How low can you go? Measuring human event-related brain potentials from a two-channel EEG system.

Over the past ten years, there has been a rapid increase in the availability and use of mobile electroencephalography (mEEG) in research. Indeed, researchers using mEEG have recorded EEG and event-related brain potentials in a wide range of environments - for example, while walking (Debener et al., 2012), riding a bike (Scanlon et al., 2020), or even in a shopping mall (Krigolson et al., 2021). However, given that low-cost, ease-of-use, and setup speed provide the primary advantages of an mEEG system over large array traditional EEG systems, an important and unresolved question is just how many electrodes does an mEEG system need to collect research-quality EEG data? Here, we tested whether or not a two-channel forehead-mounted mEEG system - the "Patch" - could measure event-related brain potentials within their established amplitude and latency characteristics (Luck, 2014). In the present study, participants performed a visual oddball task while we recorded EEG data from the Patch. Our results demonstrated that we could capture and quantify the N200 and P300 event-related brain potential components using a minimal electrode array forehead-mounted EEG system. Our data further support the idea that mEEG can be used for quick and rapid EEG-based assessments, such as measuring the impact of concussions on the sports field (Fickling et al., 2021) or assessing the impact of stroke severity in a hospital (Wilkinson et al., 2020).

Exercising is good for the brain but exercising outside is potentially better.

It is well known that exercise increases cognitive function. However, the environment in which the exercise is performed may be just as important as the exercise itself. Time spent in natural outdoor environments has been found to lead to increases in cognition similar to those resulting from acute exercise. Therefore, the benefits of both exercise and nature exposure suggest an additive impact on brain function when both factors are combined. This raises the question: what is the interaction between acute exercise and environment on cognition? We answered this question using electroencephalography to probe cognitive function using the oddball task before and after brief indoor and outdoor walks on 30 participants (average 21 years old, 95% CI [20, 22]). Our results demonstrate improved performance and an increase in the amplitude of the P300, an event-related neural response commonly associated with attention and working memory, following a 15-min walk outside; a result not seen following a 15-min walk inside. Importantly, this finding indicates that the environment may play a more substantial role in increasing cognitive function such as attention than exercise, at least in terms of acute exercise (i.e., a brief walk). With the world's growing urbanization and the associated increase in sedentary time indoors, a deeper understanding of how these factors interact and influence cognition may be critical to combat adverse health effects.

Using Muse: Rapid Mobile Assessment of Brain Performance.

The advent of mobile electroencephalography (mEEG) has created a means for large scale collection of neural data thus affording a deeper insight into cognitive phenomena such as cognitive fatigue. Cognitive fatigue - a neural state that is associated with an increased incidence of errorful performance - is responsible for accidents on a daily basis which at times can cost human lives. To gain better insight into the neural signature of cognitive fatigue in the present study we used mEEG to examine the relationship between perceived cognitive fatigue and human-event related brain potentials (ERPs) and electroencephalographic (EEG) oscillations in a sample of 1,000 people. As a secondary goal, we wanted to further demonstrate the capability of mEEG to accurately measure ERP and EEG data. To accomplish these goals, participants performed a standard visual oddball task on an Apple iPad while EEG data were recorded from a Muse EEG headband. Counter to traditional EEG studies, experimental setup and data collection was completed in less than seven minutes on average. An analysis of our EEG data revealed robust N200 and P300 ERP components and neural oscillations in the delta, theta, alpha, and beta bands. In line with previous findings we observed correlations between ERP components and EEG power and perceived cognitive fatigue. Further, we demonstrate here that a linear combination of ERP and EEG features is a significantly better predictor of perceived cognitive fatigue than any ERP or EEG feature on its own. In sum, our results provide validation of mEEG as a viable tool for research and provide further insight into the impact of cognitive fatigue on the human brain.

Influence of iron manipulation on hypoxic pulmonary vasoconstriction and pulmonary reactivity during ascent and acclimatization to 5050 m.

