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.

Motor imagery from brain to muscle: a commentary on Bach et al., (2022).

In a recent article entitled "Why motor imagery is not really motoric: towards a re-conceptualization in terms of effect-based action control", Bach et al. nicely renewed the concept of motor equivalence between actual movement and motor imagery (MI), i.e. the mental simulation of an action without its corresponding motor output. Their approach is largely based on behavioral studies and, to a lesser extent, on the literature using cerebral imagery. However, the literature on cortico-spinal circuitry modulation during MI can provide further, interesting aspects. Indeed, when it comes to addressing the motor system, one should consider the whole path from brain region to muscle contraction, including sub-cortical structures such as the spinal circuitry. This commentary aims at bridging this gap by providing supplemental evidence and outlining a complementary approach.

Acute effect of transcranial direct current stimulation (tDCS) on postural control of trained athletes: A randomized controlled trial.

Transcranial direct current stimulation (tDCS) is used to modulate brain function, and can modulate motor and postural control. While the acute effect of tDCS is well documented on patients, little is still known whether tDCS can alter the motor control of healthy trained participants. This study aimed to assess the acute effect of tDCS on postural control of parkour practitioners, known for their good balance abilities and their neuromuscular specificities that make them good candidates for tDCS intervention. Eighteen parkour practitioners were tested on three occasions in the laboratory for each stimulation condition (2 mA; 20 minutes)-primary motor cortex (M1), dorsolateral prefrontal cortex (dlPFC) and sham (placebo). Postural control was evaluated PRE and POST each stimulation by measuring Center of Pressure (CoP) displacements on a force platform during static conditions (bipedal and unipedal stance). Following M1 stimulation, significant decreases were observed in CoP area in unipedal (from 607.1 ± 297.9 mm2 to 451.1 ± 173.9 mm2, P = 0.003) and bipedal (from 157.5 ± 74.1 mm2 to 117.6 ± 59.8 mm2 P<0.001) stances. As well, the CoP total length was significantly reduced in bipedal (from 3416.8 ± 295.4 mm to 3280.6 ± 306.2 mm, P = 0.005) as well as in unipedal stance (from 4259.6 ± 398.4 mm to 3846.5 ± 468.9 mm, P<0.001), only after M1 stimulation. Relative pre-post changes observed after M1 stimulation were negatively correlated to experience in parkour only after unipedal stance (r = 0.715, P<0.001), meaning that the more participants were trained the less tDCS was effective. No significant changes were noticed after sham and dlPFC stimulation. These results suggested that the modulation of gait performance in athletes following an acute intervention of tDCS is specific to the targeted brain region, and that postures with reduced base of support (such as unipedal stance) were more sensitive to tDCS.

Effect of tDCS targeting the M1 or left DLPFC on physical performance, psychophysiological responses, and cognitive function in repeated all-out cycling: a randomized controlled trial.

BACKGROUND: Despite reporting the positive effects of transcranial direct current stimulation (tDCS) on endurance performance, very few studies have investigated its efficacy in anaerobic short all-out activities. Moreover, there is still no consensus on which brain areas could provide the most favorable effects on different performance modalities. Accordingly, this study aimed to investigate the effects of anodal tDCS (a-tDCS) targeting the primary motor cortex (M1) or left dorsolateral prefrontal cortex (DLPFC) on physical performance, psychophysiological responses, and cognitive function in repeated all-out cycling. METHODS: In this randomized, crossover, and double-blind study, 15 healthy physically active men underwent a-tDCS targeting M1 or the left DLPFC or sham tDCS in separate days before performing three bouts of all-out 30s cycling anaerobic test. a-tDCS was applied using 2 mA for 20 min. Peak power, mean power, fatigue index, and EMG of the quadriceps muscles were measured during each bout. Heart rate, perceived exertion, affective valence, and arousal were recorded two minutes after each bout. Color-word Stroop test and choice reaction time were measured at baseline and after the whole anaerobic test. RESULTS: Neither tDCS montage significantly changed peak power, mean power, fatigue index, heart rate, affective valence, arousal, and choice reaction time (p> 0.05). a-tDCS over DLPFC significantly lowered RPE of the first bout (compared to sham; p=0.048, Δ=-12.5%) and third bout compared to the M1 (p=0.047, Δ=-12.38%) and sham (p=0.003, Δ=-10.5%), increased EMG of the Vastus Lateralis muscle during the second (p=0.016, Δ= +40.3%) and third bout (p=0.016, Δ= +42.1%) compared to sham, and improved the score of color-word Stroop test after the repeated all-out task (p=0.04, Δ= +147%). The qualitative affective response (valence and arousal) was also higher under the M1 and DLPFC compared to the sham. CONCLUSION: We concluded that tDCS targeting M1 or DLPFC does not improve repeated anaerobic performance. However, the positive effect of DLPFC montage on RPE, EMG, qualitative affective responses, and cognitive function is promising and paves the path for future research using different tDCS montages to see any possible effects on anaerobic performance. TRIAL REGISTRATION: This study was approved by the Ethics Committee of Razi University (IR.RAZI.REC.1400.023) and registered in the Iranian Registry of Clinical Trials (IRCT id: IRCT20210617051606N5; Registration Date: 04/02/2022).

Post-Activation Performance Enhancement and Motor Imagery Are Efficient to Emphasize the Effects of a Standardized Warm-Up on Sprint-Running Performances.

Warm-up routines include various tasks focused on the peripheral contractile properties and nervous motor command. This present study was aimed at investigating the acute effects of different warm-up routines, emphasizing either peripheral (post-activation performance enhancement, PAPE) or central (motor imagery, MI) contributions on sport-specific tasks. Eleven young female athletes took part in this cross-over, randomized, controlled trial. They underwent three experimental sessions composed of a standardized warm-up followed by 10 min of (1) rest (CONTROL), (2) maximal concentric leg press (PAPE), or (3) mental repetitions of sprint tasks (MI). Post-tests consisted of reaction time, arrowhead agility test, 20 m sprint, repeated sprint ability, and NASA-TLX fatigue questionnaire. PAPE and MI significantly enhanced the arrowhead agility test (p < 0.001 and p = 0.012, respectively) and repeated sprint ability (p = 0.002 and p = 0.035, respectively) compared to CONTROL, without any difference between PAPE and MI. The 20 m sprint time was better after PAPE as compared to MI (p = 0.005) and CONTROL (p < 0.001), without any difference between MI and CONTROL. Reaction time and the NASA-TLX questionnaire were not affected by the warm-up modalities (p > 0.05). PAPE was the most efficient to optimize warm-up due to its greater peripheral contribution that would improve muscle contractility. MI specifically improved the imagined tasks mostly by central contribution.

Anodal tDCS over the left DLPFC but not M1 increases muscle activity and improves psychophysiological responses, cognitive function, and endurance performance in normobaric hypoxia: a randomized controlled trial.

BACKGROUND: Transcranial direct current stimulation (tDCS) has been shown to have positive effects on exercise performance and cognitive function in the normal ambient condition. Hypoxia is deemed a stressful situation with detrimental effects on physiological, psychological, cognitive, and perceptual responses of the body. Nevertheless, no study has evaluated the efficacy of tDCS for counteracting the negative effects of hypoxic conditions on exercise performance and cognition so far. Hence, in the present study, we investigated the effects of anodal tDCS on endurance performance, cognitive function, and perceptual responses in hypoxia. PARTICIPANTS AND METHODS: Fourteen endurance-trained males participated in five experimental sessions. After familiarization and measuring peak power output in hypoxia, in the first and second sessions, through the 3rd to 5th sessions, participants performed a cycling endurance task until exhaustion after 30 min hypoxic exposure at resting position followed by 20 min of anodal stimulation of the motor cortex (M1), left dorsolateral prefrontal cortex (DLPFC), or sham-tDCS. Color-word Stroop test and choice reaction time were measured at baseline and after exhaustion. Time to exhaustion, heart rate, saturated O2, EMG amplitude of the vastus lateralis, vastus medialis, and rectus femoris muscles, RPE, affective response, and felt arousal were also measured during the task under hypoxia. RESULTS: The results showed a longer time to exhaustion (+ 30.96%, p=0.036), lower RPE (- 10.23%, p = 0.045) and higher EMG amplitude of the vastus medialis muscle (+ 37.24%, p=0.003), affective response (+ 260%, p=0.035) and felt arousal (+ 28.9%, p=0.029) in the DLPFC tDCS compared to sham. The choice reaction time was shorter in DLPFC tDCS compared to sham (- 17.55%, p=0.029), and no differences were seen in the color-word Stroop test among the conditions under hypoxia. M1 tDCS resulted in no significant effect for any outcome measure. CONCLUSIONS: We concluded that, as a novel finding, anodal stimulation of the left DLPFC might provide an ergogenic aid for endurance performance and cognitive function under the hypoxic condition probably via increasing neural drive to the working muscles, lowering RPE, and increasing perceptual responses.

