Timing rehabilitation according to chronotype: An overlooked variable?

Hand injuries frequently cause significant functional limitations, and patient engagement plays a crucial role in rehabilitation outcomes. Chronotype represents an individual's inherent preference for activity timing and has been linked to variations in physical performance, pain sensitivity, and cognitive abilities; yet its impact within rehabilitation contexts remains insufficiently studied. This study aimed to investigate whether functional performance, pain, edema, and therapist-rated participation during the morning and afternoon rehabilitation sessions differ according to patients' chronotypes following hand injuries. A prospective observational study was conducted with 46 patients (mean age 39.9 ± 17.1 y) undergoing hand rehabilitation. Chronotype was assessed using the Morningness-Eveningness Questionnaire, and each participant attended two rehabilitation sessions on consecutive days - one in the morning (09:00) and one in the afternoon (16:00). Outcome measures included grip strength, the Nine-Hole Peg Test (NHPT), the Visual Analog Scale (VAS) for pain, physiotherapist-rated VAS for participation, metacarpophalangeal (MCP) joint circumferential edema, and QuickDASH scores. Data were analyzed using a three-way mixed-model repeated-measures ANOVA. Chronotype distribution was 41.3% morning-type, 45.7% intermediate-type, and 13.0% evening-type. Morning and intermediate types demonstrated significantly better NHPT performance in the morning sessions (p < 0.05), whereas evening types showed numerically better performance in the afternoon sessions, although this difference did not reach statistical significance. Intermediate and evening types exhibited significantly higher pain VAS scores in the afternoon sessions (p < 0.01). No significant chronotype-related differences were observed in grip strength, edema, or participation scores. This study is among the first to examine the effects of chronotype on hand injury rehabilitation. The findings suggest that scheduling rehabilitation in alignment with a patient's chronotype may enhance functional performance. However, to generalize these findings, studies with larger sample sizes, more homogeneous chronotype distributions, long-term follow-up, and inclusion of cognitive function assessments are needed.