Bumetanide induces post-traumatic microglia-interneuron contact to promote neurogenesis and recovery.

Although the Na-K-Cl cotransporter (NKCC1) inhibitor bumetanide has prominent positive effects on the pathophysiology of many neurological disorders, the mechanism of action is obscure. Attention paid to elucidating the role of Nkcc1 has mainly been focused on neurons, but recent single cell mRNA sequencing analysis has demonstrated that the major cellular populations expressing NKCC1 in the cortex are non-neuronal. We used a combination of conditional transgenic animals, in vivo electrophysiology, two-photon imaging, cognitive behavioural tests and flow cytometry to investigate the role of Nkcc1 inhibition by bumetanide in a mouse model of controlled cortical impact (CCI). Here, we found that bumetanide rescues parvalbumin-positive interneurons by increasing interneuron-microglia contacts shortly after injury. The longitudinal phenotypic changes in microglia were significantly modified by bumetanide, including an increase in the expression of microglial-derived BDNF. These effects were accompanied by the prevention of CCI-induced decrease in hippocampal neurogenesis. Treatment with bumetanide during the first week post-CCI resulted in significant recovery of working and episodic memory as well as changes in theta band oscillations 1 month later. These results disclose a novel mechanism for the neuroprotective action of bumetanide mediated by an acceleration of microglial activation dynamics that leads to an increase in parvalbumin interneuron survival following CCI, possibly resulting from increased microglial BDNF expression and contact with interneurons. Salvage of interneurons may normalize ambient GABA, resulting in the preservation of adult neurogenesis processes as well as contributing to bumetanide-mediated improvement of cognitive performance.

Time-dependent cortical plasticity during moderate-intensity continuous training versus high-intensity interval training in rats.

The temporal pattern of cortical plasticity induced by high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) is required to clarify their relative benefits to prevent neurological disorders. The purpose of this study is to define the time-dependent effects of work-matched HIIT and MICT on cortical plasticity, endurance, and sensorimotor performances over an 8-week training period in healthy rats. Adult healthy rats performed incremental exercise tests and sensorimotor tests before and at 2, 4, and 8 weeks of training. In parallel, cortical markers related to neurotrophic, angiogenic, and metabolic activities were assessed. Results indicate that HIIT induced an early and superior endurance improvement compared to MICT. We found significant enhancement of speed associated with lactate threshold (SLT) and maximal speed (Smax) in HIIT animals. MICT promoted an early increase in brain-derived neurotrophic factor and angiogenic/metabolic markers but showed less influence at 8 weeks. HIIT upregulated the insulin-like growth factor-1 (IGF-1) as well as neurotrophic, metabolic/angiogenic markers at 2 and 8 weeks and downregulated the neuronal K-Cl cotransporter KCC2 that regulates GABAA-mediated transmission. HIIT and MICT are effective in a time-dependent manner suggesting a complementary effect that might be useful in physical exercise guidelines for maintaining brain health.

Current perspectives on mitochondrial dysfunction in migraine.

Mitochondria are an autonomous organelle that plays a crucial role in the metabolic aspects of a cell. Cortical spreading depression (CSD) and fluctuations in the cerebral blood flow have for long been mechanisms underlying migraine. It is a neurovascular disorder with a unilateral manifestation of disturbing, throbbing and pulsating head pain. Migraine affects 2.6% and 21.7% of the general population and is the major cause of partial disability in the age group 15-49. Higher mutation rates, imbalance in concentration of physiologically relevant molecules and oxidative stress biomarkers have been the main themes of discussion in determining the role of mitochondrial disability in migraine. The correlation of migraine with other disorders like hemiplegic migraine; mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes [MELAS]; tension-type headache (TTH); cyclic vomiting syndrome (CVS), ischaemic stroke; and hypertension has helped in the assessment of the physiological and morphogenetic basis of migraine. Here, we have reviewed the different nuances of mitochondrial dysfunction and migraine. The different mtDNA polymorphisms that can affect the generation and transmission of nerve impulse has been highlighted and supported with research findings. In addition to this, the genetic basis of migraine pathogenesis as a consequence of mutations in nuclear DNA that can, in turn, affect the synthesis of defective mitochondrial proteins is discussed along with a brief overview of epigenetic profile. This review gives an overview of the pathophysiology of migraine and explores mitochondrial dysfunction as a potential underlying mechanism. Also, therapeutic supplements for managing migraine have been discussed at different junctures in this paper.

Effects of Different High-Intensity Interval Training Regimens on Endurance and Neuroplasticity After Cerebral Ischemia.

BACKGROUND AND PURPOSE: The objective is to compare the effects of high-intensity interval training (HIIT) with long versus short intervals on endurance and motor performance. Their influence on neuroplasticity markers is assessed in the ipsilesional and contralesional cortex and hippocampus since their remodeling could improve functional recovery. METHODS: Rats performed work-matched HIIT4 (long intervals: 4 minutes) or HIIT1 (short intervals: 1 minute) on treadmill for 2 weeks following transient middle cerebral artery occlusion. Forelimb grip strength evaluated motor function while incremental exercise tests measured the endurance performance. Key neuroplasticity markers were assessed by Western blot. RESULTS: Both regimens were effective in enhancing both the speed associated with the lactate threshold and maximal speed at D8 and D15. Neuroplasticity markers were upregulated in the contralesional hemisphere after training contrary to the ipsilesional side. Grip strength completely recovered but is faster with HIIT4. CONCLUSIONS: HIIT with short and long intervals induced early aerobic fitness and grip strength improvements. Our findings revealed that neuroplasticity markers were upregulated in the contralesional cortex and hippocampus to promote functional recovery.

Is High-Intensity Interval Training Suitable to Promote Neuroplasticity and Cognitive Functions after Stroke?

Stroke-induced cognitive impairments affect the long-term quality of life. High-intensity interval training (HIIT) is now considered a promising strategy to enhance cognitive functions. This review is designed to examine the role of HIIT in promoting neuroplasticity processes and/or cognitive functions after stroke. The various methodological limitations related to the clinical relevance of studies on the exercise recommendations in individuals with stroke are first discussed. Then, the relevance of HIIT in improving neurotrophic factors expression, neurogenesis and synaptic plasticity is debated in both stroke and healthy individuals (humans and rodents). Moreover, HIIT may have a preventive role on stroke severity, as found in rodents. The potential role of HIIT in stroke rehabilitation is reinforced by findings showing its powerful neurogenic effect that might potentiate cognitive benefits induced by cognitive tasks. In addition, the clinical role of neuroplasticity observed in each hemisphere needs to be clarified by coupling more frequently to cellular/molecular measurements and behavioral testing.

Degradable and Injectable Hydrogel for Drug Delivery in Soft Tissues.

Injectable hydrogels are promising platforms for tissue engineering and local drug delivery as they allow minimal invasiveness. We have here developed an injectable and biodegradable hydrogel based on an amphiphilic PNIPAAm- b-PLA- b-PEG- b-PLA- b-PNIPAAm pentablock copolymer synthesized by ring-opening polymerization/nitroxide-mediated polymerization (ROP/NMP) combination. The hydrogel formation at around 30 °C was demonstrated to be mediated by intermicellar bridging through the PEG central block. Such a result was particularly highlighted by the inability of a PEG- b-PLA- b-PNIPAAm triblock analog of the same composition to gelify. The hydrogels degraded through hydrolysis of the PLA esters until complete mass loss due to the diffusion of the recovered PEG and PNIPAAm/micelle based residues in the solution. Interestingly, hydrophobic molecules such as riluzole (neuroprotective drug) or cyanine 5.5 (imaging probe) could be easily loaded in the hydrogels' micelle cores by mixing them with the copolymer solution at room temperature. Drug release was correlated to polymer mass loss. The hydrogel was shown to be cytocompatible (neuronal cells, in vitro) and injectable through a small-gauge needle (in vivo in rats). Thus, this hydrogel platform displays highly attractive features for use in brain/soft tissue engineering as well as in drug delivery.

Effects of High- Versus Moderate-Intensity Training on Neuroplasticity and Functional Recovery After Focal Ischemia.

