Neuromuscular electrical stimulation at submaximal intensity combined with motor imagery increases corticospinal excitability.

PURPOSE: There is sparse evidence in the literature that the combination of neuromuscular electrical stimulation (NMES) and motor imagery (MI) can increase corticospinal excitability more that the application of one or the other modality alone. However, the NMES intensity usually employed was below or at motor threshold, not allowing a proper activation of the whole neuromuscular system. This questions the effect of combined MI + NMES with higher intensities, closer to those used in clinical settings. The purpose here was to assess corticospinal excitability during either MI, NMES or a combination of both at different evoked forces. METHODS: Seventeen healthy participants were enrolled in one session consisting of 6 conditions targeting flexor carpi radialis muscle (FCR): rest, MI, NMES at 5% and 20% of maximal voluntary contraction (MVC) and MI and NMES performed simultaneously (MI + NMES). During each condition, corticospinal excitability was assessed by evoking MEP of FCR by using transcranial magnetic stimulation. Maximal M-wave (Mmax) was measured by using the stimulation of the median nerve. RESULTS: MEPs during MI were greater as compared to rest (P = 0.005). MEPs during MI were significantly lower than during MI + NMES at 5% (P = 0.02) and 20% (P = 0.001). Then, MEPs during NMES 5% was significantly lower than during MI + NMES 20% (P < 0.005). CONCLUSION: The present study showed that MI + NMES increased corticospinal excitability more than MI alone. However, corticospinal excitability was not higher as the intensity increase during MI + NMES. Therefore, MI + NMES targeting FCR may not significantly increase the corticospinal excitability between different low-submaximal contractions intensities.

Influence of stimulation parameters on torque development during the combined application of electrical nerve stimulation and muscle lengthening.

This study investigated the influence of stimulation parameters on torque production when combining a brief muscle lengthening with electrical stimulation. Fifteen volunteers participated in one experimental session where two distinct stimulation modalities were compared: wide-pulse high-frequency (WPHF, pulse duration: 1ms, frequency: 100Hz), favouring afferent pathways activation, and narrow-pulse low-frequency (NPLF, pulse duration: 0.05ms, frequency: 20Hz), favouring activation of the efferent pathway. Both stimulation modalities, were applied to evoke 5-10% of maximal voluntary contraction either in isometric conditions (WPHF and NPLF) or in combination with a muscle lengthening (lengthening condition: WPHF+LEN and NPLF+LEN). The torque-time integral (TTI) during the stimulation trains and the muscle activity after the cessation of the stimulation trains (sustained EMG activity, normalized to the maximal EMG activity) were assessed and compared between the stimulation modalities and the conditions (two-way ANOVA). An interaction effect was obtained, revealing significant differences in TTI and sustained EMG activity between the WPHF+LEN and the other tested conditions (P=0.048 and P=0.044, respectively). TTI and sustained EMG activity were higher for WPHF+LEN (228.4±105.3 Nm.s and 0.085±0.070, respectively) compared to WPHF (168.4±72.9 Nm.s; 0.052±0.026), NPLF+LEN (136.4±38.9 Nm.s; 0.031±0.016) and NPLF (125.2±36.1 Nm.s; 0.028±0.015). The increased TTI during the WPHF+LEN condition suggests that the contribution of afferent pathways to the evoked torque can be enhanced with the muscle lengthening superimposition. They highlight the importance of using WPHF stimulation that already solicits Ia afferents to benefit from the cumulative afferent activation induced by the muscle lengthening to further increase torque production.

Acute effects of local vibration inducing tonic vibration reflex or illusion of movement on maximal wrist force production.

