Background: Spinal cord injuries (SCIs) cause debilitating secondary conditions such as severe muscle deterioration, cardiovascular, and metabolic dysfunctions, significantly impacting patients’ quality of life. Functional electrical stimulation (FES) combined with cycling exercise (FES-cycling) has shown promise in improving muscle function and health in individuals with SCI. Objective: This pilot study aimed to investigate the potential role of multiparametric magnetic resonance imaging (MRI) to assess muscle health during and after an FES-cycling rehabilitation program. Methods: Four male participants with chronic SCI underwent a 6-month FES-cycling training program, consisting of two 30-minute sessions per week. MRI scans were performed at baseline (T₀), after 3 months (T₁), at the end of the training (T₂), and 1-month posttraining (T₃). The MRI protocol included T₁-weighted imaging for volume quantification, Dixon imaging for fat fraction, multi-echo spin echo for T₂ relaxation times, and diffusion tensor imaging to assess diffusion parameters. Results: Muscle hypertrophy was observed, with an average increase in muscle volume of 22.3% at T₁ and 36.7% at T₂ compared with baseline. One month posttraining, muscle volume remained 23.2% higher than baseline. Fat fraction decreased from 11.1% at T₀ to 9.1% at T₂, with a rebound to 10.9% at T₃. T₂ relaxation times showed a reduction even though this was not consistent among participants. Diffusion tensor imaging parameters revealed subtle changes in muscle tissue microstructure, with a decrease in fractional anisotropy mainly associated to an increase of radial diffusivity. Conclusions: Although preliminary, this study provides evidence that 6 months of low-intensity FES-bike training can increase muscle volume and decrease fat infiltration in individuals with SCI. The study demonstrates that the use of a multiparametric MRI provides comprehensive insights into both macroscopic and microscopic changes within muscle tissues, supporting its integration into clinical practice for assessing the efficacy of rehabilitation interventions.

Road irregularities generate vibrations that are transmitted to cyclists’ hands. This paper describes a purpose-designed laboratory setup and data processing method to assess vibration-induced numbness and discomfort. The rear wheel of a road bike was coupled with a smart trainer for indoor cycling, while the front wheel was supported by a vibrating platform to simulate road–bike interaction. The vibrotactile perception threshold (VPT) is measured in the fingers, and a questionnaire was used to assess the discomfort in different parts of the hand using a unipolar scale. To validate the method, ten male volunteers underwent two one-hour cycling sessions, one for each of the two handlebar designs tested. VPT was measured in the index and little fingers of the right hand at 8 and 31.5 Hz before and after each session, while the discomfort questionnaire was completed at the end of each session. The discomfort scores showed a strong inter-subject variability, indicating the necessity to combine them with the objective measurements of the VPT, which is shown to be sensitive in identifying the perception shift due to vibration exposure and the differences between the fingers. This study demonstrates the effectiveness of the proposed method for assessing hand numbness and discomfort in cyclists.

Transport operators face increased risks of injuries and falls while walking on a vibrating floor. No standards exist for human exposure to foot-transmitted vibration (FTV). In this study, twenty-one subjects walked on a treadmill constrained on a moving platform used to apply harmonic vibrations in four directions (mediolateral, anteroposterior, roll, and pitch) at four frequencies (0.5, 0.75, 1, and 1.5 Hz) with constant displacement (2 cm or 1°). The gait metrics, kinematic, and stability data were extracted in correspondence with the onset/offset of platform movement and when the steady-state of FTV was reached. Mediolateral vibration at the highest frequency was the most impactful condition, leading to the adoption of compensatory strategies to stabilize the center of mass closer to the floor and enlarge the base of support. These findings suggest that, from a normative perspective, a specific weighting curve is needed to assess human response to FTV while walking, since it varies as a function of vibration frequency and direction.

Background: This study investigated the vibrotactile perception threshold (VPT) changes in the fingers and toes of twenty-eight healthy subjects (15 males and 13 females aged 20 to 62 years) exposed to hand- and foot-transmitted vibration. Methods: The VPT was measured before and after the exposure of the hands and feet to 5 minutes of triaxial white noise pseudorandom vibration. The post-vibration VPT was measured immediately after and 15 minutes after the end of the exposure to assess the temporary threshold shift (TTS) of vibration perception. The effects of the anatomical district (index finger and big toe), measurement time (before and after vibration exposure), test frequency (8, 31.5, and 125 Hz), age group (Under30s and Over 40s), and gender (male and female) on the changes in VPT were investigated. Results: The findings revealed that the index finger and the big toe exhibited comparable profiles in the vibrotactile sensitivity at the low-middle vibration frequencies and in the recovery of the perception threshold after vibration exposure. The big toe showed a higher perception threshold than the index finger, and the difference increased with the test frequency. In addition to vibration frequency, age and skin temperature influenced the results of VPT and TTS measurements. Conclusions: The findings of this study can contribute to outlining alternative frequency weighting functions for the neurosensory response of the hand and foot to vibration exposure, and to update the current guidelines for evaluating human vibration exposure.

The Cybathlon is a unique international competition platform for evaluating assistive technologies under real-life conditions. In the most recent edition,

Running-specific prostheses are widely used in Paralympic sport and their performance assessment under real running conditions requires wearable monitoring systems capable of capturing both prosthesis dynamics and athlete kinematics. Existing solutions have been validated in laboratory settings and short trials, leaving open challenges related to autonomy, robustness, and applicability to prolong outdoor running. This study aimed to design and evaluate a wearable IMU-based monitoring system for assessing prosthesis dynamics and athlete kinematics during long-distance running. Four IMU sensors mounted on prosthetic blades and sockets were deployed, addressing practical constraints of battery life, memory, and outdoor robustness. The system was tested during a 35 km trail running race by a former Paralympic athlete with bilateral transtibial amputation. The race course was segmented into nine slope-based sectors, and stride-level metrics, including impact acceleration, vibration peak, damping ratio, and damped natural frequency, were extracted from blade-mounted IMU data and compared across sectors using non-parametric statistics and effect size measures. The results suggest that the proposed system may capture meaningful variations in prosthesis dynamics across different running conditions, with moderate to large effect sizes observed for most metrics. These preliminary findings support the feasibility of the proposed approach for in-field prosthesis monitoring.