BACKGROUND AND PURPOSE: This study was designed to compare the effects of high-intensity interval training (HIT) and moderate-intensity aerobic training (MOD) on functional recovery and cerebral plasticity during the first 2 weeks after cerebral ischemia. METHODS: Rats were randomized as follows: control (n=15), SHAM (n=9), middle cerebral artery occlusion (n=13), middle cerebral artery occlusion at day 1 (n=7), MOD (n=13), and HIT (n=13). Incremental tests were performed at day 1 (D1) and 14 (D14) to identify the running speed associated with the lactate threshold (SLT) and the maximal speed (Smax). Functional tests were performed at D1, D7, and D14. Microglia form, cytokines, p75NTR (pan-neurotrophin receptor p75), potassium-chloride cotransporter type 2, and sodium-potassium-chloride cotransporter type 1 expression were made at D15. RESULTS: HIT was more effective to improve the endurance performance than MOD and induced a fast recovery of the impaired forelimb grip force. The ionized calcium binding adaptor molecule 1 (Iba-1)-positive cells with amoeboid form and the pro- and anti-inflammatory cytokine expression were lower in HIT group, mainly in the ipsilesional hemisphere. A p75NTR overexpression is observed on the ipsilesional side together with a restored sodium-potassium-chloride cotransporter type 1/potassium-chloride cotransporter type 2 ratio on the contralesional side. CONCLUSIONS: Low-volume HIT based on lactate threshold seems to be more effective after cerebral ischemia than work-matched MOD to improve aerobic fitness and grip strength and might promote cerebral plasticity.

A scale-based approach to interdisciplinary research and expertise in sports.

After more than 20 years since the introduction of ecological and dynamical approaches in sports research, their promising opportunity for interdisciplinary research has not been fulfilled yet. The complexity of the research process and the theoretical and empirical difficulties associated with an integrated ecological-dynamical approach have been the major factors hindering the generalisation of interdisciplinary projects in sports sciences. To facilitate this generalisation, we integrate the major concepts from the ecological and dynamical approaches to study behaviour as a multi-scale process. Our integration gravitates around the distinction between functional (ecological) and execution (organic) scales, and their reciprocal intra- and inter-scale constraints. We propose an (epistemological) scale-based definition of constraints that accounts for the concept of synergies as emergent coordinative structures. To illustrate how we can operationalise the notion of multi-scale synergies we use an interdisciplinary model of locomotor pointing. To conclude, we show the value of this approach for interdisciplinary research in sport sciences, as we discuss two examples of task-specific dimensionality reduction techniques in the context of an ongoing project that aims to unveil the determinants of expertise in basketball free throw shooting. These techniques provide relevant empirical evidence to help bootstrap the challenging modelling efforts required in sport sciences.

Physical Exercise as a Diagnostic, Rehabilitation, and Preventive Tool: Influence on Neuroplasticity and Motor Recovery after Stroke.

Stroke remains a leading cause of adult motor disabilities in the world and accounts for the greatest number of hospitalizations for neurological disease. Stroke treatments/therapies need to promote neuroplasticity to improve motor function. Physical exercise is considered as a major candidate for ultimately promoting neural plasticity and could be used for different purposes in human and animal experiments. First, acute exercise could be used as a diagnostic tool to understand new neural mechanisms underlying stroke physiopathology. Indeed, better knowledge of stroke mechanisms that affect movements is crucial for enhancing treatment/rehabilitation effectiveness. Secondly, it is well established that physical exercise training is advised as an effective rehabilitation tool. Indeed, it reduces inflammatory processes and apoptotic marker expression, promotes brain angiogenesis and expression of some growth factors, and improves the activation of affected muscles during exercise. Nevertheless, exercise training might also aggravate sensorimotor deficits and brain injury depending on the chosen exercise parameters. For the last few years, physical training has been combined with pharmacological treatments to accentuate and/or accelerate beneficial neural and motor effects. Finally, physical exercise might also be considered as a major nonpharmacological preventive strategy that provides neuroprotective effects reducing adverse effects of brain ischemia. Therefore, prestroke regular physical activity may also decrease the motor outcome severity of stroke.

