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

Sport-related muscle injury classifications are based basically on imaging criteria such as ultrasound (US) and magnetic resonance imaging (MRI) without consensus because of a lack of clinical prognostics for return-to-play (RTP), which is conditioned upon the severity of the injury, and this in turn with the muscle gap (muscular fibers retraction). Recently, Futbol Club Barcelona's medical department proposed a new muscle injury classification in which muscle gap plays an important role, with the drawback that it is not always possible to identify by MRI. Localized bioimpedance measurement (L-BIA) has emerged as a non-invasive technique for supporting US and MRI to quantify the disrupted soft tissue structure in injured muscles. OBJECTIVE: To correlate the severity of the injury according to the gap with the RTP, through the percent of change in resistance (R), reactance (Xc) and phase-angle (PA) by L-BIA measurements in 22 muscle injuries. MAIN RESULTS: After grouping the data according to the muscle gap (by MRI exam), there were significant differences in R between grade 1 and grade 2f (myotendinous or myofascial muscle injury with feather-like appearance), as well as between grade 2f and grade 2g (myotendinous or myofascial muscle injury with feather and gap). The Xc and PA values decrease significantly between each grade (i.e. 1 versus 2f, 1 versus 2g and 2f versus 2g). In addition, the severity of the muscle gap adversely affected the RTP with significant differences observed between 1 and 2g as well as between 2f and 2g. SIGNIFICANCE: These results show that L-BIA could aid MRI and US in identifying the severity of an injured muscle according to muscle gap and therefore to accurately predict the RTP.

Different displacement of bioimpedance vector due to Ag/AgCl electrode effect.

BACKGROUND/OBJECTIVES: Bioelectrical impedance vector analysis (BIVA) is increasingly used in clinical research to assess soft tissue hydration. It is known that physical characteristics of electrodes, such as low intrinsic impedance, low electrode/skin contact impedance and type of gel, affect the reliability of noninvasive bioimpedance assessments. The aim of this study was to determine the effect of intrinsic impedance of electrode on the bioimpedance vector displacement in RXc graph. SUBJECTS/METHODS: The intrinsic impedance is measured in nine pregelled disposable Ag/AgCl electrodes usually used for bioimpedance measures. The BIVA method is performed on 35 healthy volunteers using a 50 kHz phase-sensitive bioimpedance analyzer (BIA 101 Anniversary) with the lowest intrinsic impedance electrode and highest. The individual bioimpedance vector is plotted on the bivariate normal interval of reference population. The differences in the mean bioimpedance vectors obtained with each electrode are plotted, with their 95% confidence ellipses, on the dRXc graph. The paired one-sample Hotelling's T2-test is used to compare the differences of the mean bioimpedance vectors. RESULTS: We found large variability in intrinsic resistance (11-665 Ω) and reactance (0.25-2.5 Ω) values of the electrodes analyzed and significant displacement (P<0.05) of bioimpedance vector positions in healthy adults according to the paired one-sample Hotelling's T2-test. CONCLUSIONS: A robust study of all physical characteristics of commercial Ag/AgCl electrodes is necessary to reach consensus on pregelled Ag/AgCl electrodes valid for bioimpedance measurement. This information will enable BIVA users to avoid systemic errors when performing BIVA assessments, specifically when these measurements are used for clinical interpretations.

Effects of muscle injury severity on localized bioimpedance measurements.

