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The ability to generate force in the lower body can be considered a performance factor in sports. This study aims to analyze the test–retest and between-device reliability related to the location on the body of the inertial measurement unit Vmaxpro for the estimation of vertical jump. Eleven highly trained female athletes performed 220 countermovement jumps (CMJ). Data were simultaneously captured by two Vmaxpro units located between L4 and L5 vertebrae (hip method) and on top of the tibial malleolus (ankle method). Intrasession reliability was higher for ankle (ICC = 0.96; CCC = 0.93; SEM = 1.0 cm; CV = 4.64%) than hip (ICC = 0.91; CCC = 0.92; SEM = 3.4 cm; CV = 5.13%). In addition, sensitivity was higher for ankle (SWC = 0.28) than for the hip method (SWC = 0.40). The noise of the measurement (SEM) was higher than the worthwhile change (SWC), indicating lack of ability to detect meaningful changes. The agreement between methods was moderate (rs = 0.84; ICC = 0.77; CCC = 0.25; SEM = 1.47 cm). Significant differences were detected between methods (−8.5 cm, p < 0.05, ES = 2.2). In conclusion, the location of the device affects the measurement by underestimating CMJ on ankle. Despite the acceptable consistency of the instrument, the results of the reliability analysis reveal a significant magnitude of both random and systematic error. As such, the Vmaxpro should not be considered a reliable instrument for measuring CMJ. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the validity and reliability of the rear foot elevated split squat (RFESS) 5 repetition maximum (5RM) test as a field method for measuring unilateral leg strength symmetry. As a validated method of testing symmetry, the RFESS 5RM may be used by strength and conditioning coaches and sports medicine staff to measure the presence of imbalances with minimal equipment and time. Twenty-six subjects (age = 23.8 ± 4.6 years, mass = 88.1 ± 10.7 kg, and height = 1.79 ± 0.1 m) with a minimum 2 years of strength and conditioning experience were recruited. After a familiarization session, subjects performed an incremental 5RM protocol on both legs, on 2 occasions where 3D motion and force data were collected. Moderate reliability of bar load symmetry was found between test and retest conditions correlation (intraclass coefficient = 0.73, 0.33-0.91) with no proportional bias between sessions. Validation of the exercise was analyzed using a correlation between asymmetries in mean set vertical ground reaction forces (vGRF) of the lead foot during the concentric phase, with bar load. When all maximal trials, from both test conditions, were analyzed, a most likely large positive correlation (0.57, 0.30-0.76) was found for mean set concentric lead foot vGRF. When a threshold level of load symmetry (96.54-103.46%) was applied, a most likely large positive correlation (r = 0.59, 0.14-0.84) between symmetry in lead foot vGRF was found in subjects who exceeded this limit. Conversely, analysis of subjects within the threshold produced unclear correlations. Findings of this study suggest the RFESS is a valid and reliable measure of unilateral leg strength symmetry. Practitioners are recommended to use this exercise to investigate the strength symmetry of athletes, but are guided to note that a threshold level of symmetry (96.54-103.46%) may be required to have been exceeded to indicate a true difference in vGRF production. [ABSTRACT FROM AUTHOR]

Tibial acceleration is a surrogate measure for impact loading and lower limb fatigue injury in runners. Triaxial accelerometers may offer reliable and practical measurement of resultant peak tibial acceleration (PTA). With such potential in mind, this study examined variability and measurement reliability of tibial acceleration in 14 runners at baseline at one week, and eight of the runners again at six months. Triaxial accelerometers were attached to the distal tibiae of runners before they ran on a treadmill for two minutes each, at speeds of 2.7, 3.0, 3.3 and 3.7 m/s in standardised shoes. Resultant PTAs were calculated for each speed and session. Reliability outcomes were presented as percentage change and effect sizes. Variability outcomes included intraclass correlation coefficients and the typical error of the measurement. Smallest worthwhile change and performance/noise ratio were also calculated. While runners demonstrated marginally lower reliability and higher variability over six months, compared to one week, in all cases the measures of reliability and variability were of ‘good’ to ‘moderate’ reliability, and ‘small’ to ‘moderate’ variability using magnitude-based inferences. We can be confident that resultant PTA can be used with runners to assess and monitor their impacts throughout a six-month intervention. [ABSTRACT FROM AUTHOR]

Tibial acceleration is a surrogate measure for impact loading and lower limb fatigue injury in runners. Triaxial accelerometers may offer reliable and practical measurement of resultant peak tibial acceleration (PTA). With such potential in mind, this study examined variability and measurement reliability of tibial acceleration in 14 runners at baseline at one week, and eight of the runners again at six months. Triaxial accelerometers were attached to the distal tibiae of runners before they ran on a treadmill for two minutes each, at speeds of 2.7, 3.0, 3.3 and 3.7 m/s in standardised shoes. Resultant PTAs were calculated for each speed and session. Reliability outcomes were presented as percentage change and effect sizes. Variability outcomes included intraclass correlation coefficients and the typical error of the measurement. Smallest worthwhile change and performance/noise ratio were also calculated. While runners demonstrated marginally lower reliability and higher variability over six months, compared to one week, in all cases the measures of reliability and variability were of ‘good’ to ‘moderate’ reliability, and ‘small’ to ‘moderate’ variability using magnitude-based inferences. We can be confident that resultant PTA can be used with runners to assess and monitor their impacts throughout a six-month intervention. [ABSTRACT FROM AUTHOR]