Changes in Skeletal Muscle Ultrastructure and Strength Performance following acute resistance exercise
Theses
Overview
Overview
abstract
The purpose of this study was to examine changes in
muscle ultrastructure and strength performance following a
single bout of elbow flexor resistance exercise. Eight
untrained males performed 8 sets of 8 repetitions at 80%
concentric 1 RM. One arm performed only the concentric (CON)
phase of the movement while the other performed only the
eccentric (ECC) phase. Maximum isometric (MVC), low (LV} and
high velocity (HV} concentric peak torque, and evoked
contractile property measurements of the elbow flexors were
made before and after the bout, and at 24, 48, 72 and 96 h.
Needle biopsies were obtained from the biceps brachii prior to
the exercise, immediately post-exercise from each arm (POSTCON,
POST-ECC}, and 48 h post-exercise from each arm (48H-CON,
48H-ECC). Electron microscopy was used to quantify the extent
of fiber disruption in each sample. The severity of
disruption was classified as focal (FOC}, moderate (MOD}, or
extreme (EXT}. All strength measurements decreased (P s; o. 05}
below pre-exercise values immediately post-ex in both arms,
but dramatic differences were observed between arms during the
subsequent recovery period. MVC, LV, HV and peak twitch
torque (PTT) recovered to pre-ex values by 24 h in the CON
arm. In the ECC arm, HV did not recover for at least 72 h,
and MVC, LV and PTT remained depressed at 96 h. ANOVA
revealed a greater (P s; 0.05) number fibers were disrupted in
the POST-CON, POST-ECC, 48H-CON and 48H-ECC samples compared
to BASE. Significantly more fibers appeared disrupted in the
POST-ECC (82%) and 48H-ECC (80%) samples compared to the POSTCON
(33%) and 48H-CON (37%) samples, respectively. In
addition, the POST-ECC (41%) and 48H-ECC (50%) samples
contained a greater number of fibers with EXT disruption
compared to the POST-CON (13%) and 48H-CON (17%) samples.
Decreases in MVC at 48 h correlated (P ~ 0.05) with the extent
of EXT disruption in the 48H-CON and 48H-ECC samples. These
data indicate that both the CON and ECC phase of weightlifting
produce myofibrillar disruption, with the greatest disruption
occurring during the ECC phase.
This study was supported by the Natural Sciences and
Engineering Research Council of Canada.
