Pulmonary blood volume and interventricular circulation time in physically trained and untrained subjects.

Resting pulmonary plasma and blood volumes (PPV and PBV), interventricular circulation time (IVCT), cardiac and stroke index (CI and SI), heart rate (HR), total plasma and blood volumes (PV and BV) were determined in athletes (two male groups representing different types of sport activities, and one female group) and compared with those of non-athletes (one male and one female group). In addition to high maximal aerobic power, the athletes were characterized by greater SI, BV and PV and lower resting HR than non-athletes, PPV and PBV were significantly larger and IVCT significantly longer in the trained than in the untrained groups, probably reflecting an improved capacity of the pulmonary circulation. PPV as per cent of PV was almost equal in all the groups, indicating the same distribution of plasma between the pulmonary and systemic circulation. The data also indicate that total blood volume is an important determinant of the magnitude of the pulmonary vascular bed. The increased volume of flowing blood and increased stroke volume in athletes probably allows for a reduction in flow velocity and thereby a reduction in kinetic energy.     

Renal blood volume regulation in trained and untrained subjects during immersion

To study the cause of the increased blood volume of endurance-trained athletes we assessed the renal blood volume regulating mechanisms in eight untrained (UT) and eight endurance-trained (TR) male subjects during a 4 h head-out immersion. In TR plasma volume remained constant whereas it decreased in UT by 2.4 ml/kg (p less than 0.025). Immersion diuresis of TR was only half as high as in UT (peak values: 3.22 ml/min in UT, 1.60 ml/min in TR). Free water clearance remained approximately constant in UT but temporarily decreased in TR (p less than 0.001). This points to poor or even absent inhibition of antidiuretic hormone secretion in the latter group. Osmolar clearance increased less in TR than in UT (p less than 0.02) which was partly due to a delayed increase of glomerular filtration rate. Plasma osmolality, creatinine, and protein concentrations as well as hematocrit values were reduced during immersion to a similar extent in both groups. The results indicate a reduced renal response of endurance-trained subjects to congestion of the low-pressure system resulting in an increase in blood volume.     

Effect of food intake on exercise fatigue in trained and untrained subjects

The effects of carbohydrate and fat intake on exercise-induced fatigue was investigated in 30 untrained--(VO2max of 40.6 +/- 2.7 ml X kg-1 X min-1) and 24 trained-subjects (VO2max of 52.3 +/- 2.7 ml X kg-1 X min-1) performing a 34 km march with a 25 kg backpack. Marching time was 8 1/2 h and 6 1/3 h in the untrained and trained-subjects respectively. The subjects were divided into 3 dietary groups. One group had free access to sugar cubes, the second group was offered almonds and the third one served as a control. Triglyceride levels decreased by 65 mg X dl-1 in untrained, and by 115 mg X dl-1 in trained subjects, while blood glucose remained at normal levels. In the untrained subjects, ingestion of almonds delayed the subjective sensation of exhaustion, while 50% of the controls and the sugar consuming subjects complained of exhaustion. The data suggest that ingestion of food containing fat delays exercise induced exhaustion or fatigue to a greater extent than does carbohydrate ingestion.     

Differences in performance between trained and untrained subjects during a 30-s sprint test in a wheelchair ergometer

To compare physiological responses and propulsion technique of able bodied subjects with no prior experience of wheelchairs (AB) and wheelchair dependent subjects (WD), ten AB and nine WD performed a 30-s sprint test in a wheelchair ergometer. The WD had spinal cord injuries with a lesion at T8 or lower. The WD and AB did not show significantly different physiological responses. The power values averaged for the right wheel over the 30 s of the test were 50.2 (SD 14.7) W and 48.0 (SD 4.4) W for WD and AB, respectively. No significant differences in torque application could be discerned, although WD subjects seemed to have a more flattened torque curve with a smaller negative deflection at the beginning of the push. The WD applied a significantly higher horizontal propulsive force to the handrims but did not apply force more effectively. The percentages of effective force to total propulsive force were 61 (SD 16)% for WD and 57 (SD 4)% for AB. With regard to the kinematic parameters, AB followed the handrims significantly longer than WD (end angle AB 65°, WD 44°), started the push phase with their arms more in retroflexion and flexed their trunks further forward. The AB did however show a movement pattern comparable to that of wheelchair athletes measured in a comparable experiment. It could not be decided conclusively that inexperience in wheelchair propulsion led to a less effective propulsion technique. Despite the selection of WD with respect to lesion level, interindividual differences in terms of level of training may have been responsible for the absence of significant results.     

Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers

The influence of specific training on benefits from caffeine (Caf) ingestion was examined during a sprint test in a group of highly trained swimmers (T) and compared with the response of a group of untrained occasional swimmers (UT). Seven T and seven UT subjects swam freestyle two randomly assigned 2 x 100 m distances, at maximal speed and separated by 20 min of passive recovery, once after Caf (250 mg) and once after placebo (Pla) ingestion. Anaerobic capacity was assessed by the mean velocity (meters per second) during each 100 m and blood was sampled from the fingertip just before and 1, 3, 5, 7, and 9 min after each 100 m for resting and maximal blood lactate concentration ([la-]b,max) determination. The [la-]bmax was significantly enhanced by Caf in both T and UT subjects (P less than 0.01). However, only T subjects exhibited significant improvement in their swimming velocity (P less than 0.01) after Caf or any significant impairment during the second 100 m. In light of these results, it appears that specific training is necessary to benefit from the metabolic adaptations induced by Caf during supramaximal exercise requiring a high anaerobic capacity.     

EMG versus oxygen uptake during cycling exercise in trained and untrained subjects.

The aim of this study was to test the hypothesis that bicycle training may improve the relationship between the global SEMG energy and VO2. We already showed close adjustment of the root mean square (RMS) of the surface electromyogram (SEMG) to the oxygen uptake (VO2) during cycling exercise in untrained subjects. Because in these circumstances an altered neuromuscular transmission which could affect SEMG measurement occurred in untrained individuals only, we searched for differences in the SEMG vs. VO2 relationship between untrained subjects and well-trained cyclists. Each subject first performed an incremental exercise to determine VO2max and the ventilatory threshold, and second a constant-load threshold cycling exercise, continued until exhaustion. SEMG from both vastus lateralis muscles was continuously recorded. RMS was computed. M-Wave was periodically recorded. During incremental exercise: (1) a significant non-linear positive correlation was found between RMS increase and VO2 increase in untrained subjects, whereas the relationship was best fitted by a straight line in trained cyclists; (2) the RMS/VO2 ratio decreased progressively throughout the incremental exercise, its decline being significantly and markedly accentuated in trained cyclists; (3) in untrained subjects, significant M-wave alterations occurred at the end of the trial. These M-wave alterations could explain the non-linear RMS increase in these individuals. During constant-load exercise: (1) after an initial increase, the VO2 ratio decreased progressively to reach a plateau after 2 min of exercise, but no significant inter-group differences were noted; (2) no M-wave changes were measured in the two groups. We concluded that the global SEMG energy recorded from the vastus lateralis muscle is a good estimate of metabolic energy expenditure during incremental cycling exercise only in well-trained cyclists.     

Differences in the oxygenation of the forearm muscle during isometric contraction in trained and untrained subjects

The aim of this study was to test a hypothesis that a longer duration of isometric contraction is related to an increased oxygenation status of the muscle. A group of trained rock climbers and untrained subjects performed 15 kp sustained isometric contraction until fatigue set in. The oxygenation status was assessed using near infrared spectroscopy (ISS, USA). The results support the hypothesis. The concentration of relative oxygenated hemoglobin was higher in the rock climbers than in the untrained subjects. The relative total hemoglobin did not differentiate the two groups enough to show that blood volume also strongly influences contraction time.     

Perceptual and physiological responses to cycling and running in groups of trained and untrained subjects

An interesting aspect, when comparing athletes, is the effect of specialized training upon both physiological performance and perceptual responses. To study this, four groups (with six individuals each) served as subjects. Two of these consisted of highly specialized individuals (racing cyclists and marathon runners) and the other two of non-specialized individuals (sedentary and all-round trained). Cycling on a cycle ergometer and running on a treadmill were chosen as modes of exercise. Variables measured included heart rate, blood lactate and perceived exertion, rated on two different scales. Results show a linear increase of both heart rate and perceived exertion (rated on the RPE scale) in all four groups, although at different absolute levels. Blood lactate accumulation, during cycling and running, differentiates very clearly between the groups. When heart rate and perceived exertion were plotted against each other, the difference at the same subjective rating (RPE 15) between cycling and running amounted to about 15-20 beats.min-1 in the non-specialized groups. The cyclists exhibited almost no difference at all as compared to 40 beats.min-1 for the runners. It can be concluded that specialized training changes both the physiological as well as the psychological response to exercise.     

Phosphate determination during hypokinesia and ambulation in establishing phosphate changes in trained and untrained subjects

