Biomedical subjects

I G Amiridis

Publications and source records attributed to I G Amiridis.

7 recordsLinked to original sources

PubMed2000

The effects of electromyostimulation training and basketball practice on muscle strength and jumping ability.

The aim of this study was to investigate the influence of a 4-week electromyostimulation training program on the strength of the knee extensors and the vertical jump performance of 10 basketball players. Electromyostimulation sessions were carried out 3 times weekly; each session consisted of 48 contractions. Testing was carried out before and after the electromyostimulation training program (week 4) and once more after 4 weeks of normal basketball training (week 8). At week 4, isokinetic strength increased significantly (p < 0.05) at eccentric and high concentric velocities (between 180 and 360 x s(-1)); this was not the case for low concentric velocities (60 and 120 degrees x s(-1)). Electromyostimulation training increased also isometric strength at the two angles adjacent to the training angle (p < 0.01). Squat jump increased significantly by 14% at week 4 (p < 0.01), whereas counter movement-jump showed no change. At week 8, gains in isokinetic, isometric strength and squat-jump performance were maintained and the counter movement jump performance increased significantly by 17% (p<0.01). Electromyostimulation as part of a short strength-training program enhanced knee extensor strength and squat jump performance of basketball players.

Adult↗

PubMed1999

Velocity-specific training in elbow flexors.

The purpose of this study was to show that velocity-specific training may be implicated in modifications in the level of coactivation of agonist and antagonist muscles. Healthy males (n = 20) were randomly placed in to two groups: one group trained using concentric contractions (n = 12), the other was an untrained control group (n = 8). The training group underwent unilateral resistance training at a level of 35 (5)% of a one-repetition maximal contraction of the elbow flexors, executed at maximal angular velocity. Training sessions consisted of six sets of eight consecutive elbow flexions, three times per weak for a total of seven weeks. The velocity of the ballistic movements executed during training were measured using an optoelectronic measuring device (Elite), both at the beginning and at the end of the training period. Subjects were tested pre- and post-training during isokinetic maximal elbow flexions with constant angular torque (CAT) at 90 degrees (0 degrees = full extension), and at different velocities (60, 120, 180, 240 and 300 degrees x s(-1)) for concentric actions, and -60 and -30 degrees x s(-1) for eccentric and isometric contractions at 90 degrees. In order to verify the levels of activation of the agonist biceps brachii (BB) muscles and antagonist triceps brachii (TB) muscles during maximal voluntary activation, their myoelectrical activities were recorded and quantified as root mean square (RMS) amplitudes, between angles of 75 and 105 degrees . The results show that mean angular velocities between elbow angles of 75 and 105 degrees were similar before [302 (32) degrees x s(-1)] and after [312 (27) degrees x s(-1)] the training period. CAT significantly increased measures at angular velocities of 240 and 300 degrees x s(-1) by 18.7% and 23.5%, respectively. The RMS activity of BB agonist muscles was not significantly modified by training. Post-training normalized RMS amplitudes of TB antagonist muscles were inferior to those observed at pre-training, but values were only significantly different at 300 x s(-1). In conclusion, in this study we attempted to show that an increase of CAT to 240 and 300 degrees x s(-1), though velocity-specific training, may be due, in part, to a lowering of the level of coactivation.

Adult↗

PubMed1997

Effects of the type of recovery training on the concentric strength of the knee extensors.

The aim of this study was to examine the effects of specific concentric and eccentric training on concentric muscular strength following an initial standardized period of excessive training that combined concentric and eccentric actions. For a period of 12 weeks, 37 young elite female basketball players performed standardized training, which included concentric and eccentric actions at 70% and 110% of one-repetition maximum (1-RM), respectively. They were then divided into three groups that followed 12 week programmes which included concentric (C-E/C, n = 13), eccentric (C-E/E, n = 13) or a combination of both concentric and eccentric (C-E/-E, n = 11) exercises. The standardized and specific training programmes consisted of 16 and 8 sets of eight repetitions respectively, performed four times a week. Eleven players who did not participate in either the standardized or specific training programmes served as controls (n = 11). Following the initial 12 weeks of standardized training, the concentric strength of the knee extensors was evaluated isokinetically and using leg-press and squat-jump tests. Significant (P < 0.05) reductions in isokinetic torque, and leg-press and squat-jump performance, were seen. The C-E/C group showed significant (P < 0.05) increases in isokinetic torque, and leg-press and squat-jump performance, after 24 weeks of training when compared with pre-training values. Conversely, no significant differences were noted for the C-E/E and C-E/C-E groups. These findings confirm the mode specificity principle, as only the concentric specific training programme improved the concentric strength of the knee extensors.

Adolescent↗

PubMed1997

Concentric and/or eccentric training-induced alterations in shoulder flexor and extensor strength.

