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Context: The quadratus lumborum (QL) is expected to contribute to segmental motor control of the lumbar spine to prevent low back pain. It has different layers (anterior [QL-a] and posterior [QL-p] layers), whose functional differences are becoming apparent. However, the difference between the QL-a and QL-p activities during bridge exercises utilized in rehabilitation is unclear. Objective: To compare QL-a and QL-p activities during bridge exercises. Design: Repeated-measurement design was used to assess electromyographic activity of trunk muscles recorded during 14 types of bridge exercises. Setting: University laboratory. Participants: A total of 13 healthy men with no history of lumbar spine disorders participated. Intervention: The participants performed 14 types of bridge exercises (3, 3, and 8 types of side bridge, back bridge, and front bridge [FB], respectively). Main Outcome Measures: Fine-wire electromyography was used for QL-a and QL-p activity measurements during bridge exercises. Results: Both QL-a and QL-p showed the highest activity during the side bridge with hip abduction (47.3% [29.5%] and 43.0% [32.9%] maximal voluntary isometric contraction, respectively). The activity of the QL-a was significantly higher than that of the QL-p during back bridge with ipsilateral leg lift and FB elbow–toe with ipsilateral arm and contralateral leg lift (P P Conclusion: This study indicates different regional activities; the QL-a activated during the back bridge with ipsilateral leg lift and FB with ipsilateral arm lift, and the QL-p activated during the FB with ipsilateral leg lift. These results have implications for the rehabilitation of low back pain or lumbar scoliosis patients based on QL recruitment.

Background Changes in trunk and hip muscles are believed to be important in subjects with nonspecific chronic low back pain (NSCLBP), but little is known about specific changes, or how they might be affected by core stabilization exercises. The aim of this study was to compare six key muscles before and after these exercises. Methods Thirty two NSCLBP patients were assigned randomly into two groups: exercise (n = 17) and control (n = 15). On 5 days per week for 4 weeks, the Exercise group performed 16 core stabilization exercises and the Control group received transcutaneous electrical nerve stimulation and a ‘hot-pack’. Surface electromyography (EMG) was used to assess maximum bilateral activity of transversus abdominis (TrA), multifidus (MF) and gluteus maximus (Gmax) muscles. Ultrasound imaging was used to measure the rest and contracted thickness of these muscles. Pain and disability were assessed using a visual analogue scale (VAS) and the Oswestry Disability Index. Results When left and right-side muscle data were combined, two-way ANOVAs showed a nonsignificant interaction effect for all dependent variables (P > 0.05), significant time effects on resting muscle thickness for TrA (P = 0.01), MF (P = 0.041) and Gmax (P = 0.003), EMG signals of TrA (P = 0.038), pain and disability (P = 0.000). There were a significant group effect on contracted thickness for TrA (P = 0.032) and Gmax (P = 0.026) and disability (P = 0.017). Conclusions Core stabilization exercises increased contracted thickness of TrA and Gmax muscles and decreased disability in subjects with NSCLBP.

Abnormal foot motion is considered to be related to sports related injuries. This study aimed to identify the relationship between calf muscle activity and inter-segment coordination of the foot during single-leg drop jumps. Eleven healthy men participated and performed single-leg drop jumps from a 30-cm box. Muscle activity of the tibialis posterior (TP), flexor digitorum longus, peroneus longus (PL) and gastrocnemius were measured. The rearfoot and midfoot segment angle from landing to leaping were calculated according to the Rizzoli Foot Model and time scaled to 100%. A modified vector coding technique was employed to classify inter-segment coordination of every 1% into four patterns (in-phase, anti-phase, rearfoot phase,and midfoot phase). The relationship between percentage of each pattern and muscle activity levels were statistically analysed with correlation coefficient. The TP showed a significant positive correlation with percentage of in-phase in coronal plane (

OBJECTIVE Pelvic tilt exercises are used clinically to correct lumbopelvic alignment. The anterior and posterior layers of the quadratus lumborum are important for pelvic motor control in the coronal plane. This study aimed to evaluate whether the anterior and posterior activity is related to the pelvic tilt angle during pelvic tilt exercises. DESIGN The study design was single-occasion repeated measures in a randomized manner. Twelve healthy men performed the four directions of the pelvic tilt exercises (anterior or posterior pelvic tilt and lateral pelvic elevation on the ipsilateral or contralateral measurement side). The electromyographies of the anterior and posterior were recorded using intramuscular fine-wire electrodes and normalized to isometric peak electromyography. RESULTS The activity of the anterior and posterior during lateral pelvic elevation on the ipsilateral measurement side (19.0 ± 16.0 percent of maximal voluntary isometric contraction) was significantly higher than that during other directions of the pelvic tilt exercises (P < 0.01). There was a significant positive correlation between the anterior activity and the maximum change angles of pelvic tilt during lateral pelvic elevation on the ipsilateral measurement side (r = 0.674, P = 0.016). CONCLUSIONS The anterior activity was related to a large lateral pelvic elevation angle on the ipsilateral side during pelvic tilt exercises.

