The test-induced warm-up effect on hamstring flexibility tests.

Background: Although the effect of active warm-up (WU) on acute flexibility enhancement is well documented, the test-induced WU effect in muscle length test has not been widely studied. Objective: This study aimed to verify the test-induced WU effect on hamstring flexibility tests. Methods: The active knee extension (AKE) was performed using the right leg, whereas the straight leg raise (SLR) was performed using the left leg. Ten trials of AKE or SLR were performed: two as the pre-intervention trials (Pre); six as the WU intervention; and another two trials as the post-intervention (Post). During WU, subjects in the WO-Hold group performed six trials of the AKE or SLR without hold, and those in the W-Hold group performed six trials of the AKE or SLR with a 5 s hold. Results: A significant difference was noted between Pre-AKE and Post-AKE, and between Pre-SLR and Post-SLR, respectively, in both the groups. The effect of WU is clear when performing consecutive AKE or SLR without any additional hold. Conclusion: Practitioners should be cautious in interpreting the testing result to avoid overestimation of the treatment effect since the test itself may induce substantial WU effect to the target tissues.

Joint position sense error in the hip and knee without reference to the joint angle.

BACKGROUND: Joint position reproduction measures the angle acuity of reference angle reproduction using an indicator angle. However, reference angles are often not available. OBJECTIVE: This study aimed to examine joint position sense at three different targeted joint angles, which were estimated from the maximum range of motion (maxROM) without a reference angle at each targeted joint angle. METHODS: The maxROM was measured in straight leg raise (SLR) and active knee extension (AKE) positions. In both positions, a targeted joint angle at 75% of the maxROM was assessed first, followed by that at 50% and 25% of the maxROM. A one-sample t-test was used to analyze differences between the targeted and reproduced angles in both positions. RESULTS: All reproduced angles significantly differed from the targeted angle in both SLR and AKE positions except for the reproduced angle measured at 75% maxROM. Overall, position errors in the AKE position were higher than those in the SLR position. CONCLUSIONS: Estimating the angle based on the maxROM without a matched reference angle may lead to significant discrepancies in comparison with the targeted joint angle. In clinical settings, if accurate reproduction of motions is required to improve proprioception, providing a reference angle might be helpful.

Effect of PNF stretching performed in the AKE position on hip, knee, and ankle flexibility.

BACKGROUND: To measure hamstring flexibility, the active knee extension (AKE) test is preferred over the straight leg raise (SLR) test as it can be used to measure hamstring flexibility more selectively. However, hamstring stretching is primarily conducted in the SLR position (maximal hip flexion in the supine position) as it allows for maximal hip flexion in the supine position. OBJECTIVE: This study evaluates the effects of proprioceptive neuromuscular facilitation (PNF) stretching in the AKE position (maximal knee extension with 90∘ flexion of the hip in the supine position) on hip, knee, and ankle flexibility. METHODS: SLR, AKE, and active dorsiflexion (ADF) tests were used to determine the range of motion (ROM) before (pre-ROM) and after (post-ROM) stretching. PNF stretching consisted of maximal isometric knee flexion at the end range with external resistance to prevent knee flexion. One set of PNF stretches (five trials of six seconds each) was conducted. RESULTS: The post-ROMs of hip, knee, and ankle measured via the SLR, AKE, and ADF tests, respectively, were significantly higher than the pre-ROMs. CONCLUSIONS: The improvement in knee flexibility was greater than the improvement in hip and ankle flexibility. The AKE position is recommended in clinical settings during PNF stretching for individuals with hamstring tightness. Furthermore, PNF stretching in the AKE position increases the ADF ROM.

Comparison of muscle activity of hamstrings as knee flexors and hip extensors and effect of tibial and hip rotation on the contribution of hamstrings.