Muscle injuries in the lower limb are common among professional football players. Classification is made according to severity and is diagnosed with radiological assessment as: grade I (minor strain or minor injury), grade II (partial rupture, moderate injury) and grade III (complete rupture, severe injury). Tetrapolar localized bioimpedance analysis (BIA) at 50 kHz made with a phase-sensitive analyzer was used to assess damage to the integrity of muscle structures and the fluid accumulation 24 h after injury in 21 injuries in the quadriceps, hamstring and calf, and was diagnosed with magnetic resonance imaging (MRI). The aim of this study was to identify the pattern of change in BIA variables as indicators of fluid [resistance (R)] and cell structure integrity [reactance (Xc) and phase angle (PA)] according to the severity of the MRI-defined injury. The % difference compared to the non-injured contralateral muscle also measured 24-h after injury of R, Xc and PA were respectively: grade I (n = 11; -10.4, -17.5 and -9.0%), grade II (n = 8; -18.4, -32.9 and -16.6%) and grade III (n = 2; -14.1, -52.9 and -43.1%), showing a greater significant decrease in Xc (p < 0.001). The greatest relative changes were in grade III injuries. However, decreases in R, that indicate fluid distribution, were not proportional to the severity of the injury. Disruption of the muscle structure, demonstrated by the localized determination of Xc, increased with the severity of muscle injury. The most significant changes 24 h after injury was the sizeable decrease in Xc that indicates a pattern of disrupted soft tissue structure, proportional to the severity of the injury.

Changes in hydration, body-cell mass and endurance performance of professional soccer players through a competitive season.

AIM: The aim of this paper was to determine changes of the bioelectrical impedance vector (BIVA) throughout a soccer season and to ascertain whether vector changes are associated with endurance performance changes. METHODS: Eighteen professional male soccer players (age=21.8±3.0 years, height=1.8±0.07 m, mass=7.2±6.5 kg) participated in the study. BIVA was conducted serially on 8 occasions throughout one soccer season. Endurance performance (Yo-Yo test) was assessed before the first training session of the preseason training, after the pre-season training and at the end of the season. RESULTS: Vector length shortened (p<0.05) during pre-season training and was associated with improvements in endurance performance (r=0.569, p=0.034). Vector length and phase-angle increased at mid-season compared to post pre-season training (p<0.05). Vector length at end-season was lower compared to mid-season (p<0.05). No further changes in endurance performance occurred. CONCLUSION: Bioimpedance vector variations from baseline indicate that fluid-gains occur during the pre-season training, possibly due to plasma volume expansion and enhanced glycogen storage, accompanied by improvements in endurance performance. The vector migration and the increase in phase angle during the competitive season indicate fluid-loss and an increase in body cell mass without effects on performance. At the very end of the season, when training volume and intensity are reduced, body fluid increases again.

Localized BIA identifies structural and pathophysiological changes in soft tissue after post-traumatic injuries in soccer players.

Localized bioimpedance (BIA) was measured with a single frequency phase-sensitive analyzer at 50 kHz in three post-traumatic types of injuries on four professional soccer players: (1) myositis ossificans, (2) intramuscular seroma and (3) trochanteric (hip) bursitis. Normal reference value (no injury) was obtained from the contra lateral not injured limb at a mirror-like location of the injury. The relative variations resistance (R) and reactance (Xc) at the time of injury was confronted with the not injured values. Relative variations between acute measurements and post medication ones on intramuscular seroma and bursitis have been computed. In intramuscular seroma and trochanteric bursitis we have obtained a percent of change between injury data and after medical intervention. On myositis ossificans, localized BIA showed a 7-8 % decrease in Xc whereas the percent of change of R was negligible (1 %). These percent of changes are in concordance with histological evidence. In the case of a presence of seroma or the lower thigh and trochanteric bursitis, the soft tissue cavity accumulates fluid. Post-injury localized BIA, relative with respect to non-injured side, confirmed sizeable soft tissue destruction evidenced by 50 % decrease of Xc and 24-31 % decrease of R due to interstitial fluid accumulation. Once the seroma and the blood in the bursitis was removed the localized the immediate post-injury BIA parameters increased as follows: a) intramuscular seroma + 10 % on R and + 74 % of Xc; b) trochanteric bursitis + 20 % of R and +24 % of Xc. Localized BIA other than classifying soft tissue injuries, can be useful to understand the pathophysiology and structural impairments of other kind of injuries and to understand their behavior.

Localized bioimpedance to assess muscle injury.

