Showing papers in "International Journal of Sports Medicine in 1996"

Variability in serum creatine kinase response after eccentric exercise of the elbow flexors.

Abstract: There is a large inter-subject variability in serum creatine kinase (CK) response after eccentric exercise. This study examined and compared the variability of CK activity, other serum protein increases (aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, aldolase, myoglobin),changes in muscle damage indicators (maximal isometric force: MIF, relaxed and flexed elbow joint angle: RANG and FANG, circumference: CIR, and muscle soreness level: SOR), and changes in magnetic resonance (MR) images. Ten male subjects (21.7 +/- 1.6 yrs) performed 24 maximal eccentric actions of the elbow flexors, and measurements except MR images were taken immediately before and after, and for 10 days after exercise. MR images were taken 7 days after exercise. A large variability in peak CK response (236 - 25,244 IU.I(-1) was found among subjects. Spearman rank-order correlation coefficients (r) revealed significant correlations of peak CK with peak serum protein levels (r = 0.79-0.95), peak changes in MIF (r = 0.73-0.79), RANG (r = 0.69), and CIR (r = 0.91). The higher the peak CK levels, the more profound the abnormality in the MR images and the larger the changes in MR signal intensity (r = 0.90-0.94). It is concluded that the large variability in CK response after exercise seems to be related to the variability in exercise-induced muscle damage.

DNA damage after exhaustive treadmill running in trained and untrained men.

Abstract: The single cell gel electrophoresis (SCG) assay was used to compare the occurrence of DNA damage in peripheral white blood cells in 6 trained (TR) and 5 untrained (UT) men after exhaustive exercise. The subjects completed an incremental treadmill test until exhaustion (maximal lactate: 12.9 +/- 1.7 in TR and 12.2 +/- 2.5 mmol.l-1 in UT). A clear and significant increase of DNA migration from 2.31 +/- 0.20 (TR) and 2.22 +/- 0.16 (UT) at rest to 2.65 +/- 0.30 (TR) and 3.00 +/- 0.41 tail moment (UT) was found 24 hours after exercise. Noteworthy is that the increase of DNA migration was significantly lower in TR (+ 18.7 +/- 6.8%) compared to UT (+ 35.7 +/- 8.9%). Plasma levels of malondialdehyde (MDA) were not significantly increased in TR and UT after exercise. At rest and 15 minutes after exercise MDA-values were significantly lower in TR compared to UT. In conclusion the present investigation demonstrates the occurrence of DNA damage in white blood cells following exhaustive exercise. This observation may be induced by oxidative stress. Our data suggest that adaptation to training seems to be capable of reducing free radical associated effects, such as DNA damage. Further investigations are needed to clarify the causal mechanisms and biological relevance of exercise-induced DNA damage.

Athlete's Heart: A Meta-Analysis of the Echocardiographic Experience

Abstract: Meta-analytical techniques were applied to selected echocardiographic reports on athlete's heart. The combined analysis of studies in which competitive long-distance runners were compared to matched nonathletic control subjects, revealed a 10% (p < 0.001) higher left ventricular internal diameter in the runners, an 18% (p < 0.001) thicker wall and an 8% (p < 0.05) greater relative wall thickness. In strength athletes these differences averaged +2.5% (p < 0.01), +15% (p < 0.05) and +12% (p < 0.05), respectively, and in cyclists +9% (p < 0.05), +29% (p < 0.01) and +19% (p <0.05). When compared to their respective controls, left ventricular mass was larger by 64% (p < 0.01) in cyclists, 48% (p < 0.001) in runners and 25% (p < 0.05) in strength athletes. There were no differences in left ventricular systolic or diastolic function at rest. The meta-analysis of longitudinal studies, in which athletes were assessed in active and inactive periods, suggested that at least part of the differences from nonathletes can be ascribed to the training per se. In conclusion, the classification of left ventricular hypertrophy in athletes as eccentric or concentric has to be considered as a relative concept, most likely related to the fact that training regimens and/or sports activities are not exclusively of the dynamic or static type but comprise both components to a variable extent.

Assessment of the reproducibility of performance testing on an air-braked cycle ergometer.

Abstract: The purposes of this study were (I) to assess the reproducibility of endurance performance testing on an air-braked cycle ergometer, and (II) to compare laboratory performances to performances in road races. Ten well-trained, competitive cyclists (peak power output [PPO] 443 +/- 37 W, [values are mean +/- SD]) undertook either: (I) three 20 km and three 40 km time trials (TT) on an air braked ergometry system (Kingcycle) (n = 6), and/or (II) three 40 km laboratory TT and two 40 km road TT competitions (n = 8). The time taken for the laboratory simulated 20 km and 40 km TT rides were highly reproducible (coefficient of variation 1.1 +/- 0.9% and 1.0 +/- 0.5%, respectively). However, the mean power output and heart rate were significantly different (p < 0.0001) between the 20 km and 40 km TT (327.5 +/- 16.9 vs 303.9 +/- 14.9 W and 171.4 +/- 5.1 vs 168.3 +/- 4.4 beats/min, respectively). A strong relationship (r = 0.99, p < 0.001) was observed between the mean cycling time and the average sustained power output. A significant correlation (r = 0.98, p < 0.001) was also observed between laboratory and road race times, although road race times were, on average, some 8% slower. These findings indicate that the Kingcycle ergometry system can be used as a reliable method of assessing short term endurance cycling performance.

