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Petrofsky, Jerrold,Laymon, M.,Mcgrew, R.,Papa, D.,Hahn, R.,Kaethler, R.,Johnson, M.,Wernow, B.,Poblete, D. korean Academy of Physical Therapy Rehabilitation 2013 Physical therapy rehabilitation science Vol.2 No.1
Objective: To determine the energy consumed and muscle use during dance compared to different standard exercise devices. Design: Longitudinal study. Methods: Fifteen female subjects were evaluated to assess the energy cost and muscle activity during a 20 minute dance video compared to treadmill, elliptical track and bicycle ergometry. The later 3 forms of exercise were accomplished in four, 5 minute bouts at different intensities of exercise. Subjects were in the age range of 22-24 years old, were free of cardiovascular disease and did not have any neurological injuries. They were not sedentary and exercised at least twice a week. During the exercise, muscle activity was measured by the electromyogram recorded by surface electrodes on 6 muscle groups. A Cosmed metabolic cart was used to measure oxygen consumption during the exercise. Results: The aerobic dance video that was tested here was equivalent to a hard workout on any of the 3 exercise modalities. The dance routine was equivalent in terms of energy consumed to running at 225 watts of work or running for 20 minutes at a speed of 2 meters per second (4.47 miles per hour). Compared to the bicycle, it was equivalent to cycling at 112 watts for 20 minutes (2.25 kpm), and for the elliptical trainer, dance was equivalent to 435 watts. Concerning muscle use, the dance routine was the most balanced for upper, core and lower body muscles. Although the elliptical trainer was close, it required muscle less muscle use. Conclusion: A good dance video can be more effective than standard exercise equipment.
Faraday-Shielded dc Stark-Shift-Free Optical Lattice Clock
Beloy, K.,Zhang, X.,McGrew, W. F.,Hinkley, N.,Yoon, T. H.,Nicolodi, D.,Fasano, R. J.,Schä,ffer, S. A.,Brown, R. C.,Ludlow, A. D. American Physical Society 2018 Physical Review Letters Vol.120 No.18
<P>We demonstrate the absence of a dc Stark shift in an ytterbium optical lattice clock. Stray electric fields are suppressed through the introduction of an in-vacuum Faraday shield. Still, the effectiveness of the shielding must be experimentally assessed. Such diagnostics are accomplished by applying high voltage to six electrodes, which are grounded in normal operation to form part of the Faraday shield. Our measurements place a constraint on the dc Stark shift at the 10(-20) level, in units of the clock frequency. Moreover, we discuss a potential source of error in strategies to precisely measure or cancel nonzero dc Stark shifts, attributed to field gradients coupled with the finite spatial extent of the lattice-trapped atoms. With this consideration, we find that Faraday shielding, complemented with experimental validation, provides both a practically appealing and effective solution to the problem of dc Stark shifts in optical lattice clocks.</P>
( Jerrold Petrofsky ),( M Laymon ),( R Mcgrew ),( D Papa ),( R Hahn ),( R Kaethler ),( M Johnson ),( B Wernow ),( D Poblete ) 물리치료재활과학회 2013 Physical therapy rehabilitation science Vol.2 No.1
Objective: To determine the energy consumed and muscle use during dance compared to different standard exercise devices. Design: Longitudinal study. Methods: Fifteen female subjects were evaluated to assess the energy cost and muscle activity during a 20 minute dance video compared to treadmill, elliptical track and bicycle ergometry. The later 3 forms of exercise were accomplished in four, 5 minute bouts at different intensities of exercise. Subjects were in the age range of 22-24 years old, were free of cardiovascular disease and did not have any neurological injuries. They were not sedentary and exercised at least twice a week. During the exercise, muscle activity was measured by the electromyogram recorded by surface electrodes on 6 muscle groups. A Cosmed metabolic cart was used to measure oxygen consumption during the exercise. Results: The aerobic dance video that was tested here was equivalent to a hard workout on any of the 3 exercise modalities. The dance routine was equivalent in terms of energy consumed to running at 225 watts of work or running for 20 minutes at a speed of 2 meters per second (4.47 miles per hour). Compared to the bicycle, it was equivalent to cycling at 112 watts for 20 minutes (2.25 kpm), and for the elliptical trainer, dance was equivalent to 435 watts. Concerning muscle use, the dance routine was the most balanced for upper, core and lower body muscles. Although the elliptical trainer was close, it required muscle less muscle use. Conclusion: A good dance video can be more effective than standard exercise equipment.