The effects of resistance training on aerobic and anaerobic power of young boys.

A 4-wk interval-type training program incorporating omni-kinetic equipment and stationary cycling elicited an increase in the absolute and relative VO2max of an active group of young boys. The improvement in aerobic function was independent of the training protocols of high velocity-low resistance and low velocity-high resistance. However, the training programs failed to increase anaerobic function as measured by an "all-out" cycle test in which power output was calculated in watts and watts per kilogram for 0- to 15-s and 15- to 30-s work periods. Changes in aerobic and anaerobic functions were independent of physiological maturity as determined by serum testosterone level (ng X dl-1).

Psychologic effects of cardiovascular conditioning: a controlled experiment.

Although there have been numerous studies documenting a relationship between physical fitness and psychologic functioning, few have employed the type of experimental design that would allow conclusions to be drawn regarding cause and effect. In the present study, college students were randomly assigned to a cardiovascular conditioning program or to a control program designed to give the appearance of physical training while minimizing cardiovascular benefits. Both groups were tested for cardiovascular fitness as well as on a number of self-rating scales before and after the 6-week program. The cardiovascular group demonstrated a significantly greater improvement in cardiovascular fitness than the control group and also tended to show a greater reduction in anxiety and greater increase in measures of general psychologic well-being.

Plasma norepinephrine responses of man in cold water.

The hypothermic stress of immersion in cold water stimulates release of norepinephrine from the sympathetic nervous system. The speed and pattern of this response was studied in six healthy men by serial measurements of plasma norepinephrine concentrations before, during, and after 60 min of immersion in 10 degrees C water. After immersion for 2 min, the mean norepinephrine concentration was increased from 359+/-32 (basal) to 642+/-138 pg/ml and rose gradually to a maximum of 1.171+/-226 pg/ml after 45 min of immersion. Metabolic rate increased approximately threefold during the immersion period. After rewarming in warm water (40 degrees C), the subjects showed a transient peak in plasma norepinephrine followed by a rapid decrease to basal levels after 30 min. The fall in plasma norepinephrine after approximately 8 min of rewarming occurred despite persistent depression of the core temperature and coincided with a sudden decrease in metabolic rate and cessation of body shivering. These results suggest that the sympathetic nervous response to cold can be activated or suppressed very quickly and is dependent on the skin temperature.

Accidental hypothermia: an experimental study of practical rewarming methods.

Five rewarming techniques, appropriate for first-aid use in the nonhospital setting, were applied to each of nine subjects whose body temperatures had been lowered to 35 degrees C in a stirred tank of 7.5 degrees C water. The rewarming techniques were: a) inhalation of heated, water-saturated oxygen; b) placement of heating pads over areas of high heat transfer; c) combination of methods a) and b); d) hot whirlpool bath; and e) shivering. Inhalation of heated, water-saturated oxygen was significantly better than the shivering control in minimizing temperature "afterdrop" and is, therefore, preferred over the other techniques as it avoids the physiological hazards of the peripheral vasodilation from external rewarming.

The effects of alcohol upon cooling rates of humans immersed in 7.5 degrees C water.

The effects of the ingestion of a moderate dose of alcohol, a known vasodilator, upon the cooling rate of four human subjects immersed in 7.5 degrees C water for periods of time ranging from 38 to 75 min is reported. In three of the cases the cooling rate was retarded, in no case was it accelerated. This result, while lacking statistical significance, has not previously been reported. The difficulties attendant upon such research are noted.

Thermoregulatory heat production in man: prediction equation based on skin and core temperatures.