Injuries to lower limb muscles are common among football players. Localized bioimpedance analysis (BIA) utilizes electrical measurements to assess soft tissue hydration and cell membrane integrity non-invasively. This study reports the effects of the severity of muscle injury and recovery on BIA variables. We made serial tetra-polar, phase-sensitive 50 kHz localized BIA measurements of quadriceps, hamstring and calf muscles of three male football players before and after injury and during recovery until return-to-play, to determine changes in BIA variables (resistance (R), reactance (Xc) and phase angle (PA)) in different degrees of muscle injury. Compared to non-injury values, R, Xc and PA decreased with increasing muscle injury severity: grade III (23.1%, 45.1% and 27.6%), grade II (20.6%, 31.6% and 13.3%) and grade I (11.9%, 23.5% and 12.1%). These findings indicate that decreases in R reflect localized fluid accumulation, and reductions in Xc and PA highlight disruption of cellular membrane integrity and injury. Localized BIA measurements of muscle groups enable the practical detection of soft tissue injury and its severity.

Evolution of bioimpedance: a circuitous journey from estimation of physiological function to assessment of body composition and a return to clinical research.

BACKGROUND/OBJECTIVES: Bioimpedance is the collective term that describes safe, non-invasive methods to measure the electrical responses to the introduction of a low-level, alternating current into a living organism, and the biophysical models to estimate body composition from bioelectrical measurements. Although bioimpedance techniques have been used for more than 100 years to monitor assorted biological components, the desire to translate bioelectrical measurements into physiological variables advanced the creation of empirical prediction models that produced inconsistent results. SUBJECTS/METHODS: This paper succinctly reviews the origin, and critically evaluates the conceptual models and the implementation of bioimpedance in clinical research, including indirect assessment of assorted physiological functions and body composition (fluid volumes and fat-free mass), classification of hydration, regional fluid accumulation, prognosis in disease and wound healing. RESULTS: Despite widespread and mounting interest in the use of bioimpedance to characterise body structure and function, most experimental findings reveal the limitations of existing physical models and reliance on multiple regression models for use in assessments of an individual. CONCLUSIONS: Contemporary applications of bioimpedance emphasise the value of bioimpedance variables per se in some novel biomedical applications with the objective of identifying opportunities for future outcome-based research.

Evaluation of the Megaduct sweat collector for mineral analysis.

Accurate measurement of sweat mineral loss is important for whole body mineral balance estimates and dietary reference intake formulation. Currently, common localized sweat collection methods such as the pouch and patch techniques may be limited by skin encapsulation and/or hidromeiosis, which may alter sweat mineral concentrations. The design of the newly developed Megaduct sweat collector may avoid these possible limitations. Therefore, the purpose of this study was to evaluate the utility of the Megaduct sweat collector for mineral analysis. Megaduct sweat collectors were affixed to ten volunteers on the final day of a heat acclimation protocol; collection time, sweat volume, and mineral concentrations of calcium, copper, iron, potassium, sodium, and zinc were measured. Megaduct filling required a collection period of 62 ± 3 min due to a small collection surface (22.1 cm(2)). The mineral content of the sweat was 0.3 ± 0.1 mmol L(-1), 1.5 ± 1.5 µmol L(-1), 8.5 ± 2.1 mmol L(-1), 43.2 ± 15.0 mmol L(-1), and 10.1 ± 5.7 µmol L(-1) for Ca, Cu, K, Na, and Zn, respectively. The Megaduct sweat collector appears to avoid skin encapsulation and hidromeiosis, and captures sweat with similar mineral concentrations as reported in the literature for pouches. However, the filling time of the Megaduct (>60 min) may not capture possible changes in sweat mineral concentrations that are documented to occur in as little as 15 to 30 min.

Update on the relationship between magnesium and exercise.

Magnesium is involved in numerous processes that affect muscle function including oxygen uptake, energy production and electrolyte balance. Thus, the relationship between magnesium status and exercise has received significant research attention. This research has shown that exercise induces a redistribution of magnesium in the body to accommodate metabolic needs. There is evidence that marginal magnesium deficiency impairs exercise performance and amplifies the negative consequences of strenuous exercise (e.g., oxidative stress). Strenuous exercise apparently increases urinary and sweat losses that may increase magnesium requirements by 10-20%. Based on dietary surveys and recent human experiments, a magnesium intake less than 260 mg/day for male and 220 mg/day for female athletes may result in a magnesium-deficient status. Recent surveys also indicate that a significant number of individuals routinely have magnesium intakes that may result in a deficient status. Athletes participating in sports requiring weight control (e.g., wrestling, gymnastics) are apparently especially vulnerable to an inadequate magnesium status. Magnesium supplementation or increased dietary intake of magnesium will have beneficial effects on exercise performance in magnesium-deficient individuals. Magnesium supplementation of physically active individuals with adequate magnesium status has not been shown to enhance physical performance. An activity-linked RNI or RDA based on long-term balance data from well-controlled human experiments should be determined so that physically active individuals can ascertain whether they have a magnesium intake that may affect their performance or enhance their risk to adverse health consequences (e.g., immunosuppression, oxidative damage, arrhythmias).

Regional bioelectrical impedance analysis: applications in health and medicine.

Although skeletal muscle mass represents the largest organ in the human body and plays a critical role in energy metabolism, its routine assessment has been limited by the availability of practical methods. This review critically evaluates traditional and new applications of the four-electrode bioelectrical impedance method in determining regional skeletal muscle mass or volume and assessing muscle function in health and disease. It also describes opportunities for research in the use of regional bioelectrical impedance.

Body composition estimates from NHANES III bioelectrical impedance data.

BACKGROUND: Body composition estimates for the US population are important in order to analyze trends in obesity, sarcopenia and other weight-related health conditions. National body composition estimates have not previously been available. OBJECTIVE: To use transformed bioelectrical impedance analysis (BIA) data in sex-specific, multicomponent model-derived prediction formulae, to estimate total body water (TBW), fat-free mass (FFM), total body fat (TBF), and percentage body fat (%BF) using a nationally representative sample of the US population. DESIGN: Anthropometric and BIA data were from the third National Health and Nutrition Examination Survey (NHANES III; 1988-1994). Sex-specific BIA prediction equations developed for this study were applied to the NHANES data, and mean values for TBW, FFM, TBF and %BF were estimated for selected age, sex and racial-ethnic groups. RESULTS: Among the non-Hispanic white, non-Hispanic black, and Mexican-American participants aged 12-80 y examined in NHANES III, 15 912 had data available for weight, stature and BIA resistance measures. Males had higher mean TBW and FFM than did females, regardless of age or racial-ethnic status. Mean TBW and FFM increased from the adolescent years to mid-adulthood and declined in older adult age groups. Females had higher mean TBF and %BF estimates than males at each age group. Mean TBF also increased with older age groups to approximately 60 y of age after which it decreased. CONCLUSIONS: These mean body composition estimates for TBW, FFM, TBF and %BF based upon NHANES III BIA data provide a descriptive reference for non-Hispanic whites, non-Hispanic blacks and Mexican Americans in the US population.

Validation of dual x-ray absorptiometry for body-composition assessment of rats exposed to dietary stressors.

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure soft-tissue composition of laboratory rats with altered body composition associated with nutritional perturbations is lacking. We compared DXA determinations made in prone and supine positions with measurements of chemical composition of 49 male, weanling Sprague-Dawley rats that were fed the basal AIN-93 growth diet, were fed the basal diet modified to contain 30% fat, were fasted for 2 d, were limit fed 6 g of the basal diet daily for 1 wk, or were treated with furosemide (10 mg/kg intraperitoneally 2 h before DXA). DXA produced similar estimates of body mass and soft-tissue composition in the prone and supine positions. DXA estimates of body composition were significantly correlated with reference composition values (R(2) = 0.371-0.999). DXA discriminated treatment effects on body mass, fat-free and bone-free mass, fat mass, and body fatness; it significantly underestimated body mass (1% to 2%) and fat-free and bone-free mass (3%) and significantly overestimated fat mass and body fatness (3% to 25%). The greatest errors occurred in treatment groups in which body mass was diminished and body hydration was decreased. These findings suggest that DXA can determine small changes in fat-free, bone-free mass in response to obesity and weight loss. Errors in DXA determination of fat mass and body fatness associated with extra corporeal fluid and dehydration indicate the need for revision of calculation algorithms for soft-tissue determination.

