Effect of photobiomodulation therapy on performance and running economy in runners: A randomized double-blinded placebo-controlled trial.

The objective of this study was to evaluate effects of photobiomodulation therapy (PBMT) on the 3000 m running performance (primary outcome), running economy (RE), metabolic cost and ratings of perceived exertion during running (secondary outcomes). Twenty male endurance athletes performed 4-min treadmill rectangular test at 12 km.h-1 monitored by a gas analyser. After that, PBMT or placebo in each lower limb was applied, followed performed a maximum test of 3000 m. Immediately after 3000 m test, the athletes repeated the treadmill test. Another application of PBMT/placebo was done after the treadmill test, and athletes went back to the laboratory 24 h later to repeat the treadmill test. After a 72 h interval, athletes repeated all procedures with another treatment intervention (PBMT/placebo). Athletes performed the 3000 m running test ~7s faster when treated with PBMT with similar effort score compared placebo condition. The RE remains unchanged immediately post 3000 m running test, nonetheless RE measured post-24 h improved by 5% with PBMT application without changes in metabolic cost. The PBMT pre- and post-conditioning enhanced the 3000 m running performance and improved RE 24 h following the 3000 m test. However, no changes on ratings of perceived exertion and metabolic cost with the application of PBMT.

Mobile telephone use effects on perception of verticality.

Low-level radiofrequency (RF) signals may produce disorientation and nausea. In experiment I, we assessed mobile phone effects on graviception in nine symptomatic subjects after mobile telephone use and 21 controls. The mobile handset was strapped to each ear for 30 min in pulsed emission, continuous RF emission, or no emission test mode, respectively. The subjective visual vertical and horizontal (SVV/SVH) were tested from min 25 of exposure. There was no exposure effect; however, there was an ear effect, with the SVV/SVH being shifted to the opposite direction of the ear exposed. This could be due to thermal or RF effects or handset weight. In experiment II, we assessed the handset weight effect on 18 normal controls. After baseline SVV/SVH, the switched off handset was strapped to either ear; the SVV/SVH was repeated 25 min later. A significant ear effect was found. We compared the observed ear effect SVV/SVH change in the experiment II group to the continuous exposure ear effect change in the experiment I group, and the difference was not significant. The ear effect was attributed to a minor head tilt due to the handset weight, or proprioceptive stimulation of neck muscle affecting the perception of verticality.

Experimental investigation of possible warmth perception from a head exposure system for human provocation studies with TETRA handset-like signals.

An experimental investigation of warming and warmth perception caused by handset EMF exposure was performed in order to examine its possible impact on blinding. Healthy male participants (15) were exposed to three different exposure conditions: sham and Terrestrial Trunked Radio (TETRA) handsets with maximum 10 g averaged SAR values of 1.5 and 6 W/kg each on three days. The study followed a randomized, double-blind design. TETRA signals simulated exposure from a handheld device consisting of a 385 MHz carrier modulated with a pulse length of 14.17 ms and a pulse period of 56.67 ms (i.e., duty cycle 25%; 17.65 Hz pulse modulation). A body worn antenna was used and fixed at the left ear. In addition to subjective ratings, skin temperatures at two locations close to the radiating element of the body-worn antenna were measured. The measurements revealed a temperature rise proportional to the supplied RF power with an average temperature increase measured at the two locations of 0.8 °C following the high exposure level of 6 W/kg. However, subjects were not able to distinguish between exposure conditions based on their subjective perception and thus the double-blinding was ensured.

Changes in swallowing physiology and patient perception of swallowing function following chemoradiation for head and neck cancer.

Patients treated with chemoradiation for head and neck cancer often report difficulty with swallowing and are frequently diagnosed with dysphagia. The extent to which patient awareness of dysphagia corresponds to observed physiologic changes in swallowing is unclear. The purpose of this study was to determine how both patient awareness of swallowing function and swallowing physiology individually change following chemoradiation and then to clarify the relationship between them. Twenty-one patients with head and neck cancer treated with chemoradiation were assessed before and after treatment and matched with twenty-one control subjects. The modified barium swallow test was utilized to examine swallowing physiology. Each subject was also given a series of items regarding awareness of specific dysphagia symptoms. Results showed decreased swallow efficiencies, higher percentages of residue, and more occurrences of penetration and aspiration following chemoradiation. Patients also had significantly higher ratings for 4 of the 12 items ("dry mouth," "food sticking in my mouth," "need water to help food go down," and "change in sense of taste"). Only one strong and significant correlation was found between ratings for "I have difficulty swallowing" and swallow efficiency values. Based on these findings, it appears that patients sense a general difficulty with swallowing but have less awareness of specific symptoms of dysphagia.

