Within - and between - session reliability of the spider drill test to assess Change of Direction Speed in youth tennis athletes

Agility or Change of Direction Speed (CODS) is a critical physical attribute in a sport such as tennis, which is categorised by frequent and multiple changes of direction. Recently a CODS test called the ‘spider drill’ has been used to assess tennis athletes’ ability to change direction. To the authors’ knowledge, no study has solely assessed its reliability and compared this with other commonly-used CODS tests; thus, this was the aim of the study. Ten nationally ranked youth tennis athletes (age: 15.1 ± 2.6; mass: 66.4 + 17.2 kg; height: 163.0 + 16.2 cm) completed three trials of the spider drill, modified t-test and pro-agility test on two separate testing occasions. All CODS tests had low typical percentage error, both within-sessions (CV = 1.8 - 4.1%), and between session (CV = 1.2 - 3.7%). The SEM was also consistent within tests both within- and between- testing sessions. Within-session test-retest consistency illustrates strong reliability for the spider drill (ICC = 0.93, 0.95), modified t-test (ICC = 0.79, 0.83), however for pro-agility session 2 fell outside of the accepted threshold (ICC = 0.88, 0.69). These trends were similar when assessing between-session consistency, with both the spider drill and modified t-test providing high levels of reliability (ICC = 0.95 and 0.97 respectively). However, the pro-agility fell outside of the accepted threshold (ICC = 0.66), with 95% confidence intervals wide-ranging in nature (95% CI: 0.11 - 0.9). These results suggest that the spider drill and modified t-test are both reliable tests when measuring CODS within youth tennis athletes. Strength and conditioning practitioners could consider changes in excess of ± 1.1% as meaningful (based off the SDD) when assessing CODS through the spider drill or modified t-test within youth tennis athletes

Establishment of “The South African Bioinformatics Student Council” and activity highlights:

The South African Society for Bioinformatics1 (SASBi) was officially formed in September 2012 during a joint Congress with the South African Genetics Society (SAGS). Prior to this there was no official body to represent bioinformatic researchers and students in the country. The establishment of SASBi also led to the establishment of the Student Society as a platform for students to meet and discuss their research activities, but also to socialise and broaden their network of knowledge and friendships. A small group of students joined as volunteers to pioneer and set up a SASBi Student Council (SASBiSC). As a first step, one representative, selected from the attendees present at the first Joint Congress of SASBi and SAGS, was elected to the main SASBi Council

Lower extremity stiffness: considerations for testing, performance enhancement and injury risk

Force-deformation characteristics of the lower limb have been associated with athletic performance and may modulate the risk of injury. In-spite of these known associations, measurements of lower extremity stiffness are not commonly administered by strength and conditioning coaches. This review provides an overview of the available literature pertaining to the effects of lower extremity stiffness on physical performance and injury risk. Practical methods of monitoring and training stiffness are also discussed. The cumulative body of evidence indicates that increases in lower extremity stiffness are associated with heightened performance in athletic tasks such as hopping, jumping, throwing, endurance running, sprinting and changing direction. Relationships with injury are less conclusive as both excessive and insufficient limb stiffness have been postulated to increase risk. Thus, the ‘optimal’ level of stiffness appears to be dependent on the anthropometry, and physical capabilities of the athlete, in addition to sport-specific activity demands. Training interventions can positively enhance lower extremity stiffness, including isometric, eccentric and isotonic strength training and plyometrics. Complex training also appears to provide a potent stimulus and may be more effective than the use of singular training modes. For plyometric activities, it is recommended that coaches use a developmental sequence of exercises with increasing eccentric demand to provide an appropriate stimulus based on the training age and technical competency of the athlete

Postactivation potentiation and change of direction speed in elite academy rugby players

This study investigated the effect of preceding pro-agility sprints with maximal isometric squats to determine if postactivation potentiation (PAP) could be harnessed in change of direction speed. Sixteen elite under-17 rugby union players (age: 16 +/- 0.41yrs; body mass: 88.7 +/- 12.1kg, height: 1.83 +/- 0.07m) from an Aviva Premiership rugby club were tested. Subjects performed a change of direction specific warm-up, followed by two baseline pro-agility tests. After 10 minutes recovery, 3 x 3-second maximal isometric squats with a 2 minute recovery between sets were completed as a conditioning activity (CA) on a force plate where peak force and mean rate of force development over 300 milliseconds were measured. The pro-agility test was repeated at set time intervals of 1, 3, 5 and 7 minutes following the CA. Overall pro-agility times were significantly slower (p < 0.05) at 1-minute post-CA compared to the baseline (3.3%), with no significant differences occurring at 3, 5 or 7 minutes post-CA. Therefore, it appears that performing multiple sets of maximal isometric squats do not enhance pro-agility performance

Initial Estimates of Optical Constants of Mars Candidate Materials

Data obtained at visible and near-infrared wavelengths by OMEGA on Mars Express and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al- OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. To constrain the abundances of these phyllosilicates, spectral analyses of mixtures are needed. We report on our effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/ hydroxylated silicates with each other and with two analogs for other Martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass, hereafter referred to as palagonite). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al-rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 micron

Jumping-based asymmetries are negatively associated with jump, change of direction, and repeated sprint performance, but not linear speed, in adolescent handball athletes

The aim of the present study was to determine the association of multi-directional jumping asymmetries with measures of physical performance. Forty-two youth handball athletes (age: 16.0 ± 1.3 years; body height: 174.11 ± 7.3 cm; body mass: 70.49 ± 13.3 kg) performed a mid-season fitness test battery consisting of single leg countermovement, lateral and broad jump tests, two change of direction speed (CODS) tests, an 8 x 10 m repeated sprint test, and a 20 m sprint. The Kappa coefficient showed only ‘slight’ levels of agreement (K range = -0.05 to 0.15), indicating that asymmetries rarely favoured the same side during each of the jump tests. The single leg countermovement jump showed significantly (p = 0.006) larger asymmetries (11.2 ± 8.4) than the broad jump (6.4 ± 4.6) and significant correlations were present between jumping asymmetries and jump (r = -0.32 to -0.52), CODS (r = 0.31 to 0.32) and repeated sprint (r = 0.35 to 0.40) performance. The findings of the present study highlight the independent nature of jumping asymmetries and associations with measures of physical performance. Practitioners are encouraged to use multiple tests to detect existing side differences and consider appropriate training interventions for the reduction of inter-limb asymmetries