Bilateral Contractions Research Articles

Effect of home-based isometric training on blood pressure in older adults with high normal BP or stage I hypertension: A randomized controlled trial.

This trial analyzes the effects of home-based isometric handgrip training (IHT) and aerobic exercise training (AET) on ambulatory and office blood pressure (BP) in older adults with high normal to established hypertension. This randomized controlled trial included 84 participants (46 women, 71.1 ± 3.6 years, systolic BP [SBP] 137.1 ± 13.8 mmHg, diastolic BP [DBP] 80.8 ± 8.3 mmHg). Participants were randomized into IHT (n = 28), AET (n = 28), or usual medical care plus lifestyle advice (UC, n = 28). Participants performed IHT or AET three times/week for 8 weeks. IHT consisted of 4 × 45 s bilateral contractions at 50% of maximum voluntary contraction with 1-min rest between sets. AET consisted of walking 30 min at 50%-70% of estimated maximum oxygen consumption. UC received standardized medical care including lifestyle advice. Seventy-six participants completed the intervention: 27 in IHT, 26 in AET, and 23 in UC. At baseline, BP values were similar among groups. No differences were observed in 24-h ambulatory, daytime, and nighttime SBP and DBP in any group (p > 0.05). IHT and AET reduced office SBP (-8.0 ± 13.4 mmHg; p = 0.004; -5.6 ± 12.2 mmHg; p = 0.027, respectively). IHT reduced office DBP (-3.3 ± 7.4 mmHg; p = 0.024), but AET did not. No differences occurred in office BP in UC. There was no difference in office BP among groups (p > 0.05). An 8-week home-based IHT and AET failed to reduce ambulatory SBP, while office SBP was reduced by 8/5 mmHg. Only IHT reduced office DBP by 3 mmHg. Thus, IHT and AET may be effective for lowering office BP in older adults with high normal to established hypertension.

Bilateral hand dystonia following high-velocity thrust manipulation: a case report.

Thrust manipulation is one of the most commonly used techniques for managing musculoskeletal pain in clinical practice. This involves the application of a high-velocity, low-amplitude force directed to the joints with the intent of achieving joint cavitation. This current case report describes a female in her mid-20s who presented with excessive bilateral and involuntary hand muscle contractions after bilateral thrust manipulation. Dystonia appeared both at rest and during voluntary movements but was aggravated by actions such as finger flexion or spreading and disappeared during sleep. A diagnosis of complex regional pain syndrome (CRPS) type I combined with dystonia was made. Prednisolone administered between 2 and 5 weeks after symptom onset significantly reduced CRPS symptoms, but intramuscular botulinum toxin injection 5 weeks after symptom onset was ineffective at controlling her symptoms. Seven weeks after symptom onset, the patient was administered 2 mg trihexyphenidyl oral twice a day, 2.5 mg diazepam oral twice a day and 5 mg baclofen oral three times a day for 1 month and this significantly reduced dystonia, but complete resolution was not achieved. Clinicians should be aware that dystonia is a rare complication of thrust manipulation.

A 32-year old lady who developed a complex generalized movement disorder in all four limbs after plasma exchange for myelitis

A 32-year old lady with AQP4-Antibody positive neuromyelitis optica developed a new-onset complex movement disorder after therapeutic plasma exchange, which was initially suspected to be hypocalcemic carpo-pedal spasm. However, when her bilateral, distal predominant, paroxysmal, stereotypic, wrist and finger flexor tonic contractions did not respond to serum calcium correction, other diagnoses were considered. The patient had a dramatic response to oral carbamazepine suggesting that the tonic spasms were likely a spinal movement disorder due to the primary demyelinating pathology.

Localized Changes in Dentate Nucleus Shape and Magnetic Susceptibility in Friedreich Ataxia.

