Voluntary Activation and Variability During Maximal Dynamic Contractions with Aging

Whether reduced supraspinal activation contributes to age-related reductions in maximal torque during dynamic contractions is not known. The purpose was to determine whether there are age differences in voluntary activation and its variability when assessed with stimulation at the motor cortex and the muscle during maximal isometric, concentric, and eccentric contractions. Thirty young (23.6 ± 4.1 years) and 31 old (69.0 ± 5.2 years) adults performed maximal isometric, shortening (concentric) and lengthening (eccentric) contractions with the elbow flexor muscles. Maximal isometric contractions were performed at 90° elbow flexion and dynamic contractions at a velocity of 60°/s. Voluntary activation was assessed by superimposing an evoked contraction with transcranial magnetic stimulation (TMS) or with electrical stimulation over the muscle during maximal voluntary contractions (MVCs). Old adults had lower MVC torque during isometric (− 17.9%), concentric (− 19.7%), and eccentric (− 9.9%) contractions than young adults, with less of an age difference for eccentric contractions. Voluntary activation was similar between the three contraction types when assessed with TMS and electrical stimulation, with no age group differences. Old adults, however, were more variable in voluntary activation than young (standard deviation 0.99 ± 0.47% vs. 0.73 ± 0.43%, respectively) to both the motor cortex and muscle, and had greater coactivation of the antagonist muscles during dynamic contractions. Thus, the average voluntary activation to the motor cortex and muscle did not differ with aging; however, supraspinal activation was more variable during maximal dynamic and isometric contractions in the old adults. Lower predictability of voluntary activation may indicate subclinical changes in the central nervous system with advanced aging

Mechanisms for the Age-related Increase in Fatigability of the Knee Extensors in Old and Very Old Adults

The mechanisms for the age-related increase in fatigability during high-velocity contractions in old and very old adults ({greater than or equal to}80 yrs) are unresolved. Moreover, whether the increased fatigability with advancing age and the underlying mechanisms differ between men and women are not known. The purpose of this study was to quantify the fatigability of knee extensor muscles and identify the mechanisms of fatigue in 30 young (22.6 {plus minus} 0.4 yrs; 15 men), 62 old (70.5 {plus minus} 0.7 yrs; 33 men), and 12 very old (86.0 {plus minus} 1.3 yrs; 6 men) men and women elicited by high-velocity concentric contractions. Participants performed 80 maximal velocity contractions (1 contraction per 3 s) with a load equivalent to 20% of the maximum voluntary isometric contraction. Voluntary activation and contractile properties were quantified before and immediately following exercise (\u3c10 \u3es) using transcranial magnetic stimulation and electrical stimulation. Absolute mechanical power output was 97% and 217% higher in the young compared to old and very old adults, respectively. Fatigability (reductions in power) progressively increased across age groups, with a power loss of 17% in young, 31% in old, and 44% in very old adults. There were no sex differences in fatigability among any of the age groups. The age-related increase in power loss was strongly associated with changes in the involuntary twitch amplitude (r=0.75,

Physical Activity Modulates Corticospinal Excitability of the Lower Limb in Young and Old Adults

Aging is associated with reduced neuromuscular function, which may be due in part to altered corticospinal excitability. Regular physical activity (PA) may ameliorate these age-related declines, but the influence of PA on corticospinal excitability is unknown. The purpose of this study was to determine the influence of age, sex, and PA on corticospinal excitability by comparing the stimulus-response curves of motor evoked potentials (MEP) in 28 young (22.4 ± 2.2 yr; 14 women and 14 men) and 50 old adults (70.2 ± 6.1 yr; 22 women and 28 men) who varied in activity levels. Transcranial magnetic stimulation was used to elicit MEPs in the active vastus lateralis muscle (10% maximal voluntary contraction) with 5% increments in stimulator intensity until the maximum MEP amplitude. Stimulus-response curves of MEP amplitudes were fit with a four-parameter sigmoidal curve and the maximal slope calculated (slopemax). Habitual PA was assessed with tri-axial accelerometry and participants categorized into either those meeting the recommended PA guidelines for optimal health benefits (\u3e10,000 steps/day, high-PA; n = 21) or those not meeting the guidelines (n = 41). The MEP amplitudes and slopemax were greater in the low-PA compared with the high-PA group (P \u3c 0.05). Neither age nor sex influenced the stimulus-response curve parameters (P \u3e 0.05), suggesting that habitual PA influenced the excitability of the corticospinal tract projecting to the lower limb similarly in both young and old adults. These findings provide evidence that achieving the recommended PA guidelines for optimal health may mediate its effects on the nervous system by decreasing corticospinal excitability

Physical Activity Modulates Corticospinal Excitability of the Lower Limb in Young and Old Adults

