The psychobiology of post-exercise recovery: an exploratory pilot study on 48-hour plasma irisin change and state anxiety in trained males

Understanding the interplay between physiological stress and psychological recovery following intense exercise is crucial for optimising training adaptations and well-being. Muscle-derived myokines may represent biological correlates of this process, yet the association between irisin and affective responses during post-resistance-training recovery remains poorly understood. This exploratory study investigated the temporal dynamics of plasma irisin, creatine kinase (CK), and psychological states (state anxiety, positive/negative affect) in eight resistance-trained males before, and at 15 min, 24, and 48 h after a single, high-volume resistance training session controlled via repetitions-in-reserve. The findings suggested a temporal dissociation between muscular stress markers and the irisin response. While plasma CK peaked at 24 h, indicating a marked muscular stress response, plasma irisin exhibited a modest but significant increase only at the 48-hour time point. Importantly, 48-hour changes in plasma irisin were significantly and negatively associated with late changes in state anxiety from 24 to 48 h post-exercise. These preliminary findings suggest that plasma irisin may also exhibit later-phase variation, in addition to its established acute response in other exercise modalities. It is hypothesised that this 48-hour irisin variation may track alongside longer-term homeostatic restoration. These observations are exploratory and hypothesis-generating; rather than acting as a direct causal mediator, 48-hour changes in plasma irisin may be associated with inter-individual trajectories of late state anxiety during recovery, providing a novel framework for future investigations.