Short term effects of contralateral tendon vibration on motor unit discharge rate variability and force steadiness in people with Parkinson's disease.

Background: Vibration of one limb affects motor performance of the contralateral limb, and this may have clinical implications for people with lateralized motor impairments through vibration-induced increase in cortical activation, descending neural drive, or spinal excitability. Objective: The objective of this study was to evaluate the effects of acute biceps brachii tendon vibration on force steadiness and motor unit activity in the contralateral limb of persons with Parkinson's disease. Methods: Ten participants with mild to moderate Parkinson's disease severity performed a ramp, hold and de-ramp isometric elbow flexion at 5% of maximum voluntary contraction with the more-affected arm while vibration was applied to the distal biceps brachii tendon on the contralateral, less-affected arm. Using intramuscular fine wire electrodes, 33 MUs in the biceps brachii were recorded across three conditions (baseline, vibration, and post-vibration). Motor unit recruitment & derecruitment thresholds, discharge rates & variability, and elbow flexion force steadiness were compared between conditions with and without vibration. Results: Coefficient of variation of force and discharge rate variability decreased 37 and 17%, respectively in post-vibration compared with baseline and vibration conditions. Although the motor unit discharge rates did not differ between conditions the total number of motor units active at rest after de-ramp were fewer in the post-vibration condition. Conclusion: Contralateral tendon vibration reduces MU discharge rate variability and enhances force control on the more affected side in persons with Parkinson's disease.

Older Canadians' Perceptions of the Safety, Effectiveness and Accessibility of Cannabis for Medicinal Purposes: A Cross-Sectional Analysis.

BACKGROUND AND OBJECTIVE: Cannabis use is increasing among older adults, with use primarily for medicinal purposes. Much of the evidence on perceptions of cannabis is derived from younger populations and current users of cannabis. The purpose of this study was to describe community-dwelling older Canadians' perceptions of cannabis effectiveness, safety and accessibility for medicinal purposes and to identify factors influencing cannabis perceptions. METHODS: An online survey of older adults' perceptions, knowledge and experiences with cannabis was completed between February and September 2022. The survey was open to English-speaking and French-speaking Canadians aged 50 years and older regardless of their cannabis use history. RESULTS: A total of 1615 Canadians completed the survey. Respondents identified primarily as men (49.7%) or women (48.5%) of Caucasian decent. The majority of participants viewed cannabis as a reasonable alternative (65.8%) and an effective (70.5%) treatment modality for symptom management in older adults. Few respondents (16.4%) felt that older adults compared to younger adults were at a higher risk of side effects and 34.5% felt that cannabis is safe to use with most medicines. Cannabis perceptions were influenced by gender, cannabis use history (prior use vs current use) and reasons for cannabis use (recreational purposes vs medicinal purposes vs both purposes). CONCLUSIONS: Older Canadians have a positive view of the role of cannabis in symptom management. The perceptions of cannabis safety and effectiveness were influenced by gender, cannabis use history and reasons for cannabis use. Healthcare professionals should leverage these perceptions when discussing cannabis with their older patient populations.

Hunting can increase physical activity of Indigenous peoples in Canada: pixem re yecwme'nstut.

This study examined whether Indigenous peoples could achieve the Canadian Physical Activity Guidelines (CPAG) for adults while engaging in the cultural practice of hunting. It was hypothesized that Indigenous hunters would achieve or surpass the physical activity (PA) thresholds set forth by the CPAG on days spent hunting. Step count and heart rate were recorded from six male participants during mule deer hunts and days spent on-reserve. Step count was not statistically different between days spent hunting (28 803 ± 10 657 steps) and on-reserve (15 086 ± 7536 steps) (p = 0.10). Time spent in light (257 ± 45 min; p = 0.04), moderate (118 ± 71 min; p = 0.03), and vigorous (45 ± 42 min; p = 0.04) activities while hunting was greater than on-reserve (light, 180 ± 86; moderate, 71 ± 73; vigorous, 7 ± 10 min). The duration of moderate-to-vigorous PA (119 ± 95 min) for an average day hunting nearly meets the weekly CPAG recommendation of 150 min per week and is 1.8× greater than on-reserve (67 ± 80 min). Data suggest that hunting is probably a viable mode of PA for Indigenous adults to achieve health benefits. A strength of this study is the 10 h of daily recording which includes vehicular transportation to remote hunting areas. The duration of very light/sedentary PA did not differ between hunting (233 ± 211 min) and on-reserve (327 ± 164 min; p = 0.10), and highlights the importance of modernized vehicles in traditional Indigenous activities. A larger sample size would facilitate greater exploration of transportation, as well as success of the hunt on PA. These data suggest that health researchers and clinicians should consider traditional activities such as hunting as a means for Indigenous adults to increase participation in sufficiently vigorous PA to incur health benefits.

