Impaired Performance Research Articles

Impaired performance of rapid grip in people with Parkinson's disease and motor segmentation

Bradykinesia, or slow movement, is a defining symptom of Parkinson's disease (PD), but the underlying neuromechanical deficits that lead to this slowness remain unclear. People with PD often have impaired rates of motor output accompanied by disruptions in neuromuscular excitation, causing abnormal, segmented, force-time curves. Previous investigations using single-joint models indicate that agonist electromyogram (EMG) silent periods cause motor segmentation. It is unknown whether motor segmentation is evident in more anatomically complex and ecologically important tasks, such as handgrip tasks. Aim 1 was to determine how handgrip rates of force change compare between people with PD and healthy young and older adults. Aim 2 was to determine whether motor segmentation is present in handgrip force and EMG measures in people with PD. Subjects performed rapid isometric handgrip pulses to 20–60% of their maximal voluntary contraction force while EMG was collected from the grip flexors and extensors. Dependent variables included the time to 90% peak force, the peak rate of force development, the duration above 90% of peak force, the number of segments in the force-time curve, the number of EMG bursts, time to relaxation from 90% of peak force, and the peak rate of force relaxation. People with PD had longer durations and lower rates of force change than young and older adults. Six of 22 people with PD had motor segmentation. People with PD had more EMG bursts compared to healthy adults and the number of EMG bursts covaried with the number of segments. Thus, control of rapid movement in Parkinson's disease can be studied using isometric handgrip. People with PD have impaired rate control compared to healthy adults and motor segmentation can be studied in handgrip.

Load-Velocity Profiles Before and After Heated Resistance Exercise.

Sweet, DK, Qiao, J, Rosbrook, P, and Pryor, JL. Load-velocity profiles before and after heated resistance exercise. J Strength Cond Res 38(6): 1019-1024, 2024-This study examined neuromuscular performance using load-velocity (L-V) profiles in men and women before and after resistance exercise (RE) in hot (HOT; 40° C) and temperate (TEMP; 21° C) environments. Sixteen (f = 8, m = 8) resistance-trained individuals completed a single 70-minute whole-body high-volume load (6 exercises, 4 sets of 10 repetitions) RE bout in HOT and TEMP. Before and after RE, rectal temperature (TRE), muscle temperature of the vastus lateralis (TVL) and triceps brachii (TTB), and an L-V profile for the deadlift and bench press were recorded. Thermoregulatory and L-V data were analyzed using separate 2-way repeated measures analysis of variances (ANOVAs; condition [hot, temperate] and time [pre, post]) with significance level set at p ≤ 0.05. Deadlift peak velocity was reduced at 60% 1 repetition maximum (1RM) after RE in HOT but not TEMP. Peak velocity of 40% 1RM bench press was lower in TEMP vs. HOT pre-RE (p < 0.01). Peak velocity was decreased at all loads in the deadlift L-V profile after RE, regardless of condition. Despite elevated TRE (TEMP; 37.58 ± 0.35, HOT; 38.20 ± 0.39° C), TVL (TEMP; 35.24 ± 0.62, HOT; 37.92 ± 0.55° C), and TTB (TEMP; 35.05 ± 0.78, HOT; 38.00 ± 0.16° C) after RE in HOT vs. TEMP (p < 0.01), RE in HOT did not broadly affect L-V profiles. This indicates heated resistance exercise can be performed with high-volume load and high ambient temperature with minimal performance impairment.

Endothelin-1 impairs skeletal muscle myogenesis and development via ETB receptors and p38 MAPK signaling pathway.

Myopenia is a condition marked by progressive decline of muscle mass and strength and is associated with aging or obesity. It poses the risk of falling, with potential bone fractures, thereby also increasing the burden on family and society. Skeletal muscle wasting is characterized by a reduced number of myoblasts, impaired muscle regeneration and increased muscle atrophy markers (Atrogin-1, MuRF-1). Endotheline-1 (ET-1) is a potent vasoconstrictor peptide. Increased circulating levels of ET-1 is noted with aging and is associated with muscular fibrosis and decline of strength. However, the regulatory mechanism controlling its effect on myogenesis and atrophy remains unknown. In the present study, the effects of ET-1 on myoblast proliferation, differentiation and development were investigated in C2C12 cells and in ET-1-infused mice. The results show that ET-1, acting via ETB receptors, reduced insulin-stimulated cell proliferation, and also reduced MyoD, MyoG and MyHC expression in the differentiation processes of C2C12 myoblasts. ET-1 inhibited myoblast differentiation through ETB receptors and the p38 mitogen-activated protein kinase (MAPK)-dependent pathway. Additionally, ET-1 decreased MyHC expression in differentiated myotubes. Inhibition of proteasome activity by MG132 ameliorated the ET-1-stimulated protein degradation in differentiated C2C12 myotubes. Furthermore, chronic ET-1 infusion caused skeletal muscle atrophy and impaired exercise performance in mice. In conclusion, ET-1 inhibits insulin-induced cell proliferation, impairs myogenesis and induces muscle atrophy via ETB receptors and the p38 MAPK-dependent pathway.

