Symptom Exacerbation and Adverse Events during a Randomized Trial of Early-stage Concussion Rehabilitation.

CONTEXT: Few studies utilize randomized clinical trials (RCT) to quantify clinical intervention safety of rehabilitation after sport-related concussion across sport levels. OBJECTIVE: Describe symptom exacerbation and adverse events (AEs) associated with two concussion rehabilitation interventions. DESIGN: Cluster Randomized Controlled Trial (XXX). SETTING: Sports medicine clinic and field settings. PARTICIPANTS: The RCT enrolled 251 concussed athletes (median age=20 years; female n=48) across 28 sites from New Zealand professional rugby (n=31), Canadian professional football (n=52), United States (U.S.)/Canadian colleges (n=128) and U.S. high schools (n=40). INTERVENTIONS: Two medically supervised interventions: 1) Enhanced Graded Exertion (EGE): international return to sport strategy and sport specific activities only (EGE-only n=119) and 2) Multidimensional Rehabilitation (MDR) followed by EGE: early symptom-directed exercises once symptoms were stable, followed by EGE after symptoms resolved (MDR+EGE n=132). MAIN OUTCOME MEASURES: Primary outcomes were intrasession total symptom severity score exacerbation and significant intersession (increase 10+ severity points) sustained total symptom severity exacerbation, each measured with a Postconcussion Symptom Scale (132 total severity points on scale). Reported AEs were also described. Activity-based rehabilitation sessions (n=1437) were the primary analysis unit. Frequencies, proportions, medians, and Interquartile Ranges (IQRs) were calculated for outcomes by treatment group. RESULTS: The 251 post-injury participants completed 1437 (MDR+EGE=819, EGE-only=618) activity-based intervention sessions. A total of 110 and 105 participants contributed data (those missing had no documented session data) to at least 1 activity-based session in the MDR+EGE and EGE-only arms respectively. Intrasession symptom exacerbations were equivilantly low in MDR+EGE and EGE-only arms (MDR+EGE: 16.7%, 95% CI:14.1%,19.1%; EGE-only: 15.7%, 95% CI: 12.8%,18.6%). In total, 9/819 MDR+EGE sessions (0.9%) and 1/618 EGE-only sessions (0.2%) resulted in a pre- to post-session symptom exacerbation beyond a 10+ severity point increase; 8/9 resolved to <10 points by the next session. Two study-related AEs (1 in each arm) were reported. CONCLUSIONS: Participants in MDR+EGE and EGE-only activities reported equivalently low rates of symptom exacerbation.

Parent influence on concussion reporting in first-year collegiate athletes.

OBJECTIVE: To assess the relationship between sport-parenting practices and concussion reporting intentions of collegiate athletes across two levels of competition. PARTICIPANTS: Entering first-year student-athletes (varsity and club) at a mid-sized university in the Southeast region of the United States (n = 327). METHODS: Written surveys were completed prior to the start of the 2015 academic year. Structural equation modeling was used to test a model predicting concussion-reporting intentions. RESULTS: College athletes were more likely to intend to report a suspected concussion when they believed their parents wanted them to report (B=-0.88, SD = 0.94), and when they experienced less sport achievement pressure from their parents (B=-0.12, SD = 8.07). CONCLUSIONS: Parents influence the concussion safety of entering collegiate athletes at both the varsity and club level. Lower pressure sport parenting prior to college entry may help foster safer concussion reporting behaviors and may be an appropriate target for future intervention development work.

Not Just for Dancing? A Content Analysis of Concussion and Head Injury Videos on TikTok.

