Relationship Between Actual and Perceived Locomotor and Ball Skills Competence Among Children: A Person-Centered Approach.

This study examined whether profiles varying in actual and perceived locomotor and ball skill competencies would be identified and whether these profiles would differ in relation to children's characteristics. Participants were 127 (70 boys; 57 girls) French-speaking Canadian children (5-11 years). Actual and perceived motor competencies were, respectively, measured using the Test of Gross Motor Development - Third version and the pictorial scale of Perceived Movement Skill Competence. Latent profile analyses revealed four profiles: (1) Non-Alignment: Devaluation (children underestimated their slightly below average competencies; 17.9%); (2) Non-Alignment: Overestimation (children overestimated their slightly below average competencies; 24.7%); (3) Non-Alignment: Underestimation (children slightly underestimated their above average competencies; 24.9%); (4) Alignment: Low Competence (children displayed accurate but slightly below average competencies; 32.5%). Girls were more likely to correspond to profiles 1 and 4, older children and children more frequently involved in physical activity/sport practice were more likely to correspond to profile 3, and younger children were more likely to correspond to profile 2. These results emphasise the importance of considering the alignment between perceived and actual motor competencies. They also indicate that age and physical activity/sport practice were associated with higher competencies, whereas girls and younger children were associated with lower competencies.

Learning Spinal Manipulation: Objective and Subjective Assessment of Performance.

OBJECTIVE: The purpose of this study was to investigate associations between objective spinal manipulation therapy (SMT) biomechanical parameters and subjective assessments provided by patients, clinicians, and expert assessors. METHODS: Chiropractic students (N = 137) and expert instructors (N = 14) were recruited. Students were asked to perform a thoracic SMT alternately on each other on a force-sensing table while being observed by an expert instructor. Students who performed (clinicians) and received (patients) SMT, and expert instructors, independently scored each SMT performance using visual analog scales. Correlations between these subjective scores and SMT biomechanical parameters were calculated. The following parameters were evaluated: peak force, preload force, thrust duration, and drop in preload force. Spinal manipulation therapy comfort was also assessed by patients, clinicians, and expert instructors. RESULTS: Results of the study indicate that thrust duration assessed by instructors and patients was the only parameters significantly correlated with the table data (r = .37; P < .001 and r = .26; P = .002). Comfort assessed by clinicians was significantly correlated with their own assessments of thrust duration (r = .37; P < .001) and preload force (r = .23; P = .007), whereas comfort assessed by instructors was significantly correlated with their own assessment of thrust duration (r = .27; P = .002) and drop in preload force (r = -.34; P < .001). Objective biomechanical parameters of performance did not predict perceived comfort. CONCLUSIONS: Overall, the results from the subjective assessments of SMT performance are weakly correlated with objective measures of SMT performance. Only the thrust duration evaluated by expert instructors and patients was associated with scores obtained from the table. Perceived comfort of the procedure seems to be associated mostly with perceived thrust duration and preload characteristics.

Motor adaptations to trunk perturbation: effects of experimental back pain and spinal tissue creep.

In complex anatomical systems, such as the trunk, motor control theories suggest that many motor solutions can be implemented to achieve a similar goal. Although reflex mechanisms act as a stabilizer of the spine, how the central nervous system uses trunk redundancy to adapt neuromuscular responses under the influence of external perturbations, such as experimental pain or spinal tissue creep, is still unclear. The aim of this study was to identify and characterize trunk neuromuscular adaptations in response to unexpected trunk perturbations under the influence of spinal tissue creep and experimental back pain. Healthy participants experienced a repetition of sudden external trunk perturbations in two protocols: 1) 15 perturbations before and after a spinal tissue creep protocol and 2) 15 perturbations with and without experimental back pain. Trunk neuromuscular adaptations were measured by using high-density electromyography to record erector spinae muscle activity recruitment patterns and a motion analysis system. Muscle activity reflex attenuation was found across unexpected trunk perturbation trials under the influence of creep and pain. A similar area of muscle activity distribution was observed with or without back pain as well as before and after creep. No change of trunk kinematics was observed. We conclude that although under normal circumstances muscle activity adaptation occurs throughout the same perturbations, a reset of the adaptation process is present when experiencing a new perturbation such as experimental pain or creep. However, participants are still able to attenuate reflex responses under these conditions by using variable recruitment patterns of back muscles. NEW & NOTEWORTHY The present study characterizes, for the first time, trunk motor adaptations with high-density surface electromyography when the spinal system is challenged by a series of unexpected perturbations. We propose that the central nervous system is able to adapt neuromuscular responses by using a variable recruitment pattern of back muscles to maximize the motor performance, even under the influence of pain or when the passive structures of the spine are altered.

