Exzentrisches Training oder umgangssprachlich "Negative", haben in den letzten Jahren zunehmend an Popularität gewonnen. Grund dafür sind auf der einen Seite die nachgewiesenen, positiven Effekte zur Schmerzlinderung und Heilung von Sehnenbeschwerden (1, 2, 3). Aber auch die Trainingswissenschaften haben sich verstärkt mit exzentrischem Training beschäftigt, da es dank der supraphysiologischen Widerstände die während einer solchen Kontraktion möglich sind, als besonders effektive Methode zur Erzeugung von Mikrotraumata (feine Risse im Zellgewebe/DOMS) gilt (4). Von diesen Verletzungen des Muskelgewebes nimmt man bisher an, dass sie der entscheidende Signalpfad zur Stimulation der Proteinsynthese sind, welche letztlich zu Muskelwachstum führen soll (5). Im folgenden Review will ich diesen Ansatz hinterfragen und herausstellen, ob exzentrisches Training tatsächlich nicht nur heilsam, sondern gleichzeitig auch noch die Wunderwaffe zum Muskelaufbau darstellt:
Muscular adaptation to concentric and eccentric exercise at equal power levels
MAYHEW, THOMAS P.; ROTHSTEIN, JULES M.; FINUCANE, SHERYL D.; LAMB, ROBERT L.
Abstract:
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 prein-cubation of 10.5. Maximal isometric knee extension torque was also measured before and after the exercise program. An analysis of co-variance 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 (Mlso), while controlling for initial differences. Results showed a significant difference between the Type II fiber areas (P < 0.01) and the Mlso (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 Mlso production more than a subject training with eccentric contractions.
1995 The American College of Sports Medicine
Skeletal muscle hypertrophy in response to isometric, lengthening, and shortening training bouts of equivalent duration
Gregory R. Adams, Daniel C. Cheng, Fadia Haddad, and Kenneth M. Baldwin
Abstract:
Movements generated by muscle contraction generally include periods of muscle shortening and lengthening as well as force development in the absence of external length changes (isometric). However, in the specific case of resistance exercise training, exercises are often intentionally designed to emphasize one of these modes. The purpose of the present study was to objectively evaluate the relative effectiveness of each training mode for inducing compensatory hypertrophy. With the use of a rat model with electrically stimulated (sciatic nerve) contractions, groups of rats completed 10 training sessions in 20 days. Within each training session, the duration of the stimulation was equal across the three modes. Although this protocol provided equivalent durations of duty cycle, the torque integral for the individual contractions varied markedly with training mode such that lengthening > isometric > shortening. The results indicate that the hypertrophy response did not track the torque integral with mass increases of isometric by 14%, shortening by 12%, and lengthening by 11%. All three modes of training resulted in similar increases in total muscle DNA and RNA. Isometric and shortening but not lengthening mode training resulted in increased muscle insulin-like growth factor I mRNA levels. These results indicate that relatively pure movement mode exercises result in similar levels of compensatory hypertrophy that do not necessarily track with the total amount of force generated during each contraction.
Journal of Applied Physiology May 2004 vol. 96 no. 5 1613-1618.
Das, in Zusammenhang mit der durch schweres exzentrisches Training verursachten temporären Glukoseintoleranz (das liegt vermutlich übrigens an einer geringeren Konzentration von GLUT4 Protein im Muskel nach exzentrischem Training, auch wenn wiederum unklar ist wie dieser Mangel entsteht. Siehe Volltext.) lässt mich inzwischen stark an dem Nutzen von reinen "Negativen" für Muskelaufbau zweifeln.
Desweiteren wackelt für mich damit auch die Hypothese des Trauma induzierten Stimulus als entscheidenden Faktor, da Negative zweifelsohne größeren DOMS verursachen. Oder sagen wir zumindest: Die Hypothese das die Herkunft des DOMS durch exzessive Dehnung (wie Negative oder Loaded Stretching) einen optimalen Wachstumsreiz hervorrufen würde und die Amplitude des DOMS außerdem in direkter Relation zur Hypertrophie stehen würde.
