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Patrick F. Curran, Russell D. Fiore and Joseph J. Crisco

Context:

Self-myofascial release (SMR) is a technique used to treat myofascial restrictions and restore soft-tissue extensibility.

Purpose:

To determine whether the pressure and contact area on the lateral thigh differ between a Multilevel rigid roller (MRR) and a Bio-Foam roller (BFR) for participants performing SMR.

Participants:

Ten healthy young men and women.

Methods:

Participants performed an SMR technique on the lateral thigh using both myofascial rollers. Thin-film pressure sensels recorded pressure and contact area during each SMR trial.

Results:

Mean sensel pressure exerted on the soft tissue of the lateral thigh by the MRR (51.8 ± 10.7 kPa) was significantly (P < .001) greater than that of the conventional BFR (33.4 ± 6.4 kPa). Mean contact area of the MRR (47.0 ± 16.1 cm2) was significantly (P < .005) less than that of the BFR (68.4 ± 25.3 cm2).

Conclusion:

The significantly higher pressure and isolated contact area with the MRR suggest a potential benefit in SMR.

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William L. Siler and Philip E. Martin

In order to compare fast and slow runners with respect to the relative timing of the compensations they make to maintain a given running velocity during a prolonged effort, coordinate data were collected periodically for 9 fast and 10 slow volunteers performing a treadmill run to volitional exhaustion at a speed approximating their 10-km race pace. Statistically significant but small changes were noted in the average stride length, range of motion at the thigh, maximum thigh flexion, maximum knee extension, maximum knee flexion, and head-neck-trunk segment (HNT) angle at maximum thigh extension. No statistically significant differences were detected, however, with regard to the relative timing of the compensations demonstrated by the two groups. It was concluded that runners demonstrate subtle compensations in running pattern as they approach volitional exhaustion. In addition, it was concluded that the performance level of the runners as reflected by the ranges of 10-km run performance used in this investigation does not affect the relative timing of the compensations. Finally, it appears that some individuals are more sensitive to the effects of fatigue as evidenced by extreme compensations in running pattern.

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Layci J. Harrison, Kala L. Young, Sandra L. Stevens and Jennifer L. Caputo

A 19-year-old collegiate softball player collided with a fence while trying to catch a fly ball, resulting in a greenstick fibular fracture. Underwater treadmill training (UTT) was used as a modality to supplement traditional physical therapy (TPT). Active range of motion (AROM) in all directions for the knee, hip, and ankle, girth of the thigh and lower leg, static balance, and 6-Minute Walk Test (6MWT) distance were assessed pre- and postintervention. The addition of UTT to TPT led to postintervention increases in AROM, static balance, and limb girth, with no additional discomfort to the participant.

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Emma Fortune, Melissa M.B. Morrow and Kenton R. Kaufman

Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations, and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 [19–34] years) performed 8–10 walking trials at velocities ranging from 0.19 to 3.05 m/s while wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r 2 > .53, P < .001), ankle peak vertical accelerations were the most correlated (r 2 > .75, P < .001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r 2 > .57, P < .001), with waist peak resultant acceleration being the most correlated (r 2 > .70, P < .001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health.

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Jun Yuda, Masahiro Yuki, Toru Aoyanagi, Norihisa Fujii and Michiyoshi Ae

The purpose of this study was to investigate technical factors for maintaining skating velocity by kinematic analysis of the skating motion for elite long-distance skaters during the curve phase in official championship races. Sixteen world-class elite male skaters who participated in the 5,000-m race were videotaped with two synchronized high-speed video cameras (250 Hz) in a curve lane by using a panning DLT technique. Three-dimensional coordinates of the body and blades during the first and second halves of the races were collected to calculate kinematic parameters. In the group that maintained greater skating velocity, the thigh angle during the gliding phase of the left stroke during the second half was greater than that during the first half, and the center of mass was located more forward during the second half. Thus, it was suggested that long-distance speed skaters should change the support leg position during the gliding phase in the left stroke of the curve phase under fatigued conditions so that they could extend the support leg with a forward rotation of the thigh and less shank backward rotation.

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Loren Z.F. Chiu and Amy N. Moolyk

Joint kinematics differ between jump and drop landings and there is evidence that segment kinematics may also be different. The purpose of this research was to compare lower extremity segment kinematics for jump and drop landings, and to examine if multiple days of practice would influence these kinematics. Men (n = 9) and women (n = 15) performed 4 sessions of jump and drop landings (40 cm and 60 cm) in a motion-capture laboratory. Segment kinematics at initial contact, foot flat, and peak knee flexion were compared between landing types and across visits. At initial contact, foot plantar flexion was greater in jump versus drop landings (P < .05). At initial contact and foot flat, forward leg inclination and pelvis flexion were greater in jump landing (P < .05), while thigh flexion was greater in drop landings (P > .05). The differences in leg and thigh angles at initial contact and foot flat altered lower extremity posture. These results are in contrast to a previous study; this suggests that drop landing can be modified to have the same mechanics as jump landing. As practice did not influence drop landing mechanics (P > .05), specific control strategies and instructions need to be identified.

