Exercise-induced effects on growth hormone levels are associated with ghrelin changes only in presence of prolonged exercise bouts in male athletes

AIM: The aim of this study was to evaluate growth hormone (GH) and ghrelin levels in response to physical exercise in athletes. METHODS: Two different exercise workloads were administered in two different groups of athletes. Group A athletes (19 males, 18 females; mean age +/- standard deviation: 25+/-6.7 years), performing a 60-90 min training session at approximately 80% of VO2max, were sampled for GH and ghrelin determinations before and immediately at the end of a training session on-the-field. Group B athletes (4 males; mean age: 28.2+/-7.2 years) performed two consecutive 30-min cycling sessions at 80% of individual VO2max at different time intervals between bouts (2 and 6 h) in two different days. GH and ghrelin concentrations were determined in blood samples collected at 15-min intervals during exercise and following 1 h of recovery. RESULTS: In group A athletes, GH levels increased after the training session (P<0.0001), with no differences between males and females. In male athletes, ghrelin levels significantly decreased after the training session (from 1 506.4+/-859 to 1 254.8+/-661.7 pg/mL, P<0.05), while no significant changes were found in females. No correlations were observed between GH and ghrelin levels at rest and after training. In group B athletes, GH levels significantly increased after the first exercise bouts (peak: 26.8+/-11.2 and 17.3+/-3.5 ng/mL, respectively), while the pattern of GH response was different after the second bout of exercise performed at 2-h or 6-h interval. In fact, peak GH concentration in response to the second bout (4.3+/-1.6 ng/mL) was lower (P<0.01) than that of the first bout when the interval elapsed was only 2 h, while a recovery of GH responsiveness was evident after the 6-h interval between the two exercise bouts (11.9+/-3.3 ng/mL). As far as ghrelin levels are concerned, no significant changes were observed during and after the two exercise bouts performed at the different time intervals. CONCLUSION: GH responses to prolonged exercise bouts (60-90 min) are associated with changes in ghrelin levels only in male athletes, while repeated exercise bouts of lower duration (30 min), capable to determine marked GH responses, are divorced from changes in ghrelin concentrations.     

The response of serum growth hormone and prolactin to training in weight-maintaining healthy males

Resting levels of serum growth hormone (GH) and prolactin (PRL) were measured pretraining, 3 weeks and 10 weeks posttraining in seven college age males. The exercise consisted of thrice weekly sessions at 70% VO2max for 20 minutes plus warmup and cool down. Body weight remained constant during the ten week training period. However, body fat decreased significantly. Resting daytime levels of GH decreased significantly with training while resting PRL levels were unchanged. The hormone responses suggest attenuation of resting GH levels with training and may relate to changes in body fat.     

Effect of water-training in the maintenance of cardiorespiratory endurance of athletes.

The effectiveness of water-training in maintaining cardiorespiratory endurance was investigated in 16 cross country athletes, 18--24 years. Following a competitive season, subjects were stress-tested (T1) and divided into three equated groups based on VO2 max. Group I (n=5) continued training as it had during the competition season. Group II (n=5) underwent an experimental period of water-training, and Group III (n=6) let their training lapse. Subjects in the water-training group exercised in deep water for 40 minutes, 6 days/week for 3 weeks, supported by a flotation device which permitted them to engage in a running type activity, resembling their natural running form. All subjects were retested after 3 weeks (T2). A non-significant F ratio from an analysis of variance at T1 confirmed the equality of the three groups in terms of VO2 max. Analysis of covariance at T2 using T1 VO2 max values as covariates revealed a significant (p less than .05) F ratio reflecting a significant (p less than .05) difference between the regular training group and the group which let its training lapse. The water-training group did not differ significantly from the regular training group indicating that the water-training programme prevented a significant decline in VO2 max.     

Effect of training on anaerobic threshold, maximal aerobic power and anaerobic performance of preadolescent boys

