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Does sports-specific training improve measures of impairment developed for para sport classification? A multiple-baseline, single-case experiment.
Wilson, PJ, Connick, MJ, Dutia, IM, Beckman, EM, Macaro, A, Tweedy, SM
Journal of sports sciences. 2021;(sup1):81-90
Abstract
Conceptually, sports-specific training should not influence measures of impairment used to classify Para athletes. This study evaluated the extent to which measures of strength, range of movement and coordination developed for Para swimming classification changed in response to a performance-focused swimming programme. A five-phase multiple-baseline, single-case experimental research design was utilized. Three participants with cerebral palsy and high support needs completed the 64-week study, which included two 16-week performance-focused swimming training blocks. Swimming speed, isometric shoulder extension strength, shoulder flexion range of movement and upper limb coordination were monitored throughout.Interrupted Time-Series Simulation Method analysis demonstrated large, significant changes in swimming speed (m/s) during the first (d = 2.17; 95% CI 0.45-3.88; p = 0.01) and second (d = 2.59; 95% CI 1.66-3.52; p = 0.00) training blocks. In contrast, changes in strength, range of movement and coordination were predominantly trivial and non-significant. This was the first study to investigate training responsiveness of measures developed for Para sport classification. Results indicate that despite significantly improved swimming performance, impairment measures remained relatively stable, and therefore these measures of impairment may be valid for the purposes of Para swimming classification. Further research is required in elite athletes, different sports and different impairment types.
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The impact of beetroot juice supplementation on muscular endurance, maximal strength and countermovement jump performance.
Jonvik, KL, Hoogervorst, D, Peelen, HB, de Niet, M, Verdijk, LB, van Loon, LJC, van Dijk, JW
European journal of sport science. 2021;(6):871-878
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Abstract
Purpose: Dietary nitrate has been shown to enhance muscle contractile function and has, therefore, been linked to increased muscle power and sprint exercise performance. However, the impact of dietary nitrate supplementation on maximal strength, performance and muscular endurance remains to be established. Methods: Fifteen recreationally active males (25 ± 4 y, BMI 24 ± 3 kg/m2) participated in a randomized double-blinded cross-over study comprising two 6-d supplementation periods; 140 mL/d nitrate-rich (BR; 985 mg/d) and nitrate-depleted (PLA; 0.37 mg/d) beetroot juice. Three hours following the last supplement, we assessed countermovement jump (CMJ) performance, maximal strength and power of the upper leg by voluntary isometric (30° and 60° angle) and isokinetic contractions (60, 120, 180 and 300°·s-1), and muscular endurance (total workload) by 30 reciprocal isokinetic voluntary contractions at 180°·s-1. Results: Despite differences in plasma nitrate (BR: 879 ± 239 vs. PLA: 33 ± 13 μmol/L, P < 0.001) and nitrite (BR: 463 ± 217 vs. PLA: 176 ± 50 nmol/L, P < 0.001) concentrations prior to exercise testing, CMJ height (BR: 39.3 ± 6.3 vs. PLA: 39.6 ± 6.3 cm; P = 0.39) and muscular endurance (BR: 3.93 ± 0.69 vs. PLA: 3.90 ± 0.66 kJ; P = 0.74) were not different between treatments. In line, isometric strength (P > 0.50 for both angles) and isokinetic knee extension power (P > 0.33 for all velocities) did not differ between treatments. Isokinetic knee flexion power was significantly higher following BR compared with PLA ingestion at 60°·s-1 (P = 0.001), but not at 120°·s-1 (P = 0.24), 180°·s-1 (P = 0.066), and 300°·s-1 (P = 0.36). Conclusion: Nitrate supplementation does not improve maximal strength, countermovement jump performance and muscular endurance in healthy, active males.
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Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans.
Lockyer, EJ, Compton, CT, Forman, DA, Pearcey, GE, Button, DC, Power, KE
Journal of neurophysiology. 2021;(1):181-194
Abstract
The use of transcranial magnetic stimulation to assess the excitability of the central nervous system to further understand the neural control of human movement is expansive. The majority of the work performed to-date has assessed corticospinal excitability either at rest or during relatively simple isometric contractions. The results from this work are not easily extrapolated to rhythmic, dynamic motor outputs, given that corticospinal excitability is task-, phase-, intensity-, direction-, and muscle-dependent (Power KE, Lockyer EJ, Forman DA, Button DC. Appl Physiol Nutr Metab 43: 1176-1185, 2018). Assessing corticospinal excitability during rhythmic motor output, however, involves technical challenges that are to be overcome, or at the minimum considered, when attempting to design experiments and interpret the physiological relevance of the results. The purpose of this narrative review is to highlight the research examining corticospinal excitability during a rhythmic motor output and, importantly, to provide recommendations regarding the many factors that must be considered when designing and interpreting findings from studies that involve limb movement. To do so, the majority of work described herein refers to work performed using arm cycling (arm pedaling or arm cranking) as a model of a rhythmic motor output used to examine the neural control of human locomotion.