Daily solitude and well-being associations in older dyads: Evidence from daily life assessments.

Older adults spend significant time by themselves, especially since COVID-19. Solitude has been associated with positive and negative outcomes. Partners need to balance social connectedness with time for one's own needs. This project examines how individual and partner solitude are associated with daily affect and relationship quality in dyads of older adults and a close other. One-hundred thirty-six older adults plus a close other rated their relationship quality and reported affect, solitude, and its characteristics (desired and bothersome) every evening for 10 days. Over and above overall associations, individual and partner effects emerged; when individual desired solitude was up, participants reported more positive affect and their partners less negative affect. When bothersome solitude was up, participants and their partners alike reported more negative affect and less positive affect. Desired solitude was associated with more support, whereas bothersome solitude was associated with less partner support. Findings provide further evidence on the potential benefits of solitude, highlighting the importance of considering the social context of what is often believed to be an individual-level phenomenon.

Daily Rumination-Affect Associations in Dyads During the COVID-19 Pandemic.

OBJECTIVES: Negative and repetitive self-oriented thinking (rumination) is associated with lower well-being and health. The social context of rumination remains underexplored and mostly centers on marital relationships. To embrace the diversity of older adult relationships, this study includes a range of different relationships (e.g., spouses, siblings, friends, etc.) and examines the role of rumination by close others on individual well-being during the coronavirus disease 2019 pandemic. METHODS: Using daily diary data from 140 Canadian older adults (M = 72.21 years, standard deviation [SD] = 5.39, range: 63-87 years, 47% women, 71% university educated) and a close other of their choice (M = 59.95 years, SD = 16.54, range: 18-83 years, 78% women, 81% university educated), this project builds on past research examining daily life rumination dynamics from a dyadic perspective. For 10 days, both dyad members reported their daily rumination and affect quality in the evening. RESULTS: Multilevel models replicate past work showing that individual rumination was associated with higher negative affect (within-person: b = 0.27, p < .001, between-person: b = 0.57, p < .001) and lower positive affect (within-person: b = -0.18, p < .001, between-person: b = -0.29, p < .001). Importantly, we additionally observed that partner rumination was associated with higher negative affect (b = 0.03, p = .038) and lower positive affect (b = -0.04, p = .023), highlighting the social context of rumination. DISCUSSION: Findings illustrate the significance of rumination for the self and others and underline the merit of taking a dyadic perspective on what is typically viewed as an individual-level phenomenon.

The influence of assistive technology and home modifications on falls in community-dwelling older adults: a systematic review protocol.

BACKGROUND: Fall-related injuries can reduce older adults' independence and result in economic burdens. The assistive technologies and home modifications explored in this review are suggested to reduce the risk of falls of community-dwelling older people. However, the location of the in-home assistive technology being used, and the in-home modification likely interact and influence fall reduction and injury prevention of community-dwelling older adults. This interactive effect is poorly understood. A better understanding of the impact of assistive technologies and modifications in the homes of older adults is needed to support the appropriate application of these devices. OBJECTIVE: The objective of this systematic review is to detail the contribution of assistive technology and home modification on falls, fall frequency, fall severity, and fall location within the homes of community-dwelling older adults. METHODS: We will source articles from 3 databases (MEDLINE, CINAHL, Web of Science Core Collection) and will assess them using a set of pre-defined inclusion and exclusion criteria. Reporting will be in accordance with PRISMA 2020. Two independent reviewers will screen each study at the title and abstract and full-text level. We are managing citations within the Covidence software. Data extraction and analysis will be reported in a systematic review. DISCUSSION: The outcome variables of interest are fall frequency, fall location, injury, mortality, and hospitalization. These variables of interest all relate to falls, their severity, and their locations in the home. We are seeking a better understanding of how these outcomes vary with the use of different assistive technologies and home modifications as reported in the literature. This will help us understand where falls occur which may inform how different assistive technologies can be used by community-dwelling older adults to prevent falls and adverse outcomes in different areas of their homes. Our review will provide a basis for more intentional prescription of ambulatory assistive technologies and evidence-based recommendations of home modifications. It may also inform adaptations to existing technologies to foster safer mobility in the homes of community-dwelling older adults. SYSTEMATIC REVIEW REGISTRATION: This protocol has been submitted for registration in PROSPERO CRD42022370172 on October 24, 2022.

