1. Rate of torque development scaling factor decreased following a 6-week unilateral isometric training using electrostimulation or voluntary contractionsOlivera Knežević Milović, Nejc Šarabon, Amador García Ramos, Nikola Majstorović, Sladjan D. Milanović, Saša R. Filipović, Dragan Mirkov, 2024, izvirni znanstveni članek Opis: This study explored the changes in the rate of torque development scaling factor (RTD-SF) and maximum voluntary isometric contraction (MVC) variables following six weeks of unilateral isometric electromyostimulation (EMS) and voluntary (VOL) exercises. Twenty-six physically active participants were randomly assigned to EMS (n = 13) or a VOL group. MVC and RTD-SF of the quadriceps femoris of both legs were assessed before and after training. EMS and VOL exercises had identical frequency (three sessions/week), intensity (60% MVC), volume (40 contractions), and work-to-rest ratio (18 min: 6.25 s of work/20 s of rest). There were no between-group differences for the trained leg with overall increases in maximal torque (Tmax) of ~29% (d = 2.11–2.12), ~13% for RTDmax (d = 0.92–1.10); ~23% for Intercept (d = 0.72–0.78), and reduction in RTD-SF by ~15% (d = 1.01–1.10). In the non-trained leg, significant moderate change was only observed after EMS for RTD-SF which decreased by 12.5% (d = 0.76)
Ključne besede: quadriceps, strength, RTD-SF, RFD-SF, EMS
Objavljeno v RUP: 14.01.2026; Ogledov: 259; Prenosov: 0
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2. Gender-related differences in mechanics of the sprint start and sprint acceleration of top national-level sprintersDragan Mirkov, Olivera M. Knezevic, Amador García Ramos, Milan Čoh, Nejc Šarabon, 2020, izvirni znanstveni članek Opis: Background: Within the current study we aimed at exploring gender-related differences and the relationship between sprint start block kinematics and kinetics and sprint acceleration force-velocity (F-v) relationship parameters (maximal force [F0], maximal velocity [v0], maximal power [Pmax] and slope) in top national-level sprinters. (2) Methods: Twenty-eight sprinters (6 females) performed 10 maximal 30-m sprints. Start block and acceleration kinematics and kinetics were collected with an instrumented sprint start block and a laser distance sensor (KiSprint system). Displacement-time data were used to determine the F-v relationship through Samozino's method. (3) Results: Start block rear foot maximal force (effect size [ES] = 1.08), rate of force development (ES = 0.90-1.33), F0 (ES = 1.38), v0 (ES = 1.83) and Pmax (ES = 1.95) were higher in males than in females (p -< 0.05). There were no differences in the slope, and ratio of horizontal-to-resultant force. F0, v0, and Pmax generally presented higher correlations with the start block kinetics (median r [range] = 0.49 [0.28, 0.78]) than with the kinematics (median r [range] = -0.27 [-0.52, 0.28]). (4) Conclusions: We confirmed that sprint block phase and sprint acceleration mechanics should be mutually assessed when analyzing sprinting performance. KiSprint system could provide more accurate information regarding mechanical pattern and technique during sprint initiation and acceleration, and potentially help create a more personalized and effective training program.
Ključne besede: force-velocity relationship, force platform, kinematics, kinetics, track-and-field
Objavljeno v RUP: 10.09.2020; Ogledov: 2624; Prenosov: 87
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3. Introduction of dynamic rate-of-force development scaling factor in progressive drop jumpsNejc Šarabon, Olivera M. Knezevic, Dragan Mirkov, Darjan Smajla, 2020, izvirni znanstveni članek Opis: Rapid force generation across submaximal levels has been evaluated with the rate of force development scaling factor (RFD-SF) in different isometric tasks, while such measurement was still not verified in dynamic tasks. Our study was designed to evaluate the feasibility of the RFD-SF in dynamic drop jump (DJ) task (RFD-SFDJ). A total of 55 young athletes performed isometric plantarflexion at different submaximal intensities and 60 DJs (6 different drop heights). For each participant we calculated linearity (r2 ) and slope in isometric task (RFD-SFPF), eccentric part of DJ (RFD-SFDJ-ECC) and concentric part of DJ (RFD-SFDJ-CON), as well as average jump height (DJH) from each drop height. Our results revealed strong linear force-RFD relationship for isometric plantarflexion (r2 = 0.90 % 0.06), eccentric (r2 = 0.87 % 0.09) and concentric phase of DJ (r2 = 0.80 % 0.18). Significant moderate positive correlations were calculated between RFD-SFPF and RFD-SFDJ-ECC (r = 0.311, p < 0.05) and small negative correlations between RFD-SFDJ-CON and RFD-SF (r = -0.276, p < 0.05). Significant positive moderate correlations were seen only between RFD-SFDJ-ECC and DJH from 10 cm (r = 0.459, p < 0.001) and 15 cm (r = 0.423, p < 0.01). This is the first study to introduce and confirm that RFD-SFDJ can be obtained from the multi-joint tasks (60 jumps) and still provide acceptable reliability and linear relationship. Furthermore, RFD-SFDJ may have greater practical application than RFD-SF assessed under the isometric conditions. This verification of RFD-SFDJ opens opportunities for further research regarding its practical application.
Ključne besede: explosive strength, stretch-shortening cycle, plyometric, ankle, isometric
Objavljeno v RUP: 07.08.2020; Ogledov: 4773; Prenosov: 76
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