Social media platforms are an accessible and increasingly used way for the public to gather healthcare-related information, including on sports injuries. "TikTok" is currently one of the fastest-growing social media platforms worldwide, and it is especially popular amongst adolescents and young adults. The widespread use and popularity of TikTok suggests that this platform has potential to be a source for healthcare information for younger individuals. The aim of this study was to gain a preliminary understanding of the concussion/head injury-related information on TikTok, and to gauge if TikTok could serve as a platform for concussion education. This exploratory study used a systematic search strategy to understand more about how concussion is being portrayed through TikTok videos. Using the keywords "concussion" and "head injury," 200 videos were downloaded from TikTok and 43 videos were excluded. Of the 92 videos retrieved using the keyword "concussion," 95% (n = 88) had more than 100,000 views and 6% (n = 10) had been viewed more than 10 million times. Over half, 54% (n = 50) of the "concussion" videos depicted individuals "playing around" and getting hit in the head, whilst only 1% (n = 1) of the TikTok videos were categorized as "explaining concussion facts." The large numbers of views of concussion-related TikTok videos demonstrates the popularity of this platform and indicates that healthcare organizations should consider TikTok as a potential means for concussion education amongst younger individuals.

Good Food, Good Mood: Perspectives on the Relationship Between Nutrition and Mental Health With Division I Collegiate Athletic Programs.

Research has shown a strong relationship between nutrition and mental health. Packed schedules and little rest time may make student-athletes more susceptible to mental health issues than the general population, but few athletes are fully aware of the effects that nutrition can have on their mental health. While collegiate athletic programs are beginning to recognize the individual contributions of nutrition and mental health to performance and are hiring sport dietitians and psychologists for their athletes, it is unclear whether these topics are ever discussed within the same context. The goal of this study was to understand the perspectives of different athletic personnel on the relationship between nutrition and mental health. 17 athletic personnel (11 Female, 6 Male) from 6 NCAA Division I universities were recruited for a 30-45-min semi-structured WebEx interview. Participants included athletic trainers, coaches, dietitians, sport psychologists, strength and conditioning coaches, and sports medicine physicians. Participants were asked questions about their educational backgrounds, resources, and perspectives on the integration of nutrition and mental health in their programs. Transcribed responses were sorted into four themes: (1) Resources, (2) Education, (3) Department Integration or Collaboration, and (4) Student and Coach Engagement. All participants reported a need for greater monetary resources and staffing. Around 59% of the participants felt they had little more than general or personal interest-level knowledge on topics pertaining to nutrition or mental health, with the exception of sports dietitians or psychologists. Each school varied in the degree to which their athletic staff regularly communicated about their work and athlete health statuses. Athletes were reportedly more or less likely to utilize the resources provided depending on coach attitudes toward nutrition or mental health. Regardless of size, reputation and annual spending, each university was reported to be in the early stages of integrating nutrition and mental health programs into their existing athletic departments. Implications of this work may be to help schools plan for ways to reallocate funding for nutrition or mental health programming.

Gait Assessment in College Athletes: Do Concussion History, Symptoms, Gender, and Type of Sport Matter?

CONTEXT: Though previous research has focused on examining the effects of concussion history using a dual-task paradigm, the influence of factors like symptoms (unrelated to concussion), gender, and type of sport on gait in college athletes is unknown. OBJECTIVE: To examine the effect of concussion history, symptoms, gender, and type of sport (noncontact/limited contact/contact) individually on gait among college athletes. DESIGN: Exploratory cross-sectional study. SETTING: Laboratory. PARTICIPANTS: In total, 98 varsity athletes (age, 18.3 [1.0] y; height, 1.79 [0.11] m; mass, 77.5 [19.2] kg; 27 with concussion history, 58 reported at least one symptom, 44 females; 8 played noncontact sports and 71 played contact sports) walked under single- and dual-task (walking while counting backward by 7) conditions. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Dual-task cost (DTC; % difference between single task and dual task) of gait speed, cadence, step length and width, percentage of swing and double-support phases, symptom score, and total symptom severity score. Independent samples t tests and 1-way analysis of variance were conducted (α value = .05). RESULTS: Self-reported concussion history resulted in no significant differences (P > .05). Those who reported symptoms at testing time showed significantly greater DTC of step length (mean difference [MD], 2.7%; 95% confidence interval [CI], 0.3% to 5.1%; P = .012), % of swing phase (MD, 1.0%; 95% CI, -0.2 to 2.1%; P = .042), and % of double-support phase (MD, 3.9%; 95% CI, 0.2% to 7.8%; P = .019). Females demonstrated significantly higher DTC of gait speed (MD, 5.3%; 95% CI, 1.3% to 9.3%; P = .005), cadence (MD, 4.0%; 95% CI, 1.4% to 6.5%; P = .002), % of swing phase (MD, 1.2%; 95% CI, 0.1% to 2.3%; P = .019), and % of double-support phase (MD, 4.1%; 95% CI, 0.4% to 7.9%; P = .018). Noncontact sports athletes had significantly greater step width DTC than contact sports athletes (MD, 14.2%; 95% CI, 0.9% to 27.6%; P = .032). CONCLUSIONS: Reporting symptoms at testing time may influence gait under dual-task conditions. Additionally, female athletes showed more gait changes during a dual task. Sports medicine professionals should be aware that these variables, while unrelated to injury, may affect an athlete's gait upon analysis.