The Effect of Augmented Feedback and Expertise on Spinal Manipulation Skills: An Experimental Study.

OBJECTIVES: The purpose of this study was to investigate the combined effect of augmented feedback and expertise on the performance and retention of basic motor learning spinal manipulation skills. METHODS: A total of 103 chiropractic students with various training expertise were recruited for the study. Participants were evaluated at baseline, immediately after trials of augmented feedback practice and 1 week later. During all 3 assessments, students were asked to perform several trials of the same spinal manipulation, for which the maximum preload force, onset of thrust, thrust duration, force and peak force, thrust duration, rate of force application, and any drop in preload force were calculated. The constant error, absolute error, and variable error were calculated for the 3 experimental blocks of trials. RESULTS: Results confirmed that augmented feedback training modified several biomechanical parameters such as the rate of force application, the preload force, and the drop in preload force. The study also confirmed that many biomechanical parameters, including thrust duration and rate of force application, are modified with expertise but failed to identify any interaction effect between expertise and augmented feedback training effects. CONCLUSION: The study determined that expertise did not influence how students performed after a session of augmented feedback training. The study also determined that augmented feedback related to the global performance can yield improvements in several basic components of the spinal manipulation task. These results should be interpreted considering basic motor learning principles and specific learning environments.

Effect of Hippotherapy on Motor Proficiency and Function in Children with Cerebral Palsy Who Walk.

AIMS: To evaluate the effects of hippotherapy on physical capacities of children with cerebral palsy. METHODS: Thirteen children (4-12 years old) with cerebral palsy classified in Gross Motor Function Classification System Level I or II were included in this prospective quasi-experimental ABA design study. Participants received 10 weeks of hippotherapy (30 min per week). Gross motor function and proficiency were measured with the Bruininks-Oseretski Motor Proficiency short form [BOT2-SF]) and the Gross Motor Function Measure-88 [GMFM-88] (Dimension D and E) twice before the program (T1 and T1'), immediately after (T2), and 10 weeks following the end of the program (T3). RESULTS: Mean scores for dimensions D and E of the GMFM-88 Dimension scores (p = .005) and three out of the eight items of the BOT2-SF (fine motor precision (p = .013), balance (p = .025), and strength (p = .012) improved between baseline and immediately after intervention; mean scores immediately following and 10 weeks following intervention did not differ. CONCLUSIONS: Hippotherapy provided by a trained therapist who applies an intense and graded session for 10 weeks can improve body functions and performance of gross motor and fine motor activities in children with cerebral palsy.

Neuromechanical response to spinal manipulation therapy: effects of a constant rate of force application.

