1. Specific Aims &
Hypothesis
Electromyography
(EMG) is the recording of muscle action potentials and mechanomyography (MMG)
is the recording of vibrations produced by contracting muscle. It has been suggested that EMG represents
the major changes in currents and voltages occurring whenever muscle fibers are
activated by their motorneurons independent of contractile tissues. Mechanomyography represents the contractile
tissues and may be useful for evaluating viscoelastic properties of muscle and
the tissues overlying the muscle.
Therefore, the use of surface EMG and MMG simultaneously provides a
non-invasive method of measuring muscle activation and muscle contraction.
Unfamiliar
and/or intense physical exercise is typically associated with skeletal muscle
cell membrane damage and soreness 24-72 hours following the exercise bout, a
phenomenon termed “Delayed Onset Muscle Soreness” (DOMS). Recent data indicates
that DOMS does not affect the EMG signal; therefore, the muscle is activated
normally. Muscle cell damage is
indicated by increased plasma creatine kinase activity; however, muscle
strength is not compromised. It is
possible that MMG would be sensitive to the altered contractile behavior and
edematous changes within the perimuscular connective tissue that occurs during
DOMS.
The
overall goal of this study is to determine the effects of DOMS on torque, EMG
and MMG. It is hypothesized that force
production will remain the same or possibly decrease (based on previous
studies). Furthermore, it is
hypothesized that the EMG signal will be unaltered (no changes in muscle
activation) and the MMG signal will decrease due to increased fluid retention
(inflammation response) and decreased cross-bridge cycling rates associated
with internal muscle injury. The MMG
signal is expected to return back to baseline measurements within 7-days of
treatment.
I.
To determine the effects of DOMS on torque production on
days 2, 3, and 7. We shall measure
force production (torque) and perceived pain of the quadriceps (leg) muscle
prior to treatment and three times post treatment. The data obtained will be used to determine force production and
perceived pain over 7 days.
II.
To determine the effects of DOMS on EMG on day 2, 3, and
7. We shall measure surface EMG of the
rectus femoris (leg) muscle prior to treatment and three times post
treatment. The data will be used to
measure muscle activation of the rectus femoris (leg) during force production
over 7-days.
III. To
determine the effects of DOMS on MMG on day 2, 3, and 7-days post
treatment. We shall measure MMG of the
rectus femoris (leg) muscle prior to treatment and three times post
treatment. The data will be used to
measure low-frequency vibrations produced by the rectus femoris (leg) muscle
during force production over 7-days.
2.
Significance
Delayed-onset muscle soreness (DOMS) is a common muscle problem among
athletes and individuals beginning an exercise program. Initially, damage caused by DOMS leads to an
inflammatory response followed by regeneration. However, these inflammatory changes are not correlated with
perceived soreness ratings, leaving the reasons for DOMS unanswered. Furthermore, current treatment protocols for
DOMS have yielded inadequate results.
It is the goal of this study to further our understanding of DOMS and
the healing process over 7-days by using the non-invasive techniques of EMG and
MMG to determine muscle function in the presence of DOMS. Should we determine changes in MMG as
hypothesized, future research can utilize MMG as a non-invasive technique to
monitor treatment protocols for DOMS.
Each subject will be paid $25 on completion of the study. If you are interested in participating in this study please contact sdrake@astate.edu or 972-3591.