O objetivo deste estudo foi investigar os efeitos de diferentes estruturas de prática sobre a organização hierárquica de habilidades motoras no processo adaptativo. Dois experimentos foram conduzidos, cada um com a participação de 40 adultos jovens de ambos os sexos. O delineamento de ambos os experimentos contou com duas fases (estabilização e adaptação) e quatro grupos de prática: constante, constante-aleatória, aleatória e aleatória-constante. No experimento 1, os participantes executaram 240 tentativas de rebatida forehand do tênis de campo na fase de estabilização e 60 tentativas na fase de adaptação. As medidas de macro e microestrutura referiram-se, respectivamente, aos timings relativos e o tempo total de movimento. E, o desempenho foi analisado por meio de um índice de desempenho (ID) e coeficiente de variação. No experimento 2, os participantes realizaram 90 tacadas putting do golfe na fase de estabilização e 30 na fase de adaptação. As medidas utilizadas foram os deslocamentos e os timings relativos (macroestrutura) e deslocamento e tempo totais de movimento (microestrutura). Análises de clusters foram conduzidas para inferir a emergência de padrões de movimento ao longo da prática. O desempenho foi analisado por meio de ANOVAs. Os resultados do experimento 1 mostraram que a macro e microestruturas tornaram-se mais consistentes na fase de estabilização, mas isso não foi acompanhado de melhora no desempenho. Verificou-se que em todo experimento a variabilidade da macroestrutura foi superior àquela da microestrutura. No experimento 2, os grupos de prática constante, aleatória e aleatória-constante alteraram macro e microestruturas e melhoraram o desempenho na fase de estabilização. Porém, com a modificação da tarefa, não suportaram a perturbação e pioraram o desempenho. Associado aos resultados de desempenho esteve o fato de a consistência da macroestrutura ter sido menor que a da microestrutura, inferindo-se assim, não ter ocorrido estabilização funcional / The aim of this study was to investigate the effects of different practice schedules on the hierarchical organization of motor skills in the adaptive process. Two experiments were conducted, each with the participation of 40 young adults of both sexes. The design of both experiments consisted of two phases (stabilization and adaptation) and four practice groups: constant, constant-random, random and random-constant. In experiment 1, participants performed 240 trials of field tennis forehand in the stabilization phase, and 60 trials in the adaptation phase. The macro- and microstructure measures referred to relative timing and total movement time, respectively. In addition, the performance was analyzed through a performance index (ID) and coefficient of variation. In Experiment 2, participants performed 90 trials of golf putting strokes in the stabilization phase, and 30 trials in the adaptation phase. The measures were relative displacement and timing (macrostructure) and total displacement and time (microstructure). Cluster analyzes were run for inferring the emergence of movement patterns over practice. The performances were analyzed through ANOVAs. The results of experiment 1 showed that showed that the macro and microstructures became more consistent in the stabilization phase, but this was not accompanied by an improvement in performance. It was verified that in all experiment the variability of the macrostructure was superior to that of the microstructure. In experiment 2, constant, random and random-constant groups altered macro and microstructure and improved performance in the stabilization phase. However, with task modification they did not support the perturbation and worsened the performance. Associated with the performance results was the fact that the consistency of the macrostructure was lower than that of the microstructure, thus inferring that functional stabilization had not occurred