The relationship of metabolic rate to skin and core temperatures was measured in eight subjects cooled in 10 degrees C water. Reference core temperatures, based on the tympanic and rectal sites, were 41.0 and 41.4 degrees C, respectively. Reference mean skin temperatures were 41.8 and 42.2 degrees C when determined in relation to tympanic and rectal temperatures, respectively. These results enabled construction of equations for predicting the steady-state metabolic rate (MR, W-kg-1) of nonexercising man according to thermal inputs from the skin (Tsk) and core (Tty or Tre) MR = 0.0356(Tsk - 41.8)(Tty - 41.0) or, MR = 0.0314(Tsk - 42.2)(Tre - 41.4). Each equation was limited by the low level of basal metabolic rate (1.1 W-kg-1) and by the high level of peak metabolic rate (6.4 W-kg-1). Evaluation of these equations showed satisfactory agreement with previous observations and concepts on the regulation of heat production in man.

Behaviour modification techniques: their use in individual and community programmes.

New Perspectives on the Health of Canadians described the self-inflicted nature of many of the major medical problems facing Canada. Given this understanding it might have been anticipated that a carefully mounted large scale health education programme would lead to a reversal of behaviour-related complaints. However, such programmes have not had a strong record of success, with the possible exception of the recently reported Stanford Three Communities study, which is concerned with decreasing cardiac risk factors by a process of mass persuasion, aimed at teaching specific behavioural skills. In the past, living conditions have changed slowly and appropriate lifestyles have evolved along with changing conditions. Only recently has environmental change occurred so dramatically that liviing patterns could no longer mutate and develop gradually to keep pace. Hence the demand for behavioural science to assist people to develop new lifestyles which are in synchrony with a rapidly changing world. Examination of the literature concerning the application of behaviour modification techniques to specific problems clearly demonstrates the difficulties involved in changing behaviours such as smoking and overeating. Behaviour change related to increasing physical activity shows more promise in that it can be presented positively as a pleasant addition to people's lives. If lifestyle modification and environmental control are going to assume a larger part of the health care system, methods have to be devised to translate the experimental successes with relatively small numbers into powerful programmes for press action.

Effect of behavioral variables on cooling rate of man in cold water.

Five different behaviors of man while in cold ocean water (9-10 degrees C) were assessed for their effect on rate of progress into hypothermia. With subjects wearing lifejackets, two thermally protective behaviors were studied which reduce exposure to the water of areas of body surface with high relative heat loss potential. One was huddling of three persons and the other a self-huddle behavior (HELP or Heat Escape Lessening Posture). These two behaviors resulted in significant reductions of rectal temperature cooling rate of 66 per cent and 69 per cent, respectively, of that of a control behavior. With no flotation available, two survival swimming behaviors (treading water and drownproofing) were shown to result in significant increases in cooling rate to 134 per cent and 182 per cent, respectively, of the control behavior. Potential swimming distance of subjects wearing a life-jacket was 0.85 miles in water near 12 degrees C before predicted incapacitation by hypothermia. It was concluded that behavioral variables can be of major importance in determining survival time in cold water through modulation of cooling rate associated with other variables such as fatness, body size, and clothing.

Thermal balance and survival time prediction of man in cold water.

Metabolic rates and rectal temperatures were continuously monitored for humans immersed in cold ocean water (4.6--18.2 degrees C) under stimulated accident conditions. The subjects wore only light clothing and a kapok lifejacket while either holding-still or swimming. While holding-still, metabolic heat production (Hm,kcal-min--1) was inversely related to water temperature (Tw, degrees C) according to the equation Hm equals 4.19 minus-0.117 Tw. This temperature response pattern is shown to be similar to that for exposure to air of the same temperature when air velocity is just over 5 m.p.h. (2.24 m/s). The thermogenic response was one-third efficient in balancing the calculated heat loss in cold water, resulting in hypothermia at a rectal temperature cooling rate (C, degrees C-min--1) dependent on water temperature (Tw, degrees C) according to the relation C equal 0.0785 - 0.0034Tw. Although swimming increased heat production to 2.5 times that of holding-still at 10.5 degrees C water temperature, cooling rate was 35% greater while swimming. A prediction equation for survival time (ts, min) of persons accidentally immersed in cold water (Tw, degrees C) has the form ts equal 15 + 7.2/(0.0785-0.0034Tw), based on the findings of this study, and it is compared to pre-existing models.