Joern Rittweger

No influence of age, gender, weight, height, and impact profile in achilles tendinopathy in masters track and field athletes.

Background Achilles tendinopathy is commonly reported by athletes involved in activities that include running and jumping. Despite the prevalence of the problem, causative factors in Achilles tendinopathy remain poorly understood. Hypothesis In Masters track and field athletes, there is no influence of age, gender, weight, height, and impact profile in developing Achilles tendinopathy. Study Design Cross-sectional study; Level of evidence, 3. Methods During the European Veterans Athletics Championships in Poznań, Poland, in July 2006, 178 athletes (110 men and 68 women; mean age, 54.1 years; range, 35-94 years) were evaluated with the Victorian Institute of Sport Assessment—Achilles (VISA-A) questionnaire. A fully trained orthopaedic surgeon made a diagnosis of Achilles tendinopathy according to clinical criteria. Results There was no effect of gender on the presence of Achilles tendinopathy (P = .14). No significant track and field specialty effect upon the frequency of Achilles tendinopathy was found on the VISA-A questionnaire scores (P = .32). Equally, there was no effect of track and field specialty on the VISA-A score (P = .31). No correlation was found between age and VISA-A score (P = .36). There was no statistically significant difference in either prevalence of Achilles tendinopathy or VISA-A score between high-impact and low-impact athletes (P = .19 and P = .31, respectively). Conclusion In competing Masters track and field athletes, we did not find any influence of age, gender, weight, height, or impact profile on the development of Achilles tendinopathy. Additional research is required to improve our understanding of the causative factors in Achilles tendinopathy.

Adaptive response of human tendon to paralysis

To gain insight into the adaptive response of human tendon to paralysis, we compared the mechanical properties of the in vivo patellar tendon in six men who were spinal cord–injured (SCI) and eight age‐matched, able‐bodied men. Measurements were taken by combining dynamometry, electrical stimulation, and ultrasonography. Tendon stiffness and Youngs modulus, calculated from force–elongation and stress–strain curves, respectively, were lower by 77% (P < 0.01) and 59% (P < 0.05) in the SCI than able‐bodied subjects. The cross‐sectional area (CSA) of the tendon was 17% smaller (P < 0.05) in the SCI subjects, but there was no difference in tendon length between the two groups. Our results indicate that paralysis causes substantial deterioration of the structural and material properties of tendon. This needs to be taken into consideration in the design of electrical stimulation protocols for rehabilitation and experimental purposes, and when interpreting changes in the contractile speed of paralyzed muscle. Muscle Nerve, 2005

Influence of recombinant human erythropoietin treatment on pulmonary O2 uptake kinetics during exercise in humans

We hypothesized that 4 weeks of recombinant human erythropoietin (RhEPO) treatment would result in a significant increase in haemoglobin concentration ([Hb]) and arterial blood O2‐carrying capacity and that this would (1) increase peak pulmonary oxygen uptake during ramp incremental exercise, and (2) speed kinetics during ‘severe’‐, but not ‘moderate’‐ or ‘heavy’‐intensity, step exercise. Fifteen subjects (mean ±s.d. age 25 ± 4 years) were randomly assigned to either an experimental group which received a weekly subcutaneous injection of RhEPO (150 IU kg−1; n= 8), or a control group (CON) which received a weekly subcutaneous injection of sterile saline (10 ml; n= 7) as a placebo, for four weeks. The subjects and the principal researchers were both blind with respect to the group assignment. Before and after the intervention period, all subjects completed a ramp test for determination of the gas exchange threshold (GET) and , and a number of identical ‘step’ transitions from ‘unloaded’ cycling to work rates requiring 80% GET (moderate), 70% of the difference between the GET and (heavy), and 105% (severe) as determined from the initial ramp test. Pulmonary gas exchange was measured breath‐by‐breath. There were no significant differences between the RhEPO and CON groups for any of the measurements of interest ([Hb], kinetics) before the intervention. Four weeks of RhEPO treatment resulted in a 7% increase both in [Hb] (from 15.8 ± 1.0 to 16.9 ± 0.7 g dl−1; P < 0.01) and (from 47.5 ± 4.2 to 50.8 ± 10.7 ml kg−1·min−1; P < 0.05), with no significant change in CON. RhEPO had no significant effect on kinetics for moderate (Phase II time constant, from 28 ± 8 to 28 ± 7 s), heavy (from 37 ± 12 to 35 ± 11 s), or severe (from 33 ± 15 to 35 ± 15 s) step exercise. Our results indicate that enhancing blood O2‐carrying capacity and thus the potential for muscle O2 delivery with RhEPO treatment enhanced the peak but did not influence kinetics, suggesting that the latter is principally regulated by intracellular (metabolic) factors, even during exercise where the requirement is greater than the , at least in young subjects performing upright cycle exercise.

