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1.
Bilateral synergies in foot force production tasks
Goran Marković, Nejc Šarabon, Pavle Mikulić, Mark L. Latash, 2013, original scientific article

Abstract: We analysed the effects of task symmetry during bilateral accurate force production tasks performed by the two feet. In particular, we tested a hypothesis that bilateral deficit would lead to higher indices of synergies defined as co-varied adjustments in the two forces across trials that reduced total force variability. The subjects produced steady-state force followed by a quick force pulse into the target. The two feet could be acting both into plantar flexion and into dorsiflexion (symmetrical tasks), or in opposite directions (asymmetrical task). We used the framework of the uncontrolled manifold hypothesis to quantify two variance components, one of which did not change total force (VUCM), while the other did (VORT). Synergy indices during the asymmetrical task were higher than in either symmetrical task. The difference was due to higher VUCM (compared to the symmetrical plantar flexion task) or lower VORT (compared to the symmetrical dorsiflexion task). The synergy index showed a drop (anticipatory synergy adjustment, ASA) starting 100150 ms prior to the force pulse initiation. The ASA tended to be shorter and of a smaller magnitude for the asymmetrical task. This is the first demonstration of bilateral synergies during accurate force production by the legs. We conclude that bilateral deficit has no or weak effects on two-leg synergies. The results fit the earlier introduced scheme with two groups of neural variables defining average performance of a redundant system and patterns of co-variation among its elemental variables, respectively
Found in: osebi
Keywords: kinesiology, force, synergy, legs, bilateral deficit, symmetry
Published: 15.10.2013; Views: 3807; Downloads: 236
URL Full text (0,00 KB)
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Effects of eccentric training at long muscle length on architectural and functional characteristics of the hamstrings
Nejc Šarabon, Goran Marković, Rok Vatovec, Jan Marušič, 2020, original scientific article

Abstract: Hamstring strain injuries during sprinting or stretching frequently occur at long-muscle length. Yet, previous research has mainly focused on studying the effectiveness of eccentric hamstring strengthening at shorter muscle length on hamstring performance, morphology, and hamstring strain injury risk factors. Here, we evaluated the effects of 6-week eccentric hamstring training at long-muscle length on functional and architectural characteristics of the hamstrings. Healthy and injury-free participants (n = 40; age 23.7 % 2.5 years) were randomly assigned to control or intervention group. Training intervention consisted of 12 sessions with two eccentric hamstring exercises in a lengthened position. Outcome measures included isokinetic and isometric knee flexion peak torque, Nordic hamstring exercise peak torque, voluntary activation level, and countermovement jump performance. Ultrasonography was used to determine muscle thickness, pennation angle, and fascicle length of biceps femoris long head (BFlh). A significant time % group interaction effect was observed for all measured parameters except countermovement jump performance and muscle thickness. The training intervention resulted in increased concentric and eccentric knee flexion peak torque at 60°/s (d = 0.55-0.62, P = .02 and .03) and concentric peak torque at 180°/s (d = 0.99, P = .001), increased isometric knee flexion peak torque (d = 0.73, P = .008) and Nordic hamstring exercise peak torque (d = 1.19, P < .001), increased voluntary activation level (d = 1.29, P < .001), decreased pennation angle (d = 1.31, P < .001), and increased fascicle length (d = 1.12, P < .001) of BFlh. These results provide evidence that short-term eccentric hamstring strengthening at long-muscle length can have significant favorable effects on various architectural and functional characteristics of the hamstrings.
Found in: osebi
Keywords: biceps femoris, fascicle length, knee flexion torque, pennation angle, strength
Published: 07.08.2020; Views: 913; Downloads: 53
URL Full text (0,00 KB)

4.
Does pre-exercise static stretching inhibit maximal muscular performance?
Nejc Šarabon, Luka Simić, Goran Marković, 2012, original scientific article

Found in: osebi
Keywords: warm-up, stretch, performance, acute effects
Published: 15.10.2013; Views: 3189; Downloads: 83
URL Full text (0,00 KB)

5.
Change of muscle activation patterns in uphill cycling of varying slope
Borut Fonda, Nejc Šarabon, Goran Marković, 2012, original scientific article

Found in: osebi
Keywords: Electromyography, Intensity, timing, Inter-muscular coordination
Published: 15.10.2013; Views: 2686; Downloads: 86
URL Full text (0,00 KB)

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