Body ownership and a new proprioceptive role for muscle spindles.

Knowledge of which body parts belong to us is referred to as the sense of body ownership. There is increasing evidence that this important aspect of human proprioception is highly malleable. Research into ownership of individual body parts was stimulated by Botvinick and Cohen's rubber-hand illusion (Nature 391,1998, 756), which demonstrated that an artificial body part can be incorporated in one's body representation and can cause real body parts to be sensed erroneously. Here, we review key studies that have advanced our understanding of the sense of body ownership, including the important role played by multisensory integration and spatiotemporal congruence of sensory signals. We also discuss our recent discovery that body ownership can be induced in response to movement stimuli by signals from a single class of sensory receptor, namely muscle spindles.

[Disparity on the grade of exposure to ecological risks in the European region of WHO].

Disparity in relation of ecological conditions and health concerns to the general differences in environmental conditions and in large extent is stipulated by socio-economic and demographic differences in the impact of its hazards. In addition to differences in the impact the inequality in relation of ecological conditions and health can also be caused by social or demographic differences in exposure to certain risks. This article offers an assessment of the evidence and data on differences in the impact of the environment in the European Region of the World Health Organization (WHO) received during the recent work of the European Regional Office of WHO. The obtained results testify that socio-demographic disparity in the impact of the environment exists in all countries. Such inequality can be seen in respect of a variety offactors, such as age, gender income level, or on the contrary, poverty, education and employment, household type, location of the home.

The IVAIRE project--a randomized controlled study of the impact of ventilation on indoor air quality and the respiratory symptoms of asthmatic children in single family homes.

UNLABELLED: A randomized controlled trial was carried out to measure the impact of an intervention on ventilation, indoor air contaminants, and asthma symptoms of children. Eighty-three asthmatic children living in low-ventilated homes were followed over 2 years. Several environmental parameters were measured during the summer, fall, and winter. The children were randomized after Year 1 (43 Intervention; 40 Control). The intervention included the installation of either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). During the fall and winter seasons, there was a significant increase in the mean ventilation rate in the homes of the intervention group. A statistically significant reduction in mean formaldehyde, airborne mold spores, toluene, styrene, limonene, and α-pinene concentrations was observed in the intervention group. There was no significant group difference in change in the number of days with symptoms per 14 days. However, there was a significant decrease in the proportion of children who experienced any wheezing (≥1 episode) and those with ≥4 episodes in the 12-month period in the intervention group. This study indicates that improved ventilation reduces air contaminants and may prevent wheezing. Due to lack of power, a bigger study is needed. PRACTICAL IMPLICATIONS: Positive findings from this study include the fact that, upon recruitment, most of the single family homes with asthmatic children were already equipped with a mechanical ventilation system and had relatively good indoor air quality. However, the 8-h indoor guideline for formaldehyde (50 µg/m3) was frequently exceeded and the ventilation rates were low in most of the homes, even those with a ventilation system. Both ERVs and HRVs were equally effective at increasing air exchange rates above 0.30 ACH and at preventing formaldehyde concentrations from exceeding the 50 µg/m3 guideline during the fall and winter seasons. Furthermore, the ERVs were effective at preventing excessively low relative humidities in the homes. Based on observed difference of risk, intervention to increase ventilation in five sample homes and children would prevent 1 home to exceed the indoor air long-term formaldehyde guideline and prevent 1 asthmatic child experiencing at least one episode of wheezing over a year.

Changes in the length and three-dimensional orientation of muscle fascicles and aponeuroses with passive length changes in human gastrocnemius muscles.

The mechanisms by which skeletal muscles lengthen and shorten are potentially complex. When the relaxed human gastrocnemius muscle is at its shortest in vivo lengths it falls slack (i.e. it does not exert any passive tension). It has been hypothesised that when the muscle is passively lengthened, slack is progressively taken up, first in some muscle fascicles then in others. Two-dimensional imaging methods suggest that, once the slack is taken up, changes in muscle length are mediated primarily by changes in the lengths of the tendinous components of the muscle. The aims of this study were to test the hypothesis that there is progressive engagement of relaxed muscle fascicles, and to quantify changes in the length and three-dimensional orientation of muscle fascicles and tendinous structures during passive changes in muscle length. Ultrasound imaging was used to determine the location, in an ultrasound image plane, of the proximal and distal ends of muscle fascicles at 14 sites in the human gastrocnemius muscle as the ankle was rotated passively through its full range. A three-dimensional motion analysis system recorded the location and orientation of the ultrasound image plane and the leg. These data were used to generate dynamic three-dimensional reconstructions of the architecture of the muscle fascicles and aponeuroses. There was considerable variability in the measured muscle lengths at which the slack was taken up in individual muscle fascicles. However, that variability was not much greater than the error associated with the measurement procedure. An analysis of these data which took into account the possible correlations between errors showed that, contrary to our earlier hypothesis, muscle fascicles are not progressively engaged during passive lengthening of the human gastrocnemius. Instead, the slack is taken up nearly simultaneously in all muscle fascicles. Once the muscle is lengthened sufficiently to take up the slack, about half of the subsequent increase in muscle length is due to elongation of the tendinous structures and half is due to elongation of muscle fascicles, at least over the range of muscle-tendon lengths that was investigated (up to ∼60 or 70% of the range of in vivo lengths). Changes in the alignment of muscle fascicles and flattening of aponeuroses contribute little to the total change in muscle length.

Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method.

UNLABELLED: Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER(1z)). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER(2z)). In total, 287 daily pairs of AER(2z) and AER(1z) estimates were made from 35 homes across three cities. In 87% of the cases, AER(2z) was higher than AER(1z). Overall, the AER(1z) estimates underestimated AER(2z) by approximately 16% (IQR: 5-32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. PRACTICAL IMPLICATIONS: The results of this study suggest that the long-standing assumption that a home represents a single well-mixed air zone may result in a substantial negative bias in air exchange estimates. Indoor air quality professionals should take this finding into consideration when developing study designs or making decisions related to the recommendation and installation of residential ventilation systems.

[The value of housing conditions and urban environment for the health].

Housing and urban environments represent the physical context for everyday life and have a significant impact on population health and well-being. Depending on the quality of housing and urban conditions, they can support or restrict the health of their residents through a variety of aspects such as air pollution, noise, thermal conditions, safety aspects and environmental contamination. Therefore, housing and urban conditions are important dimensions for environmental health and knowledge on the main risk factors and their associated health effects is needed to identify adequate interventions and measures in the home and urban environment. This paper summarizes the results of WHO work on the health relevance of housing and urban environments and describes the health impact of the major risks observed in human settlements.

Quantifying the contribution of ambient and indoor-generated fine particles to indoor air in residential environments.

UNLABELLED: Indoor fine particles (FPs) are a combination of ambient particles that have infiltrated indoors, and particles that have been generated indoors from activities such as cooking. The objective of this paper was to estimate the infiltration factor (Finf ) and the ambient/non-ambient components of indoor FPs. To do this, continuous measurements were collected indoors and outdoors for seven consecutive days in 50 non-smoking homes in Halifax, Nova Scotia in both summer and winter using DustTrak (TSI Inc) photometers. Additionally, indoor and outdoor gravimetric measurements were made for each 24-h period in each home, using Harvard impactors (HI). A computerized algorithm was developed to remove (censor) peaks due to indoor sources. The censored indoor/outdoor ratio was then used to estimate daily Finfs and to determine the ambient and non-ambient components of total indoor concentrations. Finf estimates in Halifax (daily summer median = 0.80; daily winter median = 0.55) were higher than have been reported in other parts of Canada. In both winter and summer, the majority of FP was of ambient origin (daily winter median = 59%; daily summer median = 84%). Predictors of the non-ambient component included various cooking variables, combustion sources, relative humidity, and factors influencing ventilation. This work highlights the fact that regional factors can influence the contribution of ambient particles to indoor residential concentrations. PRACTICAL IMPLICATIONS: Ambient and non-ambient particles have different risk management approaches, composition, and likely toxicity. Therefore, a better understanding of their contribution to the indoor environment is important to manage the health risks associated with fine particles (FPs) effectively. As well, a better understanding of the factors Finf can help improve exposure assessment and contribute to reduced exposure misclassification in epidemiologic studies.

[Summary of ongoing activities on environmental noise and health at the WHO regional office for Europe].

