摘要:

FREDERICKSON, LUCINDA A., JACQUELINE L. PUHL, and WILLIAM S. RUNYAN. Effects of training on indices of iron status of young female cross-country runners.Med. Set. Sports Exerc., Vol. 15, No. 4, pp. 271–276, 1983. Hematological status and selected indices of iron status were assessed in a group of eight high-school female cross-country runners at weeks 0, 1, 2, 4, and 8 of the competitive season and at 1, 5, and 11 wk after the season. Over the season, a training effect occurred, as was shown by a significant decrease (12.8%) in step-test heart rate and a significant increase (7.0%) in &OV0312;O2max(ml·min-1kg-1). The runners experienced “sports anemia” in that their hemoglobin (Hb) concentration and packed red blood cell volume (FCV) declined significantly during the first week of training (8.8 and 8.3%, respectively), whereas changes did not occur in a comparison group of 11 nonrunners who were followed for the first 3 wk of the season. Between weeks 1 and 8 of the season, the runners' Hb and PCV values gradually returned toward preseason values while their serum iron (SeFe) and percent transferrin saturation (% Sat) showed steady, but nonsignificant, declines, and their total iron-binding capacity (TIBC) rose by 9.4% and continued to rise through the first week after the season. Concomitantly, the runners' free erythrocyte porphyrin (FEP) concentrations rose by 15%. By the end of the detraining period, all indices of iron status had returned to initial values except for TIBC, which still was significantly higher than preseason values. With the exception of TIBC, no significant changes occurred in the iron-status indices of the comparison group during the 2 wk they were followed. The results suggest that in young women recovery from sports anemia may impose a demand on body iron reserves and that it would be prudent to assess iron status as well as hematological status in such women before and during aerobic training.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

WILKES, D., N. GLEDHILL, and R. SMYTH. Effect of acute induced metabolic alkalosis on 800-m racing time.Med. Set. Sports Exerc., Vol. 15, No. 4, pp. 277–280, 1983. Six trained middle-distance runners were studied under alkalotic (NaHCOaingestion), placebo (CaCO3ingestion), and control conditions to determine the effect of an acute induced metabolic alkalosis on time to run an 800-m race. Pre-exercise, following NaHCO3ingestion, pH and standard [HCO3-] were significantly higher. In the alkalotic condition, subjects ran faster (2.9 s) and the corresponding post-exercise values for blood [lactate] and extracellular H+were higher than in the control and placebo conditions, suggesting an increased anaerobic energy contribution. These results support the speculation that the increase in extracellular buffering following NaHCO3ingestion facilitated H+efflux from the cells of working muscle, thereby delaying the decrease in intracellular pH and postponing fatigue. It is concluded that the ingestion of NaHCO3by trained middle-distance runners prior to an 800-m race has an ergogenic benefit.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

DOLATOWSKI, ROSEMARY P., RAY W. SQUIRES, MICHAEL L. POLLOCK, CARL FOSTER, and DONALD H. SCHMIDT. Dysrhythmia detection in myocardial revascularization surgery patients.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 281–286, 1983. In order to document the type and prevalence of significant dysrhythmias in myocardial revascularization surgery patients, cardiac electrical activity was recorded during graded exercise testing, 24-h ambulatory electrocardiography, and electrocardiographic-monitored exercise training. Patients participated in a cardiac rehabilitation program that began approximately 2 wk post-surgery, and attended three monitored exercise sessions per week for 12 consecutive weeks. Graded exercise testing and 24-h ambulatory electrocardiography were administered in the second and eighth weeks of the study (weeks 1 and 6 of the exercise program) post-surgery. Eighty-eight percent of the patients exhibited significant dysrhythmias. A greater number of significant dysrhythmias were found during the second 6 wk of the study in comparison with the first 6 wk. Graded exercise testing was not as effective as ambulatory electrocardiography and monitored exercise training in dysrhythmia detection. Not all dysrhythmias were detected by any one technique, thus a combination of methods may be best for optimal surveillance and detection.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

