Acute and Prolonged Effects of 300 sec of Static, Dynamic, and Combined Stretching on Flexibility and Muscle Force.

Static stretching (SS), dynamic stretching (DS), and combined stretching (CS; i.e., DS+SS) are commonly performed as warm-up exercises. However, the stretching method with the greatest effect on flexibility and performance remains unclear. This randomized crossover trial examined acute and prolonged effects of SS, DS, and CS on range of motion (ROM), peak passive torque (PPT), passive stiffness, and isometric and concentric muscle forces. Twenty healthy young men performed 300 sec of active SS, DS, or CS (150-sec SS followed by 150-sec DS and 150-sec DS followed by 150-sec SS) of the right knee flexors on four separate days, in random order. Subsequently, we measured ROM, PPT, and passive stiffness during passive knee extension. We also measured maximum voluntary isometric and concentric knee flexion forces and surface electromyographic activities during force measurements immediately before, immediately after, and 20 and 60 min after stretching. All stretching methods significantly increased ROM and PPT, while significantly decreasing isometric knee flexion force (all p < 0.05). These changes lasted 60 min after all stretching methods; the increases in ROM and PPT and the decreases in isometric muscle force were similar. All stretching methods also significantly decreased passive stiffness immediately after stretching (all p < 0.05). Decreases in passive stiffness tended to be longer after CS than after SS or DS. Concentric muscle force was decreased after SS and CS (all p < 0.05). On the other hand, concentric muscle force was unchanged after DS, while the decreases in surface electromyographic activities during concentric force measurements after all stretching methods were similar. Our results suggest that 300 sec of SS, DS, and CS have different acute and prolonged effects on flexibility and muscle force.

The First Case in Japan of Fulminant Myocarditis Due to Multisystem Inflammatory Syndrome in Children (MIS-C) That Required Mechanical Circulatory Support.

Multisystem inflammatory syndrome in children (MIS-C) is a novel hyperinflammatory syndrome that is associated with severe acute respiratory syndrome coronavirus 2 infections. Reports describing the mechanical circulatory support (MCS) and myocardial biopsy for fulminant myocarditis due to MIS-C are limited.A 13-year-old male patient with MIS-C underwent treatment, including immunosuppressive therapy and MCS devices, and managed to recover from pulseless electrical activity cardiac arrest.This is the first patient in Japan with MIS-C who required MCS devices in Japan. Appropriate and immediate treatment with immunosuppressive therapy and MCS devices is important.

Effects of High-Intensity Stretch with Moderate Pain and Maximal Intensity Stretch without Pain on Flexibility.

In this study, we aimed to identify the time course effects of different intensities of static stretch (SST) (maximal intensity without pain vs. high-intensity with moderate pain) on flexibility. This study included 16 healthy students (8 men and 8 women) who performed 1) 5-minute SST at 100%, 2) 110%, and 3) 120% intensity, as well as 4) no stretching (control) in a random sequence on four separate days. Static passive torque (SPT), hamstring electromyography (EMG), and pain intensity were continuously recorded during SST. We assessed markers of stiffness, range of motion (ROM), and maximal dynamic passive torque (DPTmax) before SST and 0, 15, 30, 45, 60, 75, and 90 minutes after SST. Stiffness decreased and ROM and DPTmax increased significantly immediately after SST at the three different intensity levels (p < 0.05). The effects of SST at 120% intensity were stronger and lasted longer than the effects of SST at 110% and 100% intensity (stiffness: -17%, -9%, and -7%, respectively; ROM: 14%, 10%, and 6%, respectively; DPTmax: 15%, 15%, and 9%, respectively). SPT decreased after SST at all intensities (p < 0.05). SST at 120% intensity caused a significantly greater reduction in SPT than SST at 100% intensity (p < 0.05). Pain intensity and EMG activity increased immediately after the onset of SST at 120% intensity (p < 0.05), although these responses were attenuated over time. Stretching intensity significantly correlated with the degree of change in ROM and stiffness (p < 0.05). These results support our hypothesis that stretch-induced flexibility is amplified and prolonged with an increase in stretch intensity beyond the pain threshold. Additional studies with more participants and different demographics are necessary to examine the generalizability of these findings.

