Sign in to follow this  
FCB

Negativ fase

Recommended Posts

Halløjsa.

Jeg har aldrig rigtig forstået, hvorfor eccentrisk træning giver så stor hypertrofi-respons, som jeg har ladet mig fortælle den gør. Kunne nogen af Jer ikke prøve at forklare det, eller lægge nogle links ud, der kan forklare det rent fysiologisk og biokemisk. :)

På forhånd tak...

Share this post


Link to post
Share on other sites
Adaptive responses to muscle lengthening and shortening in humans.

Hortobagyi T, Hill JP, Houmard JA, Fraser DD, Lambert NJ, Israel RG.

Biomechanics Laboratory and Department of Medicine and Physical Therapy, East Carolina University, Greenville, North Carolina 27858, USA.

We tested the hypothesis that exercise training with maximal eccentric (lengthening) muscle actions results in greater gains in muscle strength and size than training with concentric (shortening) actions. Changes in muscle strength, muscle fiber size, and surface electromyographic (EMG) activity of the quadriceps muscle were compared after 36 sessions of isokinetic concentric (n = 8) or eccentric (n = 7) exercise training over 12 wk with use of a one-leg model. Eccentric training increased eccentric strength 3.5 times more (pre/post 46%, P < 0.05) than concentric training increased concentric strength (pre/post 13%). Eccentric training increased concentric strength and concentric training increased eccentric strength by about the same magnitude (5 and 10%, respectively, P > 0.05). Eccentric training increased EMG activity seven times more during eccentric testing (pre/post 86%, P < 0.05) than concentric training increased EMG activity during concentric testing (pre/post 12%). Eccentric training increased the EMG activity measured during concentric tests and concentric training increased the EMG activity measured during eccentric tests by about the same magnitude (8 and 11%, respectively, P > 0.05). Type I muscle fiber percentages did not change significantly, but type IIa fibers increased and type IIb fibers decreased significantly (P < 0.05) in both training groups. Type I fiber areas did not change significantly (P > 0.05), but type II fiber area increased approximately 10 times more (P < 0.05) in the eccentric than in the concentric group. It is concluded that adaptations to training with maximal eccentric contractions are specific to eccentric muscle actions that are associated with greater neural adaptation and muscle hypertrophy than concentric exercise.

Og her er lige en røvfuld fra HST siden:

1: Nosaka K, Newton M. Repeated Eccentric Exercise Bouts Do Not Exacerbate Muscle Damage and Repair. J Strength Cond Res. 2002 Feb;16(1):117-122.

2: Nosaka K, Newton M. Concentric or eccentric training effect on eccentric exercise-induced muscle damage. Med Sci Sports Exerc. 2002 Jan;34(1):63-9.

3: Proske U, Morgan DL. Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications. J Physiol. 2001 Dec 1;537(Pt 2):333-45.

4: Nosaka K, Newton M, Sacco P. Responses of human elbow flexor muscles to electrically stimulated forced lengthening exercise. Acta Physiol Scand. 2002 Feb;174(2):137-45.

5: Allen DG. Eccentric muscle damage: mechanisms of early reduction of force. Acta Physiol Scand. 2001 Mar;171(3):311-9.

6: Clarkson PM. Eccentric exercise and muscle damage. Int J Sports Med. 1997 Oct;18 Suppl 4:S314-7.

7: Paddon-Jones D, Abernethy PJ. Acute adaptation to low volume eccentric exercise. Med Sci Sports Exerc. 2001 Jul;33(7):1213-9.

8: Nosaka K, Sakamoto K, Newton M, Sacco P. How long does the protective effect on eccentric exercise-induced muscle damage last? Med Sci Sports Exerc. 2001 Sep;33(9):1490-5.

9: McHugh MP, Connolly DA, Eston RG, Gleim GW. Exercise-induced muscle damage and potential mechanisms for the repeated bout effect. Sports Med. 1999 Mar;27(3):157-70.

10: Nosaka K, Sakamoto K, Newton M, Sacco P. The repeated bout effect of reduced-load eccentric exercise on elbow flexor muscle damage. Eur J Appl Physiol. 2001 Jul;85(1-2):34-40.

