scholarly journals Motor unit recruitment patterns of the quadriceps differ between continuous high- and low-torque isometric knee extension to momentary failure

2021 ◽  
Author(s):  
Jonathan Murphy ◽  
Emma Hodson-Tole ◽  
Andrew D Vigotsky ◽  
Jim R Potvin ◽  
James P Fisher ◽  
...  
Keyword(s):  
Motor Unit ◽  
Knee Extension ◽  
Frequency Characteristics ◽  
Myoelectric Signals ◽  
Mean Frequency ◽  
Isometric Knee Extension ◽  
Frequency Components ◽  
The Mean ◽  
Low Torque ◽  
Over Time

The size principle is a theory of motor unit (MU) recruitment that suggests MUs are recruited in an orderly manner from the smallest (lower threshold) to the largest (higher threshold) MUs. A consequence of this biophysical theory is that, for isometric contractions, recruitment is dependent on the intensity of actual effort required to meet task demands. This concept has been supported by modelling work demonstrating that, in tasks performed to momentary failure, full MU recruitment will have occurred upon reaching failure irrespective of the force requirements of the task. However, in vivo studies examining this are limited. Therefore, the aim of the current study was to examine MU recruitment of the quadriceps under both higher- and lower-torque (70% and 30% of MVC, respectively) isometric knee extension, performed to momentary failure. Specifically, we compared surface electromyography (sEMG) frequency characteristics, determined by wavelet analysis, across the two continuous isometric knee extension tasks to identify potential differences in recruitment patterns. A convenience sample of 10 recreationally active adult males (height: mean = 179.6, SD = 6.0 cm; mass: mean = 76.8, SD = 7.3 kg; age: mean = 26 SD = 7 years) with previous resistance training experience (mean = 6, SD = 3 years) were recruited. Using a within-session, repeated-measures, randomised crossover design participants performed the knee extension tasks whilst sEMG was collected from the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL). Myoelectric signals were decomposed into intensities as a function of time and frequency using an EMG-specific wavelet transformation. Our first analysis compared the mean frequency at momentary failure; second, we investigated the effects of load on relative changes in wavelet intensities; finally, we quantified the degree of wavelet similarity over time. Wavelet-based calculation of the mean signal frequency appeared to show similar mean frequency characteristics occurring when reaching momentary failure. However, individual wavelets revealed that different changes in frequency components occurred between the two tasks, suggesting that patterns of recruitment differed. Low-torque conditions resulted in an increase in intensity of all frequency components across the trials for each muscle whereas high-torque conditions resulted in a wider range of frequency components contained within the myoelectric signals at the beginning of the trials. However, as the low-torque trial neared momentary failure there was an increased agreement between conditions across wavelets. Our results corroborate modelling studies as well as recent biopsy evidence, suggesting overall MU recruitment may largely be similar for isometric tasks performed to momentary failure with the highest threshold MUs likely recruited, despite being achieved with differences in the pattern of recruitment over time utilised.

An ePIC Assessment of Quadriceps Motor Unit Firing Patterns During Isometric Knee Extension: A High Density Surface Electromyography Study

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Gregory E. Pearcey ◽  
Obaid Ul Haq Khurram ◽  
Edward H. Kim ◽  
Sai Voora ◽  
Christopher K. Thompson ◽  
...  
Keyword(s):  
Motor Unit ◽  
Surface Electromyography ◽  
Knee Extension ◽  
High Density ◽  
Firing Patterns ◽  
Motor Unit Firing ◽  
Isometric Knee Extension ◽  
Density Surface

Non-stationary Myoelectric Signals and Muscle Fatigue

2000 ◽  
Vol 39 (02) ◽  
pp. 125-129 ◽  
Author(s):  
R. N. Scott ◽  
D. MacIsaac ◽  
P. A. Parker
Keyword(s):  
Computer Simulation ◽  
Power Spectrum ◽  
Myoelectric Signal ◽  
Myoelectric Signals ◽  
Mean Frequency ◽  
Downward Shift ◽  
Final Study ◽  
Modulation Model ◽  
The Mean ◽  
Mathematical Derivation

