Radiomic analysis reveals exercise-induced textural changes in the heel fat pad macrochamber layer

The heel fat pad plays a vital role in shock absorption during weight-bearing and may exhibit structural and textural differences associated with long-term mechanical loading. This study employed ultrasound radiomics to investigate the association between exercise volume and layer-specific radiomic features of the macrochamber and microchamber layers of the heel fat pad. Ultrasound images were obtained from 51 healthy young adults aged 18-35 years, who were classified into high-exercise-volume (HEV, n = 18), moderate-exercise-volume (MEV, n = 15), and low-exercise-volume (LEV, n = 18) groups according to weekly physical activity energy expenditure. A total of 101 radiomic features were extracted from each layer to characterize intensity, heterogeneity, and spatial texture patterns. Intergroup differences were analyzed using one-way analysis of variance or the Kruskal-Wallis test, followed by Bonferroni-adjusted pairwise comparisons. Significant radiomic differences were identified in the macrochamber layer, with 19 features differing among the three groups (P < 0.05), and six representative features retained after LASSO feature selection. The main pairwise differences occurred between the LEV group and the MEV or HEV groups, whereas no significant differences were detected between the MEV and HEV groups in the main distinguishing features. In contrast, the microchamber layer showed limited variation, with only Uniformity differing significantly between the LEV group and the MEV/HEV groups. These findings suggest that the macrochamber layer may be more sensitive to activity-associated radiomic texture differences than the microchamber layer. Overall, ultrasound radiomics shows potential as a non-invasive approach for quantifying subtle, layer-specific texture patterns in the heel fat pad.