Local vibration (LV) mainly stimulates primary afferents (Ia) and can induce a tonic vibration reflex (TVR) and an illusion of movement. This study aimed to evaluate the effect of these two phenomena on maximal voluntary isometric contraction (MVIC) capacity. LV (80 Hz) was applied to the wrist flexor muscles in two randomized experiments for 6 min. LV conditions were adjusted to promote either TVR (visual focus on the vibrated wrist) or ILLUSION [hand hidden, visual focus on electromyographic activity of the flexor carpi radialis muscle (FCR)]. Mechanical and electromyographic (EMG) responses of the FCR and extensor carpi radialis muscles were recorded during MVIC in flexion and extension and during electrically evoked contractions at supramaximal intensity. Measurements were performed before (10 min and just before) and after (0 and 30 min) LV protocol. An increase in FCR EMG was observed during LV in the TVR condition (+340%) compared with the illusion condition (P = 0.003). In contrast, the movement illusion was greater in the ILLUSION condition (assessed through subjective scales) (P = 0.004). MVIC was reduced in flexion only after the TVR condition ([Formula: see text], all P < 0.034). Moreover, the decrease in force was correlated with the amount of TVR recorded on the FCR muscle (r = -0.64, P = 0.005). Although potentiated doublets of each muscle did not evolve differently between conditions, a decrease was observed between the first and the last measure. In conclusion, when conducting research to assess maximal strength, it is necessary to have better control and reporting of the phenomena induced during LV.NEW & NOTEWORTHY The maximal force production of the vibrated muscle is reduced after 6 min of LV only in TVR condition. Furthermore, the amount of TVR is negatively correlated with this force decrease. When measuring the effects of LV on maximal force production, it is important to control and report any phenomena induced during vibration, such as TVR or movement illusion, which can be achieved by recording EMG activity of vibrated muscle and quantifying illusion.

Understanding Antidiabetic Potential of Oligosaccharides from Red Alga Dulse Devaleraea inkyuleei Xylan by Investigating α-Amylase and α-Glucosidase Inhibition.

In this study, the α-glucosidase (maltase-glucoamylase: MGAM) and α-amylase inhibitory properties elicited by xylooligosaccharides (XOSs) prepared from dulse xylan were analysed as a potential mechanism to control postprandial hyperglycaemia for type-2 diabetes prevention and treatment. Xylan was purified from red alga dulse powder and used for enzymatic hydrolysis using Sucrase X to produce XOSs. Fractionation of XOSs produced xylobiose (X2), ß-(1→3)-xylosyl xylobiose (DX3), xylotriose (X3), ß-(1→3)-xylosyl-xylotriose (DX4), and a dulse XOS mixture with n ≥ 4 xylose units (DXM). The different fractions exhibited moderate MGAM (IC50 = 11.41-23.44 mg/mL) and α-amylase (IC50 = 18.07-53.04 mg/mL) inhibitory activity, which was lower than that of acarbose. Kinetics studies revealed that XOSs bound to the active site of carbohydrate digestive enzymes, limiting access to the substrate by competitive inhibition. A molecular docking analysis of XOSs with MGAM and α-amylase clearly showed moderate strength of interactions, both hydrogen bonds and non-bonded contacts, at the active site of the enzymes. Overall, XOSs from dulse could prevent postprandial hyperglycaemia as functional food by a usual and continuous consumption.

Protein hydrolysates of Moringa oleifera seed: Antioxidant and antihyperglycaemic potential as ingredient for the management of type-2 diabetes.

New plant proteins with high nutritional quality and biological properties are actively searched worldwide. Moringa oleifera seed protein isolate was prepared from defatted flour and hydrolyzed using four proteases namely trypsin, pepsin, Alcalase, and thermolysin. Then, antioxidant activity and cellular glucose uptake properties of the hydrolysates were assessed. A high degree of hydrolysis was obtained for hydrolysate prepared using trypsin (60.07%), followed by pepsin (57.14%), Alcalase (50.68%), and thermolysin (45.45%). Thermolysin hydrolysate was the most antioxidant efficient (IC50 0.15 and 0.74 mg/mL for 2,2'-azino-bis(acide 3-ethylbenzothiazoline-6-sulfonique) diammonium salt (ABTS) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, respectively). Trypsin hydrolysate stimulated high glucose uptake by yeast cells (12.34-35.28%). In the absence of insulin, Alcalase hydrolysate was the most efficient for glucose uptake by the muscle, with the rate ranging from 22.03% to 29.93% after 30 min, then from 29.55% to 34.6% after 60 min. The four hydrolysates improved glucose uptake by the muscle in the presence of insulin with the rate ranging from 46.88% to 58.03% after 30 min, and from 50% to 58.18% after 60 min. Therefore, Moringa oleifera seed proteins could be used to prepare peptides as components of functional foods for the management of type-2 diabetes.

Cerebral Benefits Induced by Electrical Muscle Stimulation: Evidence from a Human and Rat Study.