The Conconi Test: Methodology After 12 Years of Application

Abstract: The protocol for the determination of the speed/heart rate relationship during incremental exercise previously described (so-called Conconi test) has been refined and in part modified during 12 years of application. The new protocol calls for time-based increments in exercise intensity that are uniform up to submaximal speeds and progressively greater in the final phase. As in the original article (18), the speed/heart rate relationship is linear at low to moderate speed and curvilinear from submaximal to maximal speeds. A method is presented for the mathematical definition of this relationship, with the calculation of the straight-line equation of the linear phase and the identification of the point of transition from the linear to the curvilinear phase (deflection point or heart rate break-point). Analysis of 300 tests selected at random from those in our data base (more than 5,000 tests) has enabled us to show that the speed at which the deflection point occurs is significantly lower (p < 0.001) than that at which the acceleration of the final phase begins. This fact demonstrates that the break-point is not brought on by the final acceleration called for in the test protocol. Analysis of the speed/heart rate relationship allows for the determination of the following additional functional indices: 1) maximal heart rate (in 21 athletes the maximal heart rate attained in the test and that attained while racing were equal); 2) range of heart beats defining the linear part of the speed/heart rate relationship; 3) range of heart beats from the deflection point to maximal heart rate; and 4) maximal aerobic exercise intensity, obtained through extrapolation of the straight-line equation to maximal heart rate. Data are provided on the conditions of the test subject that modify his speed/heart rate relationship, such as incomplete recovery from previous efforts, inadequate warm-up, or inadequate test procedure with too rapid increments in exercise intensity. Finally, criteria for test acceptability are presented.

Is Peak VO2 a Maximal Index of Children's Aerobic Fitness?

Abstract: A levelling of oxygen uptake (VO2 plateau) at high exercise intensities is conventionally used as the criterion for establishing VO2max during progressive, incremental exercise testing. Only a minority of children, however, demonstrate a VO2 plateau during exercise to voluntary exhaustion. This study was therefore designed to investigate whether a VO2 plateau is required before peak VO2 can be considered a maximal index of children's aerobic fitness. Eighteen girls and 17 boys (age 9.9 +/- 0.4 yrs) carried out three treadmill tests to exhaustion one week apart. The first test comprised a discontinuous, incremental protocol to voluntary exhaustion. In test two each child warmed up and then ran to exhaustion at the same belt speed but on a gradient 2.5% greater than that which had produced an exhaustive effort on the first test. The third test was conducted similarly but the treadmill gradient was raised to 5% greater than that which had produced an exhaustive effort on the first test. Seven girls and 6 boys demonstrated a VO2 plateau (< or = 2 ml.kg-1.min-7) on the first test but no significant differences in either anthropometrical or peak physiological data were detected between those who demonstrated a plateau and those who did not. Mean peak VO2 values during tests two and three (supramaximal tests) did not increase significantly above that achieved on test one although indicators of an increased anaerobic contribution were significantly higher in both supramaximal tests. These findings indicate that peak VO2 in test one was a maximal value despite the absence of a VO2 plateau. The requirement of a VO2 plateau before peak VO2 can be regarded as a maximal index of young children's aerobic fitness is therefore untenable.

Relationships Between Testosterone, Cortisol and Performance in Professional Cyclists

Abstract: In the literature the use of plasma levels of cortisol and the testosterone and testosterone: cortisol ratio for training management is encouraged. Decreased levels of testosterone and increased levels of cortisol are suggested to be indicative for a disturbance in the anabolic-catabolic balance, which may express itself in decreased performance. The purpose of the study was to examine if the acute hormonal response to a bout of exercise and the resting levels of testosterone, luteinizing hormone (LH) and cortisol are correlated to performance in cyclists. In addition, the effect of training on this correlation was studied. Ten professional cyclists participated and measurements took place before and after a defined period of training. Maximum workload (Pmax), determined on a cycle-ergometer with a slowly increasing protocol, increased by 30 watt (p < 0.001). Workload at a lactate level of 4 mmol/l (P4) increased by 18 watt (p < 0.05). Post training, resting testosterone levels decreased from 28.8 +/- 74 nmol/l to 24.6 +/- 90 nmol/l (p < 0.05). Resting cortisol levels increased from 272 +/- 110 nmol/l pre training to 379 +/- 242 nmol/l post training (p < 0.05). These results indicate an increased catabolic state. The acute hormonal response and the resting levels of LH were not changed post training. The resting levels of testosterone and cortisol and the acute response to exercise showed no correlation with performance pre and post training. In spite of an increased catabolic state post training there was an increase in performance. These results suggest that in endurance trained cyclists, decreased testosterone levels, increased cortisol levels and a decreased testosterone: cortisol ratio does not automatically lead to a decrease in performance or a state of overtraining.

Structural and functional adaptations of the cardiovascular system by training

Abstract: Muscular training induces structural and functional adaptations within the cardiovascular system which vary according to type, intensity and duration of muscular exertion. Dynamic muscular training for more than 5 h a week involving more than 1/6th of the skeletal muscle mass causes an increase in parasympathetic tone and an eccentric myocardial hypertrophy. The dimensions of all cardiac chambers enlarge up to 20% and the cardiac muscle mass may increase by 70%-80%. Static muscular training does not induce any change in the parasympathetic heart regulation, nor does it lead to any disproportional increase in cardiac muscle mass relative to skeletal muscle mass. However, a tendency towards a concentric myocardial hypertrophy can be observed. The effects of regular muscular training on the arteries are the subject of current scientific investigation. To explain the acute and chronic adaptations of the arterial vasculature to exercise, a "shear stress" hypothesis has been proposed. During dynamic muscular exercise the regional arterial blood flow is enhanced. This leads to an acute increase in intraluminal shear forces, which stimulates the vascular endothelium with a reactive flow-dependent regional vasodilation mediated by endothelial-derived relaxing factors (EDRF, EDNO). Chronic enhancement of shear forces induces endothelial cell-mediated alterations in gene expression (endothelin, growth factors, regulators of fibrinolysis) and chronic structural adaptations of the vascular wall (cytoskeletal redistribution, cell shape change). Recent duplex sonographic studies in humans have revealed a significant lumen increase of muscular type arteries induced by dynamic, predominantly aerobic muscular training, but not by static muscular training. These structural adaptations are confined to those arteries supplying exercising muscle groups, whereas functional adaptations with an improvement of regional compliance are found in all arteries.

