QTc interval prolongation during recovery from brief high-intensity intermittent exercise in obese adults.

The risk of malignant arrhythmias is higher during extremely intense exercise and after its cessation. It is still unclear whether high-intensity interval exercise (HIE), an increasingly popular option in preventive and rehabilitative medicine, can lead to an impaired electrophysiological milieu, as revealed by QT interval prolongation on an electrocardiogram. This study investigated heart rate-corrected QT interval (QTc) dynamics during recovery from HIE in obese adults. In total, 13 obese males (age: 24.3 ± 4.6 years old; body mass index: 31.6 ± 4.1 kg/m2) underwent: (1) HIE: an HIE session of four 30-s all-out cycling efforts interspersed with 4­min recovery periods; (2) REC: a recovery session 24 h after HIE; and (3) CON: a control session of no treatment. The QT interval was measured before HIE, REC, and CON, and then at 30-min intervals thereafter, for up to 3 h. QTc values were obtained using Bazett, Fridericia, Framingham, Hodges, and Rautaharju correction formulas. Acute HIE led to a significant increase in QTc for each correction (by 5-47 ms, all p < 0.05), and QTc was significantly longer during early recovery from acute exercise (HIE) compared with CON corrected with the Bazett (by 49 ms), Fridericia (by 11 ms), Hodges (by 27 ms), and Rautaharju (by 15 ms) formulas (all p < 0.05). Further, the QTc for each correction at most of the observation points in the REC trial was significantly longer (by 5-10 ms, all p < 0.05) than the corresponding value of the CON. In conclusion, in obese adults, the risk of QTc prolongation increased after brief HIE, and the risk may be sustained for more than 24 h.

Impact of exercise intensity on cardiac function in adolescent runners.

BACKGROUND: Prolonged exercise may induce a transient reduction in the left ventricular (LV) function (exercise-induced cardiac fatigue) in adults. However, data related to the cardiovascular consequences of prolonged exercise in adolescents are extremely limited. This study examined the impact of exercise intensity adopted in routine long-distance run training on LV function in trained adolescent runners in a laboratory-based setting. METHODS: Twelve male adolescent runners (14.5 ± 1.5 years) performed two 90-min treadmill runs with intensity set at the running speeds that corresponded to either 80% (T1) or 100% (T2) ventilatory threshold. LV function was examined echocardiographically pre- and post-exercise. RESULTS: The two-factor repeated-measures ANOVA revealed no significant (P>0.05) main effects for the intensity and the interaction of intensityÍ pre- and postexercise in ejection fraction (EF), systolic blood pressure/end systolic volume ratio (SBP/ESV) and early to atrial diastolic flow velocity ratio (E:A). Nevertheless, the main effect for time course in EF was significant (P<0.05). Pre-exercise EF in T1 (74 ± 5 vs. 70 ± 5%, P<0.05), but not in T2 (75 ± 4 vs. 72 ± 7%, P>0.05), decreased significantly post-exercise, yet this did not reach clinical levels. Further, no difference (P>0.05) was found between pre- and post-exercise in SBP/ESV (T1: 3.9 ± 0.9 vs. 3.7 ± 1.1; T2: 4.0 ± 0.7 vs. 4.6 ± 1.9 mmHg·ml⁻¹) and E:A (T1: 1.87 ± 0.11 vs. 1.87 ± 0.11; T2: 1.83 ± 0.11 vs. 1.87 ± 0.09) in both trials. CONCLUSION: These findings suggest that the training intensities adopted in routine long-distance run training in the adolescent runners do not seem to induce cardiac fatigue. Adolescent hearts appear to cope well with prolonged run performed on training.

The influence of a half-marathon race upon cardiac troponin T release in adolescent runners.

OBJECTIVES: Post-exercise cardiac troponin T (cTnT) release has been widely reported in adult athletes but limited data is available for adolescents. The aim of this study was to determine the incidence and magnitude of cTnT appearance in a large group of adolescent runners, and to determine any association between cTnT release and personal characteristics of adolescents. METHODS: We recruited 63 adolescent runners (mean±SD: age 16.4±1.5 years; 10 females) who all completed a simulated half-marathon race (an all-out 21-km run) during routine training. Personal data collected included age, training history, 21-km run performance as well as pre-post exercise serum cTnT levels. Serum cTnT was assayed using a 3rd generation assay. RESULTS: At pre-exercise, cTnT concentrations were below the 0.01 µg/L cTnT detection limit of assay in 58/63 runners. The post-exercise cTnT level (range: <0.01-1.36 µg/L) was significantly (p<0.001) greater than that of the pre-exercise (range: <0.01-0.02 µg/L). After the exercise, 57 (90%) and 44 (70%) subjects had cTnT concentrations above the detection: 0.01, and clinical thresholds: 0.05 µg/L, respectively. Post-exercise cTnT was inversely correlated with training years (r=-0.25, p<0.05) and age (r=-0.31, p<0.05). Compared with runners who had trained for ≥ 3 years, runners with less training experience demonstrated increased post-race cTnT levels (p<0.01). CONCLUSION: cTnT increases are virtually universal among adolescent runners following a 21-km run during routine training and can reach levels typically diagnostic for acute myocardial infarction potentially initiating diagnostic dilemmas. Adolescents with less training experience had higher post-exercise cTnT.

Resting and post-exercise serum biomarkers of cardiac and skeletal muscle damage in adolescent runners.

This study examined the response of serum biomarkers of cardiac and skeletal muscle damage at rest and after a routine workout of 21 km run in 12 male adolescent (16.2±0.6 years) long-distance runners. Biomarkers of cardiac [troponins (cTnT, cTnI), creatine kinase MB mass (CK-Mbmass)] and skeletal muscle [creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and hydroxybutyrate dehydrogenase (HBD)] damage were assayed at rest, 2, 4 and 24 h post-exercise. At rest, cTnT and cTnI were not detectable; however, CK, CK-MBmass, AST, ALT and HBD were above corresponding clinical cut-off values. Post-exercise significant elevations above rest were observed for all biomarkers, except ALT, 2 and 4 h following the run, and remained elevated in cTnI, CK, CK-MBmass, LDH and AST 24 h post-workout. A significant increase in data points above clinical cut-off values from rest to post-exercise was reported for cTnT, cTnI and CK at 2 and 4 h, and in cTnI and CK 24 h post-exercise. In conclusion, a 21 km run in adolescent runners increased post-exercise biomarkers of cardiac and skeletal muscle damage.

Serum cardiac troponin T in adolescent runners: effects of exercise intensity and duration.

The purpose of this study was to evaluate the interactive effects of exercise duration and intensity on the elevation of serum cardiac troponin T (cTnT) in trained adolescent athletes following prolonged exercise in a laboratory-based setting. Thirteen male adolescent runners (mean age 14.8+/-1.6 year) performed two 45-min and two 90-min constant-load treadmill runs with intensities set at the running speeds that corresponded to either 80% or 100% ventilatory threshold (Th(vent)): 80%Th(vent)45 min, 80%Th(vent)90 min, 100%Th(vent)45 min and 100%Th(vent)90 min. Serum cTnT was assessed pre and post exercise. In the 100%Th(vent)45 min trial, the post-exercise serum cTnT level [(Median) 0.015 ng x ml(-1); (Range)<0.01-0.375 ng x ml(-1)] was greater than that of the 80%Th(vent)45 min (undetectable cTnT) and 80%Th(vent)90 min (detectable cTnT in two subjects, 0.021 and 0.133 ng x ml(-1)) trials (P<0.01). The serum cTnT level was further increased in the 100%Th(vent)90 min trial [(Median) 0.063 ng x ml(-1); (Range)<0.01-0.417 ng x ml(-1)] when the treadmill run was sustained for an additional 45 min (P<0.05). Similar changes were observed in the cTnT positive rate in subjects. These findings suggest that exercise duration and intensity are essential factors in eliciting cTnT release interactively following an endurance exercise. Nevertheless, exercise intensity compared to duration appears to cause a more pronounced increase in cTnT levels.

Serum cardiac troponin response in adolescents playing basketball.

Cardiac troponin release is generally found in adult athletes after continuous-type endurance exercises or sport competitions. The purpose of this study was to investigate whether the physical stress experienced by adolescents while playing basketball, an intense, intermittent-type sport, could induce transient elevations of the serum cardiac troponin T (cTnT) and I (cTnI). Serum cTnT and cTnI levels in 10 male adolescent players (age 15.0 +/- 0.7 yr) were assessed immediately before and at 2, 4 and 24 h after a game randomly selected from a preseason basketball-training program. At 4 h following the game, serum cTnT levels in four of the ten subjects were above the cutoff of 0.01 ng . ml (-1) for myocardial injury. Two of these four subjects had values higher than the acute myocardial infarction cutoff of 0.05 ng . ml (-1). In three of the four subjects, the serum cTnI was above the cutoff of 0.06 ng . ml (-1) for myocardial injury. Nevertheless, serum cardiac troponins at 24 h had returned to pre-exercise levels. These findings suggest that the physical stress encountered during intense, intermittent-type sports could cause release of cardiac troponins in some adolescents at low risk for cardiac disease.