Examination of clinical and laboratory measures of static and dynamic balance in breast cancer survivors.

Objectives: Balance in breast cancer survivors is understudied. Increased understanding of how postural control is affected when the body is stationary, moving, or engaged in a concurrent cognitive task, can aid clinicians who work with this population in identifying how altered postural control may indicate a potential functional decline. Therefore, the purpose of this study was to compare performance on several assessments of static and dynamic balance, with and without a concurrent cognitive task, in women with and without a history of breast cancer.Methods: Twenty-three women without a history of cancer (controls), and 20 women who were breast cancer survivors participated in the study. Static balance was assessed using the Single Leg Stance Test (SLS) and the NeuroCom Sensory Organization Test (SOT), the latter of which also included a serial sevens cognitive task. Dynamic balance was assessed using the Timed Up and Go Test (TUG) and the Fullerton Advanced Balance Scale (FABS).Results: Breast cancer survivors performed significantly worse on the TUG and the FABS compared to controls (p < .02). Performance on the SLS and SOT was largely similar between groups, including performance on the SOT with the serial sevens task (p > .05).Conclusion: Breast cancer survivors who were 0-5 years post-treatment appeared to exhibit similar static postural stability compared to controls, while some aspects of dynamic balance appeared altered. Assessing balance changes provides clinically useful information when constructing specific interventions aimed to improve function in these individuals post-treatment.

Turn Characteristics During Gait Differ With and Without a Cognitive Demand Among College Athletes.

CONTEXT: Sports often involve complex movement patterns, such as turning. Although cognitive load effects on gait patterns are well known, little is known on how it affects biomechanics of turning gait among athletes. Such information could help evaluate how concussion affects turning gait required for daily living and sports. OBJECTIVE: To determine the effect of a dual task on biomechanics of turning while walking among college athletes. DESIGN: Cross-sectional study. SETTING: University laboratory. PARTICIPANTS: Fifty-three participants performed 5 trials of a 20-m walk under single- and dual-task conditions at self-selected speed with a 180° turn at 10-m mark. The cognitive load included subtraction, spelling words backward, or reciting the months backward. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Turn duration, turning velocity, number of steps, SD of turn duration and velocity, and coefficient of variation of turn duration and velocity. RESULTS: Participants turned significantly slower (155.99 [3.71] cm/s vs 183.52 [4.17] cm/s; P < .001) and took longer time to complete the turn (2.63 [0.05] s vs 2.33 [0.04] s; P < .001) while dual tasking, albeit taking similar number of steps to complete the turn. Participants also showed more variability in turning time under the dual-task condition (SD of turn duration = 0.39 vs 0.31 s; P = .004). CONCLUSIONS: Overall, college athletes turned slower and showed more variability during turning gait while performing a concurrent cognitive dual-task turning compared with single-task turning. The slower velocity increased variability may be representative of specific strategy of turning gait while dual tasking, which may be a result of the split attention to perform the cognitive task. The current study provides descriptive values of absolute and variability turning gait parameters for sports medicine personnel to use while they perform their concussion assessments on their college athletes.

Baseline Neurocognitive Performance and Symptoms in Those With Attention Deficit Hyperactivity Disorders and History of Concussion With Previous Loss of Consciousness.

