Cortical control of sinus arrhythmia in man studied by spectral analysis.

Eighteen healthy male volunteers, 21-26 years old, participated in a study intended to detect cortical control of beat-to-beat heart rate variability independent of the effects on breathing and mean heart rate. They were tested while seated and standing relaxed (baseline), and while performing tasks requiring concentrated attention while sitting. The mental concentration elicited a typical cardiorespiratory response manifested by moderate acceleration and shallowing of respiration with a small increase of mean heart rate (HR), a pattern already widely acknowledged as typically associated with concentration.

Physical work load in modern mining.

Following our Institute's involvement in the physiology of mining work (since 1953), this paper deals with underground work load investigated in terms of time, energy expenditure and heart rate in coal miners working with various types and degrees of mechanization. Results showed that a chamber coal face and at heading (coal or sterile rock) mechanization of haulage and loading (conveyor belt and loading machine) led to 50 -- 100 kcal reduction of energy expenditure/hour. At longwall faces, mechanization of haulage (by conveyor) or hewing and loading (with drum-combine) shortened shoveling time, while there was an increase of manual work in the tasks of supporting which was conducive to metabolic rates of 300 kcal/hour.

Physical fitness in different groups of industrial workers.

Maximum oxygen consumption was determined by the indirect method (with submaximal effort) in 155 forestry workers, 120 miners, 240 tool manufacturers (turners, planers etc.), 75 control-board operators. Differences were found according both to age and occupation.