Walking with unilateral ankle-foot unloading: a comparative biomechanical analysis of three assistive devices.

BACKGROUND: Foot and ankle unloading is essential in various clinical contexts, including ulcers, tendon ruptures, and fractures. Choosing the right assistive device is crucial for functionality and recovery. Yet, research on the impact of devices beyond crutches, particularly ankle-foot orthoses (AFOs) designed to unload the ankle and foot, is limited. This study investigates the effects of three types of devices-forearm crutches, knee crutch, and AFO-on biomechanical, metabolic, and subjective parameters during walking with unilateral ankle-foot unloading. METHODS: Twenty healthy participants walked at a self-selected speed in four conditions: unassisted able-bodied gait, and using three unloading devices, namely forearm crutches, iWalk knee crutch, and ZeroG AFO. Comprehensive measurements, including motion capture, force plates, and metabolic system, were used to assess various spatiotemporal, kinematic, kinetic, and metabolic parameters. Additionally, participants provided subjective feedback through questionnaires. The conditions were compared using a within-subject crossover study design with repeated measures ANOVA. RESULTS: Significant differences were found between the three devices and able-bodied gait. Among the devices, ZeroG exhibited significantly faster walking speed and lower metabolic cost. For the weight-bearing leg, ZeroG exhibited the shortest stance phase, lowest braking forces, and hip and knee angles most similar to normal gait. However, ankle plantarflexion after push-off using ZeroG was most different from normal gait. IWalk and crutches caused significantly larger center-of-mass mediolateral and vertical fluctuations, respectively. Participants rated the ZeroG as the most stable, but more participants complained it caused excessive pressure and pain. Crutches were rated with the highest perceived exertion and lowest comfort, whereas no significant differences between ZeroG and iWalk were found for these parameters. CONCLUSIONS: Significant differences among the devices were identified across all measurements, aligning with previous studies for crutches and iWalk. ZeroG demonstrated favorable performance in most aspects, highlighting the potential of AFOs in enhancing gait rehabilitation when unloading is necessary. However, poor comfort and atypical sound-side ankle kinematics were evident with ZeroG. These findings can assist clinicians in making educated decisions about prescribing ankle-foot unloading devices and guide the design of improved devices that overcome the limitations of existing solutions.

Risk and protective factors for psychological distress during COVID-19 in Israel.

The purpose of the present study was to identify the protective and risk factors related to psychological distress during COVID-19 in an Israeli sample. An online survey was administered from April 19 to May 2, 2020, while a strict lockdown was in place. Participants were recruited by snowball sampling. Psychological distress was evaluated using the Generalized Anxiety Disorder questionnaire (GAD-7) and the Patient Health Questionnaire-9 (PHQ-9). Risk and protective factors for psychological distress were assessed on the Multi-dimensional Perceived Social Support (MSPSS), the coping strategies (COPE), the Life Orientation Test (LOT), and the Gratitude questionnaire. Out of the 655 valid questionnaires collected (from participants ranging in age from 18 to 86, 246 males, 409 females), 138 (21.3%) were positive for moderate to very severe depression and 87 (13.2%) for moderate to extremely severe anxiety. Participants who were screened for depression and anxiety were more likely to be women and young adults (18-24). After adjusting statistically for gender, age, and socioeconomic status, depression and anxiety remained significantly associated with both emotion-focused (PHQ-ß =.437, p < .001, GAD-ß=.441, p < .001) and problem-focused (PHQ-ß =-.219, p < .001, GAD-ß=-.143, p < .001) coping strategies, as well as on the social support (PHQ-ß =-.167, p < .001, GAD-ß=-.155, p < .001), life orientation (GAD-ß=-.09, p < .001), and gratitude scales (PHQ-ß =-.07, p < .001). Levels of anxiety and depression were generally associated with gender (women), age (younger population), socioeconomic status (low), and an emotion-focused strategy as risk factors. A problem-focused strategy, social support, life orientation, and gratitude served as protective factors above and beyond personal background.

The effects of a multi-day cross-country mountain bike race on myocardial function, stress, inflammation and cardiac biomarkers in amateur master athletes.

This study aimed to examine the effects of a multi-day mountain bike race on amateur master athlete cyclists (AMA). AMA (50±5 years) completed 2 stages of a mountain bike race. Six weeks before racing, echocardiography, blood and maximal cardiopulmonary exercise tests (CPET) were performed. One hour after completion of each race stage, echocardiography measurements were taken and blood was sampled for stress, inflammatory and cardiac biomarkers. Main outcomes of the CPET were maximal oxygen consumption (VO2max) 50.7±6.5 ml/kg/min; maximal power 328±45 Watt and ventilatory threshold of 86%VO2max. Participants completed 95.7km with an elevation of 1650m on the first day, and 92.5km with an elevation of 1410m on the second day, with completion times of 357±42 and 390 ±43 minutes, respectively. After racing, increases in Creatine Phosphokinase and C-reactive protein (3-6 fold) (p<0.001), Troponin I (4-fold) (p<0.001) and N-terminal pro-brain natriuretic peptide (NT-Pro BNP) (4-7-fold) (p<0.001) were noted, with a reduction in the myocardial global work index of 17-24% (p<0.001). No correlations were found between Troponin I or NT-Pro BNP and myocardial global work index. Highly aerobically fit AMA participating in demanding endurance events demonstrated elevated stress, inflammatory, muscle damage and cardiac biomarkers. However, these changes did not significantly correlate with altered cardiac function. In addition, consecutive days of demanding prolonged cycling exercise did not have cumulative effects on the measured myocardial parameters.

Exertional sodium loss does not increase immediate salt appetite or dietary sodium intake in athletes.

We tested whether salt preference increases immediately after exertion-induced Na+ loss in sweat, and whether this may generalise to an increase in habitual dietary Na+ intake. For the first aim, trained athletes (n = 20) exercised in 2 ambient temperatures and sweat Na+ loss related to immediate salt preference assessed by taste, intake and psychophysical tests. For the second aim, we compared dietary and urinary Na+, and salt preference, seasoning and hedonics in the athletes and sedentary men (n = 20). No relationship was found between sodium loss during exercise and immediate preference for salt or psychophysical responses, and no differences in comparison to sedentary men. However, athlete diet had fewer foods (29.4 ± 1.5 vs 37.8 ± 1.9, p < 0.001), less seasoning (19 vs 32. p = 0.011) and more athletes reported dietary limitations (31 vs 11, p < 0.05), although nutrient content did not differ. Together these might suggest athlete adherence to a healthy diet at the expense of variety and flavour and a dissociation between dietary reports and intake. Athletes, more than controls, liked foods rich in energy and K+ suggesting compensatory-driven hedonics, although overall their intake did not differ. The findings are consistent with the absence of a salt appetite responding to Na+ loss in humans, and specifically that trained athletes do not increase their preference for salt in immediate response to exertion-induced Na+ loss and are not at risk for increased dietary Na+ compared to sedentary men.

A Fast Track to Hypoalgesia - The Anaerobic Exercise Effect on Pain Sensitivity.

Maximal anaerobic exercise, is a short high intensity effort, involves activation of the hypothalamus-pituitary-adrenal axis, and may suggest hypoalgesic effects. In addition, this exercise-induced muscle pain may contribute to hypoalgesia via the pain inhibits pain phenomenon, which is related to the diffuse noxious inhibitory control (DNIC) mechanism. We aimed to investigate whether: 1) a single bout of 30 s maximal anaerobic exercise has an analgesic effect on experimental pain sensitivity; 2) DNIC is the underlying mechanism of anaerobic exercise-induced hypoalgesia (EIH). Fifty healthy subjects participated. The experimental group performed the 'Wingate Anaerobic Test' (WAT) and controls set on the bikes without exercising. Psychophysical tests, performed before and after the intervention, in local and remote areas, included: heat (HPT) and pressure pain thresholds (PPT); suprathreshold heat and cold pain stimulation; the conditioned pain modulation (CPM) paradigm testing the DNIC mechanism. Following WAT, PPT and HPT increased (p<0.001) , pain ratings in response to heat and cold stimuli (p<0.001) and CPM (p=0.029) decreased compared with controls. No correlation was found between muscle pain, blood lactate level and EIH. To conclude WAT induces local and remote analgesic effects. The involvement of central pain modulatory processes with DNIC probably not the underline mechanism of EIH.

