Effects of Eccentric Contractions Induced Electrical Stimulation Training System on Quadriceps Femoris Muscle
Some reports have
showed that exercise involving eccentric contractions has a greater effect for
muscle strengthening because the high intensity of muscle loading can be
generated eccentric contraction compared to concentric or isometric
contractions.
Electrical stimulation
is a technique used to elicit a muscle contraction using electrical impulses. It
has been reported that electrical stimulation (ES) can be effective to induce
muscle strengthening. And its effectiveness is determined by the intensity of
muscle loading, as well as resistance exercise. However, some studies have also
indicated that ES can cause pain and discomfort.
In this study, the
authors developed an eccentric contraction induced electrical stimulation (ES)
training system. And the purpose of this study was to investigate whether the
eccentric contraction induced ES enhance the knee extension torque compared
with typical ES.
Twenty-two young
untrained men (age: 23 ± 3 years old) in the acute response trial (single
training) and seven untrained men in the long period training trial (for 6
weeks) were studied. The authors measured muscle thickness and knee extension
torque evoked by ES with eccentric contraction training system (ES + ECC) or ES
alone for the quadriceps muscle of men. The levels of pain and discomfort were
evaluated using numeric rating scale (NRS) and heart rate variability. The
results demonstrated that the knee extension torque of ES + ECC was higher than
that of ES alone in the acute response trial. There were no significant
differences in the levels of pain and discomfort between ES and ES + ECC.
Additionally, ES + ECC training for 6 weeks was effective on the quadriceps
muscle thickness and knee extension torque. In contrast, the ES alone training
failed to increase muscle thickness and knee extension torque.
In conclusion, these
results suggest that eccentric contraction induced ES would have the potential
to become an effective intervention to promote muscle strengthening.
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