Search

The purpose of this study was to investigate the validity of a low-cost friction encoder against a criterion measure (strain gauge combined with a linear encoder) for assessing velocity, force and power in flywheel exercise devices. Ten young and physically active volunteers performed two sets of 14 maximal squats on a flywheel inertial device (YoYo Technology, Stockholm, Sweden) with five minutes rest between each set. Two different resistances were used (0.075 kg·m 2 for the first set; 0.025 kg·m 2 for the second). Mean velocity (V rep ), force (F rep ) and power (P rep ) for each repetition were assessed simultaneously via a friction encoder (Chronojump, Barcelona, Spain), and with a strain gauge combined with a linear encoder (MuscleLab 6000, Ergotest Technology, Porsgrunn, Norway). Results are displayed as (Mean [CI 90%]). Compared to criterion measures, mean bias for the practical measures of V rep , F rep and P rep were moderate (-0.95 [-0.99 to -0.92]), small (0.53 [0.50 to 0.56]) and moderate (-0.68 [-0.71 to -0.65]) respectively. The typical error of estimate (TEE) was small for all three parameters; V rep (0.23 [0.20 to 0.25]), F rep (0.20 [0.18 to 0.22]) and P rep (0.18 [0.16 to 0.20]). Correlations with MuscleLab were nearly perfect for all measures in all load configurations. Based on these findings, the friction encoder provides valid measures of velocity, force and power in flywheel exercise devices. However, as error did exist between measures, the same testing protocol should be used when assessing changes in these parameters over time, or when aiming to perform inter-individual comparisons.

Hip range of movement (ROM) impairments could affect individuals’ quality of life. The aim of this study is to describe a new flexometric method (FM) as a means to estimate hip ROM and to determine its concurrent validity and inter-rater and intra-rater reliability. Hip ROM was measured by performing the straight leg raise test (SLR) and hip abduction test (HA). The WIMU system is the gold standard. ROM was calculated in degrees using a trigonometric function based on values derived from measurements with a flexometer. The SLR and the HA showed high concurrent validity and good inter- and intra-rater reliability with an interclass correlation coefficient value that was at all times > 0.9. The minimal detectable change at the 90% confidence level for inter- and intra-rater reliability was equal to or greater than 5.7° in SLR-Right, 5.6° in SLR-Left, 5.1° in HA, 6.3° in SLR-Right, 4.9° in SLR-Left, and 5.4° in HA, respectively. This study suggests that the FM is a valid and reliable tool for assessing hip ROM. Due to its convenience and cost-effectiveness, this method could be widely used to measure the ROM of several joints in field-based tests.

The aim of this study was to identify between-position (forwards vs. backs) differences in movement variability in cumulative tackle events training during both attacking and defensive roles. Eleven elite adolescent male rugby league players volunteered to participate in this study (mean ± SD, age; 18.5 ± 0.5 years, height; 179.5 ± 5.0 cm, body mass; 88.3 ± 13.0 kg). Participants performed a drill encompassing four blocks of six tackling (i.e. tackling an opponent) and six tackled (i.e. being tackled by an opponent while carrying a ball) events (i.e. 48 total tackles) while wearing a micro-technological inertial measurement unit (WIMU, Realtrack Systems, Spain). The acceleration data were used to calculate sample entropy (SampEn) to analyse the movement variability during tackles performance. In tackling actions SampEn showed significant between-position differences in block 1 (p = 0.0001) and block 2 (p = 0.0003). Significant between-block differences were observed in backs (block 1 vs 3, p = 0,0021; and block 1 vs 4, p = 0,0001) but not in forwards. When being tackled, SampEn showed significant between-position differences in block 1 (p = 0.0007) and block 3 (p = 0.0118). Significant between-block differences were only observed for backs in block 1 vs 4 (p = 0,0025). Movement variability shows a progressive reduction with cumulative tackle events, especially in backs and when in the defensive role (tackling). Forwards present lower movement variability values in all blocks, particularly in the first block, both in the attacking and defensive role. Entropy measures can be used by practitioners as an alternative tool to analyse the temporal structure of variability of tackle actions and quantify the load of these actions according to playing position.