BACKGROUND: Limited studies have compared the muscle activity of the medial and lateral hamstrings as knee flexors with tibial internal and external rotation and hip extensors with hip internal and external rotation. In particular, hamstring activity during hip extension with hip rotation has rarely been investigated. OBJECTIVE: This study aimed to compare the muscle activity of the medial and lateral hamstrings as knee flexors and hip extensors and to compare the activity of these muscles according to tibial rotation during isometric knee flexion and hip rotation during isometric hip extension. METHODS: A total of 23 healthy adults participated in the study. The electromyographic (EMG) activity of the hamstrings was measured during maximal isometric knee flexion and maximal isometric hip extension. In addition, tibial rotation was applied actively during maximal isometric knee flexion, whereas hip rotation was applied actively during maximal isometric hip extension. RESULTS: EMG activity during maximal isometric knee flexion with tibial internal and external rotation was significantly higher than that during maximal isometric hip extension with hip internal and external rotation, respectively. For EMG activity according to tibial and hip rotation, there was no significant difference between tibial internal and external rotation during maximal isometric knee flexion, whereas there was a significant difference between hip internal and external rotation during maximal isometric hip extension. CONCLUSION: Hamstring activity was higher for knee flexors than for hip extensors. However, hip rotation during maximal isometric hip extension is an effective intervention for selective muscle activation of the medial and lateral hamstrings.

Concurrent and Angle-Trajectory Validity and Intra-Trial Reliability of a Novel Multi-View Image-Based Motion Analysis System.

Sports-related injuries are the most common in the lower extremities among physical regions. To evaluate impaired functional performance in sports training facilities and sports, a marker-less motion analysis system that can measure joint kinematics in bright indoor and outdoor environments is required. The aim of this study was to establish the concurrent and angle-trajectory validity and intra-trial reliability of a novel multi-view image-based motion analysis system with marker-less pose estimation during lower extremity tasks in healthy young men. Ten healthy young men participated voluntarily in this study. The hip and knee joint angles were collected using a multi-view image-based motion analysis system (marker-less) and a Vicon motion capture system (with markers) during the lower extremity tasks. Intraclass correlation coefficient (ICC) analyses were used to identify the concurrent and angle-trajectory validity and intra-trial reliability of the multi-view image-based motion analysis system. In the concurrent validity, the correlation analysis revealed that the ICC3, k values on the hip and knee flexions during knee bending in sitting, standing, and squat movements were from 0.747 to 0.936 between the two systems. In particular, the angle-trajectory validity was very high (ICC3, 1 = 0.859-0.998), indicating a high agreement between the two systems. The intra-trial reliability of each system was excellent (ICC3, 1 = 0.773-0.974), reflecting high reproducibility. We suggest that this novel marker-less motion analysis system is highly accurate and reliable for measuring joint kinematics of the lower extremities during the rehabilitation process and monitoring sports performance of athletes in training facilities.

Acute effect of diagonal stretching using the posterior oblique sling system on contralateral ankle dorsiflexion.

BACKGROUND: A significant increase in the dorsiflexion range of motion (DFROM) after calf muscle stretching has been widely studied. However, it has been shown that the upper body is connected to the ankle joint by passive connective tissues. OBJECTIVE: The purpose of this study was to examine the effect of upper-back stretching on the mobility of the contralateral ankle. METHODS: In the supine position, DFROM in the contralateral leg was measured. In the sitting position with and without trunk rotation, DFROM was measured in both legs. In the sitting position with trunk rotation, dorsiflexion was measured only in the contralateral leg. Static diagonal stretching combining trunk rotation with slight trunk flexion was performed in the sitting position with a neutral pelvis. RESULTS: After stretching, DFROM in contralateral and ipsilateral legs were measured in the sitting position with a neutral pelvis. In the contralateral leg, significant differences in ΔDFROM were observed between the sitting position with trunk rotation and the supine position and between the sitting position with trunk rotation and the sitting position after stretching. CONCLUSION: In clinical settings, diagonal stretching of the unilateral posterior trunk causes a significant increase in the DFROM of the contralateral lower limb.

Effects of hip rotation on the electromyographic activity of the medial and lateral hamstrings and muscle force.