KEY POINTS: Iron acts as a cofactor in the stabilization of the hypoxic-inducible factor family, and plays an influential role in the modulation of hypoxic pulmonary vasoconstriction. It is uncertain whether iron regulation is altered in lowlanders during either (1) ascent to high altitude, or (2) following partial acclimatization, when compared to high-altitude adapted Sherpa. During ascent to 5050 m, the rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders; however, upon arrival to 5050 m, PASP levels were comparable in both groups, but the reduction in iron bioavailability was more prevalent in lowlanders compared to Sherpa. Following partial acclimatization to 5050 m, there were differential influences of iron status manipulation (via iron infusion or chelation) at rest and during exercise between lowlanders and Sherpa on the pulmonary vasculature. ABSTRACT: To examine the adaptational role of iron bioavailability on the pulmonary vascular responses to acute and chronic hypobaric hypoxia, the haematological and cardiopulmonary profile of lowlanders and Sherpa were determined during: (1) a 9-day ascent to 5050 m (20 lowlanders; 12 Sherpa), and (2) following partial acclimatization (11 ± 4 days) to 5050 m (18 lowlanders; 20 Sherpa), where both groups received an i.v. infusion of either iron (iron (iii)-hydroxide sucrose) or an iron chelator (desferrioxamine). During ascent, there were reductions in iron status in both lowlanders and Sherpa; however, Sherpa appeared to demonstrate a more efficient capacity to mobilize stored iron, compared to lowlanders, when expressed as a Δhepcidin per unit change in either body iron or the soluble transferrin receptor index, between 3400-5050 m (P = 0.016 and P = 0.029, respectively). The rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders during ascent; however, PASP was comparable in both groups upon arrival to 5050 m. Following partial acclimatization, despite Sherpa demonstrating a blunted hypoxic ventilatory response and greater resting hypoxaemia, they had similar hypoxic pulmonary vasoconstriction when compared to lowlanders at rest. Iron-infusion attenuated PASP in both groups at rest (P = 0.005), while chelation did not exaggerate PASP in either group at rest or during exaggerated hypoxaemia ( PIO2  = 67 mmHg). During exercise at 25% peak wattage, PASP was only consistently elevated in Sherpa, which persisted following both iron infusion or chelation. These findings provide new evidence on the complex interplay of iron regulation on pulmonary vascular regulation during acclimatization and adaptation to high altitude.

Distribution of Practice Combined with Observational Learning Has Time Dependent Effects on Motor Skill Acquisition.

Studies of the benefits of a distributed practice schedule on motor skill acquisition have typically found that distribution of practice results in better learning. However, less research has focused on how the benefits of distributed practice are impacted by timing during acquisition. To examine how timing of skill acquisition interacts with distribution of practice we had two groups of participants complete either an extensive massed or distributed training schedule to learn a speed stacking sequence across ten sessions. For participants in both groups, we provided observational learning to facilitate skill acquisition. Analysis of speed stacking time on a retention test revealed an overall benefit for the distributed relative to the massed practice group. Interestingly, our analysis of the benefits of distributed practice during training only showed performance benefits in the early session (session one) and later sessions (sessions eight, nine, and ten) of skill acquisition but not mid-way through it (sessions two through seven). Our results support previous findings highlighting the learning benefits of a distributed practice schedule but suggest that these benefits occur differentially throughout acquisition. Our work also replicates research demonstrating that observational learning is more beneficial when it is yoked to actual practice.

The impact of wellness on neural learning systems.

Over the past 20 years there has been an increasing push for people to achieve or maintain "wellness" - a state in which one has not only physical but also mental and social well-being. While it may seem obvious that maintaining a state of wellness is beneficial, little research has been done to probe how maintaining a state of wellness impacts our brain. Here, we specifically examined the impact of wellness on a neural system within the medial-frontal cortex responsible for human reinforcement learning. Sixty-two undergraduate students completed the Perceived Wellness Survey after which they completed a computer-based learnable gambling game while electroencephalographic data were recorded. Within the game, participants were presented with a series of choices that either led to financial gains or losses. An analysis of our behavioral data indicated that participants were able to learn the underlying structure of the gambling game given that we observed improvements in performance. Concurrent with this, we observed an electroencephalographic response evoked by the evaluation of gambling outcomes - the reward positivity. Importantly, we found significant relationships between several aspects of wellness and the amplitude of the reward positivity. Given that the reward positivity is thought to reflect the function of a reinforcement learning system within the medial-frontal cortex, our results suggest that wellness impacts neural function - in this instance one of the systems responsible for human learning.

Vision facilitates tactile perception when grasping an object.

