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.

Overtraining: making a difficult diagnosis and implementing targeted treatment.

Overtraining syndrome is a serious problem marked by decreased performance, increased fatigue, persistent muscle soreness, mood disturbances, and feeling 'burnt out' or 'stale.' The diagnosis of overtraining is usually complicated, there are no exact diagnostic criteria, and physicians must rule out other diseases before the diagnosis can be made. An orthostatic challenge shows promise as a diagnostic tool, but the subjective feelings of the patient remain one of the most reliable early warning signs. Prevention is still the best treatment, and certain subjective and objective parameters can be used by athletes and their trainers to prevent overtraining. Further studies are needed to find a reliable diagnostic test and determine if proposed aids to speed recovery will be effective.

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.

Endurance training, overtraining and baroreflex sensitivity in female athletes.

We examined heavy training-induced changes in baroreflex sensitivity, plasma volume and resting heart rate and blood pressure variability in female endurance athletes. Nine athletes (experimental training group, ETG) increased intense training (70-90% VO2max) volume by 130% and low-intensity training (< 70% Vo2max) volume by 100% during 6-9 weeks, whereas the corresponding increases in six control athletes (CG) were 5% and 10% respectively. Maximal oxygen uptake (VO2max) in the ETG and CG did not change, but in five ETG athletes VO2max decreased from 53.0 +/- 2.2 (mean +/- SEM) (CI 46.8-59.2) ml kg-1 min-1 to 50.2 +/- 2.3 (43.8-56.6) ml kg-1 min-1 (P < 0.01), indicating overtraining. Baroreflex sensitivity (BRS) measured using the phenylephrine technique and blood pressure variability (BPV) did not change, but the low-frequency power of the R-R interval variability increased in the ETG (P < 0.05). The relative change in plasma volume was 7% in the ETG and 3% in the CG. The changes in BRS did not correlate with the changes in plasma volume, heart rate variability and BPV. We conclude that heavy endurance training and overtraining did not change baroreflex sensitivity or BPV but significantly increased the low-frequency power of the R-R interval variability during supine rest in female athletes as a marker of increased cardiac sympathetic modulation.

Exhaustive endurance training for 6-9 weeks did not induce changes in intrinsic heart rate and cardiac autonomic modulation in female athletes.

We investigated the effects of progressively increased training load and overtraining on resting and intrinsic heart rate (IHR) and cardiac autonomic modulation (CAM), and their relationships to performance variables. Nine athletes (ETG) increased training volume at 70-90% of maximal oxygen uptake (VO2max) by 130% (p<0.01) and training volume at <70% VO2max by 100% (p < 0.01) during 6-9 weeks. The corresponding increases in six female control athletes (CG) were 5 and 10%. Pharmacological blocking through atropine and propranolol and the Rosenblueth and Simeone model were used to calculate the sympathovagal balance index (Abal) and to measure IHR. The results were analysed using two-way analysis of variance. VO2max, IHR and Abal did not change. Resting heart rate had a tendency to decrease in the ETG and increase in the CG during the training period (interaction p < 0.01). Five ETG athletes demonstrated overtraining state (OA subgroup). Their VO2max (mean+/-SEM) decreased from 53.0+/-2.2 ml x kg(-1) x min(-1) to 50.2+/-2.3 ml x kg(-1) x min(-1) (p < 0.01), but no changes in resting HR, IHR and Abal were found. A significant correlation between the baseline values of VO2max and the parasympathetic activity index was found (r=-0.59, p < 0.05). In conclusion, progressively increased training load and overtraining did not induce significant changes in intrinsic heart rate or cardiac autonomic modulation in female endurance athletes. Resting heart rate rather decreased with heavy endurance training and overtraining. High maximal oxygen uptake was correlated with high cardiac parasympathetic modulation.

Heart rate and blood pressure variability during heavy training and overtraining in the female athlete.

We investigated heavy training- and overtraining-induced changes in heart rate and blood pressure variability during supine rest and in response to head-up tilt in female endurance athletes. Nine young female experimental athletes (ETG) increased their training volume at the intensity of 70-90% of maximal oxygen uptake (VO2max) by 125% and training volume at the intensity of < 70% of VO2max by 100% during 6-9 weeks. The corresponding increases in 6 female control athletes were 5% and 10%. The VO2max of the ETG and the control athletes did not change, but it decreased from 53.0 +/- 2.2 ml x kg(-1) x min(-1) to 50.2 +/- 2.3 ml x kg(-1) x min(-1) (mean+/-SEM, p < 0.01) in five overtrained experimental athletes. In the ETG, low-frequency power of R-R interval (RRI) variability during supine rest increased from 6 +/- 1 ms2 x 10(2) to 9 +/- 2 ms2 x 10(2) (p < 0.05). The 30/15 index (= RRI(max 30)/RRI(min 15), where RRI(max 30) denotes the longest RRI close to the 30th RRI and RRI(min 15) denotes the shortest RRI close to the 15th RRI after assuming upright position in the head-up tilt test), decreased as a result of training (analysis of variance, p = 0.05). In the ETG, changes in VO2max were related to the changes in total power of RRI variability during standing (r = 0.74, p < 0.05). Heart rate response to prolonged standing after head-up tilt was either accentuated or attenuated in the overtrained athletes as compared to the normal training state. We conclude that heavy training could increase cardiac sympathetic modulation during supine rest and attenuated biphasic baroreflex-mediated response appearing just after shifting to an upright position. Heavy-training-/overtraining-induced decrease in maximal aerobic power was related to decreased heart rate variability during standing. Physiological responses to overtraining were individual.