Previous consensus statements on sports concussion have highlighted the importance of Attention Deficit Hyperactivity Disorder (ADHD) and loss of consciousness (LOC) as risk factors related to concussion management. The present study investigated how self-reported history of either ADHD diagnosis or history of previous concussion resulting in LOC influence baseline neurocognitive performance and self-reported symptoms. This analysis was performed retrospectively on data collected primarily from student-athletes, both Division 1 and club sports athletes. The dataset (n = 1460) is comprised of college students (age = 19.1 ± 1.4 years). Significant differences were found for composite scores on the ImPACT for both history of concussion (p = 0.016) and ADHD (p = 0.014). For concussion history, those with a previous concussion, non-LOC, performed better on the visual motor speed (p = 0.004). Those with diagnosis of ADHD performed worse on verbal memory (p = 0.001) and visual motor speed (p = 0.033). For total symptoms, concussion history (p < 0.001) and ADHD (p = 0.001) had an influence on total symptoms. Those with ADHD reported more symptoms for concussion history; those with previous LOC concussion reported more symptoms than those with non-LOC concussion (p = 0.003) and no history (p < 0.001). These results highlight the importance of baseline measures of neurocognitive function and symptoms in concussion management in order to account for pre-existing conditions such as ADHD and LOC from previous concussion that could influence these measures.

Concussion history influences sleep disturbances, symptoms, and quality of life in collegiate student-athletes.

OBJECTIVES: Immediately after experiencing a concussion, many will report the presence of a variety of symptoms, which may include disturbances in sleep. It is possible that these symptoms and other resulting quality of life (QOL) disturbances may persist for some time following a concussion. The purpose of this study was to determine if a history of concussions was related to ongoing sleep disturbances, symptoms, and changes in QOL. METHODS: Eighty-two student-athletes (club and varsity) completed an online survey to determine concussion history, sleep disturbances, concussion symptoms, and QOL dysfunctions. Separate analyses of variance were performed to determine if sleep disturbances, symptoms, and QOL dysfunctions were related and if they differed based on concussion history (0, 1-2, 3+). RESULTS: Those with no concussion history reported fewer sleep disturbances (P = .028), symptoms (P = .029), symptom severity (P = .014), QOL dysfunctions (P = .003), and QOL severity (P = .011) than those who self-reported having had a previous concussion(s). Additionally, the number of sleep disturbances was found to positively correlate with symptoms (P < .001), symptom severity (P < .001), QOL dysfunctions (P = .001), and severity of QOL dysfunctions (P = .002). CONCLUSIONS: The results of the current study demonstrate that concussion history is related to persistent changes in sleep, ongoing symptoms, and QOL dysfunctions and should be considered in concussion management protocols even after return to play and academics has occurred.

Influence of Concussion History and Genetics on Event-Related Potentials in Athletes: Potential Use in Concussion Management.

Sports-related concussions are an increasing public health issue with much concern about the possible long-term decrements in cognitive function and quality of life that may occur in athletes. The measurement of cognitive function is a common component of concussion management protocols due to cognitive impairments that occur after sustaining a concussion; however, the tools that are often used may not be sensitive enough to expose long term problems with cognitive function. The current paper is a brief review, which suggests that measuring cognitive processing through the use of event related potentials (ERPs) may provide a more sensitive assessment of cognitive function, as shown through recent research showing concussion history to influence ERPs components. The potential influence of genetics on cognitive function and ERPs components will also be discussed in relation to future concussion management.

The effects of unstable surface balance training on postural sway, stability, functional ability and flexibility in women.

BACKGROUND: This study examined the effects of balance training routine, using both sides utilized balance trainer (BOSU) and aerobic step (STEP) on postural sway and functional ability in middle-aged women. METHODS: Twenty-seven females participated in the study, age 40.6±12.0 years, body mass 72.0±14.0 kg, height 164.0±7.7 cm, BMI 26.5±4.5 kg/m2, and relative body fat 33.1±7.4%. Participants were divided into two groups and performed progressive exercise routine on either STEP or BOSU for three weeks. Pre- and post-test consisted of Postural Sway Test performed on the Biodex Balance System, Functional Ability Test, Sit and Reach Test and Plank. RESULTS: A significant time effect was observed for both groups for sway index(P=0.029) and center of pressure antero-posterior (AP) displacement (P=0.038) but not for sway area or medio-lateral (ML) displacement (P>0.05). In addition, BOSU group had significantly lower Sway Index(P=0.048) and ML range (P=0.035) scores when vision and surface was altered compared to STEP group. A significant time effect was observed in walking-up the stairs (P=0.020), sit and reach test (P=0.035), and plank (P<0.001), but not for walking down the stairs. However, no other significant interactions were observed. CONCLUSIONS: Programs that incorporate multisensory balance training have a potential to induce adaptive responses in neuromuscular system that enhances postural control, balance and functional ability of women. The training using BOSU may help improve static balance and functional ability in women.