Injuries in male soccer players: team risk analysis

Abstract: Selection may be responsible for different characteristics of subgroups (teams) of soccer players resulting in different risks of injury and different injury patterns. In the present study injury rates of teams were analysed with respect to the factors age and level of play. In two Dutch non-professional soccer clubs 477 male players, active in teams of different age groups and at different levels of play, were prospectively followed during the second half of the 1986/1987 competitive season. Teams in the 17/18 years age group showed the highest incidence of injury per 1000 players hours in games. At a high level of play teams have a significantly (p < 0.01) higher risk of injury than teams at a low level of play. This difference is noticed within every age group with exception of the 15/16 years age group. At a high level of play teams of senior players have significantly (p < 0.005) more prevalent injuries than teams of junior players. Senior players, active at a high level of play, have significantly (p < 0.05) more overuse injuries than senior players of a low level of play. At a high level of play significantly (p < 0.05) more upper leg injuries are reported. In the total population of soccer players relatively more sprains are located in the ankle joint and relatively more strains are located on the upper leg. It is concluded that prevention of soccer injuries primarily should be aimed at teams and their environment and not at the individual soccer player.

Comparative Study of Lactate Removal in Short Term Massage of Extremities, Active Recovery and a Passive Recovery Period After Supramaximal Exercise Sessions

Abstract: This investigation highlights the comparison of blood lactate removal during the period of recovery in which the subjects were required to sit down as a passive rest period, followed by active recovery at 30% VO(2)max and short term body massage, as the three modes of recovery used. Ten male athletes participated in the study. Exercise was performed on a bicycle ergometer with loads at 150% VO(2)max, each session lasting 1 min, interspaced with 15 sec rest periods, until exhaustion. Blood lactate concentration was recorded at recovery periods of 0,3, 5, 10, 20, 30, and 40 min, while VO(2), VCO(2) and heart rate were recorded every 30 sec for 30 min. The highest mean lactate value was found after 3 min of recovery irrespective of the type of modality applied. Significantly lower half life of lactate was observed during active recovery (15.7 +/- 2.5 min) period, while short term massage as a means of recovery required 21.8 +/- 3.5 min and did not show any significant difference from a passive type of sitting recovery period of 21.5 +/- 2.8 min. Analysis of lactate values indicated no remarkable difference between massage and a passive type of sitting recovery period. It was observed that in short term massage recovery, more oxygen was consumed as compared to a passive type of sitting recovery. It is concluded from the study that the short term body massage is ineffective in enhancing the lactate removal and that an active type of recovery is the best modality for enhancing lactate removal after exercise.

Pre-exercise glycerol hydration improves cycling endurance time

Abstract: The effects of glycerol ingestion (GEH) on hydration and subsequent cycle ergometer submaximal load exercise were examined in well conditioned subjects. We hypothesized that GEH would reduce physiologic strain and increase endurance. The purpose of Study I (n = 11) was to determine if pre-exercise GEH (1.2 gm/kg glycerol in 26 ml/kg solution) compared to pre-exercise placebo hydration (PH) (26 ml/kg of aspartame flavored water) lowered heart rate (HR), lowered rectal temperature (Tc), and prolonged endurance time (ET) during submaximal load cycle ergometry. The purpose of Study II (n = 7) was to determine if the same pre-exercise regimen followed by carbohydrate oral replacement solution (ORS) during exercise also lowered HR, Tc, and prolonged ET. Both studies were double-blind, randomized, crossover trials, performed at an ambient temperature of 23.5-24.5 degrees C, and humidity of 25-27%. Mean HR was lower by 2.8 +/- 0.4 beats/min (p = 0.05) after GEH in Study I and by 4.4 +/- 1.1 beats/min (p = 0.01) in Study II. Endurance time was prolonged after GEH in Study I (93.8 +/- 14 min vs. 77.4 +/- 9 min, p = 0.049) and in Study II (123.4 +/- 17 min vs. 99.0 +/- 11 min, p = 0.03). Rectal temperature did not differ between hydration regimens in both Study I and Study II. Thus, pre-exercise glycerol-enhanced hyperhydration lowers HR and prolongs ET even when combined with ORS during exercise. The regimens tested in this study could potentially be adapted for endurance activities.

Cycling cadence alters exercise hemodynamics.