How Exergaming with Virtual Reality Enhances Specific Cognitive and Visuo-Motor Abilities: An Explorative Study.

Virtual reality (VR) is the computer simulation of a three-dimensional environment that a person can interact with using special electronic equipment, such as a headset with an integrated display. Often coupled with VR, exergames are video games that involve physical exercise. Little is known regarding the chronic effects of exergaming through VR chon cognitive functions. Eleven young participants were enrolled in this crossover exploratory study. They had to follow two trainings of 5 consecutive days, 15 min per day, interspaced by a 1-month washout period. Trainings were performed in a random order: (1) a video training using shadow boxing fitness videos (SBV) and (2) a VR training using a three-dimensional game where the aim is to cut moving cubes with a sword in each hand. Before and after each training period, a battery of cognitive tests was performed to assess executive functions, such as attention (change blindness), reaction time, response inhibition (go/no-go, Stroop task), or flexibility (trail making test). Fine motor skills were also evaluated through a Fitt's task. No effect of the SBV training was observed on any of the cognitive functions tested. On the contrary, a significant increased performance in selective attention and observation tests was found after VR training, as well as in inhibitory processes (Stroop and go/no-go). Other performances were unaffected by either VR or SBV training. The present study argues that VR exergaming is a promising tool to promote cognitive enhancement but targets specific functions according to the type of interface/game that is used.

Physiological demands and physical performance determinants of a new firefighting simulation test.

The study aimed to examine physiological responses of firefighters performing a firefighting simulation test (FST) and to determine the relationship between physical fitness parameters and FST performance. Aerobic fitness, muscular strength, muscular endurance, and anaerobic capabilities were evaluated in 37 firefighters (21-profesionals and 16-volunteers firefighters). Furthermore, participants carried out the FST during which we measured performance, respiratory gas exchange, heart rate (HR), perceived exertion and blood lactate concentrations. Males were significantly faster than females for all tasks of the FST (p < 0.01); however, final performance score (16.5 ± 2.9 and 14.5 ± 2.6 points for males and females, respectively), HR (94.0 ± 2.0% and 93.7 ± 2.3% of HRmax) and perceived exertion (8.1 ± 0.9 and 7.1 ± 1.3) were not significantly different. Prediction of FST performance by LASSO regression revealed a model that included mainly aerobic capacity and maximal strength. In conclusion, FST challenged both aerobic and anaerobic energy metabolisms for both males and females and requires various physiological abilities to perform. Practitioner Summary: For the safety of firefighters and victims, firefighters must meet minimum physical requirements. 37 firefighters performed physical tests and a new firefighting test implemented for the recruitment of firefighters in France. The results revealed that this test is strenuous and that performance is associated with cardiorespiratory fitness and muscular strength. Abbreviations: V̇O2: oxygen consumption; V̇CO2: carbon dioxyde production; V̇E: expired ventilation; RER: respiratory exchange ratio; FST: firefighting simulation test; MAS: maximal aerobic speed; HR: heart rate; RPE: rating of perceived exertion; MVC: maximum voluntary contraction; IMTP: isometric mid-thigh pull; TTE: time to exhaustion; Ppeak: peak power; Pmean: mean power; LASSO: least absolute shrinkage and selection operator; La-: blood lactate concentration.

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.

Virtual reality does not fool the brain only: spinal excitability changes during virtually simulated falling.

Virtual reality (VR) is known to induce substantial activation of brain's motor regions. It remains unclear to what extent virtual reality can trigger the sensorimotor system, and more particularly, whether it can affect lower nervous levels. In this study, we aimed to assess whether VR simulation of challenging and stressful postural situations (Richie's plank experience) could interfere with spinal excitability of postural muscles in 15 healthy young participants. The H-reflex of the triceps surae muscles was elicited with electrical nerve stimulation while participants were standing and wearing a VR headset. Participants went through several conditions, during which stimulations were evoked: standing still (noVR), standing in VR on the ground (groundVR), standing on the edge of a building (plankVR), and falling from the building (fallingVR). Myoelectrical activity of the triceps surae muscles was measured throughout the experiment. Leg and head movements were also measured by means of accelerometers to account for body oscillations. First, no differences in head rotations and myoelectrical activity were to be noted between conditions. Second, triceps H-reflex (HMAX/MMAX) was not affected from noVR to groundVR and plankVR. The most significant finding was a drastic decrease in H-reflex during falling (-47 ± 26.9% between noVR and fallingVR, P = 0.015). It is suggested that experiencing a postural threat in VR efficiently modulates spinal excitability, despite remaining in a quiet standing posture. This study suggests that simulated falling mimics the neural adjustments observed during actual postural challenge tasks.NEW & NOTEWORTHY The present study showed a modulation of spinal excitability induced by virtual reality (VR). In the standing position, soleus H-reflex was downmodulated during a simulated falling, in the absence of apparent changes in body oscillations. Since the same behavior is usually observed during real falling, it was suggested that the visual cues provided by VR were sufficiently strong to lead the neuromuscular system to mimic the actual modulation.