Abstract:A mathematical derivation for the mean frequency of a myoelectric signal (MES) is provided based on an amplitude modulation model for non-stationary MES. With this derivation, it is shown that mean frequency estimates of stationary and non-stationary myoelectric signals theoretically are not significantly different in a physiologically practical context. While this prediction is confirmed via a computer simulation, it is refuted with empirical evidence. Regardless, it is shown in a final study that mean frequency is capable of tracking a downward shift in the power spectrum with fatigue even in non-stationary myoelectric signals.

scholarly journals Fish Protein Ingestion Induces Neural, but Not Muscular Adaptations, Following Resistance Training in Young Adults

2021 ◽  
Vol 8 ◽  
Author(s):  
Kohei Watanabe ◽  
Aleš Holobar ◽  
Kenji Uchida ◽  
Yukiko Mita
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Resistance Training ◽  
Motor Unit ◽  
Muscle Mass ◽  
Knee Extension ◽  
Fish Protein ◽  
Motor Unit Firing ◽  
Isometric Knee Extension ◽  
Protein Ingestion

Purpose: Nutritional supplementation in conjunction with exercise is of interest for the prevention or improvement of declines in motor performances in older adults. An understanding of the effects on both young and older adults contributes to its effective application. We investigated the effect of fish protein ingestion with resistance training on neural and muscular adaptations in young adults using interventions and assessments that have already been tested in older adults.Methods: Eighteen young adults underwent 8 weeks of isometric knee extension training. During the intervention, nine participants ingested 5 g of fish protein (n = 9, Alaska pollack protein, APP), and the other nine participants ingested casein as a control (n = 9, CAS) in addition to daily meals. Before, during, and after the intervention, the isometric knee extension force, lower extremity muscle mass, and motor unit firing pattern of knee extensor muscles were measured.Results: Maximum voluntary contraction (MVC) was significantly increased in both APP and CAS groups from 0 weeks to 4, 6, and 8 weeks of intervention (p < 0.001), but there were no significant differences between the groups (p = 0.546–0.931). Muscle mass was not significantly changed during the intervention in either group (p = 0.250–0.698). Significant changes in motor unit firing rates (p = 0.02 and 0.029 for motor units recruited at 20–40% of MVC and at 40–60%) were observed following the intervention in the APP but not CAS (p = 0.120–0.751) group.Conclusions: These results suggest that dietary fish protein ingestion changes motor unit adaptations following resistance training in young adults.

scholarly journals Kinetic analysis and optimisation of 18F-rhPSMA-7.3 PET imaging of prostate cancer

2021 ◽  
Author(s):  
Simona Malaspina ◽  
Vesa Oikonen ◽  
Anna Kuisma ◽  
Otto Ettala ◽  
Kalle Mattila ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Metastatic Disease ◽  
Uptake Kinetics ◽  
Whole Body ◽  
Target Area ◽  
Post Injection ◽  
The Mean ◽  
Pet Radiopharmaceutical ◽  
Time Frames ◽  
Over Time

Abstract Purpose This phase 1 open-label study evaluated the uptake kinetics of a novel theranostic PET radiopharmaceutical, 18F-rhPSMA-7.3, to optimise its use for imaging of prostate cancer. Methods Nine men, three with high-risk localised prostate cancer, three with treatment-naïve hormone-sensitive metastatic disease and three with castration-resistant metastatic disease, underwent dynamic 45-min PET scanning of a target area immediately post-injection of 300 MBq 18F-rhPSMA-7.3, followed by two whole-body PET/CT scans acquired from 60 and 90 min post-injection. Volumes of interest (VoIs) corresponding to prostate cancer lesions and reference tissues were recorded. Standardised uptake values (SUV) and lesion-to-reference ratios were calculated for 3 time frames: 35–45, 60–88 and 90–118 min. Net influx rates (Ki) were calculated using Patlak plots. Results Altogether, 44 lesions from the target area were identified. Optimal visual lesion detection started 60 min post-injection. The 18F-rhPSMA-7.3 signal from prostate cancer lesions increased over time, while reference tissue signals remained stable or decreased. The mean (SD) SUV (g/mL) at the 3 time frames were 8.4 (5.6), 10.1 (7) and 10.6 (7.5), respectively, for prostate lesions, 11.2 (4.3), 13 (4.8) and 14 (5.2) for lymph node metastases, and 4.6 (2.6), 5.7 (3.1) and 6.4 (3.5) for bone metastases. The mean (SD) lesion-to-reference ratio increases from the earliest to the 2 later time frames were 40% (10) and 59% (9), respectively, for the prostate, 65% (27) and 125% (47) for metastatic lymph nodes and 25% (19) and 32% (30) for bone lesions. Patlak plots from lesion VoIs signified almost irreversible uptake kinetics. Ki, SUV and lesion-to-reference ratio estimates showed good agreement. Conclusion 18F-rhPSMA-7.3 uptake in prostate cancer lesions was high. Lesion-to-background ratios increased over time, with optimal visual detection starting from 60 min post-injection. Thus, 18F-rhPSMA-7.3 emerges as a very promising PET radiopharmaceutical for diagnostic imaging of prostate cancer. Trial Registration NCT03995888 (24 June 2019).

