Previously there existed no efficacious maximal effort, VO2peak prediction test for subjects who, because of injury, can exercise at high intensity only on a device such as a cycle ergometer. This study's purpose was to develop and validate such a test, a 12-Minute Stationary Cycle Ergometer Test (12MSCET), for college-age physically active men and women. For 60 college-age men and women, and a gender-based resistance setting, the total work done on the 12MSCET and body weight were found to be highly predictive of VO2peak, measured via open circuit spirometry. Furthermore, the torques required for such a test are, for this sample, approximately 50% of those required in other predictive protocols. To date, the 12MSCET has been used for VO2peak assessment of over 300 military cadets who, because of injury, found cycling their only efficacious high-intensity aerobic modality.
Cecilia Persson, Jon Summers and Richard M. Hall
A spinal cord injury may lead to loss of motor and sensory function and even death. The biomechanics of the injury process have been found to be important to the neurological damage pattern, and some studies have found a protective effect of the cerebrospinal fluid (CSF). However, the effect of the CSF thickness on the cord deformation and, hence, the resulting injury has not been previously investigated. In this study, the effects of natural variability (in bovine) as well as the difference between bovine and human spinal canal dimensions on spinal cord deformation were studied using a previously validated computational model. Owing to the pronounced effect that the CSF thickness was found to have on the biomechanics of the cord deformation, it can be concluded that results from animal models may be affected by the disparities in the CSF layer thickness as well as by any difference in the biological responses they may have compared with those of humans.
Alexander Tsouknidas, Nikoalos Michailidis, Savvas Savvakis, Kleovoulos Anagnostidis, Konstantinos-Dionysios Bouzakis and Georgios Kapetanos
This study presents a CT-based finite element model of the lumbar spine taking into account all function-related boundary conditions, such as anisotropy of mechanical properties, ligaments, contact elements, mesh size, etc. Through advanced mesh generation and employment of compound elements, the developed model is capable of assessing the mechanical response of the examined spine segment for complex loading conditions, thus providing valuable insight on stress development within the model and allowing the prediction of critical loading scenarios. The model was validated through a comparison of the calculated force-induced inclination/deformation and a correlation of these data to experimental values. The mechanical response of the examined functional spine segment was evaluated, and the effect of the loading scenario determined for both vertebral bodies as well as the connecting intervertebral disc.
Kathleen J. Ashmen, C. Buz Swanik and Scott M. Lephart
The purpose of this study was to identify strength and flexibility deficits in subjects with chronic low-back pain (CLBP). Subjects were 16 female Division I athletes: 8 athletes who had experienced CLBP for at least 6 months prior to testing and a control group of 8 matched subjects. Athletes with neurological symptoms, previous back operations, and leg length discrepancies and those who were diagnosed with scoliosis, spondylolisthesis, or spondylolysis were excluded from this study. Variables assessed included abdominal strength, erector spinae endurance, hip flexion and extension endurance, torso lateral flexibility, and low-back flexibility. Strength and endurance were calculated as a function of time in seconds. Goniometric measurements were used to determine flexibility. Significant mean differences were found by using dependent t tests for abdominal strength, erector Spinae endurance, hip extension, and right lateral flexion of the torso. The results validate the necessity for pelvic stabilization and indicate that strength and flexibility deficits vary among populations.
Robert Rein, Chris Button, Keith Davids and Jeffery Summers
The present paper proposes a technical analysis method for extracting information about movement patterning in studies of motor control, based on a cluster analysis of movement kinematics. In a tutorial fashion, data from three different experiments are presented to exemplify and validate the technical method. When applied to three different basketball-shooting techniques, the method clearly distinguished between the different patterns. When applied to a cyclical wrist supination-pronation task, the cluster analysis provided the same results as an analysis using the conventional discrete relative phase measure. Finally, when analyzing throwing performance constrained by distance to target, the method grouped movement patterns together according to throwing distance. In conclusion, the proposed technical method provides a valuable tool to improve understanding of coordination and control in different movement models, including multiarticular actions.
Kathleen A. Swanik, C. Buz Swanik, Scott M. Lephart and Kellie Huxel
To determine whether functional training reduces the incidence of shoulder pain and increases strength in intercollegiate swimmers.
Laboratory and weight room.
26 intercollegiate swimmers (13 men, 13 women).
6-wk functional training program.
Main Outcome Measures:
Incidence of shoulder pain was recorded throughout the study. Isokinetic shoulder strength was assessed before and after training.
A t test showed significant differences (P < .05) for the incidence of shoulder pain between the experimental (mean episodes = 1.8 ± 2.1) and control (mean episodes = 4.6 ± 4.7) groups. ANOVA with repeated measures revealed no significant strength differences between groups but exhibited significant within-group increases.