A systematic review of how cannabinoids affect motoneuron output.

Spinal motoneurons contain many ion channels and receptors upon which various cannabinoids are known to act. This scoping review involved the synthesis of evidence from literature published before August 2022 about the effects of cannabinoids on quantifiable measures of motoneuron output. Four databases (MEDLINE, Embase, PsycINFO, and Web of Science CoreCollection) were queried and 4,237 unique articles were retrieved. Twenty-three studies met the inclusion criteria, and the findings from these studies were grouped according to four emergent themes: rhythmic motoneuron output, afferent feedback integration, membrane excitability, and neuromuscular junction transmission. This synthesis of evidence suggests that CB1 agonists can increase the frequency of cyclical patterns of motoneuron output (i.e., fictive locomotion). Furthermore, a majority of the evidence indicates that activating CB1 receptors at motoneuron synapses promotes excitation of motoneurons by enhancing excitatory synaptic transmission and depressing inhibitory synaptic transmission. The collated study results reveal variable effects of cannabinoids on acetylcholine release at the neuromuscular junction, and the influence of cannabinoids in this area requires more work to ensure precision of findings for CB1 agonist and antagonist impact. Altogether, these reports indicate that the endocannabinoid system is integral within the final common pathway and can impact motor output. This review contributes to understanding the effects of endocannabinoids on synaptic integration at the motoneuron and modulation of motor output.

Intermuscular coherence of plantar and dorsiflexor muscles in older adults with Parkinson's disease and age-matched controls during bipedal and unipedal stance.

Introduction: Postural instability increases with age and is exacerbated in neurological disorders such as Parkinson's disease (PD). Reducing the base of support from bipedal to unipedal stance increases center of pressure (CoP) parameters and intermuscular coherence in lower-leg muscles of healthy older adults. To further develop an understanding of postural control in an altered state of neurological impairment, we explored intermuscular coherence in lower-leg muscles and CoP displacement in older adults with PD. Methods: This study measured surface EMG from the medial (MG) and lateral (LG) gastrocnemii, soleus (SOL), and tibialis anterior (TA), and examined EMG amplitude and intermuscular coherence during bipedal and unipedal stance on a force plate with firm (no foam) and compliant (standing on foam) surface conditions in nine older adults with PD (70±5 years, 6 females) and 8 age-matched non-Parkinsonian older adults (5 females). Intermuscular coherence was analyzed between agonist-agonist and agonist-antagonist muscle pairs in the alpha (8-13 Hz) and beta (15-35 Hz) frequency bands. Results: CoP parameters increased from bipedal to unipedal stance in both groups (p < 0.01), but did not increase from the firm to compliant surface condition (p > 0.05). During unipedal stance, CoP path length was shorter in older adults with PD (2027.9 ± 1074.1 mm) compared to controls (3128.5 ± 1198.7 mm) (p < 0.01). Alpha and beta agonist-agonist and agonist-antagonist coherence increased by 28% from bipedal to unipedal stance (p > 0.05), but did not differ between older adults with PD (0.09 ± 0.07) and controls (0.08 ± 0.05) (p > 0.05). The older adults with PD also had greater normalized EMG amplitude of the LG (63.5 ± 31.7%) and TA (60.6 ± 38.4%) during the balance tasks (p > 0.05) than the non-Parkinsonian counterparts. Discussion: Older adults with PD had shorter path lengths during unipedal stance and required greater muscle activation than older adults without PD to perform the tasks, but intermuscular coherence did not differ between the groups. This may be attributable to their early disease stage and high motor function.

Shoulder electromyography activity during push-up variations: a scoping review.

Background: Push-ups (PU) are a common closed chain exercise used to enhance shoulder girdle stability, with variations that alter the difficulty or target specific muscles. To appropriately select and prescribe PU exercises, an understanding of muscle activity during variations of the PU is needed. The purpose of this scoping review was to identify common PU variations and describe their muscle activation levels. Methods: Databases searched included PubMed, CINAHL, Scopus, and SPORTDiscus for articles published between January 2000 and November 2019. Results: Three hundred three articles were screened for eligibility with 30 articles included in the analysis. Six PU types and five muscles met the criteria for analysis. Weighted mean electromyography (EMG) amplitude was calculated for each muscle across PU types and for each PU type as a measure of global muscle activity. Triceps and pectoralis major had the highest EMG amplitude during unstable, suspension, incline with hands on a ball and the standard PU. Serratus anterior had the highest EMG amplitude during PU plus and incline PU. The greatest global EMG amplitude occurred during unstable surface PU. Discussion: These results provide clinicians with a framework for prescribing PU to target specific muscles and scale exercise difficulty to facilitate rehabilitation outcomes.