Comparison of a collagen membrane versus a fibrin sealant after a peroneal nerve section and repair: a functional and histological study.

BACKGROUND: To date, fibrin sealant is considered to be one of the most effective substitutes to prevent post-operative fibrosis and to limit neuroma formation after nerve suture. Because fibrin sealant presents a number of drawbacks, more suitable techniques should be considered. The aim of this study was to functionally and histologically compare the efficiency of a fibrin sealant to a resorbable semi-permeable porcine type I collagen membrane after a peroneal nerve lesion and repair on rats. METHODS: Rats were divided into four groups: (1) a SHAM group (n = 10) in which surgery was performed without damaging the nerve, (2) a LESION group (n = 15) in which the nerve was cut and immediately sutured without additional treatment, (3) a MEMBRANE group (n = 30) in which a collagen membrane was wrapped around the lesion site, and (4) a GLUE group (n = 30) in which the peroneal nerve was coated by fibrin sealant. Peroneal Functional Index (PFI), kinematic analysis of locomotion, muscular atrophy, axonal regrowth, and irritant ranking score (IRS) were performed during three months post-surgery. RESULTS: Our results indicate that at the third month post-surgery, no difference in both the functional recovery and the histological measurement was observed between groups. However, no deleterious effect was observed following the use of the collagen membrane. Indeed, the porcine membrane was well-integrated into the host tissue, with no noticeable foreign body reaction at three months post-surgery. CONCLUSION: Our preliminary results highlight the fact that the collagen membrane could be used as an alternative to fibrin sealant in peripheral nerve repair surgery. Indeed, animals in which the collagen membrane was used to wrap the lesion site exhibited similar functional and histological results as animals in which a fibrin sealant was used to coat the lesion. The greatest advantage of this membrane is that it could be used as a drug delivery device, regulated by its degradation rate.

Functional recovery after repair of peroneal nerve gap using different collagen conduits.

BACKGROUND: Currently, autologous nerve implantation to bridge a long nerve gap presents the greatest regenerative performance in spite of substantial drawbacks. In this study, we evaluate the effect of two different collagen conduits bridging a peroneal nerve gap. METHODS: Rats were divided into four groups: (1) the gold standard group, in which a 10-mm-long nerve segment was cut, reversed, and reimplanted between the nerve stumps; (2) the CG-I/III group, in which a type I/III collagen conduit bridged the gap; (3) the CG-I, in which a type I collagen conduit was grafted; and (4) the sham group, in which a surgery was performed without injuring the nerve. Peroneal Functional Index and kinematics analysis of locomotion were performed weekly during the 12 weeks post-surgery. At the end of the protocol, additional electrophysiological tests, muscular weight measurements, axon counting, and g-ratio analysis were carried out. RESULTS: Functional loss followed by incomplete recovery was observed in animals grafted with collagen conduits. At 12 weeks post-surgery, the ventilatory rate of the CG-I group in response to exercise was similar to the sham group, contrary to the CG-I/III group. After KCl injections, an increase in metabosensitive afferent-fiber activity was recorded, but the response stayed incomplete for the collagen groups compared to the sham group. Furthermore, the CG-I group presented a higher number of axons and seemed to induce a greater axonal maturity compared to the CG-I/III group. CONCLUSIONS: Our results suggest that the grafting of a type I collagen conduit may present slight better prospects than a type I/III collagen conduit.

Is an 8-Week Regimen of Nordic Walking Training Sufficient to Benefit Cognitive Performance in Healthy Older Adults? A Pilot Study.

