Biocompatible Composite Materials Based on Porous Hydroxyapatite Ceramics and Copolymer of Lactide and Glycolide.

The intensive development of reconstructive surgery and traumatology provides a stable demand for new materials for implants. Of particular interest are materials based on hydroxyapatite, which are chemically close to the elemental composition and structure of bone and have similar bioactive properties. The aim of this work was to obtain porous composite materials based on hydroxyapatite and a copolymer of lactide and glycolide with properties suitable for use as a material for bone implants. The phase and elemental composition of composites was investigated by infrared spectroscopy, X-ray diffraction, and X-ray photoelectronic spectroscopy methods, and it was established how the production process affects the composition of materials. Regularities of the formation of porosity by the methods of low-temperature adsorption of nitrogen, immersion in a liquid (determination of the pore space volume), measurement of the diffusion coefficient through the material (Franz cell), and surface properties of composite materials by the Hammett indicator method, by the lying drop method were revealed. Regularities were established between the surface properties and the composition of materials and their biocompatibility determined using monocytes isolated from human peripheral blood.

Lipid profiles of persons with paraplegia and tetraplegia: sex differences.

BACKGROUND/OBJECTIVE: To examine the lipoprotein profiles of men and women with paraplegia and tetraplegia. Impairment of the sympathetic nervous system (dependent on the level of injury) and the extent of physical capacity and activity were correlated with the lipid profile in men with spinal cord injury (SCI). Sex-related differences of the lipoprotein profiles could be found in nondisabled and premenopausal women with SCI mainly because of the different effects of sexual hormones. METHODS: Lipoprotein profiles of 112 participants with SCI (32 premenopausal women, 80 men) were analyzed and correlated to sex, lesion level, and physical performance capacity. RESULTS: Women with tetraplegia or paraplegia showed significantly higher levels of high-density lipoprotein and lower ratios of total cholesterol to high-density lipoprotein-cholesterol compared with men with corresponding lesion levels, without a difference in peak oxygen consumption. Concentrations of very-low-density lipoproteins were lower in women with paraplegia than in men with paraplegia; no differences were found in total cholesterol, low-density lipoprotein-cholesterol, and triglycerides. Sex-independent elevations in total cholesterol and low-density lipoprotein-cholesterol were associated with paraplegia, and sex-independent elevations in triglyceride levels were associated with tetraplegia. CONCLUSIONS: Persons with SCI showed sex-related differences in their lipoprotein profiles. Independent of physical fitness, the lipoprotein profile of premenopausal women with SCI did not exhibit the adverse lipoprotein characteristics observed in men with SCI, probably because of the influence of sexual hormones independent of lesion level.

Magnetic resonance imaging of the lumbar spine and blood volume in professional cyclists.

Stimulated hematopoiesis is observed in the bone marrow of endurance-trained athletes by magnetic resonance imaging (MRI) independent of the hemoglobin concentration (hematocrit or erythrocyte count) or circulating reticulocytes, but may be related to blood volume (BV). This study determined whether hyperplasia of hematopoietic bone marrow of professional cyclists correlates with their red cell volume (RCV). Twelve male professional cyclists (mean +/- SD; 20.2 +/- 1.4 years, 69.0 +/- 4.5 kg, VO2max 64.4 +/- 4.6 ml/min/kg, BV 7257 +/- 884 ml, RCV 2990 +/- 299 g) completed an MRI of the lumbar spine, a total BV determination using a CO-rebreathing method and a graded exercise testing within two consecutive days. Significant correlations were found between performance and BV data. A significant correlation existed also between the signal intensity of the Turbo inversion-recovery sequence with short inversion time (Turbo-STIR) and BV (r (2) = 0.47, P < 0.05), RCV (r (2) = 0.56, P < 0.05) and plasma volume (r (2) = 0.39, P < 0.05) per kilogram body mass. The present study provides evidence of stimulated erythropoiesis with hyperplasia of the hematopoietic bone marrow of endurance athletes explaining their large RCV.

Cycling power output produced during flat and mountain stages in the Giro d'Italia: a case study.

