Prevalence and associated risk factors of sarcopenia in community-dwelling older adults in Pakistan: a cross-sectional study.

BACKGROUND: Advancements in medical facilities have led to an increase in global life expectancy, emphasizing the need to address age-related health issues. Sarcopenia, characterized by muscle mass loss, poses significant challenges for older adults. Despite a higher prevalence in Asian populations, there is a remarkable absence of studies addressing sarcopenia among the older adults in Pakistan. This research aims to determine sarcopenia prevalence, identify risk factors, and explore gender- and age-specific patterns among older adults in Pakistan. METHODS: A cross-sectional study involving 142 participants (65 males, 77 females) aged 60 and above was conducted using DEXA scans. Over a six-month period from January to June 2023, data were collected from the Islamabad Diagnostic Centre. This comprehensive dataset covered anthropometric measurements, body composition details, and health parameters. Statistical analyses, including logistic regression, were employed to examine the associations between sarcopenia and various factors. RESULTS: Sarcopenia manifested in 47.18% of the older adult population (n = 142), with a distribution of 39 males (60%) and 28 females (36.36%). The investigation unveiled a compelling correlation between underweight status and sarcopenia across genders. Indeed, males exhibited a significant negative correlation between skeletal muscle mass index and age, whereas females did not show a statistically significant association. Males presented higher odds of sarcopenia in comparison to females (Odds Ratio [OR] = 2.63, 95% Confidence Interval [CI]: 1.33-5.18, p = 0.005). Age (OR = 1.12, 95% CI: 1.02-1.22, p = 0.014), lower BMI (OR = 0.35, 95% CI: 0.20-0.60, p < 0.001), and reduced body fat percentage (OR = 1.75, 95% CI: 1.31-2.33, p < 0.001) emerged as significant contributors to sarcopenia. These detailed gender-specific findings emphasize the importance of customizing intervention strategies to address gender disparities in sarcopenia risk factors. CONCLUSION: This study highlights the significant prevalence of sarcopenia among older adults in Pakistan, with distinct gender and age-related patterns observed. The overall prevalence of sarcopenia was found to be 47.18%, with higher rates among males compared to females. Age emerged as a significant risk factor, with each additional year increasing the odds of sarcopenia. Furthermore, weight, BMI, lean mass, and total body fat demonstrated important associations with sarcopenia prevalence, highlighting the multifaceted nature of this condition. The practical implications of this study emphasize the need for targeted screening programs and personalized interventions to mitigate sarcopenia's impact, informing healthcare policies and public health strategies in Pakistan.

A randomized clinical trial on the changing of median nerve cross-sectional area and pain after extracorporeal shock wave and low-level laser therapy added to conventional physical therapy in patients with mild-to-moderate carpal tunnel syndrome.

BACKGROUND: Carpal tunnel syndrome (CTS) is the most common mononeuropathy in the upper limb. It remains uncertain whether adding extracorporeal shockwave therapy (ESWT) or low-level laser therapy (LLLT) to conventional treatment benefits CTS patients. PURPOSE: This study aimed to compare the effectiveness of ESWT and LLLT in conjunction with conventional treatments (including carpal mobilization, transcutaneous electrical nerve stimulation, and ultrasound) on the cross-sectional area (CSA) of the median nerve and pain in mild-to-moderate CTS patients. STUDY DESIGN: This was a single-blinded randomized clinical trial with registration number IRCT20220504054734N1. METHODS: Thirty-six patients were randomly assigned using block balanced randomization to receive either four sessions of ESWT or 10 sessions of LLLT in addition to 10 sessions of conventional treatments over 2 weeks. Patients received numbered closed envelopes indicating their treatment group. CSA (primary) and pain (secondary) in 18 patients who completed the treatment were assessed at baseline and after 2 weeks by a blinded assessor. Paired and independent sample t-tests were used for analyses due to the normal distribution of data was checked by Kolmogorov-Smirnoff. Cohen's d effect size was used to assess the intervention's magnitude. RESULTS: Both ESWT and LLLT groups showed significant improvements in CSA (p = 0.002) and pain (p < 0.001) from baseline to posttreatment. CSA improvement was moderate for ESWT (mean difference: 1.2, 95% CI 0.51-1.9) and mild for LLLT (mean difference: 0.76, 95% CI 0.4-1.14). Conversely, pain improvement was substantial in both groups (ESWT: mean difference 4.4, 95% CI 3.6-5.3; LLLT: mean difference 4.4, 95% CI 3.7-5.2). No substantial differences between ESWT and LLLT were observed, highlighting their comparable efficacy. CONCLUSION: The addition of either LLLT or ESWT to conventional treatment effectively reduced pain and median nerve CSA in mild-to-moderate CTS. The absence of significant differences between ESWT and LLLT indicates their comparable efficacy in pain relief and CSA reduction.

