Eccentric Training Research

[John A. Casler]

apps.isiknowledge.com/CEL/CIW.cgi?&CustomersID=Highwire&Func=Links&PointOfEntry=FullRecord&PublisherID=Highwire&ServiceName=TransferToWos&ServiceUser=Links&UT=A1991GH96100005&e=CgglEe4K2sRKoHKNqZ.4e_8jAWfB9YDdfbLjXk3.NF2E0Uf49R6eOdIu8hRX5CrL

Title: INFLUENCE OF ECCENTRIC ACTIONS ON SKELETAL-MUSCLE ADAPTATIONS TO RESISTANCE TRAINING
Author(s): HATHER BM, TESCH PA, BUCHANAN P, DUDLEY GA
Source: ACTA PHYSIOLOGICA SCANDINAVICA 143 (2): 177-185 OCT 1991
Document Type: Article
Language: English
Cited References: 40 Times Cited: 126
Abstract: Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle-aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n = 8) performed coupled concentric and eccentric actions while group CON (n = 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n = 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P < 0.05) Type IIA and decreased (P < 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P < 0.05). Type II area increased (P < 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P < 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P < 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P < 0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining. At this time only group CON/ECC showed mean fibre hypertrophy, while capillary density was elevated in groups CON/CON and CON. This study suggests that optimal muscle hypertrophy in response to resistance exercise is not attained unless eccentric muscle actions are performed. The data also show that heavy resistance exercise may produce muscle fibre transformation and capillary neoformation.
Addresses: NASA, BIOMED OPERAT & RES OFF, MAIL CODE MD-M, KENNEDY SPACE CTR, FL 32899 USA
KAROLINSKA INST, DEPT PHYSIOL, ENVIRONM PHYSIOL LAB, S-10401 STOCKHOLM 60, SWEDEN
BIONET CORP, BIOMED & ENVIRONM LABS, KENNEDY SPACE CTR, FL USA

Publisher: BLACKWELL SCIENCE LTD, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL
Subject Category: Physiology
IDS Number: GH961

ISSN: 0001-6772

[carruthersjam]

"Testing and training for top Norwegian athletes" by P.E. Refsnes page 97-115

There are indications,' however, that the fastest fibers are preferentially recruited in the eccentric phase (Nardone et. al. 1989). The selective activation of the fastest fibers was however most pronounced in fast eccentric actions.This accords with our results in a case study of a national caliber bodybuilder. We found an increased proportion of Type IIB fibers after 8 weeks of plyometric training of the elbow flexors. He trained the elbow flexion in a way that can be compared to a drop jump. A load of 30% of 1RM was released and fell freely for 60 cm before causing a very rapid but short stretching of the maximally isometrically activated elbow flexors immediately followed by a concentric action. Before this training, the athlete had no fibers classified as Type IIB, but after the training period we found several Type IIB fibers. This may perhaps be explained as a selective recruitment of the fastest fibers during the extremely explosive training, and these results may indicate that training can convert other fibers to Type IIB fibers.
The results of our studies have led to changes in the training regimes of top Norwegian athletes. We regard eccentric training to be an excellent way to overload the muscles and many top athletes use eccentric training regularly in their strength and power training. In the future we assume that this type of training will be regarded as necessary for many groups of athletes. Even a manufacturer of commercial strength training equipment, the American Life Fitness company for instance, has built machines that are based on the principle of plyometric training, and these machines are used by people who are not engaged in top-level athletics.We think that maximal strength is necessary also for improvement of the explosive strength. Many top athletes engaged in sports that require excellent explosive strength have neglected training of their maximal strength and have had to pay the price for this. When their motor is too small, they have by no means the same potential for increasing their performance, even with proper explosive strength training.