To evaluate the effect of a 9-week interval training program on aerobic capacity, anaerobic capacity, and indices of anaerobic threshold of preadolescent boys, 28 10.2- to 11.6-year-old boys were tested. The test included laboratory evaluation of anaerobic capacity (Wingate anaerobic test) and evaluation of VO2 max and anaerobic threshold indices from a graded exercise test and measurement of blood lactate. The tests also included a 1200-m run to investigate the relationship of laboratory fitness indices, VO2 max, anaerobic threshold indices, and indices of anaerobic capacity to the performance of the run. It was found that in 10- to 11-year-old boys, a 9-week interval training increased the indices of anaerobic capacity: mean power by 10% and peak power by 14%. No change was found in percent fatigue. The training also increased VO2 max by 7% in absolute terms and by 8%/kg body weight. A significant increase was also found in the running velocity at the anaerobic threshold (running velocity at inflection point of lactate accumulation curve), but in relative terms (percent of VO2 max), the anaerobic threshold decreased by approximately 4.4%. It is concluded that proper training may improve maximal aerobic power and anaerobic capacity of preadolescent boys. It is also concluded that anaerobic threshold measures are less sensitive to the training regimen than VO2 max and that the 1200-m running performance is strongly associated with both aerobic and anaerobic capacities and less with the anaerobic threshold, which in preadolescent boys seems to be higher than in adults.     

Longitudinal changes in distance-running performance of young males

Longitudinal studies of adolescent males have shown that absolute maximal aerobic power (VO2max) and distance-running performance improve with age, while VO2max expressed relative to body mass remains stable. These earlier studies used subjects that were engaged in distance-run training; therefore, it was not possible to assess the relative importance of growth and/or run training to improved performance. The purpose of this study, therefore, was to quantify longitudinal changes in VO2max, running economy (RE), and distance-running performance in non-run-trained young males. Six subjects were tested at mean ages of 9.9 (T1) and 16.8 years (T2). Statistical tests of mean values revealed that over the 7-year period, relative VO2max remained unchanged (T1, 48.9 ml.kg-1.min-1; T2, 47.8 ml.kg-1.min-1) and RE improved (T1, 234.2; T2, 202.8 ml.kg-1.km-1), 9-min run distance increased (T1, 1637 m; T2, 2115 m), and the estimated percent of VO2max incurred during the 9-min run increased from 85.8% (T1) to 99.5% (T2). It was concluded that the improvement in distance-running performance observed in adolescent boys was not dependent upon run training. In view of the fact that maximal aerobic power remained stable, this change appears to be attributable to better running economy and an ability in runs of a fixed duration to perform at a higher relative work load.     

The effect of pure aerobic training on aerobic and anaerobic capacity.

Twenty men (Group I) and twenty-seven men (group II) took part in a 3-week training course. The training was aerobic and consisted of marching and hiking. The intensity of the training regimen in Group II was greater than for Group I. The maximal oxygen uptake (VO2 max) increased significantly in both groups, more in Group II than in Group I, though no significant change was found in anaerobic capacity. It can be concluded that aerobic training cannot induce improvement in anaerobic capacity.     

Muscle structure and aerobic performance capacity in recruit training school

The aerobic performance capacity (VO2 max) and muscle ultrastructural composition was analyzed in 18 subjects undergoing basic training in the Swiss army. Three groups were selected based on their sports activity. Group S contained subjects that had a previous systematic background in sports activities and trained regularly at least three times per week. A second group consisted of subjects that had no previous training and were subjected to an additional, individually adjusted endurance exercise (three times per week) for the first 8 weeks of their service period (group T). The control group (C) had no previous training and followed only the regular military duties. VO2 max was found to be significantly higher in group S at the beginning of the military service. However, VO2 max did not change significantly during the service period in any of the groups, Muscle mitochondria showed a significant change (+19%) only in group T. Heart rate recordings indicated that despite "strenuous" military activity, heart rates rarely reached levels sufficient for an increase in aerobic performance capacity.     

Inverse Relationship between V˙O2max and Gross Efficiency

The aim of this study was to identify if an inverse relationship exists between Gross Efficiency (GE) and V˙O2max in trained cyclists. In Experiment 1, 14 trained cyclist's GE and V˙O2max were recorded at 5 different phases of a cycling 'self-coached' season using an incremental laboratory test. In Experiment 2, 29 trained cyclists undertook 12 weeks of training in one of 2 randomly allocated groups (A and B). Over the first 6 weeks Group A was prescribed specific high-intensity training sessions, whilst Group B were restricted in the amount of intensive work they could conduct. In the second 6-week period, both groups were allowed to conduct high intensity training. Results of both experiments in this study demonstrate training related increases in GE, but not V˙O2max. A significant inverse within-subject correlation was evident in experiment 1 between GE and V˙O2max across the training season (r=?-?0.32; P<0.05). In experiment 2, a significant inverse within-subject correlation was found between changes in GE and V˙O2max in Group A over the first 6 weeks of training (r=?-?0.78; P<0.01). Resultantly, a training related inverse relationship between GE and V˙O2max is evident in these groups of trained cyclists.     