Tactile sensitivity measured on the hand is significantly decreased for a moving (MH), as opposed to a resting hand (RH). This process (i.e., tactile suppression) is affected by the availability of visual information during goal-directed action. However, the timing of the contribution of visual information is currently unclear for reach-to-grasp movements, especially in the period before the digits land on the object to grasp it. Here participants reached for, grasped, and lifted an object placed in front of them in conditions of full/limited vision. Tactile perception was assessed by measures of signal detection theory (d' & c'). Electro-cutaneous stimulation could be delivered/not at the MH/RH, either during movement preparation, execution, before grasping, or while lifting the object. Results confirm tactile gating at the MH. This result is accompanied by a significant conservative criterion shift at the MH for the latter movement stages. Importantly, visual information enhances MH sensitivity just before grasping the object, but also improves RH sensitivity, during object lift. These findings reveal that tactile suppression is shaped by visual inputs at critical action stages. Further, they indicate that such a time-dependent modulation from vision to touch extends beyond the MH, suggesting a dynamic monitoring of the grasp space.

Chasing the zone: Reduced beta power predicts baseball batting performance.

Mental state prior to sports skill execution is related to subsequent performance. For example, relationships between pre-performance electroencephalogram (EEG) power and subsequent movement outcomes in golf putting, pistol shooting, and basketball free throw shooting have been previously reported. With that said, the existing body of research examining the pre-performance EEG - performance relationship has been focused on the execution of internally as opposed to externally-paced motor skills. Given that the execution of internally and externally-paced movements are dependent on different neural pathways, in the present study we examined whether or not pre-performance EEG power predicted ensuing performance of an externally-paced motor skill - baseball batting. Sixty-seven baseball players had EEG data recorded for 120 s prior to batting practice. Performance was assessed by three expert coaches and the accuracy of coach performance ratings was verified via Generalizability Theory. An analysis of our data revealed an inverse relationship between frontal EEG power in the beta range and subsequent batting performance - reduced beta power was associated with better batting performance whereas increased beta power was associated with worse batting performance. Our results are in line with prior research that has demonstrated a relationship between increased EEG power in the beta range and the subsequent commitment of motor errors in addition to the aforementioned work examining pre-performance EEG and the execution of internally-paced motor skills.

Hand anthropometry and the limits of aperture separation determine the utility of Weber's law in grasping and manual estimation.

Recent work proposed that biomechanical constraints in aperture separation limit the utility of Weber's law in determining whether dissociable visual codes support grasping and manual estimation. We tested this assertion by having participants precision grasp, manually estimate and complete a method of adjustment task to targets scaled within and beyond the range of their maximal aperture separation (i.e., from 20 to 140% of participant-specific maximal aperture separation: MAS). For grasping and manual estimation tasks, just-noticeable-difference (JND) scores were computed via the within-participant standard deviations in peak grip aperture, whereas method of adjustment JNDs were computed via the within-participant standard deviations in response output. Method of adjustment JNDs increased linearly across the range of targets; that is, responses adhered to Weber's law. Manual estimation JNDs linearly increased for targets 20-100% of MAS and then decreased for targets 120-140% of MAS. In turn, grasping JNDs for targets 20% through 80% of MAS did not differ and were larger than targets 100-140% of MAS. That manual estimation and grasping showed a decrease in JNDs for the largest targets indicates that participants were at their biomechanical limits in aperture shaping, and the fact that the target showing the JND decrease differed between tasks (i.e., manual estimation = 100% of MAS; grasping = 80% of MAS) is attributed to the fact that grasping-but not manual estimation-requires a safety-margin task-set. Accordingly, manual estimations and grasping across a range of functionally 'graspable' targets, respectively, adhered to and violated Weber's law-a result interpreted to reflect the use of dissociable visual codes.

Tactile suppression in goal-directed movement.

Sharing numerous characteristics with suppression in the other senses, tactile suppression is a reliable phenomenon that accompanies movement. By investigating the simplest of movements (e.g., finger flexions), early research tried to explain the origins of the phenomenon in terms of motor command generation together with sensory reafference. Here, we review recent research that has delved into (naturalistic) goal-directed movements. In connection with goal-directed movement, tactile suppression is evident as a decrease in behavioural performance measured shortly prior to, and during, movement execution. It is also reflected in a consistent response bias highlighting the (perceptual) uncertainty of the movement. Goal-directed movement supports the forward model and establishes contextual influences as the defining influences on tactile suppression. Depending on the task at hand, people prioritize a certain percept during movement. Future research, we argue, should focus on studying naturalistic movements, or sequences of movements, that share a common meaning or goal.

