Kenton R. Kaufman and William J. Shaughnessy
Janet D. Larsen and David W. Rainey
James G. Hay, Qi Liu and James G. Andrews
The purpose of this study was to determine the effect that body roll has on the path followed by the hand during the pull phase in freestyle swimming. The trunk and right arm were modeled as two rigid segments joined at the shoulder by a simple hinge joint. The arm segment was assigned an elbow flexion angle, and the hand was made to move in a plane through the shoulder parallel to the sagittal plane of the rotating trunk. Shoulder extension and trunk roll occurred simultaneously at selected rates. Medial deviations of the hand to the midline of the trunk can be obtained with body roll alone and require less roll than is usually observed among competitive swimmers. When body roll exceeds the amount necessary to produce the desired medial deviation of the hand, the swimmer must move the arm away from, rather than toward, the trunk's midline.
Akinori Nagano and Karin G.M. Gerritsen
The purpose of this study was twofold: (a) to systematically investigate the effect of altering specific neuromuscular parameters on maximum vertical jump height, and (b) to systematically investigate the effect of strengthening specific muscle groups on maximum vertical jump height. A two-dimensional musculoskeletal model which consisted of four rigid segments, three joints, and six Hill-type muscle models, representing the six major muscles and muscle groups in the lower extremity that contribute to jumping performance, was trained systematically. Maximum isometric muscle force, maximum muscle shortening velocity, and maximum muscle activation, which were manipulated to simulate the effects of strength training, all had substantial effects on jumping performance. Part of the increase in jumping performance could be explained solely by the interaction between the three neuromuscular parameters. It appeared that the most effective way to improve jumping performance was to train the knee extensors among all lower extremity muscles. For the model to fully benefit from any training effects of the neuromuscular system, it was necessary to continue to reoptimize the muscle coordination, in particular after the strength training sessions that focused on increasing maximum isometric muscle force.
Brendan Burkett, James Smeathers and Timothy M. Barker
For amputees to perform an everyday task, or to participate in physical exercise, it is crucial that they have an appropriately designed and functional prosthesis. Past studies of transfemoral amputee gait have identified several limitations in the performance of amputees and in their prosthesis when compared with able-bodied walking, such as asymmetrical gait, slower walking speed, and higher energy demands. In particular the different inertial characteristics of the prosthesis relative to the sound limb results in a longer swing time for the prosthesis. The aim of this study was to determine whether this longer swing time could be addressed by modifying the alignment of the prosthesis. The following hypothesis was tested: Can the inertial characteristics of the prosthesis be improved by lowering the prosthetic knee joint, thereby producing a faster swing time? To test this hypothesis, a simple 2-D mathematical model was developed to simulate the swing-phase motion of the prosthetic leg. The model applies forward dynamics to the measured hip moment of the amputee in conjunction with the inertial characteristics of prosthetic components to predict the swing-phase motion. To evaluate the model and measure any change in prosthetic function, we conducted a kinematic analysis on four Paralympic runners as they ran. When evaluated, there was no significant difference (p > 0.05) between predicted and measured swing time. Of particular interest was how swing time was affected by changes in the position of the prosthetic knee axis. The model suggested that lowering the axis of the prosthetic knee could reduce the longer swing time. This hypothesis was confirmed when tested on the amputee runners.
Sheila C. Fairweather, John J. Reilly, Stanley Grant, Arthur Whittaker and James Y. Paton
The primary aim of this study was to assess the ability of the CSA accelerometer to measure physical activity in preschool children. A secondary aim was to examine inter-instrument differences and the effect of accelerometer placement on output. Eleven subjects (mean age = 4.0 years, SD = 0.4) wore the CSA-7164 for a 45-min preschool exercise class. They were observed throughout the class, and their engagement in activity was quantified using the Children’s Physical Activity Form (CPAF). The effect of accelerometer positioning (left vs. right hip) was assessed in 10 subjects over 2 days. CSA output during the class was highly correlated with the CPAF score (r = 0.87, p < .001), and rank order correlations between the 2 methods were also highly significant (r = 0.79, p < .01). Differences in CSA output between left and right hip reached statistical significance (paired t, p < .05), but these differences were small and probably of limited biological significance. The CSA appears to be an appropriate tool for assessment of physical activity in preschool children, but further studies on stability of activity as measured by CSA, as well as its validity, are urged.
Maurice R. Yeadon, Pui W. Kong and Mark A. King
This study used kinematic data on springboard diving performances to estimate viscoelastic parameters of a planar model of a springboard and diver with wobbling masses in the trunk, thigh, and calf segments and spring dampers acting at the heel, ball, and toe of the foot segment. A subject-specific angle-driven eight-segment model was used with an optimization algorithm to determine viscoelastic parameter values by matching simulations to four diving performances. Using the parameters determined from the matching of a single dive in a simulation of another dive resulted in up to 31% difference between simulation and performance, indicating the danger of using too small a set of kinematic data. However, using four dives in a combined matching process to obtain a common set of parameters resulted in a mean difference of 8.6%. Because these four dives included very different rotational requirements, it is anticipated that the combined parameter set can be used with other dives from these two groups.
Jaclyn B. Caccese and Thomas W. Kaminski
The Balance Error Scoring System (BESS) is the current standard for assessing postural stability in concussed athletes on the sideline. However, research has questioned the objectivity and validity of the BESS, suggesting that while certain subcategories of the BESS have sufficient reliability to be used in evaluation of postural stability, the total score is not reliable, demonstrating limited interrater and intrarater reliability. Recently, a computerized BESS test was developed to automate scoring.
To compare computerderived BESS scores with those taken from 3 trained human scorers.
Interrater reliability study.
Athletic training room.
NCAA Division I student athletes (53 male, 58 female; 19 ± 2 y, 168 ± 41 cm, 69 ± 4 kg).
Subjects were asked to perform the BESS while standing on the Tekscan (Boston, MA) MobileMat® BESS. The MobileMat BESS software displayed an error score at the end of each trial. Simultaneously, errors were recorded by 3 separate examiners. Errors were counted using the standard BESS scoring criteria.
Main Outcome Measures:
The number of BESS errors was computed for the 6 stances from the software and each of the 3 human scorers. Interclass correlation coefficients (ICCs) were used to compare errors for each stance scored by the MobileMat BESS software with each of 3 raters individually. The ICC values were converted to Fisher Z scores, averaged, and converted back into ICC values.
The double-leg, single-leg, and tandem-firm stances resulted in good agreement with human scorers (ICC = .999, .731, and .648). All foam stances resulted in fair agreement.
Our results suggest that the MobileMat BESS is suitable for identifying BESS errors involving each of the 6 stances of the BESS protocol. Because the MobileMat BESS scores consistently and reliably, this system can be used with confidence by clinicians as an effective alternative to scoring the BESS.
Thomas L. McKenzie and B. Robert Carlson
Stephanie Alley, Jannique G.Z. van Uffelen, Mitch J. Duncan, Katrien De Cocker, Stephanie Schoeppe, Amanda L. Rebar and Corneel Vandelanotte
Bureau of Statistics, 2012 ). Therefore, due to the high levels of sitting time in older adults and the health benefits of reducing sitting time, interventions are needed to reduce sitting in older adults. It is necessary to distinguish between different domains of sitting (TV, computer, other leisure