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INTRODUCTION: Neuromuscular warm-up programs, such as FIFA 11+ were developed as early as 2006. These programs have been effective in reducing the risk of injury in female athletes by decreasing the moments surrounding the knee and improving neuromuscular control during static and dynamic movements such as jumping and landing. In addition, they have been effective for improving jump height in soccer, volleyball, and basketball. METHODS: The effects of the 11+ Dance, a dance-specific neuromuscular warm-up program, was examined on jump height and lower extremity biomechanics during bilateral and single leg countermovement jumps in recreational dancers. Twenty female adolescents from 2 dance schools participated in this 2-centered 8-week controlled non-randomized trial. The intervention group (IG) performed the 11+ Dance program 3×/week for 8-weeks during the first 30-minute of their regularly scheduled dance classes. The control group (CG) continued with their regular dance classes routine. Ground reaction force and motion capture data were used to assess jump height and lower extremity biomechanics pre and post intervention. RESULTS: Both groups statistically increased their jump height (CG: Z = 1.89-2.45, P ≤ .0167; IG: Z = 2.18-2.76, P ≤ .0167). However, no statistical between group differences were observed (Z = 0.38-1.22, P > .05). During takeoff, the IG statistically reduced peak knee extension moments (t(18) = -3.04 to -3.77, P ≤ .0167) while increasing peak hip extension moments (t(18) = 2.16-2.79, P ≤ .05) and peak hip flexion angles (t(18) = 2.68-3.72, P ≤ .0167) compared to the CG. The IG also increased the hip flexion angles compared to the CG during landing (t(18) = 2.78-5.13, P ≤ .0167) while no systematic differences were observed in all other variables of lower extremity biomechanics. CONCLUSION: The reduced joint load at the knee observed during takeoff needs further investigation. Neuromuscular training, such as the 11+ Dance, is supported by numerous quality research. Due to its simplicity, the 11+ Dance may be feasible and beneficial to complement regular warm-ups in recreational dance practice.

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Humans often move in the presence of mechanical disturbances that can vary in direction and amplitude throughout movement. These disturbances can jeopardize the outcomes of our actions, such as when drinking from a glass of water on a turbulent flight or carrying a cup of coffee while walking on a busy sidewalk. Here, we examine control strategies that allow the nervous system to maintain performance when reaching in the presence of mechanical disturbances that vary randomly throughout movement. Healthy participants altered their control strategies to make movements more robust against disturbances. The change in control was associated with faster reaching movements and increased responses to proprioceptive and visual feedback that were tuned to the variability of the disturbances. Our findings highlight that the nervous system exploits a continuum of control strategies to increase its responsiveness to sensory feedback when reaching in the presence of increasingly variable physical disturbances.

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The contextual-interference effect is a frequently examined phenomenon in motor skill learning but has not been extensively investigated in motor adaptation. Here, we first tested experimentally if the contextual-interference effect is detectable in force field adaptation regarding retention and spatial transfer, and then fitted state-space models to the data to relate the findings to the "forgetting-and-reconstruction hypothesis". Thirty-two participants were divided into two groups with either a random or a blocked practice schedule. They practiced reaching to four targets and were tested 10 min and 24 h afterward for motor retention and spatial transfer on an interpolation and an extrapolation target, and on targets which were shifted 10 cm away. The adaptation progress was participant-specifically fitted with 4-slow-1-fast state-space models accounting for generalization and set breaks. The blocked group adapted faster (p = 0.007) but did not reach a better adaptation at practice end. We found better retention (10 min), interpolation transfer (10 min), and transfer to shifted targets (10 min and 24 h) for the random group (each p < 0.05). However, no differences were found for retention or for the interpolation target after 24 h. Neither group showed transfer to the extrapolation target. The extended state-space model could replicate the behavioral results with some exceptions. The study shows that the contextual-interference effect is partially detectable in practice, short-term retention, and spatial transfer in force field adaptation; and that state-space models provide explanatory descriptions for the contextual-interference effect in force field adaptation.

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Limb dominance is evident in many daily activities, leading to the prominent idea that each hemisphere of the brain specializes in controlling different aspects of movement. Past studies suggest that the dominant arm is primarily controlled via an internal model of limb dynamics that enables the nervous system to produce efficient movements. In contrast, the nondominant arm may be primarily controlled via impedance mechanisms that rely on the strong modulation of sensory feedback from individual joints to control limb posture. We tested whether such differences are evident in behavioral responses and stretch reflexes following sudden displacement of the arm during posture control. Experiment 1 applied specific combinations of elbow-shoulder torque perturbations (the same for all participants). Peak joint displacements, return times, end point accuracy, and the directional tuning and amplitude of stretch reflexes in nearly all muscles were not statistically different between the two arms. Experiment 2 induced specific combinations of joint motion (the same for all participants). Again, peak joint displacements, return times, end point accuracy, and the directional tuning and amplitude of stretch reflexes in nearly all muscles did not differ statistically when countering the imposed loads with each arm. Moderate to strong correlations were found between stretch reflexes and behavioral responses to the perturbations with the two arms across both experiments. Collectively, the results do not support the idea that the dominant arm specializes in exploiting internal models and the nondominant arm in impedance control by increasing reflex gains to counter sudden loads imposed on the arms during posture control.NEW & NOTEWORTHY A prominent hypothesis is that the nervous system controls the dominant arm through predictive internal models and the nondominant arm through impedance mechanisms. We tested whether stretch reflexes of muscles in the two arms also display such specialization during posture control. Nearly all behavioral responses and stretch reflexes did not differ statistically but were strongly correlated between the arms. The results indicate individual signatures of feedback control that are common for the two arms.