BACKGROUND: Neuromechanical responses to spinal manipulation therapy (SMT) have been shown to be modulated through the variation of SMT biomechanical parameters: peak force, time to peak force, and preload force. Although rate of force application was modulated by the variation of these parameters, the assumption that neuromuscular responses are modulated by the rate of force application remains to be confirmed. Therefore, the purpose of the present study was to evaluate the effect of a constant rate of force application in neuromechanical responses to SMT in healthy adults. METHODS: Four SMT force-time profiles presenting different time to peak force and peak force, but with a constant rate of force application were applied on 25 healthy participants' T7 transverse processes. Muscular responses were recorded through surface electromyography electrodes (T6 and T8 levels), while vertebral displacements were assessed through pasted kinematic markers on T6 to T8 spinous processes. Effects of SMT force-time profiles on neuromechanical responses were assessed using repeated-measures ANOVAs. RESULTS: There was no main effect of SMT force-time profile modulation on muscular responses (ps > .05) except for the left T8 (F (3, 72) = 3.23, p = .03) and left T6 (F (3, 72) = 2.94, p = .04). Muscular responses were significantly lower for the lowest peak force condition than the highest (for T8) or second highest (for T6). Analysis showed that increasing the SMT peak force (and concomitantly time to peak force) led to a significant vertebral displacement increase for the contacted vertebra (F T7 (1, 17) = 354.80, p < .001) and both adjacent vertebras (F T6 (1, 12) = 104.71, p < .001 and F T8 (1, 19) = 468.68, p < .001). CONCLUSION: This study showed that peak force modulation using constant rate of force application leads to similar neuromuscular responses. Coupled with previous investigations of SMT peak force and duration effects, the results suggest that neuromuscular responses to SMT are mostly influenced by the rate of force application, while peak force modulation yields changes in the vertebral displacement. Rate of force application should therefore be defined in future studies. Clinical implications of various SMT dosages in patients with spine related pain should also be investigated. TRIAL REGISTRATION: ClinicalTrials.gov NCT02550132 . Registered 8 September 2015.

Systematic Augmented Feedback and Dependency in Spinal Manipulation Learning: a Randomized Comparative Study.

OBJECTIVE: The purpose of the study was to evaluate if systematic augmented feedback during short sessions of spinal manipulation (SM) training creates a dependency compared with short training session characterized by progressive withdrawal of augmented feedback. METHODS: Forty fourth- and fifth-year chiropractic students enrolled in a 5-year chiropractic program were randomized into 2 groups. The 2 groups performed the same number of SM with a 300-N peak force target on an instrumented device. Baseline assessment consisted of 10 trials without feedback. Three training blocks of 10 SMs were then performed with visual and verbal feedback. For the control group, feedback was always provided. For the experimental group, augmented feedback was provided for each trial of the first training block, 50% of the second block, and 20% of the last training block. A postintervention assessment of 10 trials without feedback was performed, and a retention assessment was conducted 20 minutes later. RESULTS: No group main effect was found on biomechanical parameters and error variables. A main effect of learning for the absolute error was observed, suggesting that short sessions of feedback training improve participants' accuracy. CONCLUSION: The results of the study suggest that feedback scheduling does not influence SM motor performance and learning in clinically experienced students.

Learning spinal manipulation: the effect of expertise on transfer capability.

OBJECTIVE: Transfer capability represents the changes in performance in one task that result from practice or experience in other related tasks. Increased transfer capability has been associated with expertise in several motor tasks. The purpose of this study was to investigate if expertise in spinal manipulation therapy, assessed in groups of trainees and experienced chiropractors, is associated with increased transfer capabilities. METHODS: Forty-nine chiropractic students (fifth- and sixth-year students) and experienced chiropractors were asked to perform blocks of 10 thoracic spine manipulations in 3 different conditions: preferred position and table setting, increased table height, and unstable support surface. Spinal manipulations were performed on a computer-connected device developed to emulate a prone thoracic spine manipulation. Thrust duration, thrust force rate of force application, and preload force were obtained for each trial and compared across groups and conditions. RESULTS: Results indicated that both expertise and performance conditions modulated the biomechanical parameters of spinal manipulation. Decreased thrust duration and increased rate of force application were observed in experienced clinicians, whereas thrust force and thrust rate of force application were significantly decreased when task difficulty was increased. Increasing task difficulty also led to significant increases in performance variability. CONCLUSION: Overall, this study suggests that when instructed to perform spinal manipulation in a challenging context, trainees and experts choose to modulate force to optimize thrust duration, a characteristic feature of high-velocity, low-amplitude spinal manipulation. Given its known association with motor proficiency, transfer capability assessments should be considered in spinal manipulative therapy training.

