Bruno Balke

Refinements in method of evaluation and physical conditioning before and after myocardial infarction

Abstract A 54 year old white man with hypertension, obesity and an elevated serum cholesterol level volunteered for a physical training program. During the sixth week he became ill, and a repeated work-capacity test revealed physiologic evidences of myocardial insufficiency. The pre-exercise serum glutamic oxaloacetic transaminase level was elevated. A routine electrocardiogram four hours later revealed evidence of an acute inferoseptal myocardial infarction. The course of the disease was uneventful and uncomplicated. Two months after infarction the patient resumed a physical activity program which provided for a slow increase in metabolic demands compatible with his capacity. Repeated work-capacity tests 20 and 23 weeks after infarction showed that he responded to training in exactly the same manner as has been observed in normal, healthy individuals. At that time he was normotensive, with a normal serum cholesterol concentration and near-normal body weight. The capacity for adequate cardiorespiratory adjustments to high metabolic demands was rated as “good.” This study illustrates how performance tests can be used in evaluating the work capacity and progress of a cardiac patient.

Aerobic requirements of overground versus treadmill running.

There is general agreement that the oxygen demand of level running is similar for both the treadmill (TM) and overground situations at speeds under 260 m X min-1. However, controversy exists with regard to inclined running. The prevailing view, represented by the ACSM prediction formulas, is that overground hill running is theoretically more costly than inclined treadmill running. This study was designed to investigate the problem from an empirical standpoint. Seven male subjects performed overground and TM running at two grades (0 and 5.7%) over a range of speeds between 136-286 m X min-1. For the outdoor trials, subjects covered a distance of 950 m at a constant pace, and expired gas was collected over the last 150 m. Matching trials were then performed on the treadmill at the same speed and % grade. Regression lines were calculated for speed vs oxygen consumption (VO2). For TM and overground level running, these were: VO2 (ml.kg-1.min-1)= 0.222 X speed (m.min-1) - 1.33 and VO2 (ml.kg-1.min-1) = 0.202 X speed (m.min-1) + 3.21 respectively. The regression lines from TM and overground inclined running were: VO2 (ml.kg-1.min-1) = 0.237 X speed (m.min-1) + 7.53. and VO2 (ml.kg-1.min-1) = 0.233 X speed (m.min-1) + 7.78 respectively. A 2 X 3 X 2 ANOVA revealed that the differences between mean values for VO2 for level TM running vs level overground running and grade TM running vs grade overground running were not statistically significant (0.10 less than P less than 0.25).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac performance in relation to altitude

Abstract Decrease of atmospheric air density causes reductions of alveolar and arterial oxygen pressure and of arterial oxygen saturation. Acute exposure to lowered barometric pressure necessitates an increased blood flow, with or without a rise in pulmonary ventilation. When compensating for decreased arterial oxygen content by increased flow, the heart reaches performance limits at lower total energy expenditures. In chronic hypoxia the stimulation of erythropoiesis and the resulting greater arterial oxygen content tend to “normalize” cardiac work, at least as judged by the return of heart rates to more normal values. General capillary dilatation and decrease in peripheral resistance also may help to reduce the hearts work load. During acclimatization to altitude, an augmentation of total blood volume is usually observed. A substantial part of the additional blood volume is apparently absorbed by the lungs. Due to a resistance developing somewhere peripheral to the pulmonary alveolar capillaries, an arteriolar dilatation occurs, the quantity of blood in the lungs increases, pulmonary artery pressure goes up and hypertrophy of the right ventricle becomes evident. The greater demands on the right heart, in hypoxia, must be reflected in an increase of total cardiac work required for identical conditions of rest and physical work. An attempt was made to estimate the work of the heart, its oxygen requirements and the demands on coronary blood flow from measured and/or estimated parameters such as blood pressure, stroke volume, heart rate, hemoglobin and arterial and myocardial oxygen tensions. Resting values of coronary flow thus estimated (at sea level) compared favorably with “text book figures.” Similar evaluations of work situations under normal and reduced atmospheric air pressures lead to the conclusion that limitations in maximal coronary blood supply determine the range of cardiac performance capacity and, therefore, the individual range of physical working capacity, under normal atmospheric conditions as well as at altitude.

Energiebedarf im Hochgebirge

Zusammenfassung1.Wir fanden den Energieverbrauch im Gebirge höher als bisher bekannt war. Ein Arbeitsumsatz von 720 Cal. in der Stunde stellt keine Ausnahme dar, sondern gehört bei dem guttrainierten Bergsteiger für den Aufstieg zur Regel. D. h. also, daß dieser für die Zeit der Arbeit den lofachen Grundumsatz hat. 2. Dieser hohe Verbrauch wird mehrere Stunden hintereinander durchgehalten. Dermaximale Energieumsatz, d. i. Arbeits-+ restlicher Ruheumsatz, ist mit 9000–10 000 Cal. anzunehmen, ganz gleich, ob er, wie wir beim Skilanglauf gesehen haben, durch einen 15fachen Grundumsatz während 4–7 Std. oder durch einen 10fachen während 12 Std. Arbeitszeit erzielt wird. Der Energieverbrauch für durchschnittliche Hochleistungen, die etwa 2–4 Wochen durchgehalten werden können, liegt bei 6000 Cal. 3. Der Organismus vermag bei solch längerdauernder schwerster Arbeit durch Nahrungsaufnahme bis zu 5500–6000 Cal. täg-lich den Energieverbrauch weitgehend auszugleichen. 4. Am Tage nach langdauernden und anstrengenden Arbeitsleistungen ist der Grundumsatz auch beim Trainierten, der im Talort keine Steigerung mehr zeigt, in größeren Höhen gesteigert.