The exercise electrocardiogram in trained and untrained adolescent males

Exercise electrocardiograms (Ex ECG) were performed on both trained and untrained adolescent males to determine whether a difference exists between the normal adolescent and normal adult male. Exercise was performed on a mechanically braked bicycle ergometer using an intermittent work load protocol, and the Ex ECG's were analyzed according to J-point displacement and ST segment slope. No J-point depression was seen and the ST segment slope was positive during exercise in both trained and untrained subjects. There was no difference in the J-point displacement or the ST segment slope between the trained and untrained subjects. This study suggests that any J-point depression during exercise may be abnormal in the adolescent male. Training does not have an effect on the J-point or ST segment at maximum exercise.     

Maximal oxygen uptake in trained and untrained 15-year-old boys.

The purpose of this study was to assess maximal aerobic power (VO2max) in trained and untrained 15-year-old boys. The trained subjects (18) were junior swimmers from a Belgrade swimming team, and the untrained ones (12) were from a Belgrade high school. VO2max was directly measured during progressive cycle ergometer exercise using open circuit spirometry. No significant differences in height, mass, percentage fat and vital capacity were noted between the trained and untrained groups. Maximal aerobic power (overall, relative and in relation to lean body mass) in absolute values, and expressed per kilogram of body mass and lean body mass, was 31.5%, 21.2% and 20.6%, respectively, higher in the trained than in the untrained group (P less than 0.05). These data suggest that physical training significantly increases maximal aerobic power in young subjects.     

Effects of submaximal intensity cycle ergometry for one hour on substrate utilisation in trained prepubertal boys versus trained adults

AIM: Substrate utilisation during exercise might be different in trained prepubertal boys compared to trained adults, so dietary advice usually given to endurance trained adults may need to be adapted for endurance trained children. METHODS: Experimental design: subjects pedalled for 1 hour on an ergocycle at 40% or 60% of Wmax (maximal aerobic power). Participants: 14 boys and 13 adults active in endurance sport (swimming). Measures: pulmonary respiratory gas-exchange ratio [RER = VCO(2)/VO(2)], used as the equivalent of the non protein respiratory quotient (RQ), was measured at rest, at the 15(th), 30(th), 45(thv and 60(th) min of exercise in order to calculate energy expenditure. RESULTS: Relative resting energy expenditure was significantly higher in boys than in adults. During exercise, energy expenditure (EE) was significantly lower in children than in adults (p<0.001), whereas fat-free mass relative EE was only influenced by intensity. Relative EE from carbohydrates (EE(CHO)) was lower in children compared to adults, even if the highest intensity involves a higher EE(CHO) in both groups (p<0.05). Boys oxidised more lipid at 40% of Wmax than 60% of Wmax or adults at either intensity. CHO utilisation was significantly increased at 60% vs 40% of Wmax, yet lower in boys than in men (p<0.01). Lipids' use, in g x min(-1) x kg-1)FFM, was significantly higher in boys than in men at 40% of Wmax (p<0.01). CONCLUSION: Trained children, at rest, had greater fat-free mass energy expenditure than adults, which may be linked to growth processes that remain unclear. During exercise, in boys, the main observation was the increase in CHO dependence relative with the intensity. Thus, it appears that CHO feeding is as important in endurance-trained boys as in endurance-trained adults, especially when exercise intensity approaches that of competition or training sessions.     

Voluntary and electromyostimulation forces in trained and untrained men.

Electromyostimulation (EMS) evoked responses of lower extremity muscles of sedentary or disabled subjects have been extensively studied to improve muscular strength and delay atrophy. However, it is not apparent whether EMS can serve a similar function in upper extremity muscles and in athletes. We compared the forces of maximal voluntary isometric contraction (MVC), percutaneous EMS-evoked tetanus, and EMS superimposed on MVC of the elbow flexors in six strength-trained and six untrained healthy men. Stimulation consisted of a 2.5-kHz alternating current sine wave modulated at 50 bursts.s-1 with a 50% duty cycle. Reliability of the criterion measures was assessed over 4 d and ranged from R = 0.746 to R = 0.948. Strength-trained men had 29% higher MVC than untrained controls (P less than 0.001). Untrained men tolerated 21.9 mA and trained men 31.3 mA of EMS current (P less than 0.021), yet tetanic forces were similar: 92.5 N vs 96.0 N (P greater than 0.196). These tetanic forces corresponded to 32% (untrained) and 24% (trained) of MVC (P less than 0.047). When EMS was superimposed on MVC, compared with MVC alone, force was significantly (P less than 0.048) lower by 10% (31 N, untrained) and 13% (55 N, trained). These data suggest that, independent of training status, percutaneous EMS reduces maximal voluntary elbow flexion forces and that tetanic forces may not be sufficiently high for purposes of muscular strength development or prevention of atrophy.     

Cardiac glycogenolysis in trained and untrained ischemic rat hearts.

