Synergistic Dominance Induced by Hip Extension Exercise Alters Biomechanics and Muscular Activity During Sprinting and Suggests a Potential Link to Hamstring Strain.

ABSTRACT: Iguchi, J, Hojo, T, Fujisawa, Y, Kuzuhara, K, Yanase, K, Hirono, T, Koyama, Y, Tateuchi, H, and Ichihashi, N. Synergistic dominance induced by hip extension exercise alters biomechanics and muscular activity during sprinting and suggests a potential link to hamstring strain. J Strength Cond Res 37(9): 1770-1776, 2023-Hamstring strain is likely to occur during the late swing phase or the first half of the stance phase in sprinting. During the late swing phase, the hamstrings and gluteus maximus (Gmax) contract eccentrically to decelerate the lower limb. We hypothesized that, when the Gmax becomes dysfunctional because of delayed onset muscle soreness (DOMS), the hamstring workload is increased (i.e., there is synergetic dominance), which could lead to an increased risk of strain. A total of healthy 15 male undergraduate or graduate students (age 23.1 ± 1.28 years) were recruited to perform exercises and maximal sprints. On day 1, before subjects performing DOMS-causing exercises, and on day 3, while subjects were experiencing DOMS in the Gmax, lower-limb biomechanical and muscle activity data were recorded using a motion analysis system and electromyography (EMG), respectively. Data were analyzed and compared between day 1 and day 3. Hip flexion angle on day 3 was significantly lower than that on day 1, but the opposite was true for the knee flexion angle (P < 0.05). Vastus medialis (VM), biceps femoris (BF), and Gmax muscle activities on day 3 were significantly higher than those on day 1 (P < 0.05). Peak propulsive forces on day 3 were significantly higher than those on day 1 (P < 0.05). Kinematic changes such as decreased hip flexion angle and EMG changes such as increased BF EMG activity on day 3 to compensate for the loss of function of the Gmax may potentially increase the risk of hamstring strain.

Immediate effects of stance and swing phase training on gait in patients with stroke.

To compare the effects of gait trainings targeting the stance (stance training) and the swing phases (swing training) among the subjects with stroke, and quantify the characteristics in the subjects who benefitted from either the stance training or the swing training. Sixteen subjects with stroke performed the stance training, which focused on the center of pressure to move from the heel to the forefoot, and the swing training, which focused on the improvement of hip flexion in the swing phase. To investigate the immediate effects of the stance training and the swing training, the instrumented gait analysis was performed before and after training. To quantify the characteristics, subjects were divided into two groups based on the gait speed change. These two groups were compared using clinical examinations. After the stance training, the center of pressure displacement of the paretic limb was increased compared with the swing training. Subjects who benefitted from the stance training had slower Timed Up and Go and weaker paretic hip muscle strength than those who benefitted from the swing training. Stance training may be more effective in subjects with slower Timed Up and Go outcomes and weaker hip muscles.

Gait kinematics and physical function that most affect intralimb coordination in patients with stroke.

BACKGROUND: Disturbed lower limb coordination is thought to limit gait ability in patients with stroke. However, the relationship of lower limb coordination with gait kinematics and physical function has not yet been clarified. OBJECTIVE: The purpose of the study was to clarify the gait kinematic and physical function variables that most affect intralimb coordination by using the continuous relative phase (CRP) between the thigh and shank. METHODS: Fifteen participants with stroke were enrolled in this study. Kinematic and kinetic measurements were recorded during gait at preferred speeds. CRP was defined as the difference between the thigh and shank phase angles. RESULTS: Stepwise analysis revealed that non-paretic CRP during the propulsive phase was a determinant of gait speed. The paretic knee extension and flexion angles were determinants of the CRP during the propulsive phase in the non-paretic limb. Stepwise analysis showed that the paretic knee extension angle was a determinant of the CRP during the propulsive phase in the paretic limb. Stepwise analysis revealed that the paretic knee extensor muscle strength was a determinant of the CRP during the propulsive phase in both limbs. CONCLUSIONS: Our study indicates that improvement in knee movement during the stance phase may improve coordination.