Differences in the cellular and humoral immune system between middle-aged men with different intensity and duration of physically training

AIM: The effects of acute exercise on immune system and serum magnesium and iron have been investigated in recent years. However, data related to the comparisons of long-term physical training with different intensity and duration are limited. METHODS: The association between long-term physical training and cellular (lymphocyte phenotyping) and humoral immune parameters (serum immunoglobulins) and serum magnesium and iron values in the middle-aged men was investigated. Eleven male master athletes (MA) performing high intensity and long duration training, 11 male recreational athletes (RA) performing moderate intensity and duration training (>10 years) participated. Eleven male sedentary individuals were enrolled as control group (CG). RESULTS: The percentages of total CD3+ T cells, CD4+ T helper, CD8+ T suppressor/cytotoxic, CD19+ B cells, natural killer cells, HLA-DR+ active T cells and CD4/CD8 ratios did not show any significant difference among 3 groups. In MA, VO2max values showed a significant negative correlation with CD4+ T helper cells. There were no significant differences among MA, RA and CG in terms of IgG, IgA, and IgM concentrations. There was a significant correlation between VO2max and IgG in RA. Iron, iron binding capacity and ferritin were found similar in all groups, but serum magnesium level in MA was significantly lower than RA and CG. CONCLUSION: No exact data to support immunosuppression or immunostimulation could be obtained except a significant negative correlation between CD4+ T helper cells and VO2max values in MA and a positive correlation between serum IgG and VO2max ivalues in RA. These findings may be the indirect markers of cellular immune system suppression by intensive exercises and stimulation of IgG production by moderate exercises.     

The effect of exercise training on salivary immunoglobulin A and cortisol responses to maximal exercise.

The salivary immunoglobulin A (s-IgA) and cortisol responses to maximal exercise were examined in 24 adult males (X +/- SD; 22.1 +/- 3.0 yrs) before and after 10 weeks of run training. The subjects performed an incremental treadmill test to exhaustion and were randomly assigned to one of three groups: control (CON; n = 5), low intensity training (LO; n = 8), or high intensity training (HI; n = 11). Following the ten weeks of training, the subjects performed a second maximal treadmill test. Saliva samples were collected before, as well as immediately and 1 hr following each of the maximal treadmill tests and were analyzed for s-IgA and salivary cortisol. Maximal oxygen consumption (VO2max) increased significantly (p < 0.05) in the LO and HI groups but remained unchanged in the CON group. The s-IgA levels decreased significantly (p < 0.05) immediately post-exercise but returned to pre-exercise levels by one hour recovery. In addition, s-IgA and cortisol levels were not significantly (p > 0.05) correlated at any of the sampling times. These findings indicated that the s-IgA response to maximal exercise was unaffected by moderate (70% of VO2 max) to heavy (86% of VO2max) training (designed to develop cardiorespiratory fitness in healthy non-athletic adults) and independent of salivary cortisol.     

Mechanical efficiency during cycling in prepubertal and adult males

Previous studies have indicated that values for mechanical efficiency during cycle exercise in prepubertal subjects are similar to those in adults. Few studies have directly compared these groups, however, and earlier reports did not consider the importance of assessing efficiency at similar relative exercise intensities. Nineteen prepubertal boys and 21 college men underwent cycle exercise testing for determination of delta efficiency (the energy required to increase workload), related to both absolute work load and relative work intensity (percent VO2max). No significant differences in either of these measures were observed between the two groups. Mean delta efficiency between workloads of similar relative intensity was 23.2% for the prepubertal subjects and 22.5% for the adults (p greater than .05). Between equal absolute workloads the values were 23.2 and 26.5%, respectively (p greater than .05). These findings support earlier contentions that the efficiency of muscular contraction during exercise is comparable in pre- and post-pubertal subjects.     

Effects of high intensity intermittent training on peak VO(2) in prepubertal children

This study was designed to examine peak VO(2) responses of prepubescent children following a 7-week aerobic training. Twenty-three boys and thirty girls (9.7 +/- 0.8 years) were divided into a high intensity experimental group (HIEG: 20 girls and 13 boys) and a control group (CG: 10 girls and 10 boys). A graded 20-m shuttle run with measurement of gas exchange values was performed prior to and after the 7-week training program. The test consisted of a 3-min run at 7 km x h(-1) to determine energy cost of running, immediately followed by a 20-meter shuttle run test. HIEG had two 30 min-sessions of short intermittent aerobic training per week at velocities ranging from 100 up to 130 % of the maximal aerobic speed. For HIEG, absolute peak VO(2)(9.1 %) and relative to body mass peak VO(2)(8.2 %) increased significantly (p < 0.001); it was unchanged in the CG. Similarly, maximal shuttle run improved significantly in HIEG (5.1 %, p < 0.001). In contrast, there was no significant change for CG. For both groups energy cost of running remained unchanged. These findings show that prepubescent children could significantly increase their peak VO(2) and maximal shuttle velocity with high intensity short intermittent aerobic exercises.     

