The Gait Signature of Frailty: Transfer Learning based Deep Gait Models for Scalable Frailty Assessment

Abstract

Frailty is a condition in aging medicine characterized by diminished physiological reserve and increased vulnerability to stressors. However, frailty assessment remains subjective, heterogeneous, and difficult to scale in clinical practice. Gait is a sensitive marker of biological aging, capturing multisystem decline before overt disability. Yet the application of modern computer vision to gait-based frailty assessment has been limited by small, imbalanced datasets and a lack of clinically representative benchmarks. In this work, we introduce a publicly available silhouette-based frailty gait dataset collected in a clinically realistic setting, spanning the full frailty spectrum and including older adults who use walking aids. Using this dataset, we evaluate how pretrained gait recognition models can be adapted for frailty classification under limited data conditions. We study both convolutional and hybrid attention-based architectures and show that predictive performance depends primarily on how pretrained representations are transferred rather than architectural complexity alone. Across models, selectively freezing low-level gait representations while allowing higher-level features to adapt yields more stable and generalizable performance than either full fine-tuning or rigid freezing. Conservative handling of class imbalance further improves training stability, and combining complementary learning objectives enhances discrimination between clinically adjacent frailty states. Interpretability analyses reveal consistent model attention to lower-limb and pelvic regions, aligning with established biomechanical correlates of frailty. Together, these findings establish gait-based representation learning as a scalable, non-invasive, and interpretable framework for frailty assessment and support the integration of modern biometric modeling approaches into aging research and clinical practice.

Figures (3)

• Figure 1: (a) The Fried frailty phenotype defined by five clinical criteria, with mobility impairment, particularly slow gait speed as a core marker of physical frailty. (b) Conceptual trajectory of age-related physical frailty, highlighting gait deterioration as a primary functional manifestation. (c) Summary of demographic characteristics of the study cohort stratified by gender.
• Figure 2: Exemplar of gradient activation maps for best performing models. Rows 1 and 2: SwinGait M2 and its corresponding GradCAM, Rows 3 and 4: DeepGait D1 and its corresponding GradCAM.
• Figure 3: Overview of the proposed frailty assessment framework. (a) In-clinic RGB videos are converted to privacy-preserving silhouette sequences using Detectron2. (b) Two transfer-learning backbones, DeepGaitV2 and SwinGait, extract gait representations for frailty prediction. In DeepGaitV2, the Basic Block 2D consists of two spatial convolution layers with batch normalization and ReLU activation, followed by an identity shortcut, while the Basic Block P3D replaces full 3D convolution with a pseudo-3D design composed of spatial and temporal convolutions, optional downsampling, synchronized batch normalization, and a 3D residual shortcut. (c) Clinician-facing interpretation of the predicted frailty status and potential downstream applications, including screening, longitudinal monitoring, and care planning.