Subject-specific sensitivity of several biomechanical features to fatigue during an exhaustive treadmill run.

The aim of the present study was to examine the sensitivity of several movement features during running to exhaustion in a subject-specific setup adopting a cross-sectional design and a machine learning approach. Thirteen recreational runners, that systematically trained and competed, performed an exhaustive running protocol on an instrumented treadmill. Respiratory data were collected to establish the second ventilatory threshold (VT2) in order to obtain a reference point regarding the gradual accumulation of fatigue. A machine learning approach was adopted to analyze kinetic and kinematic data recorded for each participant, using a random forest classifier for the region pre and post the second ventilatory threshold. SHapley Additive exPlanations (SHAP) analysis was used to explain the models' predictions and to provide insight about the most important variables. The classification accuracy value of the models adopted ranged from 0.853 to 0.962. The most important feature in six out of thirteen participants was the angular range in AP axis of upper trunk C7 (RTAPu) followed by maximum loading rate (RFDmaxD) and the angular range in the LT axis of the C7. SHAP dependence plots also showed an increased dispersion of predictions in stages around the second ventilatory threshold which is consistent with feature interactions. These results showed that each runner used the examined features differently to cope with the increase in fatigue and mitigate its effects in order to maintain a proper motor pattern.

A Comparative Analysis of Symmetry Indices for Spatiotemporal Gait Features in Early Parkinson's Disease.

This study compared the five most commonly used equations for calculating gait symmetry in discrete variables among Parkinson's disease patients. Twelve patients (five women and seven men) performed ten consecutive gait trials on a 10 m walkway. Gait data were collected using eight optoelectronic cameras (100 fr/s). The analysis focused on various spatiotemporal parameters, including cadence, step time, stride time, single support, double support, walking speed, step length, stride length, step width, and foot angle. Five symmetry indices were calculated for each trial rather than averaging the ten recorded trials. The variability in and reliability of each symmetry equation were assessed using the coefficient of variation (CV) and intraclass correlation coefficient (ICC), respectively. Additionally, Bland-Altman plots were produced to visualize the agreement between each pair of methods for each spatiotemporal parameter. The results revealed that the symmetry ratio method exhibited lower variability and higher reliability compared with the other four indices across all spatiotemporal gait parameters. However, it was found that the reliability of a single trial was generally poor, regardless of the symmetry calculation formula used. Therefore, we recommend basing measurements of gait asymmetry in Parkinson's disease on multiple trials.

Acute effect of front crawl sprint resisted swimming on the propulsive forces of the hand.

The purpose of the current study was to investigate the acute effect of sprint resisted front crawl swimming on the propulsive forces of the hand. Eight female swimmers swam 25 m with maximal intensity, with and without added resistance. A bowl with a capacity of 2.2, 4 and 6 L was used as low, moderate and high added resistance, respectively. The underwater motion of the swimmer's right hand was recorded using 4 cameras (60 Hz) and the digitization was undertaken using the Ariel Performance Analysis System. Repeated-measures ANOVA revealed that the velocity of the hand, the pitch and the sweepback angles of the hand, as well as the magnitude and the relative contribution of the drag and lift forces were not significantly modified and thus the magnitude of the resultant force did not change. Moreover, the magnitude of the effective force, as well as the angle formed between the resultant force and the axis of the swimming propulsion were not significantly affected. Thus, it could be concluded that resistance added as in this study did not alter the pattern of the propulsive hand forces associated with front crawl sprinting.