Symposium review: high altitude travel with pulmonary vascular disease.

Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are the main precapillary forms of pulmonary hypertension (PH) summarized as pulmonary vascular diseases (PVD). PVDs are characterized by exertional dyspnoea and oxygen desaturation, and reduced quality of life and survival. Medical therapies improve life expectancy and physical performance of PVD patients, of whom many wish to participate in professional work and recreational activities including traveling to high altitude. The exposure to the hypobaric hypoxic environment of mountain regions incurs the risk of high altitude adverse events (AEHA) due to severe hypoxaemia exacerbating symptoms and further increase in pulmonary artery pressure, which may lead to right heart decompensation. Recent prospective and randomized trials show that altitude-induced hypoxaemia, pulmonary haemodynamic changes and impairment of exercise performance in PVD patients are in the range found in healthy people. The vast majority of optimally treated stable PVD patients who do not require long-term oxygen therapy at low altitude can tolerate short-term exposure to moderate altitudes up to 2500m. PVD patients that reveal persistent severe resting hypoxaemia ( <80% for >30min) at 2500m respond well to supplemental oxygen therapy. Although there are no accurate predictors for AEHA, PVD patients with unfavourable risk profiles at low altitude, such as higher WHO functional class, lower exercise capacity with more pronounced exercise-induced desaturation and more severely impaired haemodynamics, are at increased risk of AEHA. Therefore, doctors with experience in PVD and high-altitude medicine should counsel PVD patients before any high-altitude sojourn. This review aims to summarize recent literature and clinical recommendations about PVD patients travelling to high altitude.

Reduced sensitivity to future consequences underlies gambling decision in cerebellar ataxia

IntroductionPrevious research has identified that people with cerebellar ataxia (CA) showed impaired reward-related decision-making in the Iowa Gambling Task (IGT). To investigate the mechanisms underlying this impairment, we examined CA participants' combination of performance in the IGT, which predominantly tests reward seeking, and the modified IGT (mIGT), which mainly assesses punishment avoidance. MethodsFifty participants with CA and one hundred controls completed the IGT and mIGT. Task performance in each of the five twenty-trial blocks was compared between groups and the learning rates were assessed with simple linear regressions. Each participant's IGT score and mIGT score were compared. ResultsCA participants performed worse than controls in both the IGT and the mIGT, especially in the last block (IGT: −0.24 ± 10.05 vs. 3.88 ± 10.31, p = 0.041; mIGT: 2.72 ± 7.62 vs. 8.65 ± 8.64, p < 0.001). In contrast to the controls, those with CA did not significantly improve their scores over time in either task. Controls performed better in the mIGT than the IGT, while CA participants' scores in the two tasks showed no significant difference. IGT and mIGT performance did not correlate with ataxia severity or depressive symptoms. ConclusionIndividuals with CA showed impaired performance in both the IGT and mIGT, which indicates disruption in both short-term reward seeking and short-term punishment avoidance. Therefore, these results suggest that reduced sensitivity to long-term consequences drives the risky decision-making in CA.

