Detection of muscle gap by L-BIA in muscle injuries: clinical prognosis

Classification of myo-connective tissue injuries for severity grading and return to play prediction: A scoping review

OBJECTIVES

To conduct a systematic literature search to identify currently used classifications of acute non-contact muscle injuries in sporting adults.

DESIGNS

Scoping review.

METHODS

A systematic literature search from January 1, 2010 to April 19, 2022 of Medline and SPORTDiscus yielded 13,426 articles that were screened for eligibility. Findings from included studies were qualitatively synthesized. Classifications and their grading, as well as outcomes and definitions were extracted.

RESULTS

Twenty-four classifications were identified from the 37 included studies, most of which had low evidence study designs. Majority (57 %) of classifications were published after 2009 and were mostly developed for hamstring or other lower limb injuries. The six most cited classifications accounted for 70 % of the reports (BAMIC, modified Peetrons, Munich, Cohen, Chan and MLG-R). Outcome reporting was sparse, making it difficult to draw conclusions. Still, significant relationships between grading and time to return to play were reported for the BAMIC, modified Peetrons, Munich and Cohen classifications. Other classifications either had a very low number of reported associations, reported no associations, reported inconclusive associations, or did not report an assessment of the association. Other outcomes were poorly investigated.

CONCLUSIONS

There is no agreed-upon use of muscle classification, and no consensus on definitions and terminology. As a result, reported outcomes and their relationship to severity grading are inconsistent across studies. There is a need to improve the generalizability and applicability of existing classifications and to refine their prognostic value. High-level evidence studies are needed to resolve these inconsistencies.

Localized hamstring bioimpedance in marathon runners is related to muscle high-energy enzyme serum levels and predicts race time

Introduction: The aim was to analyze the response of serum levels of inflammatory, high-energy muscle biomarkers and hamstring localized bioimpedance (L-BIA) measurements to marathon running and to ascertain whether they correlate with each other or with race time. Methods: Blood samples and hamstrings tetra-polar L-BIA measurements from 14 Caucasian male recreational athletes at the Barcelona Marathon 2019 were collected at base line, immediately after and 48 h post-race. Serum C reactive protein (sCRP), creatinine kinase (sCK) and lactate dehydrogenase (sLDH) were determined using an AU-5800 chemistry analyzer. L-BIA was obtained at 50 kHz with a Quantum V Segmental phase-sensitive bioimpedance analyzer. Results: Median sCRP increased (4-fold) after 48 h post-race. Median sCK and sLDH levels increased immediately post-race (3-fold, 2-fold) and 48h post-race (5-fold, 1-fold). Left, right and combined hamstring reactance (Xc) and phase angle (PhA) increased immediately post-race. Xc combined hamstring pre- and immediately post-race correlated with race-time and with sCK and sLDH median levels pre-race. Xc combined hamstring pre- and immediately post-race > 15.6 Ω and 15.8 Ω, respectively, predicted the race time of 3:00:00 h. Conclusion: L-BIA reactance (Xc) is an objective direct, real time, easy, noninvasive bioelectrical parameter that may predict muscle and marathon athlete performance.

Can segmental bioelectrical impedance be used as a measure of muscle quality?

Recent works have shown bioelectrical impedance spectroscopy (BIS) may assess tissue quality. The purpose of this project was to examine associations between ultrasound echo intensity (EI) of quadriceps muscles (vastus lateralis [VL], vastus medialis [VM], vastus intermedius [VI], rectus femoris [RF]) and BIS parameters (R0, R1, C, α, fp), and if the associations are specific to individual muscles or associated with a representation of the entire quadriceps. Twenty-two participants (age: 22 ± 4 years; BMI: 25.47 ± 3.26 kg/m2) participated in all study activities. Participants had transverse ultrasound scans of each individual quadriceps muscle taken at 25, 50, and 75 % of the muscle length to generate an average EI for the VL, VM, VI, and RF, which were further averaged to generate an EI for the entire quadriceps. For BIS, participants were seated with electrodes placed on the thigh to measure the segmental quadriceps. The Cole-impedance model parameters that best fit the BIS data for each participant was used for all analyses. Pearson's correlation coefficient (r) were calculated to determine associations between muscles' EI and BIS parameters. The results suggest averaged EI of individual VL, VM, VI, RF muscles and the average EI of the segmental quadriceps were significantly related to the R0, C, α metrics of the Cole-impedance model representing quadriceps segmental tissues. This supports that segmental BIS may be an appropriate technique for rapid evaluation of segmental muscle quality.

Phase angle in localized bioimpedance measurements to assess and monitor muscle injury

Localized bioimpedance (L-BIA) measurements are an innovative method to non-invasively identify structural derangement of soft tissues, principally muscles, and fluid accumulation in response to traumatic injury. This review provides unique L-BIA data demonstrating significant relative differences between injured and contralateral non-injured regions of interest (ROI) associated with soft tissue injury. One key finding is the specific and sensitive role of reactance (Xc), measured at 50 kHz with a phase-sensitive BI instrument, to identify objective degrees of muscle injury, localized structural damage and fluid accretion, determined using magnetic resonance imaging. The predominant effect of Xc as an indicator of severity of muscle injury is highlighted in phase angle (PhA) measurements. Novel experimental models utilizing cooking-induced cell disruption, saline injection into meat specimens, and measurements of changing amounts of cells in a constant volume provide empirical evidence of the physiological correlates of series Xc as cells in water. Findings of strong associations of capacitance, computed from parallel Xc (X_CP), with whole body counting of 40-potassium and resting metabolic rate support the hypothesis that parallel Xc is a biomarker of body cell mass. These observations provide a theoretical and practical basis for a significant role of Xc, and hence PhA, to identify objectively graded muscle injury and to reliably monitor progress of treatment and return of muscle function.

Bioelectrical Impedance Vector and Creatine Phosphokinase Changes Induced by a High-Intensity Training Session in Rink Hockey Players

This study aimed to analyze anthropometric and whole-body/muscle-localized bioelectrical impedance vector analysis (BIVA) adaptations and their relation to creatine kinase (CK) as a biomarker of muscle damage in a group of seven male players in the maximum category of professional rink hockey. There were three checkpoint assessments in relation to a high-intensity training session: pre-session (PRE), post-session (POST), and 24 h-post-session (POST24H). The resistance, reactance, and impedance module were adjusted by height (R/h, Xc/h, and Z/h, respectively). The Wilcoxon signed-rank test was used to compare the data at baseline and follow-up, while Spearman correlation was used to explore the relationship between CK and the rest of the parameters. The results registered a decrease in body mass at POST (p = 0.03) and a reestablishment at POST24H (p = 0.02). Whole-body BIVA registered a significant increase in R/h between PRE–to–POST (p = 0.02) and returned to baseline values at POST24H (p = 0.02), which was expected since this parameter is related to hydration processes. Muscle-localized BIVA in the rectus femoris muscle showed an increase in both Xc/h and phase angle in POST (p = 0.04 and p = 0.03, respectively) and a decrease in Xc/h at POST24H (p = 0.02). CK correlated with R/h in the rectus femoris at all the checkpoints (PRE–to–POST: r = 0.75, p = 0.05; PRE–to–POST24H: r = 0.81, p = 0.03; POST–to–POST24H: r = 0.82, p = 0.02). Our results indicate that BIVA is a sensitive methodology to assess general and muscle-localized hydration induced by a high-intensity training session in rink hockey players. A correlation between BIVA and CK was also reported.

Effects of the COVID-19 Lockdown on Body Composition and Bioelectrical Phase Angle in Serie A Soccer Players: A Comparison of Two Consecutive Seasons

Simple Summary

In 2020, the first Italian soccer league (Serie A) was canceled due to the COVID-19 pandemic. Consequently, a detraining process was triggered in soccer players, leading coaches and sports scientists to implement alternative training strategies to prevent a remodeling in body composition. This study tested the hypothesis that male elite soccer players, when confined to their home during the coronavirus disease 2019 pandemic, will display unfavorable trends in bioelectrical and body composition parameters. The results of the present study showed that reduction in phase angle and muscle mass occurred in soccer players during the coronavirus disease 2019 pandemic lockdown. Recognizing these adverse effects of a detraining period is critical in avoiding adverse effects on body composition in soccer players. In addition, the bioelectrical phase angle has been identified as a valid predictor of muscle mass changes during the competitive soccer season. Considerably, the phase angle represents a parameter that can be measured directly through bioelectrical impedance analysis, and it is independent of predictive equations such as those that quantify muscle mass.

