The aim of this investigation was to study how the known dependence of working efficiency on pedaling frequency is influenced by the work load as well as by physical fitness. Oxygen uptake, CO2 output, ventilation, heart rate, and lactate concentration in capillary blood from the earlobe were determined at varying combinations of work loads and pedaling rates in road-racing cyclists and medical students. Respiratory exchange ratio, consumption of energy, gross efficiency, net efficiency, and delta efficiency (delta work rate/delta metabolic rate) were calculated. All parameters showed a nonlinear dependence on pedaling frequency. The lowest oxygen uptake and the highest efficiency shifted to higher frequencies with increasing work load. Delta efficiency increased with rising pedaling frequency. Differences of VO2 and efficiencies between trained and untrained subjects were only small. Most effects can be explained by variations in leg movement frequency and recruitment of muscle fibers. There is evidence that racing cyclists chose pedaling rates yielding optimal efficiency at any load.

The effect of three weeks ergometer training (Tr) 5 times a week for 45 min at 70% VO2max by 6 subjects on erythrocyte turnover and haemoglobin O2 affinity has been studied. Increased reticulocytosis could be observed from the second day after beginning Tr until a few days after its end, probably caused by increased erythropoietin release by the kidney. Erythrocyte destruction was most pronounced in the first and markedly reduced in the third week of Tr. Elevated glutamate oxalacetate transaminase activity and creatine as well as lowered mean corpuscular haemoglobin indicate a younger erythrocyte population in the first week of recovery. Total blood volume increased during the course of Tr by 700 ml, mainly caused by a raised plasma volume (74%). Red cell volume increased later with maximal values one week after Tr (+280 ml). In this week the standard oxygen dissociation curve was most shifted to the right (P50 increased from 3.77 +/- 0.05 kPa to 3.99 +/- 0.07 kPa) and the Bohr coefficients had their lowest values. Both effects are completely explainable by the haemoglobin O2 binding properties of young erythrocytes. After training, all parameters of physical performance (VO2max, maximal workload, heart rate during rest and exercise) were markedly improved, indicating fast adaptation mechanisms. The increased erythrocyte turnover, including higher erythropoiesis, seems to be one important part of these effects.

No abstract

The purpose of this study was to investigate the effects of prolonged exercise with and without a thermal clamp on neutrophil trafficking, bacterial-stimulated neutrophil degranulation, stress hormones, and cytokine responses. Thirteen healthy male volunteers (means +/- SE: age 21 +/- 1 yr; mass 74.9 +/- 2.1 kg; maximal oxygen uptake 58 +/- 1 ml x kg(-1) x min(-1)) completed four randomly assigned, 2-h water-immersion trials separated by 7 days. Trials were exercise-induced heating (EX-H: water temperature 36 degrees C), exercise with a thermal clamp (EX-C: 24 degrees C), passive heating (PA-H: 38.5 degrees C), and control (CON: 35 degrees C). EX-H and EX-C was comprised of 2 h of deep water running at 58% maximal oxygen uptake. Blood samples were collected at pre-, post-, and 1 h postimmersion. Core body temperature was unaltered on CON, clamped on EX-C (-0.02 degrees C), and rose by 2.23 degrees C and 2.31 degrees C on EX-H and PA-H, respectively. Exercising with a thermal clamp did not blunt the neutrophilia postexercise (EX-C postexercise: 9.6 +/- 1.1 and EX-H postexercise: 9.8 +/- 1.0 x 10(9)/liter). Neutrophil degranulation decreased (P < 0.01) similarly immediately after PA-H (-21%), EX-C, and EX-H (-28%). EX-C blunted the circulating norepinephrine, cortisol, granulocyte-colony stimulating factor, and IL-6 response (P < 0.01) but not the plasma epinephrine and serum growth hormone response. These results show a similar neutrophilia and decrease in neutrophil degranulation after prolonged exercise with and without a thermal clamp. As such, the rise in core body temperature does not appear to mediate neutrophil trafficking and degranulation responses to prolonged exercise. In addition, these results suggest a limited role for cortisol, granulocyte-colony stimulating factor, and IL-6 in the observed neutrophil responses to prolonged exercise.