Endurance Disciplines Research Articles

Energy Cost and Pole Forces during Nordic Walking under Different Surface Conditions

The purpose of the study was to identify the effect of three different surfaces on energy consumption and the forces acting on the walking poles during ground contact in Nordic walking (NW). Thirteen female NW instructors (age = 26 +/- 4 yr, weight = 58.5 +/- 4.2 kg, height = 168.1 +/- 4.6 cm) volunteered in the study. The subjects walked a distance of 1200 m at a controlled, constant speed of 2.2 m x s(-1) on each of a concrete surface (C), an artificial athletics track (A), and a naturally grown soccer lawn (G). They used NW poles with inbuilt strain gauge force transducers to measure ground reaction forces acting along the long axes of the poles. Oxygen uptake, capillary blood lactate (La), HR, and RPE were measured before and after the tests. Impact forces, maximum forces, force rates during ground contact identified from the registered force time histories, displayed significant differences related to the surface conditions. However, force time integrals did not show surface-related differences. Relative oxygen consumption showed significant differences between NW on C and on G whereas no surface-related differences could be identified between the surface conditions for the parameters La, HR, and RPE. Our data indicate that the impulse that is generated by the poles on the subjects is identical between the varying surfaces. Because there are differences for the oxygen uptake between C and G, the main regulator for the propulsion must be the musculature of the lower extremities. The work of the upper extremities seems to be a luxury effort for Nordic walkers with a proper technique.

Menstrual Status And Hyperandrogenism In Olympic Athletes In Power, Endurance And Technical Disciplines

Menstrual disturbances are highly prevalent in elite sports women, and represent one of female athletes' serious medical conditions. Such menstrual dysfunctions are often explained by caloric deficiency in combination with intense exercise. However, recently essential hyperandrogenism like poly cystic ovary syndrome (PCOS) has been described as an alternative mechanism. PURPOSE: To assess menstrual status, hormone levels and polycystic ovaries in Olympic athletes in power, endurance and technical disciplines. METHODS: Ninety female athletes, all members of the Swedish Olympic troops, underwent a general and gynaecological health assessment including vaginal ultrasound for evaluation of ovaries. Blood samples were collected for hormone analyses. Groups of athletes within power (e.g. downhill skiing, taekwando), endurance (e.g. cross-country skiing, cycling) and technical disciplines (e.g. curling, archery) were compared. RESUITS: Endurance athletes had the lowest mean BMI (21.6 ±1.8 versus 22.7 ± 1.8 in power sports, p<0.05 and 21.8 ± 1.3 in technical sports, n.s.). Hormonal contraceptives (HC) were used by 51 % of the athletes with no difference between groups. In athletes not taking HC, 77.8% of athletes in endurance disciplines were found to have menstrual disturbance, compared to 13.3% in power sports (p<0.001) and 33.3% in technical disciplines (p=0.06). We found no differences in hormone levels between disciplines. However, levels of free testosterone were higher in athletes with menstrual disturbance compared to regularly menstruating athletes without and with HC. Furthermore, the frequency of PCOS was significantly higher among athletes with menstrual disturbance compared to eumenorrheic athletes. CONCLUSIONS: Menstrual dysfunctions were most prevalent in sportswomen in endurance disciplines, and essential hyperandrogenism, like PCOS, seems to be an important cause of menstrual disturbances in these Olympic athletes. The medical consequences of PCOS in elite women and its role for physical performance remain to be determined.

Body Composition In Relation To Menstrual Status In Olympic Athletes In Power, Endurance And Technical Disciplines