Physical exercise (EX) is well established for its positive impact on brain health. However, conventional EX may not be feasible for certain individuals. In this regard, this study explores electromyostimulation (EMS) as a potential alternative for enhancing cognitive function. Conducted on both human participants and rats, the study involved two sessions of EMS applied to the quadriceps with a duration of 30 min at one-week intervals. The human subjects experienced assessments of cognition and mood, while the rats underwent histological and biochemical analyses on the prefrontal cortex, hippocampus, and quadriceps. Our findings indicated that EMS enhanced executive functions and reduced anxiety in humans. In parallel, our results from the animal studies revealed an elevation in brain-derived neurotrophic factor (BDNF), specifically in the hippocampus. Intriguingly, this increase was not associated with heightened neuronal activity or cerebral hemodynamics; instead, our data point towards a humoral interaction from muscle to brain. While no evidence of increased muscle and circulating BDNF or FNDC5/irisin pathways could be found, our data highlight lactate as a bridging signaling molecule of the muscle-brain crosstalk following EMS. In conclusion, our results suggest that EMS could be an effective alternative to conventional EX for enhancing both brain health and cognitive function.

Effect of combined electrical stimulation and brief muscle lengthening on torque development.

This study aimed to evaluate torque production in response to the application of a brief muscle lengthening during neuromuscular electrical stimulation (NMES) applied over the posterior tibial nerve. Fifteen participants took part in three experimental sessions, where wide-pulse NMES delivered at 20 and 100 Hz (pulse duration of 1 ms applied during 15 s at an intensity evoking 5-10% of maximal voluntary contraction) was either applied alone (NMES condition) or in combination with a muscle lengthening at three distinct speeds (60, 180, or 300°/s; NMES + LEN condition). The torque-time integral (TTI) and the muscle activity following the stimulation trains [sustained electromyography (EMG)] were calculated for each condition. Results show that TTI and sustained EMG activity were higher for the NMES + LEN condition only when using 100-Hz stimulation, regardless of the lengthening speed (P = 0.029 and P = 0.007 for the two parameters, respectively). This indicates that superimposing a muscle lengthening to high-frequency NMES can enhance the total torque production, partly due to neural mechanisms, as evidenced by the higher sustained EMG activity. This finding has potential clinical relevance, especially when it comes to finding ways to enhance torque production to optimize the effectiveness of NMES training programs.NEW & NOTEWORTHY This study showed, for the first time, that the combined application of a brief muscle lengthening and wide-pulse neuromuscular electrical stimulation (NMES) delivered over the posterior tibial nerve can entail increased torque production as compared with the sole application of NMES. This observation, present only for high stimulation frequencies (100 Hz) and independently of the lengthening speed, is attributed to neural mechanisms, most probably related to increased afferents' solicitation, although muscular phenomena cannot be excluded.

Do soleus responses to transcutaneous spinal cord stimulation show similar changes to H-reflex in response to Achilles tendon vibration?

INTRODUCTION/PURPOSE: Recently, the use of transcutaneous spinal cord stimulation (TSCS) has been proposed as a viable alternative to the H-reflex. The aim of the current study was to investigate to what extent the two modes of spinal cord excitability investigation would be similarly sensitive to the well-known vibration-induced depression. METHODS: Fourteen healthy participants (8 men and 6 women; age: 26.7 ± 4.8 years) were engaged in the study. The right soleus H-reflex and TSCS responses were recorded at baseline (PRE), during right Achilles tendon vibration (VIB) and following 20 min of vibration exposure (POST-VIB). Care was taken to match H-reflex and TSCS responses amplitude at PRE and to maintain effective stimulus intensities constant throughout time points. RESULTS: The statistical analysis showed a significant effect of time for the H-reflex, with VIB (13 ± 5% of maximal M-wave (Mmax) and POST-VIB (36 ± 4% of Mmax) values being lower than PRE-values (48 ± 6% of Mmax). Similarly, TSCS responses changed over time, VIB (9 ± 5% of Mmax) and POST-VIB (27 ± 5% of Mmax) values being lower than PRE-values (46 ± 6% of Mmax). Pearson correlation analyses revealed positive correlation between H-reflex and TSCS responses PRE-to-VIB changes, but not for PRE- to POST-VIB changes. CONCLUSION: While the sensitivity of TSCS seems to be similar to the gold standard H-reflex to highlight the vibratory paradox, both responses showed different sensitivity to the effects of prolonged vibration, suggesting slightly different pathways may actually contribute to evoked responses of both stimulation modalities.

Cadence Modulation during Eccentric Cycling Affects Perception of Effort But Not Neuromuscular Alterations.