Participation value of undergraduate students leading STEM outreach: evaluation of academic, personal, and professional effects.

This study explores the academic, professional, and personal career benefits of leading science, technology, engineering, and mathematics (STEM) outreach, from the perspective of undergraduate student leaders. We consider traditional and nontraditional STEM university students, gender, and type of position (paid or volunteer) in this evaluation. Data were collected through an online survey completed by 30 former student STEM outreach leaders from the University of British Columbia. Self-reported survey data indicated that STEM outreach had a moderately strong average impact of 6.89 ± 1.55 out of 10 on participants' personal, academic, and professional development, with no significant differences between these areas. Outcomes did not differ between genders, and paid work was found to contribute to greater personal and professional impact. The positive influence of outreach on academic and professional decision making was higher in traditional STEM fields than STEM-based health-science studies. The outcomes of this research adds insight into positive impacts of STEM outreach on university student instructors.

Resting Tendon Cross-Sectional Area Underestimates Biceps Brachii Tendon Stress: Importance of Measuring During a Contraction.

Force produced by the muscle during contraction is applied to the tendon and distributed through the cross-sectional area (CSA) of the tendon. This ratio of force to the tendon CSA is quantified as the tendon mechanical property of stress. Stress is traditionally calculated using the resting tendon CSA; however, this does not take into account the reductions in the CSA resulting from tendon elongation during the contraction. It is unknown if calculating the tendon stress using instantaneous CSA during a contraction significantly increases the values of in vivo distal biceps brachii (BB) tendon stress in humans compared to stress calculated with the resting CSA. Nine young (22 ± 1 years) and nine old (76 ± 4 years) males, and eight young females (21 ± 1 years) performed submaximal isometric elbow flexion tracking tasks at force levels ranging from 2.5 to 80% maximal voluntary contraction (MVC). The distal BB tendon CSA was recorded on ultrasound at rest and during the submaximal tracking tasks (instantaneous). Tendon stress was calculated as the ratio of tendon force during contraction to CSA using the resting and instantaneous measures of CSA, and statistically evaluated with multi-level modeling (MLM) and Johnson-Neyman regions of significance tests to determine the specific force levels above which the differences between calculation methods and groups became statistically significant. The tendon CSA was greatest at rest and decreased as the force level increased (p < 0.001), and was largest in young males (23.0 ± 2.90 mm2) followed by old males (20.87 ± 2.0 mm2) and young females (17.08 ± 1.54 mm2) (p < 0.001) at rest and across the submaximal force levels. Tendon stress was greater in the instantaneous compared with the resting CSA condition, and young males had the greatest difference in the values of tendon stress between the two conditions (20 ± 4%), followed by old males (19 ± 5%), and young females (17 ± 5%). The specific force at which the difference between the instantaneous and resting CSA stress values became statistically significant was 2.6, 6.6, and 10% MVC for old males, young females, and young males, respectively. The influence of using the instantaneous compared to resting CSA for tendon stress is sex-specific in young adults, and age-specific in the context of males. The instantaneous CSA should be used to provide a more accurate measure of in vivo tendon stress in humans.

Elevating neuroscience literacy and an approach for physiologists.

The field of neuroscience has made notable strides that have contributed to progress and change in a number of academic pursuits. However, the lack of understanding of basic neuroscience concepts among the general public is likely to hinder, and in some instances possibly even prevent, the appropriate application of scientific advancements to issues facing society today. Greater neuroscience literacy among the general public is necessary for the benefits of neuroscientific discovery to be fully realized. By actively enhancing neuroscience literacy, scientists can dispel falsehoods established by early research that harmed underrepresented communities, ensure that public conversations concerning neuroscience (e.g., legalization of psychotropic substances) revolve around facts, and empower individuals to make better health decisions. The widespread implementation of communication technologies and various forms of media indicate there are numerous means to engage classroom learners across disciplines and age cohorts and the public to increase neuroscience knowledge. Thus, it is not only necessary but timely that neuroscientists seek meaningful ways to bridge the widening knowledge gap with the public.