The Effect of Wii Training on Neurocognitive Function in Athletes with Functional Ankle Instability: Matched Randomized Clinical Trial.

Background: Many studies have investigated ankle sprain injury and it has been reported that in 80% of cases, ankle sprains lead to functional ankle instability (FAI). The conventional exercises for FAI rehabilitation neglect the associated neurocognitive dysfunction. Objective: This study aims to evaluate the effect of Wii Fit Plus as a virtual reality training on neurocognitive function in athletes with FAI compared to athletes without FAI. Material and Methods: In this matched randomized clinical trial study, 25 athletes with unilateral FAI and 25 athletes without FAI were assigned to two groups randomly: 1) the intervention group, subjects performed the Wii training including balance and strengthening games three times a week for 12 sessions and 2) subjects in the control group received no intervention. Before and after the training, the neurocognitive function was assessed through the computerized-reaction time test based on the detection or identification of 'X' mark on a computer monitor. Between-groups and within-group comparisons were done by the independent T-test and paired T-test, respectively. Results: A significant difference was observed in mean differences of neurocognitive function between athletes with and without FAI. Comprising before and after training was significant in the intervention group. Conclusion: Based on the results, the information-processing speed of athletes with FAI increased after the training, utilized for rehabilitation protocols.

Compare the Effect of Traditional and Virtual Reality Training on Subjective-sense of Instability and Balance in Basketball-players with Functional Ankle Instability: Matched Randomized Clinical Trial.

Background: Functional ankle instability (FAI) is a common injury. Traditional training improved the reported balance impairment and subjective sense of instability in athletes with FAI. Objective: This study aims to compare the effects of traditional and virtual reality training on a subjective sense of instability and balance in athlete with FAI. Material and Methods: In this single-blinded matched randomized clinical trial design, Fifty-four basketball players were randomly assigned in the virtual reality (n=27) or control (n=27) groups. All athletes performed 12 sessions Wii exercises or traditional training in the virtual reality and the control group, respectively, for three days a week. To assess the subjective-sense of instability and balance, we used Cumberland Ankle Instability Tool (CAIT) and Star Excursion Balance Test (SEBT), respectively. Measures were taken at pre- and post-test and one month after training as a follow-up. The between-group comparisons were done by the analysis of Covariance. Results: At the pre-test, the CAIT score was 22.37, 22.04 in the control and virtual reality groups, respectively and at the post-test, these scores increased to 26.63, 27.26. The involved limb showed significant differences in posteromedial and posterior directions of the SEBT and CAIT score in the post-test and in the posterior direction and CAIT score in the follow-up. The virtual reality group had better performance than the control group but the effect size is small (cohen's d<0.2). Conclusion: Based on our results, both training protocols were effective in reducing the subjective-sense of instability and improved balance in athletes with FAI. Moreover, virtual reality training was very attractive for the participants.

Effectiveness of ultrasound and median nerve gliding with and without shock-wave therapy in patients with moderate carpal tunnel syndrome.