Aging is associated with reduced neuromuscular function, which may be due in part to altered corticospinal excitability. Regular physical activity (PA) may ameliorate these age-related declines, but the influence of PA on corticospinal excitability is unknown. The purpose of this study was to determine the influence of age, sex, and PA on corticospinal excitability by comparing the stimulus-response curves of motor evoked potentials (MEP) in 28 young (22.4 ± 2.2 yr; 14 women and 14 men) and 50 old adults (70.2 ± 6.1 yr; 22 women and 28 men) who varied in activity levels. Transcranial magnetic stimulation was used to elicit MEPs in the active vastus lateralis muscle (10% maximal voluntary contraction) with 5% increments in stimulator intensity until the maximum MEP amplitude. Stimulus-response curves of MEP amplitudes were fit with a four-parameter sigmoidal curve and the maximal slope calculated (slopemax). Habitual PA was assessed with tri-axial accelerometry and participants categorized into either those meeting the recommended PA guidelines for optimal health benefits (\u3e10,000 steps/day, high-PA; n = 21) or those not meeting the guidelines (n = 41). The MEP amplitudes and slopemax were greater in the low-PA compared with the high-PA group (P \u3c 0.05). Neither age nor sex influenced the stimulus-response curve parameters (P \u3e 0.05), suggesting that habitual PA influenced the excitability of the corticospinal tract projecting to the lower limb similarly in both young and old adults. These findings provide evidence that achieving the recommended PA guidelines for optimal health may mediate its effects on the nervous system by decreasing corticospinal excitability

Investigation of the Frequency Response of Constant Voltage Anemometers in Turbulent Flows

Résumé Un prototype d’anémomètre disponible dans le commerce, l’anémomètre à voltage constant (CVA), est présenté et son principe de fonctionnement est étudié et analysé. Nous détaillons les différentes procédures et corrections qui doivent être appliquées aux signaux de tension afin d’obtenir les signaux de vitesse correspondant, et cela inclut l’inertie thermique du capteur. Les résultats sont comparés à un autre type d’anémomètre très répandu en recherche et dans l’industrie, l’anémomètre à température constante (CTA), à des fins de validation. Les mesures sont effectuées dans la région turbulente d’un jet turbulent axisymétrique, et incluent des vitesses moyennes, des écarts-types de fluctuations de vitesse et des densités spectrales d’énergie. Sur une même plage d’opération, nous montrons que les deux systèmes donnent des résultats similaires. Le CVA sous-estime légèrement les écarts-types de vitesse donnés par le CTA, ce qui est attribué a un effet non-linéaire. Nous montrons que la fréquence de coupure du CVA est plus élevée que le plus couramment utilisé CTA, et que le bruit électronique est plus faible. L’anémomètre à voltage constant offre donc une excellente alternative à l’anémomètre à température constante pour les écoulements faiblement turbulents dont le contenu fréquentiel est riche, comme les écoulements supersoniques et hypersoniques.----------Abstract A commercially available anemometer system considered as a prototype, the constant voltage anemometer (CVA), is presented and its working principle is studied and analyzed. We detail the different procedures and corrections that have to be applied to voltage signals to deduce corresponding velocity signals, including the effect of the thermal inertia of the sensor. Results are compared to another anemometer system widely used in research and industry, the constant temperature anemometer (CTA), for validation requirements. Measurements are performed in the turbulent region of a subsonic axisymmetric jet and include mean velocities, root-mean-square (rms) values of velocity fluctuations and power spectral densities. In the same range of operation, we show that the two instruments give similar results. The CVA anemometer slightly underestimates the rms velocity values given by the CTA anemometer which is attributed to a non-linear effect. We show that the cut-off frequency of the CVA system is higher than the more commonly used CTA system, and that the electronic noise level is lower. The constant voltage anemometer is thus an excellent alternative to the constant temperature anemometer for low turbulent flows with rich frequency content, such as supersonic and hypersonic flows

Cellular immune reactions of the sunn pest, Eurygaster integriceps, to the entomopathogenic fungus, Beauveriabassiana and its secondary metabolites

In this study, five morphological types of circulating hemocytes were recognized in thehemolymph of the adult sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae),namely prohemocytes, plasmatocytes, granulocytes, adipohemocytes, and oenocytoids. Theeffects of the secondary metabolites of the entomopathogenic fungus Beauveria bassiana oncellular immune defenses of Eurygaster integriceps were investigated. The results showed thatthe fungal secondary metabolites inhibited phagocytic activity of E. integriceps hemocytes andhampered nodule formation. A reduction of phenoloxidase activity was also observed. The datasuggest that B. bassiana produce secondary metabolites that disable several immune mechanismsallowing the fungus to overcome and then kill its host. This characteristic makes B. bassiana apromising model for biological control of insect pests such as E. integriceps

Analysis of relationships between altitude and distance from volcano with Stomach Cancer incidence using a geographic information system

