Nutraceutical Periodization for eXercise (NPX): Matching Bioactives to Training Load, Recovery Demand, and Adaptation Windows

Nutraceuticals are evaluated as though efficacy were a stable ingredient property, although net value may vary with exercise stimulus, exposure schedule, recovery pressure, athlete state, and prioritized outcome. This structured narrative review integrates exercise-adaptation biology, periodized sports nutrition, training-load and recovery models, precision nutrition, and human evidence for sport-relevant interventions. Searches of PubMed/MEDLINE, Web of Science, and Scopus were updated through August 2026 and supplemented by citation tracking. General efficacy was separated from direct evidence of timing, context, or state modification. Nutraceutical Periodization for eXercise (NPX) is an allocation layer applied only after safety, legality, product quality, and plausible efficacy are established. It defines four non-sequential functional windows—performance exploitation, adaptation-permissive signaling, restoration, and resilience—and separates intervention strategy, training context, athlete state, and outcome hierarchy. Four falsifiable propositions test context modification, temporal allocation, bottleneck/state dependence, and whole-policy utility. None of the allocation claims in the present evidence map met the criterion for direct NPX allocation evidence. NPX therefore formalizes hypothetical allocation rules rather than an established supplementation policy; proposed improvements in athlete-centered outcomes or equivalent outcomes with less exposure, burden, or harm remain to be prospectively tested against an explicitly defined active evidence-based comparator. Interaction and policy trials are needed to establish the value and boundaries of these rules.