structures assessed. Whereas the current work evaluated arch stiffness, defined as the change in AHI due to the increase in load between sitting and standing conditions, Spurrs et al 6 obtained musculotendinous stiffness of the lower limb through the oscillation technique by performing an isometric
Felipe García-Pinillos, Carlos Lago-Fuentes, Pedro A. Latorre-Román, Antonio Pantoja-Vallejo and Rodrigo Ramirez-Campillo
Adam Beard, John Ashby, Ryan Chambers, Franck Brocherie and Grégoire P. Millet
-related parameters in world-level rugby union players during a preparation phase preceding an international competition. The main findings were that 4 RSH sessions over a 2-week shock microcycle preparation period resulted in greater improvements (ie, higher lower-limb repeated power output) than similar training in
Alan Barr and David Hawkins
An anatomical database was constructed containing three-dimensional geometric representations of the structures comprising the lower extremity. The database was constructed by digitizing 100 high-resolution digital photographic images supplied from the National Library of Medicine’s Visual Human Male (VHM) project. These images were taken of sequential transverse cross-sectional slices of the leg. Slices were located 1 cm apart between a location approximately 3 mm below the superior aspect of the ilium and approximately 2 mm below the distal end of the fibula. Image Tool Software (v. 2.0) was used to manually digitize the perimeters of muscles, tendons, and bones of the pelvis, thigh, and shank from the right leg of the VHM. Additionally, the perimeter of the leg and the inner aspect of the superficial fat layer were digitized. The pelvis was digitized as a hemi-pelvis. Tissue perimeters were characterized using between 10 and 151 nodes within each slice; the number of nodes varied depending on the tissue’s size. Transverse cross-sectional slice number, structure identification, node number, and the two-dimensional coordinates of each node were stored in a data file. The information contained in this file is unique and provides a database that researchers can use to investigate questions related to tissue anatomy and movement mechanics that cannot be considered using existing musculoskeletal data sets.
Margaret K.Y. Mak, Oron Levin, Joseph Mizrahi and Christina W.Y. Hui-Chan
Calculation of joint torques during the rising phase of sit-to-stand motion is in most cases indeterminate, due to the unknown thighs/chair reaction forces in addition to the other sources of uncertainties such as joint positioning and anthropometric data. In the present study we tested the reliability of computation of the joint torques from a five-segment model; we used force plate data of thighs/chair and feet/ground reaction forces, in addition to kinematic measurements. While solving for joint torques before and after seat-off, differences between model solutions and measured data were calculated and minimized using an iterative algorithm for the reestimation of joint positioning and anthropometric properties. The above method was demonstrated for a group of six normal elderly persons.
Yaara Nadiv, Ricki Vachbroit, Amit Gefen, David Elad, Uri Zaretsky, Dani Moran, Pinchas Halpern and Anat Ratnovsky
The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching.
Bruce Elliott, J. Robert Grove and Barry Gibson
Eight international baseball pitchers were filmed in a laboratory while throwing from a pitching rubber attached to a Kistler force platform. Following a warm-up, all subjects threw fastballs (FB) until two strike pitches were assessed by an umpire positioned behind the catcher for both wind-up and set pitching techniques. Subjects then followed the same procedures for curveball pitches (CB). Both vertical (Z) and horizontal (Y) ground reaction force (GRF) data were recorded. A shutter correlation pulse was encoded so the temporal data from the film could be synchronized with the kinetic data from the force platform. Analysis of variance was used to analyze differences in force data at selected points in both pitching actions for both techniques. Vertical and horizontal GRFs increased from the first balance position to maximum levels at the cocked position for both techniques. Nonsignificant changes in GRF then occurred between the cocked position and front-foot landing. The Z GRFs were similar throughout the pitching action but higher in magnitude for the CB compared to the FB. Mean resultant forces were similar for the three fastest FB pitchers when compared to the three slowest pitchers. However, the slower group produced their peak resultant force earlier in the action, thus reducing the ability to drive over a stabilized front leg.