BACKGROUND: In clinical practice, knee flexion at the prone position for manual muscle testing of hamstrings and hip extension at the supine position for stretching of hamstring muscles are typically proposed. OBJECTIVE: Although different positions have been proposed for different purposes in hamstrings, the understanding of the changing the functional role of hamstrings with position changes is poorly understood. METHODS: The electromyographic (EMG) activity and hip extension force were compared among different postures; hip neutral, internal, and external rotation. EMG and force were measured in prone position during knee flexion and those were additionally measured in supine position during hip extension. In supine position, additional measurements were made in hip neutral, internal and external rotation. RESULTS: Hamstrings showed high EMG activity during knee flexion. Knee flexion force in prone position was significantly decreased at hip extension force in supine position. In supine position, EMG activity was significantly higher in semitendinosus (ST) than biceps femoris (BF) during internal rotation. CONCLUSIONS: It should be noted that bi-articular muscles may have different functional dependencies on the corresponding muscles for each joint. In addition, because the altered alignment of the hamstring muscles that was affected by hip rotation had a significant effect on muscle activity, and hip rotation may be helpful for selective training of medial or lateral hamstrings.

Effects of proprioceptive neuromuscular facilitation stretching at low-intensities with standing toe touch on developing and maintaining hamstring flexibility.

BACKGROUND: Proprioceptive neuromuscular facilitation (PNF) stretching at low intensities has been rarely investigated. Previous studies have shown that hamstring flexibility after stretching is only temporary. OBJECTIVE: The aim of this study was to assess the effect of low intensities (40% and 10% of maximum voluntary isometric contraction, MVIC) of PNF stretching on hamstring muscles and to assess the effect of standing toe touch on the duration of hamstring flexibility. METHODS: This was a single-blind randomized controlled trial. Sixty-four healthy adults (age, 22.67 ± 1.73 years) were selected and divided into four groups: 40% intensity PNF stretching (P40), 10% intensity PNF stretching (P10), 40% intensity PNF stretching with toe touch (P40 with TT), and 10% intensity PNF stretching with toe touch (P10 with TT). Hamstring flexibility was measured using the active knee extension test (pre-stretching, post-stretching, and 3, 6, 9, 12, and 15 min after PNF stretching). RESULTS: In the P40, P40 with TT, and P10 with TT groups, significant changes were observed at all time points after stretching (p < 0.05). In the P10 group, significant changes were only observed immediately post stretching (p = 0.006) and at 3 min (p = 0.029) after stretching. In terms of maintaining the duration of flexibility, the P40 with TT and P10 with TT groups were superior to the P40 and P10 groups. CONCLUSION: PNF stretching at low intensity, approaching 40% of MVIC, led to more flexibility than 10% MVIC. Additionally, standing toe touch after PNF stretching is recommended to develop and maintain hamstring flexibility.

Effects of upper-extremity movements on electromyographic activities of selected trunk muscles during leaning forward.

BACKGROUND: Leaning forward has been accepted as a foundational approach to facilitate trunk-stabilizing muscles in the abdominal and lumbopelvic regions for patients with back pain during rehabilitation. However, how trunk muscles are activated and recruited during leaning forward performed under dynamic upper-extremity motion conditions is not completely understood. OBJECTIVE: To determine whether activation of selected trunk muscles changes depending on shoulder movements during leaning forward exercise in healthy young adults. METHODS: Twenty-four healthy adults (6 men and 18 women) participated in this study. The participants performed 3 types of leaning forward exercises: leaning forward alone (leaning forward 1), leaning forward with horizontal shoulder abduction (leaning forward 2), and leaning forward with shoulder flexion (leaning forward 3). Surface electromyography (EMG) was used to record activation of the erector spinae (ES), multifidus (MF), rectus abdominis (RA), and internal oblique (IO) on the dominant side. RESULTS: There was a significant main effect of exercise type on the activation of the IO, RA, and MF muscles. Activation of the IO and MF during leaning forward 1 was significantly decreased compared to activation in leaning forward 2 and 3; the activation of IO and RA showed the greatest increase during leaning forward 3. Furthermore, the IO/RA ratio was significantly increased during leaning forward 2 and 3 in comparison to leaning forward 1; the MF/ES ratio was also significantly increased during leaning forward 3, compared with leaning forward 1. CONCLUSION: The integration of shoulder movements during leaning forward exercises could be effective in the facilitation of EMG activity of IO and MF muscles, especially with shoulder flexion.

