Ross Sanders

Static and dynamic assessment of the Biodex dynamometer

SummaryThe validity and accuracy of the Biodex dynamometer was investigated under static and dynamic conditions. Static torque and angular position output correlated well with externally derived data (r=0.998 andr>0.999, respectively). Three subjects performed maximal voluntary knee extensions and flexions at angular velocities from 60 to 450° · s−1. Using linear accelerometry, high speed filming and Biodex software, data were collected for lever arm angular velocity and linear accelerations, and subject generated torque. Analysis of synchronized angular position and velocity changes revealed the dynamometer controlled angular velocity of the lever arm to within 3.5% of the preset value. Small transient velocity overshoots were apparent on reaching the set velocity. High frequency torque artefacts were observed at all test velocities, but most noticeably at the faster speeds, and were associated with lever arm accelerations accompanying directional changes, application of resistive torques by the dynamometer, and limb instability. Isokinematic torques collected from ten subjects (240, 300 and 400° · s−1) identified possible errors associated with reporting knee extension torques at 30° of flexion. As a result of tissue and padding compliance, leg extension angular velocity exceeded lever arm angular velocity over most of the range of motion, while during flexion this compliance meant that knee and lever arm angles were not always identical, particularly at the start of motion. Nevertheless, the Biodex dynamometer was found to be both a valid and an accurate research tool; however, caution must be expercised when interpreting and ascribing torques and angular velocities to the limb producing motion.

Examining Movement Variability in the Basketball Free-Throw Action at Different Skill Levels

Abstract The analysis of variability both within and between performers can reveal important information about how athletes satisfy situational constraints. Transitory changes in the basketball free-throw shot were examined across different stages in skill development. Six female basketball players were selected, representing a range of playing expertise (pretest: 0–90% baskets scored). Each participant was video recorded performing 30 shots. Contrary to predictions, there was not a clear pattern of a reduction in trajectory variability with increasing skill level. However, improvements in skill level were associated with an increasing amount of intertrial movement consistency from the elbow and wrist joints. It is suggested that the angular motions of the elbow and wrist joints were compensated for each other toward the end of each throw to adapt to subtle changes in release parameters of the ball.

The influence of familiarization on the reliability of force variables measured during unloaded and loaded vertical jumps.

The purpose of this study was to determine the number of familiarization sessions required to obtain an accurate measure of reliability associated with force variables recorded during unloaded and loaded (30 and 60% of 1 repetition maximum squat [1RM]) static vertical jumps (SJ). Nine physically active men attended 4 separate testing sessions over a 2-week period. Force platform recordings of peak force, peak rate of force development (pRFD), average rate of force development, takeoff velocity, average power, and peak power were obtained for each jump. During each of the 4 testing sessions, 3 jumps were performed under each of the load conditions. The average of the force variables were used in the analysis. Familiarization was assessed using the scores obtained during the 4 separate testing sessions. Reliability was assessed by calculating intraclass correlation coefficients (ICCs) and coefficient of variation (CV) associated with the force variables. No significant differences (p > 0.05) were obtained between the testing sessions for any of the force variables. With the exception of pRFD, the force variables showed reasonably good levels of test-retest reliability (ICC range: 0.75–0.99; CV range: 1.2–7.6%). High levels of reliability can be achieved in a variety of force variables without the need for familiarization sessions when performing SJ under unloaded conditions and with loads of 30 and 60% of 1RM squat with physically active men.

Developing Effective Pre-performance Routines in Golf: Why Don't We Ask the Golfer?

The purpose of this investigation was to explore the nature of pre-performance routines used in golf. Six male international golfers were recruited to participate in this study (Age M = 29; handicap M = +1.5; years playing golf M = 16.25). The golfers were interviewed individually to gain an understanding of participants’ perceptions of the nature and function of their pre-performance routines. The data were thematically analyzed using interpretative phenomenological analysis. In total, 9 super-ordinate themes emerged: allocation of attention, psychological skills, shot selection, routine mind set, routine composition, compulsive behaviors, routine evolution/application, top players, and moderating factors. Results suggest that the development of routines is dependent on the personality, coping resources, and situational appraisals of each individual performer.

