Excessive computer game playing among Norwegian adults: self-reported consequences of playing and association with mental health problems.

Computer games are the most advanced form of gaming. For most people, the playing is an uncomplicated leisure activity; however, for a minority the gaming becomes excessive and is associated with negative consequences. The aim of the present study was to investigate computer game-playing behaviour in the general adult Norwegian population, and to explore mental health problems and self-reported consequences of playing. The survey includes 3,405 adults 16 to 74 years old (Norway 2007, response rate 35.3%). Overall, 65.5% of the respondents reported having ever played computer games (16-29 years, 93.9%; 30-39 years, 85.0%; 40-59 years, 56.2%; 60-74 years, 25.7%). Among 2,170 players, 89.8% reported playing less than 1 hr. as a daily average over the last month, 5.0% played 1-2 hr. daily, 3.1% played 2-4 hr. daily, and 2.2% reported playing > 4 hr. daily. The strongest risk factor for playing > 4 hr. daily was being an online player, followed by male gender, and single marital status. Reported negative consequences of computer game playing increased strongly with average daily playing time. Furthermore, prevalence of self-reported sleeping problems, depression, suicide ideations, anxiety, obsessions/ compulsions, and alcohol/substance abuse increased with increasing playing time. This study showed that adult populations should also be included in research on computer game-playing behaviour and its consequences.

[Work in very hot, dry climates: evaluation of stress and procedures for reducing strain on the human body]. / Arbeit in sehr heissen, trockenen Klimaten: Bewertung der Belastung und Verfahren zur Reduktion der Beanspruchung des menschlichen Körpers.

Even in temperate zones of the earth such as Middle Europe quite a number of men have to work in very hot dry climates, particularly in salt mines. Problems of evaluation stress under these condition are discussed. Climatic chamber experiments at ambient temperatures mainly between 45 and 65 degrees C were performed in order to find out various possibilities to reduce heat strain. New methods are discussed for reducing extremely elevated body core temperatures.

Volume calibration of various gasmeters using a modified Tissot spirometer.

Various methods for determinating energy expenditure by indirect calorimetry are used in laboratory and field studies such as the Douglas bag method, often used in combination with a wet gasmeter, the respirometer of Kofranyi and Michaelis (KM) and the Oxylog (OX). To calibrate the volume measurements of these pieces of apparatus a modified Tissot spirometer was built, consisting of an outer casing filled with water, a core and a bell. It was equipped with a solid counterbalance and with an additional roller chain, partly freely suspended on the side of the counterbalance. This construction allowed compensation for the varying buoyancies of the bell. The lift of the bell was measured by means of a vernier scale. From calculations of the geometric volume a revolution counter was adapted to record the moved volume in litres. By means of this spirometer volumes up to 200 l can be used for calibration at various physiological flow rates. Calibration procedures for KM, wet gasmeters and OX were developed. For OX a small inaccuracy up to 2.0% was observed within the flow range from 20 to 70 l.min-1. The inaccuracy increased at higher flow rates. Under defined calibration conditions the modified Tissot spirometer enabled repeated calibrations of different types of gasmeters.

A comparative study on different methods for the determination of energy expenditure.

In order to determine energy expenditure, the Douglas Bag technique (DB) and Kofranyi-Michaelis respirometers (KM) have been widely used under field conditions for several decades. Some years ago the Oxylog (OX) method was developed, measuring simultaneously the difference of partial oxygen pressure in inspired and expired air (PO2 diff.) by two polarographic oxygen sensors. In order to compare these three methods laboratory experiments (3 test subjects, 5 different bicycle ergometer work loads, 180 measurements per apparatus) were performed. Oxygen uptake (VO2) varied between about 0.9 to 3.0 l/min. The VO2 data obtained by the DB method, which were used as a reference, and those obtained by the KM method agreed fairly well. The recorded data of OX underestimated VO2 up to 21%, with the deviation increasing with work intensity. A sufficient accuracy of recorded VO2 was observed only up to moderate work intensity. OX data calculated from ventilation volume of inspired air per minute (VI) and PO2 diff., measured by OX, were always about 19% higher than those recorded by OX. This means that the calculated VO2 values of the OX corresponded fairly well with DB values at heavy work loads. The reason for the differences between recorded and calculated OX data is still unknown. Further research is urgently needed.

Modification of Vernon's globe thermometer and its calibration in terms of physiological strain.

