Influence of Air Resistance on Ground Reaction Forces During Treadmill Running

INTRODUCTION: Running is fundamentally driven by forces applied to the ground, eliciting ground reaction forces (GRFs) which accelerate the runner. These GRFs are divided into vertical, anteroposterior, and mediolateral components. As running speed alters, so do the patterns of these forces. By juxtaposing these GRF patterns with metabolic data, we can discern how movement patterns adapt across different running conditions. One of the key distinctions between treadmill and overground running is the influence of air resistance. METHODS: The study involved twenty-four active male runners experienced in achieving a sub-17-minute-5km or equivalent performance. The main objective was to examine the influence of air resistance on running biomechanics. Participants underwent two data collection sessions. During the sessions, various parameters such as height, weight were recorded, and the influence of different air resistance conditions on their running mechanics was studied. RESULTS: Braking Impulse, Propulsive Impulse, Horizontal Impulse, and Mean Force all demonstrated significant effects with respect to the wind conditions. Specifically, the effect of condition was significant for propulsive impulse and braking impulse, horizontal impulse, and mean force. These variables showed differences across the various wind conditions tested. CONCLUSION: We investigated the biomechanical effects of horizontal impeding forces on runners. Our results highlight how these forces alter running mechanics. With increased resistance, runners showed marked changes in propulsive and braking impulses, indicating adjustments in their gait. Aspects like ground time and stride length remained consistent, while horizontal forces primarily affected anterior-posterior running mechanics

GravityCam: Higher Resolution Visible Wide-Field Imaging

The limits to the angular resolution achievable with conventional ground-based telescopes are unchanged over 70 years. Atmospheric turbulence limits image quality to typically ~1 arcsec in practice. We have developed a new concept of ground-based imaging instrument called GravityCam capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. The acquisition of visible images at high speed without significant noise penalty has been made possible by advances in optical and near IR imaging technologies. Images are recorded at high speed and then aligned before combination and can yield a 3-5 fold improvement in image resolution. Very wide survey fields are possible with widefield telescope optics. We describe GravityCam and detail its application to accelerate greatly the rate of detection of Earth size planets by gravitational microlensing. GravityCam will also improve substantially the quality of weak shear studies of dark matter distribution in distant clusters of galaxies. The microlensing survey will also provide a vast dataset for asteroseismology studies. In addition, GravityCam promises to generate a unique data set that will help us understand of the population of the Kuiper belt and possibly the Oort cloud.This is the author accepted manuscript. The final version is available from http://dx.doi.org/10.1117/12.223090

Multiwavelength observations of the Be/X-ray binary 4U1145-619

We report optical and infrared observations of the massive X-ray binary system 4U1145-619 (V801 Cen) which show that the circumstellar disc of the Be star component is in decline. Infrared J,H,K,L magnitudes of V801Cen have been monitored from 1993 March to 1996 April. H alpha spectra have been obtained throughout the same period. We find that both the infrared excess and the Balmer emission have been in decline throughout the period of observations. A 13 year optical and X-ray history of the source has been collated, revealing a possible correlation between the optical and X-ray activity. In addition, we have used u,v,b,y,beta indices, corrected for both circumstellar and interstellar effects, to calculate the physical parameters of the underlying B star.Comment: 8 pages postscript. Accepted by MNRA

Effect of Air Resistance on Braking and Propulsive Impulses During Treadmill Running.

Treadmill running is a convenient option for runners looking to avoid adverse environmental conditions or that prefer a gym setting. Outdoor running includes air resistance, whereas treadmill running typically does not. Very little research has been focused on the influence of air resistance and its role on kinetic factors during running. PURPOSE: To determine how anterior/posterior impulses change due to air resistance during two different treadmill speeds. METHODS: A wind tunnel was placed 0.61m from the edge of a force instrumented treadmill (Bertec, Boston, MA) while attempting to run 1.12m from the opening of it. Seven subjects ran at two speeds (3.35 m/s, 4.46 m/s) on two separate visits while alternating the order of speeds run. During each speed, runners completed one minute of running during conditions of no fan and a fan representing air resistance equal to treadmill speed. Forces were collected for the final 25s segment of each air velocity. RESULTS: At the faster treadmill speed, horizontal impulse was significantly greater in the propulsive direction during the air resistance condition (5.3% ± 7.4%, p=0.019). Braking impulses were smaller (-3.2% ± 5.1%, p=0.035) while propulsive impulse remained non-significant (2.1% ± 4.5%, p=0.104). At the slower treadmill speed, horizontal impulse was trending toward significance (3.1% ± 5.9%, p=0.080) while braking impulse remained non-significant (-1.2% ± 2.8%, p=0.147) and propulsive impulse was greater with air resistance (2.3% ± 3.3%, p=0.024). CONCLUSION: The current data begins to explain that in order to keep metabolic costs low while still compensating for air resistance during running, individuals will increase net horizontal impulse by opting to decrease braking impulse while maintaining propulsive impulse. These findings match the work of Chang and Kram (2000) who asserted that “the metabolic cost of generating horizontal propulsive forces during normal running constitutes more than one-third of the total cost of steady-speed running”

Optical Polarimetry of the May 2022 Lunar Eclipse

The sunlight reflected from the Moon during a total lunar eclipse has been transmitted through the Earth's atmosphere on the way to the Moon. The combination of multiple scattering and inhomogeneous atmospheric characteristics during that transmission can potentially polarize that light. A similar (although much smaller) effect should also be observable from the atmosphere of a transiting exoplanet. We present the results of polarization observations during the first 15 minutes of totality of the lunar eclipse of 2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2 +/- 0.3 per cent in V, 0.5 +/- 0.2 per cent in R and 0.2 +/- 0.2 per cent in I. Our polarization values lie in the middle of the range of those reported for previous eclipses, providing further evidence that the induced polarization can change from event to event. We found no significant polarization difference (<0.02 per cent) between a region of dark Mare and nearby bright uplands or between the lunar limb and regions closer to the disk centre due to the different angle of incidence. This further strengthens the interpretation of the polarization's origin being due to scattering in the Earth's atmosphere rather than by the lunar regolith.Comment: Accepted for publication in MNRA

MOPTOP: Multi-colour Optimised Optical Polarimeter

Polarimetric measurements are essential for the study of jetted sources associated with black holes, such as γ-ray bursts and blazars. The relativistic jets launched from regions close to the black hole are threaded with magnetic fields, which produce synchrotron emission, and can be studied with polarimetric measurements. The multi-colour, optimised, optical polarimeter (MOPTOP) is a multi-band imaging instrument designed for use on the Liverpool Telescope. By replacing the rotating polaroid with a half wave plate and beam splitter, the instrument utilises twice as much of the incoming beam of light from the telescope compared to its predecessor, Ringo3. MOPTOP also builds on the successful introduction of dichroic mirrors to perform simultaneous multi-waveband polarimetric and photometric analysis in Ringo3, and enhances the sensitivity of the instrument with sCMOS cameras to use all photons as efficiently as possible

Optical Polarimetry of the May 2022 Lunar Eclipse

The sunlight reflected from the Moon during a total lunar eclipse has been transmitted through the Earth's atmosphere on the way to the Moon. The combination of multiple scattering and inhomogeneous atmospheric characteristics during that transmission can potentially polarize that light. A similar (although much smaller) effect should also be observable from the atmosphere of a transiting exoplanet. We present the results of polarization observations during the first 15 minutes of totality of the lunar eclipse of 2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2 +/- 0.3 per cent in V, 0.5 +/- 0.2 per cent in R and 0.2 +/- 0.2 per cent in I. Our polarization values lie in the middle of the range of those reported for previous eclipses, providing further evidence that the induced polarization can change from event to event. We found no significant polarization difference (<0.02 per cent) between a region of dark Mare and nearby bright uplands or between the lunar limb and regions closer to the disk centre due to the different angle of incidence. This further strengthens the interpretation of the polarization's origin being due to scattering in the Earth's atmosphere rather than by the lunar regolith.Comment: Accepted for publication in MNRA