Until recently, the physiological demands of cycling competitions were mostly reflected by the measurement of heart rate and the indirect estimation of exercise intensity. The purpose of this case study was to illustrate the varying power output of a professional cyclist during flat and mountain stages of a Grand Tour (Giro d'Italia). Nine stage recordings of a cyclist of the 2005 Giro d'Italia were monitored using a mobile power measurement device (SRM Trainingssystem, Julich, Germany), which recorded direct power output and heart rate. Stages were categorized into flat (n = 5) and mountain stages (n = 4). Data were processed electronically, and the overall mean power in flat and mountain stages and maximal mean power for various durations were calculated. Mean power output was 132 W +/- 26 (2.0 W x kg(-1) +/- 0.4) for the flat and 235 W +/- 10 (3.5 W x kg(-1) +/- 0.1) for the mountain stages. Mountain stages showed higher maximal mean power (367 W) for longer durations (1800 s) than flat stages (239 W). Flat stages are characterized by a large variability of power output with short bursts of high power and long periods with reduced intensity of exercise, whereas mountain stages mostly require submaximal, constant power output over longer periods.

[Cardiovascular preparticipation screening of competitive athletes]. / Die kardiovaskuläre Voruntersuchung im Wettkampfsport.

Cardiovascular deaths during or following sport activities repeatedly raise the question about a practicable preparticipation screening for athletes to prevent such adverse events. In Germany and most European countries, well-equipped sports medicine centers evaluate the health of the Olympic athletes through regular checkups, which include a detailed medical history and thorough physical examination as well as an ECG at rest, a stress ECG, and an echocardiography. In professional sports, guidelines for this screening differ according to the federations, however, most of them intend to follow the recommendations of the Olympic sports system. For nonprofessional competitive sports, there are no guidelines for preparticipation screening, although these athletes train at the same level of intensity as professional athletes. The main issue in this international debate is the question of cost-effectiveness and how to finance preventive measures.

Effect of manual lymph drainage on the course of serum levels of muscle enzymes after treadmill exercise.

OBJECTIVE: Improving muscular recovery after exercise is an important topic in sports medicine. The aim of the present study was to evaluate the effect of manual lymph drainage on the course of serum levels of muscle enzymes after an extended treadmill exercise. DESIGN: Fourteen recreational athletes (seven women, seven men) were included in the study. The participants underwent a graded exercise test on a treadmill ergometer to determine the individual anaerobic threshold (IAT). Seven days after the graded exercise test, all subjects performed 30 mins of treadmill exercise at an intensity equivalent to IAT. The subjects were randomized into two groups of seven persons. One group was treated with manual lymph drainage (ML), whereas the control group (CG) received no treatment after the endurance exercise at IAT level. RESULTS: After an increase immediately after exercise, a fast decrease in lactate dehydrogenase (LDH) and in aspartate aminotransferase (AST) concentration was observed, with significantly lower values for LDH after 48 hrs in the subjects having received lymph drainage treatment. The course of creatine kinase (CK) levels was comparable, but did not reach significance. CONCLUSION: Manual lymph drainage after treadmill exercise was associated with a faster decrease in serum levels of muscle enzymes. This may indicate improved regenerative processes related to structural damage of muscle cell integrity.

Power output during stage racing in professional road cycling.

PURPOSE: The aim of the study was to evaluate the power output during a multistage professional road race using direct power measurements and to compare these results with the performance measurements using competition heart rate recordings. METHODS: Six professional road cyclists performed an incremental cycling test during which peak power output, power output, and heart rate at the lactate threshold (LT) and at a lactate increase of 1 mM above the LT (LT + 1) were assessed. During a six-stage road race competition, power output was measured directly (SRM crankset). To analyze the time spent at different intensities during competition, the amount of competition time spent below LT (zone 1), between the LT and LT + 1 (zone 2), and above LT + 1 (zone 3) determined during laboratory testing were calculated for power output and heart rate. RESULTS: During the five mass start stages, a mean power output of 220 +/- 22 W (3.1 +/- 0.2 W x kg(-1)) with a mean heart rate of 142 +/- 5 bpm was measured. Average power output during an uphill time trial was 392 +/- 60 W (5.5 +/- 0.4 W x kg(-1)) with a mean heart rate of 169 +/- 3 bpm. For the mass start stages, the average distribution of exercise time spent in different intensities calculated for power output and heart rate was 58 versus 38% for zone 1, 14 versus 38% for zone 2, and 28 versus 24% for zone 3. CONCLUSION: Most of the competition time during the mass start stages was spent at intensities near the LT. Compared with power output, heart rate measurement underestimated the time spent at intensity zones 1 and 3, and overestimated the time spent in zone 2.

