Christos Kotzamanidis

The Effect of a Combined High-Intensity Strength and Speed Training Program on the Running and Jumping Ability of Soccer Players

The purpose of this study was to investigate the effect of a combined heavy-resistance and running-speed training program performed in the same training session on strength, running velocity (RV), and vertical-jump performance (VJ) of soccer players. Thirty-five individuals were divided into 3 groups. The first group (n = 12, COM group) performed a combined resistance and speed training program at the same training session, and the second one (n = 11, STR group) performed the same resistance training without speed training. The third group was the control group (n = 12, CON group). Three jump tests were used for the evaluation of vertical jump performance: squat jump, countermovement jump, and drop jump. The 30-m dash and 1 repetition maximum (1RM) tests were used for running speed and strength evaluation, respectively. After training, both experimental groups significantly improved their 1RM of all tested exercises. Furthermore, the COM group performed significantly better than the STR and the CON groups in the 30-m dash, squat jump, and countermovement jump. It is concluded that the combined resistance and running-speed program provides better results than the conventional resistance training, regarding the power performance of soccer players.

Effect of plyometric training on running performance and vertical jumping in prepubertal boys.

The purpose of this study was to investigate the effect of plyometric training on running velocity (RV) and squat jump (SJ) in prepubescent boys. Fifteen boys (11.1 ± 0.5 years) followed a 10-week plyometric program (JUMP group). Another group of 15 boys (10.9 ± 0.7 years) followed only the physical education program in primary school and was used as the control group (CONT group). Running distances (0–10 m, 10–20 m, 20–30 m, and 0–30 m), were selected as testing variables to evaluate the training program. The total number of jumps was initially 60 per session, which was gradually increased over a period of 10 weeks to 100 per session. Results revealed significant differences between CONT and JUMP groups in RV and SJ. In JUMP group the velocity for the running distances 0–30, 10–20, and 20–30 m increased (p < 0.05), but not for the distance 0–10 m (p > 0.05). Additionally, the SJ performance of the JUMP group increased significantly, as well (p < 0.05). There was no change in either RV or SJ for the CONT group. These results indicate that plyometric exercises can improve SJ and RV in prepubertal boys. More specifically, this program selectively influenced the maximum velocity phase, but not the acceleration phase.

Postactivation Potentiation Effects After Heavy Resistance Exercise on Running Speed

The purpose of this study was to investigate the postactivation potentiation effect after a heavy resistance stimulus (HRS) on running speed (RS). Fifteen amateur team game players (basketball, volleyball, handball, and soccer players), ages 18–23 years running the 30-m dash and the intermediate phase of 0–10 and 0–30 m sprints, were used to evaluate RS. Resistance training consisted of 10 single repetitions at 90% of 1 repetition maximum. The running tests were performed 3 times—(a) 3 minutes prior the HRS, (b) 3 minutes after the HRS, and (c) 5 minutes after the HRS—in separated training sessions. Results showed that RS was not affected 3 minutes after the resistance training, but it increased for both selected running phases (0–10 and 0–30 m) 5 minutes after the HRS (p = 0.05). These findings indicate that heavy resistance exercise improves 10- and 30-m sprint performance when performed 5 minutes after the exercise bout.

Exercise-induced changes in the concentration of individual fatty acids and triacylglycerols of human plasma

Nineteen male handball players played for two 30-minute periods with a 10-minute interval. Blood samples were drawn at rest, at halftime, and at the end of the game. A biopsy of subcutaneous fat was also taken from 14 participants. Mean plasma lactate concentration was not greater than 4 mmol/L at the end of either half. The concentration of nonesterified fatty acids (NEFA) in plasma increased gradually but not uniformly throughout the game. In effect, the percentages of the major NEFA were significantly different at the three time points of sampling: palmitate (16:0) and stearate (18:0) decreased and oleate (18:1) and linoleate (18:2) increased, resulting in an increase of the ratio of unsaturated to saturated fatty acids (U/S) from 1.1 at rest to 1.6 at the end. The concentration of plasma triacylglycerols (TG) declined during the game, but nine of 19 subjects showed increases during one or both halves, implying a stimulation of TG release from the liver during exercise, which can, at times, overcome the increased hydrolysis of TG in muscle capillaries. Changes in the acyl-group distribution of plasma TG were minor but also in favor of unsaturated fatty acids. Changes in NEFA composition tended toward the composition of adipose tissue, in which TG had a U/S ratio of 3.2. Linear regression between changes in the total concentration of plasma NEFA during each half of the game and corresponding changes in the concentration of individual NEFA showed that the contributions (slopes) of myristate (14:0), palmitoleate (16:1), 18:0, and 18:2 were not significantly different from their fractions in adipose tissue TG.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of chronological age and gender on the development of sprint performance during childhood and puberty.

Papaiakovou, G, Giannakos, A, Michailidis, C, Patikas, D, Bassa, E, Kalopisis, V, Anthrakidis, N, and Kotzamanidis, C. The effect of chronological ageand gender on the development of sprint performance during childhood and puberty. J Strength Cond Res 23(9): 2568-2573, 2009-The purpose of the present study was to examine the effect of chronological age and gender on speed development during different sprinting phases in children and adolescents of both genders. The sample consisted of 360 sedentary pupils aged between 7 and 18 years, with 15 pupils representing each subgroup. The 30-m sprint speed was measured with photocells every 10 m. According to the results, boys and girls showed a gradual improvement in running speed during each sprint phase. The 18-year-old boys had significantly higher sprint speed in all measured distances compared to the 15-year-old or younger boys (p < 0.05), whereas the 18-year-old girls had significantly higher speed at the distances of 0 to 10, 10 to 20, 20 to 30, and 0 to 30 m compared to the 13- and 12-year-old or younger girls (p < 0.05). Significant differences between genders in the 15-years-old or older participants were observed. It is concluded that, from 7 to 18 years of age, gender and chronological age are factors that affect running speed during the 30-m sprint. Furthermore, the performance on each sprint phase is uniformly affected by the chronological age. Boys run faster than girls in all running phases, and the span between genders increases after the age of 15 years. It is useful that coaches take these findings into consideration when evaluating children in sprint performance.