[Purpose] The aim of this research was to see how ultrasound and nerve gliding with and without shock wave therapy effects on clinical and sonographic data of patients with carpal tunnel syndrome (CTS). [Participants and Methods] Forty four patients with moderate carpal tunnel syndrome participated in this research. One group got shock-wave therapy in addition to median nerve glide exercises and ultrasound, whereas the other group received median nerve glide exercises and ultrasound alone. Hand grip strength (HGS), pinch grip strength (PGS), Visual Analogue Scale (VAS)-pain, Boston Questionnaire (BQ), and Cross-sectional area (CSA) of median nerve were examined before and after 10 sessions of treatment. [Results] HGS, PGS, VAS, BQ and CSA of median nerve improved considerably after therapy. [Conclusion] Patients with moderate CTS who received ultrasound and median nerve glide exercises with and without shock-wave therapy improved considerably without preference of adding shock-wave therapy to other treatment.

Contribution of components of the quadriceps femoris muscle for producing external torque in patients with patellofemoral pain syndrome.

INTRODUCTION: Different muscular activities of the quadriceps components for producing necessary torque may change in patients with patellofemoral pain syndrome (PFPS). The aim of the current study, therefore, was to assess the contribution of each component of the quadriceps femoris muscle for producing external torque in patients with PFPS. METHOD: Twelve females with PFPS (24.7 ± 2.3 years) and twelve healthy matched females (25.4 ± 2.4 years) performed three consecutive knee flexion and extension movements with maximum effort at 45°/s and 300°/s using a Biodex system 3 dynamometer. Simultaneously, electromyographic (EMG) activities of the vastus medialis oblique (VMO), RF (rectus femoris) and vastus lateralis (VL) muscles were recorded using a DataLog instrument. Standard multiple regressions were used to assess the ability of EMG activities of the VMO, RF and VL muscles to predict normalized quadriceps femoris isokinetic concentric and eccentric torques at 45°/s and 300°/s in the normal and patient groups. RESULTS: In the normal group, the VL and the VMO were the good predictors of quadriceps concentric torque at 45°/s and 300°/s, respectively. The VL and the RF were the good predictors of quadriceps eccentric torque at 300°/s in the patient group. No other conditions showed a considerable prediction for quadriceps torque in the normal or patient group. CONCLUSION: Females with PFPS differ with normal females in terms of the contribution of each component of the quadriceps femoris for producing external torque. Training the VMO for concentric contraction at both high and low velocities should be included in the management of the patients with PFPS.

Comparison of the effects of Wii and conventional training on functional abilities and neurocognitive function in basketball-players with functional ankle instability: Matched randomized clinical trial.

OBJECTIVE: To compare the effects of Wii and conventional training on functional abilities and neurocognitive function in basketball-players with Functional Ankle Instability (FAI). DESIGN: Single-blind matched randomized clinical trial study. SETTING: Outpatients setting. PARTICIPANTS: Fifty-four basketball-players were randomly assigned to the Wii and control group. INTERVENTIONS: All athletes in the Wii group (n = 27) performed Wii Fit Plus games; and in the control group (n = 27), they performed conventional training three days a week for 12 sessions. MAIN OUTCOME MEASURES: To assess functional performance and neurocognitive function, we used hop tests (8-hop, side hop, and single hop) and Deary-Liewald Reaction Time Task (DLRT), respectively. DLRT measured simple and choice reaction time and error rate. Measures were taken at baseline, four weeks, and eight weeks after baseline. RESULTS: In all 54 athletes completed the study. The results showed no significant differences for all hop tests in between-group comparison but the neurocognitive function showed significant improvements in the Wii group compared to the control group (P < 0.05). Mean (SD) for 8-hop and side hop tests for the involved limb, and simple and choice reaction time four weeks after baseline in the control group were 10.15 (1.02), 12.36 (1.31), and 339.10 (41.57), 530.52 (53.36), respectively and in the Wii group, were 10.46 (1.23), 12.40 (1.31), and 295.25 (13.16), 431.19 (33.46), respectively. CONCLUSION: Based on our results, both training protocols were equal to positively affect functional abilities. Besides, Wii training improved neurocognitive function and can be applied in FAI rehabilitation protocols.