scholarly journals A New Multiplatform Model for Outpatient Prenatal and Postpartum Care in a Cohort of COVID-19-Affected Obstetric Patients

2021 ◽  
Vol 18 (10) ◽  
pp. 5144
Author(s):  
Mar Muñoz-Chápuli Gutiérrez ◽  
Ana Durán-Vila ◽  
Javier Ruiz-Labarta ◽  
Pilar Payá-Martínez ◽  
Pilar Pintado Recarte ◽  
...  
Keyword(s):  
Clinical Manifestations ◽  
Specific Treatment ◽  
Rt Pcr ◽  
Good Adherence ◽  
Major Morbidity ◽  
Reference Hospital ◽  
The Mean ◽  
Discharge From Hospital ◽  
Over Time

Spain was one of the epicenters of the first wave of the COVID-19 pandemic. We describe in this article the design and results of a new telephone-and-telematic multiplatform model of systematic prenatal and postpartum follow-up for COVID-19-affected women implemented in a tertiary reference hospital in Madrid. We included patients with RT-PCR-confirmed COVID-19 during pregnancy or delivery from 10 March 2020 to 15 December 2020. We had a total of 211 obstetric patients: 148 (70.1%) were tested at the onset of suspicious clinical manifestations and 62 (29.4%) were tested in the context of routine screening. Of all the patients, 60 women (28.4%) were asymptomatic and 97 (46%) presented mild symptoms. Fifty-one women (24.2%) were admitted to our hospital for specific treatment because of moderate or severe symptoms. We had no missed cases and a good adherence. The mean number of calls per patient was 2.3. We performed 55 in-person visits. We analyzed the complexity of our program over time, showing a two-wave-like pattern. One patient was identified as needing hospitalization and we did not record major morbidity. Telemedicine programs are a strong and reproducible tool to reach to pregnant population affected by COVID-19, to assess its symptoms and severity, and to record for pregnancy-related symptoms both in an outpatient regime and after discharge from hospital.

Adaptors and Innovators: Selection versus Induction

1991 ◽  
Vol 68 (3_suppl) ◽  
pp. 1283-1290 ◽  
Author(s):  
P. A. Holland ◽  
I. Bowskill ◽  
A. Bailey
Keyword(s):  
Cognitive Style ◽  
Past Research ◽  
Significant Shift ◽  
Occupational Groups ◽  
Significant Difference ◽  
The Mean ◽  
New Entrants ◽  
Innovative Cognitive Style ◽  
Over Time ◽  
Established Group

The hypothesis that predictable differences would exist between the mean cognitive style of new entrants and those of the longer serving “established” employees in certain departments while not in others was tested. Data from 99 employees from four departments of a large British pharmaceuticals company who completed the Kirton Adaption-Innovation Inventory provided results broadly in line with the expectations of adaption-innovation theory and past research. The mean innovative cognitive style of new entrants to adaptive departments regressed towards the mean of the establishment and the occupational mean over time. In departments where there was no initial significant difference between the mean cognitive style of the new entrants and the established group, no significant shift was shown over time. Implications of these findings are suggested. The data also indicated norms for two occupational groups where previously they did not exist.