Interactions among dietary fat, mineral status, and performance of endurance athletes: a case study.

In a pilot study, performance measures and mineral metabolism were assessed in 3 male endurance cyclists who consumed isoenergetic, isonitrogenous diets for 28-day periods in a randomized, crossover design in which dietary carbohydrate, polyunsaturated, or saturated fat contributed about 50% of daily energy intake. Peak aerobic capacity [62 ml/(kg á min)] was unaffected by diet. Endurance capacity at 70-75% peak aerobic capacity decreased with the polyunsaturated fat diet. Copper retention tended to be positive only with saturated fat. Less iron and zinc were retained (intake - losses), and fecal losses of these minerals increased with the polyunsaturated fat. Blood biochemical measures of trace element nutritional status were unaffected by diet, except serum ferritin, which tended to decrease during consumption of the polyunsaturated fat diet. These preliminary results suggest that diets high in polyunsaturated fat, particularly linoleic acid, impair absorption and utilization of iron and zinc, and possibly magnesium, and may reduce endurance performance.

Use of bioimpedance spectroscopy to estimate body water distribution in rats fed high dietary sulfur amino acids.

The effect of dietary sulfur amino acids on bioelectric properties was studied in rats by using bioimpedance spectroscopy. Weanling rats were assigned to one of 12 groups in a factorially arranged experiment with dietary variables of supplemental sulfur amino acid (none, 10 g DL-methionine/kg or 10 g DL-homocystine/kg), pyridoxine hydrochloride (0 or 7.5 mg/kg) and nickel (0 or 1 mg/kg). After 9 wk of feeding, 20-h urine specimens were collected from food-deprived rats for measurements of creatinine, and then bioimpedance was measured with multifrequency (Hydra ECF/ICF 4200) and single-frequency (RJL Systems model 101) analyzers. Urinary creatinine excretion was measured by intracellular water (ICW), total body solid and urinary volume (R2 = 0.675). Extracellular water (ECW) did not add significantly to the model. Rats fed methionine had significantly lower total body water, ICW and ECW than rats fed no supplemental sulfur amino acid. Rats fed homocystine had significantly lower ECW and a significantly higher ratio of ICW to ECW. Rats fed methionine or homocystine had significantly lower capacitance corrected for body length and ICW than those fed no supplemental sulfur amino acids. These results suggest that dietary homocystine changes the distribution of body water and that sulfur amino acids can affect membrane porosity and/or membrane thickness.

The effects of magnesium supplementation on exercise performance.

PURPOSE: To determine the effects of magnesium (Mg2+) supplementation on performance and recovery in physically active women using the sensitive and recently advanced measure of ionic Mg2+ (iMg). METHODS: Participants (N = 121) were screened for [iMg] in plasma, with 44 (36.4%) exhibiting [iMg] below the normal range of 0.53-0.67 mmol.L-1 (4). Thirty-two subjects (21 +/- 3 yr) representing a broad range of [iMg] (0.54 +/- 0.04 mmol.L-1) completed the main 14-wk study. At baseline, participants submitted to a resting blood pressure measurement, and they completed both an anaerobic treadmill test and an incremental (aerobic) treadmill test. For the latter, values for workload, oxygen uptake, and heart rate were obtained at both anaerobic threshold and maximal effort. Blood samples for iMg, total serum Mg2+ (TMg), erythrocyte Mg2+ (EMg), Ca2+, K+, Na+, hemoglobin, hematocrit, lactate, and glucose were also collected pretest, and 4, 10, 30 min, and 24 h posttest. Subjects received 212 mg.d-1 Mg oxide or placebo in a double-blind fashion and were retested after 4 wk. After a 6-wk washout period, the testing was repeated with a treatment crossover. RESULTS: Ionic Mg2+ increased with Mg2+ treatment versus placebo (P < 0.05); however, performance and recovery indices were not significantly affected. CONCLUSION: Four weeks of 212 mg.d-1 Mg oxide supplementation improves resting [iMg] levels but not performance or recovery in physically active women.