Reliability of ultrasound measurement of the lateral abdominal and lumbar multifidus muscles in individuals with chronic low back pain: A cross-sectional test-retest study.

OBJECTIVES: Ultrasound (US) imaging has been suggested to evaluate the morphology and function of trunk muscles; however, little is known about the reliability of the US measures in patients with chronic low back pain (CLBP). This study aimed to evaluate intrarater reliability of US imaging of the lateral abdominal and lumbar multifidus muscles in individuals with nonspecific CLBP. METHODS: In this cross-sectional study, intrarater within-day and between-day reliability of US measurements of the transversus abdominis, internal oblique, external oblique and lumbar multifidus (at the L3-L4, L4-L5, and L5-S1 levels) muscles were obtained on both sides. The resting and contracted thickness and contraction ratio of each muscle were measured in 21 individuals with nonspecific CLBP. RESULTS: All US measurements of the lateral abdominal and lumbar multifidus muscles demonstrated good to excellent within-day (Intraclass correlation coefficients (ICCs: 0.80-0.98) and between-day (ICCs: 0.80-0.97) reliability. The standard error of the measurement (SEMs) and minimal detectable change (MDCs) of the lateral abdominal muscles on both sides ranged 0.5-1.6 mm and 0.4-4.4 mm, respectively. The SEMs and MDCs of the LM muscles on both sides ranged 1.1-2.7 mm and 2.86-7.49 mm, respectively. CONCLUSION: The findings indicate that US imaging has good to high intrarater within- and between-day reliability for assessing absolute thickness and contraction ratio of the trunk muscles on both right and left sides in patients with nonspecific CLBP. The vertical alignment of the US transducer is a reliable method for assessing the lateral abdominal muscles.

Short-term effect of kinesiology taping on pain, functional disability and lumbar proprioception in individuals with nonspecific chronic low back pain: a double-blinded, randomized trial.

BACKGROUND: This study aimed to evaluate the effect of kinesiology taping (KT) on lumbar proprioception, pain, and functional disability in individuals with nonspecific chronic low back pain (CLBP). METHODS: Thirty individuals with nonspecific CLBP participated in this double-blinded, randomized clinical trial from July 2017 to September 2018. The participants were randomized into two groups: KT (n = 15) and placebo group (n = 15). KT was applied with 15-25% tension for 72 h, and placebo taping was used without tension. Lumbar repositioning error was measured by a bubble inclinometer at three different angles (45° and 60° flexion, and 15° extension) in upright standing. Pain and disability were assessed by the Short-Form McGill Pain Questionnaire and Oswestry Disability Index, respectively. All measurements were recorded at baseline and 3 days after taping. RESULTS: Pain and disability scores reduced 3 days after taping in the KT group with large effect sizes (p < 0.05). Only the total score of pain was significantly different between the groups 3 days after taping and improved more in the KT group with a large effect size (p < 0.05). However, lumbar repositioning errors were similar between the groups after 3 days (p > 0.05). Also, only constant error of 15° extension showed a moderate correlation with disability (r = 0.39, p = 0.02). CONCLUSION: KT can decrease pain and disability scores after 3 days of application. Although placebo taping can reduce pain, the effect of KT is higher than placebo taping. The findings do not support the therapeutic effect of KT and placebo taping as a tool to enhance lumbar proprioception in patients with nonspecific CLBP. TRIAL REGISTRATION: The study prospectively registered on 21.05.2018 at the Iranian Registry of Clinical Trials: IRCT20090301001722N20 .

Effects of dry needling on tendon-pulley architecture, pain and hand function in patients with trigger finger: a randomized controlled trial study.