The efficacy of virtual reality assisted versus traditional rehabilitation intervention on individuals with functional ankle instability: a pilot randomized controlled trial.

PURPOSE: Virtual reality (VR) training, a virtual environment commonly generated by computer systems, may enhance the therapeutic efficacy of functional rehabilitation programmes. The aim of this study was to investigate the efficacy of a VR assisted intervention (VRAI) versus traditional rehabilitation intervention (TRI) on functional ankle instability (FAI). METHODS: A single-blind randomized controlled study was conducted with 10 subjects for each group. The VRAI was conducted with the Nintendo Wii Fit Plus, whilst the TRI was conducted with a series of exercises with theraband. The muscle strength change of the two groups and the difference between pre and post interventions for each group were compared. RESULTS: The VRAI group had less improvement in the muscle strength of all ankle motions than did the TRI group (p > .05). The VRAI group had a greater improvement in muscle strength of plantar flexion than other motions, whilst the TRI group had an improvement in muscle strength of all ankle motions (p < .05). CONCLUSIONS: The effects of VR training for the condition of FAI were not comparable to conventional training. However, VR training may be added to the conventional training programme as an optional for the condition of FAI. Implications for Rehabilitation Functional ankle instability (FAI) is subjective feelings of ankle instability resulting from proprioceptive and neuromuscular deficits in which individuals may experience "giving way" condition of the ankle. Therapeutic applications of virtual reality (VR) may be comparable to traditional rehabilitation interventions (TRI) in the rehabilitation of individuals with FAI. However, there is no definitive evidence for the issue. Integrating low-cost VR into functional rehabilitation programme can provide insight into an issue of whether it can be replaced with traditional therapeutic approaches. Although, the efficacy of VR application on strengthening muscles is unable to compare to traditional strengthening programmes, it may be considered an optional treatment based on the proprioceptive improvements.

Easy method for measuring stretching intensities in real clinical settings and effects of different stretching intensities on flexibility.

BACKGROUND: Flexibility changes according to stretching intensity have been rarely investigated. I aimed to assess the effect of different stretching intensities on hamstring flexibility by measuring them in a setting similar to real clinical settings. METHODS: Stretching intensities were quantified using an easy method, and participants were grouped according to intensity: 100% (P100), 70% (P70), 40% (P40), and 10% (P10) of maximum voluntary isometric contraction. Proprioceptive neuromuscular facilitation stretching intensities were measured using a sling system and tension dynamometer. Hamstring flexibility was measured (before; immediately after; and 3, 6, 9, 12, and 15 min after stretching) using the active knee extension test. Flexibility was compared between subgroups, and longitudinal changes in flexibility were additionally observed in each group. RESULTS: At identical time points, no significant difference in hamstring flexibility was found between the high-intensity (P100) and moderate-intensity (P70, P40) groups. A significant difference was found between P100 and P10 immediately after and 12 and 15 min after stretching. Increased flexibility was maintained until the end in P100 and P70 but not P40 and P10. CONCLUSIONS: High-intensity and moderate-intensity stretching increases flexibility compared with low-intensity stretching. Furthermore, high-intensity stretching was superior to moderate-intensity stretching in terms of maintaining flexibility over time.

Optimal intensity of PNF stretching: maintaining the efficacy of stretching while ensuring its safety.

