Dear All,
It has been very interesting to read Dr. Siff's Paradox in eccentric
training. Based upon my own observations and experimental findings (I did
my DPhil in exercise-induced muscle damage and DOMS) I can observe the
following shortcomings in the argument put forward:
1. There is the assumption that the muscle is only coping with a given
load with its contractile apparatus. This immediately nulifies the effect
that tendons and peri- and intra-muscular collagen play in tension.
2. Perhaps I misunderstood but I think that it is also assumed that the
muscle is activated maximally during eccentric contractions. Again, EMG
studies (particularly by Newham and Jones, McGlynn and others and Friden)
have concluded that the increase in tension and EMG recordings observed
during eccentric contraction is due to maximal activation of fewer motor
units. This places the muscle under considerable stress, which leads to
damage, evident by increases in serum creatine kinase and symptoms such
as stiffness, swelling and pain, a phenomenon that most of us are
familiar with at the begining of a training season after our first spell
in the gym. However, the muscle responds to this insult by either
changing its activation pattern and/or strengthening the contractile
apparatus (for detailed explanations follow the work of Clarkson PM and
Armstrong RB; apologies for not including a full record, I have not got
it with me!).
Further more a myriad of physiological experiments have shown the
force-velocity curve to be true. This shows that during fast eccentric
contractions the tension developed by the muscle fibre may reach 150% of
that during isometric contractions.
3. the issue of training with eccentric exercise is a highly
controversial one. Of what I can deduct from what I read, eccentric
training results in a fast increase in the muscle's ability to lower more
weights (Friden et al 1988 i think). Unfortunately, this increase in
eccentric/plyometric tension is not followed by either a reciprocal
increase in concentric or isometric strength or muscle hypertropy. In
addition, such training protects the muscle from further damage (as a
matter of fact an eccentric bout of exercise has a protective effect
against exercise-induced muscle damage for up to 9 wks).
Eccentric contractions are a highly controversial issue and have
different meaning for the physiotherapist, the physiologist or the
bioengineer. They are quite fun though, because they prove our
limitations in understanding what nature is made of and how clever we can
be. From the first report in 1902 by Hough, we have gone very far. I
would like to see however a paper sumarising the definitive mechanism of
contraction and, even more, the mechanism of muscle damage. Very
interesting in this respect are the papers by Julian and Morgan (1979)
and Morgan 1990.
Anyway this is my two pence.
I will be looking forward for further contributions on the subject
Panos
Panos Barlas, BSc(Hons)PDD, DPhil, MCSP, SRP, LicAc
Lecturer
Department of Physiotherapy
School of Health and Social Sciences,
Coventry University,
Priory Street,Coventry, CV1 5FB
Tel: +44- (0)1203- 838980
Fax: +44- (0)1203- 838020
E-mail: [log in to unmask]
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