[Purpose] The purpose of this study was to determine the effect of dry needling on tendon-pulley architecture, pain and hand function in patients with trigger finger. [Participants and Methods] A randomized controlled trial was conducted. Fifty eight patients having trigger finger were randomly assigned as either an experimental group that received a single session of dry needling over pulleyA1 and flexor tendon or a control group that received no intervention. Thickness of tendon-pulley, and pain-hand function (by disability arm-shoulder questionnaire score and pinch grip strength) were measured by a blinded assessor before and one week after intervention. [Results] The two way mixed ANOVA in the experimental group showed that the thickness of pulley-tendon decreased, pinch grip power increased and DASH questionnaire score was decreased in comparison to the control group. [Conclusion] This study results suggest that a single session of Dry Needling (DN) was effective in decreasing pain, DASH score, pulley-tendon thickness and improving pinch grip power in patients with trigger finger.

Effects of Peroneal Muscles Fatigue on Dynamic Stability Following Lateral Hop Landing: Time to Stabilization Versus Dynamic Postural Stability Index.

CONTEXT: Dynamic stability is a necessary requirement in many sports competitions. Muscle fatigue, which can impair stability, may be occurred in many sports competitions in which lateral movements and landing repeated frequently. OBJECTIVE: To assess the effects of peroneal muscles fatigue on dynamic stability following lateral hop landing through measuring time to stabilization (TTS) and dynamic postural stability index (DPSI). DESIGN: Quasi-experimental. SETTING: Laboratory study. PARTICIPANTS: A total of 20 recreationally active, healthy males with no lower-extremity injury during the previous 6 months participated in this study. INTERVENTION: Participants performed a lateral hop on a force plate before and immediately after a fatigue intervention using a Biodex dynamometer. For inducing fatigue, the participant made a prolonged eversion effort with 40% of the maximal voluntary contraction. Fatigue was met when the eversion torque declined by 50% of the initial value. TTS and DPSI were calculated using sequential averaging method and relevant formulas, respectively. MAIN OUTCOME MEASURES: Premeasures and postmeasures of TTS in the anteroposterior, mediolateral and vertical directions, resultant vector of TTS, stability indices in the anteroposterior, mediolateral and vertical directions, and DPSI. RESULTS: Means of the DPSI or its components did not change significantly due to fatigue (P > .05). Means of the TTS in the anteroposterior and mediolateral directions, and the mean of the resultant vector of the TTS increased significantly after fatigue (P < .05). CONCLUSIONS: The question that the dynamic stability is affected or not affected by fatigue depends on which of the TTS or DPSI is used for analysis. The TTS may be a sensitive measure to detect subtle changes in postural stability due to fatigue. But, the DPSI which may be changed after a more strenuous fatigue may be related to actual fatiguing situations.

Effect of Holmich protocol exercise therapy on long-standing adductor-related groin pain in athletes: an objective evaluation.

AIM: To objectively evaluate the effect of Holmich protocol-based exercise therapy on long-standing adductor-related groin pain (LSAGP). METHODS: We reproduced the Holmich protocol of exercise therapy and objectively evaluated its effect on 17 male athletes (mean age, 25.07±4.96 years) suffering from LSAGP, of whom 14 participants completed the 10 weeks treatment period. The study was designed as a single-blinded, before-and-after clinical trial. Main outcome measures included pain, functional ability, hip range of motion (ROM), hip abductor and adductor muscle strength, and successful return to sports activity. RESULTS: Eleven athletes (78.57%) returned to their sports activities in a mean time of 14.2 weeks (range, 10-20 weeks). Visual analogue scale pain score, hip abductor and adductor muscles strength, and function scores improved significantly. Although hip abduction ROM did not show any significant changes (p = 0.609), the extent of progress in the hip internal rotation ROM was significant (p = 0.001). The ratio of hip adduction to abduction strength did not change significantly (p = 0.309 for the isometric and p = 0.957 for the eccentric ratio). CONCLUSIONS: Exercise therapy according to the Holmich programme may be an effective treatment for LSAGP. However, more emphasis should be paid to the hip adductor muscles' eccentric strength. TRIAL REGISTRATION NUMBER: IRCT2016080829269N1.