The effect of kinesiotape on dynamic balance following muscle fatigue in individuals with chronic ankle instability.

This study aimed to evaluate the effect of kinesiotape (KT) on dynamic stability following ankle muscle fatigue among individuals with chronic ankle instability (CAI). Twenty participants with CAI participated in the study. Participants were tested under three conditions: KT, non-elastic tape, and no tape pre- and post-fatigue of the ankle muscles. Ankle muscles fatigue was induced using an isokinetic apparatus, activity of the fibularis muscle was recorded using one-channel vibromyography (VMG), and dynamic balance and neuromuscular control were assessed using the Y-Balance Test. Following fatigue exercises, the VMG signal significantly decreased in all groups (p < 0.01), without differences between groups. No significant difference in dynamic balance test scores was found between the pre- and post-fatigue condition for each group and between groups. Our results demonstrate that KT had no significant effects on dynamic balance and muscle activity following ankle muscle fatigue among individuals with CAI.

Examination of the Effectiveness of Predictors for Musculoskeletal Injuries in Female Soldiers.

The amount of training days lost to injury during military training has highlighted the need to identify a screening tool to predict injury. One hundred and fifty-eight female soldiers from the Combat Fitness Instructor Course (CFIC) of the Israel Defense Forces volunteered to participate in this study. All soldiers were free of orthopedic and neurologic conditions for at least one month before the study. All participants performed a battery of measurements during the first week of the course. Measures included anthropometric, functional movement screen (FMS), power performances (counter movement jump [CMJ], drop jump, single leg triple hop jump [SLTH], 10-m sprint) and a 2K run. Injury data was collected throughout the 3 month course. Median tests were used to compare between injured/non-injured soldiers. Chi-square and/or logistic regression analysis was used to examine the association between various predictors and injury. Percent body fat [%BF] was higher (p = 0.04), distance for SLTH was less for both left and right legs (p = 0.029, p = 0.047 respectively) and 2K run was slower (p =0.044) in injured compared to non-injured soldiers. No differences between groups were noted in total FMS score, however more zero scores in one or more movement pattern were found in the injured group (51.35 % vs. 30.5% p=0.0293). Only %BF, 2K run and SLTH distance were significant predictors of injury (p = 0.05, p = 0.02, p =0.016 respectively). The results of this study indicated that the FMS total score is not a predictor of injury in female soldiers in a CFIC. We found that %BF, SLTH, 2K run time, 10 meter sprint time and zero scores differentiated between injured and non-injured soldiers. In addition, %BF, 2K run and SLTH were each found to be separate predictors of injury. Further research is needed to determine threshold scores that predict injury. Key pointsA total of 145 injuries were reported during the three month Combat Fitness Instructor Course in a female soldiers, 37 of these injuries resulted in absence from at least two days of training.FMS total score is not a predictor of injury in female soldiers in a CFIC. However, a score of zero, which is indicative of pain during movement, could serve as a warning sign for potential injury.%BF, SLTH, 10 meter sprint, 2K run and number of zero scores in FMS appear to differentiate between injured and non-injured soldiersSLTH, 2K run and body fat % are each separate predictors of injury for female soldiers in the CFIC.

The effect of different types of walking on dual-task performance and task prioritization among community-dwelling older adults.

