Modelling the relationships between volume, intensity and injury-risk in professional rugby league players

Objective This study aimed to: (a) identify the association between external-workloads and injury-risk in the subsequent week; and (b) understand the effectiveness of workload variables in establishing injury-risk. Design Retrospective cohort study. Methods Workload and injury data (soft-tissue) were collected from forty-eight professional male rugby league players. Load variables included duration (min), total distance (m), relative distance (m min−1), high speed distance ([m]>20 km h−1), very-high speed distance ([m]>25 km h−1), acceleration and deceleration efforts (count) and PlayerLoad (Arbitrary Unit: AU). Cumulative two-, three- and four-weekly loads; Acute:Chronic Workload Ratio (ACWR); Mean-Standard Deviation Workload Ratio (MSWR) and strain values were calculated and divided into three equally-sized bins (low, moderate and high). Generalised Estimating Equations analysed relationships between workload variables and injury probability in the subsequent week. Results Injury-risk increased alongside increases in the ACWR for duration, total distance and PlayerLoad. Conversely, injury-risk decreased (Area Under Curve: 0.569–0.585) with increases in the four-weekly duration, total distance, accelerations, decelerations and PlayerLoad. For relative distance, high four-weekly workloads (high: >60 m min−1) demonstrated a positive association with injury-risk, whilst high two-weekly loads (high: >82 m min−1) were negatively associated. Conclusions A range of external workload metrics and summary statistics demonstrate either positive or negative associations with injury-risk status. Such findings provide the framework for the development of decision-support systems in which external workload metrics (e.g. total or high speed distance) can be uniquely and routinely monitored across a range of summary statistics (i.e. cumulative weekly loads and ACWR) in order to optimise player performance and welfare

Differences in the Kinematics of the Baseball Swing between Hitters of Varying Skill

Purpose: The aim of this study was to determine differences in bat swing kinematics in baseball hitters of varying ability. Methods: Kinematic data for the upper and lower body were collected from 20 trained male baseball players (22.3 ± 5.3 yr, 1.82 ± 0.07 m, 83.5 ± 10.9 kg), using three-dimensional computerized motion-analysis techniques. Participants were ranked before testing based on a novel coach's rating scale and seasonal batting average. They were subsequently separated into a relatively high-caliber group of hitters (n = 10) and a relatively low-caliber group of hitters (n = 10) for comparison. Importantly, the two groups were significantly different in terms of coach's rating (