The dentate nuclei of the cerebellum are key sites of neuropathology in Friedreich ataxia (FRDA). Reduced dentate nucleus volume and increased mean magnetic susceptibility, a proxy of iron concentration, have been reported by magnetic resonance imaging studies in people with FRDA. Here, we investigate whether these changes are regionally heterogeneous. Quantitative susceptibility mapping data were acquired from 49 people with FRDA and 46 healthy controls. The dentate nuclei were manually segmented and analyzed using three dimensional vertex-based shape modeling and voxel-based assessments to identify regional changes in morphometry and susceptibility, respectively. Individuals with FRDA, relative to healthy controls, showed significant bilateral surface contraction most strongly at the rostral and caudal boundaries of the dentate nuclei. The magnitude of this surface contraction correlated with disease duration, and to a lesser extent, ataxia severity. Significantly greater susceptibility was also evident in the FRDA cohort relative to controls, but was instead localized to bilateral dorsomedial areas, and also correlated with disease duration and ataxia severity. Changes in the structure of the dentate nuclei in FRDA are not spatially uniform. Atrophy is greatest in areas with high gray matter density, whereas increases in susceptibility-reflecting iron concentration, demyelination, and/or gliosis-predominate in the medial white matter. These findings converge with established histological reports and indicate that regional measures of dentate nucleus substructure are more sensitive measures of disease expression than full-structure averages. Biomarker development and therapeutic strategies that directly target the dentate nuclei, such as gene therapies, may be optimized by targeting these areas of maximal pathology. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neuromuscular Characteristics of Unilateral and Bilateral Maximal Voluntary Isometric Contractions following ACL Reconstruction.

Despite the advancement of diagnostic surgical techniques in anterior cruciate ligament (ACL) reconstruction and rehabilitation protocols following ACL injury, only half of the athletes return to sports at a competitive level. A major concern is neuromechanical dysfunction, which occurs with injuries persisting in operated and non-operated legs following ACL rehabilitation. One of the criteria for a safe return to sports participation is based on the maximal voluntary isometric contraction (MVIC) performed unilaterally and a comparison between the 'healthy knee' and the 'operated knee'. The present study aimed to investigate MVIC in athletes following ACL rehabilitation during open kinetic chain exercise performed unilaterally and bilateral exercises. Twenty subjects participated in the present investigation: 10 male athletes of regional-national level (skiers, rugby, soccer, and volleyball players) who were previously operated on one knee and received a complete rehabilitation protocol (for 6-9 months) were included in the ACL group (age: 23.4 ± 2.11 years; stature: 182.0 ± 9.9 cm; body mass: 78.6 ± 9.9 kg; body mass index: 23.7 ± 1.9 kg/m2), and 10 healthy male athletes formed the control group (CG: age: 24.0 ± 3.4 years; stature: 180.3 ± 10.7 cm; body mass: 74.9 ± 13.5 kg; body mass index: 22.8 ± 2.7 kg/m2). MVICs synchronised with electromyographic (EMG) activity (recorded on the vastus lateralis, vastus medialis, and biceps femoris muscles) were performed during unilateral and bilateral exertions. The rate of force development (RFD) and co-activation index (CI) were also calculated. The differences in the MVIC and RFD between the two legs within each group were not significant (p > 0.05). Vastus lateralis EMG activity during MVIC and biceps femoris EMG activity during RFD were significantly higher in the operated leg than those in the non-operated leg when exertion was performed bilaterally (p < 0.05). The CI was higher in the operated leg than that in the non-operated leg when exertion was performed bilaterally (p < 0.05). Vice versa, vastus medialis EMG activity during RFD was significantly higher in the right leg than that in the left leg when exertion was performed bilaterally (p < 0.05) in the CG. MVICs performed bilaterally represent a reliability modality for highlighting neuromechanical asymmetries. This bilateral exercise should be included in the criteria for a safe return to sports following ACL reconstruction.

Ankle Strategies for Step-Aside Movement during Straight Walking.

The step-aside movement, also known as the dodging step, is a common maneuver for avoiding obstacles while walking. However, differences in neural control mechanisms and ankle strategies compared to straight walking can pose a risk of falling. This study aimed to examine the differences in tibialis anterior (TA), peroneus longus (PL), and soleus (SOL) muscle contractions, foot center of pressure (CoP) displacement, and ground reaction force (GRF) generation between step-aside movement and straight walking to understand the mechanism behind step-aside movement during walking. Twenty healthy young male participants performed straight walking and step-aside movements at comfortable walking speeds. The participants' muscle contractions, CoP displacement, and GRF were measured. The results show significant greater bilateral ankle muscle contractions during the push and loading phases of step-aside movement than during straight walking. Moreover, the CoP displacement, GRF generation mechanism, and timing differed from those observed during straight walking. These findings provide valuable insights for rehabilitation professionals in the development of clinical decisions for populations at a risk of falls and lacking gait stability.

