A study has been undertaken to determine the energy balance and thermal stress of skidoo drivers in Antarctica, and to compare them in those respects with dog sledgers. A background study of the variation over a year in various physiological parameters in some of the travellers studied was also carried out. 1. Resting metabolic rate. blood pressure, and pulse rate, body weight and skin fold thickness were measured monthly over a period of one year in six men living on a scientific base in Antarctica. Percentage body fat was determined from body weight and skin fold thickness. Skin fold thickness and percentage body fat were greater than that to be expected in the U.K.: other parameters did not differ significantly from accepted norms. Most of the parameters measured showed similar patterns cf variation: high values in spring or summer, falling in winter, with a small-peak after midwinter, rising again in autumn. There was a significant reduction in skin fold thickness and body fat over the year, but no significant change in other parameters. 2. Energy intake, expenditure and balance, weight loss and fat loss were determined in men travelling overland in Antarctica. Thirteen trips, seven by skidoo and six by dog sledge, each of approximately eleven days, were studied. Energy deficit was found on all trips. Energy intake, expenditure, and deficit were significantly greater on dog trips. Weight loss and fat loss were also greater, but the differences were not statistically significant. 3. Skin temperature was measured and thermal comfort, shivering, sweating, clothing and activity were recorded on ten day trips, six by dog sledge, and four by skidoo. Skin temperatures on dog runs were lower and more variable than on skidoo runs, and differences between central and peripheral temperatures greater. Thermal discomfort, shivering and sweating were more common on dog runs.

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Both theoretical and practical importance can be attached to attempts to model human threshold and supra-threshold visual performance under water. Previously, emphasis has been given to the integration of visual data from experiments conducted in air with data of the physical specification of the underwater light field. However, too few underwater studies have been undertaken for the validity of this approach to be assessed. The present research therefore was concerned with the acquisition of such data. Four experiments were carried out: (a) to compare the predicted and obtained detection thresholds of achromatic targets, (b) to measure the relative recognition thresholds of coloured targets, (c) to compare the predicted and obtained supra-threshold appearance of coloured targets at various viewing distances and under different experimental instructions, (d) to compare the predicted and obtained detection thresholds for achromatic targets under realistic search conditions. Within each experiment, observers were tested on visual tasks in the field and in laboratory simulations. Physical specifications of targets and backgrounds were determined by photometry and spectroradiometry. The data confirmed that: (a) erroneous predictions of the detection threshold could occur when the contributions of absorption and scattering to the attenuation of light were not differentiated, (b) the successful replication of previous findings for the relative recognition thresholds of colours depended on the brightness of the targets, (c) the perceived change in target colour with increasing viewing distance was less than that measured physically, implying the presence of a colour constancy mechanism other than chromatic adaptation and simultaneous colour contrast; the degree of colour constancy also varied with the type of target and experimental instructions, (d) the successful prediction of the effects of target-observer motion and target location uncertainty required more than simple numerical corrections to the basic detection threshold model. It was concluded that further progress in underwater visibility modelling is possible provided that the tendency to oversimplify human visual performance is suppressed.

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The purpose of the study was to examine the proposition that adaptations of skeletal muscle are more important determinants of the ability to sustain submaximum exercise than maximum oxygen uptake (V0₂ max). The metabolic response to exercise was compared in 2 groups of runners with differing V0₂ max values. Trained female runners, despite their lower V0₂ max values, showed lower respiratory exchange ratio values (R) and higher post-exercise concentrations of plasma fat metabolites than active male subjects. This was so when subjects ran at a common absolute speed and when each individual ran at a speed equivalent to 60% V0₂ max. Six weeks of training on the cycle ergometer resulted in a 16% increase in V0₂ max but a 250% increase in endurance performance, i.e. time to exhaustion at 80% V0₂ max. During standard, submaximum exercise oxygen uptake, ventilation, heart rate, R values and blood lactate concentration were lower post-training than pre-training. The concentrations of plasma fat metabolites during and after exercises were not influenced by training. Training one leg and not the other resulted in 20% and 10% increase in V0₂ max but 340% and 150% increases in endurance for the trained leg (TL) and the untrained leg (UTL) respectively. The increases in both variables were significantly greater for the TL than for the UTL. Changes in submaximum V0₂, ventilation, R values and blood lactate concentration were mainly restricted to exercise with the TL but the reduction in heart rate was similar for each leg. Plasma FFA, glycerol and citrate concentrations during exercise were unchanged for either leg. The role of citrate in the training-induced interaction of fat and carbohydrate metabolism was investigated. Artificial elevation of plasma citrate concentrations by ingestion of citrate did not decrease blood lactate concentrations during exercise. After short-term fasting citrate accumulated in the myocardium but not in skeletal muscles in the rat. Plasma citrate concentration was a poor predictor of muscle citrate concentration in these circumstances. When subjects were exhausted after single-leg exercise at 80% V0₂ max muscle glycogen concentration decreased by 70% and muscle lactate concentration was increased 10-fold. Training halved the rate of glycogen depletion, decreased muscle lactate concentration and resulted in a decrease in R values only during exercise with the TL. The trend towards an increase in muscle citrate concentration was restricted to trained muscle. The experiments showed that absolute values of V0₂ max could be dissociated from the metabolic characteristics of endurance training and that V0₂ max is an insensitive indicator of training improvements in submaximum endurance. Peripheral adaptations are the dominant influence on the ability to sustain submaximum exercise but training only one leg can cause some systemic change which influences both V0₂ max and endurance for the UTL. The mechanism of the training-induced interaction of fat and carbohydrate metabolism remains unclear.