The role of preload forces in spinal manipulation: experimental investigation of kinematic and electromyographic responses in healthy adults.

OBJECTIVES: Previous studies have identified preload forces and an important feature of skillful execution of spinal manipulative therapy (SMT) as performed by manual therapists (eg, doctors of chiropractic and osteopathy). It has been suggested that applying a gradual force before the thrust increases the spinal unit stiffness, minimizing displacement during the thrust. Therefore, the main objective of this study was to assess the vertebral unit biomechanical and neuromuscular responses to a graded increase of preload forces. METHODS: Twenty-three participants underwent 4 different SMT force-time profiles delivered by a servo-controlled linear actuator motor and varying in their preload forces, respectively, set to 5, 50, 95, and 140N in 1 experimental session. Kinematic markers were place on T6, T7, and T8 and electromyographic electrodes were applied over paraspinal muscles on both sides of the spine. RESULTS: Increasing preload forces led to an increase in neuromuscular responses of thoracic paraspinal muscles and vertebral segmental displacements during the preload phase of SMT. Increasing the preload force also yielded a significant decrease in sagittal vertebral displacement and paraspinal muscle activity during and immediately after the thrust phase of spinal manipulation. Changes observed during the SMT thrust phase could be explained by the proportional increase in preload force or the related changes in rate of force application. Although only healthy participants were tested in this study, preload forces may be an important parameter underlying SMT mechanism of action. Future studies should investigate the clinical implications of varying SMT dosages. CONCLUSION: The present results suggest that neuromuscular and biomechanical responses to SMT may be modulated by preload through changes in the rate of force application. Overall, the present results suggest that preload and rate of force application may be important parameters underlying SMT mechanism of action.

Standardization of spinal manipulation therapy in humans: development of a novel device designed to measure dose-response.

OBJECTIVE: The main objective of this report is to present an innovative research tool that will provide the opportunity to study fundamental aspects of the spinal manipulation dose-physiological response relation in humans. METHODS: A servo-controlled linear actuator motor was developed to simulate spinal manipulative therapy. Coefficient of multiple correlations was calculated to assess the degree of similarity between each measured force curves, whereas precision was obtained by comparing resulting peak force and time-to-peak force to the target curves. RESULTS: The coefficient of multiple correlations calculations showed that repeatability was very high with all correlation values over 0.98. Precision was also very high with average differences in peak force and time-to-peak force of less than 3 N and less than 5 milliseconds. CONCLUSION: The tool was designed to optimize precision, repeatability, and safety in the delivery of force to the spine in humans. It offers a unique opportunity to study dose-response relationship for several spinal manipulation parameters such as peak force, time-to-peak force, and preload.

Physiological responses to spinal manipulation therapy: investigation of the relationship between electromyographic responses and peak force.

OBJECTIVE: It is believed that systematic modulation of spinal manipulative therapy (SMT) parameters should yield varying levels of physiological responses and eventually a range of clinical responses. However, investigation of SMT dose-physiological response relationship is recent and has mostly been conducted using animal or cadaveric models. The main objective of the present study is to investigate SMT dose-physiological response relation in humans by determining how different levels of force can modify electromyographic (EMG) responses to spinal manipulation. METHODS: Twenty-six participants were subjected to 2 trials of 4 different SMT force-time profiles using a servo-controlled linear actuator motor. Normalized EMG activity of paraspinal muscles (left and right muscles at level T6 and T8) was recorded during and after SMT, and EMG values were compared across the varying levels of force. RESULTS: Increasing the level of force yielded an increase in paraspinal muscle EMG activity during the thrust phase of SMT but also in the two 250-millisecond time windows after the spinal manipulation impulse. These muscle activations quickly attenuated (500 milliseconds after spinal manipulation impulse). CONCLUSION: The study confirmed the presence of a local paraspinal EMG response after SMT and highlighted the linear relationship between the SMT peak force and paraspinal muscle activation.

