Kiyokazu Akasaka

EMG-angle relationship of the hamstring muscles during maximum knee flexion

The aim of the present study was to investigate the EMG-joint angle relationship during voluntary contraction with maximum effort and the differences in activity among three hamstring muscles during knee flexion. Ten healthy subjects performed maximum voluntary isometric and isokinetic knee flexion. The isometric tests were performed for 5 s at knee angles of 60 and 90 degrees. The isokinetic test, which consisted of knee flexion from 0 to 120 degrees in the prone position, was performed at an angular velocity of 30 degrees /s (0.523 rad/s). The knee flexion torque was measured using a KIN-COM isokinetic dynamometer. The individual EMG activity of the hamstrings, i.e. the semitendinosus, semimembranosus, long head of the biceps femoris and short head of the biceps femoris muscles, was detected using a bipolar fine wire electrode. With isometric testing, the knee flexion torque at 60 degrees knee flexion was greater than that at 90 degrees. The mean peak isokinetic torque occurred from 15 to 30 degrees knee flexion angle and then the torque decreased as the knee angle increased (p<0.01). The EMG activity of the hamstring muscles varied with the change in knee flexion angle except for the short head of the biceps femoris muscle under isometric condition. With isometric contraction, the integrated EMGs of the semitendinosus and semimembranosus muscles at a knee flexion angle of 60 degrees were significantly lower than that at 90 degrees. During maximum isokinetic contraction, the integrated EMGs of the semitendinosus, semimembranosus and short head of the biceps femoris muscles increased significantly as the knee angle increased from 0 to 105 degrees of knee flexion (p<0.05). On the other hand, the integrated EMG of the long head of the biceps femoris muscle at a knee angle of 60 degrees was significantly greater than that at 90 degrees knee flexion with isometric testing (p<0.01). During maximum isokinetic contraction, the integrated EMG was the greatest at a knee angle between 15 and 30 degrees, and then significantly decreased as the knee angle increased from 30 to 120 degrees (p<0.01). These results demonstrate that the EMG activity of hamstring muscles during maximum isometric and isokinetic knee flexion varies with change in muscle length or joint angle, and that the activity of the long head of the biceps femoris muscle differs considerably from the other three heads of hamstrings.

Intertester Reliability and Diagnostic Validity of the Cervical Flexion-Rotation Test

OBJECTIVE This article evaluates reliability and diagnostic validity of the cervical flexion-rotation test (FRT) to discriminate subjects with headache because of C1/2 dysfunction. In addition, this study evaluates agreement between experienced and inexperienced examiners. METHODS These were 2 single blind comparative measurement study designs. In study 1, 2 experienced blinded examiners evaluated the FRT in 10 asymptomatic controls, 20 subjects with cervicogenic headache (CeH) where C1/2 was the primary dysfunctional level, and 10 subjects with CeH but without C1/2 as the primary dysfunctional level. In study 2, 2 inexperienced and 1 experienced blinded examiners evaluated the FRT in 12 subjects with CeH and 12 asymptomatic controls. Examiners were required to state whether the FRT was positive and also to determine range of rotation using a goniometer. An analysis of variance with planned orthogonal comparison, single measure intraclass correlation coefficient (2,1), and Bland-Altman plot were used to analyze FRT range of rotation between the examiners. Sensitivity, specificity, and examiner agreement for test interpretation were analyzed using cross tabulation and kappa. RESULTS In study 1, sensitivity and specificity of the FRT was 90% and 88% with 92% agreement for experienced examiners (P < .001). Overall diagnostic accuracy was 89% (P < .001) and kappa = 0.85. In study 2, for inexperienced examiners, FRT mobility was significantly greater than for experienced examiners, but sensitivity, specificity, agreement, and kappa values were all within clinically acceptable levels. CONCLUSIONS The FRT can be used accurately and reliably by inexperienced examiners and may be a useful aid in CeH evaluation.

A clinical trial of a prototype of wireless surface fes rehabilitation system in foot drop correction

The purpose of this study is to develop a wireless FES rehabilitation system to assist effective improvement of the lower limbs. In this report, a prototype system combined with foot drop correction and gait evaluation using wireless surface electrical stimulator and the wireless inertial sensors was developed and tested with a right hemiplegic subject. For gait evaluation, lower limb joint angles and segment angles were estimated by the Kalman filter from the data measured with wireless inertial sensors. Electrical stimulation was applied to the common peroneal nerve or the tibialis anterior muscle by detecting stimulus timing automatically from the data of wireless inertial sensor attached on the shank of the hemiplegic side. The maximum joint angle of ankle dorsiflexion of the paralyzed side at the swing phase was increased approximately to the value of the healthy side by applying the electrical stimulation. The developed system was performed well in foot drop correction and the measured data of the inertial sensors showed the characteristics and difference of paralyzed side with and without electrical stimulation using the segment angles and joint angles.