Effects of a walking program in patients with chronic unilateral vestibular hypofunction.

[Purpose] Patients with chronic unilateral vestibular hypofunction show decreased postural stability and low levels of physical activity and also experience much anxiety. Physical activity is known to improve these symptoms; however, no study has reported any positive effects of physical activity, such as symptom reduction or improvement in function in these patients. In this study, we investigated the role of a walking program in improvement of dizziness, anxiety, and postural stability in this patient population. [Participants and Methods] This study included 21 patients with unilateral vestibular hypofunction and chronic dizziness. Patients were instructed to walk 30 min daily for 3 months. Physical activity levels and questionnaires for clinical symptoms, anxiety, and postural stability were evaluated before and after intervention. [Results] We observed significant differences in the amount of moderate-to-vigorous physical activity, clinical symptoms, and self-perceived handicap before and after the intervention. Additionally, anxiety levels were significantly reduced and postural stability was significantly improved in these patients. [Conclusion] A walking program improved physical activity levels, clinical symptoms, and postural stability and reduced self-perceived handicap and anxiety in patients with chronic unilateral vestibular hypofunction. These results highlight the effectiveness of a walking program for these patients and emphasize its role as a complementary vestibular rehabilitation strategy.

Acute and chronic effects of static stretching at 100% versus 120% intensity on flexibility.

PURPOSE: The acute effects of static stretching have been frequently studied, but the chronic effects have not been studied concurrently. Thus, this study aimed to investigate both the acute and chronic effects of static stretching at different intensities on flexibility. METHODS: Twenty-three healthy men were randomly assigned to perform 1 min of static stretching 3 days/week for 4 weeks at 100% intensity (n = 12) or 120% intensity (n = 11). The acute effects of stretching were assessed by measuring the range of motion (ROM), peak passive torque, and passive stiffness before and after every stretching session; the chronic effects of stretching were assessed by measuring these outcomes at baseline and after 2 and 4 weeks of stretching. RESULTS: Compared with the 100% intensity group, the 120% intensity group had significantly greater acute increases in ROM after all 12 sessions, a significantly greater decrease in passive stiffness after 11 of 12 sessions, and a significantly greater increase in peak passive torque after six of 12 sessions. Regarding the chronic effects, ROM was significantly increased in both groups after 2 and 4 weeks of stretching. Peak passive torque significantly increased in the 100% intensity group after 2 and 4 weeks of stretching, and after 4 weeks in the 120% intensity group. CONCLUSION: Stretching at 120% intensity resulted in significantly greater acute improvements in ROM, peak passive torque, and stiffness than stretching at 100% intensity. Four weeks of stretching increased ROM and peak passive torque but did not decrease passive stiffness, regardless of the stretching intensity.

Application of the novel estimation method by shear wave elastography using vibrator to human skeletal muscle.

In recent years, non-invasive measurement of tissue stiffness (hardness) using ultrasound elastography has attracted considerable attention. It has been used to evaluate muscle stiffness in the fields of rehabilitation, sports, and orthopedics. However, ultrasonic diagnostic devices with elastography systems are expensive and clinical use of such devices has been limited. In this study, we proposed a novel estimation method for vibration-based shear wave elastography measurement of human skeletal muscle, then determined its reproducibility and reliability. The coefficient of variation and correlation coefficient were used to determine reproducibility and reliability of the method by measuring the shear wave velocities in konjac phantom gels and agar phantom gels, as well as skeletal muscle. The intra-day, day-to-day, and inter-operator reliabilities were good when measuring the shear wave velocities in phantom gels. The intra-day and day-to-day reliabilities were good when measuring the shear wave velocities in skeletal muscle. The findings confirmed adequate reproducibility and reliability of the novel estimation method for vibration-based shear wave elastography. Therefore, the proposed measurement method may be a useful tool for evaluation of muscle stiffness.

Median nerve injury does not contribute to early onset of decreased grip strength due to repetitive reaching and grasping tasks in rats.