INTRODUCTION: A recent study showed that cadence modulation during short eccentric cycling exercise affects oxygen consumption (V̇O 2 ), muscular activity (EMG), and perception of effort (PE). This study examined the effect of cadence on V̇O 2 , EMG, and PE during prolonged eccentric cycling and exercise-induced neuromuscular alterations. METHODS: Twenty-two participants completed three sessions 2-3 wk apart: 1) determination of the maximal concentric peak power output, familiarization with eccentric cycling at two cadences (30 and 60 rpm at 60% peak power output), and neuromuscular testing procedure; 2) and 3) 30 min of eccentric cycling exercise at a cadence of 30 or 60 rpm. PE, cardiorespiratory parameters, and vastus lateralis and rectus femoris EMG were collected during exercise. The knee extensors' maximal voluntary contraction torque, the torque evoked by double stimulations at 100 Hz (Dt100) and 10 Hz (Dt10), and the voluntary activation level were evaluated before and after exercise. RESULTS: V̇O 2 , EMG, and PE were greater at 30 than 60 rpm (all P < 0.05). Maximal voluntary contraction torque, evoked torque, and Dt10/Dt100 ratio decreased (all P < 0.01) without cadence effect (all P > 0.28). Voluntary activation level remained constant after both eccentric cycling exercises ( P = 0.87). CONCLUSIONS: When performed at the same power output, eccentric cycling exercise at 30 rpm elicited a greater PE, EMG, and cardiorespiratory demands than pedaling at 60 rpm. Exercise-induced fatigability was similar in both eccentric cycling conditions without neural impairments, suggesting that eccentric cycling seemed to alter more specifically muscular function, such as the excitation-contraction coupling process. In a rehabilitation context, eccentric cycling at 60 rpm seems more appropriate because it will induce lower PE for similar strength loss compared with 30 rpm.

Local vibration induces changes in spinal and corticospinal excitability in vibrated and antagonist muscles.

Local vibration (LV) applied over the muscle tendon constitutes a powerful stimulus to activate the muscle spindle primary (Ia) afferents that project to the spinal level and are conveyed to the cortical level. This study aimed to identify the neuromuscular changes induced by a 30-min LV-inducing illusions of hand extension on the vibrated flexor carpi radialis (FCR) and the antagonist extensor carpi radialis (ECR) muscles. We studied the change of the maximal voluntary isometric contraction (MVIC, experiment 1) for carpal flexion and extension, motor-evoked potentials (MEPs, experiment 2), cervicomedullary motor-evoked potentials (CMEPs, experiment 2), and Hoffmann's reflex (H-reflex, experiment 3) for both muscles at rest. Measurements were performed before (PRE) and at 0, 30, and 60 min after LV protocol. A lasting decrease in strength was only observed for the vibrated muscle. The reduction in CMEPs observed for both muscles seems to support a decrease in alpha motoneurons excitability. In contrast, a slight decrease in MEPs responses was observed only for the vibrated muscle. The MEP/CMEP ratio increase suggested greater cortical excitability after LV for both muscles. In addition, the H-reflex largely decreased for the vibrated and the antagonist muscles. The decrease in the H/CMEP ratio for the vibrated muscle supported both pre- and postsynaptic causes of the decrease in the H-reflex. Finally, LV-inducing illusions of movement reduced alpha motoneurons excitability for both muscles with a concomitant increase in cortical excitability.NEW & NOTEWORTHY Spinal disturbances confound the interpretation of excitability changes in motor areas and compromise the conclusions reached by previous studies using only a corticospinal marker for both vibrated and antagonist muscles. The time course recovery suggests that the H-reflex perturbations for the vibrated muscle do not only depend on changes in alpha motoneurons excitability. Local vibration induces neuromuscular changes in both vibrated and antagonist muscles at the spinal and cortical levels.

Gravity-efficient motor control is associated with contraction-dependent intracortical inhibition.

In humans, moving efficiently along the gravity axis requires shifts in muscular contraction modes. Raising the arm up involves shortening contractions of arm flexors, whereas the reverse movement can rely on lengthening contractions with the help of gravity. Although this control mode is universal, the neuromuscular mechanisms that drive gravity-oriented movements remain unknown. Here, we designed neurophysiological experiments that aimed to track the modulations of cortical, spinal, and muscular outputs of arm flexors during vertical movements with specific kinematics (i.e., optimal motor commands). We report a specific drop of corticospinal excitability during lengthening versus shortening contractions, with an increase of intracortical inhibition and no change in spinal motoneuron responsiveness. We discuss these contraction-dependent modulations of the supraspinal motor output in the light of feedforward mechanisms that may support gravity-tuned motor control. Generally, these results shed a new perspective on the neural policy that optimizes movement control along the gravity axis.