Hormonal responses to endurance training and overtraining in female athletes.

OBJECTIVE: To examine different hormonal responses to heavy endurance training and overtraining in female athletes. DESIGN: Submaximal and maximal treadmill tests, self-report mood measures, and stress hormone analyses were repeated at baseline, after 4 weeks and at the end of 6 to 9 weeks of experimental intensive training and after 4 to 6 weeks of recovery. SUBJECTS: Fifteen healthy female endurance athletes increased their intensive training volume by 130% and base training volume by 100% (ETG, n = 9) or served as controls (CG, n = 6). MAIN OUTCOME MEASURES: Maximal oxygen uptake (VO2max), mood dynamics, blood catecholamines, cortisol and testosterone at rest and after submaximal and maximal exercise, and nocturnal urine catecholamines. RESULTS: Five females from the ETG demonstrated an over-training state (OA subgroup) at the end of the training period. Their VO2max decreased (mean +/- SEM) from 53.0 +/- 2.2 ml.kg-1.min-1 (range, 46.8-59.2) to 50.2 +/- 2.3 ml.kg-1.min-1 (range, 43.8-56.6) (p < 0.01). Maximal treadmill performance expressed as oxygen demand decreased (mean +/- SEM) from 56.0 +/- 1.6 ml.kg-1.min-1 (range, 51.5-60.5) to 52.2 +/- 1.1 ml kg-1.min-1 (range, 49.1-55.3) (p < 0.01). Maximal heart rate also decreased (mean +/- SEM) from 190 +/- 1 bpm (range, 185-197) to 186 +/- 2 bpm (range, 184-193) (p < 0.05), and the athletes experienced mood disturbances. Plasma adrenaline levels at maximal and noradrenaline at submaximal work rate decreased during the last 2 to 5 training weeks (p < 0.05), and serum cortisol levels at maximal work rate decreased during the first 4 training weeks (p < 0.05) in the ETG. Plasma adrenaline at maximal work rate decreased during the first 4 training weeks (p < 0.05) in the OA subgroup. There were no changes in the CG. Individual hormonal response types to heavy training and overtraining were found. CONCLUSIONS: Hormone responses to exercise load are superior in indicating heavy training-induced stress when compared with resting hormone levels. These responses indicated decreased sympathoadrenal and/or adrenocortical activity (or exhaustion of the adrenal gland or the central nervous system). Individual hormonal profiles are needed to follow up training effects. Marked individual differences were found in training- and overtraining-induced hormonal changes.

Non-invasive evaluation of sympathovagal balance in athletes by time and frequency domain analyses of heart rate and blood pressure variability.

We examined how the time and frequency domain measures of heart rate and blood pressure variability at supine rest reflect the sympathovagal balance of 23 female and male endurance athletes. Pharmacological blocking by atropine and propranolol was used as a standard for defining autonomic control of the heart. The Rosenblueth and Simeone model for neural control of heart rate was used to calculate the sympathovagal balance index (Abal). Atropinization significantly decreased all time and frequency domain measures of heart rate and blood pressure variability. beta-Blockade significantly decreased further the low- (< 0.07 Hz) and medium-frequency power (0.07-0.15 Hz) variability of R-R intervals (RRI) and SD of RRI. Abal was 0.629 +/- 0.019, indicating that parasympathetic activity predominated in the athletes. Basal heart rate (r = 0.519, P < 0.01), SD of RRI (r = -0.533, P < 0.01), root-mean-square of successive RRIs (RRI RMSSD) (r = -0.579, P < 0.05), RRI total (r = -0.557, P < 0.01) and RRI high-frequency (HF) power (r = -0.582, P < 0.01) correlated significantly with Abal and parasympathetic activity index. We concluded that the best non-invasive method of evaluating the sympathovagal balance of athletes at supine rest is to measure SD of RRI, RRI RMSSD, HF and total power of RRI variability. All heart rate variability measures were mainly parasympathetically modulated. The nature of blood pressure variability measures remained unclear and they could not be used to evaluate the sympathovagal balance among athletes.

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.