Nordic walking requires the association of walking and coordination of limbs while orienteering in a natural environment. It has been shown to improve functional capacities more than normal walking. However, its cognitive benefits are less clear. The main hypothesis was that this training improves visuospatial capacities and inhibition functions. A total of 14 healthy older adults were included. The training was performed in three sessions of 75 min a week for 8 weeks. Pre-, intermediate, and post-tests were carried out. Cognitive functions including global cognition (MoCA), executive functions (Color-Word Stroop test), speed of information processing, switching capacities (Trail Making Test A and B), and visuospatial capacities (Rey Complex Figure Copy Task) were assessed. Motor functions including balance control (Unipedal Balance Test), functional mobility (Timed Up and Go), hamstring flexibility (Chair Sit and Reach test), and motor coordination (Four-Square Stepping Test) were evaluated. Physical function, including lower limb strength (Timed Sit-To-Stand) and cardiovascular capacities (Incremental Shuttle Walking Test), was measured. Cardiovascular capacity, strength of lower limbs, and motor coordination were positively affected by training. With respect to cognition, training improved visuospatial capacities, while switching capacities, information processing speed, and executive functions did not improve. A possible explanation is that they needed a longer program duration to show benefits. However, analyses of responders suggested that NW positively affected cognitive functioning in a subset of participants. Eight weeks of NW training produced physical, motor, and cognitive improvements. A longer training duration could be necessary to extend the benefits to executive functions in all participants.

In vivo short TE localized 1H MR spectroscopy of mouse cervical spinal cord at very high magnetic field (11.75 T).

MR spectroscopy allows a noninvasive assessment of metabolic information in healthy and pathological central nervous system. Whereas MR spectroscopy has been extensively applied in the brain, only few spectroscopic studies of the spinal cord (SC) have been performed so far. For mice, due to additional technical challenges, in vivo 1H SC MRS has not yet been reported. In this work, the feasibility of short echo time localized proton magnetic resonance spectroscopy using Point RESolved Spectroscopy sequence for the examination of mouse cervical SC at 11.75 T is presented. Several optimizations were performed to improve the static field homogeneity, to reduce physiological motion effects and lipid contaminations arising from SC surrounding tissues, and to provide a careful metabolic quantification. Satisfactory spectrum quality was obtained. The described protocol allowed reliable quantification of five metabolites in the cervical SC. The mean reproducibility regarding the quantification of tNAA, tCr and tCho was ≥80%, >70% for mI and >55% for Glu, whereas the intersubject variabilities were ≤21%. The application of this protocol to transgenic mouse models in pathological conditions such as SC injury or neurodegenerative diseases may thus provide complementary information to MRI and increase our understanding of such pathologies.

High-intensity training with short and long intervals regulate cortical neurotrophic factors, apoptosis markers and chloride homeostasis in rats with stroke.

BACKGROUND/PURPOSE: The optimal endurance exercise parameters remain to be defined to potentiate long-term functional recovery after stroke. We aim to assess the effects of individualized high-intensity interval training (HIIT) with either long or short intervals on neurotrophic factors and their receptors, apoptosis markers and the two-main cation-chloride cotransporters in the ipsi- and contralesional cerebral cortices in rats with cerebral ischemia. Endurance performance and sensorimotor functions were also assessed METHODS: Rats with a 2 h transient middle cerebral artery occlusion (tMCAO) performed work-matched HIIT4 (intervals: 4 min) or HIIT1 (intervals: 1 min) on treadmill for 2 weeks. Incremental exercises and sensorimotor tests were performed at day 1 (D1), D8, and D15 after tMCAO. Molecular analyses were achieved in both the paretic and non-paretic triceps brachii muscles and the ipsi- and contralesional cortices at D17 RESULTS: Gains in endurance performance are in a time-dependent manner from the first week of training. This enhancement is supported by the upregulation of metabolic markers in both triceps brachii muscles. Both regimens alter the expression of neurotrophic markers and chloride homeostasis in a specific manner in the ipsi- and contralesional cortices. HIIT acts on apoptosis markers by promoting anti-apoptotic proteins in the ipsilesional cortex CONCLUSION: HIIT regimens seem to be of clinical relevance in the critical period of stroke rehabilitation by strongly improving aerobic performance. Also, the observed cortical changes suggest an influence of HIIT on neuroplasticity in both ipsi- and contralesional hemispheres. Such neurotrophic markers might be considered as biomarkers of functional recovery in individuals with stroke.

Comparison of Three Physical-Cognitive Training Programs in Healthy Older Adults: A Study Protocol for a Monocentric Randomized Trial.