Incorporating functional exercises might reduce incidence of shoulder pain in swimmers. The results also validate the need to modify preventive programs as the demands of the sport change throughout the season.
Possibilities and limitations in the biomechanical analysis of countermovement jump performance were examined using force plate data. Four male and 4 female sport students participated in the study. Software designed to test jumping performance was used to evaluate recordings from a force plate and to compute net velocity and net displacement measures for the center of gravity. In parallel, a film analysis incorporating Dempster's center of gravity model was used for a comparison. Validity of the computed kinetic measures was evaluated with a general analysis of the major error sources including the data acquisition and numerical computations. Numerical integration procedures were found to be a reasonable tool for calculating net velocity and net displacement parameters for a more detailed analysis of athletic jumping performance. On the other hand, it appeared that Dempster-like center of gravity models can cause errors that disqualify their use as validation criteria for kinetic parameters.
Hong-Wan Ng, Ee-Chon Teo and QingHang Zhang
Posterior decompressive techniques including one- and two-level laminotomies and laminectomies are often used in treating cervical stenosis. Previously, several in vitro studies were conducted to help us understand the biomechanical changes occurring in the cervical spine after these surgical techniques. However, changes in the intersegmental flexibility under combined flexion-extension remain unclear. In this study, a 3-D nonlinear intact model of the C2–C7 was developed to evaluate the influence of one- and two-level laminotomies and laminectomies on the intersegmental moment rotational responses and internal stresses. The intact model was validated by comparing the predicted responses against experimental data. The validated model was then modified to simulate various surgical techniques for finite element analysis. Results showed that one- and two-level laminectomies increase the C2–C7 rotation motions by about 15% and 20%, respectively. The predicted increase in rotational motions also correlated well with the published data. Furthermore, results indicated that laminectomies would influence the biomechanical responses on both the affected and adjacent motion segments. In contrast, laminotomies have no significant effects on cervical biomechanics. To conduct a one-level laminectomy study, current findings indicate that it takes at least five motion segments to capture the immediate postsurgical biomechanical changes accurately and realistically. Minimally invasive cervical spine surgeries with one- or two-level laminotomies are preferred over one- and two-level laminectomies. Also, there is no consideration as to the efficacy of the two techniques in decompressing the spinal cord or nerve roots, which is the goal of the surgery, but is not examined in this study.
Klaus Schneider and Ronald F. Zernicke
With a validated mathematical model of the head-neck consisting of nine rigid bodies (skull, seven cervical vertebrae, and torso), we simulated head impacts to estimate the injury risk associated with soccer heading. Experimental data from head-linear accelerations during soccer heading were used to validate the nine-body head-neck model for short duration impact loading of the head. In the computer simulations, the mass ratios between head mass and impacting body mass, the velocity of the impacting body, and the impact elasticity were varied. Head-linear and angular accelerations were compared to standard head-injury tolerance levels, and the injury risk specifically related to soccer heading was estimated. Based on our choice of tolerance levels in general, our simulations showed that injury risk from angular head accelerations was greater than from linear head accelerations, and compared to frontal impacts, lateral impacts had greater angular and less linear head accelerations. During soccer heading, our simulations indicated an unacceptable injury risk caused by angular head accelerations for frontal and lateral impacts at relatively low impact velocities for children, and at medium range impact velocities for adults. For linear head accelerations, injury risk existed for frontal and lateral impacts at medium range to relatively larger impact velocities for children, while no injury risk was shown for adults throughout the entire velocity range. For injury prevention, we suggest that head-injury risk can be reduced most substantially by increasing the mass ratio between head and impacting body. In soccer with children, the mass of the impacting body has to be adjusted to the reduced head mass of a child, that is, it must be clearly communicated to parents, coaches, and youngsters to only use smaller soccer balls.
Christopher Joyce, Angus Burnett and Miccal Matthews
No method currently exists to determine the location of the kick point during the golf swing. This study consisted of two phases. In the first phase, the static kick point of 10 drivers (having identical grip and head but fitted with shafts of differing mass and stiffness) was determined by two methods: (1) a visual method used by professional club fitters and (2) an algorithm using 3D locations of markers positioned on the golf club. Using level of agreement statistics, we showed the latter technique was a valid method to determine the location of the static kick point. In phase two, the validated method was used to determine the dynamic kick point during the golf swing. Twelve elite male golfers had three shots analyzed for two drivers fitted with stiff shafts of differing mass (56 g and 78 g). Excellent between-trial reliability was found for dynamic kick point location. Differences were found for dynamic kick point location when compared with static kick point location, as well as between-shaft and within-shaft. These findings have implications for future investigations examining the bending behavior of golf clubs, as well as being useful to examine relationships between properties of the shaft and launch parameters.