BACKGROUND: The ability to safely conduct different types of walking concurrently with a cognitive task (i.e., dual task) is crucial for daily life. The contribution of different walking types to dual-task performance has not yet been determined, nor is there agreement on the strategies that older adults use to divide their attention between two tasks (task prioritization). OBJECTIVES: To compare the effect of walking in three different directions (forward, backward, and sideways) on dual-task performance and to explore the strategies of older adults to allocate their attention in response to different motor task demands. DESIGN: A cross-sectional study. SUBJECTS: Thirty-two (22 female) community-dwelling older adults (aged 72.7±5.7 years). METHODS: Subjects randomly conducted single and dual task: walking to three directions separately, cognitive tasks separately, and combination of the two. RESULTS: Walking forward was the least demanding task, during single (FW < BW, SW) (P < .001) and dual tasks (FW < BW < SW) (P < .001). The calculation of DTC revealed the same pattern (P < .001). DTC of the cognitive tasks was not significantly different among the three walking types. CONCLUSIONS: The decline mainly in the motor performance during dual task indicates that participants prioritized the cognitive task. These findings challenge the "posture first" paradigm for task prioritization.

Vagal tone, pain sensitivity and exercise-induced hypoalgesia: The effect of physical activity level.

BACKGROUND: Vagal activity has analgesic effects that are attributed to exercise-induced hypoalgesia (EIH). High vagal tone and low pain sensitivity are reported in individuals who routinely exercise yet, their association is unclear. Furthermore, it is unknown if the heightened vagal tone following high physical activity predicts and intensifies EIH. METHODS: Fifty-one healthy participants (27 low-moderately physically active; 27 females) underwent a resting-state electrocardiogram followed by heart rate variability analysis. Pain measurements, including pressure (PPT) and heat (HPT) pain thresholds, ratings of tonic heat pain (THP) and conditioned pain modulation (CPM) paradigm, were conducted pre- and post-exercise on a cycle ergometer. RESULTS: The highly active group demonstrated higher vagal tone compared to the low-moderately active (root mean square of successive differences between R-R intervals: 63.96.92 vs. 34.78 ms, p = 0.018; percentage of successive R-R intervals that exceed 50 ms: 24.41 vs. 11.52%, p = 0.012). Based on repeated-measure ANOVA, the highly active group showed higher PPT at pre-exercise, compared to the low-moderately active group (382 kPa vs. 327 kPa; p = 0.007). Post-exercise, both groups demonstrated EIH, increased HPT (p = 0.013) and decreased THP ratings (p < 0.001). Linear regression revealed that only in the low-moderately active group, higher vagal tone was associated with more efficient pre-exercise CPM and a greater reduction in THP ratings post-exercise (p ≤ 0.01). CONCLUSIONS: Highly active individuals demonstrate greater vagal tone and lower pain sensitivity but no greater EIH. Vagal tone moderates pain inhibition efficiency and EIH only in low-moderately active individuals. These findings suggest that physical activity level moderates the vagal-pain association via the endogenous analgesia system. SIGNIFICANCE: Highly physically active individuals exhibit greater vagal tone and reduced sensitivity to experimental pain, yet they do not benefit more from exercise-induced hypoalgesia (EIH) compared to low-moderately active individuals. Moreover, low-moderately active individuals with greater vagal tone exhibited more efficient endogenous pain inhibition and greater EIH, suggestive of the moderation effect of physical activity level on vagal-pain associations.

Significant exercise limitations after recovery from MIS-C related myocarditis.

