Proportionality of energy‑system adaptation to contribution and strain

Establish whether, in the proposed three-dimensional impulse–response model for training adaptation, the alactic (phosphocreatine/immediate), lactic (glycolytic), and aerobic (oxidative) energy systems adapt in proportion to their contributions to energy turnover, scaled by the magnitude of strain as quantified by the strain score (SS).

Background

The three-dimensional impulse–response model posits separate adaptation pathways for the three energy systems and uses a strain-based training load (SS) to drive fitness changes. A key modeling assumption is that each system’s adaptation is proportional to its contribution to power (i.e., energy turnover) and amplified by the accrued strain.

The authors note that this proportionality assumption has not yet been empirically verified, indicating that direct experimental validation is required to determine whether system-specific adaptations scale with system-specific contributions and measured strain.