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The energetic basis for smooth human arm movements.
Wong, JD, Cluff, T, Kuo, AD
eLife. 2021
Abstract
The central nervous system plans human reaching movements with stereotypically smooth kinematic trajectories and fairly consistent durations. Smoothness seems to be explained by accuracy as a primary movement objective, whereas duration seems to economize energy expenditure. But the current understanding of energy expenditure does not explain smoothness, so that two aspects of the same movement are governed by seemingly incompatible objectives. Here, we show that smoothness is actually economical, because humans expend more metabolic energy for jerkier motions. The proposed mechanism is an underappreciated cost proportional to the rate of muscle force production, for calcium transport to activate muscle. We experimentally tested that energy cost in humans (N = 10) performing bimanual reaches cyclically. The empirical cost was then demonstrated to predict smooth, discrete reaches, previously attributed to accuracy alone. A mechanistic, physiologically measurable, energy cost may therefore explain both smoothness and duration in terms of economy, and help resolve motor redundancy in reaching movements.
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You Snooze, You Win? An Ecological Dynamics Framework Approach to Understanding the Relationships Between Sleep and Sensorimotor Performance in Sport.
LaGoy, AD, Ferrarelli, F, Sinnott, AM, Eagle, SR, Johnson, CD, Connaboy, C
Sleep medicine clinics. 2020;(1):31-39
Abstract
Sleep has a widespread impact across different domains of performance, including sensorimotor function. From an ecological dynamics perspective, sensorimotor function involves the continuous and dynamic coupling between perception and action. Sport performance relies on sensorimotor function as successful movement behaviors require accurate and efficient coupling between perceptions and actions. Compromised sleep impairs different aspects of sensorimotor performance, including perceptual attunement and motor execution. Changes in sensorimotor performance can be related to specific features of sleep, notably sleep spindles and slow waves. One unaddressed area of study is the extent to which specific sleep features contribute to overall sport-specific performance.
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The mechanism of persistent undermining of a sacral pressure ulcer: Experimental analyses using a deformable model and examination of skin mobility over different anatomical locations.
Tanaka, M, Takahashi, Y, Hasegawa, K, Ito, Y, Nemoto, T, Isogai, Z
Journal of tissue viability. 2020;(2):130-134
Abstract
Undermining is an important issue in the treatment and care of deep pressure ulcers. The frequency of the undermining over different bony prominences varies. In particular, deep pressure ulcers over the sacrum exhibit undermining more frequently than those occurring over the heel. Although shear force has been suggested as a critical factor in undermining, the exact mechanism remains unclear due to ethical and technical reasons in clinical practice. To clarify this issue, a deformable model was constructed to recreate the physical and morphological properties of a pressure ulcer with persistent undermining. The model was constructed using urethane to recreate the physical properties of a pressure ulcer. To examine the clinical relevance of the model, mechanical properties of the skin and the model were measured using a durometer. The model was further mounted onto a phantom that was laid on a bed. Backrest elevation of the bed induced deformities in the urethane model, suggesting a mechanism of persistent undermining of the sacral pressure ulcer. Moreover, a simple palpation examination in elderly volunteers revealed that the skin over the sacrum was more mobile than the skin over the heel. Therefore, persistent undermining is likely caused by specific external forces and the characteristic skin mobility of the sacral region. These two different factors explain the frequent undermining that occurs in sacral pressure ulcers.
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Physiological responses to different neuromuscular movement task during eccentric bench press.
Wilk, M, Stastny, P, Golas, A, Nawrocka, M, Jelen, K, Zajac, A, Tufano, JJ
Neuro endocrinology letters. 2018;(1):26-32
Abstract
OBJECTIVES Increasing muscular hypertrophy is one of the main reasons for participating in a resistance training program, where different movement task such as eccentric cadences may serve as a potent hypertrophic stimulus and improve movement stability. Aim of this study was to investigate the physiological responses between slow 6/0/2/0 (SLOW) and moderate 2/0/2/0 (REG) eccentric cadences during five sets of bench press to failure using 70% 1 repetition maximum (1RM). MATERIALS AND METHODS Blood samples from sixteen men (21-29y, 85.9±7.7kg, 130±17.5kg bench press 1RM) with at least five years of resistance training experience were taken before, immediately after, 30 min after, and 60 min after both protocols in a randomized cross over study design. RESULTS ANOVA showed that more repetitions were performed during each set in REG and for the entire REG protocol (p<0.001), but total time under tension was greater during SLOW in each set and for the entire protocol (p<0.001). The post-exercise levels of lactate (p=0.02), creatine kinase (p=0.04), and testosterone (p=0.01) were greater after SLOW. Post-exercise cortisol levels decreased in both protocols (p<0.001), but these decreases were not significantly different between protocols. CONCLUSIONS Therefore, intentionally slow eccentric speeds and increased eccentric time under tension seem to be effective for increasing acute hormonal responses after exercise. As such, although a SLOW tempo may decrease the amount of total work (i.e. fewer repetitions with the same load), the increased time under tension seems to drive hormonal responses and neurological response, which may play a large role in stimulating muscle growth, coordination and movement stability.