Genetics Influence Neurocognitive Performance at Baseline but Not Concussion History in Collegiate Student-Athletes.

OBJECTIVE: This study investigates 4 single-nucleotide polymorphisms [Apolipoprotein E (APOE), APOE promoter, catechol-O-methyl transferase (COMT), and dopamine D2 receptor] that have been implicated in concussion susceptibility and/or cognitive ability in collegiate student-athletes. DESIGN: Cross-sectional study. SETTING: Neuroscience laboratory at Elon University. PARTICIPANTS: Two hundred fifty division I collegiate student-athletes (66 women, 184 men) from various sports. INTERVENTION: All participants completed Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) testing at baseline concussion testing and had a buccal swab taken for DNA for genotyping. MAIN OUTCOME MEASURES: Self-reported history of concussions and neurocognitive performance were taken from ImPACT. RESULTS: Individuals carrying an ε4 allele in their APOE gene had a significantly slower reaction time (P = 0.001). Individuals homozygous for the Val allele of the COMT gene showed significantly worse impulse control scores (P = 0.014). None of the genotypes were able to predict self-reported concussion history in collegiate student-athletes. CONCLUSIONS: These results indicate that certain genotypes may influence performance on cognitive testing at baseline and that the APOE genotypes may not influence concussion susceptibility as suggested by past studies.

Concussion Baseline Testing: Preexisting Factors, Symptoms, and Neurocognitive Performance.

CONTEXT: Neurocognitive test scores are often considered an important aspect of concussion management. To best use these data, clinicians must understand potential factors that may influence baseline performance on these tests. OBJECTIVE: To determine preexisting factors that may influence performance on the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT). DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 486 National Collegiate Athletic Association Division I collegiate student-athletes. MAIN OUTCOME MEASURE(S): To determine neurocognitive functioning and total symptom score at baseline, ImPACT was administered. Outcomes were verbal memory, visual memory, visual motor speed, reaction time, and total symptom score. A self-report demographic section at the beginning of ImPACT was used to gather information concerning previous treatment for headaches, migraines, and psychiatric conditions; diagnosis of attention-deficit/hyperactivity disorder; and exposure to previous strenuous exercise. We conducted multivariate analyses of variance to determine if the ImPACT composite and total symptom scores differed according to preexisting factors (P < .0083). RESULTS: Sex showed an effect on verbal memory (P = .001), visual motor speed (P < .001), and reaction time (P = .006), with women performing better than men. A previous diagnosis of attention-deficit/hyperactivity disorder affected visual motor speed (P = .008). Previous treatment for headaches (P < .001), migraines (P = .001), a psychiatric condition (P < .001), or a diagnosis of attention-deficit/hyperactivity disorder (P < .001) all showed effects on the total symptom score. Strenuous exercise did not affect neurocogntive performance or total symptom score. CONCLUSIONS: Based on our findings and the previous literature, we suggest that many preexisting factors influence baseline neurocognitive data. Baseline testing is an important aspect of concussion management. Sports medicine professionals should be cognizant of these factors when developing concussion-management protocols.

Single-Task and Dual-Task Gait Among Collegiate Athletes of Different Sport Classifications: Implications for Concussion Management.