Cardiometabolic and neuromuscular analyses of the sit-to-stand transition to question its role in reducing sedentary patterns.

To counteract the detrimental health effect of sitting all day long, it has been suggested to regularly break sitting time by standing. However, while the difference in energy expenditure, neuromuscular and/or cardiovascular demand of various postures from lying, sitting, and standing is well documented, little is known regarding the dynamic changes occurring during the sit-to-stand transition itself. The aim of the present study was then to describe the cardiometabolic and neuromuscular responses from sitting to standing and specifically during the time-course of this transition. Twelve healthy young participants were asked to perform standardized raises from sitting posture, while cardiometabolic (cardiorespiratory and hemodynamic variables) and neuromuscular (calf muscles' myoelectrical activity, spinal and supraspinal excitabilities) parameters were monitored. As a result, while there was a rapid adaptation for all the systems after rising, the neuromuscular system displayed the faster adaptation (~ 10 s), then hemodynamic (~ 10 to 20 s) and finally the metabolic variables (~ 30 to 40 s). Oxygen uptake, energy expenditure, ventilation, and heart rate were significantly higher and stroke volume significantly lower during standing period compared to sitting one. In calf muscles, spinal excitability (H-reflexes), was lowered by the sit-to-stand condition, while supraspinal drive (V-wave) was similar, indicating different cortico-spinal balance from sitting to standing. Although very heterogenous among participants in terms of magnitude, the present results showed a rapid adaptation for all the systems after rising and the health benefit, notably in terms of energy expenditure, appears rather modest, even if non negligeable.

What Makes Parkour Unique? A Narrative Review Across Miscellaneous Academic Fields.

Parkour is a growing sport that mostly involves jumping, vaulting over obstacles, and climbing in a non-dedicated setting. The authors gathered all known relevant literature across miscellaneous academic fields in order to define parkour with regard to other sports disciplines. Parkour is a lifestyle sport, and as such provides an alternative to mainstream sports, away from strict rules, standardized settings, and necessary competitions. Traceurs (parkour adepts) consider the city as a playground and as an outlet for their creativity, but they also have a strong taste for hard and individualized challenges. They usually train on non-specific structures, at ground level. Although their social background is not clear, they are mostly young and male. Traceurs are stronger than recreational athletes, especially in eccentric exercises. However, their endurance skills may be below average. One of the core specificities of parkour is its precision constraint at landing, which turns a standing long jump into a precision jump, regulated in flight so as to prepare for landing. The running precision jump follows the same landing pattern, and its flight phase contrasts with long jump techniques. Injuries, which are not more frequent than in other sports, often occur at landing and to lower limb extremities. This risk is mitigated by targeting the landing area with the forefoot instead of letting the heel hit the ground like in gymnastics, or with rolling in order to dissipate the impact. Overall, parkour focuses on adaptability to new environments, which leads to specific techniques that have not yet been extensively addressed by the literature.

Stand Up to Excite the Spine: Neuromuscular, Autonomic, and Cardiometabolic Responses During Motor Imagery in Standing vs. Sitting Posture.