BACKGROUND: Myocarditis is one of the presentations of multisystemic inflammatory syndrome in children (MIS-C) following coronavirus disease 2019 (COVID-19). Although the reported short-term prognosis is good, data regarding medium-term functional capacity and limitations are scarce. This study aimed to evaluate exercise capacity as well as possible cardiac and respiratory limitations in children recovered from MIS-C related myocarditis. METHODS: Fourteen patients who recovered from MIS-C related myocarditis underwent spirometry and cardiopulmonary exercise testing (CPET), and their results were compared with an age-, sex-, weight- and activity level-matched healthy control group (n = 14). RESULTS: All participants completed the CPET with peak oxygen uptake (peak [Formula: see text]), and the results were within the normal range (MIS-C 89.3% ± 8.9% and Control 87.9% ± 13.7% predicted [Formula: see text]). Five post-MIS-C patients (35%) had exercise-related cardio-respiratory abnormalities, including oxygen desaturation and oxygen-pulse flattening, compared to none in the control group. The MIS-C group also had lower peak exercise saturation (95.6 ± 3.5 vs. 97.6 ± 1.1) and lower breathing reserve (17.4% ± 7.5% vs. 27.4% ± 14.0% of MVV). CONCLUSIONS: Patients who recovered from MIS-C related myocarditis may present exercise limitations. Functional assessment (e.g., CPET) should be included in routine examinations before allowing a return to physical activity in post-MIS-C myocarditis. Larger, longer term studies assessing functional capacity and focusing on physiological mechanisms are needed.

Characterizing Movement Patterns of Older Individuals with T2D in Free-Living Environments Using Wearable Accelerometers.

(1) Background: Type 2 Diabetes (T2D) is associated with reduced muscle mass, strength, and function, leading to frailty. This study aims to analyze the movement patterns (MPs) of older individuals with T2D across varying levels of physical capacity (PC). (2) Methods: A cross-sectional study was conducted among individuals aged 60 or older with T2D. Participants (n = 103) were equipped with a blinded continuous glucose monitoring (CGM) system and an activity monitoring device for one week. PC tests were performed at the beginning and end of the week, and participants were categorized into three groups: low PC (LPC), medium PC (MPC), and normal PC (NPC). Group differences in MPs and physical activity were analyzed using non-parametric Kruskal-Wallis tests for both categorical and continuous variables. Dunn post-hoc statistical tests were subsequently carried out for pairwise comparisons. For data analysis, we utilized pandas, a Python-based data analysis tool, and conducted the statistical analyses using the scipy.stats package in Python. The significance level was set at p < 0.05. (3) Results: Participants in the LPC group showed lower medio-lateral acceleration and higher vertical and antero-posterior acceleration compared to the NPC group. LPC participants also had higher root mean square values (1.017 m/s2). Moreover, the LPC group spent less time performing in moderate to vigorous physical activity (MVPA) and had fewer daily steps than the MPC and NPC groups. (4) Conclusions: The LPC group exhibited distinct movement patterns and lower activity levels compared to the NPC group. This study is the first to characterize the MPs of older individuals with T2D in their free-living environment. Several accelerometer-derived features were identified that could differentiate between PC groups. This novel approach offers a manpower-free alternative to identify physical deterioration and detect low PC in individuals with T2D based on real free-living physical behavior.

The Compatibility of Children with Obesity to Self-Report Aspects of Physical Activity Domains.

Questions about the different aspects of physical activity (PA) are commonly asked in the clinical setting, yet their compatibility for use with children, particularly children with obesity (OB) is uncertain. Our aim was to investigate different PA-related questions when compared to an objective maximal cardiopulmonary exercise test (CPET) or validated questionnaires. For this study, 33 normal-weight (NW) (5 to less than 85% BMI percentile) and 35 OB (≥95% BMI percentile) children responded to three self-report PA questions evaluating PA domains (exercise capacity, limitations, and the maintenance of an active lifestyle); they also completed a maximal CPET and two validated questionnaires: the New York Heart Association (NYHA) questionnaire and the international physical activity questionnaire (IPAQ). The results regarding the NW children were highly compatible with their self-reports about exercise capacity (85%), whereas the compatibility was low (40%) in the OB group (p < 0.001). Both OB and NW groups had moderate compatibility between the self-report and objective findings regarding their exercise limitations and lifestyle with no significant differences between the groups. These findings suggest that it is inadvisable to rely on a single-item question by which to assess PA in OB children, and no definite conclusions regarding PA status should be drawn. NW children are more compatible with self-reporting their overall exercise capacity, with more limited compatibilities observed when self-reporting their limitations or lifestyle.

Plantar pressure modifications in experienced runners following an exhaustive run.