Gait impairments have been documented following sport-related concussion. Whether preexisting gait pattern differences exist among athletes who participate in different sport classifications, however, remains unclear. Dual-task gait examinations probe the simultaneous performance of everyday tasks (ie, walking and thinking), and can quantify gait performance using inertial sensors. The purpose of this study was to compare the single-task and dual-task gait performance of collision/contact and noncontact athletes. A group of collegiate athletes (n = 265) were tested before their season at 3 institutions (mean age= 19.1 ± 1.1 years). All participants stood still (single-task standing) and walked while simultaneously completing a cognitive test (dual-task gait), and completed walking trials without the cognitive test (single-task gait). Spatial-temporal gait parameters were compared between collision/contact and noncontact athletes using MANCOVAs; cognitive task performance was compared using ANCOVAs. No significant single-task or dual-task gait differences were found between collision/contact and noncontact athletes. Noncontact athletes demonstrated higher cognitive task accuracy during single-task standing (P = .001) and dual-task gait conditions (P = .02) than collision/contact athletes. These data demonstrate the utility of a dual-task gait assessment outside of a laboratory and suggest that preinjury cognitive task performance during dual-tasks may differ between athletes of different sport classifications.

Evidence of a conservative gait strategy in athletes with a history of concussions.

BACKGROUND: A history of 3 or more concussions is frequently associated with numerous short- and long-term neuropathologies. Impairments in postural control are a known acute consequence of concussion; however, limited evidence exists on the effects of multiple concussions on gait. The purpose of this study was to assess gait stepping characteristics in collegiate aged student-athletes based on concussion history. METHODS: There were 63 participants divided into 3 even groups based on concussion history: ≥3 concussions, 1-2 concussions, and 0 concussion. All participants completed 10 trials of gait on a 4.9 m instrumented walkway. The dependent variables of interest included both gait stepping characteristics (step velocity, length, and width, double support time, and the percentage of the gait cycle in stance) and coefficient of variability (CoV) measures (step length, time, and width). The gait stepping characteristics were compared first with a MANOVA with follow-up 1-way ANOVAs and Tukey post hoc tests as appropriate. The CoV measures were compared with 1-way ANOVAs and Tukey post hoc tests. RESULTS: There were main effects for group for step velocity, length, width, and double support time. Overall, the 0 concussion group displayed typical healthy young gait parameters and performed significantly better than either concussion group. The 0 concussion group had a significantly greater step length CoV, but there were no differences in the step time or width CoV. CONCLUSION: This finding provides evidence of subtle impairments in postural control during gait among individuals with prior history of concussion which could be an early indicator of future neurological deficiencies. The limited difference in the variability measures is consistent with prior static stance studies and could suggest the individuals constrain their motor systems to reduce variability. Taken together, these findings suggest a conservative gait strategy which is adopted by individuals with a history of concussions.

Concussion management in collegiate student-athletes: return-to-academics recommendations.

Concussions in collegiate athletics can affect student-athletes both on the field and in the classroom. As policies are made to outline return-to-play decisions and timelines, this article will make the case that return-to-academics should also be included and follow a step-wise protocol. Complete cognitive rest is a cornerstone of concussion recovery and slow reintroduction to academics should precede return-to-play. The college structure allows for student-athletes to begin small doses of cognitive activity after the recommended complete cognitive rest. It is recommended that return-to-academics involves a team approach to help the student-athlete navigate the responsibilities of course work while healing from a brain injury.

A neuroscientific approach to the examination of concussions in student-athletes.

Concussions are occurring at alarming rates in the United States and have become a serious public health concern. The CDC estimates that 1.6 to 3.8 million concussions occur in sports and recreational activities annually. Concussion as defined by the 2013 Concussion Consensus Statement "may be caused either by a direct blow to the head, face, neck or elsewhere on the body with an 'impulsive' force transmitted to the head." Concussions leave the individual with both short- and long-term effects. The short-term effects of sport related concussions may include changes in playing ability, confusion, memory disturbance, the loss of consciousness, slowing of reaction time, loss of coordination, headaches, dizziness, vomiting, changes in sleep patterns and mood changes. These symptoms typically resolve in a matter of days. However, while some individuals recover from a single concussion rather quickly, many experience lingering effects that can last for weeks or months. The factors related to concussion susceptibility and the subsequent recovery times are not well known or understood at this time. Several factors have been suggested and they include the individual's concussion history, the severity of the initial injury, history of migraines, history of learning disabilities, history of psychiatric comorbidities, and possibly, genetic factors. Many studies have individually investigated certain factors both the short-term and long-term effects of concussions, recovery time course, susceptibility and recovery. What has not been clearly established is an effective multifaceted approach to concussion evaluation that would yield valuable information related to the etiology, functional changes, and recovery. The purpose of this manuscript is to show one such multifaceted approached which examines concussions using computerized neurocognitive testing, event related potentials, somatosensory perceptual responses, balance assessment, gait assessment and genetic testing.