Six men wearing shorts performed treadmill work in about 150 climatic chamber experiments at several temperatures of Vernon's globe thermometer (tg) from 25 to 50 degrees C. Each tg was produced partly by an equal air temperature (ta) and a mean radiant temperature (MRT), partly by a lowered ta (minimum 5 degrees C) and an MRT elevated up to about 80 degrees C above the ta. With an increasing MRT and lowered ta, respectively, body temperature, heart rates, and sweat losses decreased significantly. In another 55 experiments physiologically equivalent combinations of ta and MRT were derived. According to the results a modified globe thermometer was built. It reduced the errors of Vernon's instrument by about 75%. The remaining error of 25% was due to changes in air velocity between 0.5 and 2 m.s-1. The applicability of simple instruments like globe thermometers is obviously limited for the description of physiologically equivalent conditions of unequal ta and MRT at various air velocities.

Evaluation of tolerance limits for humans under heat stress and the problems involved.

Investigators are divided about the limits of tolerable ambient temperatures and air humidities, even under equal boundary conditions. In 266 climatic chamber experiments, mostly lasting 4 h, 13 young healthy men were exposed to combinations of ambient temperature (20 to 55 degrees C) and relative humidity (5 to 97%) at an air velocity of 0.3 m.s-1. They were lightly clad and performed equal treadmill work (metabolic rate about 850 kJ.h-1). Mean rectal isotherms and their standard deviations were calculated from the final rectal temperatures of the 13 men and plotted on a psychrometric chart. The slopes of the isotherms were compared with those of various "indices of heat stress." The probability of reaching the potentially critical rectal temperature of 39 degrees C was calculated according to data of Wyndham & Heyns. It increased from about 1:500,000 to 1:150 in climates corresponding to mean isotherms of 37.6 and 38.2 degrees C, respectively. Most of the limits thus far proposed are situated between these two isotherms, and they differ merely in regard to health risk. It is useless to discuss "correct" or "incorrect" limits until society has decided what risk is to be accepted. An upper tolerable limit per se does not and cannot exist. For several reasons the 37.6 degrees C isotherm might be taken into consideration as a limit.

Heat stress upon undressed man due to different combinations of elevated environmental temperature, air humidity, and metabolic heat production: a critical comparison of heat stress indices.

In several 100 climatic chamber experiments young healthy acclimatized men were exposed successively to combinations of ambient temperature and air humidity that were varied systematically from day to day within the range of 15 to 57 degrees C and 8 to 97% relative humidity, with air speed kept constant at 0.3 m/s. The subjects who were nearly nude were exposed at rest and at different treadmill work levels (metabolic rates up to about 1350 kJ/h). Each exposure lasted between two and six h. It was found that body temperatures and heart rate, but not loss of sweat, were suitable criteria for indicating equal stress conditions. Equations were derived describing those climatic combinations which were equivalent at the various activity levels of each subject. The slope of the respective equivalence curves plotted in psychrometric charts varied systematically with work level. The curves obtained for various subjects at any given activity level showed similarities, so that the calculation of an equivalence system common to all subjects seemed to be justified. A detailed comparison of these results with previous indices is presented. The combinations of ambient temperatures and humidities that were found to be equivalent under the given conditions of physical activity corresponded particularly well with the Index of Physiological Effect (ROBINSON et al.). There was also good agreement with the P4SR Index (MCARDLE et al.). The combinations corresponded with other indices (Heat Stress Index of BELDING and HATCH, Index of Thermal Stress of GIVONI) and with Basic Effective Temperature and Wet-bulb Globe Temperature only within limited ranges of climate depending upon work level. A procedure is presented which allows one to evaluate in terms of physiological responses how far various indices describe equivalent stress conditions correctly.

Effects of environmental heart on performance and some physiological responses of a man during a psychomotor task.

In climatic chamber experiments some physiological responses of a young healthy man were studied. He was able to perform a pursuitmeter task in a fairly wide range of warm climates without decrement of performance. The highly trained and heat-acclimatized subject was exposed nearly undressed to various ambient temperatures (28--55 degrees C) and air humidities (10--92%) which were combined in such a way that the conditions were tolerable up to 4 h. In 18 experiments the man was sitting quietly all the time, and in a parallel series of 19 experiments (up to 50 degrees C) he performed the pursuitmeter task during the last 2 hours of each exposure. Under equal climatic conditions work caused a slight increase in oxygen uptake corresponding to an increase in metabolic heat generation by about 70 kj/h (17kcal/h) on the average. Rectal temperature and temperature next to the eardrum were 0.1--0.2 degrees C higher at work as compared with rest. Weight loss at work exceeded weight loss at rest, the difference ocrresponding to an increase in evaporative heat loss by about 110 kj/h (26 kcal/h) which resulted in a decrease of mean skin temperature of 0.5 to 0.9 degrees C. Superelevation of heart rate due to work reached about 10 beats/min in a thermally neutral environment, but up to 30 beats/min in hot dry and warm humid surrounding, reflecting the additional effort for maintaining performance under conditions of increasing heat stress.