Koncentrická vs. ekcentrická kontrakce

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J_Dogg
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Koncentrická vs. ekcentrická kontrakce

Příspěvekod J_Dogg » 2. lis 2006 13:10

Studie:

The effect of training with concentric and eccentric contractions on fiber hypertrophy and isometric torque production was investigated in 20 healthy subjects. One group (eight female and two male subjects) performed concentric contractions of their quadriceps femoris muscles at an intensity of 90% of their maximal concentric power. The other group (six female and four male subjects) performed eccentric contractions at the same relative power level. Both groups exercised three times per week for 4 wk at a constant speed of 60 degrees.s-1 on a Kin-Com dynamometer. Needle biopsies were obtained from the vastus lateralis before and after the exercise program. Fiber-type differentiation was performed using a myosin ATPase stain at a preincubation of 10.5. Maximal isometric knee extension torque was also measured before and after the exercise program. An analysis of covariance was used to determine whether there were significant differences between the exercise groups in: 1) the post-exercise fiber areas and 2) maximal isometric torque (MIso), while controlling for initial differences. Results showed a significant difference between the Type II fiber areas (P < 0.01) and the MIso (P = 0.01). These data indicate that, when exercising at the same relative power level, a subject performing concentric contractions will show greater muscle hypertrophy and improve in MIso production more than a subject training with eccentric contractions.

PMID: 7658948 [PubMed - indexed for MEDLINE]


zdroj: http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract

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Reginald
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Příspěvekod Reginald » 2. lis 2006 13:36

Když to vezmu selským rozumem, tak u obou skupin bylo použito 90% maxima koncentrického pohybu, takže ti co prováděli excentrickou fázi pohybu museli vynaložit menší úsilí. Ale nevím co je ten Kin-Com dynamometer. V každém případě to na mě působí dost nedůvěryhodně.

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J_Dogg
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Příspěvekod J_Dogg » 2. lis 2006 14:15

při koncentrickém pohybu se stejnou vahou jako při ekcentrickém musím vynaložit větší úsilí, takže proto ta větší hypertrofie. Aspoň jak to chápu já.

Btw kanadský silový kouč Christian Thibaudeau napsal pro t-nation dobrý článek Eccentric- base training a celou knihu o ekcentrickém tréninku Theory and Application of Modern Strength Training Methods (Canada 2004), kde říká, že ekcentrický trénink je jedním z největších stimulů v silovém tréninku. V knize uvádí četné studie, které potvrzují přínos ekcentrického tréninku.

Studie:

§ Hortobagyi and coworkers found that the total maximal strength improvement from eccentric-only training brought more strength gains than a concentric-only program followed for six weeks. Eccentric training gave a mean improvement of 85%, while concentric training led to an improvement of 78%.

§ Higbie et al. (1996) found a combined strength increase (concentric strength improvement plus eccentric strength improvement) of 43% with an eccentric-only regimen compared to one of 31.2% with a concentric-only regimen. This study also found that eccentric-only training led to an average muscle size gain of 6.6% over ten weeks while a concentric-only program led to gains of 5%.


§ Hilliard-Robertson and coworkers concluded that: “A resistance training protocol which includes eccentric as well as concentric exercise, particularly when the eccentric is emphasized, appears to result in greater strength gains than concentric exercise alone.”


§ An early study by Komi and Buskirk (1972) recorded greater strength increases after an eccentric training regimen than after a concentric-only regimen.


§ There is a greater neural (Strength) adaptation to eccentric training than to concentric training (Hortobagyi et al. 1996).


§ There is a more important force output produced during a maximal eccentric action (greater overload) due to higher external loading (Colliander and Tesch 1990).


§ There is a higher level of stress per motor unit during eccentric work. Less motor units are recruited during the eccentric portion of a movement, thus each of the recruited motor units receive more stimulation (Grabiner and Owings 2002; Linnamo et al. 2002). There is also evidence that shows eccentric nervous system adaptation potential is higher than that of concentric adaptation due to less motor unit recruitment.


§ There is some evidence that maximal eccentric actions will preferably recruit fast-twitch muscle fibers, which are more responsive to muscle growth and strengthening (Nardone et al. 1989, Howell et al. 1995, Hortobagyi et al. 1996). In fact, eccentric training may stimulate an evolution towards a faster contractile profile (Martin et al. 1995).


§ Most of the micro-trauma to the muscle cells incurred during training is a result of the eccentric action (Brown et al. 1997, Gibala et al. 200). It has been established that this micro-trauma acts as the signal to start the muscle adaptation process (Clark and Feedback, 1996).


§ Greater cross-education (Hortobagyi and Lambert 1997). Cross education refers to transfer of strength gains from one limb-side to the other. It means if you were to use only your right arm in an eccentric action that some strength gains would transfer to your left.


§ Strength gained from eccentric training is maintained longer during periods of detraining than from concentric only training (Colliander and Tesch 1992, Housh et al. 1996), which may be very important for athletes who cannot train as much during the season as they can in the off-season.


§ Sorichter et al. (1995) as well as Saxton and Donnelly (1995) studied the impact of low intensity concentric training following heavy eccentric loading and found that this second bout of training (light concentric exercise) actually improved several markers of recovery.


§ Sorichter et al. found that the concentric session might even have a “massaging” effect that could improve recovery. The study by Saxton and Donnelly is even more interesting as it found that performing light concentric training on the days after the intense eccentric loading actually increased the rate of force recovery and reduced the duration and intensity of the soreness caused by eccentric training.


§ Eccentric training seems to preferentially fatigue and damage the fast-twitch muscle fibers (Linnamo et al. 2000).


§ In line with that finding are the results of a study by Byrne and Eston (2002) that eccentric training causes a reduction in the capacity to produce a lot of force and power during the recovery period, but that the ability to maintain a moderate contraction intensity is actually increased!

What’s in it for me?
§ If you de-emphasize the yielding (lowering) portion of your strength exercises you might as well not train if size and strength is what you seek. This doesn’t mean you should emphasize the negative ALL the time, but in some cases you should.

§ Accentuating the eccentric stress during a session will lead to more strength gains. These gains are related to structural (hypertrophy) and neural (strength) adaptations.

§ The eccentric portion of a movement is the main stimulus for muscle growth as it is the cause of most of the micro-trauma inflicted on the muscles, which acts as the signal to kick the muscle building process into overdrive

§ One recent study (LaStayo et al. 2003) even found accentuated eccentric training to cause 19% more muscle growth than traditional strength training over eleven weeks!


související článek: Breaking the strength barrier

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Reginald
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Příspěvekod Reginald » 2. lis 2006 14:59

§ Greater cross-education (Hortobagyi and Lambert 1997). Cross education refers to transfer of strength gains from one limb-side to the other. It means if you were to use only your right arm in an eccentric action that some strength gains would transfer to your left.

Tohle je zajímavý. Od teď budu cvičit jenom pravou ruku a pravou nohu :-D
Kařdopádně za sebe říkám, že na sílu a objem bicepsu (a určitě nejen na něj) výborně funguje trénink založený jen na excentrické kontrakci.

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J_Dogg
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Příspěvekod J_Dogg » 2. lis 2006 15:04

Taky jsem se setkal s doporučením, aby někdo, kdo má zraněnou ruku posiloval jenom tu zdravou, protože to bude mít pozitivní vliv i na tu zraněnou...


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