Abstract: Previous studies on cycling cadence have focused on the economy of the cadence, in search of the optimal pedal cadence. The purpose of this study was to determine the hemodynamic changes associated with varying pedal cadence at a constant workload. It was hypothesized that increased pedal cadence would enhance the skeletal muscle pump, resulting in elevation of cardiac output. Seven cyclists were enlisted to cycle at 200 watts at pedal cadences of 70, 90 and 110 rpm (random order). Oxygen uptake, heart rate, stroke volume, cardiac output, blood pressure, and vascular resistance were determined. As has been previously shown, oxygen uptake increased with increased cadence (70, 90, 110 rpm) at this workload. Heart rate, stroke volume, cardiac output and blood pressure were increased, and vascular resistance decreased, with increased cadence. Cardiac output increased (34%) in excess of the increase in oxygen uptake (15%) as shown by the decrease (-14.5%) in the arterial-venous oxygen difference occurring with increasing cadence. Apparently, even though the workload was constant, the increase in pedal cadence resulted in a more effective skeletal-muscle pump which increased muscle blood flow and venous return. It is not known if this might contribute to the natural selection of higher cadences by cycling athletes, even though there is reduced economy.

Effects of Exhaustive Endurance Exercise and its One-Week Daily Repetition on Neutrophil Count and Functional Status in Untrained Men

Abstract: Whereas endurance exercise is known to induce marked neutrophilia, it remains to be fully understood as to whether the cell functions are altered as well as whether the adaptability of the responses to training occurs. To address both of these issues, we undertook the present longitudinal investigation in ten healthy untrained men (20-24 years, VO2max 39.1 +/- 4.2 ml/kg/min). The exercise protocol was 7 consecutive sessions of the same workload performed each day for 1.5 h at an intensity of 70% of VO2max. Peripheral blood samples were obtained before, immediately after, and 1 h after exercise on Days 1, 4, and 7, and served for determination of total and differential leukocyte counts, chemotaxis and chemiluminescence of neutrophils. Acute endurance exercise caused marked peripheral neutrophilia with significant increase in both absolute number and relative proportion of band neutrophils (p < 0.01, respectively), indicating partial recruitment of bone marrow neutrophils. While chemotaxis remained unaltered following exercise, reactive oxygen species generation of neutrophils, measured by luminol-dependent chemiluminescence upon stimulation with opsonized zymosan, was not only significantly enhanced following exercise (p < 0.01), but also associated with the proportional increase in band neutrophils (r = 0.727, p < 0.05), suggesting that neutrophils mobilized from the bone marrow following endurance exercise may possess higher responsiveness. On the other hand, the magnitude of the exercise-induced changes was reduced gradually by daily repeated exposure to endurance exercise, but none of the trends were significant except the decline in resting segmented neutrophil counts (p < 0.05) at least during a 1-wk period of repeated exercise sessions.

Isokinetic Muscle Performance After Anterior Cruciate Ligament Surgery: Long-Term Results and Outcome Predicting Factors After Primary Surgery and Late-Phase Reconstruction

Abstract: The purpose of this study was to evaluate the long-term isokinetic muscle performance after ACL surgery and to analyze by a multiple stepwise regression which factors (if any) predict the overall outcome. The study subjects were 119 patients who had a complete rupture of the ACL and had been treated surgically at the Tampere University Hospital between 1981 and 1990. They were divided into the acute group (N = 62) and into the chronic group (N = 57) according to the time delay between the injury and the ACL surgery. The isokinetic strength measurements of the quadriceps and hamstring muscles were performed on average 4 years after the operation using Cybex II and Cybex 6000 dynamometers (Lumex Inc., Ronkokoma, NY, USA). The peak torques were determined at speeds of 60 and 180 degrees/s and the peak work at speed of 180 degrees/s. The measurements revealed that after the ACL surgery there was still a considerable thigh muscle strength deficit especially in extension of the injured extremity, the average extension strength deficit ranging from 9 to 20%. The extension strength deficit was significantly more prominent in the chronic (18-20%) than in the acute group (9-15%). The extension strength deficit was significantly greater ar the slower (15-20%) than higher (9-18%) speed of the isokinetic movement. In both the acute and chronic groups, a multiple stepwise regression analysis indicated that patellofemoral pain and flexion deficit of the knee were the factors that most frequently and significantly associated with the strength deficits. At the higher speed of the isokinetic movement, these two factors accounted 20% and 21% for the variation seen in the quadriceps strength deficit of the acute group and the chronic group. No correlation could be found between age, sex, height, weight, body mass index, length of the follow-up time, injury type, athletic activity level, immobilization method, knee stability, and the isokinetic muscular performance.

Gender differences in adrenergic regulation of lipid mobilization during exercise.

Abstract: Gender differences in adrenergic regulation of lipid mobilization during exercise. Hellstrom L, Blaak E, Hagstrom-Toft E. Department of Medicine, Huddinge Hospital, Karolinska Institute, Sweden. Gender differences in adrenergic regulation of glycerol levels in subcutaneous, abdominal adipose tissue were investigated during submaximal exercise in non-obese, healthy men and women, using microdialysis. During exercise, glycerol levels in venous plasma and venous serum concentrations of free fatty acids increased more in women and reached about two-fold higher values than in men (p < 0.005 or less). Plasma noradrenaline and insulin did not differ between the sexes, whereas plasma adrenaline was two-fold higher in men than in women during exercise (p < 0.01). The glycerol levels in adipose tissue increased during exercise and decreased in the post-exercise period in either sex. When the non-selective beta adrenoceptor blocking agent propranolol was added to the microdialysis perfusate before exercise was initiated, the subsequent increase in dialysate glycerol was significantly diminished in both sexes (p < 0.05). A similar addition of the alpha adrenoceptor blocking agent phentolamine, however, caused a significant further rise in tissue glycerol in men (p < 0.05), whereas the exercise induced increase in glycerol levels remained unaffected by phentolamine in women. Adipose tissue blood flow did not change during exercise in either men or women. In either sex, dialysate lactate levels increased during exercise. This increase was not altered if alpha- or beta-blocking agents were added to the perfusate. In summary, during short term submaximal work, women have a higher increase in circulating lipid than men. This appears, at least in part, to be due to a sex difference in the adrenergic regulation of lipid mobilization during exercise. In men exercise activates beta- as well as alpha-adrenergic receptors in adipose tissue, whereas only beta receptors are activated in adipose tissue of women. Finally, methodological investigations indicate that microdialysis is a valid method for short-term exercise experiments.