Assessing exposure to airborne fungi and bacteria in the horse-riders environment: A pilot study

Among airborne biological contaminants, several pathogenic and/or allergenic fungi and bacteria can affect the health of horses and humans. Exposure to primary biological aerosol particles (PBAP) in the equine environment remains poorly understood, although environmental factors play a major role in the development of respiratory diseases and impaired performance in horses. This pilot study was conducted during a training course for young racers. Ambient and personal air samples provided original data on the microbial composition of PBAP in the riders’ immediate environment (stable, outdoor, riding arena), using culture-based and metagenomic approaches. The culture-based approach showed average levels of fungi and bacteria of 2.3 × 104 and 8.3 × 105 CFU/m3 respectively during training. Seventy-one and 50 fungal and bacterial species were respectively identified, while the metagenomic approach identified 211 and 285, respectively. It should be noted, however, that two-thirds of the bacterial and fungal genera were found by both approaches. Among these species, various pathogenic and/or allergenic fungi (Alternaria spp., Aspergillus spp., Cladosporium spp. and Lichtheimia ramosa) and bacteria (Aeromonas spp., Bacillus spp., Pseudomonas spp. and Staphylococcus spp.) were highlighted. This study underlines the value of the combined use of culture-based and metagenomic approaches to provide an overview of the distribution of different fungal and bacterial phyla, genera and species in the equine environment. Statistical analysis also suggests interactions between microbiological contaminants (bacteria and mold) and climatic parameters (rain, wind, temperature).

A Simple Tube Escape Assay to Test Learning and Memory in Zebrafish with Minimized Habituation.

Various methods have been used in rodents to evaluate learning and memory. Although much less frequently used, the zebrafish emerges as an alternative model organism in this context. For example, it allows assessing potential behavioral deficits because of neurodevelopmental disorders or environmental neurotoxins. A variety of learning tasks have been employed in previous studies that required extensive habituation and training sessions. Here, we introduce a simpler and faster method to evaluate learning and memory of zebrafish with minimum habituation. A new apparatus, a transparent L-shaped tube, was developed in which we trained each zebrafish to swim through a long arm and measured the time to swim through this arm. We demonstrate that in this task, zebrafish could acquire both short-term (1 h) and long-term memory (4 days). We also studied learning and memory of a gene knockout (KO) zebrafish that showed social impairments related to autism. We found KO mutant zebrafish to show a quantitative impairment in habituation, learning, and memory performance compared with wild-type control fish. In conclusion, we established a novel learning apparatus and sensitive paradigm that allowed us to evaluate learning and memory of adult zebrafish that required only a brief habituation period and minimal training.

Effects of preparticipating hypohydration oncardiac burden in recreational athletes.

The global temperature rise will have extensive consequences on our organ systems, but hypohydration caused by reduced water intake or increased water loss through sweating plays the most relevant role. Many studies have already demonstrated the association between hypohydration and impaired exercise performance, but data related to the cardiac burden of hypohydration are scarce. This study is a sub-investigation of our large, prospective, self-controlled trial on the effects of hypohydration on cardiopulmonary exercise capacity with previously published results. In the current sub-study, we analyzed the impact of hypohydration on cardiac burden in this cohort of fifty healthy, recreational athletes during cardiopulmonary exercise test.Therefore, each participant underwent cardiopulmonary exercise test with a standardized ramp protocol twice, once in hypohydrated state and once in euhydrated state as control, and the cardiac markers Troponin T, NT-pro-BNP and Chromogranin A were measured before and after the exercise test at each state. Mean age was 29.7 years and 34% of probands were female. Hypohydration led to a reduced body water, a significant decrease in oxygen uptake and lower levels of power output. Yet, Troponin T, NT-proBNP, Chromogranin A and lactate levels did not significantly differ between the two conditions.In this study cohort, decreased exercise capacity during hypohydration was more likely due to impaired cardiac output with diminished plasma volume rather than measurable cardiac stress from fluid deprivation. However, whether these data are generalizable to a diseased cohort is left unanswered and should be addressed in future randomized controlled trials.

Unveiling the Shadow: Theorizing the Impact of Narcissistic Leadership on Sales Teams

This study investigates the dual nature of narcissistic leadership within sales teams, revealing its potential to both inspire ambitious goals and undermine team cohesion and performance. By integrating a comprehensive literature review, the research outlines the characteristic behaviors of narcissistic leaders, such as arrogance and a lack of empathy, and their impact on team dynamics, including reduced cohesion, increased conflict, and impaired team performance. The paper proposes strategies to mitigate these negative effects, such as leadership development programs, team-based performance evaluations, and fostering a culture of empathy. It highlights the importance of understanding and addressing the complexities of narcissistic leadership to cultivate healthier, more productive team environments. The findings call for further research into the long-term effects of narcissistic leadership and the development of effective management strategies.