The role of ipsilateral motor network in upper limb movement.

The execution of voluntary movements is primarily governed by the cerebral hemisphere contralateral to the moving limb. Previous research indicates that the ipsilateral motor network, comprising the primary motor cortex (M1), supplementary motor area (SMA), and premotor cortex (PM), plays a crucial role in the planning and execution of limb movements. However, the precise functions of this network and its interplay in different task contexts have yet to be fully understood. Twenty healthy right-handed participants (10 females, mean age 26.1 ± 4.6years) underwent functional MRI scans while performing biceps brachii representations such as bilateral, unilateral flexion, and bilateral flexion-extension. Ipsilateral motor evoked potentials (iMEPs) were obtained from the identical set of participants in a prior study using transcranial magnetic stimulation (TMS) targeting M1 while employing the same motor tasks. The voxel time series was extracted based on the region of interest (M1, SMA, ventral PM and dorsal PM). Directed functinal connectivity was derived from the extracted time series using time-resolved partial directed coherence. We found increased connectivity from left-PMv to both sides M1, as well as right-PMv to both sides SMA, in unilateral flexion compared to bilateral flexion. Connectivity from left M1 to left-PMv, and left-SMA to right-PMd, also increased in both unilateral flexion and bilateral flexion-extension compared to bilateral flexion. However, connectivity between PMv and right-M1 to left-PMd decreased during bilateral flexion-extension compared to unilateral flexion. Additionally, during bilateral flexion-extension, the connectivity from right-M1 to right-SMA had a negative relationship with the area ratio of iMEP in the dominant side. Our results provide corroborating evidence for prior research suggesting that the ipsilateral motor network is implicated in the voluntary movements and underscores its involvement in cognitive processes such as movement planning and coordination. Moreover, ipsilateral connectivity from M1 to SMA on the dominant side can modulate the degree of ipsilateral M1 activation during bilateral antagonistic contraction.

Surface electromyography analysis of core stabilizing muscles during isometric shoulder contractions in athletes with low back pain

BackgroundThe study was carried out in the athletes with and without Low Back Pain (LBP) to determine the surface electromyography activity of core stabilizing muscles while performing isometric shoulder and trunk contractions. Study designCross-sectional study. MethodsThis study enlisted the participation of 40 athletes. Group A included 20 athletes (18 males and 2 females) without LBP, and Group B included 20 athletes (12 males and 8 females) with LBP. Athletes with LBP were assessed using the Modified Oswestry Disability Questionnaire (MODQ) and Visual Analog Scale (VAS) to determine their level of disability and pain severity, respectively. EMG activity of the rectus abdominis, external oblique, longissimus, and multifidus was recorded in both groups as they performed bilateral isometric shoulder and trunk contractions. ResultsIn the LBP group, EMG activity of the rectus abdominis and external oblique muscles was significantly lower (P < 0.05). The LBP group had significantly more multifidus activity (P = 0.03) than the NLBP group. Among all the exercises, bilateral isometric shoulder extension contraction activated the rectus abdominis, right external oblique, and longissimus group of muscles significantly more (P < 0.05) in both groups. In both groups, bilateral isometric shoulder flexion contraction resulted in significantly higher multifidus muscle activation (P = 0.002). ConclusionThe activation of core stabilizing muscles was altered in athletes with LBP. When athletes are unable to contract and activate trunk muscles owing to pain, upper extremity exercises can be used to activate these muscles.

Axial Postural Abnormalities in Parkinsonism: Gaps in Predictors, Pathophysiology, and Management.

Axial Postural Abnormalities in Parkinsonism: Gaps in Predictors, Pathophysiology, and Management.