A randomised controlled trial of preventive spinal manipulation with and without a home exercise program for patients with chronic neck pain.

BACKGROUND: Evidence indicates that supervised home exercises, combined or not with manual therapy, can be beneficial for patients with non-specific chronic neck pain (NCNP). The objective of the study is to investigate the efficacy of preventive spinal manipulative therapy (SMT) compared to a no treatment group in NCNP patients. Another objective is to assess the efficacy of SMT with and without a home exercise program. METHODS: Ninety-eight patients underwent a short symptomatic phase of treatment before being randomly allocated to either an attention-group (n = 29), a SMT group (n = 36) or a SMT + exercise group (n = 33). The preventive phase of treatment, which lasted for 10 months, consisted of meeting with a chiropractor every two months to evaluate and discuss symptoms (attention-control group), 1 monthly SMT session (SMT group) or 1 monthly SMT session combined with a home exercise program (SMT + exercise group). The primary and secondary outcome measures were represented by scores on a 10-cm visual analog scale (VAS), active cervical ranges of motion (cROM), the neck disability index (NDI) and the Bournemouth questionnaire (BQ). Exploratory outcome measures were scored on the Fear-avoidance Behaviour Questionnaire (FABQ) and the SF-12 Questionnaire. RESULTS: Our results show that, in the preventive phase of the trial, all 3 groups showed primary and secondary outcomes scores similar to those obtain following the non-randomised, symptomatic phase. No group difference was observed for the primary, secondary and exploratory variables. Significant improvements in FABQ scores were noted in all groups during the preventive phase of the trial. However, no significant change in health related quality of life (HRQL) was associated with the preventive phase. CONCLUSIONS: This study hypothesised that participants in the combined intervention group would have less pain and disability and better function than participants from the 2 other groups during the preventive phase of the trial. This hypothesis was not supported by the study results. Lack of a treatment specific effect is discussed in relation to the placebo and patient provider interactions in manual therapies. Further research is needed to delineate the specific and non-specific effects of treatment modalities to prevent unnecessary disability and to minimise morbidity related to NCNP. Additional investigation is also required to identify the best strategies for secondary and tertiary prevention of NCNP. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00566930.

Learning spinal manipulation skills: assessment of biomechanical parameters in a 5-year longitudinal study.

OBJECTIVE: Teaching spinal manipulation (SM) is a fundamental aspect of chiropractic training. Recent works have identified various biomechanical variables as indicators of SM performance and learning. However, only data from cross-sectional studies are available, limiting conclusions regarding the persistence of SM performance over the years. Therefore, the main objective of this investigation was to quantify the evolution of biomechanical parameters of SM over a 5-year learning period. METHODS: Thirty-three students enrolled in a chiropractic program participated in the present study. They were tested each year at the beginning of each fall semester by performing 10 SMs on an instrumented manikin while standing on a force plate. The procedure allowed us to measure various force-time parameters. RESULTS: Overall, significant time effects were noted for most dependent variables. The results indicated rapid improvement in the peak force applied and the rate of force production during the first 2 years. Time to peak force decreased drastically during the first year, whereas preload forces reached satisfactory levels during the third year. When various force-time requirements of bimanual task components were met, learners significantly reduced trial-to-trial variability of SM peak and preload forces, indicating automaticity of performance. Although global coordination improved in all learning processes, it was only in the later phase that learners reached values approaching those of experts. CONCLUSION: Overall, these results highlighted the importance of considering learning principles in the development of didactic strategies related to SM motor skills.

Effects of practice variability on spinal manipulation learning.

OBJECTIVE: To evaluate the effects of practice variability on chiropractic students' capacity to deliver spinal manipulations (SMs) of a targeted peak force. METHODS: Forty students participated in an experimental session including either a variable or a constant practice protocol of 45 SMs. SMs were delivered on a computer-connected device that recorded force-time profiles. Ten SMs with a target peak force of 350-N were performed before practice, immediately following practice, and 2 days later. Mixed-design analyses of variance were used to assess the effect of practice type on SM biomechanical parameters and on the constant, the absolute error (AE), and the variable error (VE). RESULTS: The practice period led to significantly more accurate (FAE[2,76] = 6.17, p < .01) and consistent (FVE[2,76] = 3.90, p = .02) performances at the postintervention assessment regardless of practice type. Among biomechanical parameters, preload force was higher at the retention assessment than at baseline (F[2,76] = 6.53, p < .01), while rate of force application significantly decreased between the baseline and the retention assessment (F[2,76] = 4.10, p = .02). CONCLUSION: This experimental study showed that 1 session of SM practice including feedback leads to an increase in SM peak force accuracy and consistency, whether or not the practice period included variable practice. The current results confirmed that short practice periods with feedback should be included in the chiropractic curriculum.

Learning spinal manipulation: the importance of augmented feedback relating to various kinetic parameters.

BACKGROUND CONTEXT: Spinal manipulation is a widely accepted therapeutic approach in the treatment of back pain. In standard training programs, feedback on student performances is provided by an instructor based on teaching and clinical experience. Systematic study of the type of augmented feedback provided and skill learning is lacking in the literature. PURPOSE: The goal of this investigation is to compare the performance of two groups of chiropractic students, one receiving traditional training from experienced instructors, and the other, augmented feedback on specific biomechanical aspects of spinal manipulation therapy using an instrumented manikin. STUDY DESIGN: Randomized controlled study. PATIENT SAMPLE: Thirty-one fourth-year students from the Department of Chiropractic of Université du Québec à Trois-Rivières participated in this study. OUTCOME MEASURES: Kinetic parameters (force-time curves) of spinal manipulation were evaluated. METHODS: Spinal manipulation parameters were measured before and after a 5-week training period in which one group received standard chiropractic training while a second group received augmented feedback about specific biomechanical parameters of spinal manipulation. For both groups, practice scheduling and time duration were similar and consisted of a weekly practice session of 90 minutes for five consecutive weeks. Both groups had to practice thoracic spine manipulation throughout the training period. RESULTS: Both groups showed a decrease in peak force applied, with a diminution in the number of trials where a downward incisural point was present in preload force. Participants in the feedback training group significantly reduced their peak force variability and significantly increased their preload force. No significant difference was observed for time to peak force. CONCLUSIONS: The results of this study highlight the merits of practicing with an instrumented manikin or other instrumented training aids. Such a device can provide specific feedback on specific parameters of the task during learning; it can also serve as a tool to assess the progress of students and eliminate the risks relating to repetitive spinal manipulative therapy practice on student colleagues.

Effects of Muscle Fatigue, Creep, and Musculoskeletal Pain on Neuromuscular Responses to Unexpected Perturbation of the Trunk: A Systematic Review.

Introduction: Trunk neuromuscular responses have been shown to adapt under the influence of muscle fatigue, as well as spinal tissue creep or even with the presence of low back pain (LBP). Despite a large number of studies exploring how these external perturbations affect the spinal stability, characteristics of such adaptations remains unclear. Aim: The purpose of this systematic review was to assess the quality of evidence of studies investigating trunk neuromuscular responses to unexpected trunk perturbation. More specifically, the targeted neuromuscular responses were trunk muscle activity reflex and trunk kinematics under the influence of muscle fatigue, spinal creep, and musculoskeletal pain. Methods: A research of the literature was conducted in Pubmed, Embase, and Sport-Discus databases using terms related to trunk neuromuscular reflex responses, measured by electromyography (baseline activity, reflex latency, and reflex amplitude) and/or trunk kinematic, in context of unexpected external perturbation. Moreover, independent variables must be either trunk muscle fatigue or spinal tissue creep or LBP. All included articles were scored for their electromyography methodology based on the "Surface Electromyography for the Non-Invasive Assessment of Muscles (SENIAM)" and the "International Society of Electrophysiology and Kinesiology (ISEK)" recommendations whereas overall quality of articles was scored using a specific quality checklist modified from the Quality Index. Meta-analysis was performed on reflex latency variable. Results: A final set of 29 articles underwent quality assessments. The mean quality score was 79%. No effect of muscle fatigue on erector spinae reflex latency following an unexpected perturbation, nor any other distinctive effects was found for back muscle fatigue and reflex parameters. As for spinal tissue creep effects, no alteration was found for any of the trunk reflex variables. Finally, the meta-analysis revealed an increased erector spinae reflex latency in patients with chronic LBP in comparison with healthy controls following an unexpected trunk perturbation. Conclusion: The literature provides some evidence with regard to trunk adaptions in a context of spinal instability. However, most of the evidence was inconclusive due to a high methodological heterogeneity between the studies.