Fatigue Alters Landing Shock Attenuation During a Single-Leg Vertical Drop Jump

Background: Landings in fatigue conditions are considered to be one of the factors that cause noncontact anterior cruciate ligament (ACL) injury. Additionally, it is known that fatigue alters lower extremity landing strategies and decreases the ability to attenuate shock during landing. Purpose: To determine characteristics of knee kinematics and shock attenuation during the landing phase of a single-leg vertical drop jump in a fatigued condition. The hypothesis was that knee kinematics during the landing phase of a single-leg vertical drop jump would demonstrate a significant difference between before and after fatigue. Study Design: Controlled laboratory study. Methods: Thirty-four college females participated in this experiment. They were randomly assigned to either the fatigue (n = 17) or control group (n = 17). The fatigue group performed the single-leg vertical drop jump before and after the fatigue protocol, which was performed on a bike ergometer. Knee kinematics data were obtained from the 3-dimensional motion analysis system. The ratio of each variable (%) was calculated, comparing the pre- to postfatigue protocol. Unpaired t tests were used to compare changes in kinematic variables between the fatigue-induced group and control group. Results: Peak knee flexion angular velocity increased significantly in the fatigue group (106.1% ± 8.0%) in comparison with the control group (100.7% ± 6.6%) (P < .05). However, peak knee flexion angle and acceleration had no differences between each group. Peak knee adduction/abduction angle, velocity, and acceleration also had no differences between each group. Conclusion: Fatigue decreased the ability to attenuate shock by increasing angular velocity in the direction of knee flexion during single-leg drop jump landing. These findings indicate the need to evaluate the ability to attenuate shock by measuring knee flexion angular velocity when fatigue is considered. Clinical Relevance: Measuring knee angular velocity during landings might be an important evaluation parameter in the consideration of the knee injury prevention.

Dynamic knee valgus alignment influences impact attenuation in the lower extremity during the deceleration phase of a single-leg landing

Dynamic knee valgus during landings is associated with an increased risk of non-contact anterior cruciate ligament (ACL) injury. In addition, the impact on the body during landings must be attenuated in the lower extremity joints. The purpose of this study was to investigate landing biomechanics during landing with dynamic knee valgus by measuring the vertical ground reaction force (vGRF) and angular impulses in the lower extremity during a single-leg landing. The study included 34 female college students, who performed the single-leg drop vertical jump. Lower extremity kinetic and kinematic data were obtained from a 3D motion analysis system. Participants were divided into valgus (N = 19) and varus (N = 15) groups according to the knee angular displacement during landings. The vGRF and angular impulses of the hip, knee, and ankle were calculated by integrating the vGRF-time curve and each joint’s moment-time curve. vGRF impulses did not differ between two groups. Hip angular impulse in the valgus group was significantly smaller than that in the varus group (0.019 ± 0.033 vs. 0.067 ± 0.029 Nms/kgm, p<0.01), whereas knee angular impulse was significantly greater (0.093 ± 0.032 vs. 0.045 ± 0.040 Nms/kgm, p<0.01). There was no difference in ankle angular impulse between the groups. Our results indicate that dynamic knee valgus increases the impact the knee joint needs to attenuate during landing; conversely, the knee varus participants were able to absorb more of the landing impact with the hip joint.

The Effects of Elbow Bracing on Medial Elbow Joint Space Gapping Associated With Repetitive Throwing in High School Baseball Players

Background: Throwing athletes risk medial elbow injury from extreme valgus stress generated across the medial elbow during throwing. Braces have been developed to protect the elbow joint; however, no previous study has investigated the effects of elbow bracing on medial elbow joint space gapping associated with repetitive throwing. Hypothesis/Purpose: The purpose of this study was to investigate the effects of elbow bracing on medial elbow joint space gapping during repetitive throwing. Our hypothesis was that an elbow brace may reduce mechanical stress on the elbow by reducing medial elbow joint space gapping. Study Design: Controlled laboratory study. Methods: Twenty-five high school baseball players participated in this study. Each subject pitched 100 times under 2 conditions: control (without elbow brace) and elbow brace. The ulnohumeral joint space was measured ultrasonically before pitching and after every block of 20 pitches. Measurement of the ulnohumeral joint space was carried out using ultrasound with the forearm hanging by the side. Two-way repeated-measures analysis of variance and post hoc tests were used to compare ulnohumeral joint space with repeated pitching and between the elbow brace and control conditions. Results: In the control condition, ulnohumeral joint space after 60 pitches was significantly greater than that before pitching (P < .01). In contrast, in the elbow brace condition, ulnohumeral joint space was not significantly different after repeated pitching. When comparing these 2 conditions, ulnohumeral joint space in the control condition was significantly greater than that in the elbow brace condition after 60 pitches (P < .01). Conclusion: An elbow brace has the effect of preventing medial elbow joint space gapping with repeated throwing when determined ultrasonically by measuring the ulnohumeral joint space under gravity load. Clinical Relevance: An elbow brace worn during baseball pitching practice may help reduce mechanical stress on the elbow by reducing medial elbow joint space gapping.