Bilateral Force Deficit in Proximal Effectors Versus Distal Effectors in Lower Extremities

ABSTRACT Purpose: Bilateral force deficit occurs when the maximal generated force during simultaneous bilateral muscle contractions is lower than the sum of forces generated unilaterally. Neural inhibition is stated as the main source for bilateral force deficit. Based on differences in bilateral neural organization, there might be a pronounced neural inhibition for proximal compared to distal effectors. The aim of the present experiment was to evaluate potential differences in bilateral force deficit in proximal compared to distal effectors in lower extremities. Methods: Fifteen young adults performed single-joint maximal voluntary contractions in isometric dorsiflexion of ankle (distal) and knee (proximal) extension unilaterally and bilaterally. Results: Results showed a significant absolute bilateral force deficit for both proximal (123.46 ± 59.51 N) and distal effectors (33.00 ± 35.60 N). Interestingly, the relative bilateral force deficit for knee extension was significantly larger compared to dorsiflexion of ankle, 19.98 ± 10.04% and 10.27 ± 9.57%, respectively. Our results indicate a significantly higher bilateral force deficit for proximal effectors compared to distal effectors. Conclusion: Plausible explanations are related to neuroanatomical and neurophysiological differences between proximal effectors and distal effectors where proximal muscles have a higher potential for bilateral communication compared to distal muscles. In addition, higher forces produced with proximal effectors could cause a higher perceived exertion and cause a more pronounced bilateral force deficit to proximal effectors.

Termination of seizures by ictal transcranial focal cortex stimulation.

Whereas high-level evidence exists on chronic neuromodulatory effects of different brain stimulation approaches in reducing seizure frequency, evidence for acute antiseizure effects of electrical brain stimulation during seizures is sparse. As part of an ongoing trial, we implanted a patient with a novel focal cortex stimulation (FCS) device with a Laplacian electrode placed over a precentral focal cortical dysplasia. The baseline seizure frequency was 125 per month, consisting of (i) focal aware sensory seizures that invariably progressed to uni- or bilateral tonic contraction and clonic jerking, and (ii) primary motor seizures. Besides an overall reduction in seizure frequency, on-demand stimulation had an immediate effect on seizures with a sensory phase, whereby 63%-86% of these seizures were terminated by ictal stimulation. These observations provide the first evidence that ictal self-triggered transcranial focal cortex stimulation can significantly interfere with the progression of seizure semiology.

The middle ear muscle reflex: Current and future role in assessing noise-induced cochlear damage.

The middle ear muscle reflex (MEMR) in humans is a bilateral contraction of the middle ear stapedial muscle in response to moderate-to-high intensity acoustic stimuli. Clinically, MEMR thresholds have been used for differential diagnosis of otopathologies for decades. More recently, changes in MEMR amplitude or threshold have been proposed as an assessment for noise-induced synaptopathy, a subclinical form of cochlear damage characterized by suprathreshold hearing problems that occur as a function of inner hair cell (IHC) synaptic loss, including hearing-in-noise deficits, tinnitus, and hyperacusis. In animal models, changes in wideband MEMR immittance have been correlated with noise-induced synaptopathy; however, studies in humans have shown more varied results. The discrepancies observed across studies could reflect the heterogeneity of synaptopathy in humans more than the effects of parametric differences or relative sensitivity of the measurement. Whereas the etiology and degree of synaptopathy can be carefully controlled in animal models, synaptopathy in humans likely stems from multiple etiologies and thus can vary greatly across the population. Here, we explore the evolving research evidence of the MEMR response in relation to subclinical noise-induced cochlear damage and the MEMR as an early correlate of suprathreshold deficits.

FP.04 Three-year natural history study in Becker muscular dystrophy in The Netherlands

The slow and highly variable disease progression observed in BMD stresses the need to develop outcome measures for clinical trials. We evaluated the responsiveness of different assessments in a cohort of adult BMD patients followed for 3 years. We included 36 genetically confirmed BMD patients (median age at baseline 42.3 years, range 18.6-67.3) of whom 28 were ambulant at baseline (78%). We conducted ambulatory assessments (6WMT, NSAA, 10-meter walk velocity (TMWv), time to rise from floor velocity (TRFv)), PUL1.2 and bilateral maximal voluntary isometric contraction (grip, knee/hip/elbow flexion and extension). The median change and the standard response mean (SRM) at 1- and 3-year follow-up were calculated. Sample sizes (SS) were calculated assuming 50% reduction in disease progression over a 3 year clinical trial with 1:1 randomization. We observed a large variability across all measures, for example the median at baseline for the 6MWT was 439.10m (range 84.30 to 650.00), median change at 1 year follow-up -8.15 (-151.90 to 182.22) and at 3-years -14.50(-151.90 to 158.72). After 1-year follow-up, the SRM was below 0.8 for all considered outcomes. At 3-year follow-up, TMWv and TRFv showed a responsiveness with SRM above 0.8 (1.91, SS 17 and -0.90, SS 79 respectively). Three strength measurements showed SRM >0.8: right elbow flexion (SRM = -1.01, SS 62), left elbow flexion (SRM = -0.85, SS 88) and left hip flexion (SRM = -0.81, SS 96). Of the 29 patients who completed the PUL1.2 at 3rd year follow-up visit, 20 (69%) obtained the maximum score of 74 points. Only one patient lost ambulation during the study. BMD is hallmarked by large inter-individual variability at baseline and follow-up. A relatively stable disease course is common even with 3 years. The ceiling effect of the PUL1.2 illustrates the need for adequate outcome measures in non-ambulant patients.