Cigarette smoking and cognitive task performance: Experimental effects of very-low nicotine-content cigarettes.

Reductions in the nicotine content of cigarettes decrease smoking rate and dependence severity, but effects on cognition are less well established. The potential impacts of very-low nicotine-content (VLNC) cigarettes on cognitive task performance must be evaluated, especially in vulnerable populations. The aim of the present study is to experimentally examine the effects of VLNC cigarettes on cognitive performance. Adults who smoked daily (n = 775) from three vulnerable populations (socioeconomically disadvantaged reproductive-age women, individuals with opioid use disorder, affective disorders) were examined. Participants were randomly assigned to normal nicotine content (NNC; 15.8 mg nicotine/g tobacco) or VLNC (2.4 mg/g or 0.4 mg/g) cigarettes for 12 weeks. Response inhibition (stop-signal task), working memory (n-back task; n of 2-n of 0), and cognitive interference (nicotine Stroop task) were assessed at baseline, 2, 6, and 12 weeks. Results were analyzed using mixed-model repeated-measures analyses of variance. Extended exposure to VLNC cigarettes produced no significant changes in any measure of cognitive performance compared to NNC cigarettes. Over weeks, response times on the n-back task decreased across doses. No significant effects were observed on the stop-signal or nicotine Stroop tasks. All three vulnerable populations performed comparably on all three cognitive tasks. Extended exposure to VLNC cigarettes produced no impairments in cognitive performance on any of the assessed tasks compared to NNC cigarettes. These findings are consistent with the larger literature detailing other consequences following exposure to VLNC cigarettes and are encouraging for the adoption of a nicotine-reduction policy. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Alzheimer-like behavior and synaptic dysfunction in 3 × Tg-AD mice are reversed with calcineurin inhibition.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by impairments in synaptic plasticity and cognitive performance. Current treatments are unable to achieve satisfactory therapeutic effects or reverse the progression of the disease. Calcineurin has been implicated as part of a critical signaling pathway for learning and memory, and neuronal calcineurin may be hyperactivated in AD. To investigate the effects and underlying mechanisms of FK506, a calcineurin inhibitor, on Alzheimer-like behavior and synaptic dysfunction in the 3 × Tg-AD transgenic mouse model of Alzheimer's disease, we investigated the effect of FK506 on cognitive function and synaptic plasticity in the 3 × Tg-AD transgenic mouse model of Alzheimer's disease. The results showed that FK506 treatment ameliorated cognitive deficits, as indicated by the decreased latency in the water maze, and attenuated tau hyperphosphorylation in 3 × Tg-AD mice. Treatment with FK506 also reduced the levels of certain markers of postsynaptic deficits, including PSD-95 and NR2B, and reversed the long-term potentiation deficiency and dendritic spine impairments in 3 × Tg-AD mice. These findings suggest that treatment with calcineurin inhibitors such as FK506 can be an effective therapeutic strategy to rescue synaptic deficit and cognitive impairment in familial Alzheimer's disease and related tauopathies.

Excessive left anterior hippocampal and caudate activation in schizophrenia underlie cognitive underperformance in a virtual navigation task

We used a virtual navigation paradigm in a city environment to assess neuroanatomical correlates of cognitive deficits in schizophrenia spectrum disorders (SSD). We studied a total of N = 36 subjects: 18 with SSD and 18 matched unaffected controls. Participants completed 10 rapid, single-trial navigation tasks within the virtual city while undergoing functional magnetic resonance imaging (fMRI). All trials tested ability to find different targets seen earlier, during the passive viewing of a path around different city blocks. SSD patients had difficulty finding previously-encountered targets, were less likely to find novel shortcuts to targets, and more likely to attempt retracing of the path observed during passive viewing. Based on a priori region-of-interest analyses, SSD participants had hyperactivation of the left hippocampus when passively viewing turns, hyperactivation of the left caudate when finding targets, and hypoactivation of a focal area of the dorsolateral prefrontal cortex when targets were initially shown during passive viewing. We propose that these brain-behaviour relations may bias or reinforce stimulus-response navigation approaches in SSD and underlie impaired performance when allocentric spatial memory is required, such as when forming efficient shortcuts. This pattern may extend to more general cognitive impairments in SSD that could be used to design remediation strategies.