Low back problems are among the most common nonfatal occupational injuries reported in the United States, and account for substantial healthcare expenditures (e.g., medical care costs) and losses to worker productivity. A strong association has been well-documented between occupational exposure to repetitive trunk motion and low back problems, particularly among workers performing manual material handling (i.e., lifting) activities. A feature of repetitive motion believed important to the development of work-related musculoskeletal disorders (MSDs), including low back problems, is a lack of within-individual, between-cycle variation of physical exposure summary measures, e.g., when observed visually, the cycle-to-cycle motion pattern appears consistent. An active literature has emerged using concepts of motor control to improve ergonomists’ understanding of physical exposure variation (i.e., motor variability) arising from individual-level mechanisms during repetitive work. Fundamentally, for any particular individual, the onset of exposure to a repetitive physical activity (i.e., task training) involves a learning process during which motor control strategies are developed to accomplish the task effectively. The cycle-to-cycle variability of motor learning metrics, such as postural and task performance summary measures, has been observed to exponentially decay during task training. From an ergonomics perspective, a temporal reduction in postural variability may lead to greater cumulative loading and physiological fatiguing of the underlying muscle tissues (due to more consistent cycle-to-cycle movements), thus increasing MSD risk over time. However, it is not known if, or to what extent, physical task characteristics (e.g., work pace) modify the temporal behavior of motor variability during training of a repetitive occupational activity. Moreover, the relationships between motor variability, task performance, and muscle fatigue during occupational task training are not well understood. The goal of this dissertation was to present new information concerning occupationally relevant metrics of motor learning during training of a laboratory-simulated, repetitive lifting activity. In this study, participants performed 100 repetitions (i.e., cycles) of the lifting task in each of four experimental sessions (i.e., visits) at different combinations of box load (low or high) and work pace (slow or fast). Three main observations were discussed in this dissertation: (i) participants exhibited a greater temporal reduction in the cycle-to-cycle variability of trunk postural summary measures during training of a heavier-weighted and faster-paced lifting activity (Chapter 3), which may have facilitated increases in the efficiency and repeatability of box movements (Chapter 4), (ii) the cycle-to-cycle variability of the erector spinae (back) muscle activity summary measures increased, but the variability of the multifidus muscle activity summary measures decreased, over time during faster-paced lifting (Chapter 3), and (iii) a greater temporal increase in trunk postural variability (i.e., a more “flexible” trunk movement strategy) was generally associated with lesser electromyographic back muscle fatigue during training of the lifting task (Chapter 5). Collectively, these research findings may open pathways to the development of new task design criteria and ergonomic guidelines to promote motor variability in the workplace and, ultimately, improve workers’ musculoskeletal health.

Researchers have shown that learners who self-control (SC) their knowledge of results (KR) schedule learn the task more effectively than yoked learners. A common recommendation from these results is that learners should be provided choice over their KR schedule, rather than at a coaches' discretion (Wulf & Lewthwaite, 2016). No research to date has compared SC learners to a group that more closely mimics receiving KR from a coach, thus challenging whether such a recommendation can be made. To this end, three groups learned a golf putting task; an SC group, a traditional yoked group (TY), and a group who were led to believe that their KR schedule was being controlled by a golf coach (perceived coach-controlled yoked group; PCC). Participants (N = 60) completed three phases; pre-test, acquisition, and two 24-hr delayed post-tests (retention/transfer). All groups lowered their mean radial error (MRE) and bivariate variable error (BVE) throughout acquisition. As hypothesized, the SC group (M = 40.10) had lower adjusted MRE compared to the TY group (M = 43.12) during the post-tests, yet, the PCC group had the lowest adjusted MRE (M = 36.61). These differences, however, were not statistically significant, F(2, 54) = 2.81, p = .069. BVE did not display the same pattern as MRE during the post-test as group means were clustered together, F(2, 57) = 0.38, p = .963. Results from a questionnaire indicated that both yoked groups showed moderate ratings for receiving KR on a desired schedule, as well as preferring KR on good trials, or good and bad trials equally. Taken together, these results call into question the recommendation for practitioners to give choice to a learner over KR scheduling.