The Relationship Between Lower Extremity Strength Ratios And Patient Reported Function After Anterior Cruciate Ligament Reconstruction

PURPOSE: Strength deficits in hip abductors and adductors, knee extension and flexion post-ACLR have been observed as potential risk factors for ACL reinjury. To holistically quantify these deficits, strength ratios can be utilized. Patient reported outcomes (PROs) help determine subjective function and can influence clinical perception of patients’ readiness to return to play. The purpose of this study was to examine the relationship between hip and thigh strength ratios to PROs post-ACLR. METHODS: In total, 146 patients with primary unilateral ACLR (76 M/70 F, 24.0 ± 10.6 yr, 172.7 ± 10.5 cm, 79.1 ± 19.1 kg, 6.6 ± 3.1 mo post-ACLR) performed maximal bilateral isometric contractions of hip abduction (AB) and adduction (AD) to assess strength via peak torque in a supine hook lying position with hips and knees flexed to 45° and 90° respectively. Peak torque during knee extension (Q) and flexion (H) was assess seated with hips and knees flexed to 90°. Peak torque ratios of AB:Q, AB:H, AD:Q, AD:H, and H:Q were calculated. PROs scores of IKDC, KOOS, and ACL-RSI were recorded. Pearson r correlation coefficients were used to assess the associations among strength ratios and PROs with α set to 0.05. RESULTS: Weak negative relationships were seen between hip:thigh strength ratios and PROs of the ACLR limb (Table 1). Correlations between AB:Q and all PROs were statistically significant with r-values between -0.2 and -0.24, except for KOOS_ADL. AB:H was only significantly correlated with KOOS_ADL (r = -0.23). No significant findings were seen between H:Q ratios and PROs of the ACLR limb, nor were any significant findings seen between any contralateral limb strength ratios and PROs. CONCLUSIONS: Patients post-ACLR displayed weak negative relationships among hip:thigh strength ratios of the ACLR limb and PROs. The lack of a relationship amid H:Q and PROs, and presence of relationships between hip:thigh and PROs highlight the influence of hip strength deficits on patient function post-ACLR.

The Influence of Maximum Strength Performance in Seated Calf Raises on Counter Movement Jump and Squat Jump in Elite Junior Basketball Players

In basketball high intensity jumping and sprinting performance is of high importance. There seems to be a relationship between maximal strength (MSt) and jumping performance in general, but influence of MSt in the plantar flexors and jumping performance seems not to be investigated very well. Thus, the aim of this study was to investigate the influence of MSt in the plantar flexors on jumping performance. 37 young elite basketball players were included (age: 13.9±1.8 years; weight: 66.4±16.8 kg; height: 179.21±13.24 cm) and countermovement jump (CMJ) and squat jump (SJ) height as well as unilateral and bilateral maximal isometric contraction in the plantar flexors with bended knee joint were assessed. Pearson correlations were calculated for MSt and jumping performance and Bland-Altman Analysis was performed to determine the level of variance between bilateral MSt assessment and cumulated MSt value of unilateral measurements. This study shows a moderate influence of isometric MSt in the calf muscle on jumping performance, so it seems beneficial to include the training of the plantar flexors in the training routine of basketball players. When determining MSt, the bilateral force deficit must be considered, even though there was no influence on determined correlations.

Differences in motor unit recruitment patterns and low frequency oscillation of discharge rates between unilateral and bilateral isometric muscle contractions.

