The Relationship Between Performance and Asymmetries in Different Multidirectional Sprint Tests in Soccer Players

Practitioners usually include change of direction (COD) and linear speed measurements in the testing batteries of soccer players; however, despite being a commonly occurring action, curve sprint (CS) ability is rarely assessed in soccer. The aims of this study were to analyze the association between linear sprint, CS, and COD speed performances, and compare the association and direction of asymmetries between these skills. Thirty-three male soccer players performed linear sprint (17 m), CS (17 m), and COD-90⍛ speed tests (COD [8.5 + 8.5 m]). Our main findings were (a) a large relationship between linear and multidirectional tasks (COD-90⍛ and CS tests) (r = from 0.6 to 0.64, p < 0.05), (b) a moderate relationship between CS and COD-90⍛ tests (r = from 0.33 to 0.41, p < 0.05), with a certain opposite tendency (higher relationships between opposing directions [CurveLEFT - CODRIGHT; r = 0.41] than between equal directions [CurveLEFT – CODLEFT; r = 0.33]), and (c) no relationship (p > 0.05) between COD and CS asymmetries, with opposing directional dominance in ~70% of players (e.g., curve left and COD right dominance). These results indicate that performance in linear sprints is strongly related to performance in multidirectional trajectories, whereas CS and COD-90⍛ seem to be more independent actions. Additionally, the direction of asymmetry or dominance is generally opposite between the non-linear tasks measured.

The effectiveness of multiple brand portfolios: the role of directional dominance and brand interference on brand evaluation

PurposeThe purposes of the study were (1) to examine whether directional dominance between co-existing athlete brands and sponsor brands exists; (2) to explore whether directional dominance influences consumers' memory interference; and (3) to test whether brand interference interacts with directional dominance among brands to influence consumer evaluation and behaviors under multiple endorsement and sponsorship portfolios.Design/methodology/approachThe research is a 3 (directional dominance: symmetric dominance vs. asymmetric dominance with existing vs. asymmetric dominance with newly endorsed brand) x 2 (brand memory interference: interference vs. no interference) between-subjects factorial design.FindingsThe results indicate that (1) directional dominance influenced consumer brand interference, and directional dominance interacted with brand interference on (2) brand evaluation and (3) purchase intention in multiple brand portfolios.Originality/valueConsidering that conventional single-sponsor sponsorship or single-endorser endorsement portfolios are increasingly rare, research on concurrent circumstances of multiple endorsers and multiple endorsed brands in multiple brand portfolios was necessary. By expanding and reconceptualizing the context of brand networks, this study provides empirical evidence on how the dominance and directionality between endorser and (existing and newly) endorsed brands—an athlete endorser's strong pre-existing association with an existing endorsed brand in particular—influenced consumer brand interference and the brand evaluation in multiple brand portfolios.

Incorporating selfing to purge deleterious alleles in a cassava genomic selection program

Cassava has been found to carry high levels of recessive deleterious mutations and it is known to suffer from inbreeding depression. Breeders therefore consider specific approaches to decrease cassava’s genetic load. Using self fertilization to unmask deleterious recessive alleles and therefore accelerate their purging is one possibility. Before implementation of this approach we sought to understand better its consequences through simulation. Founder populations with high directional dominance were simulated using a natural selection forward simulator. The founder population was then subjected to five generations of genomic selection in schemes that did or did not include a generation of phenotypic selection on selfed progeny. We found that genomic selection was less effective under the directional dominance model than under the additive models that have commonly been used in simulations. While selection did increase favorable allele frequencies, increased inbreeding during selection caused decreased gain in genotypic values under the directional dominance. While purging selection on selfed individuals was effective in the first breeding cycle, it was not effective in later cycles, an effect we attributed to the fact that the generation of selfing decreased the relatedness of the genomic prediction training population from selection candidates. That decreased relatedness caused genomic prediction accuracy to be lower in schemes incorporating selfing. We found that selection on individuals partially inbred by one generation of selfing did increase mean genetic value of the partially inbred population, but that this gain was accompanied by a relatively small increase in favorable allele frequencies such that improvement in the outbred population was lower than might have been intuited.

Comparison of Change of Direction Speed Performance and Asymmetries between Team-Sport Athletes: Application of Change of Direction Deficit

The purpose of this study was twofold: (1) to examine differences in change of direction (COD) performance and asymmetries between team-sports while considering the effects of sex and sport; (2) to evaluate the relationship between linear speed, COD completion time, and COD deficit. A total of 115 (56 males, 59 females) athletes active in cricket, soccer, netball, and basketball performed the 505 for both left and right limbs and a 10-m sprint test. All team-sports displayed directional dominance (i.e., faster turning performance/shorter COD deficits towards a direction) (p ≤ 0.001, g = −0.62 to −0.96, −11.0% to −28.4%) with, male cricketers tending to demonstrate the greatest COD deficit asymmetries between directions compared to other team-sports (28.4 ± 26.5%, g = 0.19–0.85), while female netballers displayed the lowest asymmetries (11.0 ± 10.1%, g = 0.14–0.86). Differences in sprint and COD performance were observed between sexes and sports, with males demonstrating faster 10-m sprint times, and 505 times compared to females of the same sport. Male soccer and male cricketers displayed shorter COD deficits compared to females of the same sport; however, female court athletes demonstrated shorter COD deficits compared to male court athletes. Large significant associations (ρ = 0.631–0.643, p < 0.001) between 505 time and COD deficit were revealed, while trivial, non-significant associations (ρ ≤ −0.094, p ≥ 0.320) between COD deficit and 10-m sprint times were observed. In conclusion, male and female team-sport athletes display significant asymmetries and directional dominance during a high approach velocity 180° turning task. Coaches and practitioners are advised to apply the COD deficit for a more isolated measure of COD ability (i.e., not biased towards athletes with superior acceleration and linear speed) and perform COD speed assessments from both directions to establish directional dominance and create a COD symmetry profile.

Phenotypic plasticity for life-history traits in Drosophila melanogaster. III. Effect of the environment on genetic parameters

SummaryWe estimated genetic and environmental variance components for developmental time and dry weight at eclosion in Drosophila melanogaster raised in ten different environments (all combinations of 22, 25 and 28°C and 0·5, 1 and 4% yeast concentration, and 0·25% yeast at 25°C). We used six homozygous lines derived from a natural population for complete diallel crosses in each environment. Additive genetic variances were consistently low for both traits (h2 around 10%). The additive genetic variance of developmental time was larger at lower yeast concentrations, but the heritability did not increase because other components were also larger. The additive genetic effects of the six parental lines changed ranks across environments, suggesting a mechanism for the maintenance of genetic variation in heterogenous environments.The variance due to non-directional dominance was small in most environments. However, there was directional dominance in the form of inbreeding depression for both traits. It was pronounced at high yeast levels and temperatures but disappeared when yeast or temperature were decreased. This meant that the heterozygous flies were more sensitive to environmental differences than homozygous flies. Because dominance effects are not heritable, this suggests that the evolution of plasticity can be constrained when dominance effects are important as a mechanism for plasticity.