The environmental noise is an important public health issue, according to recent assessment of the burden of diseases among environmental health risk factors in order of importance the environmental noise occupies the second place after air pollution. The World Health Organization (WHO) for the first time published its public health recommendations for the environmental noise in 1999 in the "WHO Guidelines for Community Noise (1999)". These recommendations found their development in WHO Night Noise Guidelines for Europe" (2009). From then onward there have been published new important data on the impact of the environmental noise on the health, that stipulated the revision of existing guidelines. Furthermore, both in the European Union (EU) Directive 2002/49/ EC and the Parma Declaration from 2010 there was pointed out the importance of renewal environmental noise recommendations. Responding to appearing interrogation, WHO Regional Office for Europe has recently initiated the process of the elaboration of new guiding principles known as "WHO Environmental Noise Guidelines for the European Region". The Guidelines will include a systematic review of most critical or important health consequences and also concentrate on health benefits of measures for the reducing noise levels. The Guidelines will consider noise coming from various noise sources such as aircraft, railroad, personal electronic devices and wind turbines. The Guidelines will also consider the particularity of such accommodations as residences, hospitals, and educational facilities. The work in the mentioned spheres is ongoing and the revised Guidelines are expected to be published in mid-2015. The Guidelines will provide up-to-date information on the health risks related to the environmental noise and evidence-based recommendations in order to support for WHO Member States in their efforts to prevent of the excessive noise and the struggle with their negative impact.

[The potential of the member states of the European Region of WHO in the field of prevention of adverse effects of chemicals on human health and measures for its strengthening].

The issue of providing chemical safety for the population, and especially for the most vulnerable groups remains to be actual in relation to the significant contribution of the impact of hazardous chemicals in the forming of morbidity rate, industrial growth and return of chemical products, rapid development and introduction of new technologies. The international community has adopted a series of mandatory and voluntary initiatives in the field of chemical safety. Strategic document for the WHO European Region, determining priorities in this area, is the Parma Declaration. Implementation of a wide range of arrangements set out in the Declaration requires sufficient capacity of the health sector and other concerned parties, the scope of which is addressed to aspects of healthcare from exposure to hazardous chemicals. Performed by the WHO European Centre for Environment and Health (ECEH) the assessment of existing in this area capacity based on the survey permitted to identify significant gaps in the legislative regulation, policies and planning, human and technical resources, the collection and exchange of information, education and training. With the participation of national experts ECEH developed a set of recommended measures aimed to the creation and strengthening the potential. Development and implementation of effective national strategies/plans/actions with regard to regional priorities and recommended actions will allow to increase the level of chemical safety for the population of the region as a whole.

Mortality associated with exposure to carbon monoxide in WHO European Member States.

In closed environments, the concentration of carbon monoxide (CO) can easily rise to health-threatening levels. CO-related incidents are often caused by poor condition or inappropriate use of indoor combustion devices as well as structure fires but are also due to suicides. To evaluate the incidence of CO poisoning in Europe, national data on CO-related mortality and morbidity were compiled from Member States of the WHO European Region using a standardized data collection form. National data on CO poisoning were provided by 28 Member States. Within the maximum reporting period (1980-2008), a total of 140 490 CO-related deaths were reported (annual death rate of 2.2/100 000). The number of hospital admissions available from six countries was 31 473. Unintentional CO deaths accounted for 54.7% of the CO-related deaths (35.9%: unintentional inhalation; 18.8%: related to structure fires). The intentional deaths related to CO exposure account for 38.6% of all CO-related deaths (38.1%: suicides; 0.5%: homicides). CO exposure is preventable but causes a substantial amount of deaths in many European countries. More efficient measures and policies to prevent CO poisoning and better reporting of CO mortality are necessary.

[The main conclusions about the medical aspects of air pollution: the projects REVIHAAP and HRAPIE WHO/EC].

For the time present the World Health Organization (WHO) is coordinating two major international projects aimed to provide the European Union (EU) with science-based information on health aspects of air pollution for a comprehensive analysis of EU policy in the field of air quality, scheduled for 2013. The information provided is structured in the form of answers to 26 policy-forming key questions, defined by the European Commission (EC). The questions cover the both general aspects that are important for air quality management, and also specific topics related to the health effects of certain air pollutants. Texts of the answers to the questions were provided on requests of large group of invited experts from leading specialized institutions around the world. First stages of the overview of existing data have shown that in recent years there has been published a significant amount of information proving adverse health effects of suspended particulate matter (PM), ozone (O3) and nitrogen dioxide (NO2) in an amount, which typically occurs in the air in Europe. These new data confirm the findings reported in renewed in 2005 WHO Guidelines for Air Quality (GAQ), and show that the negative health effects in some cases may take place at concentrations of aeropollutants in the air below mentioned in the GAQ in 2005. In the review there are presented the scientific arguments in favor of adoption of strong measures to improvement air quality and reduction of the burden of diseases associated with air pollution in Europe. The conclusions formulated within a framework of these projects, are equally referred to all Member States and can become a basis for the development and implementation of effective strategies to reduce air pollution and reduction of its negative impact on the health of the population.