Motor imagery (MI) for health and performance strategies has gained interest in recent decades. Nevertheless, there are still no studies that have comprehensively investigated the physiological responses during MI, and no one questions the influence of low-level contraction on these responses. Thus, the aim of the present study was to investigate the neuromuscular, autonomic nervous system (ANS), and cardiometabolic changes associated with an acute bout of MI practice in sitting and standing condition. Twelve young healthy males (26.3 ± 4.4 years) participated in two experimental sessions (control vs. MI) consisting of two postural conditions (sitting vs. standing). ANS, hemodynamic and respiratory parameters, body sway parameters, and electromyography activity were continuously recorded, while neuromuscular parameters were recorded on the right triceps surae muscles before and after performing the postural conditions. While MI showed no effect on ANS, the standing posture increased the indices of sympathetic system activity and decreased those of the parasympathetic system (p < 0.05). Moreover, MI during standing induced greater spinal excitability compared to sitting posture (p < 0.05), which was accompanied with greater oxygen consumption, energy expenditure, ventilation, and lower cardiac output (p < 0.05). Asking individuals to perform MI of an isometric contraction while standing allows them to mentally focus on the motor command, not challenge balance, and produce specific cardiometabolic responses. Therefore, these results provide further evidence of posture and MI-related modulation of spinal excitability with additional autonomic and cardiometabolic responses in healthy young men.

Different plantar flexors neuromuscular and mechanical characteristics depending on the preferred running form.

Two main types of endurance runners have been identified: aerial runners (AER), who have a larger flight time, and terrestrial runners (TER), who have a longer ground contact time. The purpose of this study was to assess the neuromuscular characteristics of plantar flexors between AER and TER runners. Twenty-four well-trained runners participated in the experiment. They were classified either in a TER or AER group according to the Volodalen® scale. Plantar flexors' maximal rate of force development (RFD) and maximal voluntary contraction force (MVC) were assessed. Percutaneous electrical stimulation was delivered to the posterior tibial nerve to evoke maximal M-waves and H-reflexes of the triceps surae muscles. These responses, as well as voluntary activation, muscle potentiation, and V-waves, were recorded by superimposing stimulations to MVCs. RFD was significantly higher in AER than in TER, while MVC remained unchanged. This was accompanied by higher myoelectrical activity recorded in the soleus muscle. While M-waves and other parameters remained unchanged, maximal H-reflex was significantly higher in AER than in TER, still in soleus only. The present study raised the possibility of different plantar flexors' neuromuscular characteristics according to running profile. These differences seemed to be focused on the soleus rather than on the gastrocnemii.

Neural Efficiency and Ability to Produce Accurate Efforts in Different Perceived Intensity Zones.

This study aimed to investigate the relationship between neural efficiency and the ability of an athlete to produce accurate efforts in different perceived intensity zones during a racing scenario. The α/ß ratio was used to quantify the neural efficiency during cycling, as it traduced the degree of participants information processing activity with lower cortical activity possible. Twelve trained competitive male cyclists delimited their perceived intensity zones 2 to 6 on a scale to assess the rating of exercise intensity. Then, they performed a 30 min racing scenario during which they had to produce different perceived intensities. The ability of athletes to produce perceived effort with accuracy and their neural efficiency was quantified during the racing scenario. The increase in the neural efficiency with the increase in the effort intensity could partly explain the improvement in athletes' ability to produce accurately perceived efforts from intensity zones 3 to 6. Moreover, the neural efficiency during the racing scenario was significantly correlated to the ability to produce perceived effort with accuracy at submaximal intensities.

Does partial activation of the neuromuscular system induce cross-education training effect? Case of a pilot study on motor imagery and neuromuscular electrical stimulation.

INTRODUCTION: Cross education defines the gains observed in the contralateral limb following unilateral strength training of the other limb. The present study questioned the neural mechanisms associated with cross education following training by motor imagery (MI) or submaximal neuromuscular electrical stimulation (NMES), both representing a partial activation of the motor system as compared to conventional strength training. METHODS: Twenty-seven participants were distributed in three groups: MI, NMES and control. Training groups underwent a training program of ten sessions in two weeks targeting plantar flexor muscles of one limb. In both legs, neuromuscular plasticity was assessed through maximal voluntary isometric contraction (MViC) and triceps surae electrophysiological responses evoked by electrical nerve stimulation (H-reflexes and V-waves). RESULTS: NMES and MI training improved MViC torque of the trained limb by 11.3% (P < 0.001) and 13.8% (P < 0.001), respectively. MViC of the untrained limb increased by 10.3% (P < 0.003) in the MI group only, accompanied with increases in V-waves on both sides. In the NMES group, V-waves only increased in the trained limb. In the MI group, rest H-reflexes increased in both the trained and the untrained triceps suraes. CONCLUSION: MI seems to be effective to induce cross education, probably because of the activation of cortical motor regions that impact the corticospinal neural drive of both trained and untrained sides. Conversely, submaximal NMES did not lead to cross education. The present results emphasize that cross education does not necessarily require muscle activity of the trained limb.