Changes in serum cardiac troponins following a 21-km run in junior male runners.

AIM: This study was designed to examine the appearance and clearance characteristics of serum cardiac troponin T (cTnT) and I (cTnI) in junior runners after an exhaustive 21-km run. The dependence of the alternations of the cardiac troponins on the runners' training status reflected in training years, running ability and physiological profile at ventilatory threshold (Th(vent)) was also examined. METHODS: Ten trained male adolescents (16.2+/-0.6 years) performed 21-km run and graded treadmill exercise with maximum effort on two different days. cTnT and cTnI immediately before and 2, 4 and 24 hours after exercise were measured in the 21-km trial. The parameters at Thvent including the running speed (Th(vent)-Speed) and VO2 (Th(vent)-VO2) were identified in the graded exercise trial. RESULTS: Serum cTnT and cTnI in 6 of the 10 subjects measured 4 hours after the 21-km run were above the myocardial injury cutoffs of 0.03 and 0.09 ng x mL(-1), respectively, but returned towards pre-exercise levels within 24 hours that were not in the same manner observed in the clinical situation of myocardial infraction. The 6 subjects' training status was generally lower than that of the rest 4. Further, subjects' 4-h serum cTnT and cTnI were negatively related to their training years, Th(vent)-Speed and Th(vent)-VO2, and positively related to their personal best in half- and full-marathon races (r2 = or > 36%, n = 10). CONCLUSIONS: Such findings implied that clinicians based the diagnosis of long-distance run-induced myocardial infraction in novice junior runners upon the transient postexercise elevations of cardiac troponins alone should be with caution.

The murine gene encoding parathyroid hormone: genomic organization, nucleotide sequence and transcriptional regulation.

The type 1 parathyroid hormone receptor (PTHR1) binds, with equal affinity, two ligands with distinct biological functions: PTH, the major peptide hormone controlling calcium homeostasis, and the paracrine factor, PTH-related peptide (PTHrP), a local regulator of cellular proliferation and differentiation. To clarify the complexity of possible interactions between two distinct ligands, PTH and PTHrP, and their common receptor in the intact organism, and to identify as yet unrecognized roles for PTH in normal physiology, we have cloned and characterized the structural organization, nucleotide sequence and transcriptional regulation of the murine gene encoding PTH. One recombinant clone isolated from a mouse genomic library contained 14 kb of DNA, encompassing the entire Pth gene. The transcriptional unit spans 3.2 kb of genomic DNA and, analogous to the human PTH gene, it is interrupted by two introns. The deduced mRNA encodes the 115-amino acid precursor, preproPTH. Comparison of the murine preproPTH sequence with other mammalian forms of the protein shows it to be highly conserved and to share limited structural similarity to PTHrP at the amino-terminal region, a domain critical for binding and activation of their common receptor. Putative binding motifs for the transcription factors sex-determining region Y gene product, transcriptional repressor CDP, hepatic nuclear factor 3beta, GATA-binding factor 1, glucocorticoid receptor, SRY-related high mobility group box protein 5 and cAMP response element binding protein were identified in the 5' flanking region of the Pth gene. When placed upstream of a reporter gene, these sequences failed to confer transcriptional regulation in response to 1,25(OH)(2) vitamin D(3), but responded positively to the addition of isoproterenol and forskolin. Mutational analysis identified a cAMP-response element in the Pth promoter.

Nostril dilatation increases capacity to sustain moderate exercise under nasal breathing condition.