Influence of Lumbar Muscle Fatigue on Trunk Adaptations during Sudden External Perturbations.

Introduction: When the spine is subjected to perturbations, neuromuscular responses such as reflex muscle contractions contribute to the overall balance control and spinal stabilization mechanisms. These responses are influenced by muscle fatigue, which has been shown to trigger changes in muscle recruitment patterns. Neuromuscular adaptations, e.g., attenuation of reflex activation and/or postural oscillations following repeated unexpected external perturbations, have also been described. However, the characterization of these adaptations still remains unclear. Using high-density electromyography (EMG) may help understand how the nervous system chooses to deal with an unknown perturbation in different physiological and/or mechanical perturbation environments. Aim: To characterize trunk neuromuscular adaptations following repeated sudden external perturbations after a back muscle fatigue task using high-density EMG. Methods: Twenty-five healthy participants experienced a series of 15 sudden external perturbations before and after back muscle fatigue. Erector spinae muscle activity was recorded using high-density EMG. Trunk kinematics during perturbation trials were collected using a 3-D motion analysis system. A two-way repeated measure ANOVA was conducted to assess: (1) the adaptation effect across trials; (2) the fatigue effect; and (3) the interaction effect (fatigue × adaptation) for the baseline activity, the reflex latency, the reflex peak and trunk kinematic variables (flexion angle, velocity and time to peak velocity). Muscle activity spatial distribution before and following the fatigue task was also compared using t-tests for dependent samples. Results: An attenuation of muscle reflex peak was observed across perturbation trials before the fatigue task, but not after. The spatial distribution of muscle activity was significantly higher before the fatigue task compared to post-fatigue trials. Baseline activity showed a trend to higher values after muscle fatigue, as well as reduction through perturbation trials. Main effects of fatigue and adaptation were found for time to peak velocity. No adaptation nor fatigue effect were identified for reflex latency, flexion angle or trunk velocity. Conclusion: The results show that muscle fatigue leads to reduced spatial distribution of back muscle activity and suggest a limited ability to use across-trial redundancy to adapt EMG reflex peak and optimize spinal stabilization using retroactive control.

Correlation of expertise with error detection skills of force application during spinal manipulation learning.

OBJECTIVE: Most studies on spinal manipulation learning demonstrate the relevance of including motor learning strategies in chiropractic curricula. Two outcomes of practice are the production of movement in an efficient manner and the improved capability of learners to evaluate their own motor performance. The goals of this study were to evaluate if expertise is associated with increased spinal manipulation proficiency and if error detection skills of force application during a high-velocity low-amplitude spinal manipulation are related to expertise. METHODS: Three groups of students and 1 group of expert chiropractors completed 10 thoracic spine manipulations on an instrumented device with the specific goal of reaching a maximum peak force of 300 N after a brief period of practice. After each trial, participants were asked to give an estimate of their maximal peak force. Force-time profiles were analyzed to determine the biomechanical parameters of each participant and the participant's capacity to estimate his or her own performance. RESULTS: Significant between-group differences were found for each biomechanical parameter. No significant difference was found between groups for the error detection variables (p > .05). The lack of significant effects related to the error detection capabilities with expertise could be related to the specificity of the task and how the training process was structured. CONCLUSION: This study confirms that improvements in biomechanical parameters of spinal manipulation are related to expertise. Feedback based on error detection could be implemented in chiropractic curricula to improve trainee abilities in detecting motor execution errors.