Motor learning is an important component of daily life: humans are constantly adjusting their movements and acquiring new skills in order to meet the demands of their environment. Motor learning also contributes to neurorehabilitation, so it is therefore important to understand the neural mechanisms underlying motor learning so that these mechanisms can be exploited to promote neurorehabilitation after central nervous system injury. This dissertation focuses on three distinct methods of improving motor learning in healthy adults. In Chapter 2, we tested the effects of perturbation schedule on retention of a locomotor adaptation. The results of this work demonstrated that introducing a perturbation slowly and incrementally versus introducing a perturbation abruptly produces similar behavioral expression of locomotor memories across days. In Chapter 3, we tested whether administering 200 mg of caffeine immediately after practicing a novel motor skill enhances retention of that skill 24 hours later. However, we found that post-practice caffeine administration did not significantly improve retention of the motor skill. In combination with previous reports, these results suggest that the effects of post-practice caffeine administration are likely task-specific. In Chapter 4, we examined the interactions between hand use, practice-dependent plasticity and motor learning. We found that experimentally immobilizing the left hand for 8 hours facilitates subsequent practice-dependent changes in corticospinal excitability in a topographically-specific manner. In contrast, immobilization did not facilitate practice-dependent changes in TMS-evoked thumb movements, nor did it promote learning or retention of a ballistic motor skill. Although it is thought that practice-dependent changes in corticospinal excitability are an important and potentially causal contributor to motor memory, the results of this work indicate that experimentally enhancing practice-dependent changes in corticospinal excitability is not sufficient to promote motor learning. In sum, although none of the experimental interventions tested here substantially improved motor learning, these experiments highlight the influence of various mechanisms on motor learning in the intact nervous system.

[Tuncated abstract] Previous research has shown that associated movements (AMs) decrease with age in typically developing children. However, considerable variability has been found to exist between children of the same chronological age (Wolff et al., 1983; Largo et al., 2001) and the reasons for this variability are unclear. As AMs are considered to be a construct of motor behaviour it is possible that varying levels of motor ability may contribute to this variability. Only a few studies have investigated the relationship between motor ability and AM expression, and those have resulted in equivocal findings. Therefore, the aim of the first study in this research project was to investigate the relationship between motor ability and AMs using a large sample of normative children (N=165). Group 1 consisted of 19 boys and 33 girls in school year 1 with a mean age of 6 years and 4 months (SD = 4 months); Group 2 consisted of 28 boys and 29 girls in school year 3 with a mean age of 8 years and 3 months (SD = 3 months); and Group 3 consisted of 27 boys and 29 girls in school year 5 with a mean age of 9 years 11 months (SD = 5 months). Motor ability was established using the McCarron Assessment of Neuromuscular Development (MAND) (McCarron, 1982). Associated movements were measured using tasks adapted from the Zurich Neuromotor Assessment (Largo et al., 2002), the Fog Test (Fog & Fog, 1963), and Licari et al. (2006). '...' The second study in this research project continued to explore the relationship between motor ability and AMs by investigating whether increased severity of AMs previously reported in children with attention deficit hyperactivity disorder (ADHD) (Denckla & Rudel, 1978; Lazarus, 1994; Mostofsky et al., 2003) is reflective of symptoms associated with the disorder or movement difficulties co-occurring in some children with the disorder. Four groups of children participated in the study. Group 1 consisted of 13 children with Developmental Coordination Disorder (DCD) with a mean age of 7 years 3 months (SD = 9 months); Group 2 consisted of 13 children with ADHD with a mean age of 7 years 4 months (SD = 11 months); Group 3 consisted of 10 children with co-occurring DCD and ADHD with a mean age of 7 years 4 months (SD = 10 months); and, Group 4 was a normative sample 15 control children. The children undertook the same AM assessment protocol outlined for Study 1. The AM data was entered into the RUMM 2020 and person location estimates (Rasch AM scores) were created for each child based on the person location map from Study 1. A comparison of AM scores between the groups revealed that the DCD and DCD/ADHD groups showed significantly more (p <0.001) AMs than the children in the ADHD and control groups. No significant differences were found between children in the DCD and DCD/ADHD groups (p = 0.19) or the ADHD and control groups (p = 0.67). The findings of this research show that increased expression of AMs is not influenced by the symptoms of ADHD. In addition, the finding that increased expression of AMs in children with DCD extends the findings from Study 1 showing that AM expression is linked to motor ability. Overall this research has enhanced the understanding of a unique measure of motor behaviour.