Disturbance of neck proprioception and feed-forward motor control following static neck flexion in healthy young adults.

The highly complex proprioceptive system provides neuromuscular control of the mobile cervical spine. Static neck flexion can induce the elongation of posterior tissues and altered afferent input from the mechanoreceptors. The purpose of this study was to examine the effect of prolonged static neck flexion on neck proprioception and anticipatory postural adjustments. Thirty-eight healthy participants (20 females and 18 males) between the ages of 20-35 years with no history of neck, low back, and shoulder pain enrolled in this study. Neck proprioception and anticipatory muscle activity were tested before and after 10-min static neck flexion. For assessment of neck proprioception, each participant was asked to perform 10 trials of the cervicocephalic relocation test to the neutral head position after active neck rotation to the left and right sides. Anticipatory postural adjustments were evaluated during a rapid arm flexion test. Following the flexion, the absolute and variable errors in head repositioning significantly increased (p < 0.05). The results also showed that there was a significant delay in the onset of myoelectric activity of the cervical erector spinae muscles after flexion (p = 0.001). The results of this study suggested that a 10-min static flexion can lead to changes in the neck proprioception and feed-forward control due to mechanical and neuromuscular changes in the viscoelastic cervical spine structures. These changes in sensory-motor control may be a risk factor for neck pain and injury.

The Effect of Therapeutic Exercise on Long-Standing Adductor-Related Groin Pain in Athletes: Modified Hölmich Protocol.

OBJECTIVE: The Hölmich protocol in therapeutic exercise is the most appropriate method for the treatment of long-standing adductor-related groin pain (LSAGP). Herein, we evaluated a modified Hölmich protocol to resolve the possible limitations intrinsic to the Hölmich protocol in terms of the rate of return to sport and the recovery period for athletes with LSAGP. DESIGN: The study followed a single-blind, before/after study design, where 15 athletes with LSAGP (mean age = 26.13 years; SD = 4.48) performed a 10-week modified Hölmich therapeutic exercise protocol. RESULTS: Outcome scores related to pain, hip adductor and abductor muscle strengths, and the ratio of maximum isometric and eccentric hip adduction to abduction strength increased significantly. Likewise, hip abduction and internal rotation ROM improved significantly compared to that at baseline. Furthermore, functional records (t-test, Edgren Side Step Test, and Triple Hop Test) showed significant improvement after treatment. Finally, 13 athletes (86.6% of the participants) successfully returned to sports activity in a mean time of 12.06 weeks (SD = 3.41). CONCLUSION: The findings of this study objectively show that the modified Hölmich protocol may be safer and more effective than the Hölmich protocol in athletes with LSAGP in promoting their return to sports activity. This trial is registered with IRCT2016080829269N1.

The effect of static neck flexion on mechanical and neuromuscular behaviors of the cervical spine.

Occupations that involve sustained or repetitive neck flexion are associated with a higher incidence of neck pain. Little in vivo information is available on the impact of static neck flexion on cervical spinal tissue. The aim of this study was to assess changes in mechanical and neuromuscular behaviors to sustained neck flexion in healthy adults. Sixty healthy subjects aged 20-35 years participated in this study. The participants were exposed to static neck flexion at a fixed angle of full flexion for 10 min. Mechanical and neuromuscular responses of the cervical spine to sudden perturbations were measured pre- and post-exposure. Magnitude of load-relaxation during flexion exposure, stiffness, peak head angular velocity, and reflexive activities of cervical muscles were recorded. Effective neck stiffness decreased significantly, especially in female participants (P = 0.0001). The reflexive response of the cervical erector spinae muscles to head perturbation delayed significantly (P = 0.0001). Peak head angular velocity was significantly increased after exposure to neck flexion for 10 min, especially in female participants (P = 0.001). In the present study, static flexion resulted in changes in mechanical and neuromuscular behavior of the cervical spine, potentially leading to decreased stiffness of the cervical spine. The results confirm the importance of maintaining a correct head and neck position during work and improving the work environment to reduce the cervical spinal load and work-related neck pain.