BACKGROUND: Workplace risk factors, such as repetitive tasks, can cause work-related musculoskeletal disorders. In a rat model, decreased grip strength and median nerve injury develop following repetitive reaching and grasping tasks, involving negligible force. OBJECTIVE: We investigated whether median nerve injury is involved in the early onset of decreased grip strength due to such tasks METHODS: Sprague-Dawley rats were divided into: non-task-performing (0-week) and task-performing (1-, 2-, and 3-week) groups. After an initial training period, the task-performing groups continued to perform the task for 2 h/day, 3 days/week, for 1-3 weeks. Grip strength and relative muscle weight of the flexor digitorum superficialis (FDS) muscle were measured. Median nerve injury was evaluated by histopathology and immunohistochemistry. RESULTS: Grip strength of the reach limb (forelimb used in tasks) was significantly lower in the 3-week group compared with the other groups and was significantly lower than that of the non-reach limb in all groups. There were no significant differences in the relative FDS muscle weights of either limb among groups. No evidence of median nerve demyelination was observed and no cells expressed activating transcription factor-3, a specific marker of peripheral nerve injury, in the anterior horn of the spinal cord. CONCLUSION: Median nerve injury does not contribute to the decreased grip strength caused by 3 weeks of repetitive reaching and grasping tasks, involving negligible force, in rats.

The protective role of localized nitric oxide production during inflammation may be mediated by the heme oxygenase-1/carbon monoxide pathway.

Nitric oxide (NO) is an important part of the host defense mechanism; however, it displays both pro- and anti-inflammatory properties depending on its location and concentration. Importantly, excessive or inappropriate NO production can cause tissue damage. Systemic and local administration of NO synthase (NOS) inhibitors ameliorates and may exacerbate the inflammatory response, respectively. Here, we used a carrageenan-induced pleurisy model of acute inflammation in rats to confirm the location-dependent effects of NO and investigate the underlying mechanisms. As expected, localized suppression of NO production exacerbated inflammation, as evidenced by increased pleural exudate volumes and leukocyte counts and enhanced activity of enzymes related to oxidative stress. In contrast, local NO supplementation reduced leukocyte infiltration, vascular permeability, and the activity of oxidative stress-related enzymes. Interestingly, inhibition of heme oxygenase-1 (HO-1) reversed the anti-inflammatory effects of localized NO production, while the addition of hemin (HO-1 substrate) or carbon monoxide (CO; HO-1 metabolite) decreased leukocyte migration and exudation. Together, these findings confirm a protective role for NO at the inflammatory site, which appears to be mediated via NOS induction of the HO-1/CO pathway. Thus, NO supplementation may be a potential new treatment for oxidative stress-associated inflammatory diseases.

Changes in Flexibility and Force are not Different after Static Versus Dynamic Stretching.

In this study, we examined the effects of static and dynamic stretching on range of motion (ROM), passive torque (PT) at pain onset, passive stiffness, and isometric muscle force. We conducted a randomized crossover trial in which 16 healthy young men performed a total of 300 s of active static or dynamic stretching of the right knee flexors on two separate days in random order. To assess the effects of stretching, we measured the ROM, PT at pain onset, passive stiffness during passive knee extension, and maximum voluntary isometric knee flexion force using an isokinetic dynamometer immediately before and after stretching. Both static and dynamic stretching significantly increased the ROM and PT at pain onset (p<0.01) and significantly decreased the passive stiffness and isometric knee flexion force immediately after stretching (p<0.01). However, the magnitude of change did not differ between the two stretching methods for any measurements. Our results suggest that 300 s of either static or dynamic stretching can increase flexibility and decrease isometric muscle force; however, the effects of stretching do not appear to differ between the two stretching methods.

Differences in postural stability and dynamic visual acuity among healthy young adults in relation to sports activity: a cross sectional study.

[Purpose] Sports activity has been shown to improve postural stability and vestibular function in healthy older adults. The hypothesis was that healthy young adults undertaking sports activity will also have better postural stability and vestibular function compared with healthy young adults who do not undertake sports activity. The purpose of this study was to investigate the differences in postural stability and vestibular function between healthy young adults who undertake sports activity and those who do not undertake such activity. [Participants and Methods] Thirty-nine healthy young adults were recruited and divided into sports and non-sports groups on the basis of their response to a questionnaire concerning regular participation in sports activities over the past 12 months. In both groups, postural stability was measured during quiet standing and standing during head rotation, and dynamic visual acuity was assessed during head rotation. [Results] The results showed significant differences in postural stability during head rotation and dynamic visual acuity between the two groups, whereas no significant differences were found in postural stability during quiet standing. [Conclusion] The results suggest that healthy young adults who undertake sports activity have better postural stability during head rotation and better dynamic visual acuity. The causal effect of these differences is not clear and further investigation is warranted.