HAGBERG, JAMES A. and EDWARD F. COYLE. Physiological determinants of endurance performance as studied in competitive racewalkers.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 287–289, 1983. The physiological factors that relate to 20-km performance were studied in eight competitive racewalkers. The racewalking velocity at the blood lactate threshold (LT) during steady-state exercise was highly correlated to racewalking pace (r=0.94) and predicted performance times to within 0.6%, which agrees with previous observations on runners. The two factors that contribute to velocity at LT are O2uptake at LT (&OV0312;o2at LT) and submaximal racewalking economy (measured as the &OV0312;o2at a standard velocity). Oxygen uptake at LT was significantly correlated (r=0.89) to performance in the racewalkers in the present investigation, which agrees with previous observations of runners. Submaximal economy was significantly correlated to performance in the racewalkers (r=0.82). Maximal oxygen uptake measured during racewalking was not significantly correlated (r=0.62) to performance. These data indicate that the velocity at LT correlates closely to performance in racewalkers and that the factor of submaximal economy, which partly determines velocity at LT, is related more to performance ability in racewalking than was previously observed in running.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

DAUB, W.B., H.J. GREEN, M.E. HOUSTON, J.A. THOMSON, I.G. FRASER, and D.A. RANNEY. Specificity of physiologic adaptations resulting from ice-hockey training.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 290–294, 1983. The specificity of the metabolic and cardiorespiratory responses to varied seasonal training programs and to varied testing modalities and protocols were investigated in two groups of college hockey players. Training consisted of either ice hockey (IH) or a combination of ice hockey and prolonged low-intensity cycling (IH-C). Measurement of training-induced adaptations were determined during maximal and submaximal ice skating, and during maximal and submaximal cycling. Ice hockey training caused no change in &OV0312;O2max, maximal heart rate (HRmax), and maximal ventilation (&OV0312;Emax) during maximal ice skating. During submaximal ice skating following IH training, however, reductions (P<0.05) in blood lactate (La), &OV0312;E/&OV0312;O2max, and respiratory exchange ratio (R) were observed. When maximal and submaximal cycling was employed as the test modality, no training-induced alteration was found. The IH-C training program (ice hockey-cycling) resulted in adaptations similar to those observed during submaximal ice skating following the IH training. In addition, a reduction (P<0.05) in heart rate was observed during submaximal cycling exercise. From these findings it appeared that the adaptive response to training may be specific to the type of work used in training, the type of ergometry used to evaluate training, and to specific physiological processes. In addition, these results suggested a dissociation between local and central adaptations.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

CUMMINS, THOMAS D. and L. BRUCE GLADDEN. Responses to submaximal and maximal arm cycling above, at, and below heart level.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 295–298, 1983. It has been suggested previously that arm position may influence the cardiovascular and metabolic adjustments to arm cycling. Therefore, it was the purpose of this study to compare the responses to submaximal and maximal arm cycling with the arms positioned above, at, and below heart level. Five untrained subjects performed arm cycling at each of the three positions at 0, 29.6, 59.0, and 88.0 W. The work rate of 59.0 W was the highest work rate that could be maintained for 10 min by all five subjects. In addition, all subjects performed maximal cycling exercise at all three arm positions in order to determine arm &OV0312;O2peakA restraining harness and synchronous arm cycling were used to isolate the work to the arms as much as possible. Arm &OV0312;O2peakaveraged only 57% of leg &OV0312;O2peakin the present study, due probably to the harness used to reduce the use of accessory muscles during arm exercise, as well as the use of synchronous arm cycling, which reduces trunk rotation. The present study found no significant difference in the responses to either submaximal or maximal arm cycling with the arms positioned above, at, or below heart level. These results suggest that possible changes in arm-muscle blood flow exert only negligible effects when rhythmic dynamic arm exercise is performed in an overhead position.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