Mechanical energy efficiency for stepping up and down in persons with medial knee osteoarthritis.

BACKGROUND: Energetic cost contributes to movement impairments observed during stair negotiation in persons with knee osteoarthritis. Specifically, the intersegmental mechanical energy exchange may be diminished in the presence of pathologies. RESEARCH QUESTION: The purpose of this study was to evaluate mechanical energy efficiency in persons with knee osteoarthritis during stepping up and down based on mechanical energy analysis. METHODS: Sixteen patients with medial knee osteoarthritis and 16 age-matched controls participated. A three-dimensional motion analysis system and force platforms were used to acquire biomechanical data. The participants were instructed to ascend/descend a 2-step staircase. The mechanical power exhibited during the stance phase at the lower step of the staircase were computed. Mechanical Energy Expenditure (MEE) was calculated as the integral of net joint power at each joint. Mechanical Energy Compensation (MEC) was defined as the proportion of muscle energy compensated by inter-segmental energy transfer. According to energy transfer modes, MEE and MEC were determined separately as three phases: concentric and eccentric transfer phases and no-transfer phase. RESULTS: While stepping up, the patient group performed the task with less MEC at the ankle joint, which was observed prior to push-off. The patient group displayed less mechanical energy transfer from the shank to the foot segment. The concentric MEC at the hip joint in the late-stance phase of stepping down was lower in the patient group, which meant patients demonstrated less mechanical energy transfer from the pelvis to the thigh segment. SIGNIFICANCE: It was disclosed that persons with knee osteoarthritis demonstrated less mechanical energy transfer while stepping up and down.

Movement variability response to change in the rate of hopping.

Movement variability is often considered undesirable, but growing evidence demonstrates positive aspects of variability. During unipedal hopping, control of limb stiffness and limb length are paramount. PURPOSE: The purpose of this study was to compare two methods of measuring movement variability that provide information at the task level, and their capacities to illuminate the neuromotor control system's response to change in hopping rate. METHODS: The typical task-level movement variability measure of the standard deviation of vertical limb length was compared to uncontrolled manifold analysis. We examined the relationship between change scores in deviation from spring-mass model-type behavior and these two variability measures for the shift from typical (2.3 Hz) to slow (1.7 Hz) hopping. RESULTS: The change scores for deviation from spring-mass model-type behavior and vertical limb length standard deviation demonstrated no correlation ( p = 0.784, R = 0.051). In contrast, the change scores for deviation from spring-mass model-type behavior and the uncontrolled manifold analysis measure demonstrated a moderate correlation ( p = 0.004, R = 0.502). CONCLUSIONS: Uncontrolled manifold analysis considers not just variability in the sense of error, but illustrates how the neuromotor control system distributes movement variability into performance-irrelevant and performance-destabilizing subspaces. As such, this type of analysis may be more effective at illuminating global control aspects of movement variability than the typical variability measure of limb length standard deviation.

Back muscle activity and sagittal spinal alignment during quadruped upper and lower extremity lift in young men with low back pain history.