Preparatory brain activity and anticipatory postural adjustments accompanied by externally cued weighted-rapid arm rise task in non-specific chronic low back pain patients and healthy subjects.

OBJECTIVE: Cortical reorganization is one of the most plausible mechanisms underlying impairment of anticipatory postural adjustments (APAs) in low back pain (LBP) patients. In order to clarify changes in corticomotor neurophysiology, APAs were assessed by using electromyography (EMG) and electroencephalography (EEG). METHODS: An equal number (29) of nonspecific LBP patients and healthy subjects performed unilateral rapid arm movements in response to auditory imperative stimulus preceded by warning stimulus within 2 s interstimulus interval. Burst onset activity was calculated in relation to the activity of anterior deltoid for bilateral transverse abdominis/internal oblique (TrA/IO), and also postural muscles on left side, including rectus abdominis, external oblique (E.O), erector spinae and medial head of gastrocnemius (Gc.M). Contingent negative variation (CNV) potentials were recorded by scalp EEG, and the area under receiver operating characteristic curve (AUC) was analyzed. RESULTS: In LBP patients, there was a significant onset delay for E.O and bilateral TrA/IO, but a significant earlier activity for Gc.M (for both P < 0.05). The CNV parameters were considerably greater in LBP patients (P < 0.01). The AUC was significant just for left TrA/IO and E.O muscles (P < 0.05). CONCLUSIONS: The CNV amplitudes were increased, and APA onset times re-organized to be delayed at the trunk and early at the distal limb in LBP cases. These findings support the hypothesis about reorganized activity of cerebral cortex in LBP patients.

Effect of static neck flexion in cervical flexion-relaxation phenomenon in healthy males and females.

INTRODUCTION: Neck pain is a common musculoskeletal disorder, especially among skilled workers who must keep their necks in a flexed position frequently during the day. The present study investigated changes in cervical flexion-relaxation phenomenon parameters after sustained neck flexion. METHODS: The participants were 40 healthy subjects grouped by gender (20 females, 20 males). They were exposed to static neck flexion at the full angle of cervical flexion for 10 min. Each subject underwent three trials of cervical flexion and re-extension before and after this period. Differences in onset and cessation angle of flexion-relaxation phenomenon, maximum neck flexion angle, amplitude of neck muscle activation and flexion-relaxation ratio were evaluated. RESULTS: The maximum neck flexion angle significantly increased after sustained flexion. The onset of flexion-relaxation was significantly delayed during flexion, but cessation angle remained unchanged. Myoelectric activity of the cervical erector spinae muscles increased significantly after maintaining flexion, especially in female subjects. The flexion-relaxation ratio also decreased significantly. CONCLUSION: It was concluded that 10 min of static flexion results in a delay in flexion-relaxation phenomenon and a shortened silence period. Also the cervical erector spinae muscles are required to be active longer and generate more activity. These neuromuscular changes may be a risk factor for neck pain.

Comparing the Effects of Peroneal Muscle Fatigue and Cyclic Loading on Ankle Neuromuscular Control During Lateral-Hop Landing.