Power spectral analysis of RR interval and blood pressure short-term variability at rest and during dynamic exercise : Comparison between cyclists and controls

Abstract: To determine the adaptations of the autonomic nervous system in the control of heart rate and blood pressure induced by endurance training, 10 competitive cyclists aged 27 ± 7 years and 10 age, weight- and height-matched sedentary controls were subjected to Power Spectral Analysis of the RR interval and of blood pressure at supine rest and during submaximal cycloer-gometric exercise test in the supine position at 20 % and 40 % of maximal workload. At rest, the high-frequency (HF) power of the RR interval was higher in cyclists (p < 0.05) compared to) controls, whereas the power spectrum of both systolic and diastolic blood pressure did not differ between cyclists and controls. During exercise the variance, the low-frequency (LF) and the HF power of the RR interval decreased significantly (p < 0.005) and similarly in cyclists and controls. The LF/HF ratio of the RR interval increased (p < 0.001) and the alfa index of baroreflex sensitivity decreased (p < 0.05) without differences between cyclists and controls. The variance of both systolic and diastolic blood pressure increased (p < 0.001 and p < 0.005, respectively) as well as the HF power of systolic blood pressure (p < 0.001) similarly in cyclists and in controls. In conclusion, the data of the present study suggest that competitive cycling causes an enhanced vagal drive to the sinus node, whereas the neural control of blood pressure is not affected. During exercise a vagal withdrawal and a sympathetic activation in the neural control of heart: rate, together with a reduction of baroreflex sensitivity are operative. These changes are similar in cyclists and controls.

Physical Activity Levels of 5-11-Year-Old Children in England: Cumulative Evidence from Three Direct Observation Studies

Abstract: The aim of this study was to determine the physical activity levels of a sample of young children. Data were collected using direct, continuous observation by trained observers. The observational method utilised a points system to differentiate intensity of physical activity. Observations were carried out during school break times, lunch times and physical education lessons and during free time outside of school. The sample consisted of 93 girls and 86 boys aged between 5 and 11 years. Only 38 children (21%) engaged in a sustained 20-min period of moderate to vigorous physical activity (MVPA), but nearly all children (95%) took part in a 5-min period of MVPA. The highest recordings of MVPA occurred during school break times but MVPA was less prominent during free time outside of school. One hundred and seventy eight children were observed during school physical education lessons. Sustained MVPA was particularly low during physical education lessons with only 13 children (8%) participating in at least one sustained 10-min period. There appeared to be no difference in activity levels between boys and girls or between children of differing ages. During all observation periods the main activity of the child was recorded. Soccer, brisk walking, general play and chasing games were the most common activities. The results are disturbing since preadolescent children appear to be engaging in very little sustained, playful physical activity during their free time outside of school. If childhood is considered to be the most active stage of life there must be concern for the future. There is a need for health professionals to promote active lifestyles from birth.

Vitamin C and Common Cold Incidence: A Review of Studies with Subjects Under Heavy Physical Stress

Abstract: Several studies have observed an increased risk of respiratory infections in subjects doingheavy physical exercise Vitamin C has been shown to affect some parts of the immune system,and accordingly it seems biologically conceivable that it could have effects on the increasedincidence of respiratory infections caused by heavy physical stress In this report the results ofthree placebo-controlled studies that have examined the effect of vitamin C supplementation oncommon cold incidence in subjects under acute physical stress are analyzed In one study thesubjects were school-children at a skiing camp in the Swiss Alps, in another they were militarytroops training in Northern Canada, and in the third they were participants in a 90 km runningrace In each of the three studies a considerable reduction in common cold incidence in thegroup supplemented with vitamin C (06–10 g/day) was found The pooled rate ratio (RR)of common cold infections in the studies was 050 (95 % CI: 035–069) in favour of vitamin Cgroups Accordingly, the results of the three studies suggest that vitamin C supplementationmay be beneficial for some of the subjects doing heavy exercise who have problems withfrequent upper respiratory infections

Cortisol response to exercise and post-exercise suppression of blood lymphocyte subset counts.