Menstrual disturbances in athletes may be related to body composition and particularly low amount of body fat. In turn, long-standing amenorrhea will lead to an increased bone resorption. Although this serious condition has been extensively characterized in athletes in disciplines that emphasize leanness, little is known about body composition in relation to menstrual status in athletes of other disciplines. PURPOSE: To determine body composition in relation to menstrual status in Olympic athletes in power, endurance, and technical disciplines. METHODS: Ninety female athletes, all members of the Swedish Olympic troops, underwent a general and gynaecological health assessment and a Dual energy X-ray absorptiometry (DXA) for determination of body composition. Groups of athletes within power (e.g. downhill skiing, taekwando), endurance (e.g. cross-country skiing, cycling) and technical disciplines (e.g. curling, archery) were compared. RESULTS: Endurance athletes had the lowest mean BMI and body fat content (19.1 ± 5.6% versus power: 21.7 ± 5.2%, p<0.05 and technical: 25.1 ± 6.8%, p<0.01). Power athletes had the highest total bone mineral density (BMD) compared to endurance and technical athletes (p<0.001, respectively). Menstrual disturbance was most common among endurance athletes (77.8% of those not taking hormonal contraceptives), compared to 13.3% in power sports (p<0.001) and 33.3% in technical disciplines (p=0.06). Athletes with menstrual disturbance had the lowest amount of body fat and significantly lower total BMD than regularly menstruating subjects and lower spinal BMD than athletes taking hormonal contraceptives. However, only one woman with menstrual disturbance had osteopenia. CONCLUSIONS: In this study, Olympic female athletes in endurance disciplines had lower amount of body fat, higher frequency of menstrual disturbances and lower BMD than athletes in power and technical disciplines. Women with menstrual disturbances had the lowest amount of body fat and BMD. However, their values were, for all but one woman having osteopenia, in the normal range, which may reflect an increasing awareness of the importance of healthy training and nutritional habits, or the selection of athletes with optimal physique at this level.

Timeframe to Detect Blood Withdrawal Associated with Autologous Blood Doping.

Autologous blood doping is a commonly applied and not yet detectable form of blood manipulation in endurance disciplines. One promising detection strategy could be based upon regular measurements of total hemoglobin mass (tHb) in order to discover blood withdrawal and blood re-infusion. The recently developed optimized CO rebreathing method (oCOR-method) to determine tHb is accurate (typical error 1.7%) and may therefore be suitable when applying this strategy. PURPOSE: To determine the magnitude of tHb-loss, the time required for recovery of tHb, and the timeframe available for secure detection of phlebotomy of one unit of blood, respectively. METHODS: 550ml of blood were withdrawn in 9 moderately trained male and female subjects (VO2max 46–69ml/min/kg). 6 matched subjects served as a control group (VO2max 46–64ml/min/kg). tHb and blood volume (B V) were determined using the oCOR-method before (4 times), 1 day after phlebotomy, and twice a week for a total of 49 days. VO2max was obtained before and on day 1,10, 20, and 40, thereafter. RESULTS: The mean loss of tHb was 77.0 ±21.7g which was completely recovered on day 26. A true decrease in tHb, exceeding the 99%-confidence limits of the method (4.4%), was found in all individuals up to and including day 12. BV only temporarily decreased on day 1 and returned to initial values thereafter. VO2max was reduced by 255 ±130ml/min (p< 0.001) on day 1 after phlebotomy, was still decreased on day 10 (−197 ±116ml/min, p<0.01), and had recovered on day 20 (−58 ±158ml/min). CONCLUSION: Complete recovery from phlebotomy of one unit of blood occurs within 26 days. Its detection for anti doping purposes is possible for at least 2 weeks. During this time endurance performance is suppressed since the loss of 1g of hemoglobin is associated with a decrease in VO2max of 3.1ml/min.

Corticotroph axis sensitivity after exercise: Comparison between elite athletes and sedentary subjects

Strenuous exercise activates the hypothalamic-pituitary-adrenal (HPA) axis. Several reports showed that physical training is associated with a decreased efficiency of the feedback control of HPA axis. The aims of the present study were: 1) to evaluate the differences in the mechanical, hormonal, and lactate responses to a high-intensity isokinetic exercise among different groups of competitive athletes (CA, no.=20) of power and endurance disciplines and sedentary controls (SED, no.=10); 2) to determine the effects of the training status on the HPA axis responsiveness following exercise, as indirectly evaluated by the rates of ACTH, cortisol, and DHEA recovery after exercise. CA and SED fulfilled eight sets of twenty concentric contractions of the knee extensors at 180 degrees/sec angular velocity throughout a constant range of motion (100 degrees). There was a rest period of 30 sec between each set and a 3-min rest period between the two legs. Before, immediately after the isokinetic exercise and at different times in the subsequent 120 min of recovery, blood and saliva were sampled to determine plasma ACTH, salivary cortisol, serum DHEA, and serum lactate concentrations. CA showed a higher cortisol response to exercise than SED, whereas no differences were found in the responses of ACTH, DHEA and lactate. In the athlete group the exercise-induced increases of ACTH, cortisol, and lactate were higher in power athletes with respect to endurance athletes. No differences were observed between athletes and SED in the rates of hormonal recovery after exercise: this finding does not support the concept that a reduced feedback control of HPA axis can represent a feature of trained individuals.