Effect of continuous slow-speed running for 12 weeks on 10-14-year-old Indian boys.

Endurance training was conducted on a group of 41 East Indian boys aged 10-14 years and was compared with 25 untrained boys of the same age. A continuous slow-running method was adopted for 12 weeks. The intensity of the training was 80-85% of maximum heart rate and frequency was 3 days per week. The boys were trained for a 1500-m event and therefore they covered three to five times their racing distance. For psychological reasons the training was carried out in a playground. The investigations included different physical and motor fitness tests: measurement of flexibility, agility, speed, leg muscle strength etc. Their performance times were also recorded before and after training. From statistical analysis we concluded that this particular type of training programme did not produce any detrimental effects on 10-14-year-old boys. On the other hand, this type of training did have some influence on improving physiological parameters in this age group of boys when compared with untrained boys of the same age.     

Cross-sectional and longitudinal evaluations of an endurance training program.

A comparison of the cardiorespiratory responses obtained using both a longitudinal and cross-sectional evaluation of an endurance training program was made in two groups of 60 young male military personnel. Both groups were initially tested (T1) and then retested 6 months later (T2). At T1, Group I was a sample of personnel not participating in a training program while Group II had undergone a 5-month endurance program (2-4 mile run/day). At T2, Groups I and II had been participating in the program for 6 and 11 months, respectively. Testing consisted of sub-maximal and maximal determinations of VO2, VE and heart rate (HR) using an interrupted treadmill test. VO2 max was 11% greater in Group II compared to Group I at T1 and increased 10% in Group I at T2. Similar results were also seen for HR submax, HR max and VE max. These results show that similar values indicative of an improved level of cardiorespiratory fitness can be obtained using either a cross-sectional or longitudinal design when relatively homogeneous groups are studied.     

运动性免疫抑制大鼠肝、脾糖皮质激素受体表达变化探讨

目的:研究运动性免疫抑制时糖皮质激素受体(glucocorticoid receptor,GR)mRNA和蛋白表达变化,探讨GR在运动性免疫抑制发生中的作用。方法:40只SD大鼠随机分为安静对照组(C组,n=10)、中强度运动组(M组,n=10)和过度疲劳运动组(O组,n=20)。后两组分别进行不同强度的8周递增负荷训练,每周训练6天。每周称量大鼠体重。8周训练结束后采血,检测Hb、血睾酮、皮质酮水平,外周血T细胞亚群(CD3+、CD4+、CD8+)、自然杀伤细胞(NK细胞)数量和辅助性T淋巴细胞1、2(Th1、Th2)特异性细胞因子IFN-γ、IL-4水平。之后断头处死动物,采用real time PCR和Western blot方法分别检测大鼠肝、脾GR mRNA和蛋白水平。结果:(1)与安静对照组和中强度运动组相比,过度疲劳运动组大鼠体重从第4周起明显下降(维持至实验结束),Hb、血浆睾酮水平、睾酮/皮质酮比值均显著下降,血浆皮质酮水平显著升高,表明过度疲劳训练组大鼠已发生过度疲劳。(2)8周训练后,与安静对照组和中强度运动组相比,过度疲劳运动组大鼠CD3+细胞、NK细胞数量显著减少、IFN-γ/IL-4比值显著下降,Th1/Th2失衡,但CD4+/CD8+比值无显著性差异,表明运动性免疫抑制大鼠模型建立成功。(3)与安静对照组和中强度运动组相比,8周训练后,过度疲劳运动组大鼠肝、脾GR mRNA和蛋白水平均显著下降;与安静对照组相比,中强度运动组大鼠肝、脾GR mRNA和蛋白水平均无显著变化。(4)相关性分析显示,肝、脾GR mRNA和蛋白水平与血浆GC的相关系数分别为-0.752、-0.613、-0.144和-0.397,均P<0.05。结论:(1)运动性免疫抑制大鼠肝、脾GR mRNA和蛋白表达水平较安静对照组和中强度运动组显著降低。(2)运动性免疫抑制大鼠肝、脾GR mRNA减少和脾GR蛋白水平下降可能与血浆GC升高有关。     