Abstract: This study examined a temporal relationship between exercise-induced changes in blood cortisol levels and circulating leukocyte and lymphocyte subset counts during and after exercise. Twenty-one young male, sedentary subjects [mean age, 20.8 +/- 2.4 (SD) yr; mean VO2max, 48.0 +/- 7.9 (SD) ml/kg/min] underwent a cycle ergometer exercise for 60 min at 60% VO2max. Peripheral blood samples, collected every 30 min during exercise and at 30, 60 min, 2.5 and 6 h of recovery, were used for the determination of serum cortisol and plasma catecholamines; lymphocyte subsets were analyzed by flow-cytometry. Based on the analysis of serum cortisol levels in response to exercise, the subjects can be identified as two groups: cortisol-responder (n = 13) and non-responder (n = 8) groups. Other than the cortisol response, the two groups showed no significant differences in terms of age, physical build, aerobic fitness, maximal heart rate, and pre-exercise blood leukocyte and lymphocyte subset counts. The two groups also did not differ significantly in their relative work rate and catecholamine response to the exercise. Both cortisol responder and non-responder groups displayed a granulocytosis, lymphocytosis and monocytosis during exercise, and a further granulocytosis after exercise. Changes in lymphocyte count and distribution during recovery, however, differed significantly between the two groups. In the circulation of the cortisol non-responder group, total lymphocyte counts returned to the baseline level shortly after exercise, whereas a significant lymphopenia occurred at 2.5 h of recovery in the cortisol responder group: the CD4+ cells showed the greatest decrease in cell count, followed by the CD8+ cells. In both groups, the CD16+ cell-counts tended to decline below the pre-exercise values at 30 and 60 min of recovery and returned to the baseline values by 2.5 h of recovery. The CD19+ cell-count was not suppressed in both groups after exercise. These results suggest that exercise-induced secretion of blood cortisol may contribute to post-exercise suppression of the helper- and cytotoxic-T cell counts, but does not seem to be involved in post-exercise changes in the NK-cell and B-cell counts as well as in post-exercise granulocytosis.

Variability in energy cost of running at the end of a triathlon and a marathon

Abstract: The aim of this study was to investigate the increase in energy cost of running occurring at the end of a triathlon and a marathon event and to link them to the metabolic and hormonal changes, as well as to variations in stride length. Seven subjects took part in 3 experimental situations: a 2 h 15 min triathlon (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 min marathon (MR) were the last 45 min were run at the same speed as the triathlon run (TR), and a 45 min isolated run (IR) done at triathlon speed. The results show that energy cost during MR was higher than during TR (p < 0.01) (+ 8.9%). Similar observations were made for pulmonary ventilation (+ 7.9%) and heart rate (+ 6.3%). Moreover, the values were significantly greater than the values obtained during the IR. TR and MR lead to greater weight loss (p < 0.01) (2.4 +/- 0.3 kg) than IR (1 +/- 0.2 kg). The triathlon and the marathon produced a large decrease in plasma volume (respectively 19.6 +/- 1.4% and 12.9 +/- 1.1%) compared to IR (2 +/- 0.4%). Plasma renin activity was higher for the triathlon and the marathon than for the IR (p < 0.01). MR produces a significantly greater increase in plasma free fatty acids (F.F.A.) than TR (p < 0.05) and IR (p < 0.01). In addition, the F.F.A. at the end of TR were significantly higher than IR (p < 0.05). At the end of the trial the mean stride lengths for TR and IR were greater (+ 15%) (p < 0.01) than for MR. This study, carried out with subjects running overground, confirms the decrease in running efficiency previously shown at the end of a laboratory triathlon, and demonstrates that this decrease is lower than that occurring during a marathon.

Thermal and Cardiovascular Strain from Hypohydration: Influence of Exercise Intensity.

Abstract: This study determined the effects of exercise intensity on the physiologic (thermal and cardiovascular) strain induced from hypohydration during heat stress. We hypothesized that the added thermal and cardiovascular strain induced by hypohydration would be greater during high intensity than low intensity exercise. Nine heat-acclimated men completed a matrix of nine trials: three exercise intensities, 25%, 45% and 65% VO2 max; and three hydration levels, euhydration and hypohydration at 3% and 5% body weight loss (BWL). During each trial, subjects attempted 50 min of treadmill exercise in a hot room (30 degrees C db, 50% rh) while body temperatures and cardiac output were measured. Hypohydration was achieved by exercise and fluid restriction the day preceding the trials. Core temperature increased (P<0.05) 0.12 degrees C per%BWL at each hypohydration level and was not affected by exercise intensity. Cardiac output was reduced (P<0.05) compared to euhydration levels and was reduced more during high compared to low intensity exercise after 5% BWL. It was concluded that: a) the thermal penalty (core temperature increase) accompanying hypohydration is not altered by exercise intensity; and b) at severe hypohydration levels, the cardiovascular penalty (cardiac output reduction) increases with exercise intensity.

Effects of eccentric-only resistance training and detraining

Abstract: The purposes of this investigation were to examine the effects of unilateral eccentric-only dynamic constant external resistance (DCER) training of the leg extensor muscles on: (a) eccentric DCER strength in the trained and untrained limbs, (b) concentric isokinetic leg extension peak torque-velocity curves in the trained and untrained limbs, and (c) retention of eccentric DCER strength and concentric isokinetic peak torque in the trained and untrained limbs following detraining. Seventeen adult male (X age +/- SD = 24 +/- 3 yr) volunteers comprised training (TR, n = 9) and control (CTL, n = 8) groups. The TR group trained the leg extensor muscles of the nondominant limb with eccentric-only DCER exercise (3 - 5 sets of 6 repetitions at 80% of the eccentric one-repetition maximum [1-RM] load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining, and after detraining for 1-RM unilateral eccentric DCER strength of the leg extensor muscles as well as concentric isokinetic leg extension peak torque at 1.05, 2.09, 3.14, 4.19, and 5.24 rad.s(-1) in both limbs. Mixed factorial ANOVAs, follow-ups, and post-hoc analyses indicated that the training resulted in increased eccentric DCER strength in both the trained (29 %) and untrained (17 %) limbs, but no change in isokinetic peak torque at any of the velocities of contraction in either limb. Furthermore, the training-induced increases in eccentric DCER strength for both limbs were retained across eight weeks of detraining.

The diagnostic validity of magnetic resonance imaging in acute knee injuries with hemarthrosis. A single-blinded evaluation in 69 patients using high-field MRI before arthroscopy.

Abstract: Sixty-nine patients with traumatic knee hemarthrosis were evaluated an average of 3 days after trauma by high field (1.5T) magnetic resonance imaging (MRI) using sagittal T1, T2-weighted and coronal 3D-gradient echo images. All knees were arthroscopically examined shortly afterwards. The diagnostic validity of MRI for intraarticular pathology was determined using arthroscopy as golden standard. All patients had pathological findings on arthroscopy. The injuries were sports-related in 77% of the cases. MRI was highly sensitive (86%) and specific (92%) for diagnosis of anterior cruciate ligament tears. Diagnosis of medial meniscal tears showed a 74% sensitivity and 66% specificity. MRI detected lateral meniscal tears in 50% with an 84% specificity. As such, MRI missed 10 significant meniscus ruptures requiring surgical treatment. The sensitivity for partial or total medial collateral ligament tears was 56%, the specificity 93%. Rupture of the medial retinaculum in cases with patellar dislocation or significant damage of articular cartilage were only detected by MRI in a few cases (27% and 20% sensitivity, respectively). MRIs low diagnostic validity for intraarticular pathology with hemarthrosis may be attributed to the shifting paramagnetic properties of the blood remains and catabolic processes in meniscal and chondral tissues during the hemoglobin degradation process. Accordingly, MRI, with the technique used, could neither replace arthroscopy in the diagnosis and screening of acute knee injuries, nor select patients with need for immediate arthroscopic meniscal surgery.

State anxiety following 20 minutes of bicycle ergometer exercise at selected intensities

Abstract: An attempt was made to determine if state anxiety responses following acute exercise are influenced by the intensity of exercise. Fifteen adults (5 female, 10 male) completed 20 minute sessions of bicycle ergometer exercise on separate days at intensities equal to 40, 60, or 70 % VO 2peak . Expired gas spirometry was employed to determine peak oxygen consumption and to control the workload during the submaximal protocols. State anxiety (STAI-Y1) was assessed prior to and following each exercise session, and 5, 60 and 120 minutes post-exercise. Repeated measures ANOVA revealed that state anxiety decreased (p < 0.05) following each exercise condition. POST HOC analysis indicated that state anxiety was significantly (p<0.05) reduced at all post-exercise assessments in the 40 and 60 % VO 2peak conditions. State anxiety was elevated by 3i.4 units at 5 minutes following exercise at 70 % VO 2 peak, but decreased (p < 0.05) below baseline at 60 and 120 minutes post-texercise to a degree not different from the other exercise conditions. Further analysis indicated the increase in anxiety 5 minutes following 70 % VO 2peak exercise was significant only in subjects with low baseline state anxiety values, whereas it was unchanged in subjects with higher baseline values. In conclusion, 20-rninute sessions of cycle ergometer exercise at intensities ranging from light to heavy were equally effective in reducing state anxiety in young, healthy adults. However, this reduction is delated somewhat following exercise at a high intensity (i.e., 70 % VO 2peak ).

Effects of hyperhydration on total body water, temperature regulation and performance of elite young soccer players in a warm climate.

Abstract: The purpose of this study was to test the effect of increased fluid intake on temperature regulation and performance in elite soccer players. Eight players of the Puerto Rico National Team were studied under field conditions at a Wet Bulb Globe Temperature (WBGT) heat stress index of 25.3 +/- 0.5 degrees C. They were young (17.0 +/- 0.6 yr) and well aerobically conditioned, as shown by their maximum aerobic power of 69.2 +/- 0.7 ml.kg(-1).min(-1). Players were randomly allocated to a week of voluntary hydration (VH) (fluid intake = 2.7 +/- 0.2.day(-1)) and a week of hyperhydration (HH) (fluid intake = 4.6 +/- 0.2.day(-1)) (p <0.05) prior to a soccer match. Their total body water (TBW) increased in HH compared to VH (p<0.05), despite a significant increase in urine output (p < 0.01). The soccer match was played at 82 +/- 7% (VH) and 83 +/- 6% (HH) of maximum heart rate. Sweat losses and core temperature increases during the match were similar in both hydration conditions. When the environmental conditions were taken into consideration, the increase in core temperature during the match rose, as a function of the heat stress index, only in VH (p < 0.05). Plasma volume was slightly reduced in both hydration conditions (ns). Performance assessment at the end of the soccer match revealed that average time to complete 7 repetitions of a soccer specific test was significantly increased (p < 0.05) after the match in both hydration conditions but showed no difference between them. Peak torque and fatigability of knee flexor and extensor muscle groups at 240 deg.sec(-1), measured on a Cybex 340 dynamometer were similar in both hydration conditions and not affected by the soccer match. The data suggest that additional water intake in these heat-acclimated players increased body water reserves and improved temperature regulation during a soccer match with no significant effect on the decrement in soccer specific performance observed at the end of a soccer match.

Lymphocyte, NK and LAK cell responses to maximal exercise.