To examine the effect of specific concentric and eccentric training on muscular strength following an initial standardized period of excessive training, shoulder extensors and flexors were tested. The shoulder is a joint particularly susceptible to injury and requires a specific strength training program. For a period of 12 weeks, subjects performed training, including concentric and eccentric actions. Thereafter, they were divided into three groups that performed specific 12-week programs, including either concentric (C-E/C), eccentric (C-E/E), or a combination of both concentric and eccentric exercises (C-E/C-E). Following the initial period of training, significant increases (p < 0.05) in performance were observed for all experimental groups. The C-E/C group showed significant increases (p < 0.05) in performance after 24 weeks of training, especially at high concentric angular velocities. However, the C-E/E group showed significant increases (p < 0.05) only in their eccentric moments. No significant differences were noted for the C-E/C-E group. These findings seem to partly confirm the mode-specificity principle, as only the concentric-specific training program improved concentric and eccentric strength. Moreover, the velocity-specificity principle was strongly supported.

Adolescent↗

PubMed1996

Co-activation and tension-regulating phenomena during isokinetic knee extension in sedentary and highly skilled humans.

The aim of this study was to examine isokinetic torque produced by highly skilled (HS) and sedentary (S) human subjects, during knee extension, during maximal voluntary and superimposed electrical activation. To verify the level of activation of agonist (vastus lateralis, VL, and vastus medialis, VM) and antagonist muscles (semi-tendineous, ST), during maximal voluntary activation, their myo-electrical activities were detected and quantified as root mean square (rms) amplitude. Ten HS and ten S subjects performed voluntary and superimposed isometric actions and isokinetic knee extensions at 14 angular velocities (from -120 to 300 degrees*s(-1)). The rms amplitude of each muscle was normalized with respect to its rms amplitude when acting as agonist at 15 degrees*s(-1). Whatever the angular velocity considered, peak torque and constant angular torque at 65 degrees of HS were significantly higher (P <0.05) than those of S. Eccentric superimposed torque of S, but not HS, was significantly higher (P <0.05) than voluntary torque at -120, -90, - 60 and - 30 degrees*s(-1) angular velocities. For a given velocity, the rms amplitude of VL and VM were significantly lower (P <0.05), during eccentric than during concentric actions, in S, but not in HS. However, whatever the angular velocity, ST co-activation in HS was significantly lower (P < 0.05) than in S. We concluded that co-activation phenomenon could partly explain differences in isokinetic performances. Differences between voluntary and superimposed eccentric torques as well as lower agonist rms amplitude during eccentric action in S, support the possibility of the presence of a tension-regulating mechanism in sedentary subjects.

Adult↗

PubMed1995

[Activation of agonist and antagonist muscles during plantar flexion of the ankle].

The aim of this study was to examine isokinetic moment produced by well-trained and sedentary subjects, during plantar flexion, at 13 angular velocities (from -120 to 300 degrees.s-1), under maximal voluntary and superimposed electrical conditions. In order to verify the level of activation of agonist (Soleus (SOL) and Gastrocnemius Medialis (GM)) and antagonist muscles (Tibialis Anterior (TA), their myoelectrical activities were detected and quantified as Root Mean Square (RMS). Whatever the angular velocity considered, the moments developed at 90 degrees by well-trained subjects were significantly (p < 0.05) higher than those developed by sedentary subjects, except at -10 degrees.s-1. Eccentric superimposed moments of sedentary subjects were significantly (p < 0.05) higher than those developed by the same subjects under maximal voluntary conditions. For a given velocity, the RMS's of S and GM muscles were significantly (p < 0.05) lower, during eccentric than during concentric actions, in sedentary, but not in well-trained subjects. The TA co-activation in well-trained subjects was significantly (p < 0.05) lower than in sedentary subjects, whatever the angular velocity considered. We concluded that a co-activation phenomenon could partly explain differences in isokinetic performances. Differences between voluntary and superimposed eccentric moment as well as lower agonists' RMS during eccentric action, support the presence of a tension-regulating mechanism in sedentary subjects.

Ankle↗

PubMed1994

[Effects of different types of training on torque/angular velocity relationship. Experimental study by isokinetic ergometry in high-level basketball players].

The purpose of this study was to examine the alterations of the Torque/Angular Velocity relationship in knee extensor and flexor muscles due to a long-term training programme. Thirty five young elite basketball players were tested before, after 12 weeks of a common weight-lifting programme (including concentric and eccentric actions) and after 24 weeks including only concentric (C-E/C group) or concentric and eccentric actions (C-E/C-E group). After 12 weeks, significant decrease in torque of knee extensor muscles was observed. In contrast, significant increases in torque of knee flexor and shoulder flexor and extensor muscles were noted. After 24 weeks, significant increases were noted in torque of all muscular groups, for the C-E/C group but not for the C-E/C-E group. It is concluded that training including concentric and eccentric actions have not the same effect on agonist and antagonist muscular groups. The alternation of the contraction mode influences straingthly the strength restoration.

Adolescent↗