Shoulder and hip roll changes during 200-m front crawl swimming.

PURPOSE To determine accurately the magnitude and changes in shoulder roll (SR) and hip roll (HR) throughout a 200-m maximum front crawl swim and whether SR and HR were associated with swimming velocity (V). Bilateral roll asymmetries and timing differences between SR and HR were also investigated. METHODS Ten male swimmers of national/international level performed a maximum 200-m front crawl swim. Performance was recorded with four below- and two above-water synchronized cameras and four nonbreathing stroke cycles (SC) were analyzed (one for each 50 m). SR and HR were calculated separately. RESULTS Swimmers rolled their shoulders significantly more than their hips (P < 0.001). V generally decreased during the test, and HR was significantly higher in SC4 than in SC1 (P = 0.001). SR had a negative and significant correlation with V in each SC (-0.663 <or= r <or= -0.634, 0.037 <or= P <or= 0.049), with the exception of SC4. Although several roll profiles existed, left-side SR dominance was identified, with swimmers rolling their shoulders significantly more to the left than to the right side (0.000 <or= P <or= 0.022). Despite individual differences in the timings of maximum SR and HR to the left and right sides, no consistent pattern was found for the group. CONCLUSION Separate calculation is required for SR and HR to explore their influence on front crawl swimming. Faster swimmers tended to roll their shoulders less than slower swimmers. The increase in HR as the test progressed is possibly associated with a decrease in stroke frequency and increase in SC duration. Given that all swimmers were right-handed and that SR was significantly greater to the left than to the right side, it seems that factors related to handedness might affect SR symmetry in swimming.

The Physical Demands of Olympic Yacht Racing

The primary purpose of this study was to quantify the up wards forces of the feet on the hiking strap and the forces in the mainsheet of four Olympic classes of racing dinghies (Europe, Laser. Finn and 470) during realistic on-water sailing in varying wind conditions. The secondary aim of the study was to measure the joint angles adopted by the sailors and boat heel angles. The tertiary aim was to identify events and sailing conditions associated with large or patterned force production. Forces in the hiking strap and mainsheet of four classes of Olympic sailing dinghies were measured on eleven New Zealand sailors during simulated on-water racing in a range of wind conditions. Up-wind hiking strap forces reached an average of 73-87% of predicted maximal voluntary contraction (pred MVC), with peak forces exceeding 100% pred MVC. Mainsheet forces reached 25-35% pred MVC, with peak forces reaching 40-50% pred MVC. Off-wind hiking strap and mainsheet forces were considerably lower than up-wind forces. Ankle and hip joint angles increased and knee joint angles decreased with increasing wind speed during up-wind sailing. Large forces occurred in the hiking strap and mainsheet when boats reached the tops of wave during up-wind sailing in high wind speeds and when a gust of wind hit the boat. During off-wind sailing large forces were observed in the mainsheet when surfing down waves. It is recommended that the intensities and joint angles found in this study be used as a basis for the development of class specific off-water physical conditioning programmes.

Psychological consequences of childhood obesity: psychiatric comorbidity and prevention

Childhood obesity is one of the most serious public health challenges of the 21st century with far-reaching and enduring adverse consequences for health outcomes. Over 42 million children <5 years worldwide are estimated to be overweight (OW) or obese (OB), and if current trends continue, then an estimated 70 million children will be OW or OB by 2025. The purpose of this review was to focus on psychiatric, psychological, and psychosocial consequences of childhood obesity (OBy) to include a broad range of international studies. The aim was to establish what has recently changed in relation to the common psychological consequences associated with childhood OBy. A systematic search was conducted in MEDLINE, Web of Science, and the Cochrane Library for articles presenting information on the identification or prevention of psychiatric morbidity in childhood obesity. Relevant data were extracted and narratively reviewed. Findings established childhood OW/OBy was negatively associated with psychological comorbidities, such as depression, poorer perceived lower scores on health-related quality of life, emotional and behavioral disorders, and self-esteem during childhood. Evidence related to the association between attention-deficit/hyperactivity disorder (ADHD) and OBy remains unconvincing because of various findings from studies. OW children were more likely to experience multiple associated psychosocial problems than their healthy-weight peers, which may be adversely influenced by OBy stigma, teasing, and bullying. OBy stigma, teasing, and bullying are pervasive and can have serious consequences for emotional and physical health and performance. It remains unclear as to whether psychiatric disorders and psychological problems are a cause or a consequence of childhood obesity or whether common factors promote both obesity and psychiatric disturbances in susceptible children and adolescents. A cohesive and strategic approach to tackle this current obesity epidemic is necessary to combat this increasing trend which is compromising the health and well-being of the young generation and seriously impinging on resources and economic costs.

Kinematic differences between front crawl sprint and distance swimmers at sprint pace.

Abstract The purpose of this study was to use three-dimensional methods to determine whether there are distinct kinematic differences between sprint and distance front crawl swimmers when swimming at a sprint pace. Seven sprint and eight distance specialists performed four 25-m sprints through a 6.75-m3 calibrated space recorded by six gen-locked cameras. The variables of interest were: average swim velocity, stroke length, stroke frequency, upper limb and foot displacement, elbow angle, shoulder and hip roll angles, duration of stroke phases, and the time corresponding to particular events within the stroke cycle relative to hand entry. Differences between sprint and distance swimmers were assessed with an independent t-test for each variable, in addition to effect size calculations. Differences between sprint and distance front crawl swimmers were generally small and not significant when swimming at a sprint pace. Differences were limited to temporal aspects of the stroke cycle. These findings suggest that coaches should not train sprint and distance specialists differently in terms of technique development.

Rolling rhythms in front crawl swimming with six-beat kick

The purpose of this study was to establish the rhythm characteristics of skilled front crawl swimmers using a six-beat kick. These included the amplitudes of the first three Fourier harmonics (H1, H2, H3) and their percent contributions to power contained in the angular displacement signals of the shoulders, hips, knees, and ankles with respect to the longitudinal axis in line with the swimming direction. Three-dimensional video data of seven national/international level swimmers were collected during simulated 200m front crawl races in which swimmers maintained six-beat kicking patterns. Swimmers differed in all variables but had small variability across the four 50m laps. Modest changes occurred during the 200m, with the exception of shoulder roll, which remained constant and was represented almost entirely by a single sinusoid (H1). Changes across laps reached significance for swimming speed, stroke rate, hip roll, and H3 wave velocity between the knee and ankle. A H3 body wave of moderate and increasing velocity travelled caudally from hip to ankle. In the light of existing knowledge of aquatic locomotion this was compatible with the goal of generating propulsion in an efficient manner.

Measures of Reliability in the Kinematics of Maximal Undulatory Underwater Swimming

PURPOSE The purposes of this article were to establish the reliability of the kinematics of maximal undulatory underwater swimming (UUS) in skilled swimmers, to determine any requirement for familiarization trials, to establish the within-subject (WS) variability of the kinematics, and to calculate the number of cycles required to accurately represent UUS performance. METHODS Fifteen male swimmers performed 20 maximal UUS trials (two cycles per trial) during four sessions. The magnitude of any systematic bias present within the kinematic variables was calculated between session, trial, and cycle. Random error calculations were calculated to determine the WS variation. An iterative intraclass correlation coefficient (ICC) process was used to determine the number of cycles required to achieve a stable representation of each kinematic variable. RESULTS Significant differences were found between session 1 and all other sessions for several variables, indicating the requirement for a familiarization session. Results indicated a wide range of WS variation (coefficient of variation [CV] = 1.21%-12.42%). Reductions in WS variation were observed for all variables when the number of cycles of data used to calculate WS variation was increased. Using six cycles of data, including additional cycles of data, provided diminishing returns regarding the reduction of WS variation. The ICC analysis indicated that an average of nine cycles (mean ± SD = 9.47 ± 5.63) was required to achieve the maximum ICC values attained, and an average of four cycles (mean ± SD = 3.57 ± 2.09) was required to achieve an ICC of 0.95. CONCLUSIONS After determining the systematic bias and establishing the requirement for a familiarization session, six cycles of data were found to be sufficient to provide high levels of reliability (CV(TE) = 0.86-8.92; ICC = 0.811-0.996) for each of the UUS kinematic variables.