Effect of transcranial direct current stimulation on the psychomotor, cognitive, and motor performances of power athletes.

In sports science, transcranial direct current stimulation (tDCS) has many unknown effects on neuromuscular, psychomotor and cognitive aspects. Particularly, its impact on power performances remains poorly investigated. Eighteen healthy young males, all trained in a jumping sport (parkour) performed three experimental sessions: anodal tDCS applied either on the left dorsolateral prefrontal cortex (dlPFC, cathode in supraorbital area) or on the primary motor cortex (M1, cathode on contralateral shoulder), and a placebo condition (SHAM), each applied for 20 min at 2 mA. Pre and post, maximal vertical and horizontal jumps were performed, associated to leg neuromuscular assessment through electromyography and peripheral nerve stimulations. Actual and imagined pointing tasks were also performed to evaluate fine motor skills, and a full battery of cognitive and psychomotor tests was administered. M1 tDCS improved jump performance accompanied by an increase in supraspinal and spinal excitabilities. dlPFC stimulation only impacted the pointing tasks. No effect on cognitive tests was found for any of the tDCS conditions. To conclude, the type of performance (maximal versus accurate) affected depended upon the tDCS montage. Finally, athletes responded well to tDCS for motor performance while results to cognitive tests seemed unaffected, at least when implemented with the present rationale.

Feasibility and acceptability of "active" classroom workstations among French university students and lecturers: a pilot study.

BACKGROUND: Sedentary lifestyles plague today's society in terms of physical, psychosocial and cognitive health. Students are particularly at risk because they spend most of their daily time sitting and inactive. The current pedagogical model must be rethought in order to promote students' health, well-being and therefore their success. The objective of this project was to equip one classroom of the sport science department at a university with various active workstations (standing desks, Swiss balls, cycling desks, pedal- or stepper-board) and to evaluate the feasibility and influence of these types of active workstations on the cognitive and psychological factors of the students, and to collect the feedback of lecturers during this experience. METHODS: Participation in the study was voluntary and students had the opportunity to choose or not to use an active workstation during lectures. A total of 663 students and 14 lecturers completed a survey to evaluate subjective feelings about physical, psycho-cognitive and academic aspects after their first experience with active workstations in the classroom. RESULTS: The majority of students and lecturers reported positive effects of active workstations in reducing fatigue, distraction, and boredom. The preferred active workstations were the cycling desks and the Swiss balls. Finally, 89.4% of students favoured using active workstations in future lectures if they had the option, as well as 71% of lecturers, demonstrating the acceptance of such active workstations. CONCLUSION: The present study brings promising results toward a more general implementation of active workstations in universities. Once a familiarisation period is observed, having such workstations in the classroom could help prevent the deleterious effect of sedentary behaviour and promote a more active daily life for the future.

Psychophysiological responses of firefighters to day and night rescue interventions.

This study aimed 1) to assess the psychophysiological responses throughout a rescue intervention performed during the day and at night and 2) to determine if a vibrating alarm influences these psychophysiological responses at night. Sixteen male firefighters completed a simulated intervention under three different conditions: 1) during the day with a sound alarm signal (DaySA), 2) during the night with a sound alarm signal (NightSA), 3) during the night with a vibrating alarm signal (NightVA). Cardiovascular and psychological stress were recorded throughout the interventions. During the alarm signal, HR reactivity was greater in NightSA than in DaySA (p < 0.01). Parasympathetic reactivation and self-confidence were significantly lower in NightSA than in DaySA (p < 0.05). HR reactivity was decreased in NightVA in comparison to NightSA (p < 0.05). Overall, the rescue intervention had a greater impact on the psychophysiological variables during the night than during the day, and the type of alarm had a minor effect.

A cross-species neural integration of gravity for motor optimization.

Recent kinematic results, combined with model simulations, have provided support for the hypothesis that the human brain shapes motor patterns that use gravity effects to minimize muscle effort. Because many different muscular activation patterns can give rise to the same trajectory, here, we specifically investigate gravity-related movement properties by analyzing muscular activation patterns during single-degree-of-freedom arm movements in various directions. Using a well-known decomposition method of tonic and phasic electromyographic activities, we demonstrate that phasic electromyograms (EMGs) present systematic negative phases. This negativity reveals the optimal motor plan's neural signature, where the motor system harvests the mechanical effects of gravity to accelerate downward and decelerate upward movements, thereby saving muscle effort. We compare experimental findings in humans to monkeys, generalizing the Effort-optimization strategy across species.