Hypokinesia (diminished movement) induces phosphate (P) changes; however, it is not known if P change is greater in trained than untrained subjects. Measuring P balance and P retention during hypokinesia (HK) and P load, we studied if changes in P retention and P depletion were significantly (p<0.05) greater in trained than untrained subjects. Studies were done during a 30-d pre-HK period and a 364-d HK period. Forty male trained and untrained healthy individuals aged 24.5±5.4 yr were chosen as subjects. All volunteers were equally divided into four groups: trained ambulatory control subjects (TACS), trained hypokinetic subjects (THKS), untrained ambulatory control subjects (UACS), and untrained hypokinetic subjects (UHKS). All THKS and UHKS were limited to an average walking distance of 0.3 km/d, and TACS and UACS were on an average running distance of 9.8 and 1.8 km/d, respectively. Subjects took daily 12.7-mmol dicalcium-phosphate/kg body weight in the form of supplementation. Negative P balance, fecal P loss, urinary P and calcium (Ca) excretion, serum P, and total Ca (Ca_t) levels increased significantly (p<0.05), whereas P retention, serum 1,25-dihydroxyvitamin D [1,25 (OH)₂D₃] and intact parathyroid hormone (iPTH) level decreased significantly (p<0.05) in THKS and UHKS when compared with their pre-HK values and their respective ambulatory controls (TACS and UACS). However, P retention, P balance, serum, urinary, and fecal P, and serum hormone level changed significantly (p<0.05) more in THKS than UHKS. Retention of P, fecal P, urinary P and Ca loss, serum P and Ca_t level, P balance, 1,25(OH)₂D₃, and iPTH level change insignificantly (p>0.05) in TACS and UACS when compared with their pre-HK control values. It was concluded that significant negative P balance may indicate P depletion, whereas significant P loss in spite of negative P balance and P load may suggest P retention incapacity; however, P depletion was greater in THKS than UHKS. Clearly, P is wasted much more in THKS than UHKS.     

Proteomic analysis and protein carbonylation profile in trained and untrained rat muscles

Understanding the relationship between physical exercise, reactive oxygen species and skeletal muscle modification is important in order to better identify the benefits or the damages that appropriate or inappropriate exercise can induce. Unbalanced ROS levels can lead to oxidation of cellular macromolecules and a major class of protein oxidative modification is carbonylation. The aim of this investigation was to study muscle protein expression and carbonylation patterns in trained and untrained animal models. We analyzed two muscles characterized by different metabolisms: tibialis anterior and soleus. Whilst tibialis anterior is mostly composed of fast-twitch fibers, the soleus muscle is mostly composed of slow-twitch fibers. By a proteomic approach we identified 15 protein spots whose expression is influenced by training. Among them in tibialis anterior we observed a down-regulation of several glycolitic enzymes. Concerning carbonylation, we observed the existence of a high basal level of protein carbonylation. Although this level shows some variation among individual animals, several proteins (mostly involved in energy metabolism, muscle contraction, and stress response) appear carbonylated in all animals and in both types of skeletal muscle. Moreover we identified 13 spots whose carbonylation increases after training.     

Physiological characteristics of system quanta of athletic performance

Physiological mechanisms of muscle activity during cyclic physical exercises of various intensity, including individual maximum exercise intensity, have been studied in 30 athletes. The system quantization of behavior showed that the spectral components of heart rate variability during attainment of individual maximum exercise intensity by athletes change in different directions. An increase in the individual maximum exercise intensity is accompanied by an increase in the maximum movement pace after each system quantum of muscle activity and is performed at a lower heart rate. This increases the absolute spectral power of the EEG β₂ range, and each system quantum of physical activity induces adequate triggering of autonomic mechanisms ensuring the activity. The results of this study may be used for professional selection or development of criteria of the endurance of athletes with regard to high cyclic exercise intensities.     

Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects

Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%VO2max) as a normalising independent variable is valid despite significant differences in the absolute VO2max of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine VO2max and lactate threshold. The subjects were grouped as trained (T) if their VO2max exceeded 60 ml.kg-1.min-1, and untrained (UT) if their VO2max was less than 50 ml.kg-1.min-1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% VO2max. The allocation of each exercise session (50% or 70% VO2max) was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (- 10 min), just prior to the commencement of exercise (0 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [Cl-], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (VO2) and related variables were measured at two time intervals (14-15 and 34-35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% VO2max for heart rate (fc) and venous [la-].(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of dropping height on jumping performance in trained and untrained prepubertal boys and girls

Plyometric training in children, including different types of jumps, has become common practice during the last few years in different sports, although there is limited information about the adaptability of children with respect to different loads and the differences in performance between various jump types. The purpose of this study was to examine the effect of gender and training background on the optimal drop jump height of 9- to 11-year-old children. Sixty prepubertal (untrained and track and field athletes, boys and girls, equally distributed in each group [n = 15]), performed the following in random order: 3 squat jumps, 3 countermovement jumps (CMJs) and 3 drop jumps from heights of 10, 20, 30, 40, and 50 cm. The trial with the best performance in jump height of each test was used for further analysis. The jump type significantly affected the jump height. The jump height during the CMJ was the highest among all other jump types, resulting in advanced performance for both trained and untrained prepubertal boys and girls. However, increasing the dropping height did not change the jumping height or contact time during the drop jump. This possibly indicates an inability of prepubertal children to use their stored elastic energy to increase jumping height during drop jumps, irrespective of their gender or training status. This indicates that children, independent of gender and training status, have no performance gain during drop jumps from heights up to 50 cm, and therefore, it is recommended that only low drop jump heights be included in plyometric training to limit the probability of sustaining injuries.