetic (rest and digest).

Breaths per minute, derived from pulse wave data