The effects of chronic concentric and eccentric training on position sense and joint reaction angle of the knee extensors.

The aim of the present study was to compare the effect of chronic concentric or eccentric training on position sense and joint reaction angle, in healthy, untrained young men. Twenty-four men were randomly assigned into a pure concentric (CT) or a pure eccentric (ET) group and performed for 8 weeks, one training session/week, 75 maximal knee extensors contractions. Before and 48 h after the first (W1) and the last (W8) training sessions, knee joint position sense and joint reaction angle were assessed at three different knee angles (i.e. 30°, 45° and 60°). At the same time points, indirect indices of exercise-induced muscle damage (EIMD) were evaluated (i.e. range of motion [ROM], optimal angle, maximum isometric, concentric and eccentric torques, delayed onset muscle soreness [DOMS] and blood creatine kinase concentrations [CK]). Forty-eight hours post W1, position sense, reaction angle and all EIMD indices were significantly changed for both groups (p < 0.05; η2: 0.125-0.618), however, greater alterations were observed after ET. Significant correlations were found, in both groups, between the training-induced changes of position sense, reaction angles and the changes of EIMD biomarkers (r: -0.855-0.825; p < 0.005). No significant changes were found 48 h post W8 for position sense, reaction angle and EIMD indices (p > 0.285) for both CT or ET groups. In conclusion, exercise-induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se.HighlightsExercise induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se.After the 1st training session eccentric exercise caused greater disturbances, compared to concentric exercise, in EIMD indices which caused concomitant disturbances to position sense and knee reaction angle.8 weeks of either eccentric or concentric training leads to preservation of position sense and knee reaction angle 48 h after maximal intensity exercise of either types of muscle contraction.

Nutrition strategies before and during ultra-endurance event: A significant gap between science and practice.

The purpose of this study was to investigate and assess the nutritional practices of open-water swimmers, during the preparation period and the competition, as well as their implications on performance and anthropometric parameters according to their age. Twenty-four (n = 24) men open-water swimmers, twelve young (26.3 ± 4.9 years) and twelve older athletes (45.8 ± 9.7 years), participated in this study. Nutritional behavior-energy intake consumption, and anthropometric characteristics were evaluated prior to the Toroneos Gulf crossing (26 km). In addition, nutritional intakes during the race and anthropometrics after the race were also evaluated. Significant differences between the two groups were found for Toroneos Gulf crossing performance, BMI, and all variables of body composition at the preparation period (P < .05). The results involving energy consumption, in both preparation period and during the race, displayed significant differences between the two groups, while both groups exhibited significantly negative energy balances. During the race, significant differences were found also for the energy expenditure, relative energy intake, negative energy balance, relative consumption of carbohydrates per hour, and relative protein intake (P < .05). In both groups, lower intakes than the recommended were observed for macronutrient-micronutrient elements at any time point. Significant correlations were found between selected variables of body composition, nutritional intakes during the preparation period and the competition, and athletes' performance. In summary, this study provides strong evidence about the malnutrition of ultra-endurance swimmers prior and during their competition, with potential dangers for their health and performance as certain deficiencies in both macro- and micronutrient contents are present.

Reliability of resting intramuscular fiber conduction velocity evaluation.

Characterization of the least number of muscle fibers analyzed for a quick and reliable, evaluation of intramuscular fiber conduction velocity (MFCV) is of importance for sport scientists. The aim of this study was to evaluate the reliability of vastus lateralis' intramuscular MFCV measuring either 25 or 50 different muscle fibers per participant, as well as to compare intramuscular MFCV measured in 25 (C25 ), 50 (C50 ), or 140 (C140 ) muscle fibers. Resting vastus lateralis' MFCV was measured in 21 young healthy males (age 22.1±2.4 years) using intramuscular microelectrodes in different days. Test-retest reliability of MFCV's parameters was calculated for C25 and C50 , while MFCV was compared among C25 , C50 , and C140 . Significant differences of MFCV parameters were observed between C25 condition and those of C50 and C140 . The differences in MFCV values between conditions C50 and C140 were non-significant. A close correlation was found for MFCV between C50 and C140 (r=0.884-0.988, P=.000). All reliability measures of MFCV measured with 50 fibers were high (eg, ICC=0.813-0.980, P=.000), in contrast to C25 (eg, ICC=0.023-0.580 P>.05). In conclusion, an average of 50 different fibers per subject is sufficient to provide a quick and reliable intramuscular evaluation of vastus lateralis MFCV.

Body composition analysis in late-onset Pompe disease.

Pompe disease is an inherited metabolic disorder caused by α-glycosidase deficiency. The adult onset form is mainly characterized by progressive proximal muscle weakness and respiratory dysfunction. The aim of the present study is to evaluate body composition in adult patients before and after enzyme replacement therapy (ERT). Body composition was examined at baseline by means of dual x-ray absorptiometry (DXA) in nine adult patients and after different time periods in six of them who received ERT. Total BMD (bone mineral density) was initially mildly decreased in two patients, while femoral neck BMD was decreased in five patients. On the other hand fat mass was increased in the majority of patients, while body mass index (BMI) was high in four. ERT administration did not seem to induce obvious BMD changes in any patient. Conclusively, the greater femoral neck BMD involvement may be attributed to the lower mechanical load applied by the selectively weakened muscles, whereas the increased fat mass may be the result of metabolic and nutritional derangement.