Classification of middle- and long-distance runners based upon their performance.

The scientific literature lacks consensus on classification of middle- and long-distance runners. This creates situations where the sample studied may not represent the target population and could produce misleading conclusions. Thus, we present an approach for a data-driven classification of middle- and long-distance runners according to their competition results. The best annual results of middle- and long-distance track runners participating at major (Olympics, World and European Championships) and national championships (Denmark, Sweden, Finland, Norway) were gathered for the 2012-2018 period. Overall, 1920 men's and 1808 women's performance results were gathered. The results were grouped accordingly. Quadratic discriminant analysis was applied to define the limits between the groups. Three basic categories could be proposed for classification: world class, international and national. Classification provides a realistic overview of performance standards and the number of athletes for different categories in middle- and long-distance track running in real-world settings. The performance-based classification provides data-driven and unified criteria for reporting standards on athletes' proficiency levels. It allows for more consistent reporting practices on the target population in research. In addition to scientific research, the classification could also be employed for a variety of practical purposes.

Altered relationship between R-R interval and R-R interval variability in endurance athletes with overtraining syndrome.

Autonomic dysfunction decreases within-subject correlation between R-R interval length (RRi) and vagally mediated RRi variability in cardiac disease. We tested the hypothesis that overtraining syndrome (OTS) may also weaken this relationship. Nine OTS and 10 control endurance athletes underwent 24-h electrocardiogram monitoring, which was repeated in eight OTS and nine control athletes after 6 months, when two OTS athletes still had symptoms of OTS. The power of high-frequency (HF) oscillations of RRi was analyzed in 5-min epochs over the whole recording. Quadratic regression was performed between 5-min values of RRi and log-transformed (ln) HF to obtain R(2) for each recording. The relationship between RRi and HFln was higher in the OTS athletes than controls [R(2): 0.87 (90% confidence interval, CI: 0.84-0.89) vs 0.78 (90% CI: 0.72-0.84); P = 0.034; effect size = 1.22]. Large decrease in R(2) was observed in six recovered OTS athletes after 6 months follow-up [ΔR(2): -0.12 (90% CI: -0.25-0.01); P = 0.11; effect size = 1.44] with no changes in the controls. Mean values of RRi and its variability did not differ between the groups. The within-subject correlation between RRi and vagally mediated RRi variability was stronger in endurance athletes with OTS compared with controls. The present findings may improve the detection of OTS and recovery from OTS in endurance athletes.

Plasma irisin and its associations with oxidative stress in athletes suffering from overtraining syndrome.

Irisin is a novel exercise-induced myokine that may be involved in regulating energy metabolism. We determined whether overtraining syndrome (OTS) and its biochemical markers are associated with plasma irisin levels in athletes. Seven severely overtrained athletes (OA) and 10 healthy control athletes (CA) were recruited and examined at the time of diagnosis (baseline) and after 6- and 12-months follow-up. Training volume and intensity were initially restricted but progressively increased in OA as OTS symptoms alleviated; CA continued their normal training routine. A maximal cycle ergometer test was performed with irisin analyzed before and after the test. Before the exercise test, irisin levels tended to be lower in OA than in CA at baseline (154.5 ± 28.5 vs. 171.7 ± 58.7 ng/mL). In both groups, at rest irisin levels changed only marginally during follow-up and were not affected by maximal exercise, nor were they associated with physical performance or body fat percentage. Irisin concentration at rest correlated positively with an oxidative stress marker, malondialdehyde (MDA) and negatively with an antioxidant protection marker, oxygen radical absorbance capacity (ORAC) in response to the exercise test in OA at baseline. Our findings help to clarify the possible contribution of irisin and its association with oxidative stress in the pathophysiology of OTS.

Aerobic fitness, energy balance, and body mass index are associated with training load assessed by activity energy expenditure.

The present study examined whether activity energy expenditure related to body mass (AEE/kg) is associated with maximal aerobic fitness (VO(2max)), energy balance, and body mass index (BMI) during the 2 hardest weeks of the military basic training season (BT). An additional purpose was to study the accuracy of the pre-filled food diary energy intake. Energy expenditure (EE) with doubly labeled water, energy intake (EI), energy balance, and mis-recording was measured from 24 male conscripts with varying VO(2max). AEE/kg was calculated as (EE x 0.9-measured basal metabolic rate)/body mass. The reported EI was lower (P<0.001) than EE (15.48 MJ/day) and mis-recording of the pre-filled diary was -20%. The negative energy balance (-6+/-26%) was non-significant; however, the variation was high. The subjects with a low VO(2max), a high BMI, and a negative energy balance were vulnerable to low AEE/kg. However, in the multivariate regression analysis only BMI remained in the model, explaining 33% of the variation in AEE/kg. During wintertime BT, AEE/kg is affected by energy balance, VO(2max), and BMI. From these three factors, overweight limits high-level training the most. Furthermore, an optimal energy balance facilitates physical performance and enables high training loads to be sustained during the BT season.