Dynamic Stretching Has Sustained Effects on Range of Motion and Passive Stiffness of the Hamstring Muscles.

Dynamic stretching (DS) is often performed during warm-up to help avoid hamstring muscle injuries, increase joint flexibility, and optimize performance. We examined the effects of DS of the hamstring muscles on passive knee extension range of motion (ROM), passive torque (PT) at the onset of pain (as a measure of stretch tolerance), and passive stiffness of the muscle-tendon unit over an extended period after stretching. Twenty-four healthy subjects participated, with 12 each in the experimental and control groups. Stretching was performed, and measurements were recorded using an isokinetic dynamometer pre-intervention, and at 0, 15, 30, 45, 60, 75, and 90 min post-intervention. DS consisted of ten 30-s sets of 15 repetitions of extension and relaxation of the hamstrings. ROM increased significantly (range, 7%-10%) immediately after DS, and the increase was sustained over 90 min. PT at the onset of pain also increased immediately by 10% but returned to baseline by 30 min. Passive stiffness decreased significantly (range, 7.9%-16.7%) immediately after DS, and the decrease was sustained over 90 min. Post-DS values were normalized to pre-DS values for the respective outcomes in both groups. ROM was significantly higher (range, 7.4%-10%) and passive stiffness was significantly lower (range, 5.4%-14.9%) in the experimental group relative to the control group at all time points. Normalized PT values at the onset of pain were significantly higher in the experimental group at 0-15 min than in the controls, but the differences were smaller at 30-45 min and not significant thereafter. We conclude that DS increases ROM and decreases passive stiffness in a sustained manner, and increases PT at the onset of pain for a shorter period. Overall, our results indicate that when performed prior to exercise, DS is beneficial for the hamstring muscles in terms of increasing flexibility and reducing stiffness.

Objective measures of physical activity in patients with chronic unilateral vestibular hypofunction, and its relationship to handicap, anxiety and postural stability.

OBJECTIVE: Dizziness is one of the most common symptoms in the general population. Patients with dizziness experience balance problems and anxiety, which can lead to decreased physical activity levels and participation in their daily activities. Moreover, recovery of vestibular function from vestibular injury requires physical activity. Although there are reports that decreased physical activity is associated with handicap, anxiety, postural instability and reduced recovery of vestibular function in patients with chronic dizziness, these data were collected by self-report questionnaires. Therefore, the objective data of physical activity and the relationships between physical activity, handicap, anxiety and postural stability in patients with chronic dizziness are not clear. The purpose of this research was to objectively measure the physical activity of patients with chronic dizziness in daily living as well as handicap, anxiety and postural stability compared to healthy adults. Additionally, we aimed to investigate the relationships between physical activity, handicap, anxiety and postural stability in patients with chronic dizziness. METHODS: Twenty-eight patients with chronic dizziness of more than 3 months caused by unilateral vestibular hypofunction (patient group) and twenty-eight age-matched community dwelling healthy adults (healthy group) participated in this study. The amount of physical activity including time of sedentary behavior, light physical activity, moderate to vigorous physical activity and total physical activity using tri-axial accelerometer, self-perceived handicap and anxiety using questionnaires, and postural stability were measured using computerized dynamic posturography. RESULTS: The results showed worse handicap, anxiety and postural stability in the patient group compared to the healthy group. Objective measures of physical activity revealed that the patient group had significantly longer time of sedentary behavior, shorter time of light physical activity, and shorter time of total physical activity compared to the healthy group; however, time of moderate to vigorous physical activity was not significantly different between groups. Moreover, there were correlations between physical activity and postural stability in the patient group, while there were no correlations between physical activity, handicap or anxiety in the patient group. CONCLUSION: These results suggest that objectively measured physical activity of the patients with chronic unilateral vestibular hypofunction is lower compared to the healthy adults, and less active patients showed decreased postural stability. However, the details of physical activity and causal effect between physical activity and postural stability were not clear and further investigation is needed.