The effect of induced myocardial ischemia on cardiac glycogen utilization was investigated in trained and untrained male Sprague-Dawley rats. Following a 12 to 15 week endurance training program, myocardial ischemia was induced by ligation of the left coronary artery. Prior to and at 5 min intervals following ligation, affected tissues of five trained and untrained animals were removed, frozen in liquid nitrogen, and analyzed for glycogen and lactic acid. The glycogen content for both groups declined significantly (p less than 0.05) during the first 5 min, 38% and 15% for the trained and untrained, respectively, with a concomitant rise in the lactic acid of 150% and 40%. Overall, the cardiac lactate in the trained hearts was lower (p less than 0.05) than in untrained hearts but the pattern of response was the same. During the final 5 min of ischemia, cardiac glycogen rose in the trained hearts and declined in the sedentary hearts. The difference between the two groups at 30 min was significant (p less than 0.05). The results show that trained and untrained rat hearts utilize glycogen differently but produce similar quantities of lactic acid during brief periods of myocardial ischemia. Similar lactate despite greater glycogen utilization may indicate reduced anaerobic stress in the trained rat heart.     

Atrioventricular plane displacement in untrained and trained females

PURPOSE: Female athletes often demonstrate changes in cardiac dimensions that are less prominent than in male athletes, and results from longitudinal studies are conflicting. The atrioventricular plane displacement (AVPD) in the heart is used as an index of left ventricular systolic function with the assumption that it is a more sensitive method for measuring myocardial contractility compared with left ventricular ejection fraction. The aim of the present study was to determine the effect of a short period of endurance training on cardiac dimensions in sedentary female subjects and to measure the AVPD at rest and during submaximal workload. METHODS: Twelve sedentary female subjects (21.9 +/- 1.3 yr, 168.8 +/- 3.5 cm, 64.0 +/- 6.6 kg, and 42.6 +/- 2.9 mL x kg(-1) x min(-1) in maximal oxygen uptake) were examined with echocardiography before and after a period of interval training (varying from 2 to 5 min at 90-95% of maximal heart rate, 3 d x wk(-1), 8 wk). RESULTS: Maximal oxygen uptake increased by 18% to 50.4 +/- 3.1 mL x kg(-1) x min(-1) (P < 0.001). Left ventricular mass increased from 123.9 to 139.2 g (P = 0.007). There was a significant increase in posterior wall thickness but no change in cavity size. The AVPD did not change at rest but increased significantly from 15.6 to 17.6 mm (P < 0.001) during exercise at 85-90% of maximal heart rate. CONCLUSION: This study shows that a short period of aerobic endurance training induces changes in the female heart, both in cardiac dimensions at rest and in left ventricular systolic function at submaximal workload. AVPD during submaximal exercise discriminate well between the untrained and trained healthy heart.     

Running velocity at blood lactate threshold of boys aged 6-15 years compared with untrained and trained young males

Running velocities at the blood lactate threshold, which was estimated by the velocity just below 2 mmol X l-1 of blood lactate, were measured in sixty-six 6- to 15-year-old boys during a graded exercise stress test on the track and compared with those of twenty-three 16- to 18-year-old young males and eighteen 18- to 23-year-old untrained young males. The boys were divided into five age groups: 6-7, 8-9, 10-11, 12-13, and 14-15. The mean velocity at the lactate threshold of all age groups was significantly higher than that of untrained young males and not different from that of trained young males. There was no significant difference between boys of all age groups, but a significant negative correlation between the velocity at the lactate threshold and bone maturity score (RUS score) of more than 200 was found in boys. Heart rates and percent maximal heart rate at the lactate threshold were dependent on age. These were significantly inversely related to the chronological age and RUS score. These results suggest that maturation is one of the factors influencing lactate threshold.     

Urinary excretion of free noradrenaline and adrenaline in trained and untrained men.

Measurements of free noradrenaline and adrenaline were made in the urine of 28 men sampled after rest and exercise prior to, and following six and twelve weeks of an excercise programme. The training consisted of thirty minutes of running and walking four times per week at an intensity estimated at 75% of the age-predicted maximum heart rate. A fifteen minute standardized cycle ergometer work test was conducted on all subjects prior to the training and following six and twelve weeks of training. Noradrenaline and adrenaline excretions in the urine were measured before and after the work test.     

Cardiovascular responses to Valsalva maneuver in physically trained and untrained normal subjects.

To elucidate whether the Valsalva maneuver (VM) can distinguish different degrees of normal ventricular function and parasympathetic tone, we studied 10 physically untrained and 18 trained normal individuals who regularly performed isotonic exercises. Both groups were submitted to an exercise stress test. An electrocardiogram and an M-mode echocardiogram were recorded before and during VM. The arterial pressure, heart rate and ventricular function responses to the maneuver were evaluated. The end diastolic volume, ejection fraction, circumferential fiber shortening and left ventricular posterior wall thickness were greater at rest in the trained group than in the untrained one. In both groups, during the straining phase of the VM the volumes and end systolic stress decreased and the systolic function indexes increased, but the changes were more pronounced in the trained subjects. In spite of these differences, the arterial pressure and heart rate responses were similar in both groups. It can thus be concluded that only changes in ventricular function distinguish physically trained vs untrained subjects during VM.     