While the traditional dependent variables of motor skill learning are accuracy and consistency of movement outcome, there has been increasing interest in aspects of motor performance that are described as reflecting the ‘energetics’ of motor behaviour. One defining characteristic of skilled motor performance is the ability to complete the task with minimum energy expenditure (Sparrow & Newell, 1998). A further consideration is that movements also have costs in terms of cognitive ‘effort’ or ‘energy’. The present project extends previous work on energy expenditure and motor skill learning within a coordination dynamics framework. From the dynamic pattern perspective, a coordination pattern lowest on the 11KB model potential curve (Haken, Kelso & Bunz, 1985) is more stable and least energy is required to maintain pattern stability (Temprado, Zanone, Monno & Laurent, 1999). Two experiments investigated the learning of stable and unstable coordination patterns with high metabolic energy demand. An experimental task was devised by positioning two cycle ergometers side-by-side, placing one foot on each, with the pedals free to move independently at any metronome-paced relative phase, Experiment 1 investigated practice-related changes to oxygen consumption, heart rate, relative phase, reaction time and muscle activation (EMG) as participants practiced anti-phase, in-phase and 90°-phase cycling. Across six practice trials metabolic energy cost reduced and AE and VE of relative phase declined. The trend in the metabolic and reaction time data and percent co-contraction of muscles was for the in-phase cycling to demonstrate the highest values, anti-phase the lowest and 90°-phase cycling in-between. It was found that anti- and in-phase cycling were both kinematically stable but anti-phase coordination revealed significantly lower metabolic energy cost. It was, therefore, postulated that of two equally stable coordination patterns, that associated with lower metabolic energy expenditure would constitute a stronger attractor. Experiment 2 was designed to determine whether a lower or higher energy-demanding coordination pattern was a stronger attractor by scanning the attractor layout at thirty-degree intervals from 0° to 330°. The initial attractor layout revealed that in-phase was most stable and accurate, but the remaining coordination patterns were attracted to the low energy cost anti-phase cycling. In Experiment 2 only 90°- phase cycling was practiced with a post-test attractor layout scan revealing that 90°-phase and its symmetrical partner 270°-phase had become attractors of other coordination patterns. Consistent with Experiment 1, practicing 90°-phase cycling revealed a decline in AE and VE and a reduction in metabolic and cognitive cost. Practicing 90°-phase cycling did not, however, destabilise the in-phase or anti-phase coordination patterns either kinematically or energetically. In summary, the findings suggest that metabolic and mental energy can be considered different representations of a ‘global’ energy expenditure or ‘energetic’ phenomenon underlying human coordination. The hypothesis that preferred coordination patterns emerge as stable, low-energy solutions to the problem of inter-and intra-limb coordination is supported here in showing that the low-energy minimum of coordination dynamics is also an energetic minimum.

Motion is a fundamental activity for the healthy functioning human organism. Its importance, however, is increasingly de-valued in Western cultures as they speed toward adopting technologies and virtual experiences as adjuncts to, and even replacements for7 traditional educational structures and processes that involve physical activity. Organised and reflective experience of human motion is becoming increasingly marginalised in teaching methodologies and learning programs in educational institutions at all levels around the globe. This inquiry sets out to gain a greater understanding of why people and human motion become disconnected, particularly during periods of formal education. A central question and two sub-questions form the basis of the inquiry. The central question asks why human motion is not valued and more utilised in education. In particular, why do learning areas that directly represent involvement with human motion, such as physical education, continually struggle in education programs. It directs the investigation to focus on the causes rather than the symptoms of the disuse and devaluation of human motion in Australian education. The two sub-questions split the praxis of the study. The first seeks to understand how the causes of devaluation work in the educational context lo affect the lack of acknowledgement; and the second considers ways to counter the disuse of human movement in education programs. To address these questions, the research focuses on rebutting the notion of a mind-body dualism. Rather, it seeks to better understand how humans learn and function as monists - integrated beings, acquiring self-knowledge in their 'world of being' in which bodily and emotional experiences, and reasoning are inextricably intertwined. I have approached this qualitative research as an ethnographic sociologist examining the issues from a critical high modernist perspective in order to demonstrate the pervading influence in Australian education of strong beliefs and values from the era of Enlightenment. Narrative analysis of 'memoir' in the form of self-defining memories was selected to gain a sensibility of the connectedness between human emotion, motion and reasoning in the lived experiences of students in three primary and three secondary schools across Years 2-12. An opportunity for human movement to be more valued and utilised in emerging educational frameworks that have life knowledge, dispositions and capabilities at their core is identified. The inquiry proposes a conceptualisation of human motion in education for new times characterised by the need for people to develop personal resources and strong positive identities in order to cope with a world of rapid change and uncertainty.