PSII-7 Effect of endophyte-infected tall fescue on body weight, vital signs, and liver function of beef heifers

Abstract Tall fescue was first introduced to the United States over 70 years ago. Since then, it has become the most common forage source for beef cattle in the Southeastern region of the US. Most tall fescue establishes a symbiotic relationship with a toxic fungal endophyte (Epichloë coenophiala), which contributes to the improved vigor of the plant due to acquired resistance to grazing, insects, heat, and drought. However, when consumed by cattle, it may cause fescue toxicosis, a condition characterized by reduced feed intake, body weight (BW) loss, vasoconstriction, and impaired reproductive performance in livestock species. Therefore, the aim of this study was to investigate the effect of endophyte-infected tall fescue consumption on growth performance and health-related traits in beef cattle. For this purpose, 24 Simmental x Angus heifers were divided into two dietary treatments, in which 12 heifers received endophyte-free tall fescue seeds (E-) and 12 heifers were fed with endophyte-infected tall fescue seeds (E+, 6,764 ppb of ergovaline) mixed with the diet for 45 d. The E+ heifers received a daily dose of 20 μg of ergovaline per kg of BW. The E- heifers received the same quantity of seeds as the E+ heifers. For each heifer, phenotypes related to growth (BW), vital signs (respiration rate [RR], and body temperature [TEMP]), and liver functions (serum albumin [ALB], alkaline phosphatase [ALP], aspartate aminotransferase [AST], gamma-glutamyltransferase [GGT], cholesterol [COL], bilirubin [BIL], and triglycerides [TRI]) were analyzed at the end of the experiment. Phenotypes were analyzed using a linear model in R with diet included as a fixed effect. For analysis of BW, the BW at the beginning of the trial was included in the model as a covariate. Results showed that COL and ALP were significantly less (P &amp;lt; 0.05) in the E+ heifers compared with the E- (-32.92 ± 11.16 mg/dL and -32.33 ± 13.95 U/L, respectively). Conversely, E+ heifers had greater (P &amp;lt; 0.05) BW, RR, TEMP, and AST when compared with E- heifers (-17.82 ± 5.12 kg, 25.83 ± 5.52 breaths/min, 0.56 ± 0.12 oC, and 5.83 ± 2.18 U/L, respectively). Measurements of ALB, BIL, GGT, and TRI were not different between E+ and E- heifers. Our results suggest that heifers consuming endophyte-infected tall fescue have compromised vital signs and metabolically altered liver, which may impair growth performance. This study increases our understanding of the biological mechanisms affected by the fescue toxin in beef cattle.

Trainability of affordance judgments in right and left hemisphere stroke patients.

Whenever we are confronted with action opportunities in everyday life, e.g., when passing an opening, we rely on our ability to precisely estimate our own bodily capabilities in relation to the environmental conditions. So-called affordance judgments can be affected after brain damage. Previous studies with healthy adults showed that such judgments appeared to be trainable within one session. In the current study, we examined whether stroke patients with either right brain damage (n = 30) or left brain damage (n = 30) may similarly profit from training in an aperture task. Further, the role of neuropsychological deficits in trainability was investigated. In the administered task, stroke patients decided whether their hand would fit into a presented opening with varying horizontal width (Aperture Task). During one training session, patients were asked to try to fit their hand into the opening and received feedback on their decisions. We analyzed accuracy and the detection theory parameters perceptual sensitivity and judgment tendency. Both patients with right brain damage and patients with left brain damage showed improved performance during training as well as post training. High variability with differential profiles of trainability was revealed in these patients. Patients with impaired performance in a visuo-spatial or motor-cognitive task appeared to profit considerably from the target-driven action phase with feedback, but the performance increase in judgments did not last when the action was withdrawn. Future studies applying lesion analysis with a larger sample may shed further light on the dissociation in the trainability of affordance judgments observed in patients with versus without visuo-spatial or motor-cognitive deficits.

