1)The purpose of this study was to assess the influence of the duration of smartphone usage on cervical and lumbar spine flexion angles and reposition error in the cervical spine. The study included 18 healthy smartphone users (7 males and 11 females). We measured the kinematics of the upper and lower cervical and lumbar spine flexion angles and the reposition error of the upper and lower cervical spine after 3 s and 300 s smartphone use in sitting. A paired t-test was used to compare the effects of the duration of smartphone usage on the kinematics of cervical and lumbar spine flexion angles and reposition error. The flexion angles of the lower cervical and lumbar spine and the reposition error in the upper and lower cervical spine were significantly increased after 300 s smartphone of use (p<.05). However, the flexion angle of the upper cervical spine was not significantly different between the 3 s and 300 s smartphone of use (p>.05). These findings suggest that prolonged use of smartphones can induce changes in cervical and lumbar spine posture and proprioception in the cervical spine.
[Purpose] This study investigated the changes in electromyographic (EMG) activities of
the infraspinatus and posterior deltoid muscles during shoulder external rotation under
open kinetic chain (OKC) and closed kinetic chain (CKC) exercise conditions. [Subjects] In
total, 15 healthy males participated in this study. [Methods] Subjects performed shoulder
external rotations under CKC and OKC conditions while standing with and without weight
support provided by a height-adjustable table. Pressure biofeedback was used to ensure a
constant amount of weight support. The activities of the infraspinatus and posterior
deltoid muscles during shoulder external rotation were measured using a wireless surface
EMG system. The paired t-test was used to compare the EMG activities of the infraspinatus
and the posterior deltoid muscles and the ratio of the infraspinatus to the posterior
deltoid during shoulder external rotation under OKC and CKC conditions. [Results] The EMG
activity of the infraspinatus and the ratio of the infraspinatus to the posterior deltoid
activities were significantly increased, whereas the posterior deltoid activity was
significantly decreased under the CKC condition compared to the OKC condition.
[Conclusion] Clinicians should consider the CKC shoulder external rotation exercise when
they wish to selectively strengthen the infraspinatus.
Abstract. [Purpose] We investigated the effects of changing the resistance direction using an elastic tubing band on abdominal muscle activities during isometric upper limb exercises in a seated position.[Subjects] Twenty ablebodied volunteers (10 males, 10 females) were recruited for the study.[Methods] All subjects performed isometric upper limb exercises with an elastic tubing band involving three different shoulder movements (extension, flexion, and horizontal abduction). Surface electromyography (EMG) signals were recorded from the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) bilaterally during isometric upper limb exercises.[Results] There were significant differences in EMG activity of the bilateral RA during shoulder extension, shoulder horizontal abduction, and shoulder flexion. The EMG activities of the bilateral EO and IO were significantly higher in shoulder extension and horizontal abduction than in shoulder flexion when the subjects performed the arm exercise in the seated position. There was no significant difference between shoulder extension and horizontal abduction.[Conclusions] We suggest that upper limb extension and horizontal abduction using an elastic tubing band could be effective at improving abdominal muscle activities without trunk movement during isometric upper limb exercises.
[Purpose] The aim of this study was to investigate changes in electromyographic (EMG)
activity of the infraspinatus and posterior deltoid muscles during shoulder external
rotation under different shoulder flexion angles. [Subjects] Thirteen participants were
included in this study. [Methods] The participants performed isometric shoulder external
rotation at 45°, 90°, and 135° of shoulder flexion. A surface EMG system recorded the EMG
activity of the infraspinatus and posterior deltoid muscles during shoulder external
rotation. The changes in the muscle activity of infraspinatus and posterior deltoid and
ratio of infraspinatus to posterior deltoid muscle activity were analyzed using one-way
repeated-measures analysis of variance with Bonferroni’s correction. [Results] The
posterior deltoid activity was significantly decreased, while the ratio of the
infraspinatus to posterior deltoid activity was significantly increased at 45° of shoulder
flexion compared with 90° and 135° of shoulder flexion (p < 0.05). There were no
significant differences in the EMG activity of the infraspinatus among the three
conditions (p > 0.05). [Conclusion] These findings indicate that shoulder external
rotation at 45° of shoulder flexion effectively reduced the contribution of the posterior
deltoid activation to shoulder external rotation.
[Purpose] We investigated the effects of shoulder flexion loaded by an elastic tubing
band during squat exercises, by assessing electromyographic activities of the gluteus
maximus and gluteus medius. [Subjects] In total, 17 healthy males were recruited.
[Methods] Participants performed squat exercises with and without shoulder flexion loaded
by a tubing band. Gluteal muscle activities during the downward and upward phases of the
squat exercises were recorded using a surface electromyography (EMG) system. The mean
electromyographic activities of the gluteal muscles during squat exercises with and
without loaded shoulder flexion were compared using the paired t-test. [Results]
Electromyographic activities of the gluteus maximus and gluteus medius were greater in
both the upward and downward phases of the squat with loaded shoulder flexion.
[Conclusions] The combination of squat and loaded shoulder flexion can be an effective
exercise for increasing gluteal muscle activity.
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