[Purpose] To investigate changes in hamstring flexibility in relation to intensity of proprioceptive neuromuscular facilitation stretching and changes in pain over time, and examine the correlations between pain level and target intensity or flexibility gain. [Participants and Methods] Sixty-one healthy adults were randomly divided into 4 groups (100% [P100], 70% [P70], 40% [P40], and 10% [P10] of maximum voluntary isometric contraction) according to intensity of hold-relax stretching. Hamstring flexibility was measured with the active knee extension test, and pain was measured using the visual analogue scale. [Results] Concerning hamstring flexibility, P100 showed significant differences from P40 and P10, and P70 was significantly different from P10. At post-stretch, P100 significantly differed from P70, P40, and P10 in visual analogue scale. At 1 day, P100 significantly differed from P40 and P10. Although there was a significant correlation between post-stretch pain level and stretching intensity, there was no significant correlation between pain level and flexibility improvement. [Conclusion] Repetitive high-intensity stretching may cause heavy burden on muscle tissues, and pain caused by high-intensity stretching can hinder muscle performance. Moderate stretching intensity is recommended and considered conducive to maintaining the effects of stretching while ensuring its safety.

Brain tumors disrupt the resting-state connectome.

Brain tumor patients often experience functional deficits that extend beyond the tumor site. While resting-state functional MRI (rsfMRI) has been used to map such functional connectivity changes in brain tumor patients, the interplay between abnormal tumor vasculature and the rsfMRI signal is still not well understood. Therefore, there is an exigent need for new tools to elucidate how the blood­oxygenation-level-dependent (BOLD) rsfMRI signal is modulated in brain cancer. In this initial study, we explore the utility of a preclinical model for quantifying brain tumor-induced changes on the rsfMRI signal and resting-state brain connectivity. We demonstrate that brain tumors induce brain-wide alterations of resting-state networks that extend to the contralateral hemisphere, accompanied by global attenuation of the rsfMRI signal. Preliminary histology suggests that some of these alterations in brain connectivity may be attributable to tumor-related remodeling of the neurovasculature. Moreover, this work recapitulates clinical rsfMRI findings from brain tumor patients in terms of the effects of tumor size on the neurovascular microenvironment. Collectively, these results lay the foundation of a preclinical platform for exploring the usefulness of rsfMRI as a potential new biomarker in patients with brain cancer.

No significant correlation between the intensity of static stretching and subject's perception of pain.

[Purpose] The purpose of this study was to determine whether the intensity of static stretching measured quantitatively is related to subjects' perception of pain. [Subjects and Methods] Sixty-eight participants were recruited. Static stretching was performed once for 30 seconds while maintaining the knee at 0° flexion and was continued to the point where pain was recognized. The intensity of stretching exerted by the practitioner was quantitatively measured by using a handheld dynamometer (HHD). A subject's pain scaled on one's perception was measured by using the visual analog scale (VAS). [Results] No significant correlation was found between the intensity of stretching and the VAS score representing the subject's pain scaled on one's perception. In this study, the most frequent VAS score was 7, and the mean VAS score was 5.57 ± 1.77. The stretching intensity measured by using a HHD ranged from 28.4 to 133.0 N (mean, 72.04 ± 22.37 N). [Conclusion] This study showed that the intensity of stretching quantitatively measured by using HHD did not correlate with the degree of pain reported by the subjects. Therefore, subjective responses cannot guarantee a consistent application of intensity.

Energy Harvesting for GaAs Photovoltaics Under Low-Flux Indoor Lighting Conditions.