Abstract

The present study compared changes in body composition during the COVID-19-associated lockdown with the same period of the following season in elite soccer players. Fifteen elite male soccer players (30.5 ± 3.6 years.) underwent a bioelectrical impedance analysis (BIA) before (end of February) and after (end of May) the lockdown, which occurred during the 2019/2020 season, and at the same period during the following competitive season in 2020/2021, when restrictions were lifted. Fat and muscle mass were estimated using predictive equations, while phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) patterns were directly measured. After lockdown, fat mass remained unchanged (p > 0.05), while muscle mass (95%CI = −1.12/−0.64; ES = −2.04) and PhA (95%CI = 0.51/−0.24, ES = −1.56) decreased. A rightward displacement of the BIVA vector was also found (p < 0.001, ES = 1.50). After the same period during the regular season, FM% and muscle mass did not change (p > 0.05), while the PhA increased (95%CI = 0.01/0.22; ES = 0.63). A leftward vector displacement (p < 0.001, ES = 1.05) was also observed. The changes in muscle mass correlated with changes in PhA (“lockdown” season 2019/2020: ß = −1.128, p = 0.011; “regular” season 2020/21: ß = 1.963, p = 0.011). In conclusion, coaches and strength conditioners should monitor muscle mass in soccer players during detraining periods as this parameter appears to be mainly affected by changes in training plans.

Electrical Impedance Myography in Health and Physical Exercise: A Systematic Review and Future Perspectives

Background: Electrical impedance myography (EIM) is a non-invasive method that provides information about muscle health and changes that occur within it. EIM is based on the analysis of three impedance variables: resistance, reactance, and the phase angle. This systematic review of the literature provides a deeper insight into the scope and range of applications of EIM in health and physical exercise. The main goal of this work was to systematically review the studies on the applications of EIM in health and physical exercise in order to summarize the current knowledge on this method and outline future perspectives in this growing area, including a proposal for a research agenda. Furthermore, some basic assessment principles are provided. Methods: Systematic literature searches on PubMed, Scopus, SPORTDiscus and Web of Science up to September 2020 were conducted on any empirical investigations using localized bioimpedance devices to perform EIM within health and physical exercise contexts. The search included healthy individuals, elite soccer players with skeletal muscle injury, and subjects with primary sarcopenia. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist was used to develop the systematic review protocol. The quality and risk of bias of the studies included were assessed with the AQUA tool. Results: Nineteen eligible original articles were included in this review, which were separated into three tables according to the nature of the study. The first table includes six studies on the bioelectrical characterization of muscle. The second table includes five studies analyzing muscle changes in injured elite soccer players. The third table includes studies on the short-, medium-, and long-term bioelectrical adaptations to physical exercise. Conclusions: EIM has been used for the evaluation of the muscle condition in the clinical field over the last few years, especially in different neuromuscular diseases. It can also play an important role in other contexts as an alternative to complex and expensive methods such as magnetic resonance imaging. However, further research is needed. The main step in establishing EIM as a valid tool in the scientific field is to standardize the protocol for performing impedance assessments.

Conception of a Phantom in Agar-Agar Gel with the Same Bio-Impedance Properties as Human Quadriceps