BACKGROUND: Effect of nasal breathing without and with nostril dilatation on sustainability of moderate exercise (75% VO2max) and selected respiratory variables were examined. EXPERIMENTAL DESIGN: Nine healthy male subjects completed three randomly assigned exhaustive treadmill runnings under three breathing conditions: (i) oronasal breathing (CON), (ii) nasal breathing with external nasal dilator strip (NBENDS), and (iii) nasal breathing with fake nasal strip (NBFNS). RESULTS: Pre-exercise peak nasal inspiratory flow was increased with NBENDS but not with NBFNS. Pre-exercise nasal 12-sec maximum voluntary ventilation with NBENDS was greater than that with NBFNS while both were less than oronasal value. Exercise time to exhaustion in NBFNS trial, which was 23.6+/-6.7% less than the CON value, increased 31.9+/-12.3% under NBENDS condition. During exercise at exhaustion, although the difference in ventilation among all trials was not significant, lower breathing frequency in NBFNS and NBENDS exercises and higher end-tidal CO2 tension in NBFNS trial were found in comparison to CON values. Ratings of perceived magnitude of breathing effort (RPMBE) and exertion (RPE) at exhaustion were similar among all trials. However, RPMBE at exhaustion during NBFNS exercise was higher than that at the iso-time point during CON and NBENDS exercises. Similar result in RPE was found between NBFNS and CON exercises. After exercise, maximum inspiratory and expiratory pressures reduced. The reduction of each variable was similar among the three trials. CONCLUSIONS: Nasal breathing reduces the sustainability of moderate exercise measured under oronasal breathing condition. Nostril dilatation increases the capacity to sustain moderate exercise under nasal breathing condition.

Reliability of a 5-min running field test and its accuracy in VO2max evaluation.

BACKGROUND: Five-min running field test (5_RFT) was established for determining individuals' maximal aerobic velocity (V(amax)) and functional aerobic capacity (VO2peak) during horizontal run. We determined the number of trials required for establishing high reliability of the 5_RFT and examined its accuracy in evaluating individuals' maximal aerobic capacity (VO2max). METHODS: The V(amax)(5) recorded during the 5_RFT on four separate days was compared in 45 subjects (14 male, 31 female, 17.0+/-0.2 yrs) of various levels of physical fitness. The accuracy of VO2max evaluation using V(amax)(5) was examined via regression analysis in additional 23 male subjects (20.7+/-0.3 yrs). RESULTS: The mean correlation coefficient of V(amax)(5) among four trials was 0.94. Intraclass reliability coefficient across all trials was 0.98. For trial 3 and 4, the mean value of subjects' V(amax)(5) was higher than that of trial 1 and 2. V(amax)(5) of trial 2 was also higher than that of trial 1 while no difference was found between trial 3 and 4. F-test of equality of variances demonstrated similar sample variance of V(amax)(5) in all trials. Within-subject coefficient of variation in V(amax)(5) was 3.7 percent for all trials was reduced to 2.4 percent for trial 3 vs 4. For examining the accuracy in VO2max evaluation, regression analysis revealed that the V(amax)(5) explained 35.0 percent of the variance of measured VO2max (SEE = 5.64 ml x kg(-1) x min(-1)). CONCLUSIONS: The 5_RFT is reliable in determining V(amax)(5). Nevertheless, two familiarization sessions are recommended for achieving the best performance in the test. The 5_RFT cannot evaluate VO2max with reasonable accuracy in young males.

Effect of nostril dilatation on prolonged all-out intermittent exercise performance.

BACKGROUND: This study was designed to examine whether nostril dilatation would affect the ventilatory muscle (VM) function and the mean power output (PO) during prolonged all-out intermittent exercise. METHODS: Eight untrained young male subjects each completed 30 bouts of all-out exercise 20-sec each on a cycle ergometer interspersed with 40-sec recovery periods under (i) normal breathing and (ii) nostril dilatation conditions. For nostril dilatation, external nasal dilator (END) was used. Pre-exercise peak nasal inspiratory flow (PNIF), pre- and postexercise maximum inspiratory (MIP) and expiratory pressures were assessed in all trials. During exercise, ratings of perceived magnitude of breathing effort (RPMBE) and exertion (RPE) were recorded at 5-min intervals while ventilation, tidal volume, breathing frequency and oxygen consumption (VO2) were measured at 20-sec intervals. RESULTS: Inspiratory muscle fatigue occurred during control trial as MIP reduced from 155.1+/-25.3 cm H2O to 140.5+/-31.2 cm H2O after the exercise. Pre-exercise PNIF was increased with END from 3.1+/-0.8 l x sec(-1) to 3.8+/-1.0 l x sec(-1) showing that the nasal airflow resistance was reduced. Using END during exercise eliminated inspiratory muscle fatigue (no change in post-exercise MIP), and resulted in low average RPMBE and RPE, and high PO in comparison with the control values. In addition, the augmentation of PO was concomitant with no change in the average values of the VO2 and the ventilatory parameters. CONCLUSIONS: Exercise-induced VM fatigue occurs during the prolonged all-out intermittent exercise. Nostril dilatation with END during the exercise results in eliminating the VM fatigue and improving the PO.