Habitual levels of high, but not moderate or low, impact activity are positively related to hip BMD and geometry: Results from a population‐based study of adolescents

Whether a certain level of impact needs to be exceeded for physical activity (PA) to benefit bone accrual is currently unclear. To examine this question, we performed a cross‐sectional analysis between PA and hip BMD in 724 adolescents (292 boys, mean 17.7 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC), partitioning outputs from a Newtest accelerometer into six different impact bands. Counts within 2.1 to 3.1g, 3.1 to 4.2g, 4.2 to 5.1g, and >5.1g bands were positively related to femoral neck (FN) BMD, in boys and girls combined, in our minimally adjusted model including age, height, and sex (0.5–1.1g: beta = −0.007, p = 0.8; 1.1–2.1g: beta = 0.003, p = 0.9; 2.1–3.1g: beta = 0.042, p = 0.08; 3.1–4.2g: beta = 0.058, p = 0.009; 4.2–5.1g: beta = 0.070, p = 0.001; >5.1g: beta = 0.080, p < 0.001) (beta = SD change per doubling in activity). Similar positive relationships were observed between high‐impact bands and BMD at other hip sites (wards triangle, total hip), hip structure indices derived by hip structural analysis of dual‐energy X‐ray absorptiometry (DXA) scans (FN width, cross‐sectional area, cortical thickness), and predicted strength (cross‐sectional moment of inertia). In analyses where adjacent bands were combined and then adjusted for other impacts, high impacts (>4.2g) were positively related to FN BMD, whereas, if anything, moderate (2.1–4.2g) and low impacts (0.5–2.1g) were inversely related (low: beta = −0.052, p = 0.2; medium: beta = −0.058, p = 0.2; high: beta = 0.137, p < 0.001). Though slightly attenuated, the positive association between PA and FN BMD, confined to high impacts, was still observed after adjustment for fat mass, lean mass, and socioeconomic position (high: beta = 0.096, p = 0.016). These results suggest that PA associated with impacts >4.2g, such as jumping and running (which further studies suggested requires speeds >10 km/h) is positively related to hip BMD and structure in adolescents, whereas moderate impact activity (eg, jogging) is of little benefit. Hence, PA may only strengthen lower limb bones in adolescents, and possibly adults, if this comprises high‐impact activity.

Greater loss in muscle mass and function but smaller metabolic alterations in older compared with younger men following 2 wk of bed rest and recovery.

This investigation aimed to compare the response of young and older adult men to bed rest (BR) and subsequent rehabilitation (R). Sixteen older (OM, age 55-65 yr) and seven young (YM, age 18-30 yr) men were exposed to a 14-day period of BR followed by 14 days of R. Quadriceps muscle volume (QVOL), force (QF), and explosive power (QP) of leg extensors; single-fiber isometric force (Fo); peak aerobic power (V̇o2peak); gait stride length; and three metabolic parameters, Matsuda index of insulin sensitivity, postprandial lipid curve, and homocysteine plasma level, were measured before and after BR and after R. Following BR, QVOL was smaller in OM (-8.3%) than in YM (-5.7%,P= 0.031); QF (-13.2%,P= 0.001), QP (-12.3%,P= 0.001), and gait stride length (-9.9%,P= 0.002) were smaller only in OM. Fo was significantly smaller in both YM (-32.0%) and OM (-16.4%) without significant differences between groups. V̇o2peakdecreased more in OM (-15.3%) than in YM (-7.6%,P< 0.001). Instead, the Matsuda index fell to a greater extent in YM than in OM (-46.0% vs. -19.8%, respectively,P= 0.003), whereas increases in postprandial lipid curve (+47.2%,P= 0.013) and homocysteine concentration (+26.3%,P= 0.027) were observed only in YM. Importantly, after R, the recovery of several parameters, among them QVOL, QP, and V̇o2peak, was not complete in OM, whereas Fo did not recover in either age group. The results show that the effect of inactivity on muscle mass and function is greater in OM, whereas metabolic alterations are greater in YM. Furthermore, these findings show that the recovery of preinactivity conditions is slower in OM.

Bone geometry and volumetric bone mineral density in girls with Turner syndrome of different pubertal stages

Objective  An increased rate of fractures has been reported in patients with Turner syndrome (TS). We aimed to assess bone geometry and volumetric bone mineral density (vBMD) at the radius in girls with TS and to evaluate the relationships between bone parameters and fracture history.