Myofiber “Lipotoxicity” Does Not Disrupt Cellular Biophysical Properties

Obesity is associated with pathological changes in skeletal muscle that contribute to functional loss and disability. While it is unclear which specific factors cause this impairment in muscle performance, intramyocellular lipid (IMCL) within the muscle fibers, termed “lipotoxicity”, is implicated. Some studies have suggested the mechanism for this association is mitochondrial dysfunction, whereas others propose the increase in IMCL leads to structural changes within the muscle fibers. The objective of this study was to determine whether IMCL, independent of obesity, impacted active force generation and passive viscoelasticity of the myofiber sarcomere lattice. This study utilized soleus muscles from wildtype (WT) and lipodystrophic (LD) mice and calf muscle biopsies from individuals with (DPN) and without (CTL) type 2 diabetes over a range of obesity status to isolate the effects of IMCL from the effects of obesity in general. IMCL was quantified for each fiber type by co-registration of Oil Red O (ORO) stained cryosections or fluorescent BODIPY stained section and myosin heavy chain isoform stained sections. BODIPY stained sections were used with confocal microscopy to quantify individual lipid droplet metrics (average area, total number). Individual muscle fibers were isolated from soleus muscles and calf muscle biopsies and chemically permeabilized to isolate the myofibrillar lattice and were tested in a specialized system (1400A; Aurora Scientific). Active and passive forces were recorded, fit with a 3-element model, and correlated with metrics of IMCL accumulation by fiber type. LD muscle had 2-3 fold higher IMCL accumulation (p&lt;0.05) in type 2a and 2x fibers than WT quantified by ORO and BODIPY. This was due to an increase in both lipid droplet area and number. DPN muscle had ~2 fold higher IMCL accumulation (p&lt;0.05) in type 2 fibers compared with CTL. Both type 1 and type 2 fibers had significantly increased area of lipid droplets, but only in type 2 fibers was there an increase in lipid droplet number and consequently in area fraction. Despite the large accumulation of IMCL, LD permeabilized muscle fibers had no deficit in active force generation and no change in any of the 5 measures of passive viscoelasticity compared with WT. Conversely, in humans, DPN type 2 fibers had significantly lower (-18%) active force generation and both type 1 and type 2 DPN fibers had elevated resting viscosity (+5%) compared with CTL. Across human samples, active force generation was significantly correlated with average lipid droplet area (r2=0.53, p=0.04), but no other correlations were significant. This study suggests that an increase in IMCL accumulation in and of itself does not physically disrupt sarcomere contraction. Dramatic accumulation of IMCL in LD mouse fibers did not impact active or passive forces, likely due to an absence of systemic complications (obesity, advanced diabetes). Human fibers of comparable IMCL accumulation have a deficit in active force generation correlated with IMCL parameters, but we conclude this relationship is more likely correlative than causative as type 1 fibers with similar lipid droplet areas have no association between lipid droplet area and active force generation. These data suggest that while accumulation of IMCL is associated with contractile disfunction across a number of conditions, the mechanism is likely either indirect or biochemical rather than biophysical. Shriners Hospitals for Children, P30 AR074992, AR075773, AG15768, AG46927, AR072999, AR073752. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The effect of high intensity interval training on muscle contractile function 8 weeks following chemically-induced ovarian failure

The negative effects of ovariectomy on muscle contractile function have been well-characterized, however, the effects of gradual ovarian failure (i.e., perimenopausal transition into late-stage menopause) on muscle function over the lifespan have received less attention. Furthermore, whether exercise training can mitigate changes in muscle contractile function associated with menopause is unclear. The objective of this study, using a chemically-induced ovarian failure mouse model (4-vinylcyclohexene diepoxide; VCD), was to investigate time-course changes in muscle contractility of sedentary controls and the potential of high intensity interval training to mitigate any deleterious effects of ovarian failure. Starting at 11wks old, mice were injected with 160mg/kg/day of VCD for 15 days. Twenty-eight (VCD-trained: n=10, VCD-sedentary: n=10, control: n=8) CD1 female mice were used in this study, with the VCD-trained group beginning training at the onset of ovarian failure for a total of 8 weeks. Contractile properties of the plantar flexors were assessed using an in-vivo set-up 8 weeks following the onset of ovarian failure. As well, a fatigue task (repeated maximal isometric contractions until torque decreased by 60%) was performed. Recovery was measured immediately after, and up to 10min following task termination. Upon completion of mechanical testing, mice were sacrificed and intact muscle fibres were isolated from the flexor digitorum brevis, and myoplasmic free Ca2+ (tetanic [Ca2+]i) concentrations were measured across stimulation frequencies of 10-200 Hz and throughout 50 tetanic contractions (70Hz) to replicate our fatigue task. There was no difference in pre-fatigue values across groups for peak twitch torque, peak 100Hz torque, RTD, 10:100Hz torque, tetanic [Ca2+]i during low (10Hz) and high Hz (100Hz) stimulation, and all were reduced similarly immediately following the fatigue task. Repetitions to task failure was similar across groups and tetanic [Ca2+]i during repetitive contractions (n=50) was reduced similarly across groups. As well, all groups recovered similarly across these measures. Torque and RTD did not recover fully by 10min for either measure, while 10Hz, 100Hz and 10:100Hz tetanic [Ca2+]i was recovered immediately following the fatigue task. Given 10Hz torque was relatively maintained following the fatigue task, and there was a ~40% decline in 100Hz torque, the 10:100Hz ratio increased throughout recovery — this, combined with the [Ca2+] data indicate that calcium sensitivity and release are unlikely contributors to impaired force production following the fatigue task across groups. The present study aimed to assess the impact of training on muscle contractility using a mouse model of gradual ovarian failure. Unlike other models of ovarian failure, there does not seem to be any impairment in muscular performance at the joint level in our VCD-mice, and they responded similarly across groups in response to repetitive fatiguing contractions and exercise training. Supported by NSERC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Qualitative Study of Work-Related Musculoskeletal Disorders Among Midwives in Selected Hospitals in Ho Municipality, Ghana