Objective To identify injuries and physical characteristics affecting swimmers’ performance. Design Prospective study. Setting Laboratory-based. Participants Sixty-four Rio Olympic candidates (36 men, 28 women), who were high level swimmers ranked among the top 32 in the 2014 World Ranking in swimming. The participants were categorized into the Olympian group (n = 25), swimmers who were consecutively selected for the Olympic team, and the non-Olympian group (n = 39), swimmers who were not. Main outcome measures Four months prior to the Olympic qualification in 2016, an orthopedist and two physical therapists evaluated injuries and 11 physical characteristics of the swimmers. The prevalence of total overuse injuries, shoulder and low back injury, and physical characteristics were compared between the two groups. Results The female swimmers in the non-Olympian group had a 53.3% prevalence of total overuse injuries, which was significantly higher than that of those in the Olympian group with 15.4% (p = 0.037). The prevalence of total over use injuries in male swimmers in both the Olympian and non-Olympian groups was 41.7%. Female Olympian group showed that the shoulder external rotation range of motion was significantly less than that of non-Olympian group (97.8 ± 5.7 and 103.6 ± 7.3, p = 0.046). Conclusions In female swimmers, total overuse injuries four months before an important competition influence their performance at the event.

The purpose of this study was to clarify the influence of different postures on the activity of the shoulder girdle and lower back muscles while using a smartphone. Sixteen healthy male participants maintained two postures while using a smartphone : a good posture in which the tragus and acromion were closer to the vertical line passing through the greater trochanter, and a poor posture in which the tragus and acromion were farther from the vertical line passing through the greater trochanter. The target muscles were the rhomboid major (Rhom), upper trapezius, middle trapezius, lower trapezius (LT), lumbar erector spinae (LES), and lumbar multifidus (LMF). The activities of the Rhom and LT were significantly lower with poor posture than those with good posture. The activities of LES and LMF were significantly higher with poor posture than those with good posture. The results of this study indicated that poor posture was associated with hypoactivity of the shoulder girdle muscles and hyperactivity of the lower back muscles when compared with good posture. Poor posture for prolonged periods while using a smartphone would lead to malfunction of the shoulder girdle muscles and musculofascial lower back pain. J. Med. Invest. 67 : 274-279, August, 2020.

The purpose of this study was to examine the influence of a history of low back pain (LBP) on pelvic and lumbar kinematics during baseball hitting. Twenty collegiate male baseball players (age, 21±1 years; height, 172.8±4.7 cm; weight, 72.7±6.2 kg; baseball experience, 13±1 years) performed 5 bat swings. Participants were categorized into the LBP group (n=10) or control group (n=10) based on having experienced lumbar spine pain due to bat swing that lasted more than 24 h within the last 12 months. Three-dimensional kinematic data of the pelvis and lumbar spine during bat swing were measured. Two-way ANOVAs were used to compare pelvic and lumbar kinematics throughout the bat swing between groups, and independent t-tests were used to compare the other outcomes between groups. There was a significant main effect between groups in lumbar flexion angle throughout the bat swing (p=0.047). The mean lumbar flexion angle of the LBP group throughout the bat swing was less than that of the control group. Additionally, the peak angular velocity of lumbar flexion of the LBP group was significantly faster than that of control group (p=0.047). These results can be helpful for longitudinal studies that identify the risk factors of LBP due to bat swing.

The nordic hamstring exercise (NHE) is a dynamic lengthening hamstring exercise that requires trunk and hip muscles activation. Thigh muscles activation, specifically hamstring/quadriceps contractions has been previously examined during NHE. Trunk and hip muscles activity have not been enough studied. The aim of this study was to analyze of hip and trunk muscles activity during NHE. Surface electromyography (EMG) and kinematic data were collected during NHE. Ten healthy men with the age range of 21-36 years performed two sets of two repetitions with downward and upward motions each of NHE. EMG activity of fifteen trunk and hip muscles and knee kinematic data were collected. Muscle activity levels were calculated through repeated measure analysis of variance in downward and upward motions, through Paired t-test between downward and upward motions and gluteus maximus to erector spine activity ratio (Gmax/ES ratio) using Pearson correlation analyses were evaluated. Semitendinosus and biceps femoris muscles activity levels were the greatest in both motions and back extensors and internal oblique muscles activity were greater than other muscles (P

ObjectivesThis study aimed to clarify the trends of injury occurrence in the Japan national swim team for 15 years and to evaluate the effectiveness of the lumbar injury prevention project. It also aimed to verify the incidence of swimming-related injuries among swimmers by sex, age and swimming style.MethodsThe target group comprised 488 swimmers who participated in the Olympics, Asian Games and Universiade from 2002 to 2016; we compiled data for the total number of injuries in each body part. The lumbar injury prevention project started in 2008 and included two components (deep trunk muscle exercises and evaluation of lumbar disc degeneration using MRI). We analysed the prevalence of lumbar injury before (2002–2008) and after (2009–2016) implementation of the lumbar injury prevention project by χ2 test. We compared age, sex and swim strokes between the injured and non-injured groups by χ2 test and unpaired t-test.ResultsThe most common injury site was the lower back, followed by the shoulder and knee. The lumbar injury prevalence was significantly lower after implementation of the prevention project (23.5% vs 14.8%; pConclusionsLumbar injury prevention intervention might be effective to prevent lower back injury in swimmers. Injury risk factors included female and old age; younger female athletes should prevent the development of injuries as they mature.

[Purpose] The purpose of the study was to assess the muscle activity change of the tibialis posterior, flexor digitorum longus, and peroneus longus during gait with orthoses. [Subjects and Methods] Sixteen healthy males participated in this study. Activity of each muscle was measured by using fine-wire and surface electromyography. Gait task was performed by the participants barefoot, with footwear and with orthoses. The electromyography data from a stance phase of each gait trial were used for analysis. The stance phase was divided into contact, midstance, and propulsion phases. The data from ten participants were extracted for final analysis, as electromyography measurements were unsuccessful for the other six. [Results] The results demonstrated that orthoses significantly reduced the tibialis posterior muscle activity in the propulsion phase compared to that in the barefoot condition. Although there was a significant difference in the midstance phase, post hoc analysis did not indicate significant differences among the phases. No significant electromyography amplitude change was detected in flexor digitorum longus and peroneus longus. [Conclusion] Orthothes reduced the tibialis posterior activity level during gait. This result may be beneficial for patients with injuries related to excessive activity of tibialis posterior.

This study aimed to clarify the difference in the onset of EMG activity between eight trunk muscles, including the anterior (QL-a) and posterior (QL-p) layers of the quadratus lumborum during rapid shoulder joint abduction. Thirteen healthy men participated in this study. Electromyography of the QL-a, QL-p, transversus abdominis (TrA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), lumbar multifidus (LMF), lumbar erector spinae (LES) on non-movement side, and middle deltoid (MD) on the movement side were measured. Subjects who were standing in a relaxed position performed rapid shoulder abduction with the dominant hand after light stimulus with or without a 3 kg wrist weight. Two-way ANOVA (muscles × weight conditions) was used to compare the onset of trunk muscles relative to that of MD. There was a significant main effect of the muscles. The onset of the QL-a, QL-p, and TrA was significantly earlier than that of the IO, EO, LMF, and LES (P 0.01). This result suggests that the activities of the QL-a, QL-p, and TrA have a crucial role in controlling the center of mass within the base of support and stabilizing the lumbar spine in the coronal plane during shoulder abduction.

Objective Exercises for lower leg muscles are important to improve function. To examine the influence of foot position on lower leg muscle activity during heel raises. Design Cross-sectional laboratory study. Setting Laboratory. Participants Fourteen healthy men participated in this study. Main outcome measures The muscle activity levels of the tibialis posterior (TP), peroneus longus (PL), flexor digitorum longus (FDL) and medial gastrocnemius (MG) were measured. The heel raises consisted of three foot positions: 1) neutral, 2) 30° abduction, and 3) 30° adduction. The EMG data for five repetitions of each foot position were normalized to maximum voluntary contraction. One-way repeated measure ANOVA was employed for statistical analysis. Results The muscle activity level of TP, PL and FDL was significantly different between the three foot positions during the heel raises. TP and FDL showed the highest activity level in 30° foot adduction while PL demonstrated the highest activity level in 30° foot abduction. Conclusions Heel raises with 30° foot adduction and abduction positions can change lower leg muscle activity; These findings suggest that altering foot posture during the heel raise exercise may benefit patients with impaired TP, PL or FDL function.