BACKGROUND: Quadruped upper and lower extremity lift (QULEL) is performed for selective training of the lumbar multifidus muscle in patients with low back pain (LBP) or individuals with LBP history (LBPH). However, the activities of the back muscles and sagittal spinal alignment during QULEL are not clarified in individuals with LBPH. RESEARCH QUESTION: This study aimed to analyze the activities of the back muscles and sagittal spinal alignment during QULEL in young male with LBPH. METHODS: The study comprised 9 asymptomatic young men and 8 young men with LBPH. The activities of the lumbar multifidus, latissimus dorsi and thoracic erector spinae, and lumbar erector spinae muscles were measured using surface electromyography. The flexion angles of the upper and lower thoracic spine, and extension angle of the lumbar spine were measured using a 6-DF electromagnetic motion tracking system. The association with LBPH was investigated using multiple logistic regression analysis with a forward selection method, with the activities of the back muscles, sagittal spinal alignment, age, body height, and body weight as independent variables. RESULTS: Multiple logistic regression analysis (p = 0.0002) showed that the activity of the latissimus dorsi and thoracic erector spinae muscles in the side on which the lower extremity was lifted and body height were significant and independent determinants of LBPH, but other factors were not. SIGNIFICANCE: The results of this study suggest that the activity of the latissimus dorsi and thoracic erector spinae muscles increases while there are no decrease in activity of the lumbar multifidus muscle and excessive extension of the lumbar spine during QULEL in young men with LBPH.

Gait strategies to reduce the dynamic joint load in the lower limbs during a loading response in young healthy adults.

Reducing external joint moments during gait can lead to a reduction in dynamic joint load. There has yet to be a detailed investigation of gait strategies that can reduce external joint moments by decreasing the magnitude of ground reaction force (GRF) without reducing the walking speed. The objectives of this study were to verify whether it is possible to reduce external joint moments by decreasing the GRF magnitude without reducing the walking speed and to identify the alternative walking strategy involved in young healthy adults. This study included 14 young healthy subjects. They performed two types of walking: normal and impact reduction walking. For impact reduction walking, the subjects walked in a manner that reduced the impact upon foot contact. Cadence and step length were unified between the two conditions. The walking speed, peak value of vertical GRF, braking-accelerating force, loading rate, joint angle, and external joint moments of the two conditions were recorded and compared. No significant difference was noted in the walking speed. However, the first peak of vertical GRF, braking force, and loading rate during loading response were significantly reduced during impact reduction walking, and external joint moments in the hip, knee, and ankle joints were reduced. In contrast, the second peak of vertical GRF, hip extension angle, and external ankle dorsiflexion moment were significantly increased during terminal stance. Our data imply that the ankle joint function during the terminal stance is important in reducing the dynamic joint load in the contralateral leg during the loading response.

Radiographic and clinical factors associated with one-leg standing and gait in patients with mild-to-moderate secondary hip osteoarthritis.

A decline in physical function associated with secondary hip osteoarthritis (OA) may be caused by both radiographic and clinical factors; however, the underlying mechanism remains unclear. The purpose of this study was to determine how joint degeneration, hip morphology, pain, hip range of motion (ROM), and hip muscle strength relate to one-leg standing (OLS) and gait in patients with mild-to-moderate secondary hip osteoarthritis. Fifty-five female patients (ages 22-65 years) with mild-to-moderate hip OA secondary to hip dysplasia were consecutively enrolled. Balance during OLS and three-dimensional hip angle changes while maintaining the OLS and at foot-off of the raised leg were measured. Gait speed and peak three-dimensional hip joint angles during gait were also measured. The associations between dependent variables (balance, gait speed, and hip kinematic changes) and independent variables (age, body mass index, pain, joint degeneration, hip morphologic abnormality, passive hip ROM, and hip muscle strength) were determined. While lower hip muscle strength was associated with hip kinematic changes such as flexion and internal rotation while maintaining OLS, decreased acetabular head index (AHI) and increased pain were associated with hip extension and abduction at foot-off in OLS. Decreased passive hip ROM was associated with decreased peak hip angles (extension, adduction, and external and internal rotation) during gait, although increased pain and decreased hip extension muscle strength were associated with slower gait speed. In this study of patients with secondary hip OA, AHI, pain, and hip impairments were associated with OLS and gait independently from age and radiographic degeneration.

Associations of radiographic degeneration and pain with daily cumulative hip loading in patients with secondary hip osteoarthritis.

The purpose of this study was to investigate the associations of radiographic and clinical variables of hip osteoarthritis (OA) with alterations in gait and joint loading in patients with secondary hip OA. Fifty females with secondary hip OA were participated. The minimum joint space width (mJSW) of the hip as a degenerative sign and Sharp and center edge (CE) angles as morphological variables were measured radiographically. Hip joint pain was assessed using a visual analog scale. As gait variables, walking speed, range of hip motion, hip moment peak, and hip moment impulse were calculated. Daily cumulative hip loading was calculated as the hip moment impulse multiplied by the mean number of steps per day. After bivariate correlation analyses between dependent (mJSW and pain) and independent variables (age, body mass index, sharp/CE angles, steps per day, and gait variables), separate forward-backward stepwise multiple regression analyses were performed for each dependent variable. Daily cumulative hip loading in the sagittal plane (ß = 0.30, p = 0.021) and age (ß = -0.36, p = 0.007) were significantly associated with the mJSW. Walking speed (ß = -0.36, p = 0.008) and age (ß = 0.29, p = 0.031) were significantly associated with hip joint pain. Decrease in daily cumulative hip loading in the sagittal plane was associated with mJSW independently of age. Although the causal relationship was not clear, patients with hip OA reduced total exposure to hip joint loading adaptively rather than lowering the hip moment peak concerning worsening of hip degeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1977-1983, 2016.

Relationships between performance and kinematic/kinetic variables of stair descent in patients with medial knee osteoarthritis: An evaluation of dynamic stability using an extrapolated center of mass.

BACKGROUND: The ability to descend stairs independently is impaired from a relatively early stage in patients with knee osteoarthritis. The purpose of this study was to evaluate the performance in patients with knee osteoarthritis when stepping down a step by evaluating the dynamic stability using the extrapolated center of mass. METHODS: Twenty-three individuals with medial knee osteoarthritis were evaluated during step descent without any assistance. Kinematic/kinetic data were collected using a three-dimensional motion analysis system and force platforms. The extrapolated center of mass and its deviation from the anterior boundary on the base of support (margin of stability) were calculated at the initiation of descent. Joint angles and internal joint moments were collected at the stance limb. The relationship between patients' dynamic stability control, which was measured by the timed up and go test, and the length of margin of stability was analyzed. Relationships between the length of the margin of stability and each kinematic/kinetic variable were also evaluated. FINDINGS: The margin of stability positively correlated with the time taken for a timed up and go test. A positive correlation was additionally observed between the ankle dorsiflexion angle and the margin of stability. It was also found that a higher ratio of ankle plantar flexion moment by support moment was associated with a larger margin of stability. INTERPRETATION: Patients with knee osteoarthritis who had high ability in dynamic stability control were observed to move their center of mass anteriorly at the initiation of stepping down. It was also suggested that these patients could dorsiflex their ankle joint and generate sufficient ankle plantar flexor torque.

Immediate effect of Masai Barefoot Technology shoes on knee joint moments in women with knee osteoarthritis.

Footwear modification can beneficially alter knee loading in patients with knee osteoarthritis. This study evaluated the effect of Masai Barefoot Technology shoes on reductions in external knee moments in patients with knee osteoarthritis. Three-dimensional motion analysis was used to examine the effect of Masai Barefoot Technology versus control shoes on the knee adduction and flexion moments in 17 women (mean age, 63.6 years) with radiographically confirmed knee osteoarthritis. The lateral and anterior trunk lean values, knee flexion and adduction angles, and ground reaction force were also evaluated. The influence of the original walking pattern on the changes in knee moments with Masai Barefoot Technology shoes was evaluated. The knee flexion moment in early stance was significantly reduced while walking with the Masai Barefoot Technology shoes (0.25±0.14Nm/kgm) as compared with walking with control shoes (0.30±0.19 Nm/kgm); whereas the knee adduction moment showed no changes. Masai Barefoot Technology shoes did not increase compensatory lateral and anterior trunk lean. The degree of knee flexion moment in the original walking pattern with control shoes was correlated directly with its reduction when wearing Masai Barefoot Technology shoes by multiple linear regression analysis (adjusted R2=0.44, P<0.01). Masai Barefoot Technology shoes reduced the knee flexion moment during walking without increasing the compensatory trunk lean and may therefore reduce external knee loading in women with knee osteoarthritis.