ITO, AKIRA, PAAVO V. KOMI, BERTIL SJÖDIN, CARMELO BOSCO, and JAN KARLSSON. Mechanical efficiency of positive work in running at different speeds.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 299–308, 1983. To investigate the possible role of elastic potentiation on mechanical efficiency, three male marathon runners were filmed while running on a treadmill at various steady-state speeds ranging from 7.0–22.0 km·h-1. Kinematic and mechanical energy analyses were performed from the film. Expired air was collected for energy expenditure determination. The analysis disclosed that during contact on the treadmill the knee and ankle joints initially had a phase of negative (flexion) angular velocity, followed by a positive velocity. In the hip joint the stretch-shortening cycle of the extensor muscles occurred primarily during the flight phase. The mean vertical and horizontal forces of the negative and positive phases of the contact period increased linearly with the increase in the running speed. The calculated mechanical efficiency of positive work was high but relatively constant (55.1 ± 12.7%) across all speeds. The absolute contribution of the extra work, which comes from the stored elastic energy to the positive work, increased with running speed; however, its relative value (0.61 ± 0.09 J·min-1·kg-1) remained constant at all measured speeds. It is suggested, therefore, that when the flight phase is included in the mechanical energy calculations, the measured efficiency for the positive work reaches a high but constant value in running at low-to-moderate speeds.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

FUKASHIRO, SENSHI and MITSUMASA MIYASHITA. An estimation of the velocities of three take-off phases in 18-m triple jump.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 309–312, 1983. The purposes of this study were to estimate the take-off velocities necessary to gain a given distance on the triple jump by adopting three hypotheses and to investigate the external force vectors during the jump's supporting phase. The total distance corresponding to the varying combinations of horizontal and vertical velocities at take-offs were calculated based on these hypotheses. The calculated velocities of the body's center of gravity coincided well with the observed total distance, even though the velocities were slightly underestimated. There was a significant correlation between the run-up velocity and the total distance (r=0.91,P< 0.001). From these results, the run-up and take-off velocities and the external force vectors for an 18-m jump were estimated. It might be said that the 18-m jumper must gain great run-up velocity (10.7 m·s-1) and exert forces during each supporting phase which are 3.6–4.4 times the body weight, resulting in a force-vector angle of about 101° at each take-off.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

DAPENA, JESÚS and TERESA BRAFF. Use of separate hand locations to calculate ground reaction force exerted on a vaulting pole.Med Sci. Sports Exerc., Vol. 15, No. 4, pp. 313–318, 1983. A model was developed to permit calculation of the force exerted by the ground on a vaulting pole given the flexibility characteristics of the pole, the grip height of the upper hand, and the coordinates of each of the two hands relative to the base of the pole. The flexural rigidity of the pole was assumed constant throughout the length of the pole and not subject to hysteresis or dynamic loading effects. The model was based on the following rationale: knowing the initial angle of the base of the pole (β0) and the force vector (F1) exerted by the ground on the pole, it was possible to estimate the shape of the pole and the coordinates of the two hands following an iterative procedure. Conversely, it was possible to find a combination of β0, and F1that made the pole fit two specified hand locations.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

FARRELL, PETER A., MICHAEL B. MARON, LYLE H. HAMILTON, MICHAEL G. MAKSUD, and CARL FOSTER. Time course of lung volume changes during prolonged treadmill exercise.Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 319–324, 1983. It has been known since the 1920s that runners completing marathon races have reduced forced vital capacity (FVC) values. To investigate the time course of these lung volume alterations, we measured FVC and residual volume (RV) in 11 runners before, after, and at 30-min intervals during a 2.5-h treadmill run at just under their marathon pace (70% &OV0312;o2max). Mean distance run was 21.5 ± 1.5 (SD) miles in the 2.5-h period. During the first 60 min, both RV and total lung capacity (TLC) decreased by 110 ml, however, this change was not significant (P>0.05). A high correlation (r=0.93) was observed between ARV and ATLC during the first 5 min, while FVC remained unchanged. From 60–90 min, all lung volumes remained constant. From 90–150 min, lung volumes changed in a direction similar to that observed after a marathon, i.e., FVC decreased significantly (5.51 to 5.37 liter between 90 and 150 min,P<0.05), TLC remained unchanged (7.41 vs 7.42 liter,P>0.05), and RV showed a nonsignificant increase from 1.90 to 2.05 liter (P>0.05). The data are consistent with multiple mechanisms playing a role in pulmonary function changes during prolonged exercise. The smaller mean decrease in FVC observed in this study, as compared to that found during a marathon, suggested that the marathon imposes a greater demand on the lungs than did treadmill exercise of the duration and relative intensity used in this study.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID