Affiliations: [a] Department of Sports Medicine and Biology of Physical
Activity, Faculty of Physical Education and Sports Science, University of
Athens, Athens, Greece
Abstract: This study investigated the hypothesis that isotonic muscle
performance following mild muscle damage would be disproportionately affected
when measured at different parts of the range of motion. Seven male volunteers
performed 50 maximal isometric contractions with the elbow flexors at a
lengthened position. Maximal isotonic performance was measured before and for
four days post-exercise at two parts of the range of motion of elbow flexion,
including mainly the descending (L) or the ascending limb (S) of the
angle–force curve. On day 1 post-exercise, muscle damage was evidenced by
a decrease in peak isometric force (−20.3 ± 2.7%, p<0.01), a
shift in optimum angle for force generation towards a greater elbow angle (by
0.12 ± 0.03 rad, p<0.05), and an increase in serum creatine kinase
activity and muscle soreness (P<0.01). Isotonic performance indices were
decreased only in the S condition (p<0.01). Shift in optimum angle and
isotonic performance indices recovered on day 2. The disproportionate decrease
in isotonic performance in the S condition may be explained by the shift of the
optimum angle towards a longer muscle length, which would benefit force
generation at elbow angles beyond the optimum angle but impair force at the
more acute elbow angles.