GaAs photovoltaics are promising candidates for indoor energy harvesting to power small-scale (≈1 mm2) electronics. This application has stringent requirements on dark current, recombination, and shunt leakage paths due to low-light conditions and small device dimensions. The power conversion efficiency and the limiting mechanisms in GaAs photovoltaic cells under indoor lighting conditions are studied experimentally. Voltage is limited by generation-recombination dark current attributed to perimeter sidewall surface recombination based on the measurements of variable cell area. Bulk and perimeter recombination coefficients of 1.464 pA/mm2 and 0.2816 pA/mm, respectively, were extracted from dark current measurements. Resulting power conversion efficiency is strongly dependent on cell area, where current GaAs of 1-mm2 indoor photovoltaic cells demonstrates power conversion efficiency of approximately 19% at 580 lx of white LED illumination. Reductions in both bulk and perimeter sidewall recombination are required to increase maximum efficiency (while maintaining small cell area near 1 mm2) to approach the theoretical power conversion efficiency of 40% for GaAs cells under typical indoor lighting conditions.

A 380pW Dual Mode Optical Wake-up Receiver with Ambient Noise Cancellation.

We present a sub-nW optical wake-up receiver for wireless sensor nodes. The wake-up receiver supports dual mode operation for both ultra-low standby power and high data rates, while canceling ambient in-band noise. In 0.18µm CMOS the receiver consumes 380pW in always-on wake-up mode and 28.1µW in fast RX mode at 250kbps.

Hindlimb muscle morphology and function in a new atrophy model combining spinal cord injury and cast immobilization.

Contusion spinal cord injury (SCI) animal models are used to study loss of muscle function and mass. However, parallels to the human condition typically have been confounded by spontaneous recovery observed within the first few post-injury weeks, partly because of free cage activity. We implemented a new rat model combining SCI with cast immobilization (IMM) to more closely reproduce the unloading conditions experienced by SCI patients. Magnetic resonance imaging was used to monitor hindlimb muscles' cross-sectional area (CSA) after SCI, IMM alone, SCI combined with IMM (SCI+IMM), and in controls (CTR) over a period of 21 days. Soleus muscle tetanic force was measured in situ on day 21, and hindlimb muscles were harvested for histology. IMM alone produced a decrease in triceps surae CSA to 63.9±4.9% of baseline values within 14 days. In SCI, CSA decreased to 75.0±10.5% after 7 days, and recovered to 77.9±10.7% by day 21. SCI+IMM showed the greatest amount of atrophy (56.9±9.9% on day 21). In all groups, muscle mass and soleus tetanic force decreased in parallel, such that specific force was maintained. Extensor digitorum longus (EDL) and soleus fiber size decreased in all groups, particularly in SCI+IMM. We observed a significant degree of asymmetry in muscle CSA in SCI but not IMM. This effect increased between day 7 and 21 in SCI, but also in SCI+IMM, suggesting a minor dependence on muscle activity. SCI+IMM offers a clinically relevant model of SCI to investigate the mechanistic basis for skeletal muscle adaptations after SCI and develop therapeutic approaches.

Silk amino acids improve physical stamina and male reproductive function of mice.

The effects of a silk amino acid (SAA) preparation on the physical stamina and male reproductive function of mice were investigated. Eight-week-old male ICR mice (29-31 g) were orally administered SAA (50, 160 or 500 mg/kg) for 44 d during 30-min daily swimming exercise. The mice were subjected to a weight-loaded (5% of body weight) forced swimming on the 14th, 28th and 42nd day to determine maximum swimming time, and after a 2-d recovery period (treated with SAA without swimming exercise), parameters related to fatigue and reproductive function were analyzed from blood, muscles and reproductive organs. Repeated swimming exercise increased the maximum swimming time to some extent, in spite of a marked reduction in body weight gain, and SAA further enhanced the stamina in a dose-dependent manner. Forced swimming exercises increased blood parameters of tissue injury, but depleted blood glucose and tissue glycogen, which were substantially prevented by SAA treatment. In addition, SAA significantly reduced the muscular thiobarbituric acid-reactive substances and blood corticosterone content increased by forced swimming. Swimming exercise decreased the blood testosterone level, which was recovered by SAA, leading to enhanced sperm counts. These combined results indicate that SAA not only enhances physical stamina by minimizing damage to tissues, including muscles, as well as preventing energy depletion caused by swimming stress, but also improves male reproductive function by increasing testosterone and sperm counts.