No abstract

This systematic review and meta-analysis aimed to analyse the technologies and main training variables used in the literature to monitor flywheel training devices in real time. In addition, as the main research question, we investigated how eccentric overload can be effectively monitored in relation to the training variable, flywheel shaft type device and the moment of inertia selected. The initial search resulted in 11,621 articles that were filtered to twenty-eight and seventeen articles that met the inclusion criteria for the systematic review and meta-analysis, respectively. The main technologies used included force sensors and rotary/linear encoders, mainly to monitor peak or mean force, power or speed. An eccentric overload was not always achieved using flywheel devices. The eccentric overload measurement was related to the main outcome selected. While mean force (p = 0.011, ES = -0.84) and mean power (p < 0.001, ES = -0.30) favoured the concentric phase, peak power (p < 0.001, ES = 0.78) and peak speed (p < 0.001, ES = 0.37) favoured the eccentric phase. In addition, the lower moments of inertia (i.e., from 0.01 to 0.2 kg·m 2 ) and a cylindrical shaft type (i.e., vs conical pulley) showed higher possibilities to achieve eccentric overload. A wide variety of technologies can be used to monitor flywheel devices, but to achieve eccentric overload, a flywheel cylindrical shaft type with low moments of inertia is advised to be used.

The aims of this study were to analyse the effect of chronic strength training over concentric power (CON), eccentric power (ECC), ECC/CON ratio, and 20 m linear sprint performance in elite young soccer players. Twenty young elite Spanish soccer players were assigned to an experimental group (CPG) which performed a front-step exercise using a conical pulley, 2–3 sets of 6 repetitions each leg, during 9 weeks (CPG, n=10) in addition to its usual strength training, or to a control group (CG, n=10). The improvements in the ECC mean power (36%, ES=1.61), and ECC / CON ratio (17%, ES=1.77) were substantially greater in the CPG than in the CG while the CON mean power (16%, ES=0.83) was substantially greater in the CG than in the CPG. The sprinting time for 10 m (2.8%, ES=0.78) and the 10 m flying time between 10–20 m (1.72%, ES=0.41) were substantially enhanced in CPG and CG respectively. To be efficient when defining a functional strength training and performance increments using an inertial device, the mean power output need to be measured during the CON and ECC phases and an analysis of the ECC / CON ratio should be included.

GPS systems are commonly used to analysis football performance during either trainings or matches. While many studies have investigated the validity and reliability of these devices, there is a lack of objective procedures regarding synchronization with gold standards such as real distance or timing gates. The objective of this study was to study the validity and reliability of a 5Hz GPS system (WIMU) during 10m and 30m sprints and during team sports specific movements and the reliability during very high s peeds (> 30 km/h). The Total Distance (TD) BIAS for Circuit A, 10m sprint and 30m sprint were -2.73  1.64 m (p < 0.001), -0.80  0.58 m (p<0.001) and 0.42  2.50 m (p=0.515) respectively. Average ICC for GPS speed point-topoint were 0.976  0.012 and 0.991 0.003 for Circuit B and Motorized Sprints, respectively. The average BIAS compared with each unit mean laps (intra-unit reliability) results for TD, Peak-Speed and Avg-Speed were 0.00  1.68, 0.00  1.73 and 0.00  0.33 for Circuit A, 0.00  0.49, 0.00  0.53 and 0.00  0.77 for 10m sprints and 0.00  2.34, 0.00  0.76 and 0.00  0.74 for 30m sprints, non-significant difference in all cases. In conclusion, despite a lower than recommended sample frequency, the WIMU GPS showed to be valid and reliable for measuring sprints at speed higher than 20 km· h -1 , as well as for team sport movements. (2017). The validity and reliability of a 5-hz GPS device for quantifying athletes' sprints and movement demands specific to team sports.

Muñoz-López, A, De Hoyo, M, Nuñez, FJ, and Sañudo, B. Using tensiomyography to assess changes in knee muscle contraction properties after concentric and eccentric fatiguing muscle actions. J Strength Cond Res 36(4): 935–940, 2022—The purposes of this study were to analyze the effects of different types of muscle contraction (concentric and eccentric) on the passive muscular contraction properties of knee muscles and how muscle contraction can affect the muscles in different knee functions. In total, 23 active healthy men (age: 24.65 ± 1.95 years, height: 1.78 ± 0.05 m, mass: 75.33 ± 8.37 kg) participated in this study. Muscle soreness, muscle contractile properties assessed with tensiomyography (TMG) (vastus lateralis [VL] and biceps femoris [BF]), and isometric peak torque were tested before and immediately after 32 maximal repetitions of an isokinetic leg extension and flexion exercise at 180° per second. Muscle contractions were randomized to each subject's leg. From the TMG variables, only contraction velocity showed significant interactions in time × muscle × contraction (p = 0.046; partial ηp2 = 0.19). A greater reduction was observed in the BF (−29.03%) than in the VL (−21.25%). There was a significant decrease in contraction velocity after concentric p < 0.001, d = 1.18) and eccentric (p = 0.007, d = 0.51) exercise for the BF, while for VL, a decrease was only observed after concentric exercise (p = 0.007, d = 0.66). The leg extension exercise showed reductions in the isokinetic peak torque (p < 0.001; partial ηp2 = 0.83). Isometric peak torque (p < 0.001; partial ηp2 = 0.80) and muscle soreness (p < 0.001; partial ηp2 = 0.70) decreased after exercise. In conclusion, muscle mechanical properties were differently affected in relation to the muscle contraction and knee muscles involved, after a fatiguing leg extension isokinetic exercise. Isometric peak torque and muscle soreness were also reduced immediately after exercise. These results are particularly important to understand how TMG parameters are modified depending on the type of contraction.