Ventilatory responses of trained and untrained subjects during running and walking

To investigate the influence of stride frequency on ventilation in different subject populations, the ventilatory responses to walking and running at similar metabolic loads were studied in 29 males. Ten of the males were well-trained, highly fit runners (HFR), ten were well-trained, highly fit cyclists (HFC), and nine were healthy low-fit males (LFM) who did not engage in any form of regular exercise. All subjects completed two separate exercise bouts, a level run and an uphill walk, at 90% of their ventilatory threshold. Stride frequency was found to increase by 49% between the walk and run trials. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), end-tibial CO2 tension (PETCO2), end-tidal O2 tension (PETO2), and inspiratory time (TI) were all significantly different (P less than 0.05) between the walk and run trials for the HFR. Minute ventilation and expiratory time (TE) did not differ significantly between the walk and run trials for the HFC; however, VT, f, PETCO2, PETO2, and TI were significantly different. Only PETCO2 and TI were found to be significantly different between the walk and run trials for the LFM. These results suggest that stride frequency affects ventilation to varying degrees dependent upon the subject population and that the mechanisms for the hyperpnea of moderate exercise operating in each of these subject populations involve a complex interaction of many factors.     

Stress reactivity: hemodynamic adjustments in trained and untrained humans

There is mounting evidence to suggest a relationship between heightened cardiovascular (CV) and sympathetic nervous system (SNS) reactivity to behaviorally stressful situations and cardiovascular pathology. Exercise training has been suggested as a non-pharmacological, therapeutic intervention technique to counter behaviorally induced CV and SNS reactivity. This approach is based on well-documented adaptations in CV and SNS functioning that result from exercise training. However, the theoretical basis for the relationship between physical fitness and stress reactivity has not been fully explored. Additionally, there are methodological and design considerations that inhibit comparison and interpretation of research studies regarding the role of physical fitness or exercise training and cardiovascular and SNS reactivity during behavioral stress. The focus of our laboratory studies has been to more fully described the CV and SNS responses to behaviorally challenging novel and learned tasks in highly fit, exercise trained, and untrained college-age males. The results from these studies suggest that highly fit and untrained males exhibit similar CV and SNS responses to a novel task. However, upon repeated exposure to the task, fit individuals exhibit attenuated mean arterial pressure and cardiac output responses. The data from the longitudinal studies suggest that there is an exercise training induced attenuation in the cardiac output response to behavioral challenge and that this is at least partially the result of an attenuated stroke volume response to the task. Thus, exercise training does appear to alter cardiovascular functioning during familiar, behaviorally challenging situations.     

Hemoglobin mass and peak oxygen uptake in untrained and trained residents of moderate altitude.

Blood composition, hemoglobin mass (CO rebreathing method) and VO2peak were measured in 15 untrained (UT-Bogotá) and 14 trained males (TR-Bogotá) living at 2600 m of altitude, and in 14 untrained lowlanders (UT-Berlin). [Hb] amounted to 15.3 + 0.2(SE) g/dl in UT-Berlin, 17.4 + 0.2 g/dl in UT-Bogotá and 16.0 + 0.2 g/dl in TR-Bogotá. Hb mass was significantly higher in UT-Bogotá (13.2 + 0.4 g/kg, P < 0.01) and in TR-Bogotá (14.7 + 0.5 g/kg, P < 0.001) than in UT-Berlin (11.7 + 0.2 g/kg). In TR-Bogotá also plasma volume was expanded. Erythropoietin concentrations in UT-Bogotá and TR-Bogotá were not significantly increased. There was a positive correlation between blood volume and VO2peak for the pooled values of all subjects, if the oxygen uptake of UT-Berlin was corrected for an ascent to 2600 m. For the Hb mass - VO2peak relation two groups are indicated pointing to two types of altitude acclimatization with different Hb mass increases but similar distribution of aerobic performance capacity. We suggest that different genetic properties in a population of mixed ethnic origin might play a role.     

Cardiovascular response of trained and untrained old men to mental challenge

PURPOSE: The cardiovascular response to mental challenge of trained and untrained older men was examined. METHODS: Blood pressure, heart rate, stroke volume, cardiac output, total peripheral resistance (TPR), rate pressure product, and cardiac contractility of 10 aerobically trained (trained) and 10 untrained (untrained) older men during and recovering from the Stroop task were compared. Fitness was assessed by online, open-circuit spirometry using a bicycle ergometer. RESULTS: Trained compared with untrained men showed significantly lower absolute heart rate during and recovering from the Stroop and greater left ventricular ejection time recovering from Stroop. Delta TPR scores were greater for Trained during and recovering from the Stroop, whereas delta systolic blood pressure was greater recovering from Stroop. CONCLUSION: These results indicate that although aerobically trained men possessed lower absolute heart rate their change in TPR and systolic blood pressure during mental challenge was significantly greater than that of untrained older men. The greater vascular response of the trained to mental challenge may reflect greater sensitivity to alpha-adrenergic stimulation.