(1) Combining aerobic, coordination and cognitive training allows for more improved physical and cognitive performance than when performed separately. A Nordic walking (NW) and two cognitive-motor circuit training programs (CT-c and CT-fit) are compared. CT-c and CT-fit stimulate cognition differently: CT-c, is through conventional complex coordination training performed in single and dual-task conditions; CT-fit, incorporates it into complex goal-directed actions, implemented by fitness gaming technology (2) The aim is to determine whether CT-fit brings additional benefits to cognition compared to more traditional training. (3) Forty-five healthy independent living community dwellers participants (65-80 years) will be included after a general medical examination. The main exclusion criteria are signs of cognitive impairments (Mini-Mental State Examination < 26/30) and physical impairments. Pre and post-tests will be performed to assess: cognitive functions (Montreal Cognitive Assessment; Trail Making Test; Stroop task, working memory test, Rey Complex Figure copy task, Oral Trail Making Test, and dual-task); motor fitness (Bipedal and unipedal balance test, gait assessments, Time Up and Go, chair sit and reach test and four-square stepping test); and physical fitness (10 m incremental shuttle walking test, maximal handgrip force, Timed-Stands test). (4) Incorporating cognitive demands into complex, goal-directed actions using fitness gaming technology should be the best solution to optimize training benefits.

High-intensity interval training is superior to moderate intensity training on aerobic capacity in rats: Impact on hippocampal plasticity markers.

The use of endurance regimens could be improved by defining their respective effectiveness on aerobic fitness and brain health that remains controversial. We aimed at comparing work-matched high-intensity interval training (HIIT) with moderate-intensity continuous training (MICT) on aerobic performance and muscular plasticity markers in healthy rats. Cognitive functions and brain plasticity markers were also investigated following the 8-week training. Rats performed the incremental exercise test and behavioural tests before and after training at day 1 (D1), D15, D29 and D57. Key cerebral markers were assessed by Western blot and quantitative polymerase chain reaction to provide information on brain function related to angiogenesis, aerobic metabolism and neurotrophin activity at D59. Muscular protein levels involved in angiogenesis and aerobic metabolism were measured in both triceps brachii and soleus muscles. HIIT induced superior improvement of aerobic fitness compared to MICT, as indicated by enhancement of speed associated with lactate threshold (SLT) and maximal speed (Smax). In the triceps brachii muscle, markers of angiogenesis and aerobic activity were upregulated as well as myokines involved in neuroplasticity. Moreover, levels of key brain plasticity markers increased in the hippocampus after 8 weeks of HIIT, without improving cognitive functions. These findings might contribute to define physical exercise guidelines for maintaining brain health by highlighting the promising role of HIIT when using SLT for distinguishing low running speed from high running speed. Further studies are required to confirm these brain effects by exploring synaptic plasticity and neurogenesis mechanisms when exercise intensity is standardized and individualized.

Modulation of the spinal excitability by muscle metabosensitive afferent fibers.

The aim of this study was to identify the effect of chemical activation of muscle metabosensitive afferent fibers from groups III and IV on Hoffmann (H-) reflex modulation in the vastus medialis muscle. The experiment was conducted in rats and was divided into two experiments. The first experiment consisted of recording the metabosensitive afferent activity from femoral nerve in rats in response to KCl intraarterial injections in nontreated adults and adults treated neonatally with capsaicin. Thus, the dose-response curve was determined. The second experiment consisted of eliciting the H- and M-waves before and after KCl injection in nontreated adult animals and those treated neonatally with capsaicin. Thus, the H(max)/M(max) ratio was measured. Results indicated that, 1) in nontreated animals, afferent fibers peak discharge was found after 10 mM KCl injection; 2) no significant increase in afferent discharge rate was found in capsaicin-treated animal after KCl injections, confirming that capsaicin is an excitotoxic agent that had destroyed the thin metabosensitive nerve fibers; 3) in nontreated animals, H(max)/M(max) ratio was significantly attenuated after a 10 mM KCl injection activating metabosensitive afferent fibers; and 4) in capsaicin-treated animals, no significant change in H(max)/M(max) ratio was observed after the KCl injection. These results reinforce the hypothesis that the spinal reflex response was influenced by metabosensitive muscle fibers and provide direct evidence that activation of these fibers could partially explain the reported decrease in H-reflex when metabolites are released in muscle.

