Background

Teaching physiology in preclinical medical education demands not only conceptual knowledge but the capacity to construct causal explanatory frameworks linking physiological mechanisms to clinical outcomes [1]. Problem-Based Learning (PBL) has been proposed as a strategy to foster this integrative reasoning [2], yet evidence from first-year curricula — before formal cardiovascular instruction — remains scarce, particularly when assessed with instruments sensitive to causal integration [3]. Whether mechanistic understanding and causal integration develop as distinct cognitive constructs following PBL has not been directly tested.

Aims

To determine whether a brief, authentically-triggered PBL intervention improved two independent dimensions of physiological reasoning — mechanistic conceptual complexity (P1: cardiac pump model) and physiological cause–effect integration (P2: rationale for emergency cardiovascular intervention) — in first-year medical students prior to formal instruction.

Methods

A quasi-experimental pre–post study was conducted with 135 first-year medical students at the University of Málaga, before lecture-based cardiovascular teaching. The intervention comprised two face-to-face sessions (3 h each) in five small-group classes of 25–30 students, with cooperative teams of five, triggered by authentic video recordings of cardiovascular collapses in professional athletes (Eriksen, 2021; Hamlin, 2023). Written responses to two open-ended questions were independently coded by three raters using a validated five-level ordinal framework (N0–N4) assessing P1 and P2 separately (inter-rater κ = 0.39–0.52). Pre–post comparisons used Wilcoxon signed-rank tests; effect size r = Z/√N. Independence of P1 and P2 gains was assessed by Spearman correlation.

Results

After excluding non-evaluable responses, 130 students (96.3%) were included in conceptual analyses; all 135 for textual quality. For P1 (N = 130): Z = −4.683, p < 0.001, r = 0.41 (moderate effect); students at advanced levels (N3–N4) rose from 23.1% to 43.8%. For P2 (N = 130): Z = −7.723, p < 0.001, r = 0.68 (large effect); students at N3–N4 increased from 3.8% to 53.8% — a near-complete transformation of the cohort’s reasoning profile. Textual quality improved significantly (Z = −5.709, p < 0.001, r = 0.49; N = 135): 37.8% improved, 5.2% declined. Spearman correlation between P1 and P2 gains was r_s = 0.128 (p > 0.05), confirming their independence.

Conclusions

Two sessions of PBL centred on authentic cardiovascular cases produced large, independent gains in causal physiological reasoning before formal instruction. The effect size for P2 (r = 0.68) exceeds benchmarks reported in comparable PBL interventions [4]. The dissociation between mechanistic complexity and causal integration indicates these are distinct cognitive constructs requiring targeted pedagogical strategies, consistent with retention advantages reported for inquiry-based approaches in preclinical physiology [5].

Ethical approval

The study was approved by the Ethics Committee of the University of Málaga (CEUMA; ref. 187-2024-H) and conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all participants prior to inclusion.

Keywords: problem-based learning; physiology education; causal reasoning; preclinical medical education; conceptual progression