Methods of Rhythm Measurement
Sue Binkley in Biological Clocks, 2020
A particular time point of a rhythm is a phase. The time difference between two phases is called the phase angle. When a rhythm is altered so that its peaks occur later in time, the phase of a rhythm is delayed; when a rhythm is altered so that its peaks occur early in time, the rhythm is advanced, a phase advance. The application of these ideas is clear in people. When we travel east across time zones (as when an American flies to Europe), we encounter earlier sunrises with respect to our time back home. Our internal rhythms must advance in order to synchronize with the new external time zone at our destination. When we journey westward (as when a European flied to America), a delay is required for our rhythms to synchronize, a phase delay. Advances and delays are called phase shifts.
Introduction
Nicholas Stergiou in Nonlinear Analysis for Human Movement Variability, 2018
To model this phenomenon, Haken et al. (1985) developed the HKB model to capture the collective variable dynamics of this phenomenon. A collective variable is a variable that captures collective ordering or collective organization or a behavior. The collective variable identified for coordinated finger wiggling is relative phase (ϕ). As shown in Figure 1.17a relative phase is calculated by starting with the time series of the angle of oscillation of the component oscillators (i.e., fingers), and then calculating the phase of these oscillators. Here phase is simply defined in a space with dimensions of angle, and rate or change of angle (i.e., angular velocity). This phase space can be represented as a phase portrait in which we can calculate a phase angle (θ) for each oscillator. Relative phase is calculated as the difference in phase angle between the two phase angles. This collective variable captures in-phase coordination with a relative phase of 0° and antiphase coordination with a relative phase of 180°.
Electric and magnetic fields
James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney in Basic Introduction to Bioelectromagnetics, 2018
Two sinusoids expressed in the form of Eq. (1.9) are said to be in phase if their phase angles are equal, which means they line up in time. They are said to be out of phase when their phase angles are not equal, in which case they will not line up in time. Figure 1.26 shows two functions, g1(t) and g2(t), that are out of phase by π/6 radians. Phase angles and differences in phase are often specified in degrees, done by converting the angles in units of radians to angles in units of degrees, although it is not strictly correct to do so because ωt has units of radians and ϕ and ωt must have the same units. (To convert from radians to degrees, multiply the radians by 180/π. To convert from degrees to radians, multiply the degrees by π/180.) Thus, g1(t) and g2(t) are said to be out of phase by π/6 radians, or 30°.
The decrease in phase angle measured by bioelectrical impedance analysis reflects the increased locomotive syndrome risk in community-dwelling people: The Yakumo study
Published in Modern Rheumatology, 2019
Satoshi Tanaka, Kei Ando, Kazuyoshi Kobayashi, Tetsuro Hida, Taisuke Seki, Takashi Hamada, Kenyu Ito, Mikito Tsushima, Masayoshi Morozumi, Masaaki Machino, Kyotaro Ota, Naoki Ishiguro, Yukiharu Hasegawa, Shiro Imagama
For body composition analysis, arm and leg muscle mass and phase angle were measured using BIA. The Inbody 770 BIA unit (Inbody Co., Ltd., Seoul, Korea) was used. This system differentiates tissues, such as fat, muscle, and bone, based on their electrical impedances [20]. Participants grasped the handles of the analyzer with embedded electrodes and stood on a platform with the soles of the feet in contact with the electrodes (two electrodes for each foot and hand). The accuracy of this method has been shown to be comparable to that of computed tomography cross-sectional area [21]. The appendicular skeletal muscle mass index (ASMI) was calculated using the following formula: ASMI = arm and leg skeletal muscle mass (kg)/height2 (m2) [22]. BIA measures whole-body impedance and the opposition of the body to alternating currents consisting of the following two components: resistance and reactance. Phase angle was determined at a single frequency (50 kHz) and was calculated using the impedance and reactance of the whole body according to the following formula: phase angle (°) = (reactance/resistance) × (180°/π). This phase angle is calculated automatically by the BIA device.
Phase Angle Evaluation of Lung Disease Patients and Its Relationship with Nutritional and Functional Parameters
Published in Journal of the American College of Nutrition, 2021
Priscila Berti Zanella, Camila Coutinho Àvila, Fernanda Cardoso Chaves, Marcelo Basso Gazzana, Danilo Cortozi Berton, Marli Maria Knorst, Carolina Guerini de Souza
In recent years, bioelectrical impedance analysis (BIA) has been widely used for body composition analysis in different patient groups, as it is a noninvasive, practical, low-cost method whose results are easily reproducible and quickly obtained (6,7). The method consists in the passage of a high-frequency, low-amplitude electric current through the body, which acts as a biological conductor (8). The body offers two types of resistance to electric current, capacitive resistance or reactance (Xc) and resistive resistance (R), and impedance is the term used to describe the combination of these two types of resistance. R reflects the opposition to current flow exerted by intracellular and extracellular contents, being directly related to the water content. Xc results from the opposition to current flow exerted by cell membranes and tissue interfaces by means of capacitance, i.e., the membranes store the energy of the electric current for a short time, and this “slows down” their conduction, generating a drop in voltage and a phase shift (9). This phase shift is geometrically quantified by the arctangent of the Xc/R ratio, which is called phase angle (PhA) (10). Thus, PhA is positively associated with Xc, where higher values reflect better cellularity, cell membrane integrity, and cell size and function (9,11). Although its biological significance is not yet fully clear, PhA has been considered an indicator of cell membrane function (permeability, electrical properties) and of changes in the quantity and quality of soft tissues (10,11).
Factors Associated with Sarcopenia in Patients with Colorectal Cancer
Published in Nutrition and Cancer, 2018
Bianca Umbelino de Souza, Nilian Carla Silva Souza, Renata Brum Martucci, Viviane Dias Rodrigues, Nivaldo Barroso de Pinho, Maria Cristina Gonzalez, Carla Maria Avesani
Bioelectrical impedance analysis (BIA) was performed with a tetrapolar device, single frequency (50 kHz), model Quantum II (RJL Systems, Detroit, MI, USA), according to the protocol recommended by Kyle (37). BIA provides resistance (R) and reactance (Xc) values in Ohms (Ω). Phase angle (PA) was calculated with the following equation: PA (degrees) = arc tan (Xc/R) × (180/π). The principles of PA is based on changes in resistance and reactance as alternating electric current passes through tissues. A phase shift of the current is stored in the resistive compartments of cellular membranes. PA has been interpreted as an indicator of quantity of cells, cell membrane integrity, and water distribution between the intra- and extracellular spaces (38–40).
Related Knowledge Centers
- Angle of Incidence
- Brightness
- Ray
- Reflection
- Parallax
- Backscatter
- Forward Scatter
- Opposition Surge
- Phase Curve
- Angle of Incidence