Distinct cortical activities contribute to unilateral and bilateral motor control. However, it remains largely unknown whether the behavior of motor neurons differs between unilateral and bilateral isometric force generation. Here, we first investigated motor units (MUs) recruitment patterns during unilateral and bilateral force generation. Considering that the force control is primarily regulated by low-frequency synaptic inputs to motor neurons, we also examined the relation between MU discharge rate and force output during unilateral and bilateral muscle contractions. Using advanced electromyography (EMG) sensor arrays and spike-triggered averaging techniques, we examined a large population of MUs in the right first dorsal interosseous (FDI) muscle during unilateral and bilateral force tracking tasks. Using the principal component analysis, we analyzed the first common component (FCC) of MU discharge rate to describe the force fluctuations during unilateral and bilateral contractions. We found that MU discharge rate decreased during bilateral compared with unilateral contractions. MU recruitment threshold increased, while the amplitude and duration of MU action potential (MUAP) remained unchanged during bilateral compared with unilateral contractions. We found that the coefficients of variation (CV) for the force and FCC signal increased during bilateral compared with unilateral contractions. Notably, the FCC signal captured a great amount of MU discharge variability, and its CV correlated with the CV of the force signal. Our findings suggest that MU recruitment patterns are altered during bilateral compared with unilateral isometric force generation, likely related to changes at the low-frequency portion of the synaptic drive.

EFFECTS OF HOME-BASED ISOMETRIC HANDGRIP OR AEROBIC EXERCISE TRAINING IN OLDER ADULTS WITH PRE-HYPERTENSION AND HYPERTENSION

Objective: Isometric handgrip exercise training (IHT) is a promising non-pharmacological treatment to hypertension. In HoldAge (NCT04275037) we compared the effects of a home-based IHT intervention to home-based aerobic exercise training (AET) intervention or usual care on blood pressure (BP) in older adults with high normal BP and hypertension. Design and method: 53 participants with high normal BP to stage I hypertension were (24 men, age 71.7 ± 4.2 years, systolic BP 138.2 ± 16.2 and diastolic BP 80.4 ± 8.7 mmHg) were randomized into IHT (n = 19), AET (n = 19) or an attention control group (AC, n = 15). Participants performed IHT or AET, 3 times/week, for 8 weeks. IHT consisted of 4x45 sec bilateral contractions, at an intensity of 50% of the maximum voluntary contraction, with a 1-min rest between sets. AET was walking at an intensity of 50–70% of the estimated peak maximal oxygen consumption. The AC group received standardized optimal medical care, including lifestyle advice. Results: Of the 53 participants, 49 finished the intervention (92.5%) with one dropout in AET and 3 in AC. Three participants were excluded due to changes in the antihypertensive medication (AET:1 and AC:2). The self-reported exercise adherence was 96.6% for IHT and 83.8% for AET. There were no significant differences at baseline for SBP (p = 0.343), DBP (p = 0.107) and pulse pressure (PP, p = 0.386). Both exercise interventions elicited similar reductions in SBP from baseline to postintervention (IHT: 138.8 ± 14.9 vs 129.2 ± 10.4 mmHg; p = 0.003; AET: 139.8 ± 19.6 vs 132.6 ± 9.5 mmHg; p = 0.049). There were no changes in BP in the AC group (130.6 ± 12.7 vs 127.9 ± 18.3 mmHg; p = 0.392). DBP decreased after IHT (78.6 ± 7.9 vs 74.7 ± 8.1 mmHg; p = 0.025) but not AET (83.1 ± 9.2 vs 80.8 ± 9.5 mmHg; p = 0.360) or AC (76.5 ± 5 vs 76.5 ± 10.1 mmHg; p = 0.942). Both exercise interventions also elicited similar reductions in PP (IHT: 60.2 ± 10.5 vs 54.4 ± 8.9 mmHg; p = 0.014; AET: 56.7 ± 13.2 vs 51.7 ± 13.5 mmHg; p = 0.016) with no differences for the AC (54.1 ± 10.3 vs 51.2 ± 13.3 mmHg; p = 0.285). Conclusions: The preliminary results from HoldAge indicate home-based IHT and AET elicit significant reductions in office SBP among older adults with high-normal BP to Stage 1 hypertension.