The physiology of the patient can be reflected by various data. Serious games, using an intelligent combination, could be based on this data to adjust to the specificities of the patient. Rehabilitation would therefore be personalized to the patient. This smart suit would use dry electrodes in order to be easily usable. Before performing dry electrode validation tests on a population, it is necessary to perform preliminary tests on a phantom. Agar-Agar (AA) gel, combined with NaCl and graphite which directly impact the resistivity and reactance values of the phantom, are generally used. Depending on the part of the body simulated by the phantom, it is necessary to adapt the concentrations of NaCl and graphite in order to obtain values of physiological reactance and resistance. The anisotropy of a muscle must also be considered. Different concentrations of NaCl and graphite have been tested in order to present charts linking the concentrations to the resistance and reactance values of the AA phantom. Electrical properties similar to those of human quadriceps are achieved at a concentration of 7 g/L of NaCl and 60 g/L of graphite. These values can be used as a conversion table to develop an AA phantom with electrical properties similar to different muscles. Furthermore, an AA phantom has an anisotropy of 0° and 90°. This anisotropy corresponds to a human quadriceps, where 0° is the direction of the muscle fiber. This will allow us to study and characterize the behavior of the electrodes on an anisotropic model. Thus it can be used as a first test phase for dry electrodes in order to propose the most suitable conditions for a connected garment application.

New Frontiers of Body Composition in Sport

The body composition phenotype of an athlete displays the complex interaction among genotype, physiological and metabolic demands of a sport, diet, and physical training. Observational studies dominate the literature and describe the sport-specific physique characteristics (size, shape, and composition) of adult athletes by gender and levels of competition. Limited data reveal how body composition measurements can benefit an athlete. Thus, the objective is to identify purposeful measurements of body composition, notably fat and lean muscle masses, and determine their impact on the health and performance of athletes. Areas of interest include relationships among total and regional body composition measurements, muscle function, sport-specific performance, risk of injury, return to sport after injury, and identification of activity-induced fluid shifts. Discussion includes the application of specific uses of dual X-ray absorptiometry and bioelectrical impedance including an emphasis on the need to minimize measurement errors and standardize protocols, and highlights opportunities for future research. This focus on functional body composition can benefit the health and optimize the performance of an athlete.

Assessment of Body Composition in Athletes: A Narrative Review of Available Methods with Special Reference to Quantitative and Qualitative Bioimpedance Analysis

Body composition is acknowledged as a determinant of athletic health and performance. Its assessment is crucial in evaluating the efficiency of a diet or aspects related to the nutritional status of the athlete. Despite the methods traditionally used to assess body composition, bioelectric impedance analysis (BIA) and bioelectric impedance vector analysis (BIVA) have recently gained attention in sports, as well as in a research context. Only until recently have specific regression equations and reference tolerance ellipses for athletes become available, while specific recommendations for measurement procedures still remain scarce. Therefore, the present narrative review summarizes the current literature regarding body composition analysis, with a special focus on BIA and BIVA. The use of specific technologies and sampling frequencies is described, and recommendations for the assessment of body composition in athletes are provided. Additionally, the estimation of body composition parameters (i.e., quantitative analysis) and the interpretation of the raw bioelectrical data (i.e., qualitative analysis) are examined, highlighting the innovations now available in athletes. Lastly, it should be noted that, up until 2020, the use of BIA and BIVA in athletes failed to provide accurate results due to unspecific equations and references; however, new perspectives are now unfolding for researchers and practitioners. In light of this, BIA and especially BIVA can be utilized to monitor the nutritional status and the seasonal changes in body composition in athletes, as well as provide accurate within- and between-athlete comparisons.

Comparison of silver-plated nylon (Ag/PA66) e-textile and Ag/AgCl electrodes for bioelectrical impedance analysis (BIA)

Recently, researchers have adapted Bioelectrical Impedance Analysis (BIA) as a new approach to objectively monitor wounds. They have indicated various BIA parameters associated to specific wound types can be linked to wound healing through trend analysis relative to time. However, these studies are conducted using wet electrodes which have been identified as possessing several shortcomings, such as unstable measurements. Thus, the adaption of e-textile electrodes has become an area of interest in measuring biosignals. E-textile electrodes are known to possess a significantly large polarization impedance (Z_p) that potentially influences these biosignal measurements. In this study we aim to identify the suitability of e-textile electrodes to monitor wounds using BIA methodologies. By adapting suggested methodologies conducted in-vivo from previous studies, we used an ex-vivo model to observe the behaviour of e-textile electrodes relative to time. This was compared to common clinical wet electrodes, specifically Ag/AgCl. The objective of this study was to identify the BIA parameters that can be used to monitor wounds with e-textile electrodes. By analysing the BIA parameters relative to time, we observed the influence ofZ_pon these parameters.