Hamstring Stiffness Returns More Rapidly After Static Stretching Than Range of Motion, Stretch Tolerance, and Isometric Peak Torque.

Context: Hamstring injuries are common, and lack of hamstring flexibility may predispose to injury. Static stretching not only increases range of motion (ROM) but also results in reduced muscle strength after stretching. The effects of stretching on the hamstring muscles and the duration of these effects remain unclear. Objective: To determine the effects of static stretching on the hamstrings and the duration of these effects. Design: Randomized crossover study. Setting: University laboratory. Participants: A total of 24 healthy volunteers. Interventions: The torque-angle relationship (ROM, passive torque [PT] at the onset of pain, and passive stiffness) and isometric muscle force using an isokinetic dynamometer were measured. After a 60-minute rest, the ROM of the dynamometer was set at the maximum tolerable intensity; this position was maintained for 300 seconds, while static PT was measured continuously. The torque-angle relationship and isometric muscle force after rest periods of 10, 20, and 30 minutes were remeasured. Main Outcome Measures: Change in static PT during stretching and changes in ROM, PT at the onset of pain, passive stiffness, and isometric muscle force before stretching were compared with 10, 20, and 30 minutes after stretching. Results: Static PT decreased significantly during stretching. Passive stiffness decreased significantly 10 and 20 minutes after stretching, but there was no significant prestretching versus poststretching difference after 30 minutes. PT at the onset of pain and ROM increased significantly after stretching at all rest intervals, while isometric muscle force decreased significantly after all rest intervals. Conclusions: The effect of static stretching on passive stiffness of the hamstrings was not maintained as long as the changes in ROM, stretch tolerance, and isometric muscle force. Therefore, frequent stretching is necessary to improve the viscoelasticity of the muscle-tendon unit. Muscle force decreased for 30 minutes after stretching; this should be considered prior to activities requiring maximal muscle strength.

Farming habit, light exposure, physical activity, and depressive symptoms. A cross-sectional study of the HEIJO-KYO cohort.

BACKGROUND: Bright light therapy and exercise interventions are effective methods for treating seasonal and non-seasonal affective disorders. Synchronization of internal circadian rhythms with the external environment by light therapy and physical activity may partly explain its efficacy. In the present study, we objectively measured daytime light exposure and physical activity in real life situations with elderly participants, and investigated the association between farming habits and the prevalence of depressive symptoms. METHODS: This cross-sectional was conducted among 1005 participants (mean age: 71.5) of a community-based cohort study. Depressive symptoms were assessed by the Geriatric Depression Scale (GDS score ≥ 6) and administration of antidepressant. RESULTS: Farming habit with long duration (> 7.0 h/week) showed significantly lower odds ratios (OR) for depressive symptoms (adjusted OR 0.63, 95% confidential interval,0.41 to 0.96) compared with participants without farming habit independent of confounders such as age, gender, body mass index smoking, drinking, daytime ambulatory systolic blood pressure, diabetes, living alone, education, income, and daylength. Even in farming with short duration (≤ 7.0 h/week), we found significant association with lower OR for depressive symptoms (adjusted OR 0.64, 95%CI, 0.42 to 0.97). Light exposure and daytime physical activity measured by wrist actigraphy were significantly higher among participants with longer farming habits (p for trend < 0.01). Physical activity mediated 12.0% of association between farming habit and depressive symptoms. LIMITATIONS: A cross-sectional association may be found because the participants with depressive symptoms tended to avoid farming. A longitudinal study is warranted to determine the direction of causality. CONCLUSIONS: Participants with farming habit showed significantly lower OR for depressive symptoms than those without farming habit, and it was partly mediated by physical activity.

Objective sleep quality and night-time blood pressure in the general elderly population: a cross-sectional study of the HEIJO-KYO cohort.

OBJECTIVES: Night-time blood pressure (BP) - prognostically more important than circadian BP variability - has not been evaluated for quantitative associations with objective sleep quality in large populations. METHODS: The cross-sectional study measured actigraphic sleep parameters and night-time BP for two nights in 1101 elderly participants. RESULTS: Mean age of the participants was 71.8 years, and mean night-time SBP and DBP were 115.9 ±â€Š16.2 and 66.9 ±â€Š8.4 mmHg, respectively. Multivariable analysis controlling for potential confounders revealed that the lowest sleep efficiency quartile group exhibited significantly higher night-time SBP and DBP than the highest quartile group [mean difference: SBP, 4.7 mmHg, 95% confidence interval (CI), 2.0-7.3; DBP, 2.3 mmHg, 95% CI 0.9-3.7]. The longest wake after sleep onset and sleep-onset latency quartile groups exhibited significantly higher night-time SBP (3.1 mmHg, 95% CI 0.3-5.9 and 3.4 mmHg, 95% CI 0.8-6.0) and DBP (2.0 mmHg, 95% CI 0.5-3.5 and 1.9 mmHg 95% CI 0.5-3.3), respectively, than the shortest quartile group. Significantly lower night-time SBP (3.0 mmHg, 95% CI 0.01-6.1) was observed in the longest total sleep time quartile group than in the shortest quartile group. These results were similar on sensitivity analyses excluding participants with possible sleep-disordered breathing (n = 69) or nocturnal hypertension (n = 503). CONCLUSION: Decreased sleep quality on actigraphy was significantly associated with higher night-time BP in a large general elderly population. Clinically significant increase in night-time BP exists in relation to decreased objective sleep quality.

Acute Effects of the Different Intensity of Static Stretching on Flexibility and Isometric Muscle Force.

Kataura, S, Suzuki, S, Matsuo, S, Hatano, G, Iwata, M, Yokoi, K, Tsuchida, W, Banno, Y, and Asai, Y. Acute effects of the different intensity of static stretching on flexibility and isometric muscle force. J Strength Cond Res 31(12): 3403-3410, 2017-In various fields, static stretching is commonly performed to improve flexibility, whereas the acute effects of different stretch intensities are unclear. Therefore, we investigated the acute effects of different stretch intensities on flexibility and muscle force. Eighteen healthy participants (9 men and 9 women) performed 180-second static stretches of the right hamstrings at 80, 100, and 120% of maximum tolerable intensity without stretching pain, in random order. The following outcomes were assessed as markers of lower limb function and flexibility: static passive torque (SPT), range of motion (ROM), passive joint (muscle-tendon) stiffness, passive torque (PT) at onset of pain, and isometric muscle force. Static passive torque was significantly decreased after all stretching intensities (p ≤ 0.05). Compared with before stretching at 100 and 120% intensities, ROM and PT were significantly increased after stretching (p ≤ 0.05), and passive stiffness (p = 0.05) and isometric muscle force (p ≤ 0.05) were significantly decreased. In addition, ROM was significantly greater after stretching at 100 and 120% than at 80%, and passive stiffness was significantly lower after 120% than after 80% (p ≤ 0.05). However, all measurements except SPT were unchanged after 80% intensity. There was a weak positive correlation between the intensities of stretching and the relative change for SPT (p ≤ 0.05), a moderate positive correlation with ROM (p ≤ 0.05), and a moderate positive correlation with passive stiffness (p ≤ 0.05). These results indicate that static stretching at greater intensity is more effective for increasing ROM and decreasing passive muscle-tendon stiffness.

Heat Stress Modulates Both Anabolic and Catabolic Signaling Pathways Preventing Dexamethasone-Induced Muscle Atrophy In Vitro.

It is generally recognized that synthetic glucocorticoids induce skeletal muscle weakness, and endogenous glucocorticoid levels increase in patients with muscle atrophy. It is reported that heat stress attenuates glucocorticoid-induced muscle atrophy; however, the mechanisms involved are unknown. Therefore, we examined the mechanisms underlying the effects of heat stress against glucocorticoid-induced muscle atrophy using C2C12 myotubes in vitro, focusing on expression of key molecules and signaling pathways involved in regulating protein synthesis and degradation. The synthetic glucocorticoid dexamethasone decreased myotube diameter and protein content, and heat stress prevented the morphological and biochemical glucocorticoid effects. Heat stress also attenuated increases in mRNAs of regulated in development and DNA damage responses 1 (REDD1) and Kruppel-like factor 15 (KLF15). Heat stress recovered the dexamethasone-induced inhibition of PI3K/Akt signaling. These data suggest that changes in anabolic and catabolic signals are involved in heat stress-induced protection against glucocorticoid-induced muscle atrophy. These results have a potentially broad clinical impact because elevated glucocorticoid levels are implicated in a wide range of diseases associated with muscle wasting. J. Cell. Physiol. 232: 650-664, 2017. © 2016 The Authors. Journal of Cellular Physiology published by Wiley Periodicals, Inc.