Gunnar Andréasson and Lars Peterson
The dynamical behavior of sport shoes and surfaces has been measured and combined with a clinical study of injuries. The method used for the technical measurement has been the DIN Standard, and the clinical injury assessment has been obtained from several teams using different shoes and surfaces. The results point out that a dynamical spring constant can be used as a means of predicting potential athletic injuries. For the interaction between a shoe and surface the combined dynamical modulus may not exceed 3.2 MPa.
Stephanie Chester, Audrey Zucker-Levin, Daniel A. Melcher, Shelby A. Peel, Richard J. Bloomer and Max R. Paquette
The purpose of this study was to compare knee and hip joint kinematics previously associated with anterior knee pain and metabolic cost among conditions including treadmill running (TR), standard elliptical (SE), and lateral elliptical (LE) in healthy runners. Joint kinematics and metabolic parameters of 16 runners were collected during all 3 modalities using motion capture and a metabolic system, respectively. Sagittal knee range of motion (ROM) was greater in LE (P < .001) and SE (P < .001) compared with TR. Frontal and transverse plane hip ROM were greater in LE compared with SE (P < .001) and TR (P < .001). Contralateral pelvic drop ROM was smaller in SE compared with TR (P = .002) and LE (P = .005). Similar oxygen consumption was found during LE and TR (P = .39), but LE (P < .001) and TR (P < .001) required greater oxygen consumption than SE. Although LE yields similar metabolic cost to TR and produces hip kinematics that may help strengthen hip abductors, greater knee flexion and abduction during LE may increase symptoms in runners with anterior knee pain. The findings suggest that research on the implications of elliptical exercise for injured runners is needed.
Max R. Paquette, Audrey Zucker-Levin, Paul DeVita, Joseph Hoekstra and David Pearsall
The purpose of this study was to compare lower extremity joint angular position and muscle activity during elliptical exercise using different foot positions and also during exercise on a lateral elliptical trainer. Sixteen men exercised on a lateral elliptical and on a standard elliptical trainer using straight foot position, increased toe-out angle, and a wide step. Motion capture and electromyography systems were used to obtain 3D lower extremity joint kinematics and muscle activity, respectively. The lateral trainer produced greater sagittal and frontal plane knee range of motion (ROM), greater peak knee flexion and extension, and higher vastus medialis activation compared with other conditions (P < .05). Toe-out and wide step produced the greatest and smallest peak knee adduction angles, respectively (P < .05). The lateral trainer produced greater sagittal and frontal plane hip ROM and greater peak hip extension and flexion compared with all other conditions (P < .05). Toe-out angle produced the largest peak hip external rotation angle and lowest gluteus muscle activation (P < .05). Findings from this study indicate that standard elliptical exercise with wide step may place the knee joint in a desirable frontal plane angular position to reduce medial knee loads, and that lateral elliptical exercise could help improve quadriceps strength but could also lead to larger knee contact forces.
Renato Rodano and Roberto Squadrone
Stability and consistency is a critical aspect in joint kinetic measurements. By applying a statistical technique, called sequential estimation procedure, the aim of this work was to determine the minimum number of trials required to obtain a stable mean for peak hip, knee, and ankle moments and powers during vertical jump. Nine competitive track and field sprinters (21.7 ± 3.5 yrs, 177.6 ± 4.3 cm, 70.8 ± 3.6 kg) performed 5 series of 5 double-legged maximum-height countermovement vertical jumps. From force platform and kinematic data, moment and power output were calculated for hip, knee, and ankle joints. The sequential estimation procedure applied to these data revealed that at least a 12-trial protocol is needed to establish a true measure for all the selected parameters. The mean number of trials for each variable was greater than 8 and less than 13. When hip moments were excluded from the analysis, a 10-trial protocol could be sufficient to reach a stable mean. In conclusion. the results of this study gave statistical evidence for the need to adopt multiple-trial protocols in order to obtain a stable mean for joint kinetic data.