No abstract

No abstract

Eggers, TM, Massard, TI, Clothier, PJ, and Lovell, R. Measuring vertical stiffness in sport with accelerometers: Exercise caution! J Strength Cond Res 32(7): 1919-1922, 2018-This study aimed to determine the measurement accuracy of triaxial accelerometers, to determine vertical stiffness (Kvert) during overground running, and to examine the influence of device location. Seventeen healthy adults wore 2 triaxial accelerometers (positioned between scapulae and at lumbar spine) during a 2-minute continuous 20-m shuttle run (12 km·h), which was repeated 7 days later. Accelerometer-derived Kvert data were compared with that calculated from corresponding force-plate ground contacts (criterion measure). Moderate correlations (r = 0.65-0.66) between the accelerometer and criterion measure were identified, irrespective of unit location. However, accelerometer-determined Kvert had questionable reliability in both positions (intraclass correlation coefficient = 0.70-0.71). These results suggest caution be taken when using accelerometer-derived Kvert during overground running.

Purpose: To assess the impact of microcycle (MC) structures on physical and technical performances in rugby league training and matches. Methods: Thirty-four professional rugby league players were monitored during all training sessions and matches across a single season wherein 2 different competition-phase MC structures were implemented. The first MC structure involved the first session on match day (MD) + 2 and the main stimulus delivered MD − 3, and the second structure delayed all sessions by 1 day (first session on MD + 3 and main session MD − 2; MC structure in the second half of the season). Physical output was quantified via relative total speed (in meters per minute), high-speed running (per minute; ≥4.0 m·s−1), and very-high-speed running (per minute; ≥5.5 m·s−1), measured using a global positioning system (10 Hz) in addition to accelerometer (100 Hz) metrics (PlayerLoad per minute and PlayerLoadslow per minute]) during training and matches. Technical performance (number of runs, meters gained, tackles made and missed) was recorded during matches. Generalized linear mixed models and equivalence tests were used to identify the impact of MC structure on physical and technical output. Results: Nonequivalent increases in meters per minute, high-speed running per minute, and PlayerLoad per minute were observed for the first training stimulus in MC structure in the second half of the season with no practical difference in midcycle sessions observed. The MC structure in the second half of the season structure resulted in increased high-speed running per minute and decreased PlayerLoadslow per minute during MD with no differences observed in technical performance. Conclusions: Delaying the first training stimulus of the MC allowed for greater training load accumulation without negative consequences in selected match running and technical performance measures. This increased MC load may support the maintenance of physical capacities across the in-season.