The effect of short-term strength training on human skeletal muscle: the importance of physiologically elevated hormone levels

The effect of strength training and endogenously elevated hormone levels (plasma testosterone, growth hormone (GH) and cortisol) was studied in 16 young untrained males, divided into an arm only training group, A, and a leg plus arm training group, LA, in order to increase circulating levels of anabolic hormones. Both groups performed the same one-sided arm training for 9 weeks, twice a week. Group A trained only one arm (AT), the contralateral arm serving as control (AC), whereas group LA additionally trained their legs following the training of the one arm (LAT), with the contralateral arm serving as control (LAC). In spite of the attempt to match the two groups, the initial isometric arm strength was 20-25% lower for group LA compared to group A (significant for the arm to be trained). Isometric strength increased significantly in LAT and LAC by 37% and 10%, respectively, while the 9% and 2% increases in AT and AC, respectively, remained insignificant. Isokinetic strength increased at one out of three velocities tested for the trained arm relative to the untrained arm in both group A and group LA (P<0.05). Functional strength increased significantly by 20% in LAT, 18% in LAC, 19% in AT, and 17% in AC. Hormonal responses were monitored during the first and last training sessions. Resting hormone levels remained unchanged for both groups. However, during the first training session plasma testosterone as well as plasma cortisol increased significantly in group LA but not in group A. Plasma GH rose in all exercise tests, except during the last test in group LA, but was significantly higher in group LA than in group A in the first training session. In conclusion, a larger relative increase in isometric strength was found in the group having the highest hormonal response. However, due to the initial difference in isometric strength caution must be taken with the interpretation of this finding, which may only indicate a possible link between anabolic hormones and muscle strength with training.     

Effect of aerobic training and detraining on left ventricular dimensions and diastolic function in prepubertal boys and girls

PURPOSE: The purpose of this study was to determine the effect of an aerobic training program on the left ventricular (LV) cardiac morphology and function of prepubertal children. METHODS: Twenty-nine 10-11 year old boys and girls (TG) participated in a 13-week running program (3 x 1 h/week, intensity: > 80% HRmax), 26, of the same age, served as a control group (CG). M-mode, 2-dimensional and pulsed-wave Doppler analyses were performed, during resting conditions, before and after the training period (T) as well as, for TG only, after 2 months of detraining (D). RESULTS: LV internal chamber dimension increased (+ 4.6 %, p < 0.01) while wall thicknesses concomitantly decreased (-10.7%, p < 0.05) as a result of T. All cardiac morphological parameters returned to pretraining values after D. Doppler-derived measurements of LV diastolic filling performance were also significantly altered by Tand D. A significant enhancement in the early diastolic passive LV filling with a concomitant reduction in the late diastolic active LV filling were in fact obtained after T. The training-induced bradycardia (-7 beats x min(-1), p < 0.01) was probably responsible for the changes in the late characteristics of the diastolic active filling. All diastolic filling indexes returned to pretraining values after D. Systolic function indexes were not modified after either T or D. No changes were obtained for the overall LV morphological and functional variables after 13 weeks of normal life for CG. CONCLUSION: These findings indicate that cardiac morphological adaptations can occur in prepubertal children after several months of aerobic training. These alterations differ however, in some areas, to those classically reported in adults following endurance training programs where both an increase in LV size and mass exist. Our data likewise demonstrate that endurance training is able to induce favourable LV diastolic filling modifications, directed principally towards an enhancement in the early rapid filling inflow and a corresponding reduction in the atrial contribution to the total diastolic inflow.     

A comparative study of left ventricular structure and function in elite athletes.