Myocardial stress after competitive exercise in professional road cyclists.

PURPOSE: Based on the determination of cardiac troponin (cTnT), brain natriuretic peptide (BNP), and echocardiographic measurements, recent investigations have reported myocardial damage and reversible cardiac dysfunction after prolonged endurance exercise in apparently healthy subjects. In the present study, we investigated the myocardial stress reaction in professional endurance athletes after strenuous competitive physical exercise. METHODS: Eleven highly trained male professional road cyclists (age 27 +/- 4 yr; .VO2peak 67 +/- 5 mL.kg-1.min-1; training workload 34,000 +/- 2,500 km.yr-1) were examined. The following parameters were determined before and after one stage of a 5-d professional cycling race: BNP, cTnT (third-generation assay that shows no cross reactivity with skeletal TnT), creatine kinase (CK), creatine kinase MB (CKMB), myoglobin (Myo), and urea. All participants were submitted to a careful cardiac examination including echocardiography and stress ECG. RESULTS: None of the athletes showed pathological findings in the cardiac examination. CK (P < 0.01), CKMB (P < 0.05), and Myo (P < 0.01) were increased after the race. Normal postexercise cTnT levels indicate that the increase in CK, CKMB, and Myo was of noncardiac origin. In contrast, BNP rose significantly from 47.5 +/- 37.5 to 75.3 +/- 55.3 pg.mL-1 (P < 0.01). Pre- and postexercise values of BNP as well as the individual exercise-induced increase in BNP were significantly correlated with age (R2 = 0.68, R2 = 0.66, and R2 = 0.58, respectively; P < 0.05). CONCLUSION: Strenuous endurance exercise in professional road cyclists does not result in structural myocardial damage. The rise in BNP in older athletes may reflect a reversible, mainly diastolic left ventricular dysfunction. This needs to be confirmed by larger trials including different intensities, sports, and age groups.

Characterization of hematopoietic bone marrow in male professional cyclists by magnetic resonance imaging of the lumbar spine.

PURPOSE: To prospectively evaluate hematopoietic bone marrow of male professional cyclists in relation to performance data and laboratory data, and in comparison to age-matched healthy volunteers. MATERIALS AND METHODS: Twenty male cyclists and 44 volunteers (27 males and 17 females) were prospectively studied by magnetic resonance imaging (MRI) at high-field strength. A sagittal T1-weighted (T1-w) spin-echo (SE) sequence, a gradient-echo (GE) sequence with an echo time (TE) for out-of-phase (OOP) imaging, and a turbo inversion-recovery sequence with short inversion time (TIRM) for fat suppression was used. The averaged bone marrow signal intensity (SI) of three adjacent vertebrae was related to the signal of an adjacent nondegenerative disk. RESULTS: The cyclists revealed a significantly different SI as compared to male volunteers in the OOP (0.34 +/- 0.14 vs. 0.28 +/- 0.09, P < 0.05) and T1-w sequences (1.62 +/- 0.19 vs. 1.77 +/- 0.30, P < 0.05). Only in TIRM was there a significant difference compared to female volunteers (0.36 +/- 0.08 vs. 0.44 +/- 0.04, P < 0.01). MRI data of cyclists did not correlate to hemoglobin, erythrocyte, or reticulocyte counts; ferritin, relative heart volume, relative maximal power (rPmax; W/kg bw), or relative maximal oxygen consumption (VO(2)max). A borderline linear correlation was found for hematocrit (OOP: r = 0.42, P = 0.06; TIRM: r = 0.44, P = 0.06). CONCLUSION: Bone marrow hyperplasia is observed in male professional cyclists in the axial skeleton. The MR findings are probably independent of mechanically induced marrow edema. A multifactorial cause must be considered, as single laboratory and performance data did not appear to contribute significantly to these results.