Variation in the determinants of power of chemically skinned type I rat soleus muscle fibres.

We explored to which extent maximal velocity of shortening (Vmax), force per cross-sectional area (specific tension, Po) and curvature of the force-velocity relationship (a/Po in the Hill equation) contribute to differences in peak power of single, chemically skinned rat type I fibres. Force-velocity relationships were determined from isotonic contractions of 94 maximally activated fibres. Peak power (±SD) was 3.50±1.64 WL(-1). There was a tenfold range of peak power and five-, six- and fourfold ranges for Po, Vmax and a/Po, respectively. None of the differences between fibres was explicable by differences in myosin heavy or light chain composition. The inverse relationship between a/Po and Vmax suggests a similar underlying cause. Fitting the data to the Huxley (Progr Biophys Biophys Chem 7:255-318, 1957) cross-bridge model showed that the rate constant g (2) and the sum of the rate constants (f+g(1)) co-varied, both being low in the slowest fibres. Approximately 16% of the variation in Po could be explained by variation in the proportion of attached cycling cross-bridges (f/(f+g(1))), but the origin of most of the variance in Po remains unknown.

Patellar tendinopathy in master track and field athletes: influence of impact profile, weight, height, age and gender.

PURPOSE: Patellar tendinopathy causes significant morbidity in professional and recreational athletes. Despite the relevance of the problem, its causative factors remain poorly understood. The purpose of this cross-sectional study is to evaluate the influence of age, gender, weight, height and impact profile on developing patellar tendinopathy in master track and field athletes. METHODS: During the European Veterans Athletics Championships in Poznan in July 2006, 174 athletes (103 men and 71 women; mean age: 53.8 (SD 11.4) years, range 35-82 years) were evaluated with the VISA-P questionnaire. A fully trained orthopaedic surgeon made a diagnosis of patellar tendinopathy according to clinical criteria. RESULTS: There was no effect of gender upon the presence of patellar tendinopathy (n.s.). No significant track and field specialty effect upon the frequency of patellar tendinopathy was found on the VISA-P questionnaire scores. There was no effect of track and field specialty on the VISA-P score. No evidence of a statistically significant association was found between age and VISA-P score (n.s.). There was no statistically significant difference in either prevalence of patellar tendinopathy or VISA-P score between high-impact and low-impact athletes (n.s.). CONCLUSION: In master track and field athletes, impact profile, weight, height, age and gender did not exert any influence on developing patellar tendinopathy.

Changes in contractile properties of skinned single rat soleus and diaphragm fibres after chronic hypoxia.

Hypoxia may be one of the factors underlying muscle dysfunction during ageing and chronic lung and heart failure. Here we tested the hypothesis that chronic hypoxia per se affects contractile properties of single fibres of the soleus and diaphragm muscle. To do this, the force-velocity relationship, rate of force redevelopment and calcium sensitivity of single skinned fibres from normoxic rats and rats exposed to 4 weeks of hypobaric hypoxia (410 mmHg) were investigated. The reduction in maximal force (P(0)) after hypoxia (p=0.031) was more pronounced in type IIa than type I fibres and was mainly attributable to a reduction in fibre cross-sectional area (p=0.044). In type IIa fibres this was aggravated by a reduction in specific tension (p=0.001). The maximal velocity of shortening (V (max)) and shape of the force velocity relation (a/P(0)), however, did not differ between normoxic and hypoxic muscle fibres and the reduction in maximal power of hypoxic fibres (p=0.012) was mainly due to a reduction in P(0). In conclusion, chronic hypoxia causes muscle fibre dysfunction which is not only due to a loss of muscle mass, but also to a diminished force generating capacity of the remaining contractile material. These effects are similar in the soleus and diaphragm muscle, but more pronounced in type IIa than I fibres.

Forearm and tibial bone measures of distance- and sprint-trained master cyclists.

PURPOSE: Cycling is very popular; however, it is often believed to be associated with below average bone mass. This study compared bone measures of sprint- and distance-trained cyclists competing at World Master Track Championships, along with sedentary controls (30-82 yr), and examined the associations of bone measures with age. METHODS: Radius and tibia epiphyseal and shaft bone mineral density (BMD), bone mineral content (BMC), and cross-sectional area along with shaft polar moment of resistance (RPol) and endocortical/periosteal circumferences were assessed by peripheral quantitative computed tomography. Intergroup differences were assessed by ANOVA and age relationships by correlation analyses. RESULTS: Sprint cyclists had the largest bone shafts and bone strength surrogates; the difference in diaphyseal BMC, area, and RPol compared with controls being >or=10% in the tibia and >or=8% in the radius (P < 0.01). Distance cyclists versus control group differences were smaller (tibia: approximately 4-10%; radius: <2%), reaching statistical significance only for tibial BMC and area (P < 0.05). Generally, epiphyseal bone measures showed no group differences. In the radius, age correlations were negative for both the sprinters' and the controls' diaphyseal and the sprinters' epiphyseal BMD; they were positive for the controls' diaphyseal endocortical and periosteal circumferences (P < 0.05). In the cyclists' tibiae, neither epiphyseal nor diaphyseal bone measures were correlated with age. CONCLUSIONS: Sprint cyclists and to a lesser extent distance cyclists had greater tibia and radius bone strength surrogates than the controls, with tibial bone measures being well preserved with age in all groups. This suggests that competition-based cycling and the associated training regime is beneficial in preserving average or above-average bone strength surrogates into old age in men.

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 Poznan, 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.