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Increased involvement of the hip musculature during some movements is associated with enhanced performance and reduced injury risk. However, the impact of hip dominant weight training methods on movement strategy has seen limited attention within the literature. The aim of this study was to evaluate if a 9-week hip dominant weight training intervention promotes a more hip dominant movement strategy leading to an improvement in countermovement jump performance. Twenty-two experienced female dancers were recruited and separated into an intervention (age 24.4 ± 6.3 years, body height 165.5 ± 5.8 cm, body mass 65.9 ± 5.6 kg) and a control (age 22.9 ± 5.6 years, body height 163.3 ± 5.4 cm, body mass 57.4 ± 6.8 kg) group. The intervention group participated in a 9-week hip dominant training intervention, which consisted of a wide stance back squat, Romanian deadlift, hip thrusters, and a bent over row. Hip and knee kinematics and kinetics, and countermovement jump performance were assessed pre and post training. Significant interaction effects were found for peak hip joint moment (p = 0.030, η2 = 0.214) and countermovement jump performance (p = 0.003, η2 = 0.356), indicating an increase in peak hip joint moment and countermovement jump performance for the intervention group. Specifically, the intervention group showed a mean increase in jump height of 11.5%. The data show that the use of a hip dominant weight training strategy can improve hip contribution in the propulsion phase of the countermovement jump. Strength and conditioning specialists should incorporate hip dominant weight training exercises to increase hip strength and improve performance.

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BACKGROUND: Motor assessments are important to determine effectiveness of physical activity in individuals with dementia (IWD). However, inappropriate and non-standardised assessments without sound psychometric properties have been used. This systematic review aims to examine psychometric properties of motor assessments in IWD combined with frequency of use and effect sizes and to provide recommendations based on observed findings.We performed a two-stage systematic literature search using Pubmed, Web of Science, Cochrane Library, ALOIS, and Scopus (inception - July/September 2018, English and German). The first search purposed to identify motor assessments used in randomised controlled trials assessing effectiveness of physical activity in IWD and to display their frequency of use and effect sizes. The second search focused on psychometric properties considering influence of severity and aetiology of dementia and cueing on test-retest reliability. Two reviewers independently extracted and analysed findings of eligible studies in a narrative synthesis. RESULTS: Literature searches identified 46 randomised controlled trials and 21 psychometric property studies. While insufficient information was available for validity, we observed sufficient inter-rater and relative test-retest reliability but unacceptable absolute test-retest reliability for most assessments. Combining these findings with frequency of use and effect sizes, we recommend Functional Reach Test, Groningen Meander Walking Test (time), Berg Balance Scale, Performance Oriented Mobility Assessment, Timed Up & Go Test, instrumented gait analysis (spatiotemporal parameters), Sit-to-Stand assessments (repetitions> 1), and 6-min walk test. It is important to consider that severity and aetiology of dementia and cueing influenced test-retest reliability of some assessments. CONCLUSION: This review establishes an important foundation for future investigations. Sufficient relative reliability supports the conclusiveness of recommended assessments at group level, while unacceptable absolute reliability advices caution in assessing intra-individual changes. Moreover, influences on test-retest reliability suggest tailoring assessments and instructions to IWD and applying cueing only where it is inevitable. Considering heterogeneity of included studies and insufficient examination in various areas, these recommendations are not comprehensive. Further research, especially on validity and influences on test-retest reliability, as well as standardisation and development of tailored assessments for IWD is crucial.This systematic review was registered in PROSPERO (CRD42018105399).

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Lateral ankle stability and how it changes in different footwear has been investigated for years. Research, however, has shown a lack of reliability or sensitivity of available methodologies. This study aimed to evaluate the test-retest reliability and sensitivity of a novel lateral stability protocol, the Submaximal Lateral Shuffle Test (SLST). We recruited 11 and 40 participants to assess reliability and sensitivity of the SLST, respectively. Participants performed the SLST in footwear that differed in collar height and upper stiffness. ICC values showed good to excellent reliability in peak ankle angles and moments, ground reaction forces, impulses, stance time, and performance time. Significantly lower peak inversion and adduction angles and lower medio-lateral push off peak forces were found in the high cut shoes compared to the low cut shoes. The medio-lateral landing peak force showed lower forces in the high cut shoes. The smallest worthwhile change indicated meaningful differences in 70.0-82.5% of participants for inversion, adduction, medio-lateral landing peak, and push off peak forces. These results, however, were not systematic such that there was not a consistent direction of the difference for all participants. In conclusion, the SLST is a promising protocol to further investigate lateral stability in footwear.

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