Perception of the electromagnetic field emitted by a mobile phone.

Electromagnetic sensibility refers to the ability to perceive the electromagnetic field (EMF) without necessarily developing health symptoms attributed to EMF exposure. A large sample of young healthy adults (n = 84) performed two forced-choice tasks on the perception of the GSM mobile phone EMF (902 MHz pulsed at 217 Hz), "Was the field on?" and "Did the field change?" (3 conditions x 100 trials for each task, n = 600 trials in total). A monetary prize was announced for good performance (correct response rate > or =75%, n = 600 trials). The performance was no better than expected by chance, and thus none of the participants won the prize. Two participants showed extraordinary performance in one of the task conditions ("Was the field on?", n = 100 trials), with correct response rates of 97% (P = 1.28 x 10(-25)) and 94% (P = 9.40 x 10(-22)), but they failed to replicate the result in the retest of six blocks of the same condition 1 month later. Six participants had reported being able to perceive the mobile phone EMF in the preliminary inquiry, but they performed no better than the others. This study provides empirical evidence against the existence of electromagnetic sensibility to the mobile phone EMF, demonstrating the necessity for replication in EMF studies.

Rats avoid high magnetic fields: dependence on an intact vestibular system.

High strength static magnetic fields are thought to be benign and largely undetectable by mammals. As magnetic resonance imaging (MRI) machines increase in strength, however, potential aversive effects may become clinically relevant. Here we report that rats find entry into a 14.1 T magnet aversive, and that they can detect and avoid entry into the magnet at a point where the magnetic field is 2 T or lower. Rats were trained to climb a ladder through the bore of a 14.1 T superconducting magnet. After their first climb into 14.1 T, most rats refused to re-enter the magnet or climb past the 2 T field line. This result was confirmed in a resistive magnet in which the magnetic field was varied from 1 to 14 T. Detection and avoidance required the vestibular apparatus of the inner ear, because labyrinthectomized rats readily traversed the magnet. The inner ear is a novel site for magnetic field transduction in mammals, but perturbation of the vestibular apparatus would be consistent with human reports of vertigo and nausea around high strength MRI machines.

Dissociable modulating effect of repetitive transcranial magnetic stimulation on sensory and pain perception.

The effects of high frequency repetitive transcranial magnetic stimulation on sensory perception and the pain tolerance thresholds were investigated applying both motor cortex stimulation and medial frontal cortex stimulation in normal study participants. Both the sensory perception and pain tolerance thresholds were significantly increased in the motor cortex stimulation, whereas the pain tolerance thresholds, but not the sensory perception was significantly decreased in the medial frontal cortex stimulation. These results suggest the dissociable modulating effects of sensory and pain perception by the high frequency repetitive transcranial magnetic stimulation on the medial pain regulating system, but not the lateral pain regulating system.

Pain relief by single low-level laser irradiation in orthodontic patients undergoing fixed appliance therapy.

INTRODUCTION: The objective of this study was to analyze the effect of single low-level laser therapy (LLLT) irradiation on pain perception in patients having fixed appliance treatment. METHODS: Seventy-six patients (46 women, 30 men; mean age, 23.1 years) enrolled in this single-blind study were assigned to 2 groups. The patients in group 1 (G1; 38 patients, 13 men, 25 women; mean age, 25.1 years) received a single course of LLLT (Mini Laser 2075, Helbo Photodynamic Systems GmbH & Co KG, Linz, Austria; wavelength 670 nm, power output 75 mW) for 30 seconds per banded tooth. The patients in group 2 (G2; 38 patients, 17 men, 21 women; mean age, 21.0 years) received placebo laser therapy without active laser irradiation. Pain perception was evaluated at 6, 30, and 54 hours after LLLT by self-rating with a standardized questionnaire. RESULTS: Major differences in pain perception were found between the 2 groups. The number of patients reporting pain at 6 hours was significantly lower in G1 (n = 14) than in G2 (n = 29) (P <.05), and the differences persisted at 30 hours (G1, n = 22; G2, n = 33) (P <.05). At 54 hours, no significant differences were seen between the number of patients reporting pain (G1, n = 20; G2, n = 25), although the women had a different prevalence between G1 (n = 11) and G2 (n = 15) (P = .079). At 6, 30, and 54 hours, more than 90% of the subjects in both groups described the pain as "tearing." CONCLUSIONS: LLLT immediately after multibanding reduced the prevalence of pain perception at 6 and 30 hours. LLLT might have positive effects in orthodontic patients not only immediately after multibanding, but also for preventing pain during treatment.