The effect of spinal manipulation impulse duration on spine neuromechanical responses.

INTRODUCTION: Spinal manipulation therapy (SMT) is characterized by specific kinetic and kinematic parameters that can be modulated. The purpose of this study is to investigate fundamental aspects of SMT dose-physiological response relation in humans by varying SMT impulse duration. METHODS: Twenty healthy adults were subjected to four different SMT force-time profiles delivered by a servo-controlled linear actuator motor and differing in their impulse duration. EMG responses of the left and right thoracic paraspinal muscles (T6 and T8 levels) and vertebral displacements of T7 and T8 were evaluated for all SMT phases. RESULTS: Significant differences in paraspinal EMG were observed during the "Thrust phase" and immediately after ("Post-SMT1") (all T8 ps < 0.01 and T6 during the thrust ps < 0.05). Sagittal vertebral displacements were similar across all conditions (p > 0.05). CONCLUSION: Decreasing SMT impulse duration leads to a linear increase in EMG response of thoracic paraspinal during and following the SMT thrust.

INTRODUCTION: La manipulation vertébrale (MV) se caractérise par des paramètres cinétiques et cinématiques particuliers qui peuvent être modulés. L'objet de la présente étude est d'examiner des aspects fondamentaux de la relation dose-réponse physiologique de la MV chez des humaines en faisant varier la durée de l'impulsion de la MV. MÉTHODOLOGIE: Vingt adultes en santé ont subi quatre différents profils force-temps de MV livrés au moyen d'un actuateur linéaire asservi et ayant des durées d'impulsion différentes. Les réponses EMG des muscles paravertébraux de gauche et de droite (au niveau des vertèbres T6 et T8) et les déplacements des vertèbres T7 et T8 ont été évalués pour toutes les phases de la MV. RÉSULTATS: Des différences considérables ont été observées dans l'EMG des muscles paravertébraux au cours de la phase de la « poussée ¼ et immédiatement après celle-ci (« post-MV1 ¼) (T8 : tous les p < 0,01 et T6 lors de la poussée : tous les p < 0,05). Les déplacements sagittaux des vertèbres étaient semblables dans toutes les situations (p < 0,05). CONCLUSION: Une réduction de la durée de l'impulsion de la MV entraîne une augmentation linéaire de la réaction à l'EMG des muscles paravertébraux thoraciques au cours de la poussée de la MV, et après celle-ci.

Learning spinal manipulation: a comparison of two teaching models.

PURPOSE: The goal of the present study was to quantify the high-velocity, low-amplitude spinal manipulation biomechanical parameters in two cohorts of students from different teaching institutions. The first cohort of students was taught chiropractic techniques in a patient-doctor positioning practice setting, while the second cohort of students was taught in a "complete practice" manipulation setting, thus performing spinal manipulation skills on fellow student colleagues. It was hypothesized that the students exposed to complete practice would perform the standardized spinal manipulation with better biomechanical parameters. METHODS: Participants (n = 88) were students enrolled in two distinct chiropractic programs. Thoracic spine manipulation skills were assessed using an instrumented manikin, which allowed the measurement of applied force. Dependent variables included peak force, time to peak force, rate of force production, peak force variability, and global coordination. RESULTS: The results revealed that students exposed to complete practice demonstrated lower time to peak force values, higher peak force, and a steeper rate of force production compared with students in the patient-doctor positioning scenario. A significant group by gender interaction was also noted for the time to peak force and rate of force production variables. CONCLUSION: The results of the present study confirm the importance of chiropractic technique curriculum and perhaps gender in spinal manipulation skill learning. It also stresses the importance of integrating spinal manipulation skills practice early in training to maximize the number and the quality of significant learner-instructor interactions.