Twisting movements are categorised into three mechanical types, named as DIRECT, COUNTER-ROTATION and TILT TWIST. Twisting techniques are studied using mathematical models. A mathematical inertia model is constructed to enable the determination of segmental inertia parameters from anthropometric measurements. A film analysis program is developed so that the angles, which specify the orientation and configuration of the body, may be derived from digitised film data. A computer simulation model, comprising 11 segments and 17 degrees of freedom, is constructed to represent the human body in free fall. The combined use of the three computer programs results in maximum errors of 3% for somersault and 9% for twist in ten filmed movements. The mechanics of twisting techniques are explained using simple mathematical models. An analysis of rigid body motions shows that there are two distinct modes of motion, named as the ROD MODE and the DISC MODE. It is shown that it is possible to change from one mode to the other by varying the angle of pike and this permits the twist to be increased or stopped or even reversed. The capacities of twisting techniques are determined using simulations. For twists from a piked position, delaying the extension from the pike can increase the twist rate although this does depend upon the particular technique used and the initial direction of somersault. The contributions of twisting techniques used in the filmed movements are determined using simulations based upon modifications of the film data. It is found that counter-rotation techniques made small contributions and that aerial techniques, which increased the angle of tilt, were the major contributors, even in movements where the twist was apparent at take off. Using the simulation model it is shown that the build up of twist in the unstable double layout somersault may be controlled by means of small asymmetrical arm movements during flight.

Influential models, capable of predicting human responses to hot and cold environments and potentially suitable for use in practical applications, have been identified and implemented in usable forms onto computers. Six models have been evaluated: the Gagge and Nishi 2-node model of human thermoregulation, the Stolwijk and Hardy 25-node model of human thermoregulation, the Givoni and Goldman model of rectal temperature response, the ISO/DIS 7933 analytical determination and interpretation of thermal stress using calculation of required sweat rate model, the Ringuest 25-node model of human thermoregulation, and the Wissler 225-node model of human thermoregulation. A preliminary evaluation enabled the Ringuest and Wissler models to be eliminated from further investigation. In the case of the Ringuest model this was because of its poor predictions, and for the Wissler model because of practical difficulties with its implementation and use. The remaining models were modified to quantify the insulative effects of clothing by the method considered to be most appropriate, given the current state of knowledge. The modified versions of the models were evaluated by comparing their predictions with human data published previously in the literature. Experimental data were available for a wide range of environmental conditions, with air temperatures ranging from -10 to 50 °C, and with different levels of air movement, humidity, work and clothing. Data for a total of 590 subject exposures were used. The experimental data were grouped into environment categories to enable effects such as the influence of wind or clothing, on the accuracy of the models' predictions to be examined. This categorization also enables advice to be given as to which model is likely to provide the most accurate predictions for a particular combination of environmental conditions. For the majority of environment categories, for which evaluation data were available, at least one of the models was able to predict to an accuracy comparable with the degree of variation that occurred within the data from the human subjects. It may be concluded from the evaluation that it is possible to accurately predict deep body and mean skin temperature responses to cool, neutral, warm and hot environmental conditions. The models' predictions of deep body temperature in the cold are poor. Overall, the 25-node model probably provided the most accurate predictions. The 2-node model was often accurate, but could be poor for exercise conditions. The rectal temperature model usually overestimated deep body temperature, except for very hot or heavy exercise conditions, where its predictions were reasonable. The ISO model's allowable exposure times were often acceptable, but would not have protected subjects for some exercise conditions.

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