Direct transformation into silver nanoparticles via thermal decomposition of oxalate-bridging silver oleylamine complexes.

Silver(I) oxalate, Ag2(C2O4), reacts with two equivalents of oleylamine (Ag:oleylamine = 1:1 mole/mole) to form an oxalate-bridged silver-oleylamine complex, [(oleylamine)Ag(micro-C2O4)Ag(oleylamine)]. The precursor complex is thermally decomposed at approximately 150 degrees C with CO2 evolution to produce Ag nanoparticles with approximately 11 nm dimension. The Ag nanoparticles contain approximately 12 wt% of oleylamines as the surface stabilizer. In the synthetic mechanism, the oxalate ligand acts as a two-electron reducing agent. The precursor complex is directly transformed into oleylamine-stabilized Ag nanoparticles in high yields of more than 80% without any additional synthetic organic solvents and reducing agents.

Mechanisms of calcium elevation in the micromeres of sea urchin embryos.

The micromeres, the first cells to be specified in sea urchin embryos, are generated by unequal cleavage at the fourth cell division. The micromeres differentiate autonomously to form spicules and dispatch signals to induce endomesoderm in the neighbouring macromeres cells in the embryo. Using a calcium indicator Fura-2/AM and a mixture of dextran conjugated Oregon green-BAPTA 488 and Rhodamine red, the intracellular calcium ion concentration ([Ca2+]i) was studied in embryos at the 16-cell stage. [Ca2+]i was characteristically elevated in the micromeres during furrowing at the 4th cleavage. Subsequently, Ca2+ oscillated for about 10 min in the micromeres, resulting in episodic high levels of [Ca2+]i. High [Ca2+]i regions were associated with regional localizations of the endoplasmic reticulum (ER), though not with ER accumulated at the vegetal pole of the micromeres during the 4th division. Pharmacological studies, using a blocker of IP3-mediated Ca2+ release (Xestospongin), a store-operated Ca2+ entry inhibitor (2 aminoethoxydiphenyl borate (2-APB)) and an inhibitor of stretch-dependent ion channels (gadolinium), suggest that the high [Ca2+]i and oscillations in the micromeres are triggered by calcium influx caused by the activation of stretch-dependent calcium channels, followed by the release of calcium ions from the endoplasmic reticulum. On the basis of these new findings, a possible mechanism for autonomous formation of the micromeres is discussed.

An epidemiologic survey of methicillin-resistant Staphylococcus aureus by combined use of mec-HVR genotyping and toxin genotyping in a university hospital in Japan.

OBJECTIVE: To evaluate the usefulness of an assay using two polymerase chain reaction-based genotyping methods in the practical surveillance of methicillin-resistant Staphylococcus aureus (MRSA). METHODS: Nosocomial infection and colonization were surveyed monthly in a university hospital in Japan for 20 months. Genotyping with mec-HVR is based on the size of the mec-associated hypervariable region amplified by polymerase chain reaction. Toxin genotyping uses a multiplex polymerase chain reaction method to amplify eight staphylococcal toxin genes. RESULTS: Eight hundred nine MRSA isolates were classified into 49 genotypes. We observed differing prevalences of genotypes for different hospital wards, and could rapidly demonstrate the similarity of genotype for outbreak isolates. The incidence of genotype D: SEC/TSST1 was significantly higher in isolates causing nosocomial infections (49.5%; 48 of 97) than in nasal isolates (31.4%; 54 of 172) (P = .004), suggesting that this genotype may represent the nosocomial strains. CONCLUSION: The combined use of these two genotyping methods resulted in improved discriminatory ability and should be further investigated.