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Stine Kloster, Ida Høgstedt Danquah, Andreas Holtermann, Mette Aadahl and Janne Schurmann Tolstrup

Background:

Harmful health effects associated with sedentary behavior may be attenuated by breaking up long periods of sitting by standing or walking. However, studies assess interruptions in sitting time differently, making comparisons between studies difficult. It has not previously been described how the definition of minimum break duration affects sitting outcomes. Therefore, the aim was to address how definitions of break length affect total sitting time, number of sit-to-stand transitions, prolonged sitting periods and time accumulated in prolonged sitting periods among office workers.

Methods:

Data were collected from 317 office workers. Thigh position was assessed with an ActiGraph GT3X+ fixed on the right thigh. Data were exported with varying bout length of breaks. Afterward, sitting outcomes were calculated for the respective break lengths.

Results:

Absolute numbers of sit-to-stand transitions decreased, and number of prolonged sitting periods and total time accumulated in prolonged sitting periods increased, with increasing minimum break length. Total sitting time was not influenced by varying break length.

Conclusions:

The definition of minimum break length influenced the sitting outcomes with the exception of total sitting time. A standard definition of break length is needed for comparison and interpretation of studies in the evolving research field of sedentary behavior.

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Niell G. Elvin, Alex A. Elvin, Steven P. Arnoczky and Michael R. Torry

Impact forces and shock deceleration during jumping and running have been associated with various knee injury etiologies. This study investigates the influence of jump height and knee contact angle on peak ground reaction force and segment axial accelerations. Ground reaction force, segment axial acceleration, and knee angles were measured for 6 male subjects during vertical jumping. A simple spring-mass model is used to predict the landing stiffness at impact as a function of (1) jump height, (2) peak impact force, (3) peak tibial axial acceleration, (4) peak thigh axial acceleration, and (5) peak trunk axial acceleration. Using a nonlinear least square fit, a strong (r = 0.86) and significant (p ≤ 0.05) correlation was found between knee contact angle and stiffness calculated using the peak impact force and jump height. The same model also showed that the correlation was strong (r = 0.81) and significant (p ≤ 0.05) between knee contact angle and stiffness calculated from the peak trunk axial accelerations. The correlation was weaker for the peak thigh (r = 0.71) and tibial (r = 0.45) axial accelerations. Using the peak force but neglecting jump height in the model, produces significantly worse correlation (r = 0.58). It was concluded that knee contact angle significantly influences both peak ground reaction forces and segment accelerations. However, owing to the nonlinear relationship, peak forces and segment accelerations change more rapidly at smaller knee flexion angles (i.e., close to full extension) than at greater knee flexion angles.

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Jørgen Skotte, Mette Korshøj, Jesper Kristiansen, Christiana Hanisch and Andreas Holtermann

Background:

The aim of this study was to validate a triaxial accelerometer setup for identifying everyday physical activity types (ie, sitting, standing, walking, walking stairs, running, and cycling).

Methods:

Seventeen subjects equipped with triaxial accelerometers (ActiGraph GT3X+) at the thigh and hip carried out a standardized test procedure including walking, running, cycling, walking stairs, sitting, and standing still. A method was developed (Acti4) to discriminate between these physical activity types based on threshold values of standard deviation of acceleration and the derived inclination. Moreover, the ability of the accelerometer placed at the thigh to detect sitting posture was separately validated during free living by comparison with recordings of pressure sensors in the hip pockets.

Results:

Sensitivity for discriminating between the physical activity types sitting, standing, walking, running, and cycling in the standardized trials were 99%–100% and 95% for walking stairs. Specificity was higher than 99% for all activities. During free living (140 hours of measurements), sensitivity and specificity for detection of sitting posture were 98% and 93%, respectively.

Conclusion:

The developed method for detecting physical activity types showed a high sensitivity and specificity for sitting, standing, walking, running, walking stairs, and cycling in a standardized setting and for sitting posture during free living.

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Jeffrey D. Holmes, David M. Andrews, Jennifer L. Durkin and James J. Dowling

The purpose of this study was to derive and validate regression equations for the prediction of fat mass (FM), lean mass (LM), wobbling mass (WM), and bone mineral content (BMC) of the thigh, leg, and leg + foot segments of living people from easily measured segmental anthropometric measures. The segment masses of 68 university-age participants (26 M, 42 F) were obtained from full-body dual photon x-ray absorptiometry (DXA) scans, and were used as the criterion values against which predicted masses were compared. Comprehensive anthropometric measures (6 lengths, 6 circumferences, 8 breadths, 4 skinfolds) were taken bilaterally for the thigh and leg for each person. Stepwise multiple linear regression was used to derive a prediction equation for each mass type and segment. Prediction equations exhibited high adjusted R 2 values in general (0.673 to 0.925), with higher correlations evident for the LM and WM equations than for FM and BMC. Predicted (equations) and measured (DXA) segment LM and WM were also found to be highly correlated (R 2 = 0.85 to 0.96), and FM and BMC to a lesser extent (R 2 = 0.49 to 0.78). Relative errors between predicted and measured masses ranged between 0.7% and –11.3% for all those in the validation sample (n = 16). These results on university-age men and women are encouraging and suggest that in vivo estimates of the soft tissue masses of the lower extremity can be made fairly accurately from simple segmental anthropometric measures.