Differentiation Between Tendinous, Myotendinous and Myofascial Injuries by L-BIA in Professional Football Players

Purpose

To differentiate by localized bioimpedance (L-BIA) measurements 24 h after injury, between tendinous, myotendinous junction (MTJ), and myofascial junction (MFJ) injuries, previously diagnosed by MRI exam. To evaluate by L-BIA, the severity of MTJ injuries graded from 1 to 3, and to determine the relationship between days to return to play (RTP) and L-BIA measurements.

Methods

3T MRI and tetra polar L-BIA was used to analyzed 37 muscle injuries 24 h after injury in 32 male professional football players, (23.5 ± 1.5 kg m^–2; 1.8 ± 0.1 m; 20–30 year.) between the 2016–2017 and 2017–2018 seasons. Muscle injuries were classified by The British Athletics Muscle Injury Classification (BAMIC). Percentage difference of L-BIA parameters [resistance (R), reactance (Xc), and phase angle (PA)] of the injured side were calculated considering contralateral non-injured side as the reference value.

Results

According to BAMIC classification and by MRI exam, we found tendinous (n = 4), MTJ (n = 26), and MFJ (n = 7) muscle injuries. In addition, MTJ injuries were grouped according to the severity of injury in grade 1 (n = 11), grade 2 (n = 8), and grade 3 (n = 7). Significant decrease (P < 0.01) was found in the L-BIA parameters R, Xc, and PA, in both MTJ and MFJ as well as in the different grades of MTJ injuries. In particular, in Xc (P < 0.001), which is related to muscle cell disruption. Regarding days to RTP, there was statistical significance among the three different grades of MTJ injuries (P < 0.001), especially when grade 1 was compared to grade 3 and grade 2 compared to 3.

Conclusion

L-BIA is a complementary method to imaging diagnostic techniques, such as MRI and US, to quantify MTJ and MFJ injuries. In addition, the increase in the severity of the MTJ injury resulted in higher changes of the Xc parameter and longer time to RTP.

Phase Angle from Bioelectric Impedance and Maturity-Related Factors in Adolescent Athletes: A Systematic Review

Phase angle (PhA) is a body composition (BC) parameter from bioelectrical impedance analysis that is suggested as a marker of cell integrity and general health. In adolescent athletes, PhA values are used to monitor the effects of training and competitions and seem to vary according to age, having an upward trajectory during puberty. Since adolescence is a period composed of maturation stages, the aim of this systematic review was to investigate the relationship between PhA and maturation stage in adolescent athletes. A search was conducted in PubMed/MEDLINE, BVS, Web of Science (WOS), Scopus, Science Direct, and Academic Search Complete (EBSCO) databases up to May 2020. Eligibility criteria followed the PICOS strategy and studies with healthy athletes aged 10–19 years of any level of competition were included. Six cross-sectional studies and two longitudinal studies met the inclusion criteria. Results showed that early and mature athletes have higher PhA than those who are non-matured or maturated late. Thus, PhA is influenced by the pubertal status. Considering BC is one of the factors influencing sports performance together with its growth-related changes, practitioners may use PhA values in BC analysis of adolescent athletes.

Fluid distribution and cell integrity indicators evaluated by bioelectrical impedance in university athletes: comparison between team sports and individual sports

OBJECTIVE

To compare indicators of fluid distribution and cellular integrity in university athletes through a cross-sectional study of 167 university athletes (18-35 years) who competed in team sports and individual sports.

APPROACH

Bioimpedance was used to estimate total body water (TBW), intracellular water (ICW), extracellular water (ECW), ECW/ICW ratio, impedance (Z), reactance (Xc), resistance (R), phase angle, body cell mass (BCM) and ECW/BCM ratio at a frequency of 50 kHz. X-ray absorptiometry was used to determine lean soft tissue mass and body fat. As covariables, sex, age, time of practice and type of modality were obtained by questionnaire.