Motor Planning Influences the Perceived Timing of Vibrotactile Stimuli in an Amplitude-Dependent Manner.

The authors characterized how motor planning influences temporal order judgment (TOJ) tasks. They examined this by applying vibrotactile stimulation during the planning stages of a bimanual arm movement that would bring the arms into a crossed configuration. The authors have previously shown that planning to cross the arms induces a subjective reversal of spatially defined temporal order judgments that evolves over the course of the planning period. It was unclear, however, whether this effect is modulated by the extent to which the arms would be crossed after movement. The authors examined this issue by having participants plan to move to 4 different targets that would leave the arms in crossed configurations of varying extents. The results demonstrate that even though cutaneous stimuli were applied before the movements, if participants were planning to move into a more crossed configuration, performance on the TOJ task worsened depending on where they were in the planning process. This data suggest the brain uses planning signals to predict sensations from impending movements in a context-dependent manner.

Availability of vision and tactile gating: vision enhances tactile sensitivity.

A multitude of events bombard our sensory systems at every moment of our lives. Thus, it is important for the sensory and motor cortices to gate unimportant events. Tactile suppression is a well-known phenomenon defined as a reduced ability to detect tactile events on the skin before and during movement. Previous experiments (Buckingham et al. in Exp Brain Res 201(3):411-419, 2010; Colino et al. in Physiol Rep 2(3):e00267, 2014) found detection rates decrease just prior to and during finger abduction and decrease according to the proximity of the moving effector. However, what effect does vision have on tactile gating? There is ample evidence (see Serino and Haggard in Neurosci Biobehav Rev 34:224-236, 2010) observing increased tactile acuity when participants see their limbs. The present study examined how tactile detection changes in response to visual condition (vision/no vision). Ten human participants used their right hand to reach and grasp a cylinder. Tactors were attached to the index finger and the forearm of both the right and left arm and vibrated at various epochs relative to a "go" tone. Results replicate previous findings from our laboratory (Colino et al. in Physiol Rep 2(3):e00267, 2014). Also, tactile acuity decreased when participants did not have vision. These results indicate that the vision affects the somatosensation via inputs from parietal areas (Konen and Haggard in Cereb Cortex 24(2):501-507, 2014) but does so in a reach-to-grasp context.

Time Course of Tactile Gating in a Reach-to-Grasp and Lift Task.

Humans' sensory systems are bombarded by myriad events every moment of our lives. Thus, it is crucial for sensory systems to choose and process critical sensory events deemed important for a given task and, indeed, those that affect survival. Tactile gating is well known, and defined as a reduced ability to detect and discriminate tactile events before and during movement. Also, different locations of the effector exhibit different magnitudes of sensitivity changes. The authors examined that time course of tactile gating in a reaching and grasping movement to characterize its behavior. Tactile stimulators were attached to the right and left mid-forearms and the right index finger and fifth digit. When participants performed reach-to-grasp and lift targets, tactile acuity decreased at the right forearm before movement onset (F. L. Colino, G. Buckingham, D. T. Cheng, P. van Donkelaar, & G. Binsted, 2014 ). However, tactile sensitivity at the right index finger decreased by nearly 20% contrary to expectations. This result reflecting that there may be an additional source acting to reduce inhibition related to tactile gating. Additionally, sensitivity improved as movement end approached. Collectively, the present results indicate that predictive and postdictive mechanisms strongly influence tactile gating.

Tactile gating in a reaching and grasping task.

Abstract A multitude of events bombard our sensory systems at every moment of our lives. Thus, it is important for the sensory cortex to gate unimportant events. Tactile suppression is a well-known phenomenon defined as a reduced ability to detect tactile events on the skin before and during movement. Previous experiments found detection rates decrease just prior to and during finger abduction, and decrease according to the proximity of the moving effector. This study examined how tactile detection changes during a reach to grasp. Fourteen human participants used their right hand to reach and grasp a cylinder. Tactors were attached to the index finger, the fifth digit, and the forearm of both the right and left arm and vibrated at various epochs relative to a "go" tone. Results showed that detection rates at the forearm decreased before movement onset; whereas at the right index finger, right fifth digit and at the left index finger, left fifth digit, and forearm sites did not decrease like in the right forearm. These results indicate that the task affects gating dynamics in a temporally- and contextually dependent manner and implies that feed-forward motor planning processes can modify sensory signals.