Contribution of Achilles tendon mechanical properties to torque steadiness in persons with transfemoral amputation.

BACKGROUND: How Achilles tendon mechanics and plantar flexion strength and torque steadiness are altered in the intact leg of persons with trauma-related amputation is unknown. Understanding Achilles tendon mechanics following amputation will further inform rehabilitation approaches to enhance posture, balance, and force control. OBJECTIVE: Conduct a pilot study to quantify plantar flexion maximal voluntary contraction torque, torque steadiness, and Achilles tendon mechanics in persons with unilateral trauma-related transfemoral amputation and controls without amputation. STUDY DESIGN: Cross-sectional study. METHODS: Isometric plantar flexion maximal voluntary contractions were performed with the intact leg of ten males with transfemoral amputation (48 ± 14 years) and the dominant leg of age-matched male controls without amputation. Torque steadiness was calculated as the coefficient of variation in torque over 6 s during submaximal tracking tasks (5%, 10%, 25%, 50%, and 75% maximal voluntary contraction). Achilles tendon elongation and cross-sectional area were recorded with ultrasound to calculate strain, stress, and stiffness. RESULTS: Maximal voluntary contraction and torque steadiness did not differ between persons with amputation (90.6 ± 31.6 N m, 3.7 ± 2.0%) and controls (95.8 ± 26.8 N m, 2.9 ± 1.2%; p > 0.05). Tendon stiffness (21.1 ± 18.2 N/mm) and strain (5.2 ± 1.3%) did not differ between groups (p > 0.05). Tendon cross-sectional area was 10% greater in persons with amputation leading to 29% lower stress (p = 0.021). Maximal voluntary contraction was a predictor of a lower coefficient of variation in torque (R2 = 0.11, p < 0.05). CONCLUSION: Persons with trauma-related transfemoral amputation do not differ in plantar flexion maximal voluntary contraction and torque steadiness of the intact leg compared with controls without amputation. Larger tendon cross-sectional area reduces stress and enables distribution of force across a greater area.

Examining gender diversity growth as a model for inclusion of all underrepresented persons in medical physics.

The labor force of Medical Physics is one of the most gender diverse in the field of Physics, as it has attained the proportional achievement of ~30% women worldwide (Tsapaki et al. Phys Medica. 2018;55:33-39). While great strides have been made toward a gender diverse workforce, women still comprise an underrepresented group. Many strategies have been suggested to increase the participation of underrepresented persons by addressing unconscious biases, increasing opportunities, dedicated hiring policies, and providing support networks in science and medicine (Barabino et al. Sci Eng Ethics. 2019; Coe et al. Lancet. 2019), yet the personnel landscape remains largely uniform. Herein, the conditions, strategies, and approaches that facilitated gender diversity in Medical Physics are considered as a means to further the inclusion of other underrepresented groups through exemplars of mentorship, addressing unconscious biases and the implementation of inclusive practices. Furthermore, the potential for gender diversity to act as a catalyst to create an environment that is more accepting of diversity and supports and encourages inclusive practices for the participation and inclusion of other underrepresented groups in Medical Physics is discussed.

Greater fatigue resistance of dorsiflexor muscles in people with prediabetes than type 2 diabetes.

Although exercise can prevent progression to T2D among people with prediabetes, little is known about fatigue during exercise in people with prediabetes compared to T2D. The purpose of the study was to compare the magnitude and mechanisms of fatigability of the ankle dorsiflexor muscles between people with prediabetes and T2D. Ten people with prediabetes (6 females, 51.7 ± 6.9 years) and fourteen with T2D (6 females, 52.6 ± 6.2 years) who were matched for age, body mass index and physical activity performed an intermittent (6 s contraction: 4 s relaxation) fatiguing task at 75% maximal voluntary contraction (MVC) with the dorsiflexors. Electrical stimulation was used to assess contractile properties of the dorsiflexor muscles before and after the fatiguing task. People with prediabetes had a longer time-to-task failure, i.e. greater fatigue resistance (7.9 ± 5.1 vs. 4.9 ± 2.5 min, P = 0.04), and slower rate of decline of the (potentiated) twitch amplitude (6.5 ± 3.1 vs. 16.5 ± 11.7%·min-1, P = 0.03) than people with T2D. Shorter time-to-task failure (i.e. greater fatigability) was associated with greater baseline MVC torque (r2 = 0.21, P = 0.02) and faster rate of decline of twitch amplitude (r2 = 0.39, P = 0.04). The ankle dorsiflexor muscles of males and females with prediabetes were more fatigue resistant than people with T2D, and fatigability was associated with contractile mechanisms.