Electric current perception of the general population including children and the elderly.

Although the 50 Hz electric current perception threshold is a key parameter for limiting electric touch currents in electrical technology and for limiting indirect effects of external electromagnetic fields, the data available mainly reflect men's perception ability; with only sparse data for women and almost none for children or the elderly. Measurements with 240 children aged 9 - 16 years, and 123 elderly people, allow this gap of knowledge to be filled. Taking into account the demographic age distribution, it was possible to generate a probability distribution representing the perception ability of the overall general population, and thus to provide a more established basis for deriving safety limits. The results show that the existing limit values for electric touch currents are considerably too high if compared with results derived from the new data with the same criteria. On the other hand, it appeared that children do not exhibit such a high sensitivity to electricity as assumed to date. Therefore, former rule-of-thumb estimates to account for higher sensitivities of children lie on the safe side. The presented assessment of the general population's electric current perception ability should stimulate a critical review of the existing regulations.

Knowing each random error of our ways, but hardly correcting for it: an instance of optimal performance.

Random errors are omnipresent in sensorimotor tasks due to perceptual and motor noise. The question is, are humans aware of their random errors on an instance-by-instance basis? The appealing answer would be 'no' because it seems intuitive that humans would otherwise immediately correct for the errors online, thereby increasing sensorimotor precision. However, here we show the opposite. Participants pointed to visual targets with varying degree of feedback. After movement completion participants indicated whether they believed they landed left or right of target. Surprisingly, participants' left/right-discriminability was well above chance, even without visual feedback. Only when forced to correct for the error after movement completion did participants loose knowledge about the remaining error, indicating that random errors can only be accessed offline. When correcting, participants applied the optimal correction gain, a weighting factor between perceptual and motor noise, minimizing end-point variance. Together these results show that humans optimally combine direct information about sensorimotor noise in the system (the current random error), with indirect knowledge about the variance of the perceptual and motor noise distributions. Yet, they only appear to do so offline after movement completion, not while the movement is still in progress, suggesting that during movement proprioceptive information is less precise.

EHS subjects do not perceive RF EMF emitted from smart phones better than non-EHS subjects.

As the use of smart phones increases, social concerns have arisen concerning the possible effects of radio frequency-electromagnetic fields (RF-EMFs) emitted from wideband code division multiple access (WCDMA) mobile phones on human health. The number of people with self-reported electromagnetic hypersensitivity (EHS) who complain of various subjective symptoms, such as headache, insomnia, etc., has also recently increased. However, it is unclear whether EHS subjects can detect RF-EMFs exposure or not. In this double-blind study, two volunteer groups of 17 EHS and 20 non-EHS subjects were investigated in regards to their perception of RF-EMFs with real and sham exposure sessions. Experiments were conducted using a WCDMA module inside a dummy phone with an average power of 24 dBm at 1950 MHz and a specific absorption rate of 1.57 W/kg using a dummy headphone for 32 min. In conclusion, there was no indication that EHS subjects perceive RF-EMFs better than non-EHS subjects.

Can disordered radical pair systems provide a basis for a magnetic compass in animals?

A proposed mechanism for magnetic compasses in animals is that systems of radical pairs transduce magnetic field information to the nervous system. One can show that perfectly ordered arrays of radical pairs are sensitive to the direction of the external magnetic field and can thus operate, in principle, as a magnetic compass. Here, we investigate how disorder, inherent in biological cells, affects the ability of radical pair systems to provide directional information. We consider biologically inspired geometrical arrangements of ensembles of radical pairs with increasing amounts of disorder and calculate the effect of changing the direction of the external magnetic field on the rate of chemical signal production by radical pair systems. Using a previously established signal transduction model, we estimate the minimum number of receptors necessary to allow for detection of the change in chemical signal owing to changes in magnetic field direction. We quantify the required increase in the number of receptors to compensate for the signal attenuation through increased disorder. We find radical-pair-based compass systems to be relatively robust against disorder, suggesting several scenarios as to how a compass structure can be realized in a biological cell.