Neuromuscular recovery pattern after medial collateral ligament disruption in rats.

The medial collateral ligament (MCL) is one of the most injured ligaments during sport activities. The resulting joint damage effects on neuromuscular system remain unclear. Thus this study was designed to assess the changes in neuromuscular properties of vastus medialis muscle after MCL transection. Complete rupture of MCL was performed on rats, and dynamic functional assessment during locomotion was achieved before and once a week from 1-5 wk postlesion. Twitch properties and metabo- and mechanosensitive afferent fiber responses to specific stimuli were measured 1, 3, and 5 wk after MCL transection. Results indicated that maximum knee angle measured during the stance phase of the gait cycle was decreased during 3 wk after MCL injury and then recovered. Minimum knee angle measured during the stance phase was decreased during 2 wk and showed compensatory effects at week 5. A stepwise decrease in maximum relaxation rate-to-amplitude ratio concomitant with a stepwise increase in half-relaxation time were observed following MCL injury. Variations in metabosensitive afferent response to chemical (KCl and lactic acid) injections were decreased at week 1 and recovered progressively from week 3 to week 5 postlesion. Recovery of the mechanosensitive afferent response to vibrations was not totally complete after 5 wk. Our data indicate that alteration of the sensory pathways from the vastus medialis muscle could be considered as a source of neuromuscular deficits following MCL transection. Our results should be helpful in clinical purpose to improve the knowledge of the influence exerted by ligament rupture on the motor system and permit development of rehabilitation protocols and exercises more appropriate for recovery of functional stability.

Group III and IV muscle afferent discharge patterns after repeated lengthening and shortening actions.

The purpose of this study was to test the hypothesis that group III and IV muscle afferent activity would differ after concentric- and eccentric-type fatiguing tasks. Tibialis anterior afferent activities from adult rats were measured in three conditions: before and after a rest period (C), and after concentric (CC) or eccentric (EC) exercise. Specific activators were used to elicit increases in afferent discharge rates, i.e., electrically induced fatigue (EIF), or potassium chloride (KCl) and lactic acid (LA) injections. After the rest period (POST-condition), the control group displayed a pattern of response to stimuli similar to that obtained in baseline condition (PRE-condition). However, responses were significantly different in the exercise groups: afferent responses were blunted in the CC group and were almost suppressed in the EC group. These results demonstrate that the type of muscular contraction involved in the fatiguing task can affect group III and IV afferent fiber activity differently and, potentially, can differentially affect the regulation of central motor command.

Cognitive functioning enhancement in older adults: is there an advantage of multicomponent training over Nordic walking?

INTRODUCTION: We compared Nordic walking training (NW) to a multicomponent training (MCT) program of an equivalent intensity, in older adults. Our main hypothesis was that MCT would result in larger effects on cognitive processes than NW. METHODS: Thirty-nine healthy older adults, divided into two groups (NW and MCT), took part in the study (17 males, 22 females, mean age =70.8±0.8 years). They were tested for cardiovascular fitness, motor fitness and cognitive performance during the two weeks preceding and following the 12-week training session (3 times/week), respectively. For both the NW and MCT interventions, the training sessions were supervised by a trainer. Heart rate of participants was monitored during the sessions and then used to make training loads as similar as possible between the two groups (TRaining IMPulse method). RESULTS: Results showed that training resulted in better performance for cardiovascular and motor fitness tests. Among these tests, only two revealed a significant difference between the two groups. The NW group progressed more than the MCT group in the 30 Seconds Chair Stand test, while in the One Leg Stance test, the MCT group progressed more. For the cognitive assessment, a significant effect of training was found for executive functions, spatial memory score, and information processing speed response time, with no differences between the two groups. CONCLUSION: The study confirmed that physical exercise has a positive impact on cognitive processes with no advantage of MCT intervention over NW training. A possible reason is that NW intervention not only improved cardiovascular capacities, but also motor fitness, including coordination capacities.