Complete denture problem solving: a survey.

An investigation was carried out into the problems experienced by 114 referred patients with complete dentures who were considered to be difficult or to have difficult prosthodontic problems. The commonest problems were those of pain and lack of retention, due mainly to occlusal discrepancies and excessive VDO. Treatment was carried out on an individual basis with a large proportion of dentures being remade. However, a small number was satisfied by counselling alone without procedural treatment. A diagnostic denture technique was used for particularly difficult cases. This technique showed that, in two cases, technical prosthodontic inadequacies could definitively be excluded as the problem. The overall success rate for treatment was 80 per cent. Further studies on a larger patient sample are needed so that specific problems can be linked to cause and outcome in a meaningful manner.

Measured energy expenditure in pediatric intensive care patients.

Few data are available on energy requirements of mechanically ventilated, critically ill children. We measured the resting energy expenditure in 18 mechanically ventilated patients between ages 2 and 18 years, using indirect calorimetry. All patients had fractional inspired oxygen concentration less than 0.6, no spontaneous respirations, hemodynamic stability, and no fever or active infection, and were receiving 5% dextrose. All subjects were hypermetabolic, since the measured resting energy expenditure divided by the predicted basal energy expenditure from the Harris-Benedict equations was 1.48 +/- 0.09 (mean +/- SEM). The energy requirements calculated using "injury factors" and "activity factors" adapted for adults is 1.62 times basal energy expenditure. The injury factor for the pediatric multiple trauma patients should be 1.25 compared with 1.35 in adults. In these pediatric intensive care patients 33% +/- 8% of the energy is derived from carbohydrates, 53% +/- 8% from fat, and 14% +/- 2% from protein oxidation. In individual critically ill pediatric patients, energy requirements should be estimated by measuring their resting energy expenditure whenever possible and adding 5% for their activity. In the absence of the actual measurement of resting energy expenditure, the recommended energy requirement is 1.5 times basal energy expenditure. In this acute phase of injury, the daily nitrogen requirement is 250 mg per kilogram of body weight.

Hydrostatic pressure-induced colon trauma from a pool whip.

Hydrostatic pressure-induced colon injury is a rare occurrence in the pediatric population. We present a case of massive hydroperitoneum following a pool whip-induced injury. Although tension pneumoperitoneum or hydroperitoneum is rare, prompt recognition and surgical intervention are essential.

Gastrografin aspiration in a 3 3/4-year-old girl.

A case of Gastrografin aspiration in a 3 3/4-year-old child admitted for multiple trauma is described.

Lack of evidence that formula-derived creatinine clearance approximates glomerular filtration rate in pediatric intensive care population.

During the four-year period from January 1980 to April 1984, 56 patients were admitted to the Pediatric Intensive Care Unit (PICU) whose care required timed urine collections using indwelling urinary catheters. The glomerular filtration rate derived from the clearance of endogenous creatinine with accurate timed urine volume is compared to that derived from the formula, 0.55 body length (cm)/plasma creatinine (mg/dl). There is a significant difference in the results between the two methods, p less than 0.0001. The largest divergence arises in those with creatinine clearance of less than 40 ml/min per 1.73 sq.m. In this subgroup, the formula derived glomerular filtration rates consistently overestimate the renal function and create a misleading assurance of minimal renal impairment. Therefore, our findings suggest that the latter formula is not applicable to PICU patients for consideration of fluid and electrolyte balance, administration of nephrotoxic drugs or criteria for dialysis.

Postictal pulmonary edema in children.

Pulmonary edema complicating generalized tonic-clonic seizures has rarely been reported in children, although it has been well documented in adults. We report two patients, aged 8 and 9 years, who developed clinical and radiographic evidence of the condition. Fever, leukocytosis, and arterial hypoxemia are seen in the absence of cardiac dysfunction or infection. Rapid and complete recovery is to be expected if supportive therapy is instituted. Since these patients had no underlying cardiac pathology, control of the seizures will prevent further episodes.