Gastric cancer (GC) is the fifth most common cancer in the world, with a wide variation in incidence rates across different geographical areas. In Iran GC is the most common cancer in males and it is reported to be the third most prevalent after breast and colorectal in females. A geographical information system (GIS) allows investigation of the geographical distribution of diseases. The purpose of the present study was to explore the relationship between gastric cancer and effective climatic factors using GIS. The dispersion distribution and the relationship between environmental factors effective on cancer were measured using Arc GIS. Of all cases, 672 (73.8) were in males with a sex ratio of 3 to1. The highest incidence by cities was seen in Namin with 137.5 per 100,000. The results of this study showed that the distribution of GC around the Sabalan volcanic mountain was significantly higher than other places in the same province. These results can be considered as a window to future comprehensive research on gastric cancer

Effect of Physical Guidance on Learning a Tracking Task in Children with Cerebral Palsy

The purpose of this study was to investigate the effect of physical guidance (PG) frequency on learning a tracking task in children with hemiplegic spastic cerebral palsy (CP). For this purpose, 25 children, aged 7–15 years with CP affecting the left side of the body, who were classified in levels II–III of Manual Abilities Classification System (MACS) and levels III–IV of Gross Motor Function Classification System (GMFCS), were recruited from 10 clinical centers. A pre-test including two blocks of 12 trials of the tracking task without any PG was performed by all participants, after that they were assigned into five homogenous groups (with 100%, 75%, 50%, 25%, and 0% of PG) through blocked randomization according to their age. All participants involved in an intervention consisted of eight sessions (four blocks of 12 trials in each session) practicing a tracking task. The 0% PG group received no PG, the 25% PG group received PG for three trials, the 50% PG group received PG for six trials, the 75% PG group received PG for nine trials, and the 100% PG group received PG for all twelve trials. PG consisted of placing the experimenter’s hand around the child’s less-involved hand guiding to stay on the track and complete the task. Learning was inferred by acquisition and delayed retention tests. The results showed that the higher frequency of PG led to more accurate performance during practice phase. However, the group that received 75% PG had significantly better performance compared to the other groups in the retention phase. It is concluded that optimum level of PG, about 75% of trials, can be helpful for learning a tracking task in children with spastic hemiplegic CP, supporting the challenge point framework

Endurance Training and Royal Jelly Consumption Effects on Dopamine in Rats with Alzheimer's disease

Introduction: Alzheimer's disease may be a sort of amnesia with brain dysfunction that gradually degrades the patient's mental abilities. The purpose of this study was to research the effect of endurance training with royal jelly consumption on dopamine in the hippocampus tissue of Alzheimer's rats with trimethyltin. Methods: During this study, 30 rats underwent injection of 8 milligram / Kilograms trimethyltin chloride and were divided into groups of 6 rats: control, training, royal jelly consumption, and training with royal jelly consumption. 6 rats were included in the healthy control group to be evaluated the effects of Alzheimer's induction on dopamine levels. The training groups were active on the treadmill for 8 weeks. The royal jelly consumption groups received 100 milligram / Kilograms royal jelly per day peritoneally for 8 weeks. The Kolmogorov-Smirnov, one-way ANOVA, and Tukey’s post hoc tests were used to analyze the findings. (P ≤0.05). Results: Alzheimer's induction with trimethyltin toxin had a Significant Impact on reducing dopamine gene levels (P = 0.04); royal jelly, training, and training with royal jelly consumption had a significant effect on increasing dopamine gene expression levels (P = 0.001). Also, the effect of training with Royal Jelly was greater than training or royal jelly consumption alone. (P = 0.001) Conclusions: Although training and royal jelly consumption improve dopamine gene expression levels in the hippocampus tissue of rats with Alzheimer's disease, the effects of training combined with royal jelly consumption appear to be greater than those of royal jelly consumption alone

Estimation of cardiovascular and respiratory diseases attributed to PM10 using AirQ model in Urmia during 2011-2017

Background: Quantification of the attributed effects of air pollution determines the impact of air pollutants on the community and shows the critical condition of air quality. This study aimed to quantify and estimate the cardiovascular and respiratory diseases attributed to PM10 in Urmia during 2011-2016. Methods: In this descriptive-analytic study, at first, hourly data of pollutant PM10 concentrations were received from air pollutants station located in the Department of Environmental Protection. The data were evaluated using AirQ2.2.3 software after primary and secondary processes and filtering. Results: The results showed that the mean annual concentration of PM10 during 2011-2016 was 88.66, 92.45, 81.22, 78.38, 113.78, and 92.67 μg /m3, respectively. The number of hospitalized cases due to respiratory diseases attributed to PM10 in this period was 486, 525, 459, 453, 684, and 552, respectively, and the number of cases due to cardiovascular diseases was 188, 203, 177, 175, 263, and 213, respectively. Conclusion: Considering the attributed health effects of PM10, the necessary measures should be taken to identify the causative agents and to understand the mechanisms of these processes and correct them. © Iran University of Medical Sciences