MAIN RESULTS

Individual male athletes presented higher values of ECW/ICW ratio (means difference MD  =  0.006, p   =  0.020) and ECW/BCM ratio (MD  =  0.006, p   =  0.017) than team sports male athletes. Values of Z (MD  =  24.988, p   =  0.009), Xc (MD  =  3.327, p   =  0.008) and R (MD  =  24.755, p   =  0.09) were higher in male athletes practicing team sports than individual sports. Female team sports athletes presented higher values of Z (MD  =  32.029, p   =  0.015) and R (MD  =  31.987, p   =  0.015) than individual female athletes. It was concluded that ECW/ICW and ECW/BCM ratios were higher in male athletes who practiced individual sports. For the Z, R, and Xc values, the athletes in team sports presented higher values. The female athletes who practiced team sports presented higher values of Z and R than did individual female athletes.

SIGNIFICANCE

ECW/ICW and ECW/BCM ratios were higher in male athletes who practiced individual sports. For the Z, R, and Xc values, the athletes in team sports presented higher values. The female athletes who practiced team sports presented higher values of Z and R than did individual female athletes.

Fatigue-Induced Cole Electrical Impedance Model Changes of Biceps Tissue Bioimpedance

Bioimpedance, or the electrical impedance of biological tissues, describes the passive electrical properties of these materials. To simplify bioimpedance datasets, fractional-order equivalent circuit presentations are often used, with the Cole-impedance model being one of the most widely used fractional-order circuits for this purpose. In this work, bioimpedance measurements from 10 kHz to 100 kHz were collected from participants biceps tissues immediately prior and immediately post completion of a fatiguing exercise protocol. The Cole-impedance parameters that best fit these datasets were determined using numerical optimization procedures, with relative errors of within approximately ± 0.5 % and ± 2 % for the simulated resistance and reactance compared to the experimental data. Comparison between the pre and post fatigue Cole-impedance parameters shows that the R ∞ , R 1 , and f p components exhibited statistically significant mean differences as a result of the fatigue induced changes in the study participants.

Lack of agreement of in vivo raw bioimpedance measurements obtained from two single and multi-frequency bioelectrical impedance devices

BACKGROUND

It is important for highly active individuals to accurately assess their hydration level. Bioelectrical impedance (BIA) can potentially meet these needs but its validity in active individuals is not well established.

METHODS

We compared whole-body bioimpedance measurements obtained from multi-frequency bioelectrical impedance spectroscopy (BIS, Xitron 4200) at a 50 kHz frequency with those determined by a phase-sensitive single-frequency device (SF-BIA, BIA-101, RJL/Akern Systems) in two populations: active adults and elite athletes.

RESULTS

One hundred twenty-six participants, including active males involved in recreational sports (N = 25, 20-39 yr) and elite athletes (females: N = 26, 18-35 yr; males: N = 75, 18-38 yr) participated in this study. Reactance (Xc), Resistance (R), Impedance (Z), and phase angle (PhA) were obtained by BIS and SF-BIA. Small but significant differences (R: -9.91 ± 15.09 Ω; Xc: -0.97 ± 2.56 Ω; Z: -9.96 ± 15.18 Ω; PhA: 0.12 ± 0.2°) were observed between the bioimpedance equipment in all measured variables (p < 0.05) though differences were within the devices' technical error of measurements. Device-specific values were highly (p < 0.0001) correlated [R² ranged from 0.881 (Xc) to 0.833 (R)], but slopes and intercepts were different (p < 0.0001) from 1 and 0, respectively. Relatively large limits of agreement were observed for R (-40 to 21 Ω), Xc (-6 to 4 Ω), PhA (-0.4 to 0.5°), and impedance (-40 to 20 Ω).

CONCLUSION

Bioimpedance measurements from the current single- and multi-frequency devices should not be used interchangeably. The of lack of agreement between devices was observed in determining individual values of R, Xc, Z and PhA of highly active populations possibly due to methodological and biological factors.