Magnesium, zinc, and chromium nutrition and athletic performance.

Magnesium, zinc and chromium are mineral elements required in modest amounts for health and optimal performance. Accumulating evidence supports the hypothesis that magnesium and zinc play significant roles in promoting strength and cardiorespiratory function in healthy persons and athletes. Differences in study designs, however, limit conclusions about recommendations for intakes of magnesium and zinc needed for optimal performance and function. The role of chromium in supporting performance is not well established. There is a compelling need to confirm and extend findings of beneficial effects of magnesium and zinc function and performance of humans. Suggestions for an experimental model and specific topics for research to advance knowledge of mineral nutrition to promote attainment of genetic potential for optimal performance are provided.

Magnesium, zinc, and chromium nutriture and physical activity.

Magnesium, zinc, and chromium are mineral elements required in modest amounts to maintain health and optimal physiologic function. For physically active persons, adequate amounts of these micronutrients are needed in the diet to ensure the capacity for increased energy expenditure and work performance. Most physically active individuals consume diets that provide amounts of magnesium and zinc sufficient to meet population standards. Women tend to consume less of these minerals than is recommended, in part because they eat less food than men. Inadequate intakes of magnesium and zinc have been reported for participants in activities requiring restriction of body weight. Dietary chromium is difficult to estimate because of a lack of appropriate reference databases. Acute, intense activity results in short-term increases in both urine and sweat losses of minerals that apparently diminish during recovery in the days after exercise. Supplemental magnesium and zinc apparently improve strength and muscle metabolism. However, evidence is lacking as to whether these observations relate to impaired nutritional status or a pharmacologic effect. Chromium supplementation of young men and women does not promote muscle accretion, fat loss, or gains in strength. Physically active individuals with concerns about meeting guidelines for nutrient intake should be counseled to select and consume foods with high nutrient densities rather than to rely on nutritional supplements. The indiscriminate use of mineral supplements can adversely affect physiologic function and impair health.

Assessing regional muscle mass with segmental measurements of bioelectrical impedance in obese women during weight loss.

Tetrapolar bioelectrical impedance analysis (BIA) offers the possibility of determining the bioconductor volume in discrete segments of the body, because the resistivities of bone, fat, and skeletal muscle differ considerably. We tested this hypothesis by measuring BIA and anthropometry of defined segments of the right thighs of women before and during a controlled weight-loss program. Eight women, aged 22 to 32 years, with a body mass index of 37.8 +/- 1.6 (mean +/- SE) kg/m2 underwent determinations of body composition with dual-energy X-ray absorptiometry (DXA) and regional BIA measurements (800 microA at 50 kHz) before the program, and monthly thereafter for four months during weight loss. BIA measurements were made with spot-detector electrodes positioned 10 cm apart on the anterior of the thigh, and source electrodes placed on the right hand and foot. The physical volume of the thigh segment decreased by 29 +/- 3% (p < 0.0001), with a modest change in its electrical volume (8 +/- 0.2%; p < 0.05) during weight loss. Muscle (181 +/- 49 g; p < 0.05) and fat mass (702 +/- 95 g; p < 0.001) also declined. The electrical or bioconductor volume correlated with DXA determinations of muscle mass (r = 0.91, p < 0.0001), whereas physical volume correlated with fat mass (r = 0.95, p < 0.0001). These findings support the hypothesis that BIA is a valid method to assess regional muscle mass in humans.