Effects of a 4-week eccentric training program on the repeated bout effect in young active women.

The aim of this study was to analyze the responses of women to the repeated bout effect (RBE) and to a short eccentric training program. Twenty-four young females were randomly assigned to a training group (TG, n = 14) or a control group (CG, n = 10). They performed two identical acute eccentric bouts (120 repetitions at 70% of 1RM) in a leg-press device in an 8 weeks interval. TG followed a 4-week-eccentric-training program between the bouts. Maximal isometric contraction, range of motion, peak power and quadriceps muscle soreness were compared between and within groups before and after the two acute eccentric bouts. TG and CG presented significant losses of isometric strength and peak power, and an increment in soreness after the first bout. Isometric strength and peak power were recovered faster in CG after the second bout (p < 0.05) compared with TG, which showed a similar recovery of these parameters after the second bout compared with the first one. A decrease in soreness and a faster recovery of range of motion were found in TG (p < 0.05) following the second bout compared with the first one, but not in CG. Data indicate that a 4-week eccentric training program may prevent the RBE over those adaptations related with muscle damage (e.g. strength loss), but it may increase RBE impact on inflammatory processes (e.g. soreness). Key pointsAn acute bout of eccentric exercise induces losses of strength, peak power and range of motion, and increases muscle soreness in young active women.When the acute eccentric bout is repeated by young women, the losses of strength and power are smaller, indicating less muscle damage. However, muscle pain and range of motion do not present any difference with the results obtained after the first bout, which would indicate that the repeated bout effect does not affect inflammatory response after acute eccentric exercise.Four weeks of eccentric training is enough to increase maximal isometric strength, but not dynamic strength (1RM) or peak power. Furthermore, this training seems to prevent those adaptations provided by the repeated bout effect related with muscle damage. On the other hand, the eccentric training seems to be a positive tool to decrease muscle soreness, and thus the inflammatory response, associated to a repeated acute eccentric bout.

Comparison of technical and physiological characteristics of prepubescent soccer players of different ages.

Although soccer is one of the most widely played sports around the world, studies about young players and the success factors in soccer are still scarce. Therefore, the purpose of this study was to offer some insight into the factors contributing to success in this sport and to describe how physiological and technical performance evolves in young soccer players. Soccer technical skills during match play, maximum voluntary isometric contraction and power of lower limbs, jumping ability and endurance parameters were assessed in 30 prepubescent male soccer players with the same experience in soccer training. Subjects were divided into 2 groups of 15 children, a younger group (YG), aged 9.4 +/- 0.3 years, and an older group (OG), aged 11.8 +/- 0.2 years. Correlations between technical and physiological parameters were also described. Significant difference was set at p < 0.05. Differences between YG and OG appeared in physiological performance, mainly in VO(2)peak expressed in absolute values, VO(2) at different speeds, perceived exertion in treadmill test, jump performance, strength, and peak power of lower limbs. Among the technical skills measured, significant differences were found only in heading. The differences found between groups showed that most physical capacities that were measured here have an important increase during the first stages of puberty, pointing out that a specific training at these ages is necessary to get an appropriate basis for future performance. Besides, over 30% of the technical performance measured in this study can be explained with the physiological parameters. The data shown in this paper help to determine the most important capacities in youth soccer, which can facilitate the development of more appropriate selection models and trainings.

Feelings of well being in elderly people: relationship to physical activity and physical function.

The aim of the research was to investigate in a sample of Spanish elderly whether measures of physical activity and physical function are related to feelings of well being, and whether level of dependence is a moderator in the relation of well being, physical activity and physical function. The sample was a cohort of 151 elderly people (89 women and 62 men, aged 60-98 years) from the North of Spain. Participants completed surveys including demographic characteristics, and measures of physical activity (Yale Physical Activity Survey, YPAS), instrumental activities of daily living (Barthel Index, BI) and well being (Psychological Well Being Scale, from Spanish: Escala de Bienestar Psicológico=EBP). Components of the physical function were measured by the Senior Fitness Test (SFT). Upper and lower body strength, dynamic balance, aerobic endurance, self-reported weekly energy expenditure and physical activity total time were significantly correlated with both Material and Subjective well being. All components of physical function were significantly impaired in dependent subjects when compared to independent individuals of the same sex and physical activity category. Significant differences were also observed in Subjective well being among less active dependent or independent individuals. In conclusion, physical function and physical activity are related to feelings of well being, and results emphasize the positive functional and psychological effects of physical activity in dependent subjects.

Eccentric training impairs NF-kappaB activation and over-expression of inflammation-related genes induced by acute eccentric exercise in the elderly.

The present study was aimed to investigate in elderly humans changes in NF-kappaB activation and in the expression of the inflammation-related genes inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6) induced in peripheral blood mononuclear cells (PBMC) by acute eccentric exercise and by submaximal eccentric training. Eleven subjects, aged 66-75 years, carried out 2 bouts of eccentric exercise separated by 8 weeks of training. Following the first bout, NF-kappaB activation, and protein level of p50/p65 subunits, phospho-IkappaBalpha and phospho-IKKalpha increased, while IkappaBalpha protein level was significantly reduced. This was accompanied by a significant increase in iNOS, COX-2 and IL-6 mRNA protein level and protein content. Changes were significantly attenuated following the second exercise bout. In conclusion, acute eccentric exercise increases NF-kappaB activation and the expression of several inflammation-related genes in PBMC from elderly individuals. Regular eccentric training might be an effective method of preventing undesirable inflammatory responses induced by eccentric exercise.

Effects of short vs. long rest period between sets on elbow-flexor muscular endurance during resistance training to failure.

This study aimed to examine short-term resistance training effects of resting period length between sets on maximal number of repetitions and mean velocity over a moderate-intensity (60% of the maximum voluntary isometric contraction [MVIC]) set to failure on elbow-flexor muscles. The MVIC and surface electromyographic activity (sEMG) were also measured. Twenty-one untrained subjects were divided into 3 groups: short rest between sets (1 minute; SR), long rest between sets (4 minutes; LR), and nontraining control group (CG). The SR and LR performed 3 sets to failure in an arm-curl machine, 2 days per week for 5 weeks, with moderate loads (60-75% of the MVIC). The LR completed a significantly higher (31.6%, p < 0.05) total training volume than the SR. Both training groups enhanced the maximal number of repetitions to failure, with no significant differences in the magnitude of gains. The posttraining average velocity achieved by the SR at 40, 50, 60, 70, 80, and 90% of the total number of repetitions completed was significantly higher (p < 0.05) than the corresponding average velocity achieved on pretraining conditions, whereas no significant differences were observed in the LR. No significant changes in the MVIC or sEMG were observed in any group. We conclude that short-term elbow-flexor resistance training to failure, allowing 1 or 4 minutes of rest between sets, induces similar gains concerning local muscular endurance. Nevertheless, only the SR training approach reduced the rate of decline in the average repetition velocity during a set to failure. This can be of some importance in sport modalities in which not only the maximal number of repetitions (e.g., muscle endurance), but also a greater maintenance of high repetition velocities, may be critical for performance.