ISSN:0112-1642    

DOI:10.2165/00007256-198704060-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummanryOzone is a principal component of photochemical air pollution endogenous to numerous metropolitan areas, which may induce irritant effects on the respiratory tract which impair pulmonary function, result in subjective symptoms of respiratory discomfort, including cough and shortness of breath, and can limit exercise performance. The effects of moderate ambient photochemical air pollution observed in a mobile laboratory have also been shown to be similar to those induced in laboratory chamber exposures to the same level of ozone alone.The metabolic demand of exercise increases minute ventilation V̇Eand thus, the rate of ozone inhalation over that at rest. Potentially, exercise can also enhance the effects of ozone by: (a) reducing nasal passage absorption; (b) increasing the uniformity of ventilation throughout the lungs; and (c) replacing reacted ozone at a faster rate. However, results from 2-hour intermittent exercise and 1-hour continuous exercise exposures at the same total ventilation and ozone concentration have been shown to yield similar pulmonary function effects.It has been shown via significant variation in exercise intensity, and thus V̇E, that the simple product of ozone concentration, V̇Eand exposure time (termed the ozone effective dose) predicts pulmonary function and exercise ventilatory pattern (induced rapid, shallow breathing) effects more precisely than ozone concentration alone. Better prediction of pulmonary function effects has been achieved via multiple regression analysis in which ozone concentration is given a greater weighting than V̇Eand exposure time.Light intermittent exercise was first studied in 2-hour laboratory exposures to ozone at concentrations rarely seen in the ambient environment. In recent studies, heavy continuous exercise has been used in 1-hour exposures to ozone at levels routinely observed in photochemical episodes (≤ 0.35 ppm). Statistically significant impairment of exercise performance has been observed at 0.18 ppm, a level reached for 1 hour, or more, on about 180 days per year in the Los Angeles basin.Responses of subpopulation groups, such as children, young adult females, older adults, and those with pre-existing pulmonary disease are not notably different from those of young adult males provided that the ozone effective dose is proportional to body size. Conversely, highly trained endurance athletes demonstrate significant responses at rather low ozone concentrations due to their ability to sustain very high V̇Eover prolonged periods.Numerous investigators have observed a wide range of individual subject’s pulmonary function responses to a given ozone exposure, although mechanisms accounting for this disparate individual responsiveness have not been identified. In recent studies, decreases in exercise performance and greater respiratory subjective symptom severity have been observed in those with greater pulmonary function impairment.Repeated exposure to high ambient levels of ozone within 24 hours results in greater response than upon initial exposure, if 72 hours or longer intervenes before re-exposure. However, with several consecutive daily exposures, pulmonary function and subjective symptom responses are greatly reduced. Exercise performance is also much less affected than that incurred upon initial exposure.Photochemical smog episodes also include air pollutants other than ozone and usually coincide with high ambient temperatures, which can significantly reduce endurance exercise performance. There is no appreciable additive impact with carbon monoxide, nitrogen dioxide or sulphur dioxide, but peroxyacetyl nitrate appears to induce an additive effect with ozone. The combination of heat and ozone exposure has been shown to accentuate ozone-induced effects although the mechanism remains unclear.Only a few studies have been designed to investigate maximum exercise performance and V̇Emax impairment following ozone exposure sufficient to induce significant pulmonary function and respiratory discomfort response. With the increasing use of high intensity (≥ 65% of V̇2max) 1-hour continuous exercise protocols, especially in the presence of ambient heat (Tdb> 31°C), numerous instances of subjects unable to complete the full hour at the workload prescribed, or only upon reducing the workload, have been reported.Mechanisms accounting for reduced maximum exercise performance upon significant ozone exposure have not been well elucidated. Although significant pulmonary function impairment has been routinely observed, as well as enhanced subjective symptoms of res-piratory discomfort, no consistent objective evidence of effect on oxygen diffusion, transport and delivery has been observed. Hence, it appears that factors associated with ventilatory limitation impair both V̇O2maxand prolonged heavy exercise (> 65% V̇O2max) performance. The observation that ozone exposure, which induces significant pulmonary function impairment, also incurs an increased perceived exertion during submaximal exercise strongly supports this contention. The hypothesis of subjective respiratory discomfort as the principal factor accounting for reduced exercise performance is further substantiated by several notable occurrences of discordance with pulmonary function impairment.

ISSN:0112-1642    

DOI:10.2165/00007256-198704060-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryResearchers of the future will depend upon computer technology to address questions that previously could not be answered using traditional methods of data acquisition. Re-cent advances in computer design and software availability have eliminated many of the limitations previously associated with computer use in the laboratory setting. Although computerisation facilitates the acquisition of laboratory data, identification of errors in-troduced into the measurement is often more difficult.The laboratory computer is only one component of an automated data acquisition system. A system designed to collect physiological data comprises several primary com-ponents, including: (a) sensing element; (b) signal amplification/conditioning circuits; (c) analogue display; (d) computer interface; (e) laboratory computer; and (f) acquisition soft-ware. The acquisition and conditioning of analogue signals is accomplished using tradi-tional laboratory procedures familiar to the researcher. Converting this analogue signal into a digital format used by the computer, however, represents new techniques.Fundamentals of computerised data acquisition are discussed. An understanding of how an automated data acquisition system is configured and the techniques used to transform the values will assist the user in identifying sources of error introduced into the measurement. Additionally, familiarisation with the methods of computerisation will provide insight into future applications of computer technology in the human performance laboratory.

ISSN:0112-1642    

DOI:10.2165/00007256-198704060-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryOlder individuals, regardless of how one classifies ‘old’, are the most rapidly growing portion of the population. Statistics from heat waves and other morbidity-mortality data strongly suggest that older persons are at greater risk of developing life-threatening manifestations of heat stress such as heat stroke. Most laboratory studies have found that ageing is associated with decreased heat tolerance and alterations in thermoregulatory effector responses. What is not so clear is the role of ageingper sein this decreased heat tolerance (as opposed to some concomitant functional decline, e.g. decreasing V̇O2max, which accompanies ageing across a population). Studies have shown decrements in resting heat tolerance and responses to thermal transients in older adults. With exercise in warm environments, most research has focused on the sweating response and it appears that whether or not sweating rate declines in the elderly is dependent upon the environment studied. In hot dry environments, older persons (of both sexes) consistently secrete sweat at a lower rate than their younger counterparts. However, as humidity of the environment increases, this difference tends to disappear. A key issue which deserves further attention is that of hydration in the elderly, both in terms of body water content and compartmentalisation, and of skin water content. Finally, ageing is often accompanied by other conditions (e.g. hypertension, diabetes, cardiovascular insufficiencies, long term therapeutic drug modalities) which further affect heat tolerance and thermoregulation.

ISSN:0112-1642    

DOI:10.2165/00007256-198704060-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS