Video measurement of linear displacement along an oblique line using the cross-ratio

The purpose of this study was to rediscover the cross-ratio and assess its effectiveness for measuring linear displacement when the image plane is not parallel to the object plane. In the laboratory a fixed, 4m object length was reconstructed with a mean absolute error of 2.6mm (s.d. = 1.6mm, maximum = 4.9mm). In the field, two cameras filmed a fixed, 8m object length with a mean absolute error of 13mm (s.d. = 5mm, maximum = 20mm). The method is very accessible to non-specialists in projective geometry and the results are both valid and reliable

VIDEO MEASUREMENT OF LINEAR DISPLACEMENT ALONG AN OBLIQUE LINE USING THE CROSS-RATIO

The purpose of this study was to rediscover the cross-ratio and assess its effectiveness for measuring linear displacement when the image plane is not parallel to the object plane. In the laboratory a fixed, 4m object length was reconstructed with a mean absolute error of 2.6mm (s.d. = 1.6mm, maximum = 4.9mm). In the field, two cameras filmed a fixed, 8m object length with a mean absolute error of 13mm (s.d. = 5mm, maximum = 20mm). The method is very accessible to non-specialists in projective geometry and the results are both valid and reliable

Statistical analysis in JASP: a guide for students

This document is a collection of standalone handouts covering the most common standard (frequentist) statistical analyses used by students studying Biological Sciences. Datasets used in this document are available for download from https://osf.io/bx6uv

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients

Low-stakes, VLE intensive, formative approach to maths teaching as a pedagogic strategy for improving assessment outcomes

Functional numeracy skills in the UK workforce have been an issue for at least 20 years and are of mounting concern due to the increasing use of technology in the workplace and the need for mathematical problem solving skills. Surveys reveal anxiety related to maths (MA) has a negative impact on Higher Education (HE) subject choices and subsequent career options. This at a time when Science, Technology, Engineering and Mathematics (STEM) subjects, requiring maths and data handling skills, are in high demand globally.This case study relates the journey from discovering the need for maths support in science students to the use of low-stakes, VLE intensive, formative maths support as a means of overcoming MA and improving student outcomes

Does whole body vibration have clinically significant neurophysiological and neurovascular implications?

Whole body vibration has received much attention as an innovative approach to exercise, leading to constantly increasing attention fro m the scientific community. Previous research considering occupational vibration has illustrated the risks associated with high levels of exposure to vibration; however during vibration exercise the exposure duration is much shorter and therefore the potential complications must be reconsidered. This review brings together research from various aspects of occupational vibration, clinical research and vibration exercise to address issues within the context of health and safety with a particular focus on neurophysiological and neurovascular responses. The results indicate that peripheral nerve and blood vessels are exposed to risks such as compression, shear stress and altered function as a response to vibration. However, correct planning and implementation of exercise protocols should effectively control these risks. By summarising the areas that have received attention an overview of potential complications will be achieved; with an understanding of which factors prevent participation and those that simply require an amended approach to vibration exercise

La eficacia de diferentes protocolos de ejercicios para prevenir la incidencia de lesión isquiotibial en atletas.