Das könnte übrigens auch daran liegen, dass die Bedeutung der IGF-1 Expression im Zusammenhang mit Muskelwachstum überschätzt wird:
A functional insulin-like growth factor receptor is not necessary for load-induced skeletal muscle hypertrophy
Spangenburg EE, Leroith D, Ward CW, Bodine SC.
University of Maryland.
Abstract
Increasing the mechanical load on skeletal muscle results in increased expression of insulin-like growth factor I (IGF-I), which is thought to be a critical step in the induction of muscle hypertrophy. To determine the role of the IGF-I receptor in load-induced skeletal muscle hypertrophy, we utilized a transgenic mouse model (MKR) that expresses a dominant negative IGF-I receptor specifically in skeletal muscle. Skeletal muscle hypertrophy was induced in the plantaris muscle using the functional overload (FO) model, a model which has previously been shown to induce significant elevations of IGF-I expression in skeletal muscle. Adult male wild-type (WT) and MKR mice were subjected to 0, 7 or 35 days of FO. In control or unchallenged animals, the plantaris mass was 11% greater in WT compared to the MKR mice (P < 0.05). After 7 days of FO, plantaris mass increased significantly by 26% and 62% in WT and MKR mice, respectively (P < 0.05). After 35 days of FO, WT and MKR mice demonstrated significant increases of 100% and 122%, respectively, in plantaris mass (P < 0.05). Further, at no time point was the degree of hypertrophy significantly different between the WT and MKR mice. Previous research suggests that IGF-I induces muscle growth through activation of the Akt-mTOR signalling pathway; therefore, we measured the phosphorylation status of Akt and p70(s6k) in the WT and MKR mice after 7 days of FO. Significant increases of approximately 100% and approximately 200% in Akt (Ser-473) and p70(s6k) (Thr-389) phosphorylation were measured in overloaded plantaris from both WT and MKR mice, respectively. Moreover, no differences were detected between the WT and MKR mice. These data suggest that increased mechanical load can induce muscle hypertrophy and activate the Akt and p70(s6k) independent of a functioning IGF-I receptor.
J Physiol. 2008 Jan 1;586(1):5-6.
The role of IGF-I in skeletal muscle function
E. E. Spangenburg
Abstract:
Induction of insulin-like growth factor-I (IGF-I) expression is thought to be a major contributor to muscle development and to muscle adaptation in response to exercise training (1,2). IGF-I expression increases in skeletal muscle in response to mechanical load or muscle injury. The increase in IGF-I expression is an initiating event for downstream signaling events that are thought to regulate mechanisms including protein synthesis and cellular proliferation (1,2). Much of our understanding concerning the mechanistic roles of IGF-I has been delineated by gain of function experiments where exogenous IGF-I has been delivered to the muscle (3). Unfortunately, loss of function experiments has been prohibitive because traditional knockout models of the IGF-I system are often fatal. To gain a better understanding of IGF-I, my laboratory has utilized a transgenic mouse model that expresses a dominant negative IGF-I receptor specifically in skeletal muscle (MKR) (4). These mice express normal amounts of IGF-I, but due to the mutated IGF-I receptor the muscle does not respond to IGF-I exposure. These mice are viable, but exhibit ~20-40% reductions in skeletal muscle mass, with no differences detected in heart mass. We have used these mice to examine the role of IGF-I in muscle hypertrophy and signaling mechanisms that regulate protein translation. Specifically, we have found using the functional overload model (FO) that the muscle hypertrophic response of the MKR mice is equivalent to that of the WT mice (4). These data suggest that a functional IGF-I receptor is not necessary for muscle hypertrophy. Further, we have found that mutation of the IGF-I receptor does not prevent load-induction of the Akt-mTOR pathway in the FO model (4). These data indicate that when using a chronic model of mechanical loading activation of the IGF-I receptor is not critical for the induction of the Akt-mTOR signaling pathway. IGF-I is also thought to be critical in the recovery from muscle injury. Interestingly, in preliminary studies we have found that the MKR mice are very susceptible to contraction-induced muscle injury compared to WT mice. These data suggest that the IGF-I receptor may provide a protective effect to the muscle. Clearly, much of our understanding of the role of IGF-I continues to be unraveled, but it is clear that the role of IGF-I is complex and will necessitate more studies.