Role of genetic and environmental influences on heart rate variability in middle-aged men.

Our aim was to estimate causal relationships of genetic factors and different specific environmental factors in determination of the level of cardiac autonomic modulation, i.e., heart rate variability (HRV), in healthy male twins and male twins with chronic diseases. The subjects were 208 monozygotic (MZ, 104 healthy) and 296 dizygotic (DZ, 173 healthy) male twins. A structured interview was used to obtain data on lifetime exposures of occupational loading, regularly performed leisure-time sport activities, coffee consumption, smoking history, and chronic diseases from 12 yr of age through the present. A 5-min ECG at supine rest was recorded for the HRV analyses. In univariate statistical analyses based on genetic models with additive genetic, dominance genetic, and unique environmental effects, genetic effects accounted for 31-57% of HRV variance. In multivariate statistical analysis, body mass index, percent body fat, coffee consumption, smoking, medication, and chronic diseases were associated with different HRV variables, accounting for 1-11% of their variance. Occupational physical loading and leisure-time sport activities did not account for variation in any HRV variable. However, in the subgroup analysis of healthy and diseased twins, occupational loading explained 4% of the variability in heart periods. Otherwise, the interaction between health status and genetic effects was significant for only two HRV variables. In conclusion, genetic factors accounted for a major portion of the interindividual differences in HRV, with no remarkable effect of health status. No single behavioral determinant appeared to have a major influence on HRV. The effects of medication and diseases may mask the minimal effect of occupational loading on HRV.

Brain serotonin reuptake did not change during one year in overtrained athletes.

Brain 5-HT neurotransmission has been described to be down-regulated in depressed people, and also suspected to be changed in overtraining state, the consequence of long-term physical overloading and stress in athletes. We studied brain serotonin (5-HT) transporter binding i.e., 5-HT reuptake with the specific radioligand (123-I-labelled 2beta-carbomethoxy-3beta[4-iodopenyl]-nortropane, Nor-beta-CIT), and with single photon emission tomography (SPET) in severely overtrained athletes and their controls at the baseline and after a one-year recovery period. Twelve overtrained (6 women and 6 men, mean age 27 yrs, range 16 - 39 yrs) and 11 healthy (6 women, 5 men, 26 yrs, 20 - 39 yrs) athletes were examined. Overtrained athletes 1) had suffered from an unexplained decrement in physical performance and fatigue for several weeks to many months and continued to have the same symptoms even after a recovery time of weeks to months, 2) had been examined to be otherwise healthy, and 3) had a suitable training history for overtraining. Nor-beta-CIT SPET was acquired 5 min, and 3, 6, and 24 h after the injection of the radioligand. 5-HT reuptake in ml/ml in midbrain (raphe nuclei) was calculated as (midbrain - cerebellum)/cerebellum. According to two-way analysis of variance, no changes inside the groups or group differences in 5-HT reuptake were found. Male athletes had significantly higher 5-HT reuptake than female athletes at the baseline (p = 0.034). The overtrained athletes were moderately depressed, while their scores in standardized Hamilton and Montgomery-Asberg Depression Rating Scales were 16 +/- 2 (mean +/- SEM, range 8 - 29) and 17 +/- 2 (7 - 28), respectively. In the CA, the scores were 6 +/- 1 (range 2 - 18) and 6 +/- 2 (1 - 19), respectively. 5-HT reuptake did not correlate with the depression scores either in the whole group or in the OA. The finding of the present study does not support the idea of long-term changes in 5-HT neurotransmission in overtraining state, in this case serotonin reuptake in midbrain, the regulating area of brain serotonin neurotransmission. Furthermore, depression of overtrained athletes may be its own variant having no correlation with 5-HT reuptake in midbrain. Sex may have effect on chronic stress response at the brain level in athletes, which may be a confusing factor in the overtraining studies, and has to be taken into consideration in the future.

Abnormal serotonin reuptake in an overtrained, insomnic and depressed team athlete.

The purpose of this report is to study serotonin reuptake of the brain in a severely overtrained athlete by using single-photon emission computed tomography (SPECT). A 26-year-old team athlete increased his training volume (by 200 %) and intensity markedly in a new high-level team. After two months, he started to feel continuous fatigue. He had tinnitus in his left ear, he felt disturbing palpitation and had pollacisuria. After four months, he started to suffer from insomnia. He still continued to play for another three months, after which he was unable to play. He could only sleep for 3 to 4 hours per night. Only minor abnormalities could be found in extensive physical and laboratory examinations. The athlete had a severe overtraining state. In the brain SPECT scans, using the specific radioligand for serotonin transporter imaging ( (123)I labelled 2beta-carbomethoxy-3beta-[4-iodophenyl]-nortropane), low activity areas were detected in the midbrain, anterior gingulus, and left frontal and temporo-occipital lobes. In a psychiatric examination, the patient was found to have signs of major depression, which he hardly recognized himself. We conclude, that that the severe overtraining state could have been related to decreased serotonin reuptake in the brain and signs of major depression.