Objectiveand rationale: The study sought to explore the experiences of midwives at selected hospitals in the Ho municipality regarding work-related musculoskeletal disorders, the predisposing factors, the impacts on them, and their coping strategies to mitigate the effects of work-related musculoskeletal disorders. MethodsThis study adopted a qualitative research approach with a phenomenological study design. Purposive sampling was employed in this study to select participants. Data was collected and recorded on voice recording devices from fifteen (15) midwives through an interview using a semi-structured interview guide. Data was manually transcribed and analyzed using thematic content analysis. ResultsThe four emerging themes include: the lived experiences of midwives regarding musculoskeletal disorders, predisposing factors contributing to musculoskeletal disorders, impact of musculoskeletal disorders, and coping strategies of midwives. These themes were further expanded by their sub-themes in describing musculoskeletal conditions, onset, understaffing of midwives, awkward posture assumption during care delivery, limited logistics, struggle with quality of life, impaired work performance, rest and good body mechanics, and teamwork. ConclusionTo lower the rate of work-related musculoskeletal disorders among midwives and increase work efficiency and productivity, educational programs on prevention and coping mechanisms for musculoskeletal disorders should be made mandatory for midwives.

Mesenchymal stem cells improve cardiac function in diabetic rats by reducing cardiac injury biomarkers and downregulating JAK/STAT/iNOS and iNOS/Apoptosis signaling pathways

Cardiovascular complications are prevalent manifestations of type 2 diabetes mellitus (T2DM) and are usually the main cause of death. This study aims to show the underlying mechanisms of the potential therapeutic effect of mesenchymal stem cells (MSCs) on diabetic cardiac dysfunction. Twenty-four male Wistar rats were randomly assigned to one of three groups The control group received standard laboratory chow, and the groups with T2DM received a single dose of 45 mg/kg body weight of streptozotocin (STZ) after 3 weeks of pretreatment with a high-fat diet (HFD). Eight weeks after the diagnosis of T2DM, rats were divided into two groups: the T2DM model group and the T2DM+MSCs group. BM-MSCs were administered systemically at 2 × 106 cells/rat doses.A Significant amelioration in Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and dyslipidemia was noted 2 weeks post-administration of MSCs. Administration of MSCs improved dyslipidemia, the altered cardiac injury biomarkers (p≤0.0001), downregulated Janus kinase 2/signal transducer and activator of transcription 3(JAK2/STAT3) / inducible Nitric oxide synthase (iNOS) and iNOS/ Apoptosis signaling pathways. This was associated with improved cardiac dysfunction (impaired left ventricular performance and decreased contractility index).Our results show that MSCs ameliorate cardiac dysfunction associated with diabetic cardiomyopathy by lowering dyslipidemia and insulin resistance, inhibiting oxidative stress, and inflammation, downregulating JAK2/STAT3/ iNOS and iNOS/Apoptosis signaling pathways,

Inflammation and weight change related to neurocognitive and functional impairment in diabetes and psychiatric disorders