Careers In Cycling

For successful careers in endurance sports, long-term discipline specific training and competition have been addressed as being of crucial importance. Sporting bodies in many countries deploy considerable funds to develop junior high performance programs to prepare young athletes for future success in the elite class. Junior world championships are held in many disciplines. It is unknown, how many of the former top junior athletes reach success in the elite class. PURPOSE To investigate the careers of athletes having participated in major junior or elite cycling races. This data could help in refining development programs in high performance sports. METHODS Official results from major junior (athletes age ± 18 yr.) and elite (age >18 yr.) cycling races (world championships road + track endurance disciplines, Olympic games and “Grand Tours” (Tour, Giro, Vuelta)) from 1979 to 2002 were analysed. According to their achievement in the races, riders were categorised as follows: Podium (rank 1–3), Top Ten (4–10), and Participation (10-end), age and country of origin. Career lengths were calculated as the time span between the first and last result recorded. Careers of riders who presented results in both junior and elite races were compared to riders that had no junior race results. RESULTS 26213 individual rankings were extracted. Retrospectively, 66,3% of all Top Ten finishers in elite world championship races (57,7% road, 80,3% track endurance) and 25,6% of the podium finishers of the “Grand Tours” had previously participated in major junior competitions. Former juniors reached the top elite level earlier than athletes that had no junior results. Career lengths showed no significant difference between the two groups (2,7 ± 3,1 years). There was no correlation between placing in the junior and the elite class (Podium, Top Ten, Participation). However, top achievers in the sport (=career length >10yr. or >20 placings) had mostly been present as junior athletes. Significant differences in having success in the elite class for junior athletes between the different countries were found. CONCLUSIONS Success in elite cycling races is based on long term activity in the sport with participation in international junior races. Participation, not success in these junior competitions seems to be of significance. The data underline the importance of structured performance programs for young athletes.

Erythrocytic System under the Influence of Physical Exercise and Training

It is obvious that physical performance, endurance capacity and resistance to fatigue in humans are dependent upon many different factors. One factor, the oxygen carrying capacity of blood, seems to be of particular importance. This factor is mainly determined by haemoglobin concentration, number of circulating erythrocytes and the efficiency of their functions. A single bout of physical effort and, even more, repeated exercise may change the morphological indices of blood and influence the erythropoietic processes in the bone marrow. That is why there is so great an interest now attached to the effects of physical exercise on the erythrocytic system. Although in recent years many papers have been published on the subjects their findings pertaining to the effects of single bouts of exercise and systematic training on the erythrocytic system are often contradictory. The haematological parameters in some top-class athletes, particularly those performing in endurance disciplines are lowered at rest. Anaemia has been described in sportsmen, even among the members of Olympic teams. This type of anaemia has been called 'sports anaemia', 'athletes' anaemia' or 'postexercise anaemia' in order to emphasise its character. Among many possible causes which may bring about the development of sports anaemia the most commonly recognised are: postexercise plasma expansion, intensified haemolysis during physical efforts, iron deficiency, losses of erythrocytes by the way of bleeding into the digestive and urinary systems and also some disturbances in erythropoiesis. However, there is evidence of the intensification of erythropoiesis by many factors occurring during physical exercise.

The long-term involution of physiological cardiomegaly and cardiac hypertrophy

The long-term involution of physiological cardiomegaly and cardiac hypertrophy. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 244-249, 1989. Forty-five former athletes in endurance disciplines, primarily Olympic medalists and World Cup, European Cup, and German champions, for whom results of an exercise ECG and radiological heart volume measurement were available from their active competitive phase, were examined. The study protocol included clinical examination, laboratory controls, resting and exercise ECG, determination of cardiac volume, and one- and two-dimensional echocardiographic examination. Of the 45 former athletes contacted, 38 appeared for examination. Of these, four presented with heart disease (two with infarction, one with aortic stenosis, and one with arrhythmia). The remaining 34 were divided into groups of still active (more than 300 kcal.wk-1) and inactive (less than 300 kcal.wk-1) athletes. The interval between the first and second examination averaged 23 yr. The active former athletes showed a weight increase of 5.2% (P less than 0.01) and a reduction of 14% in ergometric performance (P less than 0.02). The inactive group had a marked weight increase of 17.4% (P less than 0.001); the ergometric performance was lowered by 20% (P less than 0.001). The absolute heart size had decreased in the active group by 6.1% (NS) and the relative heart size by 10.7% (P less than 0.005); the corresponding values in the inactive group were 4.5% (NS) and 18% (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)