Cryptochromes--a potential magnetoreceptor: what do we know and what do we want to know?

Cryptochromes have been suggested to be the primary magnetoreceptor molecules underlying light-dependent magnetic compass detection in migratory birds. Here we review and evaluate (i) what is known about these candidate magnetoreceptor molecules, (ii) what characteristics cryptochrome molecules must fulfil to possibly underlie light-dependent, radical pair based magnetoreception, (iii) what evidence supports the involvement of cryptochromes in magnetoreception, and (iv) what needs to be addressed in future research. The review focuses primarily on our knowledge of cryptochromes in the context of magnetoreception.

A quantitative assessment of torque-transducer models for magnetoreception.

Although ferrimagnetic material appears suitable as a basis of magnetic field perception in animals, it is not known by which mechanism magnetic particles may transduce the magnetic field into a nerve signal. Provided that magnetic particles have remanence or anisotropic magnetic susceptibility, an external magnetic field will exert a torque and may physically twist them. Several models of such biological magnetic-torque transducers on the basis of magnetite have been proposed in the literature. We analyse from first principles the conditions under which they are viable. Models based on biogenic single-domain magnetite prove both effective and efficient, irrespective of whether the magnetic structure is coupled to mechanosensitive ion channels or to an indirect transduction pathway that exploits the strayfield produced by the magnetic structure at different field orientations. On the other hand, torque-detector models that are based on magnetic multi-domain particles in the vestibular organs turn out to be ineffective. Also, we provide a generic classification scheme of torque transducers in terms of axial or polar output, within which we discuss the results from behavioural experiments conducted under altered field conditions or with pulsed fields. We find that the common assertion that a magnetoreceptor based on single-domain magnetite could not form the basis for an inclination compass does not always hold.

Magnetoreception in eusocial insects: an update.

Behavioural experiments for magnetoreception in eusocial insects in the last decade are reviewed. Ants and bees use the geomagnetic field to orient and navigate in areas around their nests and along migratory paths. Bees show sensitivity to small changes in magnetic fields in conditioning experiments and when exiting the hive. For the first time, the magnetic properties of the nanoparticles found in eusocial insects, obtained by magnetic techniques and electron microscopy, are reviewed. Different magnetic oxide nanoparticles, ranging from superparamagnetic to multi-domain particles, were observed in all body parts, but greater relative concentrations in the abdomens and antennae of honeybees and ants have focused attention on these segments. Theoretical models for how these specific magnetosensory apparatuses function have been proposed. Neuron-rich ant antennae may be the most amenable to discovering a magnetosensor that will greatly assist research into higher order processing of magnetic information. The ferromagnetic hypothesis is believed to apply to eusocial insects, but interest in a light-sensitive mechanism is growing. The diversity of compass mechanisms in animals suggests that multiple compasses may function in insect orientation and navigation. The search for magnetic compasses will continue even after a magnetosensor is discovered in eusocial insects.

Photoreceptor-based magnetoreception: optimal design of receptor molecules, cells, and neuronal processing.

The sensory basis of magnetoreception in animals still remains a mystery. One hypothesis of magnetoreception is that photochemical radical pair reactions can transduce magnetic information in specialized photoreceptor cells, possibly involving the photoreceptor molecule cryptochrome. This hypothesis triggered a considerable amount of research in the past decade. Here, we present an updated picture of the radical-pair photoreceptor hypothesis. In our review, we will focus on insights that can assist biologists in their search for the elusive magnetoreceptors.

Directional orientation of birds by the magnetic field under different light conditions.