Explicit knowledge and real-time action control: anticipating a change does not make us respond more quickly.

When the target of a goal-directed reach changes location, people normally respond rapidly and automatically to the target shift. Here, we investigate whether explicit knowledge about a moving target (knowing whether a location change is likely/unlikely) improves responsiveness, with the goal of understanding top-down effects on real-time reaching. In Experiment 1, we presented participants with pre-cues that indicated a 20 or 80% likelihood of a target perturbation on that trial. When participants made pro-pointing responses to the target perturbations, their online response occurred later for 20% trials than for 80% trials, but this effect may have been due to suppression of the online response on 20% trials, rather than enhancement of the response on 80% trials. In Experiment 2, we presented participants with 50 and 100% likelihood pre-cues, and observed no shortening of the latency on 100% trials compared to 50% trials, which suggests that expectation does not enhance the automatic response to a perturbation. However, we did observe more vigorous responses to the perturbation on the 100% trials, and this contributed to shorter movement times relative to the 50% trials. We also examined, in Experiment 2, whether prior knowledge about the direction of the target perturbation would shorten the latency of the online response, but we did not observe any reduction in latency. In sum, the onset of the automatic response appears to be suppressible, but not augmentable by top-down input. The possibility that the forcefulness of the automatic response is modifiable by expectation is examined, but not resolved.

Grasping time does not influence the early adherence of aperture shaping to Weber's law.

The "just noticeable difference" (JND) represents the minimum amount by which a stimulus must change to produce a noticeable variation in one's perceptual experience (i.e., Weber's law). Recent work has shown that within-participant standard deviations of grip aperture (i.e., JNDs) increase linearly with increasing object size during the early, but not the late, stages of goal-directed grasping. A visually based explanation for this finding is that the early and late stages of grasping are respectively mediated by relative and absolute visual information and therefore render a time-dependent adherence to Weber's law. Alternatively, a motor-based explanation contends that the larger aperture shaping impulses required for larger objects gives rise to a stochastic increase in the variability of motor output (i.e., impulse-variability hypothesis). To test the second explanation, we had participants grasp differently sized objects in grasping time criteria of 400 and 800 ms. Thus, the 400 ms condition required larger aperture shaping impulses than the 800 ms condition. In line with previous work, JNDs during early aperture shaping (i.e., at the time of peak aperture acceleration and peak aperture velocity) for both the 400 and 800 ms conditions scaled linearly with object size, whereas JNDs later in the response (i.e., at the time of peak grip aperture) did not. Moreover, the 400 and 800 ms conditions produced comparable slopes relating JNDs to object size. In other words, larger aperture shaping impulses did not give rise to a stochastic increase in aperture variability at each object size. As such, the theoretical tenets of the impulse-variability hypothesis do not provide a viable framework for the time-dependent scaling of JNDs to object size. Instead, we propose that a dynamic interplay between relative and absolute visual information gives rise to grasp trajectories that exhibit an early adherence and late violation to Weber's law.

Influence of posture on the regulation of cerebral perfusion.

BACKGROUND: Posture has a major influence on cerebral blood flow (CBF). Unlike head-up tilt (HUT), less is known about how CBF is regulated during head-down tilt (HDT). We hypothesized that CBF would be elevated during HDT and decreased during HUT. METHODS: In 21 healthy young adults, while controlling for end-tidal Pco2, we combined concurrent measurements of middle cerebral artery velocity and posterior cerebral artery velocity (MCAv and PCAv, respectively), blood pressure (BP), and heart rate (HR). Measures were made at rest and, in a randomized order, during -90 degrees HDT and +900 HUT. Dynamic cerebral autoregulation was quantified using transfer function analysis. In a subgroup, volumetric blood flow recordings were obtained in the common carotid artery (CCA; N=11), internal and external carotid arteries (ICA; N=8 and ECA; N=6), and vertebral artery (VA; N=4). RESULTS: End-tidal Pco2, CCA, ICA, VA, MCAv(mean) and PCAv(mean) remained unchanged during -90 degrees HDT and +90 degrees HUT compared to supine. During -90 degrees HDT, mean BP (+22 mmHg) and cerebral vascular resistance (CVR) in both the MCA and PCA were elevated relative to supine, whereas HR remained unchanged. During +900 HUT, when compared to supine, HR increased (+18 bpm), and mean arterial pressure (MAP) total power and low frequency (LF) power in the MCA and PCA increased. In both the very low frequency (VLF) and LF ranges, coherence during +90 degrees HUT increased (P < 0.05 vs. supine) in both the MCA and PCA. In contrast, coherence was reduced during -90 degrees HDT. DISCUSSION: Despite marked changes in perfusion pressure with HUT or HDT, our findings indicate that cerebral perfusion is well maintained during acute severe changes in posture.