Variation in the determinants of power of chemically skinned human muscle fibres

We have explored the extent to which the maximal velocity of unloaded shortening (Vmax), the force generated per unit cross‐sectional area (P0) and the curvature of the force–velocity relationship (a/P0 in the Hill equation) contribute to differences in peak power of chemically skinned single fibres from the quadriceps muscle of healthy young male subjects. The analysis was restricted to type I and IIA fibres that contained a single type of myosin heavy chain on electrophoretic separation. Force–velocity relationships were determined from isotonic contractions of maximally activated fibres at 15°C. Mean (±s.d.) peak powers were 1.99 ± 0.72 watts per litre (W L−1) for type I fibres and 6.92 ± 2.41 W L−1, for type IIA fibres. The most notable feature, however, was the very large, sevenfold, range of power outputs within a single fibre type. This wide range was a consequence of variations in each of the three components determining power: P0, Vmax and a/P0. Within a single fibre type, P0 varied threefold, and Vmax and a/P0 two‐ to threefold. There were no obvious relationships between P0 and Vmax or between P0 and a/P0. However, there was a suggestion of an inverse relationship between a/P0 and Vmax, the effect being to reduce, somewhat, the impact of differences in Vmax on peak power. In searching for the causes of variation in peak power of fibres of the same type, it appears likely that there are two factors, one that affects P0 and another that leads to variation in both Vmax and a/P0.

Updates on improvement of human athletic performance: focus on world records in athletics

INTRODUCTION Progression of world records (WRs) in athletics is a reliable mean to assess the potentiality of the human body, which also reflects how society has evolved over time and will continue to evolve. We conducted a quantitative analysis of WRs in measurable Olympic events from nine representative disciplines (100, 400, 1500, 10,000 m, marathon, long jump, high jump, shot put and javelin throw) in order to identify progression and trends. SOURCES OF DATA Data were gathered for the years 1900-2007 from the database of the International Olympic Committee. AREAS OF AGREEMENT Overall, the relative improvement of athletic performance was higher in women than in men, being nearly doubled across the different specialities. The biggest increases were observed for javelin throw and shot put, in both men and women, respectively. Conversely, the improvement in race time was directly related to the race distance. We also observed a consistent significant linear model of WRs progression in time, although the improvement has substantially stopped or reached a plateau in several specialities. GROWING POINTS The observed trend might be explained by a variety of factors, including social and environmental changes, natural selection, advances in training and sport physiology, ergogenic aids and, possibly, doping. EMERGING AREAS FOR DEVELOPING RESEARCH These results are discussed in a multifaceted approach, taking into account several biological, environmental and technological issues that might explain the trends observed.

Knee extensor fatigability after bedrest for 8 weeks with and without countermeasure

We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness of resistive vibration exercise to counteract these changes. Changes in knee extensor fatigability as a consequence of 8 weeks of horizontal bedrest with or without daily resistive vibration exercise were evaluated in 17 healthy male volunteers. Bedrest increased fatigability (% decrease in maximal voluntary isometric torque per minute exercise) from −7.2 ± 0.5 to −10.2 ± 1.0%/min (P < 0.05), which was accompanied by a decline (of 52.0 ± 3.7%, P < 0.05) in muscle blood flow. Daily resistive vibration exercise training during bedrest prevented increases in fatigability (from −10.8 ± 1.8 to −8.4 ± 1.6%/min, P < 0.05), and mitigated the reduction in blood flow (decline of 26.1 ± 5.1%, P < 0.05). Daily resistive exercise may thus be suggested as an effective countermeasure during spaceflight and illness‐related prolonged bedrest to combat the detrimental changes in muscle endurance that result from gravitational unloading. Muscle Nerve, 2007

Traumatic patellar tendinopathy.

Purpose. In patellar tendinopathy, there is anterior knee pain with tenderness of the attachment of the patellar tendon over the lower pole of the patella. The condition is commonly associated with athletic overuse, but we have encountered it in some patients following direct blunt trauma to the anterior aspect of the knee. We describe the history and management of patients with traumatic patellar tendinopathy. Method. Between April 2000 and August 2006, we managed eight otherwise healthy well trained athletes who developed signs and symptoms compatible with classical patellar tendinopathy after a direct trauma to the anterior aspect of the patellar tendon during sport activity. Results. The clinical diagnosis of patellar tendinopathy was confirmed clinically and at imaging by MRI and ultrasound scans. Patients responded to conservative or surgical management, in the same way as patellar tendinopathy secondary to overuse. Conclusion. A single direct traumatic event can lead to chronic tendon problems. Hence, in addition to overuse injury, patellar tendinopathy can follow a direct trauma and exhibit the same clinical features. Further research is required to better understand the pathophysiology of the clinical condition.