This paper reviews the directional orientation of birds with the help of the geomagnetic field under various light conditions. Two fundamentally different types of response can be distinguished. (i) Compass orientation controlled by the inclination compass that allows birds to locate courses of different origin. This is restricted to a narrow functional window around the total intensity of the local geomagnetic field and requires light from the short-wavelength part of the spectrum. The compass is based on radical-pair processes in the right eye; magnetite-based receptors in the beak are not involved. Compass orientation is observed under 'white' and low-level monochromatic light from ultraviolet (UV) to about 565 nm green light. (ii) 'Fixed direction' responses occur under artificial light conditions such as more intense monochromatic light, when 590 nm yellow light is added to short-wavelength light, and in total darkness. The manifestation of these responses depends on the ambient light regime and is 'fixed' in the sense of not showing the normal change between spring and autumn; their biological significance is unclear. In contrast to compass orientation, fixed-direction responses are polar magnetic responses and occur within a wide range of magnetic intensities. They are disrupted by local anaesthesia of the upper beak, which indicates that the respective magnetic information is mediated by iron-based receptors located there. The influence of light conditions on the two types of response suggests complex interactions between magnetoreceptors in the right eye, those in the upper beak and the visual system.

Light-dependent magnetic compass orientation in amphibians and insects: candidate receptors and candidate molecular mechanisms.

Magnetic compass orientation by amphibians, and some insects, is mediated by a light-dependent magnetoreception mechanism. Cryptochrome photopigments, best known for their role in circadian rhythms, are proposed to mediate such responses. In this paper, we explore light-dependent properties of magnetic sensing at three levels: (i) behavioural (wavelength-dependent effects of light on magnetic compass orientation), (ii) physiological (photoreceptors/photopigment systems with properties suggesting a role in magnetoreception), and (iii) molecular (cryptochrome-based and non-cryptochrome-based signalling pathways that are compatible with behavioural responses). Our goal is to identify photoreceptors and signalling pathways that are likely to play a specialized role in magnetoreception in order to definitively answer the question of whether the effects of light on magnetic compass orientation are mediated by a light-dependent magnetoreception mechanism, or instead are due to input from a non-light-dependent (e.g. magnetite-based) magnetoreception mechanism that secondarily interacts with other light-dependent processes.

Avian magnetite-based magnetoreception: a physiologist's perspective.

It is now well established that animals use the Earth's magnetic field to perform long-distance migration and other navigational tasks. However, the transduction mechanisms that allow the conversion of magnetic field variations into an electric signal by specialized sensory cells remain largely unknown. Among the species that have been shown to sense Earth-strength magnetic fields, birds have been a model of choice since behavioural tests show that their direction-finding abilities are strongly influenced by magnetic fields. Magnetite, a ferromagnetic mineral, has been found in a wide range of organisms, from bacteria to vertebrates. In birds, both superparamagnetic (SPM) and single-domain magnetite have been found to be associated with the trigeminal nerve. Electrophysiological recordings from cells in the trigeminal ganglion have shown an increase in action potential firing in response to magnetic field changes. More recently, histological evidence has demonstrated the presence of SPM magnetite in the subcutis of the pigeon's upper beak. The aims of the present review are to review the evidence for a magnetite-based mechanism in birds and to introduce physiological concepts in order to refine the proposed models.

Biophysics of magnetic orientation: strengthening the interface between theory and experimental design.

The first demonstrations of magnetic effects on the behaviour of migratory birds and homing pigeons in laboratory and field experiments, respectively, provided evidence for the longstanding hypothesis that animals such as birds that migrate and home over long distances would benefit from possession of a magnetic sense. Subsequent identification of at least two plausible biophysical mechanisms for magnetoreception in animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, led to major efforts over recent decades to test predictions of the two models, as well as efforts to understand the ultrastructure and function of the possible magnetoreceptor cells. Unfortunately, progress in understanding the magnetic sense has been challenged by: (i) the availability of a relatively small number of techniques for analysing behavioural responses to magnetic fields by animals; (ii) difficulty in achieving reproducible results using the techniques; and (iii) difficulty in development and implementation of new techniques that might bring greater experimental power. As a consequence, laboratory and field techniques used to study the magnetic sense today remain substantially unchanged, despite the huge developments in technology and instrumentation since the techniques were developed in the 1950s. New methods developed for behavioural study of the magnetic sense over the last 30 years include the use of laboratory conditioning techniques and tracking devices based on transmission of radio signals to and from satellites. Here we consider methodological developments in the study of the magnetic sense and present suggestions for increasing the reproducibility and ease of interpretation of experimental studies. We recommend that future experiments invest more effort in automating control of experiments and data capture, control of stimulation and full blinding of experiments in the rare cases where automation is impossible. We also propose new experiments to confirm whether or not animals can detect magnetic fields using the radical-pair effect together with an alternate hypothesis that may explain the dependence on light of responses by animals to magnetic field stimuli.