Week and weekend day cadence patterns long-term post-bariatric surgery

Obesity can negatively influence walking cadence, reducing the overall intensity of daily activities and increasing the risk of weight gain. Purpose: Objectively describe the walking cadence of individuals’ long-term post-bariatric surgery. Methods: Fifty-eight participants, 51.2 ± 8.9 years old, with a BMI of 34.6 ± 10.1 kg/m2, 10.0 ± 3.1 years post-surgery wore an activPAL accelerometer for 7 consecutive days. Data was analyzed using participants’ current BMI, dichotomized by obesity status, < or ≥ 30 kg/m2. Results: On average, participants walked 5124 ± 2549 steps/day on weekdays and 6097 ± 2786 steps/day on weekend days (p = .003). Participants spent the majority (75%) of their daily steps at a slow-walking average cadence (non-obese: week = 65.3 ± 5.0 steps/min and weekend = 63.8 ± 6.7 steps/min; obese: week = 67.8 ± 8.2 steps/min and weekend = 63.3 ± 6.9 steps/min), with no difference between groups for week or weekend days (p = .153 and .774). The cadence of participants with obesity was significantly lower on weekends compared to weekdays for walking events > 30 s (p = .002) and > 60 s (p = .008) in duration. Weekday cadence of participants without obesity was similar to weekend day cadence across all walking event durations. The majority of walking events occurred below 30 s in duration for all participants. Conclusions: Long-term post-bariatric surgery, movement occurs in short duration bouts at a slow-walking cadence for the majority of movement. Individuals without obesity had similar movement patterns from week to weekend days while participants with obesity significantly lowered their cadence on weekend days

The Confrontation between General Relativity and Experiment

The status of experimental tests of general relativity and of theoretical frameworks for analysing them is reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational-wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and other binary pulsar systems have yielded other tests, especially of strong-field effects. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.Comment: 89 pages, 8 figures; an update of the Living Review article originally published in 2001; final published version incorporating referees' suggestion

Exploring new physics frontiers through numerical relativity

The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein's equations - along with some spectacular results - in various setups. We review techniques for solving Einstein's equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology

Varying constants, Gravitation and Cosmology

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit