Force Production Eccentric and Concentric Actions

[Guest guest]

In vitro conditions (without nerve and blood supply), muscles produce

greater force during eccentric than concentric contractions measured

with isokinetics apparatus in physiological liquid and with artifical

electrical stimulation. Mechanism for this larger forces (during

eccentric contractions) are author-dependent: Jaric states that it is

because viscosity in muscles (which resists movement speed, and in

eccentric contraction is in same direction as aktin-miosin force, thus

we get larger force), and Enoka (correct me if I am wrong) states it

is because changes in actin-myosin cycle!

If there is a governor that limits maximum isometric force (strength

deficit) in vivo (with nerve and blood supply – normal muscle) to

protect tendons, joints and muscles itself, then why does he

(governor) allows greater forces in eccentric contraction? Why doesn't

he (governor) reduce muscle activation, so does muscle produce same

maximum force in isometric conditions and in eccentric condition? And

if the larger isometric force than allowed by governor, harms tendons,

joints and muscles, why doesnt larger eccentric force create damage?

Or put another word:

Maximum maximorum isometric strength (via artifical stimulation) = 100N

Maximum isometric force MVC = 70N

MVC force during eccentric contraction (at some predef speed) = 90N

(or more)

Is the maximum isometric MVC force is limited because of protection,

then why MVC force during eccentric contraction IS NOT limited, and

why doesn't it produce any damage?

Mladen Jovanovic (student 4th year)

Department of strength training and conditioning

Faculty of sport and physical education

University in Belgrade

Serbia and Montenegro