Acute effects of different stretching durations on passive torque, mobility, and isometric muscle force.

Static stretching is widely applied in various disciplines. However, the acute effects of different durations of stretching are unclear. Therefore, this study was designed to investigate the acute effects of different stretching durations on muscle function and flexibility, and provide an insight into the optimal duration of static stretching. This randomized crossover trial included 24 healthy students (17 men and 7 women) who stretched their right hamstrings for durations of 20, 60, 180, and 300 seconds in a random order. The following outcomes were assessed using an isokinetic dynamometer as markers of lower-limb function and flexibility: static passive torque (SPT), dynamic passive torque (DPT), stiffness, straight leg raise (SLR), and isometric muscle force. Static passive torque was significantly decreased after all stretching durations (p < 0.05). Static passive torque was significantly lower after 60, 180, and 300 seconds of stretching compared with that after 20-second stretching, and stiffness decreased significantly after 180- and 300-second stretching (p < 0.05). In addition, DPT and stiffness were significantly lower after 300 seconds than after 20-second stretching (p < 0.05), and SLR increased significantly after all stretching durations (p < 0.05). Straight leg raise was higher after 180- and 300-second stretching than after 20-second stretching and higher after 300-second stretching than after 60-second stretching (p < 0.05). Isometric muscle force significantly decreased after all stretching durations (p < 0.05). Therefore, increased duration of stretching is associated with a decrease in SPT but an increase in SLR. Over 180 seconds of stretching was required to decrease DPT and stiffness, but isometric muscle force decreased regardless of the stretching duration. In conclusion, these results indicate that longer durations of stretching are needed to provide better flexibility.

Effect of oculo-motor and gaze stability exercises on postural stability and dynamic visual acuity in healthy young adults.

The purpose of this study was to investigate the effectiveness of oculo-motor exercises and gaze stability exercises on postural stability and dynamic visual acuity (DVA) in healthy young adults. Subjects were randomly divided into experimental (n=28) and control groups (n=13). The experimental group performed oculo-motor exercises and gaze stability exercise for three weeks and the control group did not. Pre and post postural stability during quiet standing, standing with active head rotation, and DVA were measured on both groups. Significant differences were found in postural stability during standing with active head rotation and DVA in the experimental group (p<0.05). No significant differences were found in postural stability or DVA in the control group. Improvements in postural stability and DVA after three weeks of oculo-motor exercises and gaze stability exercises suggest that this specific type of vestibular and ocular system exercises may be beneficial for healthy young adults.

Involvement of nitric oxide in a rat model of carrageenin-induced pleurisy.

Some evidence indicates that nitric oxide (NO) contributes to inflammation, while other evidence supports the opposite conclusion. To clarify the role of NO in inflammation, we studied carrageenin-induced pleurisy in rats treated with an NO donor (NOC-18), a substrate for NO formation (L-arginine), and/or an NO synthase inhibitor (S-(2-aminoethyl) isothiourea or N(G)-nitro-L-arginine). We assessed inflammatory cell migration, nitrite/nitrate values, lipid peroxidation and pro-inflammatory mediators. NOC-18 and L-arginine reduced the migration of inflammatory cells and edema, lowered oxidative stress, and normalized antioxidant enzyme activities. NO synthase inhibitors increased the exudate formation and inflammatory cell number, contributed to oxidative stress, induced an oxidant/antioxidant imbalance by maintaining high O(2) (-), and enhanced the production of pro-inflammatory mediators. L-arginine and NOC-18 reversed the proinflammatory effects of NO synthase inhibitors, perhaps by reducing the expression of adhesion molecules on endothelial cells. Thus, our results indicate that NO is involved in blunting-not enhancing-the inflammatory response.