The effect of sprinting after each set of heavy resistance training on the running speed and jumping performance of young basketball players.

Tsimahidis, K, Galazoulas, C, Skoufas, D, Papaiakovou, G, Bassa, E, Patikas, D, and Kotzamanidis, C. The effect of sprinting after each set of heavy resistance training on the running speed and jumping performance of young basketball players. J Strength Cond Res 24(8): 2102-2108, 2010-The purpose of this study was to investigate the effect of a 10-week heavy resistance combined with a running training program on the strength, running speed (RS), and vertical jump performance of young basketball players. Twenty-six junior basketball players were equally divided in 2 groups. The control (CON) group performed only technical preparation and the group that followed the combined training program (CTP) performed additionally 5 sets of 8-5 repetition maximum (RM) half squat with 1 30-m sprint after each set. The evaluation took place before training and after the 5th and 10th weeks of training. Apart from the 1RM half squat test, the 10- and 30-m running time was measured using photocells and the jump height (squat, countermovement jump, and drop jump) was estimated taking into account the flight time. The 1RM increased by 30.3 ± 1.5% at the 10th week of training for the CTP group (p < 0.05), whereas the CON group showed no significant increase (1.1 ± 1.6%, p > 0.05). In general, all measured parameters showed a statistically significant increase after the 5th and 10th weeks (p < 0.05), in contrast to the CON group (p > 0.05). This suggests that the applied CTP is beneficial for the strength, RS, and jump height of young basketball players. The observed adaptations in the CTP group could be attributed to learning factors and to a more optimal transfer of the strength gain to running and jumping performance.

Characterization of vanA-type Enterococcus faecium isolates from urban and hospital wastewater and pigs

Aims:  In this study we analysed urban, hospital wastewater and pig faeces samples to investigate the presence of vancomycin‐resistant Enterococcus faecium strains (VREF) and to determine potential links among the strains originating from the above sources and VREF strains causing clinical infections.

The post-activation potentiation effect on squat jump performance: age and sex effect.

This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFDpeak) in preadolescent (10-12 y), adolescents (14-15 y) and adults (20-25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFDpeak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFDpeak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFDpeak in both adult groups (P < .05) and teen-males, with no effects in children. In conclusion, the PAP effects on SJ performance and RFDpeak are age- and sex-dependent; that is PAP appears as a viable method for acutely enhancing SJ performance in men but not in pediatric population.

Submaximal Fatigue and Recovery in Boys and Men

We examined the effects of a sustained submaximal isometric contraction on fatigue and recovery rates in untrained prepubescent boys and men. Fifteen prepubescent boys and 15 men executed an isometric plantar flexion at 20% of their maximal voluntary contraction for 10 min. During the fatigue protocol, surface electromyogram of the soleus, medial gastrocnemius, and tibialis anterior muscles were obtained. Following the fatigue protocol, maximal voluntary contraction data were also obtained every 3 min throughout a 15-min recovery period. During the fatigue protocol, agonist and antagonist surface electromyogram increased gradually to a similar extent in both groups. Following fatigue, torque and surface electromyogram during a maximal voluntary contraction decreased compared to pre-fatigue values and recovered in a similar manner in both groups. However, boys showed faster recovery in torque and surface electromyogram during the third minute of recovery period. It is concluded that a low-intensity sustained isometric fatigue protocol induces similar fatigue levels in boys and men. However, there is evidence that boys can recover faster than men.

The Effect of Basketball Training on the Muscle Strength of Adults With Mental Retardation

Tsimaras, VK, Samara, CA, Kotzamanidou, MC, Bassa, EI, Fotiadou, EG, and Kotzamanidis, CM. The effect of basketball training on the muscle strength of adults with mental retardation. J Strength Cond Res 23(9): 2638-2644, 2009-The purpose of this study was to evaluate the effect of basketball training on the muscle strength of adults with mental retardation (MR). Twenty-four adults with and without MR were separated into 3 groups. Eight adults (mean age 25.4 years) with normal IQ constituted the control group (NIQ). Eight adults (mean age 26.5 years) with MR and all participating in a 4-year systematic basketball exercise program constituted the trained group (MR-T), and 8 adults (mean age 25.3 years) with MR exercised occasionally for recreational reasons formed the MR-R group. Parameters measured were isometric and isokinetic concentric and eccentric muscle strength. All subjects performed a leg strength test on a Cybex Norm isokinetic dynamometer. Analysis of variance was used to examine mean differences between the values of the 3 groups. A significance level of 0.05 was used for all tests. The NIQ group showed a statistically significant difference in all measured values compared to the MR groups. The MR-T group presented higher absolute and relative torque scores for both knee extensors and flexors than the MR-R group, whereas the MR-R group presented statistically higher antagonistic activity for both knee extensors and flexors than the MR-T group. In addition, both MR groups presented statistically higher antagonistic activity for both knee extensors and flexors compared to the NIQ group. Data support participation on a systematic and well-designed basketball training program to improve muscle strength levels of adults with MR. Participation in basketball without necessarily focusing on developing specific fitness components may be an effective training strategy for the promotion of strength of adults with MR.