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Task errors contribute to implicit aftereffects in sensorimotor adaptation.
Leow, LA, Marinovic, W, de Rugy, A, Carroll, TJ
The European journal of neuroscience. 2018;(11):3397-3409
Abstract
Perturbations of sensory feedback evoke sensory prediction errors (discrepancies between predicted and actual sensory outcomes of movements), and reward prediction errors (discrepancies between predicted rewards and actual rewards). When our task is to hit a target, we expect to succeed in hitting the target, and so we experience a reward prediction error if the perturbation causes us to miss it. These discrepancies between intended task outcomes and actual task outcomes, termed "task errors," are thought to drive the use of strategic processes to restore success, although their role is incompletely understood. Here, as participants adapted to a 30° rotation of cursor feedback representing hand position, we investigated the role of task errors in sensorimotor adaptation: during target-reaching, we either removed task errors by moving the target mid-movement to align with cursor feedback of hand position, or enforced task error by moving the target away from the cursor feedback of hand position, by 20-30° randomly (clockwise in half the trials, counterclockwise in half the trials). Removing task errors not only reduced the extent of adaptation during exposure to the perturbation, but also reduced the amount of post-adaptation aftereffects that persisted despite explicit knowledge of the perturbation removal. Hence, task errors contribute to implicit adaptation resulting from sensory prediction errors. This suggests that the system which predicts the sensory consequences of actions via exposure to sensory prediction errors is also sensitive to reward prediction errors.
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Triggering Mechanisms for Motor Actions: The Effects of Expectation on Reaction Times to Intense Acoustic Stimuli.
Leow, LA, Uchida, A, Egberts, JL, Riek, S, Lipp, OV, Tresilian, J, Marinovic, W
Neuroscience. 2018;:226-235
Abstract
Motor actions can be released much sooner than normal when the go-signal is of very high intensity (>100 dBa). Although statistical evidence from individual studies has been mixed, it has been assumed that sternocleidomastoid (SCM) muscle activity could be used to distinguish between two neural circuits involved in movement triggering. We summarized meta-analytically the available evidence for this hypothesis, comparing the difference in premotor reaction time (RT) of actions where SCM activity was elicited (SCM+ trials) by loud acoustic stimuli against trials in which it was absent (SCM- trials). We found ten studies, all reporting comparisons between SCM+ and SCM- trials. Our mini meta-analysis showed that premotor RTs are faster in SCM+ than in SCM- trials, but the effect can be confounded by the variability of the foreperiods employed. We present experimental data showing that foreperiod predictability can induce differences in RT that would be of similar size to those attributed to the activation of different neurophysiological pathways to trigger prepared actions. We discuss plausible physiological mechanisms that would explain differences in premotor RTs between SCM+ and SCM- trials.
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Brain Motor Control Assessment Post Early Intensive Hand Rehabilitation After Spinal Cord Injury.
Zoghi, M, Galea, M
Topics in spinal cord injury rehabilitation. 2018;(2):157-166
Abstract
Background: The Brain Motor Control Assessment (BMCA) is a surface electromyography (sEMG)-based measure of motor output from the central nervous system during a variety of reflex and voluntary motor tasks. Objective: The aim of this study was to assess the pattern of voluntary movements in patients with spinal cord injury (SCI) to investigate whether BMCA could add more resolution to clinical assessments and the recovery path of these patients. Method: Ten participants were recruited from the Royal Talbot Rehabilitation Centre as part of a multicenter randomized controlled trial. Four participants received usual care while the other 3 participants received usual care plus an intensive task-specific hand training program in conjunction with functional electrical stimulation for 8 weeks. BMCA assessments were completed for 7 participants at this center 4 times over a period of 1 year. Results: Generalized linear model analysis showed a significant main effect of task (p < .001) and assessment time (p = .003) on the Similarity Index. However, there were no significant interactions among the factors (p > .05). Based on ARAT or summed upper limb strength scores, some participants showed significant improvement after 8 weeks of rehabilitation, however this improvement was not reflected in the pattern of muscle activation that was captured by BMCA. Conclusion: The quantifiable features of BMCA through surface EMG may increase the resolution of SCI characterization by adding subclinical details to the clinical picture of lesion severity and progression during rehabilitation.