Region-Dependent Increase of Cerebral Blood Flow During Electrically Induced Contraction of the Hindlimbs in Rats

Elevation of cerebral blood flow (CBF) may contribute to the cerebral benefits of the regular practice of physical exercise. Surprisingly, while electrically induced contraction of a large muscular mass is a potential substitute for physical exercise to improve cognition, its effect on CBF remains to be investigated. Therefore, the present study investigated CBF in the cortical area representing the hindlimb, the hippocampus and the prefrontal cortex in the same anesthetized rats subjected to either acute (30 min) or chronic (30 min for 7 days) electrically induced bilateral hindlimb contraction. While CBF in the cortical area representing the hindlimb was assessed from both laser doppler flowmetry (LDFCBF) and changes in p-eNOSSer1177 levels (p-eNOSCBF), CBF was evaluated only from changes in p-eNOSSer1177 levels in the hippocampus and the prefrontal cortex. The contribution of increased cardiac output and increased neuronal activity to CBF changes were examined. Stimulation was associated with tachycardia and no change in arterial blood pressure. It increased LDFCBF with a time- and intensity-dependent manner as well as p-eNOSCBF in the area representing the hindlimb. By contrast, p-eNOSCBF was unchanged in the two other regions. The augmentation of LDFCBF was partially reduced by atenolol (a ß1 receptor antagonist) and not reproduced by the administration of dobutamine (a ß1 receptor agonist). Levels of c-fos as a marker of neuronal activation selectively increased in the area representing the hindlimb. In conclusion, electrically induced bilateral hindlimb contraction selectively increased CBF in the cortical area representing the stimulated muscles as a result of neuronal hyperactivity and increased cardiac output. The absence of CBF changes in cognition-related brain regions does not support flow-dependent neuroplasticity in the pro-cognitive effect of electrically induced contraction of a large muscular mass.

Quadriceps Muscle Fatigue Reduces Extension and Flexion Power During Maximal Cycling.

Purpose: To investigate how quadriceps muscle fatigue affects power production over the extension and flexion phases and muscle activation during maximal cycling.Methods: Ten participants performed 10-s maximal cycling efforts without fatigue and after 120 bilateral maximal concentric contractions of the quadriceps muscles. Extension power, flexion power and electromyographic (EMG) activity were compared between maximal cycling trials. We also investigated the associations between changes in quadriceps force during isometric maximal voluntary contractions (IMVC) and power output (flexion and extension) during maximal cycling, in addition to inter-individual variability in muscle activation and pedal force profiles.Results: Quadriceps IMVC (−52 ± 21%, P = 0.002), voluntary activation (−24 ± 14%, P < 0.001) and resting twitch amplitude (−45 ± 19%, P = 0.002) were reduced following the fatiguing task, whereas vastus lateralis (P = 0.58) and vastus medialis (P = 0.15) M-wave amplitudes were unchanged. The reductions in extension power (−15 ± 8%, P < 0.001) and flexion power (−24 ± 18%, P < 0.001) recorded during maximal cycling with fatigue of the quadriceps were dissociated from the decreases in quadriceps IMVC. Peak EMG decreased across all muscles while inter-individual variability in pedal force and EMG profiles increased during maximal cycling with quadriceps fatigue.Conclusion: Quadriceps fatigue induced by voluntary contractions led to reduced activation of all lower limb muscles, increased inter-individual variability and decreased power production during maximal cycling. Interestingly, power production was further reduced over the flexion phase (24%) than the extension phase (15%), likely due to larger levels of peripheral fatigue developed in RF muscle and/or a higher contribution of the quadriceps muscle to flexion power production compared to extension power during maximal cycling.

New fixed-disc results via bilateral type contractions on S-metric spaces

There are some examples of self-mappings which does not satisfy the Banach contractive condition and have a unique fixed point or more than one fixed point. In this case, metric fixed-point theory has been extensively generalized using some techniques. One of these techniques is to generalize the used contractive conditions such as the Jaggi type contractive condition, the Dass-Gupta type contractive condition etc. Another technique is to generalize the used metric spaces such as a b-metric space, an S-metric space etc. The last technique is to investigate geometric properties of the fixed-point set of a given self-mapping such as fixed circle, fixed disc etc. For this purpose, “fixed-circle problem” has been studied with various techniques as a geometrical generalization of the metric fixed-point theory. This problem was also considered as “fixed-figure problem”. Some solutions to these recent problems were obtained using different contractions both a metric space and a generalized metric space. The main purpose of this paper is to prove some fixed-disc theorems on an S-metric space. To do this, we modify the known contractive conditions. Also, the obtained new theorems are supported by some illustrative examples.