Abstract: To evaluate if exhaustion after maximal exercise suppresses the immune system; ten healthy male oarsmen (maximal oxygen uptake, 5.7 +/- 0.2 l.min-1; mean and SE) performed a six minute "all-out" bout on a rowing ergometer (394 +/- 12 watt). Rowing increased the blood leucocyte count as reflected in the concentrations of lymphocytes, monocytes, and neutrophils. Two hours after rowing the leucocyte and neutrophil numbers remained elevated, while the lymphocyte count decreased below the prevalue. The concentrations of cluster designation CD3+ (pan T), CD4+ (T subset), CD8+ (T subset), CD19+ (B cells), and CD16+ natural killer (NK) cells increased during rowing with the elevation in CD16+ cells being sevenfold. Only the concentration of CD3+ and CD8+ cells decreased below prevalues two hours after exercise. The lymphokine activated killer (LAK) cell activity of blood mononuclear cells (BMNC), and the NK cell activity of BMNC (%lysis per fixed number of BMNC), either unstimulated or stimulated with interleukin-2, interferon-alfa or indomethacin, also increased in response to rowing, and returned to the prevalues after two hours. In contrast, the BMNC proliferative responses did not change significantly. The evaluation of NK and LAK cell activities, and the proliferative responses of BMNC suggest that six minute maximal exercise does not suppress the immune response during recovery, even when a large muscle mass is involved.

Effect of strength training on blood pressure measured in various conditions in sedentary men.

Abstract: To examine the effect of long term strength training on heart rate and blood pressure, measured in different conditions, and on their variability, thirty healthy, previously sedentary men were randomized into a training and a control group. The strength training program consisted of 48 training sessions on a multigym apparatus at a frequency of 3 sessions each week, involving leg press, bench press, leg curl, shoulder press, leg extension and sit ups. The control group was asked not to change their sedentary lifestyle. In the subjects of the training group the load could be increased significantly for all exercises (p < 0.01). Heart rate and blood pressure were measured at rest in the supine and sitting position, during 24 hours with a non-invasive ambulatory device and during an exercise test on a cycloergometer. Repeated measures analysis of variance did not show an effect of strength training on heart rate or on blood pressure. In addition, power spectral analysis of the RR interval (ECG) and of the beat-to-beat blood pressure in the supine subject revealed similar total, low frequency and high frequency power before and after training, indicating that the neural control of both heart rate and blood pressure was not affected by a 16-week program of strength training.

Force development of dynamic and static contractions in children and adults

Abstract: There are still unclarified points remaining in regard to the characteristics of force development in children who are immature in their basic activities in daily living Moreover, there are morphological, histological, and biochemical differences between immature and mature muscles In the present study, dynamic elbow flexion and static contractions which were performed by elbow flexors with maximum effort were examined by force-velocity and force-time relationships and electromyograms (EMG) in six-year-old children and in adults In dynamic contractions with various loads, the force-velocity relationship for children was (P + 565) (v + 148) = 1951, and (P + 1465) (v + 226) = 9621 for adults The maximum power in children and adults was 228 watts and 1608 watts, respectively The contraction delay in children was greater than that in adults for every relative load In static contractions, the maximum rate of force development for children was significantly lower than that for adults at each pre-tension With an increase in pre-tension, the adult rate showed a tendency to decrease, whereas the rate for children showed no change The electromechanical delay observed in children was significantly greater than that in adults For dynamic and static contractions, the contractile speed in children was lower than that in adults

Long-term results after arthroscopic meniscectomy. The role of preexisting cartilage fibrillation in a 13 year follow-up of 60 patients.

Abstract: Sixty patients with stable knees and arthroscopic menisectomy were matched into two groups according to the presence of early degenerative changes at the operation. Patients with severe cartilage changes were excluded. The patients were between 20 and 40 years of age at the operation and no patient had previous surgery on the involved knee. The intraarticular findings were documented at surgery and the patients were re-examined 12 to 15 years after the meniscectomy. Pre-existing cartilage fibrillation at the meniscectomy did not seem to influence the long-term results. At the follow-up no difference was found between the groups at the physical examination, in subjective complaints, in knee function and activity or in radiographic findings. In the total group 62% had early signs of arthrosis (Fairbank changes) and 42% narrowing of the joint space (Ahlback grade 1-2) in the operated knee. No one had more severe changes. Radiographic signs of arthrosis were 4 times commoner in the operated knee compared to the non-operated knee after partial meniscectomy and 7 times commoner in the operated knee after subtotal meniscectomy. Arthrosis at the follow-up was seen three times more often in patients older than 30 years of age at surgery than in younger patients. The functional outcome was good and 70% were still active in sports compared to 90% before the operation.

Reliability and validity of the maximal anaerobic running test

Abstract: Physically active men (n = 13) twice performed the Maximal Anaerobic Running Test (MART) on a treadmill and once the Wingate Anaerobic Test (WAnT) on a cycle ergometer. The MART consisted of n 20-s runs with 100-s recovery between the runs. The speed of the first run was 14.6 km.h-1 and the inclination 4 degrees. Thereafter, the speed was increased by 1.37 km.h-1 every run until exhaustion. During all tests oxygen uptake was measured breath-by-breath and blood samples were taken from the fingertip 40s after each run to determine the lactate concentration (BLa). Power at submaximal BLa levels and maximal power (P5mM, P10mM and Pmax, respectively) were calculated and P was expressed as the oxygen demand of running according to the American College of Sports Medicine equation. In the MART the Pmax was 108 ml.kg-1.min-1 and peak BLa was 15.6 mM. The reliability for the power indices in the MART were as follows: r = 0.92 (p < 0.001) for Pmax r = 0.80 (p < 0.001) for P10mM and r = 0.67 (p = 0.01) for P5mM. The average contribution of anaerobic energy expenditure was calculated to be 68% but it ranged from 64% to 72% during the MART. Although four out of seven of the correlations between the corresponding variables of the MART and WAnT were significant (0.52 < r < 0.59) they were not high. It is concluded that the anaerobic energy production is high in the MART, the test is reliable, and that the treadmill and cycle ergometer test measure slightly different qualities.