CONTEXT: Cyclic movements and muscle fatigue may result in musculoskeletal injuries by inducing changes in neuromuscular control. Ankle frontal-plane neuromuscular control has rarely been studied in spite of its importance. OBJECTIVE: To compare the effects of peroneal muscle fatigue and a cyclic passive-inversion (CPI) protocol on ankle neuromuscular control during a lateral hop. DESIGN: Quasi-experimental, repeated measures. SETTING: University laboratory. PARTICIPANTS: 22 recreationally active, healthy men with no history of ankle sprain or giving way. INTERVENTIONS: Participants performed a lateral hop before and after 2 interventions on a Biodex dynamometer. They were randomly assigned to intervention order and interventions were 1 wk apart. A passive intervention included 40 CPIs at 5°/s through 80% of maximum range of motion, and a fatigue intervention involved an isometric eversion at 40% of the maximal voluntary isometric contraction until the torque decreased to 50% of its initial value. MAIN OUTCOME MEASURES: Median frequency of the peroneus longus during the fatigue protocol, energy absorption by the viscoelastic tissues during the CPI protocol, and feedforward onset and reaction time of the peroneus longus during landing. RESULTS: A significant fall in median frequency (P < .05) and a significant decrease in energy absorption (P < .05) confirmed fatigue and a change in viscoelastic behavior, respectively. There was a significant main effect of condition on feedforward onset and reaction time (P < .05). No significant main effect of intervention or intervention × condition interaction was noted (P > .05). There was a significant difference between pre- and postintervention measures (P < .0125), but no significant difference was found between postintervention measures (P > .0125). CONCLUSIONS: Both fatigue and the CPI may similarly impair ankle neuromuscular control. Thus, in prolonged sports competitions and exercises, the ankle may be injured due to either fatigue or changes in the biomechanical properties of the viscoelastic tissues.

Trunk muscle fatigue in subjects with a history of low back pain and a group of healthy controls measured by similarity index.

BACKGROUND: Trunk muscle fatigue has high relevance in human performance. Most authors agree that the use of the median frequency is preferred as a fatigue indicator. Most work has to date, been done on dynamic fatigue measurements, using the similarity index (SI). OBJECTIVE: Repeated trunk flexion-extensions were measured using the B200 Isostation. Muscle activity was recorded by surface electromyography (EMG) in order to evaluate fatigue of trunk flexor and extensor muscles. Twenty male university students participated in this pilot study, including 6 apparently healthy subjects with a history of low back pain (LBP), and 14 healthy matched controls. All participants were instructed to perform repeated trunk flexion-extension against 50% of their back extensors maximal volutary contractions (MVCs) resistance until they could no longer perform the task. The SI was calculated from quantitative analysis of EMG data recording during dynamic trunk flexion extension task. Median frequency was also measured before and after fatiguing contractions. RESULTS: The results of this study revealed a significant decrease in the SI and median frequency measurements following fatigue in both groups (p< 0.05). CONCLUSION: The results of this study indicated that in both groups changes in SI measurements following fatigue are in agreement with the changes in median frequency measurements.

Compensatory behavior of the postural control system to flexion-relaxation phenomena.

SUMMARY: Laxity of the passive tissues of the spine during prolonged spinal flexion has been shown to disturb spinal stability. This study investigated the effects of short periods of static lumbar flexion and short rest periods on the flexion-relaxation angle for the erector spinae muscles in 36 healthy female college students. The surface electromyographic activity of the erector spinae muscles was measured in three states before the onset of creep, immediately after 7 min of static lumbar flexion, and after a 10 min rest. The results showed that 7 min of static lumbar flexion will produce relaxation of the erector spinae muscles that occurs at greater absolute lumbar and trunk angles, during the forward bending activity (P<0.05), while the corresponding relative angles did not change before and after creep. The results also indicate that postural compensations are dominant over the muscular compensations for load sharing in flexion-relaxation phenomena of asymptomatic healthy participants. This further highlights the importance of postural modulation in the control of movement and preservation of skeletal stability. CLINICAL RELEVANCE: Considering spinal posture in the upright condition, and its changes by phenomena such as creep, can reduce postural injuries by instructing subjects to approach a more vertical posture, after periods of bending, to compensate the stretching effects of the tissues and thus regaining the normal muscular activity pattern.