Brachialis muscle activity can be assessed with surface electromyography

The brachialis muscle (BR) represents an important elbow flexor and its activity has so far mainly been measured with intramuscular electromyography (EMG). The aim of this study was to examine whether the activity of the BR can be assessed with surface EMG without interference from the biceps brachii (BB). With eight subjects we measured surface EMG of the arm flexor synergists, BR, BB, and brachioradialis (BRR) during two isometric voluntary contraction types: (1) pure elbow flexion and (2) elbow flexion with a superimposed forearm supination. Since the BR and BB have a distinct biomechanical function, an individual activity of the BR can be expected for the second contraction type, if the BR can be assessed independently from the BB. The correlation coefficients between EMG amplitudes and flexion force (supination torque) were determined. During pure flexion the activities of all synergists were similarly correlated with the flexion force (r = 0.96 ± 0.02). During flexion + supination the activity of the BR was distinct from the activity of the BB, with a 14% higher correlation for the BR with the flexion force and a 40–64% lower correlation with the supination torque. The BB predicted supination torque substantially better than the BR and BRR (r = 0.93 ± 0.02). The current results demonstrate that the activity of the BR can be assessed with surface EMG as it was distinct from the BB during flexion + supination but predicted flexion force equally well as BB during the pure flexion contraction

Medical specialty certification exams studied according to the Ottawa Quality Criteria: a systematic review.

BACKGROUND Medical specialty certification exams are high-stakes summative assessments used to determine which doctors have the necessary skills, knowledge, and attitudes to treat patients independently. Such exams are crucial for patient safety, candidates' career progression and accountability to the public, yet vary significantly among medical specialties and countries. It is therefore of paramount importance that the quality of specialty certification exams is studied in the scientific literature. METHODS In this systematic literature review we used the PICOS framework and searched for papers concerning medical specialty certification exams published in English between 2000 and 2020 in seven databases using a diverse set of search term variations. Papers were screened by two researchers independently and scored regarding their methodological quality and relevance to this review. Finally, they were categorized by country, medical specialty and the following seven Ottawa Criteria of good assessment: validity, reliability, equivalence, feasibility, acceptability, catalytic and educational effect. RESULTS After removal of duplicates, 2852 papers were screened for inclusion, of which 66 met all relevant criteria. Over 43 different exams and more than 28 different specialties from 18 jurisdictions were studied. Around 77% of all eligible papers were based in English-speaking countries, with 55% of publications centered on just the UK and USA. General Practice was the most frequently studied specialty among certification exams with the UK General Practice exam having been particularly broadly analyzed. Papers received an average of 4.2/6 points on the quality score. Eligible studies analyzed 2.1/7 Ottawa Criteria on average, with the most frequently studied criteria being reliability, validity, and acceptability. CONCLUSIONS The present systematic review shows a growing number of studies analyzing medical specialty certification exams over time, encompassing a wider range of medical specialties, countries, and Ottawa Criteria. Due to their reliance on multiple assessment methods and data-points, aspects of programmatic assessment suggest a promising way forward in the development of medical specialty certification exams which fulfill all seven Ottawa Criteria. Further research is needed to confirm these results, particularly analyses of examinations held outside the Anglosphere as well as studies analyzing entire certification exams or comparing multiple examination methods

Increase in heterogeneity of biceps brachii activation during isometric submaximal fatiguing contractions: a multichannel surface EMG study