Neuromuscular fatigability of plantar flexors following continuous and intermittent contractions.

The purpose of this study is to investigate if a continuous muscle contraction (CON) is more fatiguing than an intermittent exercise (INT) performed until task failure. To get a more comprehensive picture of neuromuscular fatigability, in addition to the commonly used maximal voluntary contraction (MVC), we assessed the maximal torque sustainability (i.e., the ability to maintain a high level of torque for 1 min). Fourteen subjects performed a plantar flexors MVC of 1-min duration (MVC1-MIN) before and after CON or INT contractions at 40% MVC until task failure. Despite a greater torque-time integral for the INT task, a similar MVC reduction was found after both exercises. On the contrary, a greater torque loss during the MVC1-MIN was observed after the CON exercise and it was positively correlated to the mean exercise torque. These results reveal that, for exercises performed until exhaustion, the contraction pattern (i.e., CON vs. INT) affects the ability to maintain a high level of torque, but does not influence the maximal torque production capacity. Thus, we demonstrate that maximal torque production and sustainability are two distinct and complementary characteristics of neuromuscular fatigability. Consequently, when considering both capacities, it results that, an exhausting CON contraction is more fatiguing than an exhausting INT effort. This highlights the importance of simultaneously evaluating both capacities when exploring neuromuscular fatigability.NEW & NOTEWORTHY This study provides new information about the influence of the contraction pattern (i.e., continuous and intermittent) on the development of neuromuscular fatigability when exercise is performed until exhaustion. Maximal torque production is similarly reduced by both exercises, whereas maximal torque sustainability is impaired only after the continuous exercise. To evaluate neuromuscular fatigability, we then recommend using a sustained maximal voluntary contraction since this measure allows to concurrently collect information on complementary aspects of neuromuscular fatigability.

Can motor imagery balance the acute fatigue induced by neuromuscular electrical stimulation?

PURPOSE: The combination of motor imagery (MI) and neuromuscular electrical stimulation (NMES) can increase the corticospinal excitability suggesting that such association could be efficient in motor performance improvement. However, differential effect has been reported at spinal level after MI and NMES alone. The purpose of this study was to investigate the acute effect on motor performance and spinal excitability following MI, NMES and combining MI and NMES. METHODS: Ten participants were enrolled in three experimental sessions of MI, NMES and MI + NMES targeting plantar flexor muscles. Each session underwent 60 imagined, evoked (20% MVC) or imagined and evoked contractions simultaneously. Before, immediately after and 10 min after each session, maximal M-wave and H-reflex were evoked by electrical nerve stimulation applied at rest and during maximal voluntary contraction (MVC). RESULTS: The MVC decreased significantly between PRE-POST (- 12.14 ± 6.12%) and PRE-POST 10 (- 8.1 ± 6.35%) for NMES session, while this decrease was significant only between PRE-POST 10 (- 7.16 ± 11.25%) for the MI + NMES session. No significant modulation of the MVC was observed after MI session. The ratio Hmax/Mmax was reduced immediately after NMES session only. CONCLUSION: The combination of MI to NMES seems to delay the onset of neuromuscular fatigue compared to NMES alone. This delay onset of neuromuscular fatigue was associated with specific modulation of the spinal excitability. These results suggested that MI could compensate the neuromuscular fatigue induced acutely by NMES until 10 min after the combination of both modalities.

Effect of Cadence on Physiological and Perceptual Responses during Eccentric Cycling at Different Power Outputs.