Running-induced fatigue alters foot strike pattern. The purpose of this study was to assess plantar pressure and centre of pressure (CoP) trajectory alterations after a 30-minute run at sub-maximal speed in experienced long-distance runners. Plantar pressure data from 9 experienced heel-to-toe male runners was collected before and after a 30-minute run on a treadmill at a speed 5% above the respiratory compensation point (RCP) of each participant. Significant changes in the plantar-pressure map were found post-run, including increased impulses in the first metatarsal head (9.92%, p < 0.001) and hallux areas (16.19%, p < 0.001), and decreased impulses in the fourth and fifth metatarsal heads (4.95%, p < 0.05). The CoP curve showed a medial shift (p < 0.01). The plantar-pressure map and CoP trajectory were altered following a 30-minute exhausting run. These changes may indicate an increase in stress on joints and tissues when individuals are fatigued and may promote overload injuries.

Active Lifestyle Post First Myocardial Infarction: A Comparison between Participants and Non-Participants of a Structured Cardiac Rehabilitation Program.

Following myocardial infarction (MI), impaired physical, mental, and cognitive functions can reduce participation in the community and diminish quality of life. This study aims to assess active lifestyle participation and functional performance in patients who were participants and non-participants in cardiac rehabilitation. A total of 71 patients were recruited, 6-10 months after the MI event; 38 chose to participate in a cardiac rehabilitation (CR) program, and 33 did not (NCR). Participation and activity patterns in instrumental activities of daily living, as well as physically demanding leisure activities and social activities, were evaluated using the Activity Card Sort (ACS). Hand grip force and timed up and go (TUG) were tested. A total of 74% of the CR group met physical activity recommendations and only 34% continued to smoke, compared to 39% and 71% in the NCR group, respectively. The CR group, compared to the NCR group, had higher levels of daily activity, social leisure, and physically demanding leisure activities (p ≤ 0.001). Null differences between the NCR and CR groups were observed in grip strength and the TUG tests. The study highlighted community participation after MI. Based on a comparison between the groups, the study implies that patients choosing to participate in CR retained higher community participation levels and had better self-management of cardiovascular risk factors.

Susceptibility to movement-evoked pain following resistance exercise.

OBJECTIVE: To investigate the: (1) role of basic muscle pain sensitivity and psychological factors in the prediction of movement-evoked pain (MEP) following delayed onset muscle soreness (DOMS), and (2) association of MEP with changes in systemic muscle pain sensitivity following DOMS induction. METHODS: Fifty-one participants were assigned to either eccentric resistance exercise or control groups. They completed questionnaires evaluating psychological distress and underwent muscle pain sensitivity evaluation by the pressure pain threshold (PPT) test at the exercised and remote muscles, before and 24 hours following the intervention. MEP intensity was determined in response to lifting a 3kg canister using a visual analogue scale (VAS). RESULTS: The exercise group demonstrated MEP intensity of 5/10 on VAS and reduced PPTs at the main exercised muscle (p<0.001). A regression tree analyses revealed that the level of anxiety trait predicted a higher MEP intensity. A secondary analysis showed that 53% participants who were DOMS responders (MEP > mild intensity; ≥ 3/10 VAS) exhibited decreased PPTs in the exercised (p<0.001) and remote (p = 0.027) muscles following eccentric exercise. Characterization of DOMS responders revealed that, at baseline, they had lower PPTs in the exercised (p = 0.004) and remote (p = 0.001) muscles and reported higher psychological distress i.e., anxiety trait and depression symptoms (p<0.05), compared to non-responders. A regression analysis revealed that lower PPT or high levels of anxiety trait increased the probability to become a responder (p = 0.001). CONCLUSIONS: Susceptibility to MEP following DOMS is determined by muscle pain hypersensitivity and high levels of anxiety trait. MEP at the early stage of DOMS is linked with an increase in systemic muscle pain sensitivity suggestive of central mechanisms. This knowledge is valuable in translating science into clinical musculoskeletal pain management.

Heat acclimation and exercise training interact when combined in an overriding and trade-off manner: physiologic-genomic linkage.

Combined heat acclimation (AC) and exercise training (EX) enhance exercise performance in the heat while meeting thermoregulatory demands. We tested the hypothesis that different stress-specific adaptations evoked by each stressor individually trigger similar cardiac alterations, but when combined, overriding/trade-off interactions take place. We used echocardiography, isolated cardiomyocyte imaging and cDNA microarray techniques to assay in situ cardiac performance, excitation-contraction (EC) coupling features, and transcriptional programs associated with cardiac contractility. Rat groups studied were controls (sedentary 24°C); AC (sedentary, 34°C, 1 mo); normothermic EX (treadmill at 24°C, 1 mo); and heat-acclimated, exercise-trained (EXAC; treadmill at 34°C, 1 mo). Prolonged heat exposure decreased heart rate and contractile velocity and increased end ventricular diastolic diameter. Compared with controls, AC/EXAC cardiomyocytes demonstrated lower l-type Ca(2+) current (I(CaL)) amplitude, higher Ca(2+) transient (Ca(2+)T), and a greater Ca(2+)T-to-I(CaL) ratio; EX alone enhanced I(CaL) and Ca(2+)T, whereas aerobic training in general induced cardiac hypertrophy and action potential elongation in EX/EXAC animals. At the genomic level, the transcriptome profile indicated that the interaction between AC and EX yields an EXAC-specific molecular program. Genes affected by chronic heat were linked with the EC coupling cascade, whereas aerobic training upregulated genes involved with Ca(2+) turnover via an adrenergic/metabolic-driven positive inotropic response. In the EXAC cardiac phenotype, the impact of chronic heat overrides that of EX on EC coupling components and heart rate, whereas EX regulates cardiac morphometry. We suggest that concerted adjustments induced by AC and EX lead to enhanced metabolic and mechanical performance of the EXAC heart.

A rat model of exercise-induced asthma: a nonspecific response to a specific immunogen.

Exercise-induced bronchoconstriction (EIB) is common; however, key aspects of its pathogenesis are still unclear. We investigated the feasibility of adapting an established animal model of asthma to investigate the earliest stages of EIB. The hypothesis was that a single exposure to a normally innocuous, and brief, exercise challenge could trigger EIB symptoms in rats previously sensitized to ovalbumin (OVA) but otherwise unchallenged. Brown-Norway rats were sensitized by intraperitoneal injection of OVA at 0 and 2 wk. At week 3, animals were exposed to either aerosolized OVA (SS) or exercise (EXS). A trained, blinded, clinical observer graded EIB by respiratory sounds. Plasma and lung cytokine levels were analyzed. No control rats with or without exercise (EX, CON) showed evidence of EIB. Eighty percent of the SS group demonstrated abnormal breath sounds upon exposure to aerosolized OVA. Approximately 30% of EXS rats sensitized to OVA but exposed only to exercise had abnormal breath sounds. Lung tissue levels of TNF-α, IL-1α, growth-related oncogene/keratinocyte/chemoattractant, and IFN-γ were significantly higher (P < 0.001) in the SS group, relative to all other groups. Changes in most of these cytokines were not notable in the EXS rats, suggesting a different mechanism of EIB. Remarkably, IFN-γ, but not the other cytokines measured, was significantly elevated following brief exercise in both sensitized and unsensitized rats. Exercise led to detectable breathing sound abnormalities in sensitized rats, but less severe than those observed following classical OVA challenge. Precisely how this immune crossover occurs is not known, but this model may be useful in elucidating essential mechanisms of EIB.

Exercise and leukocyte interchange among central circulation, lung, spleen, and muscle.