The effects of fatigue emerge from the beginning of sustained submaximal contractions, as shown by an increase in the amplitude of the surface electromyogram (EMG). The increase in EMG amplitude is attributed to an augmentation of the excitatory drive to the motor neuron pool that, more importantly than increasing discharge rates, recruits additional motor units for the contraction. The aim of this study was to determine whether the spatiotemporal distribution of biceps brachii (BB) activity becomes more or less heterogeneous during a fatiguing isometric contraction sustained at a submaximal target force. Multiple electrodes were attached over the entire BB muscle, and principal component analysis (PCA) was used to extract the representative information from multiple monopolar EMG channels. The development of heterogeneity during the fatiguing contraction was quantified by applying a cluster algorithm on the PCA-processed EMG amplitudes. As shown previously, the overall EMG amplitude increased during the sustained contraction, whereas there was no change in coactivation of triceps brachii. However, EMG amplitude did not increase in all channels and even decreased in some. The change in spatial distribution of muscle activity varied across subjects. As found in other studies, the spatial distribution of EMG activity changed during the sustained contraction, but the grouping and size of the clusters did not change. This study showed for the first time that muscle activation became more heterogeneous during a sustained contraction, presumably due to a decrease in the strength of common inputs with the recruitment of additional motor units

Does Quantum Mechanics Clash with the Equivalence Principle - and Does it Matter?

With an eye on developing a quantum theory of gravity, many physicists have recently searched for quantum challenges to the equivalence principle of general relativity. However, as historians and philosophers of science are well aware, the principle of equivalence is not so clear. When clarified, we think quantum tests of the equivalence principle won't yield much. The problem is that the clash/not-clash is either already evident or guaranteed not to exist. Nonetheless, this work does help teach us what it means for a theory to be geometric.Comment: 12 page

Lower between-limb asymmetry during running on treadmill compared to overground in subjects with laterally pronounced knee osteoarthritis

Subjects with knee osteoarthritis (KOA) show gait asymmetries evidenced by lower knee flexion and shorter contact times for the affected leg. Interestingly, running on a treadmill compared to running overground is also associated with lower knee flexion and shorter contact times. Thus, it is of particular interest how gait patterns are influenced by the type of ground in subjects with KOA. The aim of the current study was therefore to measure the overground asymmetry of kinematic parameters in KOA subjects while running and to investigate whether this asymmetry is altered on a treadmill. Nine patients diagnosed with KOA underwent overground and treadmill running with 3D-motion analysis. The symmetry analysis was performed using Symmetry Angles for five selected gait parameters: contact and step time, heel-toe delay, maximal knee flexion during stance and vertical speed variance. For all parameters, the values were significantly lower for the affected compared to the non- affected leg (p≤0.023). Post-hoc analyses revealed significant differences between legs only overground and not on the treadmill. The asymmetry was lower on the treadmill, as indicated by significant Symmetry Angle reductions for contact time (p = 0.033), knee flexion (p = 0.001) and vertical speed variance (p = 0.002). The symmetry increase on the treadmill was mainly due to changes of the non-affected leg towards the affected leg values leading to smaller steps and less impact load in general. The present results suggest therefore that a) an assessment of symmetry may differ depending on the ground type (treadmill versus overground) and b) treadmill running may be more suitable for patients with KOA related gait asymmetries

Task-Dependent Inhomogeneous Muscle Activities within the Bi-Articular Human Rectus Femoris Muscle

The motor nerve of the bi-articular rectus femoris muscle is generally split from the femoral nerve trunk into two sub-branches just before it reaches the distal and proximal regions of the muscle. In this study, we examined whether the regional difference in muscle activities exists within the human rectus femoris muscle during maximal voluntary isometric contractions of knee extension and hip flexion. Surface electromyographic signals were recorded from the distal, middle, and proximal regions. In addition, twitch responses were evoked by stimulating the femoral nerve with supramaximal intensity. The root mean square value of electromyographic amplitude during each voluntary task was normalized to the maximal compound muscle action potential amplitude (M-wave) for each region. The electromyographic amplitudes were significantly smaller during hip flexion than during knee extension task for all regions. There was no significant difference in the normalized electromyographic amplitude during knee extension among regions within the rectus femoris muscle, whereas those were significantly smaller in the distal than in the middle and proximal regions during hip flexion task. These results indicate that the bi-articular rectus femoris muscle is differentially controlled along the longitudinal direction and that in particular the distal region of the muscle cannot be fully activated during hip flexion