INTRODUCTION: The effect of cadence in eccentric (ECC) cycling on physiological and perceptual responses is, to date, poorly understood. This study aimed to evaluate the effect of cadence during ECC cycling on muscular activation (EMG), oxygen consumption (V̇O 2 ), and perceived effort (PE) for two different levels of power output. METHODS: Seventeen participants completed four sessions 1 wk apart: 1) determination of the maximal concentric peak power output (PPO) and familiarization with ECC cycling at five cadences (30, 45, 60, 75, and 90 rpm); 2) second familiarization with ECC cycling; 3) and 4) ECC cycling exercise consisting of 5 min at the five different cadences at either 40% or 60% PPO. PE was reported, and V̇O 2 and EMG of seven muscles were calculated over the exercise's last minute. RESULTS: PE, V̇O 2 , and global lower limb muscles activation (EMG ALL ) showed an effect of cadence ( P < 0.001) and followed a curvilinear function. Both low and high cadences increased PE and V̇O 2 responses compared with intermediate cadences. Although muscle activation of vastus lateralis follows a U-shaped curve with cadence, it was greater at low cadence for rectus femoris and biceps femoris, greater at high cadence for tibialis anterior and gastrocnemius medialis, and was not altered for soleus. The estimated optimal cadence was greater (all P < 0.01) for V̇O 2 (64.5 ± 7.9 rpm) than PE (61.7 ± 9.4 rpm) and EMG ALL (55.9 ± 9.3 rpm), but power output had no effect on the optimal cadences. CONCLUSIONS: The physiological and perceptual responses to changes in cadence during ECC cycling followed a U-shaped curve with an optimal cadence depending on the parameter considered.

Characterisation of Bioactive Peptides from Red Alga Gracilariopsis chorda.

In this study, we studied the bioactive peptides produced by thermolysin hydrolysis of a water-soluble protein (WSP) from the red alga Gracilariopsis chorda, whose major components are phycobiliproteins and Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCo). The results showed that WSP hydrolysate exhibited significantly higher ACE inhibitory activity (92% inhibition) compared to DPP-IV inhibitory activity and DPPH scavenging activity. The phycobiliproteins and RuBisCo of G. chorda contain a high proportion of hydrophobic (31.0-46.5%) and aromatic (5.1-46.5%) amino acid residues, which was considered suitable for the formation of peptides with strong ACE inhibitory activity. Therefore, we searched for peptides with strong ACE inhibitory activity and identified two novel peptides (IDHY and LVVER). Then, their interaction with human ACE was evaluated by molecular docking, and IDHY was found to be a promising inhibitor. In silico analysis was then performed on the structural factors affecting ACE inhibitory peptide release, using the predicted 3D structures of phycobiliproteins and RuBisCo. The results showed that most of the ACE inhibitory peptides are located in the highly solvent accessible α-helix. Therefore, it was suggested that G. chorda is a good source of bioactive peptides, especially ACE-inhibitory peptides.

Antagonist muscle torque at the ankle interfere with maximal voluntary contraction under isometric and anisometric conditions.

While resultant maximal voluntary contraction (MVC) is commonly used to assess muscular performance, the simultaneous activation of antagonist muscles may dramatically underestimate the strength of the agonist muscles. Although quantification of antagonist torque has been performed in isometric conditions, it has yet to be determined in anisometric conditions. The aim of the study was to compare the mechanical impact of antagonist torque between eccentric, isometric and concentric contractions in PF and DF MVCs. The MVCs in dorsiflexion (DF) and plantar-flexion (PF) were measured in isometric, concentric and eccentric conditions (10° s-1) in nine healthy men (26.1 ± 2.7 years; 1.78 ± 0.05 m; 73.4 ± 6.5 kg) through two sessions. Electromyographic (EMG) activities from the soleus, gastrocnemius medialis and lateralis, and tibialis anterior muscles were simultaneously recorded. The EMG biofeedback method was used to quantify antagonist torque. Resultant torque significantly underestimated agonist torque in DF MVC (30-65%) and to a lesser extent in PF MVC (3%). Triceps surae antagonist torque was significantly modified with muscle contraction type, showing higher antagonist torque in isometric (29 Nm) than in eccentric (23 Nm, p < 0.001) and concentric (14 Nm, p < 0.001) conditions and resulting in modification of the DF MVC torque-velocity shape. Estimation of the antagonist torque in isometric or anisometric conditions provides new relevant insights to improve neuromuscular performance assessment and to better design strength training and rehabilitation programs related to the torque applied by agonist and antagonist muscles.

Specific modulation of presynaptic and recurrent inhibition of the soleus muscle during lengthening and shortening submaximal and maximal contractions.