Circulating leukocytes increase rapidly with exercise then quickly decrease when the exercise ends. We tested whether exercise acutely led to bidirectional interchange of leukocytes between the circulation and the lung, spleen, and active skeletal muscle. To accomplish this it was necessary to label a large number of immune cells (granulocytes, monocytes, and lymphocytes) in a way that resulted in minimal perturbation of cell function. Rats were injected intravenously with a single bolus of carboxyfluorescein diacetate succinamidyl ester (CFSE) dye which is rapidly and irreversibly taken up by circulating cells. The time course of the disappearance of labeled cells and their reappearance in the circulation following exercise was determined via flow cytometry. The majority of circulating leukocytes were labeled at 4h. post-injection and this proportion slowly declined out to 120 h. At both 24 and 120 h, running resulted in an increase in the proportion of labeled leukocytes in the circulation. Analysis of the skeletal muscle, spleen and lung indicated that labeled leukocytes had accumulated in those tissues and were mobilized to the circulation in response to exercise. This indicates that there is an ongoing exchange of leukocytes between the circulation and tissues and that exercise can stimulate their redistribution. Exchange was slower with muscle than with spleen and lung, but in all cases, influenced by exercise. Exercise bouts redistribute leukocytes between the circulation and the lung, spleen and muscle. The modulatory effects of exercise on the immune system may be regulated in part by the systemic redistribution of immune cells.

Effect of dynamic tape on postural sway in individuals with chronic ankle instability.

OBJECTIVE: To examine the effects of dynamic tape on balance control in subjects with chronic ankle instability (CAI). METHODS: This two group experimental pre- and post-treatment design included 18 individuals with CAI and 18 controls. The single-limb stance test with eyes open and closed, standing on a force plate (Accusway Plus; AMTI) for 30 s, was conducted before, 10 min (T1) and 24 h (T24) after a dynamic tape application over the gastrocnemius muscle. Outcome measurements were: mean sway velocity, sway area (circular area), and standard deviation of the body center of pressure path length in both mediolateral and anteroposterior directions. Individuals with poor (unable to perform a single leg test for at least 30 s, eyes closed) vs. good postural stability, were also compared. RESULTS: In both groups, a repeated analysis of variance demonstrated a significant time main effect on sway velocity (F = 14.95; p < 0.001) and path length (F = 14.95; p < 0.001) during eyes closed. Post-hoc analysis revealed a significant decrease in T1 values compared to baseline. When comparing individuals with poor vs good stability amongst the CAI group, a statistically significant interaction was observed between group, time on sway velocity and path length (F = 3.92; p < 0.05) during eyes closed. In the poor postural group, most T1 values were significantly lower than baseline. CONCLUSIONS: Dynamic tape when applied to posterior calf muscles, enhanced balance control with no difference between CAI individuals and controls. The contribution of the tape was greater in those with poor postural stability.

The Effect of Incorporating an Exergame Application in a Multidisciplinary Weight Management Program on Physical Activity and Fitness Indices in Children with Overweight and Obesity.

Children with overweight/obese (OW/OB) have low physical activity (PA) levels and excessive daily screen times. Although access to personal smartphones may complicate restricting sedentary screen time, these devices may be used to promote PA and improve fitness. Therefore, we aim to examine the impact of incorporating an exergame application (APP) into an existing weight management program on BMI, physical activity, fitness levels, and attitude toward PA among OW/OB children. Seventy-nine children (51% girls), median age 10 years, completed an established 5-month weight management program. The intervention included structured PA sessions (2/week), nutritional, and behavioral counseling. An exergame app was installed on the smartphones of the intervention group (APP, n = 32). BMI, physical fitness, PA level, and attitudes toward PA were assessed before and after the intervention. BMI decreased (p < 0.0001) in both groups by 0.67 kg/m2 (Q1, Q3: -1.36-0.12). There were improvements in more fitness components in the APP group than controls, with significantly greater improvements in aerobic fitness (p = 0.038), speed and agility (p = 0.01), and leg strength endurance (p = 0.05) compared to controls. PA levels increased similarly in both groups during the intervention period. The incorporation of an exergame application leads to more significant improvements in fitness components. These findings support the use of exergame apps to improve fitness in OW/OB children.