Introducción: La distensión de los músculos isquiotibiales es la lesión, sin contacto, más frecuente asociada a la participación deportiva.Además de las características anatómicas y funcionales de los isquiotibiales, tales como la organización biarticular, o la bi-inervación de bíceps femoral; un número de factores modificables y no modificables, se han asociado con el riesgo de lesiones de los músculos isquiotibiales en atletas. Cada una de estas variables podría tener un impacto sobre el riesgo de lesión en un enfoque integral; por lo cual la posibilidad de sufrir una lesión puede variar dependiendo de las circunstancias particulares de cada atleta. El objetivo de esta revisión crítica, es examinar los efectos de los actuales protocolos de ejercicios preventivos y proporcionar directrices básicas para la prevención de lesiones de los isquiotibiales en los atletas.Discusión:Las lesiones de los isquiotibiales se producen durante las acciones de alta velocidad, o de estiramiento extremo; por lo tanto, con el fin de prevenir la incidencia de este tipo de lesiones, el estiramiento activo específico, los ejercicios de estiramiento, o ejercicios específicos del deporte, se han integrado en los programas regulares de entrenamiento. La respuesta a estos programas de intervención ha mostrado resultados mixtos.Se presenta un marco conceptual, proponiendo que un programa eficaz de prevención de lesiones debe incluir una combinación de diferentes ejercicios específicos y no específicos. Además, debe tenerse una consideración especial sobre los ejercicios excéntricos realizados sobre los músculos estirados, y también hacer hincapié en las acciones de co-contracción de los isquiotibiales, en la estabilidad de la rodilla.Conclusión: Los efectos protectores provocados por un programa de prevención bien diseñado, podrían ser obtenidos en cuatro semanas, con sólo dos sesiones semanales, incluyendo tres series de seis a ocho repeticiones, con tres ejercicios de cadena cinética abierta y cerrada. Las investigaciones futuras deberían analizar las modificaciones estructurales y funcionales específicas, provocadas por la aplicación regular de los diferentes tipos de ejercicios y protocolos, destinados a reducir el riesgo de lesión en los músculos isquiotibiales

Analysis of the hamstring muscle activation during two injury prevention exercises

The aim of this study was to perform an electromyographic and kinetic comparison of two commonly used hamstring eccentric strengthening exercises: Nordic Curl and Ball Leg Curl. After determining the maximum isometric voluntary contraction of the knee flexors, ten female athletes performed 3 repetitions of both the Nordic Curl and Ball Leg Curl, while knee angular displacement and electromyografic activity of the biceps femoris and semitendinosus were monitored. No significant differences were found between biceps femoris and semitendinosus activation in both the Nordic Curl and Ball Leg Curl. However, comparisons between exercises revealed higher activation of both the biceps femoris (74.8 ± 20 vs 50.3 ± 25.7%, p = 0.03 d = 0.53) and semitendinosus (78.3 ± 27.5 vs 44.3 ± 26.6%, p = 0.012, d = 0.63) at the closest knee angles in the Nordic Curl vs Ball Leg Curl, respectively. Hamstring muscles activation during the Nordic Curl increased, remained high (>70%) between 60 to 40° of the knee angle and then decreased to 27% of the maximal isometric voluntary contraction at the end of movement. Overall, the biceps femoris and semitendinosus showed similar patterns of activation. In conclusion, even though the hamstring muscle activation at open knee positions was similar between exercises, the Nordic Curl elicited a higher hamstring activity compared to the Ball Leg Curl

Perceptual, mechanical and electromyographic responses to different relative loads in the parallel squat

The effectiveness of the OMNI-RES (0-10) and the electromyographic signal for monitoring changes in the movement velocity was examined during a set to muscular failure using different percentages of one repetition maximum (1RM) in the parallel squat exercise (PSQ). Twelve males (26.3 ± 5.8 years) were evaluated on eight separate days with 48 hours of rest between sessions. After determining the 1RM value, participants underwent seven tests until achieving muscular failure with the following percentage ranges: 30 to 90%. An optical rotary encoder measured mean accelerative velocity (MAV) and the OMNI-RES (0-10) scale was used to express the Rating of Perceived Exertion (RPE) after every repetition of each set. Additionally, the normalized root mean square (RMS) signal of the surface electromyography (N-EMG) was calculated for the vastus medialis muscle. The RPE expressed after the first repetition and when the maximum value of MAV was achieved along the sets was lower (p 0.8) than the RPE that corresponded to a 10% drop in MAV and at failure. Additionally, the initial RPE was useful to distinguish different loading zones by anchoring the OMNI-RES value to the magnitude of the relative load (<60%, 60 to <70% or ≤ 70% 1RM). Similar patterns were observed using the N-EMG. In conclusion, apart from differentiating between relative loads during a set to failure in the PSQ, the RPE and the N-EMG can both reflect changes associated with the initial, maximal, 10% drop in movement velocity and the muscular failure

Bayesian inference in JASP: a guide for students

This is a collection of standalone handouts covering the most common Bayesian statistical analyses available in JASP for students studying Biological Sciences. Datasets used in this document are available for download from https://osf.io/8qtu2