The effect of inertial loading on wrist kinetic tremor and rhythmic muscle activity in individuals with essential tremor.

OBJECTIVES: Determine the effect of concentric and eccentric movement and contraction intensity on the strength of rhythmic muscle activity in individuals with essential tremor (ET). METHODS: 21 ET subjects and 22 healthy controls produced wrist flexion-extension movements while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Kinetic tremor and wrist extensor neuromuscular activity were recorded using an angular displacement sensor and electromyography (EMG). RESULTS: Rhythmic muscle activity was twice as big during movement compared to previous results involving postural or isometric tasks. ET subjects with greater rhythmic muscle activity had (1) larger overall kinetic tremor amplitude, (2) greater tremor spectral power during eccentric compared to concentric movement and (3) a reduction in overall kinetic tremor amplitude and the percentage of EMG spectral power accounted for by the tremor spectral peak in the presence of inertial loading. CONCLUSIONS: Greater than normal kinetic tremor amplitude appears to be limited to ET subjects with higher levels of rhythmic muscle activity. Furthermore, rhythmic muscle activity is much greater during movement compared to during postural or closed-kinetic tasks. SIGNIFICANCE: The strength of rhythmic muscle activity in ET is influenced by the type of contraction (i.e., static vs. dynamic) being performed. Clinicians and researchers should include measures of simple kinetic tremor as part of their assessments.

The effect of contraction intensity on force fluctuations and motor unit entrainment in individuals with essential tremor.

OBJECTIVES: Quantify the effect of increasing contraction intensity on the amplitude of force fluctuations and neuromuscular and force tremor spectral power. METHODS: Twenty-one subjects with essential tremor (ET) and 22 healthy controls applied isometric wrist extension contractions. Various sub-maximal contraction intensities were evaluated (5%-, 10%-, 20%- and 30%-MVC). Force fluctuations and wrist extensor neuromuscular activity were recorded using a load cell and electromyography (EMG). RESULTS: Higher contraction intensities were associated with larger amplitude force fluctuations and greater neuromuscular activation. However, spectral power associated with tremor peaks remained relatively constant (EMG) or decreased (force) with increasing contraction intensity. CONCLUSIONS: Motor unit entrainment associated with centrally generated oscillatory inputs does not increase with greater levels of muscle activation. SIGNIFICANCE: Rather than influencing a constant proportion of active motor units, abnormal oscillatory drive influences a relative constant number of total motor units. When combined with the findings from our previous study on postural tremor, the present results provide preliminary evidence that abnormal stretch reflex activity may contribute to this motor unit entrainment.

The effect of inertial loading on wrist postural tremor in essential tremor.

OBJECTIVES: Determine the effect of inertial loading on the strength of motor unit entrainment and the synergistic/competitive interaction between central and mechanical reflex tremor components in subjects with essential tremor (ET). METHODS: Twenty-three subjects with ET and 22 controls held their hand in an outstretched position while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Hand postural tremor and wrist extensor neuromuscular activity were recorded. RESULTS: Inertial loading resulted in a reduction in postural tremor in all ET subjects. The largest reduction in tremor amplitude occurred between 5% and 15% loads, which was associated with spectral separation of the mechanical reflex and central tremor components in a large number of ET subjects. Despite an increase in overall neuromuscular activity with inertial loading, EMG tremor spectral power did not increase with loading. CONCLUSIONS: The effect of inertial loading on postural tremor amplitude appears to be mediated in large part by its effect on the interaction between mechanical reflex and central tremor components. Also, ET is associated with a constant absolute level of motor unit entrainment. SIGNIFICANCE: The amplitude of postural tremor is dependent on both central and peripheral factors, with proportionally greater motor unit entrainment occurring at low contraction intensities.