Eccentriche per l'ipertrofia

[Elitemember]

Un interessante studio, tra l'altro citato in diversi testi di riferimento nella fisiologia applicata allo sport, che pone l'accento sulle diverse modificazioni indotte dall'allenamento eccentrico e concentrico a livello ipertrofico, di forza massima e di attivazione neurale.
L'articolo è gratuito quindi consultabile per intero.

1: J Appl Physiol. 1996 Nov;81(5):2173-81.
Related Articles, Links



Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation.

Higbie EJ, Cureton KJ, Warren GL 3rd, Prior BM.

Department of Exercise Science, University of Georgia, Athens 30602-3654, USA.

We compared the effects of concentric (Con) and eccentric (Ecc) isokinetic training on quadriceps muscle strength, cross-sectional area, and neural activation. Women (age 20.0 +/- 0.5 yr) randomly assigned to Con training (CTG; n = 16), Ecc training (ETG; n = 19), and control (CG; n = 19) groups were tested before and after 10 wk of unilateral Con or Ecc knee-extension training. Average torque measured during Con and Ecc maximal voluntary knee extensions increased 18.4 and 12.8% for CTG, 6.8 and 36.2% for ETG, and 4.7 and -1.7% for CG, respectively. Increases by CTG and ETG were greater than for CG (P < 0.05). For CTG, the increase was greater when measured with Con than with Ecc testing. For ETG, the increase was greater when measured with Ecc than with Con testing. The increase by ETG with Ecc testing was greater than the increase by CTG with Con testing. Corresponding changes in the integrated voltage from an electromyogram measured during strength testing were 21.7 and 20.0% for CTG, 7.1 and 16.7% for ETG, and -8.0 and -9.1% for CG. Quadriceps cross-sectional area measured by magnetic resonance imaging (sum of 7 slices) increased more in ETG (6.6%) than in CTG (5.0%) (P < 0.05). We conclude that Ecc is more effective than Con isokinetic training for developing strength in Ecc isokinetic muscle actions and that Con is more effective than Ecc isokinetic training for developing strength in Con isokinetic muscle actions. Gains in strength consequent to Con and Ecc training are highly dependent on the muscle action used for training and testing. Muscle hypertrophy and neural adaptations contribute to strength increases consequent to both Con and Ecc training.

[richard]

Ti ringrazio per lo spunto. Approfitto per allegare un altro riferimento in tema di eccentriche, a mio avviso molto completo (sottolinea, in particolare, un aspetto da non sottovalutare mai nei nostri allenamenti, quello medico).


LaStayo P C, Woolf J M, Lewek M D, Snyder-Mackler L, PT, Reich T, Lindstedt S L, Eccentric Muscle Contractions: Their Contribution to Injury, Prevention, Rehabilitation, and Sport, Journal of Orthopaedic & Sports Physical Therapy, 33(10): 557 (2003)


Si tratta di una review (o meglio un clinical commentary), di cui allego il paragrafo conclusivo.

CONCLUSION

The traditional thinking that eccentric contractions result in an obligatory damage response may be overstated. While the high forces produced in muscles working eccentrically can certainly cause damage and injury, muscle and tendon appear very capable of adapting to such high forces if the muscle experiences this stimulus progressively and repeatedly. The adaptive mechanisms are not uniformly defined, but it is apparent that muscle can increase in size and strength and its spring quality can change following chronic exposure to eccentric contractions. The muscle-tendon structure also responds favorably to an eccentric-resistance exercise protocol. These adaptations, which need to be explored further in well-defined, basic, randomized epidemiological studies, play a part in (1) the enhancement of high-power sport activities, (2) the prevention, and (3) the rehabilitation of sport injuries and nonsport musculoskeletal impairments, especially those that afflict the elderly. Despite the dearth of studies comparing traditional strength training to exclusively eccentric training, the beneficial effects of the high negative-work exercise regimes are apparent.
In this paper we have explored the potential to capitalize on the ability to perform eccentric contractions (1) chronically (due to the low energetic cost), even with the frail elderly, and (2) with extremely high muscle forces (in excess of the maximum isometric force), which is only possible during eccentric, not isometric nor concentric, contractions. If an exercise is designed to simply recover, eccentrically, the forces generated concentrically, then that exercise does not take advantage of the unique high force-producing properties of eccentric contractions.

E l'intero documento, per chi volesse approfondire.

[Elitemember]

Influence of concentric and eccentric resistance training on architectural adaptation in human quadriceps muscles

Anthony J. Blazevich, Dale Cannavan, David R. Coleman, and Sara Horne

Centre for Sports Medicine and Human Performance, School of Sport and Education, Brunel University, Uxbridge, United Kingdom

Studies using animal models have been unable to determine the mechanical stimuli that most influence muscle architectural adaptation. We examined the influence of contraction mode on muscle architectural change in humans, while also describing the time course of its adaptation through training and detraining. Twenty-one men and women performed slow-speed (30°/s) concentric-only (Con) or eccentric-only (Ecc) isokinetic knee extensor training for 10 wk before completing a 3-mo detraining period. Fascicle length of the vastus lateralis (VL), measured by ultrasonography, increased similarly in both groups after 5 wk (Con = +6.3 ± 3.0%, Ecc = +3.1 ± 1.6%, mean = +4.7 ± 1.7%; P < 0.05). No further increase was found at 10 wk, although a small increase (mean 2.5%; not significant) was evident after detraining. Fascicle angle increased in both groups at 5 wk (Con = +11.1 ± 4.0%, Ecc = +11.9 ± 5.4%, mean = 11.5 ± 3.2%; P < 0.05) and 10 wk (Con = +13.3 ± 3.0%, Ecc = +21.4 ± 6.9%, mean = 17.9 ± 3.7%; P < 0.01) in VL only and remained above baseline after detraining (mean = 13.2%); smaller changes in vastus medialis did not reach significance. The similar increase in fascicle length observed between the training groups mitigates against contraction mode being the predominant stimulus. Our data are also strongly indicative of 1) a close association between VL fascicle length and shifts in the torque-angle relationship through training and detraining and 2) changes in fascicle angle being driven by space constraints in the hypertrophying muscle. Thus muscle architectural adaptations occur rapidly in response to resistance training but are strongly influenced by factors other than contraction mode.