Phase Angle as a Biomarker for Frailty and Postoperative Mortality: The BICS Study

Background Phase angle (PA) is a bioimpedance measurement that is determined lean body mass and hydration status. Patients with low PA values are more likely to be frail, sarcopenic, or malnourished. Previous work has shown that low PA predicts adverse outcomes after cardiac surgery, but the effect of PA on survival has not previously been assessed in this setting. Methods and Results The BICS (Bioimpedance in Cardiac Surgery) study recruited 277 patients undergoing major cardiac surgery at 2 university-affiliated hospitals in Montreal, QC, Canada. Bioimpedance measurements as well as frailty and nutritional assessments were performed preoperatively. The primary outcome was all-cause mortality. Secondary outcomes were 30-day mortality, postoperative morbidity, and hospital length of stay. There were 10 deaths at 1 month of follow-up and 16 deaths at 12 months of follow-up. PA was associated with age, sex, body mass index, comorbidities, and frailty, as measured by the Short Physical Performance Battery and Fried scales. After adjusting for Society of Thoracic Surgeons-predicted mortality, lower PA was associated with higher mortality at 1 month (adjusted odds ratio, 3.57 per 1° decrease in PA ; 95% confidence interval, 1.35-9.47) and at 12 months (adjusted odds ratio, 3.03 per 1° decrease in PA ; 95% confidence interval, 1.30-7.09), a higher risk of overall morbidity (adjusted hazard ratio, 2.51 per 1° decrease in PA ; 95% confidence interval, 1.32-4.75), and a longer hospital length of stay (adjusted β, 4.8 days per 1° decrease in PA ; 95% confidence interval, 1.3-8.2 days). Conclusions Low PA is associated with frailty and is predictive of mortality, morbidity, and length of stay after major cardiac surgery. Further work is needed to determine the responsiveness of PA to interventions aimed at reversing frailty.

Estimating Localized Bio-impedance with Measures from Multiple Redundant Electrode Configurations

In most bio-impedance applications, measurements are collected from a single electrode configuration though multi-electrode systems could monitor different tissue sites or serve as a source of redundancy in case of electrode malfunction. However, comparison of impedance data collected from different electrode configurations is difficult. This article proposes an approach to estimate the current tissue impedance collected from a fixed electrode configuration using measurements from different sites of the same localized tissue. Estimated impedance is calculated using the ratio between impedance values from different electrode configurations collected prior to the electrode malfunction event. This approach is validated using measurements of a human forearm collected from 3 kHz to 1 MHz collected with 4 electrode configurations over 3 days. The estimation results using this approach show maximum estimation errors of 2.3% and 16.9% for the resistance and reactance, respectively, compared to the measured impedance.

Correlations between resistance training-induced changes on phase angle and biochemical markers in older women

The main purpose of this study was to investigate the effects of 12 weeks of resistance training (RT) on phase angle (PhA), inflammatory and oxidative stress biomarkers, and to evaluate whether these RT-induced adaptations are related to PhA changes. Fifty-one older women (70.6 ± 5.1 years; 26.9 ± 4.2 kg/m² ) were randomly allocated into a training group (TG) that performed 12-week RT or a nonexercising control group (CG). The PhA (Xitron), body composition (DXA), and blood sample measurements (after a 12 hours fast) were performed before and after the intervention. The TG showed a significant (P < .05) increase in PhA (TG: +7.4±5.9% vs CG: -3.6 ± 8.8%), and interleukin-10 (IL-10; TG: +51.8 ± 71.1% vs CG: -46.6 ± 38.0%), and a decrease in tumor necrosis factor alpha (TNF-α; TG: -15.2 ± 11.1% vs CG: +6.9±17.7%), interleukin-6 (IL-6; TG: -17.9 ± 17.8% vs CG: +6.1 ± 24.8%), and C-reactive protein (CRP; TG: -24.1 ± 19.9% vs CG: +43.8 ± 31.1%). Moreover, TG upregulated catalase (TG: +11.4 ± 15.0% vs CG: -6.7 ± 10.2%). Changes in TNF-α (r = -.71), CRP (r = -.65), lower advanced oxidation protein products (r = -.55), and catalase (r = +.73) after RT were correlated with changes in PhA (P < .05). These results suggest that RT improves PhA, inflammatory and oxidative stress biomarkers, and the changes in inflammatory and oxidative damage markers are correlated with changes in PhA.