A meta-analysis was conducted to examine gender differences in motor performance during childhood and adolescence. Data were 64 studies yielding 702 effect sizes based on 31,444 subjects. Age was regressed on effect size, and the relation was significant for 12 of 20 tasks. Several types of age-related curves were found; the curve for a throwing task was the most distinctive. Five of the tasks followed a typical curve of gender differences across age. For eight tasks, gender differences were not related to age, and effect sizes were small. Results are discussed relating the development of gender differences to biological and environmental sources.

This study examined the relationship of sport-specific knowledge to the development of children's skills in basketball. Two experiments were conducted. The first compared child expert and novice basketball players in two age leagues, 8-10 years and 11-12 years, on the individual components of basketball performance (control of the basketball, cognitive decisions, and motor execution) and on measures of basketball knowledge, dribbling skill, and shooting skill. Child expert players of both age groups possessed more shooting skill and more basketball knowledge. A canonical correlation analysis indicated that basketball knowledge was related to decision-making skill, whereas dribbling and shooting skill were related to the motor components of control and execution. Experiment 2 examined the changes in the individual components of performance, basketball knowledge, dribbling skill, and shooting skill from the beginning to the end of the season. Subjects improved in the cognitive decision-making and control components of performance across the course of the season, and basketball knowledge increased from the beginning to the end of the season. Only basketball knowledge was a significant predictor of the decision-making component at the end of the season. The overall results of Experiments 1 and 2 indicate that the development of the sport knowledge base plays a salient role in skilled sport performance of children.

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SummarySpvC is encoded by the Salmonella virulence plasmid. We have investigated the biochemical function of SpvC and the mechanism by which it is secreted by bacteria and translocated into infected macrophages. We constructed a strain carrying a deletion in spvC and showed that the strain is attenuated for systemic virulence in mice. SpvC can be secreted in vitro by either the SPI-1 or SPI-2 type III secretion systems. Cell biological and genetic experiments showed that translocation of the protein into the cytosol of macrophages by intracellular bacteria is dependent on the SPI-2 T3SS. Using antibodies specific to phospho-amino acids and mass spectrometry we demonstrate that SpvC has phosphothreonine lyase activity on full-length phospho-Erk (pErk) and a synthetic 13-amino-acid phospho-peptide containing the TXY motif. A Salmonella strain expressing spvC from a plasmid downregulated cytokine release from infected cells.

Using a lifespan approach, the authors investigated developmental features of the control of ballistic aiming arm movements by manipulating movement complexity, response uncertainty, and the use of precues. Four different age groups of participants (6- and 9-year-old boys and girls and 24- and 73-year-old men and women, 20 participants in each age group) performed 7 types of rapid aiming arm movements on the surface of a digitizer. Their movement characteristics such as movement velocity, normalized jerk, relative timing, movement linearity, and intersegment intervals were profiled. Analyses of variance with repeated measures were conducted on age and task effects in varying movement complexity (Study 1), response uncertainty (Study 2), and precue use (Study 3) conditions. Young children and senior adults had slower, more variant, less smooth, and less linear arm movements than older children and young adults. Increasing the number of movement segments resulted in slower and more variant responses. Movement accuracy demands or response uncertainty interacted with age so that the 6- and 74-year-old participants had poorer performances but responded similarly to the varying treatments. Even though older children and young adults had better performances than young children and senior adults, their arm movement performance declined when response uncertainty increased. The analyses suggested that young children's and senior adults' performances are poorer because less of their movement is under central control, and they therefore use on-line adjustments. In addition, older children and young adults use a valid precue more effectively to prepare for subsequent movements than do young children and senior adults, suggesting that older children and young adults are more capable of organizing motor responses than are young children and senior adults.