University College Dublin (2009) Proc Physiol Soc 15, SA19, Research Symposium
Der stärkere IGF-1 Response von exzentrischem, verglichen zu konzentrischem Training scheint also nicht maßgeblich zu sein.
Deshalb nun zu vermuten, die exzentrische Phase der Kontraktion während des Trainings wäre für das Muskelwachstum überflüssig und vielleicht sogar hinderlich, wäre falsch:
Influence of eccentric actions on skeletal muscle adaptations to resistance training
B. M. HATHER1, P. A. TESCH3, P. BUCHANAN2, G. A. DUDLEY1,*
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.[...]
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.
Acta Physiologica Scandinavica Volume 143, Issue 2, pages 177–185, October 1991
Schlussfolgerung
Ein effektives Krafttraining sollte also sowohl aus konzentrischen, als auch exzentrischen Kontraktionen bestehen. Das ursprünglich verbreitete Vorgehen im Krafttraining, beide Kontraktionsformen in direkter aufeinanderfolge einer dynamischen Bewegung miteinander zu verknüpfen, scheint optimal um größtmögliche Fortschritte zu erzielen.
Quellen:
1. Alfredson H, Pietilä T, Jonsson P, Lorentzon R. (1998). Heavy-Load Eccentric Calf Muscle Training For the Treatment of Chronic Achilles Tendinosis. Am J Sports Med May 1998 vol. 26 no. 3 360-366 .
2. Fahlström M, Jonsson P, Lorentzon R, Alfredson H. (2003). Chronic Achilles tendon pain treated with eccentric calf-muscle training. Knee Surg Sports Traumatol Arthrosc. 2003 Sep;11(5):327-33. Epub 2003 Aug 26.
3. Jonsson P, Wahlström P, Ohberg L, Alfredson H. (2005). Eccentric training in chronic painful impingement syndrome of the shoulder: results of a pilot study. Knee Surg Sports Traumatol Arthrosc. 2006 Jan;14(1):76-81. Epub 2005 May 5.
4. Bamman M, Shipp J, Jiang J, Gower B, Hunter G, Goodman A, McLafferty C and Urban R.(2001). Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans. AJP - Endo March 2001 vol. 280 no. 3 E383-E390.
5. Chesley A, MacDougall JD, Tarnopolsky MA, Atkinson SA and Smith K. (1992). Changes in human muscle protein synthesis after resistance exercise. Journal of Applied Physiology October 1992 vol. 73 no. 4 1383-1388.
6. Mayhew T, Rothstein J, Finucane S, Lamb R. (1995). Muscular adaptation to concentric and eccentric exercise at equal power levels. The American College of Sports Medicine 1995.
7. Adams G, Cheng D, Haddad F, Baldwin K. (2004). Skeletal muscle hypertrophy in response to isometric, lengthening, and shortening training bouts of equivalent duration. Journal of Applied Physiology May 2004 vol. 96 no. 5 1613-1618.
8. Spangenburg EE, Leroith D, Ward CW, Bodine SC. (2008). A functional insulin-like growth factor receptor is not necessary for load-induced skeletal muscle hypertrophy. J Physiol. 2008 Jan 1;586(1):5-6.
9. E. E. Spangenburg (2009). The role of IGF-I in skeletal muscle function. University College Dublin (2009) Proc Physiol Soc 15, SA19, Research Symposium.
10. Hather B, Tesch P, Buchanan P, Dudley G. (1991). Influence of eccentric actions on skeletal muscle adaptations to resistance training. Acta Physiologica Scandinavica Volume 143, Issue 2, pages 177–185, October 1991.
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