acta facultatis educationis physicae universitatis comenianae

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22 Marián Vanderka – Adrián Novosád force and it is thought that the fast twitch fibres may be selectively activated during high velocity movements. When using light loads, high force levels are achieved only through a very small range of movement. Some training techniques aim at decreasing the deceleration phase by allowing the load to be projected as in a throw or a jump (Cronin et al., 2001). It may be important in developing power whether the athlete uses eccentric muscle action prior to concentric muscle action. Findings indicate that this type of training leads to greater rate of force development, higher peak bar velocities, higher accelerations achieved throughout the entire range of movement and increased work and power (Bosco et al., 1982). Previous studies proved the optimal effect of rapid eccentric phase in relative small range of motion 4 – 5 %. The elastic properties of activated muscle-tendon system and reflexes are useful only in this case for the increasing production of force and power (Bosco et al., 1982, Häkkinen et al., 1986). While studies have examined the effect of load, speed of movement (Newton et al., 1996) and contraction type, some of them find out differences of strength parameters at various of exercises tempos (Cronin et al., 2001; Pryor et al, 2011). Only a few studies have examined the training effects of strengthening with or without eccentric breaking in a single research paradigm (Naruhiro et al, 2008). Therefore the purpose of our study was to compare the effects of explosive squat training with and without counter movement. We hypothesized that performing eccentric phase without braking in the lowest position would maximize power output and especially the rate of force development in the comparison with training by 2 second break in the lowest position of squats. We try to get detailed knowledge about the mechanisms of adaptation to loaded explosive squatting and based on these findings propose more effective development of strength abilities. Methods It was a time parallel double group experiment with 11 weeks duration and frequency of trainings 2 times a week. Thirty male subjects were divided into two groups (n = 15 per group). Experimental group (Ex) performed counter movement. No counter movement group (Ko) had two-second stop at bottom squat position. The subjects were physically active, but not highly trained students of Faculty of PE and Sport, Comenius University in Bratislava, Slovakia. (age 22.1 ± 2.5 years; weight 78.3 ± 16.1 kg; height 178.2 ± 12.2 cm). After pretesting, the subjects were divided in the groups with no significant differences in power output parameters. Both groups trained with the same volume and manner of implementing the active part of the movement (concentric contraction). Then effort of this training was to maximize acceleration. The training load was gradually increase in combination from 3 sets of 6 reps with dumbbells weighing about 5 % lower than the maximum rating, which was at about 50 % of 6RM, then we added a week alternating series and increased weight dumbbells, while in the eighth week a volume ceiling was achieved, namely 6 sets of 6 reps with 20 % heavier weights than the maximum rating at the beginning of the experiment, which represents approximately 70 % of 6RM. Following parameters were tested: the mean rate of force development (RFD) in the intervals 0 – 50 ms of maximal isometric contraction at 90° knee angle on the dynamometer plate; the highest average power output in the diagnostic series measured by Fitrodyne (Pmean) and six repetition maximum in half squat at 90° in the knee Comenius University in Bratislava, Faculty of Physical Education and Sports
Weighted squat training with and without counter movement for strength and power development 23 joint (6RM) for security reasons. We used nonparametric statistical methods on assessing the significance of differences in mean values: two-way Mann-Whitney and Wilcox t-test. Results Increase in the maximum power capabilities were comparable and statistically significant (p < 0.05) in both groups. When we do the squat exercises, for safety reasons we added 6RM testing, and after a period of training we reached changes. The Ex group achieved the improvement of 10.5 ± 5.8 kg (10.5 %) (Fig. 1), the Ko group of 12, 1 ± 5.9 kg (12.5 %). Figure 1 Pre (In) and post (Out) 11weeks training period both groups (Ko and Ex) values of six repetition maximum 6RM (kg) during the squat exercises The highest average power output in the total concentric phase measured in the diagnostic series (Pmean) increased modestly after a period of training exercises in both groups (Fig. 2). Additions to the average power in concentric phase of movement when squatting were comparable in both groups and were statistically insignificant (Fig. 2). Tested subjects in Ex group improved an average of 11.94 ± 84.7 W (1.7 %) in group Ko of 14.6 ± 88.4 W (1.9 %). The average rate of force development - strength gradient (RFD) measured in isometric mode is a parameter that showed the most significant changes in both groups during the 11 weeks training period. The most significant increases (p < 0.01) was noticed mainly in the period of 0 – 50 ms of maximal isometric contraction. Significant pre-post differences in the improvements between groups were detected in favour of (Ex) group in the force gradient (RFD) measured in the period of 0 – 50 ms in the isometric mode at 90° squat in the knee joint (p < 0.05). Ex group achieved the improvements of 2.57 ± 2.50 N·s 1 (60.8 %, p < 0.01) from the average initial value of 3.96 to 6.54 N·s 1 . Ko group RFD (0 – 50) was improved of 2.23 ± 2.40 (50.2 %, p < 0.01) from 4.73 to 7.10 N·s 1 (Fig. 3). Acta Facultatis Educationis Physicae Universitatis Comenianae LII/I
Page 1 and 2: ACTA FACULTATIS EDUCATIONIS PHYSICA
Page 3: Contents 3 CONTENTS THE SUBJECTIVE
Page 6 and 7: 6 Durdica Miletic items were taken
Page 8 and 9: 8 Durdica Miletic Table 1 Factor An
Page 10 and 11: 10 Durdica Miletic influence these
Page 12 and 13: 12 Durdica Miletic 20. REJESKI, W.
Page 14 and 15: 14 Martin Sebera - Jaromír Sedlá
Page 24 and 25: 24 Marián Vanderka - Adrián Novos
Page 30 and 31: 30 Miroslav Huntata - Ludmila Zaple
Page 42 and 43: 42 Juraj Karas considered the range
Page 44 and 45: 44 Juraj Karas The manufacturer cla
Page 46 and 47: 46 Juraj Karas Figure 4 The coeffic
Page 48 and 49: 48 Juraj Karas Comenius University
Page 50 and 51: 50 Vladimír Přidal - Jaroslav Han
Page 62 and 63: 62 Dagmar Nemček - Jela Labudová
Page 72 and 73:
72 Dagmar Nemček - Jela Labudová
Page 74 and 75:
74 Martin Vaváček - Marek Hardoň
Page 76 and 77:
76 Martin Vaváček - Marek Hardoň
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ACTA FACULTATIS EDUCATIONIS PHYSICA
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acta facultatis educationis physicae universitatis comenianae

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