The underrepresentation of female participants in studies assessing the impact of high-dose exercise on cardiovascular outcomes: a scoping review

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
S Pallikadavath ◽  
R Patel ◽  
CL Kemp ◽  
M Hafejee ◽  
N Peckham ◽  
...  
Keyword(s):  
Scoping Review ◽  
High Volume ◽  
Cardiovascular Outcomes ◽  
High Dose ◽  
Funding Sources ◽  
Review Protocol ◽  
The Mean ◽  
The Impact ◽  
Over Time ◽  
Funding Acknowledgements

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Cardiovascular adaptations as a result of exercise conducted at high-intensity and high-volume are often termed the ‘Athlete’s heart’. Studies have shown that these cardiovascular adaptations vary between sexes. It is important that both sexes are well represented in this literature. However, many studies assessing the impact of high-dose exercise on cardiovascular outcomes under-recruit female participants. Purpose This scoping review aimed to evaluate the representation of females in studies assessing the impact of high-dose exercise on cardiovascular outcomes and demonstrate how this has changed over time. Methods The scoping review protocol as outlined by Arksey and O’Malley was used. OVID and EMBASE databases were searched and studies independently reviewed by two reviewers. Studies must have investigated the effects of high-dose exercise on cardiovascular outcomes. To assess how the recruitment of females has changed over time, two methods were used. One, the median study date was used to categorise studies into two groups. Two, studies were divided into deciles to form ten equal groups over the study period. Mean percentage of female recruitment and percentage of studies that failed to include females were calculated. Results Overall, 250 studies were included. Over half the studies (50.8%, n = 127) did not include female participants. Only 3.2% (n = 8) did not include male participants. Overall, mean percentage recruitment was 18.2%. The mean percentage of recruitment was 14.5% before 2011 and 21.8% after 2011. The most recent decile of studies demonstrated the highest mean percentage of female recruitment (29.3%) and lowest number of studies that did not include female participants (26.9%). Conclusion Female participants are significantly underrepresented in studies assessing cardiovascular outcomes caused by high-dose exercise. The most recent studies show that female recruitment may be improving, however, this still falls significantly short for equal representation. Risk factors, progression and management of cardiovascular diseases vary between sexes, hence, translating findings from male dominated data is not appropriate. Future investigators should aim to establish barriers and strategies to optimise fair recruitment. Mean percentage females recruited per study (%) Percentage studies that do not include women (%) Overall (n = 250) 18.2 50.8 (n = 127) Studies before 2011 (n = 121) 14.5 59.5 (n = 72) Studies after 2011 (n = 129) 21.8 42.6 (n = 55) Table 1: Female recruitment characteristics. The year 2011 (median study year) was chosen as this divides all included studies into two equal groups.

scholarly journals Complex Regional Pain Syndrome: Current Practice Management and Referral Trends in a Closed Healthcare System

Osteology ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 39-47
Author(s):  
Connor Zale ◽  
Joshua Hansen ◽  
Paul Ryan
Keyword(s):  
Pain Management ◽  
Pain Score ◽  
Complex Regional Pain Syndrome ◽  
Healthcare System ◽  
Pain Syndrome ◽  
Occupational Outcomes ◽  
Mean Delay ◽  
Significant Difference ◽  
The Mean ◽  
Over Time

Background: Complex regional pain syndrome (CRPS) is a neurologic condition that can present with severe pain and dysfunction. Delay in treatment adversely affects outcomes. The purpose of this study is to evaluate patient outcomes as they relate to the time from diagnosis to pain management referral once the diagnosis of CRPS has been made in a closed healthcare system. Methods: A retrospective record review from a closed healthcare system was utilized for CRPS cases from 2010–2019. Demographics, injury pattern, surgeries, pain score, treatment modalities, occupational outcomes, and time to pain management referral were recorded. Results: There were 26 cases of CRPS that met inclusion criteria. The mean time from diagnosis to treatment was 55 days. 16/26 (61.5%) were medically discharged from the military. 23/26 (88.5%) were unable to return to full duty due to CRPS. There was no significant difference in the reported pain scores over time regardless of treatment (p = 0.76). A linear regression demonstrated a significantly higher Visual Analog Scale Pain Score (VAS) over time in patients that were medically discharged (p = 0.022). Conclusions: The mean delay in referral to the pain service was 55 days. The majority of patients (88.5%) did not return to full duty secondary to the diagnosis of CRPS, and 61.5% of patients required medical separation from active duty. Due to the negative impact that the diagnosis of CRPS has on occupational outcomes with a mean delay in referral of 55 days, clinics and providers should set up referral criteria and establish early pain pathways for patients diagnosed with CRPS.

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