The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

A theoretical model has been proposed relating physical effort to perceived exertion. The model has been applied to a comparative investigation of the perception of various forces exerted by the adductor pollicis muscle and the quadriceps in five male subjects. The increase in perception of effort with increasing applied force in both muscle groups has been shown to increase exponentially. A force constant, defined in the paper, as the applied force at which perception of effort approximates two-thirds of maximum seems to discriminate effectively between the muscle groups concerned. The description of psychophysical data in this concise quantifiable manner may offer better insight into physiological processes contributing to the appreciation of effort.

Summary. The effects of three different physical training programmes on the control of sinoatrial rate in the young male rat were investigated. After training for 8 weeks, 5 d/week, the intrinsic rate and chronotropic response to cumulatively applied norepinephrine (NEp) were examined using isolated atrial preparations. Preparations from animals trained by walking for 60 min/d at 16-1 m/min possessed the same intrinsic atrial rate as sedentary controls, while preparations from an endurance-trained group running for 60 min at 32-2 m/min at 15% grade, and from a sprint-trained group running 50, 10-s efforts at 80-5 m/min, 15% grade with a 30-s rest interval, possessed lower intrinsic atrial rates. Atrial preparations from all groups demonstrated similar maximum rates after application of NEp. For all groups there was no statistically significant difference between the ECJQ values for the chronotropic effect of NEp. Training induced a modification in intrinsic atrial rate without influencing NEp chronotropic responses.

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