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Logan A. Lucas, Benjamin S. England, Travis W. Mason, Christopher R. Lanning, Taylor M. Miller, Alexander M. Morgan and Thomas Gus Almonroeder

3 times an athlete’s body weight. 7 These impact forces generate a transient spike in acceleration which is transmitted throughout the musculoskeletal system from the foot to the head. 8 Although the lower-extremity musculature can help to attenuate these impact accelerations, passive tissues also

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Oren Tirosh, Guy Orland, Alon Eliakim, Dan Nemet and Nili Steinberg

stride length and moderately with stride frequency. 3 These findings are expected because tibia peak positive acceleration was found to increase with speed 3 , 4 while the body was found to respond to varying impact situations and sufficiently attenuate the impact shock to maintain constant head

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Ryu Nagahara, Mirai Mizutani, Akifumi Matsuo, Hiroaki Kanehisa and Tetsuo Fukunaga

preceding acceleration. In contrast, Morin et al 6 and Rabita et al 8 found no significant relationship between averaged vertical force or impulse over a 40-m distance and either maximal speed or mean running speed over 40 m. They demonstrated that a larger propulsive force or impulse during the

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Lydia R. Vollavanh, Kathleen M. O’Day, Elizabeth M. Koehling, James M. May, Katherine M. Breedlove, Evan L. Breedlove, Eric A. Nauman, Debbie A. Bradney, J. Eric Goff and Thomas G. Bowman

rotational accelerations based on player position, event type, and location of impact in football. 7 , 16 Researchers also noted differences in mechanism, event type, and location of impact in youth and collegiate ice hockey. 4 , 14 To date, research into head impacts in men’s lacrosse is limited. 25 The

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Michelle A. Sandrey, Yu-Jen Chang and Jean L. McCrory

activated during a jumping task. Repetitive impacts from vertical jump landings in jumping sport athletes have been associated with injury, as the musculoskeletal system must attenuate the mechanical shock during contact. 7 , 8 Elevated peak tibial accelerations (TAs) values might, therefore, indicate an

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Adriana M. Duquette and David M. Andrews

Considerable variability in tibial acceleration slope (AS) values, and different interpretations of injury risk based on these values, have been reported. Acceleration slope variability may be due in part to variations in the quantification methods used. Therefore, the purpose of this study was to quantify differences in tibial AS values determined using end points at various percentage ranges between impact and peak tibial acceleration, as a function of either amplitude or time. Tibial accelerations were recorded from 20 participants (21.8 ± 2.9 years, 1.7 m ± 0.1 m, 75.1 kg ± 17.0 kg) during 24 unshod heel impacts using a human pendulum apparatus. Nine ranges were tested from 5–95% (widest range) to 45–55% (narrowest range) at 5% increments. ASAmplitude values increased consistently from the widest to narrowest ranges, whereas the ASTime values remained essentially the same. The magnitudes of ASAmplitude values were significantly higher and more sensitive to changes in percentage range than ASTime values derived from the same impact data. This study shows that tibial AS magnitudes are highly dependent on the method used to calculate them. Researchers are encouraged to carefully consider the method they use to calculate AS so that equivalent comparisons and assessments of injury risk across studies can be made.

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Ewald M. Hennig and Mario A. Lafortune

Using data from six male subjects, this study compared ground reaction force and tibial acceleration parameters for running. A bone-mounted triaxial accelerometer and a force platform were employed for data collection. Low peak values were found for the axial acceleration, and a time shift toward the occurrence of the first peak in the vertical force data was present. The time to peak axial acceleration differed significantly from the time to the first force peak, and the peak values of force and acceleration demonstrated only a moderate correlation. However, a high negative correlation was found for the comparison of the peak axial acceleration with the time to peak vertical force. Employing a multiple regression analysis, the peak tibial acceleration could be well estimated using vertical force loading rate and peak horizontal ground reaction force as predictors.

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Erin M.R. Bigelow, Niell G. Elvin, Alex A. Elvin and Steven P. Arnoczky

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time. The accelerometer was attached to a custom-made acrylic plate and secured at the level of the L5 vertebra via a tight fitting triathlon belt. Each subject ran 4 miles on a synthetic, indoor track at a self-selected pace and accelerations were recorded on three perpendicular axes. Seven days later, the subjects ran 4 miles on a treadmill set at the individual runner’s average pace on the track and the peak vertical and horizontal impact magnitudes between the track and treadmill were compared. There was no difference (P = .52) in the average peak vertical impact accelerations between the track and treadmill over the 4 mile run. However, peak horizontal impact accelerations were greater (P = .0012) on the track when compared with the treadmill. This study demonstrated the feasibility for long-term impact accelerations monitoring using a novel wireless accelerometer.

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Alison Schinkel-Ivy, Timothy A. Burkhart and David M. Andrews

To date, there has not been a direct examination of the effect that tissue composition (lean mass/muscle, fat mass, bone mineral content) differences between males and females has on how the tibia responds to impacts similar to those seen during running. To evaluate this, controlled heel impacts were imparted to 36 participants (6 M and 6 F in each of low, medium and high percent body fat [BF] groups) using a human pendulum. A skin-mounted accelerometer medial to the tibial tuberosity was used to determine the tibial response parameters (peak acceleration, acceleration slope and time to peak acceleration). There were no consistent effects of BF or specific tissue masses on the un-normalized tibial response parameters. However, females experienced 25% greater peak acceleration than males. When normalized to lean mass, wobbling mass, and bone mineral content, females experienced 50%, 62% and 70% greater peak acceleration, respectively, per gram of tissue than males. Higher magnitudes of lean mass and bone mass significantly contributed to decreased acceleration responses in general.

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Joseph J. Crisco, Laura Costa, Ryan Rich, Joel B. Schwartz and Bethany Wilcox

Girls’ lacrosse is fundamentally a different sport than boys’ lacrosse, and girls are not required to wear protective headgear. Recent epidemiological studies have found that stick checks are the leading cause of concussion injury in girls’ lacrosse. The purpose of this study was to determine stick check speeds and estimate the head acceleration associated with direct checks to the head. In addition, we briefly examine if commercially available headgear can mitigate the accelerations. Seven (n = 7) experienced female lacrosse players checked, with varying severity, a NOSCAE and an ASTM headform. Stick speed at impact and the associated peak linear accelerations of the headform were recorded. The NOCSAE headform was fitted with four commercially available headgear and similar stick impact testing was performed. The median stick impact speed was 8.1 m/s and 777 deg/s. At these speeds, peak linear acceleration was approximately 60g. Three out of the four headgear significantly reduced the peak linear acceleration when compared with the bare headform. These data serve as baseline for understanding the potential mechanism and reduction of concussions from stick impacts in girls’ lacrosse.