Identifying leading joint strategies in a bimanual coordination task: does coordination stability depend on leading joint strategy?

The authors sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint, bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates with an isodirectional motion of the end effectors (both hands moving counterclockwise [CCW]) at two cycling frequencies. Ellipse templates were oriented either tilted right or tilted left, yielding a total of 4 left arm-right arm leading-joint combinations. Analysis of torque sign and impulse data indicated that the 4 ellipse-tracing conditions resulted in 4 distinct left arm-right arm leading-joint combinations: 2 conditions with similar leading joints and 2 conditions with different leading joints. Isodirectional CCW ellipse tracing was more stable when produced with similar leading joints compared with when produced with different leading joints. The authors discuss results within the context of intralimb control contributions to the stability of interlimb coordination patterns.

Targeted aiming movements are compromised in nonaffected limb of persons with stroke.

BACKGROUND: Research has shown that movement impairments following stroke are typically associated with the limb contralateral to the side of the stroke. Prior studies identified ipsilateral motor declines across a variety of tasks. OBJECTIVE: Two experiments were conducted to better understand the ipsilateral contributions to organization and execution of proximal upper extremity multisegment aiming movements in persons with right-hemispheric stroke. METHODS: Participants performed reciprocal aiming (Experiment 1) and 2-segment aiming movements (Experiment 2) on a digitizing tablet. In both experiments, target size and/or target orientation were manipulated to examine the influence of accuracy constraints on the planning and organization of movements. RESULTS: Kinematic measures, submovement analysis, and harmonicity measures were included in this study. Declines in organization and execution of multisegment movements were found to contribute to performance decrements and slowing in stroke patients. Furthermore, stroke patients were unable to efficiently plan multisegment movements as one functional unit, resulting in discrete movements. CONCLUSIONS: Results suggest the importance of considering ipsilateral contributions to the control and organization of targeted aiming movements as well as implications for rehabilitation and recovery.

Efficient control of arm movements in advanced age.

The present study addresses the influence of aging on the ability to regulate mechanical effects arising during arm movements due to the multi-joint structure of the arm. Two mechanical factors were considered, interaction torque (IT) and inertial resistance (IR). Regulation of these two factors can be demanding in terms of the timing and magnitude of the required muscle torque (MT), specifically during fast movements. We hypothesized that aging exacerbates the challenge regarding the regulation of these effects with muscular control due to declines in the motor system. This hypothesis was tested by comparing performance of a cyclic line-drawing task in two age groups, young and older adults. Only two joints, the shoulder and elbow, participated in motion. Four orientations of the lines were used to provide variations in the requirements for regulation of IT and IR. Cyclic frequency was manipulated to emphasize the dependence of the mechanical factors on movement speed. Various characteristics of fingertip motion showed that there were no age-related deteriorations in accuracy of line drawing. However, older adults were systematically slower, particularly in the directions of high IR. A detailed analysis of the magnitude of MT and the contribution of this torque to production of net torque at each joint demonstrated that older adults modified joint control and decreased the demands for MT by skillful exploitation of IT in a way specific for each particular line orientation. The results point to a tendency in older adults to decrease the production of muscle force. Nevertheless, older adults also demonstrated an ability to partially compensate for declines in the force production by developing sophisticated strategies of joint control that exploit the multi-joint mechanical structure of the arm. This ability suggests that the internal representation of inter-segmental dynamics and the capability to use it for movement control does not decay with age. The study emphasizes the importance of analysis of joint motion and control characteristics for the investigation of arm movements and for comparison of these movements between different subject populations.