This paper aimed at investigating the neuromuscular response of knee flexor and extensor muscles in elite karateka and karate amateurs (Amateurs) during isokinetic knee flexion/extensions and during the execution of a front kick (FK). Surface electromyograms (sEMG) were recorded from the right vastus lateralis (VL) and biceps femoris (BF) muscles with a four-array electrode during maximal isometric knee flexion and extension (maximal voluntary contraction), during isokinetic contractions (30 degrees , 90 degrees , 180 degrees , 270 degrees , 340 degrees , 400 degrees /s), and during the FK. The level of VL and BF agonist (ago) and antagonist (ant) activation during the isokinetic and FK protocols was quantified through normalized sEMG root mean square value (%RMS(ago/ant-ISOK/FK)). VL and BF average muscle fiber conduction velocity (CV) was computed for isokinetic and FK. Isokinetic flexion and extension torques and knee angular velocity during FK were also assessed. Analysis of variance was used to test the effect of group, angular velocity, and task on the assessed variables (P < 0.05). Elite karateka showed higher isokinetic knee flexion torque when compared with Amateurs. For all angular velocities, VL and BF %RMS(ant-isokinetic) were lower in elite karateka, while their BF-CV(isokinetic) BF-CV(front kick) and BF %RMS(ant-front kick) values were higher. For VL and BF, %RMS(ago-front kick) was lower than %RMS(ago-isokinetic) in both groups. Elite karateka demonstrated a typical neuromuscular activation strategy that seems task and skill level dependent. Knee flexion torque and CV results suggest the presence of an improved ability of elite karateka to recruit fast MUs as a part of training induced neuromuscular adaptation.
The main purposes of this study were to describe the cardiorespiratory fitness and lower limbs maximal muscle power of a selected group of Olympic Italian male (M) and female (F) judokas. Eleven subjects (6 M, 5 F) underwent 3 different tests. The VO(2)max and ventilatory threshold (VT; V-slope method) were assessed during a graded maximal treadmill test. Lower limbs muscle peak power (PP) and mean power (MP) were determined during a 30-second Wingate test (WIN). Post-WIN blood lactate peak was also measured. Subjects were tested also during a 5-minute combat test (CT), during which blood lactate and heart rate (HR) were monitored. VO(2)max (mean +/- SD) was 47.3 +/- 10.9 and 52.9 +/- 4.4 ml x kg(-1) x min(-1) for M and F judokas, respectively. The VT corresponded to 80.8% (M) and 86.5% (F) of VO(2)max. Both PP and MP, measured during the WIN, were significantly higher (p < 0.05) in M than in F judokas (PP: 12.1 +/- 2.4 vs. 9.5 +/- 1.1 W x kg(-1); MP: 5.4 +/- 1.1 W x kg(-1); F: 4.3 +/- 0.5 W x kg(-1)). Post WIN blood lactate peak was 6.9 +/- 2.8 mmol x l(-1) and 6.1 +/- 1.8 mmol x l(-1) for M and F judokas, respectively (not significant). During the CT blood lactate peak was 9.9 +/- 3.0 mmol x l(-1) (M) and 9.2 +/- 2.0 mmol x l(-1) (F); these values being significantly higher than those obtained after the WIN (p < 0.05). In conclusion, Italian Olympic judokas showed high levels of muscle power but accompanied by a moderate engagement of the aerobic metabolic pathway, which is well in accordance with the characteristics of judo. Having these results in top-level athletes may represent a useful contribution to the work of coaches and trainers in optimizing training programs for the achievement of the best performance of the judoka.
IANT-BF is partially related to the age of the group and to joint protection upon impact. Moreover, given the very brief duration of the task, a feed-forward mechanism modulating antagonist activation partly based on the stress imposed on the knee joint could be hypothesized. This mechanism potentially involves skill dependent re-modelling of the peripheral and central nervous system.
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