Introduction: Obesity is a global pandemic associated with various cardio-metabolic and psychiatric disorders. Neurocognitive and functional deficits have been associated with several somatic and psychiatric disorders. Adiposity-related inflammation has recently emerged as a key risk factor for neurocognitive and functional impairments. This prospective transdiagnostic study aimed to investigate the role of adiposity-related inflammatory markers in neurocognitive and functional outcomes associated with weight changes.Methods: Peripheral blood inflammatory and oxidative stress biomarkers and neurocognitive and functional performance were assessed twice over 1 year in 165 individuals, including 30 with schizophrenia, 42 with bipolar disorder, 35 with major depressive disorder, 30 with type 2 diabetes mellitus (T2DM), and 28 healthy controls. Participants were stratified by body mass index into categories of type 2 obesity (T2OB; n=30), type 1 obesity (T1OB; n=42), overweight (OW; n=53), and average weight (NW; n=40). Mixed one-way analysis of covariance and linear and binary logistic regression analyses were performed.Results: Compared with NW, T2OB and T1OB were significantly associated with impaired neurocognitive and functional performance (p<0.01; η²p=0.06–0.12) and higher levels of C-reactive protein and platelets (PLT) (p<0.01; η²p= 0.08–0.16), with small-to-moderate effect sizes. IL-6, IL-10, and PLT were key factors for detecting significant weight changes in T1OB and T2OB over time. Regression models revealed that inflammatory and oxidative stress biomarkers and cellular adhesion molecules were significantly associated with neurocognitive and functional performance (p<0.05).Discussion: Obesity is characterised by neurocognitive and functional impairments alongside low-grade systemic inflammation. Adiposity-related inflammatory biomarkers may contribute to neurocognitive and functional decline in individuals with T2DM and psychiatric disorders. Our data suggest that these biomarkers facilitate the identification of specific subgroups of individuals at higher risk of developing obesity.

Age-related blunting of serial sarcomerogenesis and mechanical adaptations following 4 weeks of maximal eccentric resistance training

During natural aging, muscles atrophy, which is partly accounted for by a loss of sarcomeres in series. Serial sarcomere number (SSN) is associated with aspects of muscle mechanical function including the force-length and force-velocity-power relationships; hence, the age-related loss of SSN contributes to declining performance. Training emphasizing muscle lengthening (eccentric) contractions increases SSN in young healthy rodents. However, the ability for eccentric training to increase SSN and improve mechanical function in old age is unknown. Older individuals often exhibit a blunted ability for training-induced hypertrophic adaptations. Therefore, the purpose of this study was to investigate the sarcomerogenic response to eccentric training in old rats. We hypothesized that old rats would experience a smaller magnitude of serial sarcomerogenesis than young rats, which would correspond to smaller beneficial adaptations in mechanical function as compared with young. Ten young (9 months) and 11 old (33 months) Fisher344/BN F1 rats completed 4 weeks of unilateral isokinetic eccentric plantar flexion training 3 days/week. Pre- and post-training, the plantar flexors were assessed for maximum tetanic torque (ankle angles of 70° and 90°), the torque-frequency relationship (stimulation frequencies of 1-100 Hz), the passive torque-angle relationship (ankle angles of 110-70°), and the torque-angular velocity-power relationship (isotonic loads of 10%-80% maximum). Following post-training testing, rats were sacrificed, and the soleus, lateral gastrocnemius (LG), and medial gastrocnemius (MG) were harvested for SSN assessment by measuring sarcomere lengths with laser diffraction, with the untrained leg used as a control. In the untrained leg/pre-training, old rats had lower SSN in the soleus (−9%), LG (−7%), and MG (−14%), lower maximum torque (−27 to −42%), power (−63%), and shortening velocity (−35%), and greater passive torque (+62 to +191%) than young. Young rats showed 6% increased SSN from the untrained to the trained soleus and MG. In contrast, old rats had no change in soleus SSN, only a 2% increase in MG SSN, and 4% SSN loss in the LG. Young rats saw modest improvements in isometric mechanical function, including a 13% increase in maximum torque at 90° and 4-11% increases in 10-60 Hz torque. Old rats, however, had reductions in maximum torque (−35%), shortening velocity (−46%), and power (−63%), and increased passive torque (+24 to +51%). Altogether, eccentric training induced serial sarcomerogenesis and improved mechanical function in young rats, while old rats exhibited dysfunctional remodelling that led to impaired muscle mechanical performance. Supported by NSERC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.