Importance of Maximal Strength and Muscle-Tendon Mechanics for Improving Force Steadiness in Persons with Parkinson's Disease.

Although plantar flexion force steadiness (FS) is reduced in persons with Parkinson's disease (PD), the underlying causes are unknown. The aim of this exploratory design study was to ascertain the influence of maximal voluntary contraction (MVC) force and gastrocnemius-Achilles muscle-tendon unit behaviour on FS in persons with PD. Nine persons with PD and nine age- and sex-matched non-PD controls (~70 years, 6 females per group) performed plantar flexion MVCs and sub-maximal tracking tasks at 5, 10, 25, 50 and 75% MVC. Achilles tendon elongation and medial gastrocnemius fascicle lengths were recorded via ultrasound during contraction. FS was quantified using the coefficient of variation (CV) of force. Contributions of MVC and tendon mechanics to FS were determined using multiple regression analyses. Persons with PD were 35% weaker during MVC (p = 0.04) and had 97% greater CV (p = 0.01) with 47% less fascicle shortening (p = 0.004) and 38% less tendon elongation (p = 0.002) than controls. Reduced strength was a direct contributor to lower FS in PD (ß = 0.631), and an indirect factor through limiting optimal muscle-tendon unit interaction. Interestingly, our findings indicate an uncoupling between fascicle shortening and tendon elongation in persons with PD. To better understand limitations in FS and muscle-tendon unit behavior, it is imperative to identify the origins of MVC decrements in persons with PD.

Motor unit contributions to activation reduction and torque steadiness following active lengthening: a study of residual torque enhancement.

Following active lengthening, steady-state isometric (ISO) torque is greater than a purely ISO contraction at the same muscle length, this is referred to as residual torque enhancement (rTE). A phenomenon of rTE is activation reduction, characterized by reduced electromyography (EMG) amplitude for a given torque output. We hypothesized that lower motor unit discharge rates would contribute to activation reduction and lessening torque steadiness. Ten young male subjects performed ISO dorsiflexion contractions at 10 and 20% of maximal voluntary contraction (MVC) torque. During rTE trials, the muscle was activated at 10° of plantar flexion, then the ankle was rotated to the ISO position at 40°. Fine wire electrodes recorded motor unit (MU)-discharge rates and variability from the tibialis anterior. Surface EMG quantified activation reduction, and steadiness was determined as the coefficient of variation of torque. The activation reduction was 44 and 24% at 10 and 20% MVC, respectively (P < 0.05). Fewer MUs were recorded in the rTE than ISO condition at 10% (~47%) and 20% (~36%) MVC (P < 0.05). Discharge rates were 19 and 26% lower in the rTE compared with the ISO condition for 10 and 20% MVC, respectively (P < 0.05), with no difference in variability between conditions (P > 0.05). Steadiness was ~22 and 18% lower for the rTE than ISO condition at 10 and 20% MVC (P < 0.05). Our findings indicate that activation reduction may be attributed to lower MU discharge rate and fewer detectable MUs and that this theoretically contributes to a reduction in steadiness in the rTE condition.NEW & NOTEWORTHY Our findings indicate that lower electromyographic activity during the torque enhanced condition following active lengthening compared with a purely isometric contraction arises from fewer active motor units and a lower discharge rate of those that are active. We used an acute condition of increased torque capacity to induce a decrease in net output of the motor neuron pool during a submaximal task to demonstrate, in humans, the impact of motor unit activity on torque steadiness.

On the horizon of aging and physical activity research.

This viewpoint is the result of a Horizon Round Table discussion of Exercise and Aging held during the 2017 Saltin International Graduate School in Exercise and Clinical Physiology in Gatineau, Quebec. This expert panel discussed key issues and approaches to future research into aging, across human physiological systems, current societal concerns, and funding approaches. Over the 60-min round table discussion, 3 major themes emerged that the panel considered to be "On the Horizon" of aging research. These themes include (i) aging is a process that extends from womb to tomb; (ii) the importance of longitudinal experimental studies; and (iii) the ongoing need to investigate multiple systems using an integrative approach between scientists, clinicians, and knowledge brokers. With a focus on these themes, we aim to identify critical questions, challenges, and opportunities that face scientists in advancing the understanding of exercise and aging.