Deep abdominal muscle thickness measured under sitting conditions during different stability tasks.

[Purpose] This study was conducted to investigate ultrasonically determined changes in the thickness of the transversus abdominis and internal oblique muscles during different sitting conditions. [Subjects and Methods] Twenty healthy men volunteered to participate in this study. Four different sitting conditions including (A) sitting, (B) sitting with left hip flexion, (C) sitting with an abdominal hollowing maneuver (AHM), and (D) sitting with an AHM and left hip flexion, were used. Subjective exercise difficulty was evaluated. [Results] Transversus abdominis and internal oblique muscle thicknesses significantly differed between conditions, with significantly greater thickness between positions from (A) to (D). Stability of the surface when sitting had no effect on the muscle thickness of the transversus abdominis. By contrast, sitting on an unstable surface caused an increase in muscle thickness of the internal oblique in each condition. The subjects reported progressively increasing difficulty in performing each exercise in a stable position from (A) to (D), while the difficulty in an unstable position was significantly different between (A) and (B), and between (C) and (D). [Conclusion] Our findings suggest that task (B) on a stable surface should be chosen for maximal activation of transversus abdominis without inducing overactivation of the internal oblique muscle.

Immediate effect of application of the pressure technique to the psoas major on lumbar lordosis

[Purpose] To demonstrate immediate alteration in lumbar lordosis and the lumbar angle in each segment after the application of the mechanical pressure technique to the psoas major muscle (PM). [Participants and Methods] In all, 34 participants were assigned to either the PM pressure technique group (n=17) or control group (n=17). Three dimensional (3D) coordinates of the 12th thoracic spinous process and lumbar spinous processes were measured with a 3D digitizer in the prone position with 15° bilateral hip extension to compare the changes in lumbar lordosis and the lumbar extension angle in each segment in both the PM pressure technique group and control group. [Results] Mann-Whitney’s U test revealed no significant differences in lumbar lordosis in either group. However, the lumbar extension angle at L4 decreased significantly after the PM pressure technique compared with that before the pressure technique. Additionally, the lumbar extension angle at L4 also decreased significantly after the PM pressure technique compared with the control group. Conversely, lumbar extension angle at L1 increased significantly after the PM pressure technique compared with that before. There was no significant difference in the lumbar extension angle at L2, L3 and L5 after the PM pressure technique. [Conclusion] This study suggests that the PM pressure technique possibly attenuates PM stiffness while reducing lumbar extension in each segment.

Three-Dimensional Motion Analysis of the 2nd Cervical Spinous Process at End Range Cervical Rotation in Different Scapular Positions Using 3D Digitizer

Objective The study used a 3D digitizer to determine three-dimensional motion analysis of the 2nd cervical (C2) spinous process at end range cervical rotation with the scapula in different positions. Methods 30 healthy adults participated in this study. Different scapula positions were adopted bilaterally and positioned passively at normal resting, depression, adduction, and abduction. Under each scapula position, bilateral end range cervical rotation and displacement of the C2 spinous process were analyzed by a 3D digitizer. Results Displacement of the C2 spinous process relative to the occiput was significantly correlated with range of cervical rotation under all scapular positions (p<0.05). However, there were no significant differences between end range cervical rotation and displacement of the C2 spinous process relative to the occiput in any scapular position. Conclusion These results suggest that measurement of upper cervical mobility using the 3D digitizer is a reliable method that holds promise in the evaluation of people with cervical spine disorders.

The effect of repetitive baseball pitching on medial elbow joint space gapping associated with 2 elbow valgus stressors in high school baseball players

BACKGROUND To prevent elbow injury in baseball players, various methods have been used to measure medial elbow joint stability with valgus stress. However, no studies have investigated higher levels of elbow valgus stress. This study investigated medial elbow joint space gapping measured ultrasonically resulting from a 30 N valgus stress vs. gravitational valgus stress after a repetitive throwing task. METHODS The study included 25 high school baseball players. Each subject pitched 100 times. The ulnohumeral joint space was measured ultrasonographically, before pitching and after each successive block of 20 pitches, with gravity stress or 30 N valgus stress. Two-way repeated measures analysis of variance and Pearson correlation coefficient analysis were used. RESULTS The 30 N valgus stress produced significantly greater ulnohumeral joint space gapping than gravity stress before pitching and at each successive 20-pitch block (P < .01). For the 2 stress methods, ulnohumeral joint space gapping increased significantly from baseline after 60 pitches (P < .01). Strong significant correlations were found between the 2 methods for measurement of medial elbow joint space gapping (r = 0.727-0.859, P < .01). CONCLUSIONS Gravity stress and 30 N valgus stress may produce different effects with respect to medial elbow joint space gapping before pitching; however, 30 N valgus stress appears to induce greater mechanical stress, which may be preferable when assessing joint instability but also has the potential to be more aggressive. The present results may indicate that constraining factors to medial elbow joint valgus stress matched typical viscoelastic properties of cyclic creep.