In the current study, we examined whether coupling influences resulting from unintended afference-based phase entrainment are affected by movement amplitude as such or by the amplitude relation between the limbs. We assessed entrainment strength by studying how passive movements of the contralateral hand influenced unimanual coordination with a metronome. Results showed that amplitude as such did not affect entrainment strength, whereas the amplitude relation between the hands did. Larger amplitudes of the passive hand relative to the active hand resulted in stronger entrainment. This dependence on relative amplitude implies that entrainment strength is not only based on the intensity of afferent signals generated in the entraining limb but also on the susceptibility of the entrained limb to these signals.
Betteco J. de Boer, C. (Lieke) E. Peper, Arne Ridderikhoff and Peter J. Beek
Timothy C. Mauntel, Eric G. Post, Darin A. Padua and David R. Bell
A disparity exists between the rates of male and female lower extremity injuries. One factor that may contribute to this disparity is high-risk biomechanical patterns that are commonly displayed by females. It is unknown what biomechanical differences exist between males and females during an overhead squat. This study compared lower extremity biomechanics during an overhead squat and ranges of motion between males and females. An electromagnetic motion tracking system interfaced with a force platform was used to quantify peak lower extremity kinematics and kinetics during the descent phase of each squat. Range of motion measurements were assessed with a standard goniometer. Differences between male and female kinematics, kinetics, and ranges of motion were identified with t tests. Males displayed greater peak knee valgus angle, peak hip flexion angle, peak vertical ground reaction forces, and peak hip extension moments. Males also displayed less active ankle dorsiflexion with the knee extended and hip internal and external rotation than females. No other differences were observed. The biomechanical differences between males and females during the overhead squat may result from differences in lower extremity ranges of motion. Therefore, sex-specific injury prevention programs should be developed to improve biomechanics and ranges of motion.
Ken A. McLachlan, Aron J. Murphy, Mark L. Watsford and Sven Rees
Two popular methods of assessing lower body musculotendinous stiffness include the hopping and oscillation tests. The disparity and paucity of reliability data prompted this investigation into leg musculotendinous stiffness (Kleg) and ankle musculotendinous stiffness (Kank) measures. Kleg and Kank were assessed on three separate occasions in 20 female subjects. Kleg was determined using bilateral hopping procedures conducted at 2.2 Hz and 3.2 Hz frequencies. Kank was assessed by perturbation of the subject's ankle musculotendinous unit on an instrumented calf raise apparatus at 70% of maximum isometric force (MIF). Excellent reliability was produced for all Kleg measures between all days, whereas Kank exhibited acceptable reliability after one session of familiarization. No relationship was evident between Kleg and Kank. It was concluded that no familiarization session was required for Kleg at the test frequencies and conditions tested, whereas at least one familiarization session was needed to ensure the reliable assessment of Kank.
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.
Christopher A. Miller, Alan H. Feiveson and Jacob J. Bloomberg
Gait kinematics have been shown to vary with speed and visual-target fixation distance, but their combined effects on toe trajectory during treadmill walking are not known. The purpose of this investigation was to determine the role of walking speed and target distance on vertical toe trajectory during treadmill walking. Subjects walked on a treadmill at five speeds while performing a dynamic visual-acuity task at both “far” and “near” target distances (ten trials total). The analysis concentrated on three specific toe trajectory events during swing: the first peak toe height just after toe-off; the minimum toe height (toe clearance), and the second peak toe height just before heel strike. With increasing speed, toe clearance decreased and the peak toe height just before heel strike increased. Only the peak toe height just after toe-off was significantly changed between the near-target and far-target tasks, though the difference was small. Therefore, walking speed and visual-fixation distance cannot be neglected in the analysis of toe trajectory. Otherwise, differences observed between populations may be attributed to age- or clinically related factors, instead of disparities of speed or target-fixation distance.
Sarah Shaw, Tina Smith, Jenny Alexanders, Thomas Shaw, Lois Smith, Alan Nevill and Anna Anderson
To investigate half-marathon runners’ frequency of use of recovery strategies, perceptions regarding the most beneficial recovery strategy, and reasons for using recovery strategies.
186 participants of the 13.1 mile BUPA Great North Run 2013.
A questionnaire was developed which required participants to indicate how frequently they used 12 different recovery strategies, identify which recovery strategy they believed to be most beneficial, and rank 6 reasons for using recovery strategies in order of importance. Data were analyzed using a Friedman nonparametric ANOVA and additional nonparametric tests.
All participants used recovery strategies. Stretching was the most commonly used recovery strategy (P < .001), whereas the use of nutritional supplements was the most commonly selected most beneficial recovery strategy. More than 50% of respondents indicated that they never used strategies such as kinesio tape (80%), hydrotherapy (78%), or ice baths (71%). A significant difference was observed between reasons for using recovery strategy (χ2 (5) = 292.29, P < .001). Reducing muscle tightness (rank 4.87) and reducing injury (rank 4.35) were the most frequently chosen most important reasons for using recovery strategies. Minor sex and age differences in the responses were identified.
Recovery strategy usage appears to be widespread among half-marathon runners; however, disparities exist between the frequency of use and perceived effectiveness of different recovery strategies. Further research in this area is needed to facilitate the development of recovery strategy guidelines which are both evidence-based and practically relevant.
Chelsey Klimek, Christopher Ashbeck, Alexander J. Brook and Chris Durall
the injury rate was higher in the Hak et al’s 4 study, although differences in sample size and/or response bias may explain some of the disparity between these studies. Differences in CrossFit experience between the reviewed studies may also explain some of the disparities in injury rates. Weisenthal
Lauren Anne Lipker, Caitlyn Rae Persinger, Bradley Steven Michalko and Christopher J. Durall
, whereas the third study found no between-group differences in atrophic changes. 1 , 2 , 4 This disparity in outcomes may be due to a variety of factors including but not limited to, cuff size, occlusive pressure, individual treatment session duration, and length of the intervention period. For instance
Erica M. Willadsen, Andrea B. Zahn and Chris J. Durall
the training protocols between these studies may have contributed to the disparity in outcomes. It is also plausible that the impact of core stability training on landing knee valgus angulation is nominal. Core stability training also produced conflicting results between the reviewed studies for
John J. Fraser and Jay Hertel
pretreatment to posttreatment in 2 of the 3 IFM exercises. Delignières and Brisswalter 35 described a disparity between perceived effort and physical performance. They postulate that perceived difficulty is more determined by a participant’s personality, self-esteem, self-confidence, and aspiration rather