Factors that affect action possibility judgements: recent experience with the action and the current body state.

It has been suggested that action possibility judgements are formed through a covert simulation of the to-be-executed action. We sought to determine whether the motor system (via a common coding mechanism) influences this simulation, by investigating whether action possibility judgements are influenced by experience with the movement task (Experiments 1 and 2) and current body states (Experiment 3). The judgement task in each experiment involved judging whether it was possible for a person's hand to accurately move between two targets at presented speeds. In Experiment 1, participants completed the action judgements before and after executing the movement they were required to judge. Results were that judged movement times after execution were closer to the actual execution time than those prior to execution. The results of Experiment 2 suggest that the effects of execution on judgements were not due to motor activation or perceptual task experience-alternative explanations of the execution-mediated judgement effects. Experiment 3 examined how judged movement times were influenced by participants wearing weights. Results revealed that wearing weights increased judged movement times. These results suggest that the simulation underlying the judgement process is connected to the motor system, and that simulations are dynamically generated, taking into account recent experience and current body state.

Preceding movement effects on sequential aiming.

In this study, two experiments were devised to examine the control strategy used by individuals when performing sequential aiming movements. Of particular interest was the aiming behavior displayed when task difficulty was changed midway through a sequence of movements. In Experiment 1, target size was manipulated, as the targets were made either larger or smaller, between the 8th and 12th movement of the sequence. In Experiment 2, the amplitude between the two targets was similarly changed while the target size remained constant. Results revealed that in Experiment 1, individuals took two movements following the perturbation to target size, to re-tune their movement times in order to correspond with the new task difficulty. Conversely for Experiment 2, movement time changed immediately and in correspondence with the new target amplitude. These findings demonstrate that participants can use information from the preceding movement to prepare and guide subsequent movements--but only when target size is changed. When response amplitude changes mid-sequence, it seems individuals rely more on immediate, target-derived information. Therefore, counter to some current accounts of visual movement control, it appears that memory representations of the preceding movement can guide subsequent movements; however, this information appears selectively accessed in a context-dependent fashion.

Changing the sheets: a new system to reduce strain during patient repositioning.

BACKGROUND: Manually repositioning patients puts healthcare providers at risk for injury; this may be reduced by using low-friction bedsheets. OBJECTIVES: The aim of this study was to evaluate the physical properties and the physiological measures of muscle activity and perceptual participant accounts between a new slider sheet system and traditional hospital bedsheet makeup (soaker pad with a jersey bottom sheet). METHOD: Surface electromyography was recorded from the arm and shoulder muscles of five healthcare providers executing a patient repositioning (boosting and turning) in a controlled laboratory setting to gain an indication of muscle activity required for two types of bedsheets (slider system and traditional sheet makeup). The Borg Scale was used to establish rating of perceived exertion for these repositioning tasks on the two types of bedsheet makeup. To evaluate the sheets independent of human interaction and contact, the physical resistive characteristics of the sheets were calculated by determining the coefficient of friction. RESULTS: Patient repositioning on traditional sheets, compared with the slider system, resulted in 16% greater electromyography burst numbers and 11% longer duration for both boosting and turning. Moreover, ratings of perceived exertion for repositioning patients on traditional sheets versus on slider sheets were more than double. The coefficient of friction of the traditional sheets was 65% less in the slider sheet system. DISCUSSION: This study suggests that manually repositioning patients on a low-friction slider system reduces muscular and perceived effort. Proper usage of this type of bedsheets may reduce the risks associated with musculoskeletal strain and injuries of the healthcare providers.