11: Rennie MJ. How muscles know how to adapt. J Physiol. 2001 Aug 15;535(Pt 1):1.

12. Nosaka K, Sakamoto K. Effect of elbow joint angle on the magnitude of muscle damage to the elbow flexors. Med Sci Sports Exerc. 2001 Jan;33(1):22-9.

13: Lieber RL, Friden J. Morphologic and mechanical basis of delayed-onset muscle soreness. J Am Acad Orthop Surg. 2002 Jan-Feb;10(1):67-73.

14: Nosaka K, Clarkson PM. Influence of previous concentric exercise on eccentric exercise-induced muscledamage. J Sports Sci. 1997 Oct;15(5):477-83.

15: Carson JA. The regulation of gene expression in hypertrophying skeletal muscle. Exerc Sport Sci Rev. 1997;25:301-20.

16:. Lieber RL, Friden J. Mechanisms of muscle injury after eccentric contraction. J Sci Med Sport. 1999 Oct;2(3):253-65.

17: Nosaka K, Clarkson PM. Muscle damage following repeated bouts of high force eccentric exercise. Med Sci Sports Exerc. 1995 Sep;27(9):1263-9.

God læselyst ;)

Share this post


Link to post
Share on other sites

Der er også en artikel i det nye nr. af Workout and Fitness, som er god, men tager jeg meget fejl hvis det er dig der har skrevet den Cilius? B)

Share this post


Link to post
Share on other sites
Guest PlayboY

Man siger jo at når man kører i den exentriske face i et HST program, skal man køre med 130% over max løft, fra dengang man startede..

Men så lige et spørgsmål.

Når man kører excentrisk, skal man så selv presse alt hvad man kan opad, og så er der en der løfter det sidste stykke ligesom i en forced rep.. Eller skal spotteren løfte hele lortet, og så skal man selv kun køre den meget langsomt ned? :blink:

Share this post


Link to post
Share on other sites

Den sidste, men du sænker den ikke laaangsomt ned.. en 2-3 sekunder er rigeligt - og bruger du mere, bliver det i stedet opfattet som en quasi isometrisk udførelse af musklen ;)

Share this post


Link to post
Share on other sites

cilius ->

Lige en drillende bemærkning.

Er selvfølgelig enig i at forced reps generelt er noget man skal holde sig fra. I det meste af HST-cyklusen er jeg desuden helt enig at dette helt skal undgås. Men jeg kom alligevel til at tænke på........

Forced reps er primært dårligt fordi det (over-)stresser nervesystemet og delvist fordi "løftestrukturen", set som et hele, overbelastes en anelse for meget over tid. Men i HST'ens sidste minicyklus er vi altså tæt på at kunne holde 7-14 dages total neural pause, så der skulle vel ikke være nogen problemer for, at man gennem de sidste 3-6 træningspas kan træne med noget der nærmer sig forced reps!!!! Herved kunne man udover den excentriske del af løftet også kæmpe de sidste ressourcer ud af systemet med lidt hjælp fra spotteren. Argumentet burde sikkert også for en HST uden excentrisk del - dog ville de forced reps her sikkert (måske ;) ) kun være relevant de sidste to træningspas, idet det kun er her man presses "ud over evne".

Bare noget jeg har gået og tænkt på :unsure::rolleyes:

Edited by jarvig13

Share this post


Link to post
Share on other sites

Hvis vi holder den i HST tankegangen:

Muskler vokser i respons på belastninger de ikke er konditioneret i forhold til. Hvis du har overskredet din 5rm, og kombinerer den eccentrisk del med forced reps i den concentriske del, så vil belastningen du udsætter musklen for i sidste gentagelse ikke være nær så stor som i den første (trætheds akkumulation). Du kan ikke skabe mere kraft end din MVC (maximal voluntary contraction), hvorfor forced reps i hypertrofi øjemed er totalt uanvendelige (klart der kommer et fantastisk pump og udmattelse - men det har i store træk intet med sagen at gøre).

Den neurale udmattelse derimod er fantastisk, men eftersom det er noget vi langt fra ønsker at stimulere, så er pointen og motivationen for brugen af forced reps stadig mangelfuld.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this