Previous research on contextual interference theory in controlled laboratory situations consistently illustrated that random practice was superior to blocked practice when learning motor skills. However, when considered in relation to physical education class settings the findings of the contextual interference experiments were not as uniform. Furthermore, the results of the contextual interference research were ambiguous when an open skill was used as the experimental task, with no definite trend evident. Random practice was found more effective for learning (del Rey, 1989) whereas French, Rink and Werner (1990) demonstrated blocked practice to be superior. In the present study, the influence of high and low contextual interference as practice schedules was investigated within an applied sports setting using an open sports skill as the experimental task. Two groups of boys and girls, 8-9 and 10-12 years of age, were taught a forehand tennis groundstroke using both their preferred and non-preferred hands over a ten week coaching and practice period. The findings showed that male subjects were significantly better at the experimental task than female subjects at the pre-test stage only. The result also demonstrated that the 10-12 year old subjects were significantly better than the 8-9 year olds at the task with the exception of the preferred hand at the post and retention test stage. The contextual interference effect was demonstrated in the retention phase on the preferred hand of the 10-12 year old subjects where the random practice group was significantly better than the blocked practice group in an applied sports setting. These findings were discussed in relation to the role of cognition in the learning of these motor skills and the influence of the subjects related background experiences.

The goal of this thesis is to apply the computational approach to motor learning, i.e., describe the constraints that enable performance improvement with experience and also the constraints that must be satisfied by a motor learning system, describe what is being computed in order to achieve learning, and why it is being computed. The particular tasks used to assess motor learning are loaded and unloaded free arm movement, and the thesis includes work on rigid body load estimation, arm model estimation, optimal filtering for model parameter estimation, and trajectory learning from practice. Learning algorithms have been developed and implemented in the context of robot arm control. The thesis demonstrates some of the roles of knowledge in learning. Powerful generalizations can be made on the basis of knowledge of system structure, as is demonstrated in the load and arm model estimation algorithms. Improving the performance of parameter estimation algorithms used in learning involves knowledge of the measurement noise characteristics, as is shown in the derivation of optimal filters. Using trajectory errors to correct commands requires knowledge of how command errors are transformed into performance errors, i.e., an accurate model of the dynamics of the controlled system, as is demonstrated in the trajectory learning work. The performance demonstrated by the algorithms developed in this thesis should be compared with algorithms that use less knowledge, such as table based schemes to learn arm dynamics, previous single trajectory learning algorithms, and much of traditional adaptive control.

The purpose of the current study was to examine the effects of self-controlled video feedback on the learning of the basketball set shot. Female participants were assigned to self-control (SC) (n = 14) and yoked (YK) (n = 14) groups. SC participants were allowed to request video feedback in the form of knowledge of performance (KP) following any trial while YK participants received video KP according to the schedule created by their SC counterpart. Participants in both groups were also allowed to view a poster of written instructional cues at any time. An acquisition phase consisted of 25 set shots (five blocks) from a youth free throw line (3.66 m). Each trial was 30 s in duration. An additional 30 s break was given between blocks. Retention and transfer phases each consisted of ten trials (two blocks) and occurred 24 hours following acquisition. Retention was administered from the youth free throw line and transfer from a traditional free throw line (4.57 m). Participants were scored on both movement form and shooting accuracy during acquisition, retention, and transfer. Results indicated that the SC group had significantly higher form scores than the YK group during Blocks 3 and 5 of acquisition and during the transfer phase. In addition, the SC group looked at the instructional cues more frequently than the YK group. Both groups increased shooting accuracy during acquisition (p < .05), but did not differ from one another during any of the experimental phases. A number of results differed from previous research findings. The responses of participants on a post-training questionnaire indicated no preference for requesting or receiving feedback following so-called good trials as reported by Chiviacowsky & Wulf (2002, 2005). In addition, there were no differences in accuracy or form between feedback (i.e., good) and no feedback (i.e., poor) trials. Overall, the results indicated that self-controlled video KP facilitated learning of correct shooting technique.