The study analyzed neural mechanisms mediating spinal excitability modulation during eccentric (ECC) movement (passive muscle lengthening, submaximal, and maximal ECC contractions) as compared with concentric (CON) conditions. Twenty-two healthy subjects participated in three experiments. Experiment A (n = 13) examined D1 presynaptic inhibition (D1 PI) and recurrent inhibition (RI) modulation during passive muscle lengthening and shortening, by conditioning the soleus (SOL) H-reflex with common peroneal nerve submaximal and tibial nerve maximal stimulation, respectively. Experiment B (n = 13) analyzed the effect of passive muscle lengthening on D1 PI and heteronymous Ia facilitation (HF, conditioning the SOL H-reflex by femoral stimulation). Experiment C (n = 13) focused on the effect of muscle contraction level (20%, 50%, and 100% of maximal voluntary contraction) on D1 PI and RI. Results showed a significantly higher level of D1 PI during passive muscle lengthening than shortening (P < 0.01), whereas RI and HF were not affected by passive muscle movement. D1 PI and RI were both higher during ECC as compared with CON contractions (P < 0.001). However, the amount of D1 PI was independent of the torque level, whereas RI was reduced as the torque level increased (P < 0.05). The decreased spinal excitability induced by muscle lengthening during both passive and active conditions is mainly attributed to D1 PI, whereas RI also plays a role in the control of the specific motoneuron output during ECC contractions. Both inhibitory mechanisms are centrally controlled, but the fact that they evolve differently with torque increases, suggests a distinct supraspinal control.NEW & NOTEWORTHY Presynaptic (PI) and recurrent inhibitions (RI) were studied during passive muscle lengthening and eccentric contractions. Results indicate that the increased PI during passive muscle lengthening accounts for the decreased spinal excitability at rest. During eccentric contraction both mechanisms contribute to spinal excitability modulation. The same amount of PI was observed during eccentric contractions, while RI decreased as developed torque increased. This distinct modulation according to torque level suggests a distinct supraspinal control of these mechanisms.

The impact of submaximal fatiguing exercises on the ability to generate and sustain the maximal voluntary contraction.

Neuromuscular fatigability is a failure to produce or maintain a required torque, and commonly quantified with the decrease of maximal torque production during a few seconds-long maximal voluntary contraction (MVC). The literature shows that the MVC reduction after exercises with different torque-time integral (TTI), is often similar. However, it was shown that after a fatiguing exercise, the decline in the capacity to sustain the maximal voluntary contraction for 1 min (MVC1-MIN) differs from the decrease in the capacity to perform a brief-MVC, suggesting that this latter can only partially assess neuromuscular fatigability. This study aims to highlight the relevance of using a sustained MVC to further explore the neuromuscular alterations induced by fatiguing exercises with different TTI. We used two contraction intensities (i.e., 20% and 40% MVC) to modulate the TTI, and two exercise modalities [i.e., voluntary (VOL) and electrical induced (NMES)], since the letter are known to be more fatiguing for a given TTI. Thirteen subjects performed a plantar-flexors MVC1-MIN before and after the fatiguing exercises. A similar MVC loss was obtained for the two exercise intensities despite a greater TTI at 40% MVC, regardless of the contraction modality. On the other hand, the torque loss during MVC1-MIN was significantly greater after the 40% compared to 20% MVC exercise. These findings are crucial because they demonstrate that maximal torque production and sustainability are two complementary features of neuromuscular fatigability. Hence, MVC1-MIN assessing simultaneously both capacities is essential to provide a more detailed description of neuromuscular fatigability.

Sodium Pyruvate Nasal Spray Reduces the Severity of Nasal Inflammation and Congestion in Patients with Allergic Rhinitis.

Background: As an anti-inflammatory and antioxidant, sodium pyruvate significantly reduces inflammatory cytokines and oxygen radicals such as interleukin (IL) IL-6, IL-8, Monocyte Chemoattractant Protein-1, and hydrogen peroxide. Thus, sodium pyruvate holds promise as a treatment for many respiratory diseases, including allergic rhinitis (AR). Novel treatments for AR are needed as current medications, including steroids, often fail to treat severe symptoms. Methods: The data from five human clinical studies were analyzed to determine the effect of 20 mM sodium pyruvate nasal spray (N115) in patients with AR. Nasal inflammation scores were compared to a placebo control or a no-treatment baseline control. Three studies were open-labeled and two were appropriately blinded to both patients and clinicians using computer randomization of subjects. Results: The intranasal administration of sodium pyruvate significantly improved nasal inflammation scores in all five clinical trials of patients with AR (p < 0.0001 in all trials). Conclusions: These results give credence to the overall ability of sodium pyruvate, administered by nasal spray, to treat inflammation of the nasal airways.

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.