Adaptations to left ventricular (LV) structure and function appear to be dependent on the type, intensity and duration of exercise training. We therefore studied two clearly defined groups of elite athletes, by M-mode and Doppler echocardiography, with a group of inactive individuals as controls. All groups were age matched. Group 1 comprised ten elite endurance athletes with maximal oxygen consumption (VO2 max) of 74.7 +/- 1.43 (mean +/- SEM). Group 2 consisted of ten elite weightlifters with VO2 max 45.3 +/- 2.00. Group 3 comprised of ten inactive individuals with VO2 max 44.5 +/- 2.13. Left ventricular end diastolic dimension was significantly higher in group 1 (5.72 +/- 0.07) than in groups 2 or 3 (5.29 +/- 0.09 and 5.19 +/- 0.09 respectively, p less than 0.001). Left ventricular mass index was significantly higher in groups 1 and 2 (156.4 +/- 5.97 and 138.6 +/- 7.27 respectively) than in group 3 (104.1 +/- 3.16 p less than 0.001). Percentage fractional shortening was used as an index of systolic function and no significant difference was found between groups. Doppler E:A ratio was taken as an index of diastolic function and was found to be significantly elevated in group 1 at rest (3.37 +/- 0.24) compared with 2.38 +/- 0.16 and 1.99 +/- 0.10 in groups 2 and 3 respectively (p less than 0.003). On exercise, the E:A ratio in group 1 was significantly higher than in group 3 (1.95 +/- 0.14 and 1.23 +/- 0.05 respectively p less than 0.001), and tended to be higher than group 2 (1.68 +/- 0.15 p = ns). These data show that both modes of intense training produce left ventricular hypertrophy. Diastolic function is not impaired in the athletes and may be augmented in the endurance athletes.     

Discordance between dipyridamole stress Tc-99m sestamibi SPECT and coronary angiography in patients with Kawasaki disease

BACKGROUND: Kawasaki disease is an acute vasculitis syndrome of unknown etiology that mainly affects the coronary arteries. The purpose of this study was to assess the agreement between dipyridamole stress technetium 99m sestamibi single photon emission computed tomography (SPECT) and coronary angiography in these patients. METHODS AND RESULTS: Forty-one consecutive patients (29 boys and 12 girls) who underwent coronary angiography were studied prospectively. Their ages at onset of the disease ranged from 2 months to 4.8 years (mean +/- SD, 1.9 +/- 1.3 years). Their ages at the time of the study ranged from 8 months to 15.3 years (6.2 +/- 4.4 years). The duration between symptom onset and the study ranged from 2 months to 12 years (4.3 +/- 4.0 years). All patients underwent dipyridamole stress Tc-99m sestamibi SPECT within 1 month of their angiographic studies. They were divided into 3 groups according to coronary angiography findings. Group A consisted of 2 patients (1 boy and 1 girl, aged 10.3 and 1.9 years, respectively) with coronary stenoses who also had aneurysms. Group B consisted of 10 patients (8 boys and 2 girls, aged 0.7-15.3 years [mean, 3.8 years]) with coronary aneurysms. Group C consisted of 29 patients (20 boys and 9 girls, aged 1.2-13.8 years [mean, 7 years]) with normal coronary angiograms. Two patients in group A (100%), 3 of 10 patients in group B (30%), and 19 of 29 patients in group C (65.5%) had myocardial perfusion defects. There was poor agreement between Tc-99m sestamibi SPECT and coronary angiography for detecting coronary stenoses (kappa = 0.07; P =.222) and aneurysms (kappa = -0.184; P =.158). CONCLUSION: Significant discordance exists between Tc-99m sestamibi SPECT and coronary angiography in patients with Kawasaki disease.     

Tracking of physical activity and aerobic power from childhood through adolescence

PURPOSE: To evaluate the tracking of physical activity levels (PA) and aerobic power (VO2max) in African-American (AA) and Caucasian (CA) youth as they age from 8 to 16 yr. METHODS: Subjects were 529 girls and 535 boys for whom data were obtained at least three times over 7 yr and a subset of 387 girls and 404 boys who participated in all years. PA levels were obtained from a survey. VO2max was predicted from a cycle ergometer test. RESULTS: Spearman correlation for VO2max for years 1-7 for AA boys and girls were similar (rho approximately 0.53). Year 1-7 correlations for VO2max for the CA boys and girls were similar (rho approximately 0.50-0.53). The year 2-7 correlations for PA were similar for the AA and CA girls but higher for the AA than the CA boys. The kappa (kappa) statistics for VO2max indicated substantial year-to-year agreement on categorization (high, moderate, and low), with AA girls having the highest agreement and AA boys the lowest. The kappa statistic for high, moderate, and low PA groupings in girls of either ethnicity was quite low, whereas the kappa statistics for the boys were somewhat better. The general estimating equation (GEE) stability coefficients for tracking of VO2max were similar between the sexes and ethnicities (P<0.0001). The GEE stability coefficient for PA was better for the boys than girls and slightly better for the AA than CA. CONCLUSION: Although aerobic power and physical activity levels decline from childhood through adolescence, aerobic power tracks better than physical activity levels. Because tracking within the cohort is only moderate, change is possible if we intervene early in these youth.