Glycoprotein Matrix Zinc Exhibits Improved Absorption: A Randomized Crossover Trial

Biotransformation of minerals via glycosylation by microorganisms such as yeast and/or probiotics yields nutrients bound to a food matrix, resulting in increased bioavailability. The purpose of this study was to compare the effects of glycoprotein matrix-bound zinc (GPM) on absorption compared to inorganic zinc oxide. Sixteen participants ingested 11 mg of zinc as either GPM™ Soy-Free Zinc (GPM, Ashland, Kearny, NJ, USA) or zinc oxide (USP). Blood samples were taken at 0 (i.e., baseline), 30, 60, 90, 120, 180, 240, 300, 360, 420, and 480 min post-ingestion. GPM zinc concentrations were significantly higher at 120 min (p = 0.02; 12.4 ± 5.1 mcg/dL), 180 min (p = 0.002; 16.8 ± 5.1 mcg/dL), and 240 min (p = 0.007; 14.6 ± 5.1 mcg/dL) in comparison to USP zinc oxide. In addition, GPM zinc significantly increased iAUC by 40% (5840 ± 2684 vs. 4183 ± 1132 mcg/dL * 480 min, p = 0.02), and Cmax values were 10% higher in GPM compared to USP (148 ± 21 mcg/dL vs. 135 ± 17.5 mcg/dL, p = 0.08). Tmax was 12% slower in GPM compared to USP (112.5 ± 38.7 min vs. 127.5 ± 43.1 min); however, differences in Tmax failed to reach statistical significance (p = 0.28). Zinc bound to a glycoprotein matrix significantly increased absorption compared to zinc oxide.

Sex-related differences in motor unit behavior are influenced by myosin heavy chain during high- but not moderate-intensity contractions

AIMS

Motor unit recruitment and firing rate patterns of the vastus lateralis (VL) have not been compared between sexes during moderate- and high-intensity contraction intensities. Additionally, the influence of fiber composition on potential sex-related differences remains unquantified.

METHODS

Eleven males and 11 females performed 40% and 70% maximal voluntary contractions (MVCs). Surface electromyographic (EMG) signals recorded from the VL were decomposed. Recruitment thresholds (RTs), MU action potential amplitudes (MUAPAMP ), initial firing rates (IFRs), mean firing rates (MFRs), and normalized EMG amplitude (N-EMGRMS ) at steady torque were analyzed. Y-intercepts and slopes were calculated for MUAPAMP , IFR, and MFR versus RT relationships. Type I myosin heavy chain isoform (MHC) was determined with muscle biopsies.

RESULTS

There were no sex-related differences in MU characteristics at 40% MVC. At 70% MVC, males exhibited greater slopes (p = 0.002) for the MUAPAMP , whereas females displayed greater slopes (p = 0.001-0.007) for the IFR and MFR versus RT relationships. N-EMGRMS at 70% MVC was greater for females (p < 0.001). Type I %MHC was greater for females (p = 0.006), and was correlated (p = 0.018-0.031) with the slopes for the MUAPAMP , IFR, and MFR versus RT relationships at 70% MVC (r = -0.599-0.585).

CONCLUSION

Both sexes exhibited an inverse relationship between MU firing rates and recruitment thresholds. However, the sex-related differences in MU recruitment and firing rate patterns and N-EMGRMS at 70% MVC were likely due to greater type I% MHC and smaller twitch forces of the higher threshold MUs for the females. Evidence is provided that muscle fiber composition may explain divergent MU behavior between sexes.

High-Intensity Cycling Training Necessitates Increased Neuromuscular Demand of the Vastus Lateralis During a Fatiguing Contraction

Purpose: To examine the effects of a 5-week continuous cycling training intervention on electromyographic amplitude (EMG_RMS)- and mechanomyographic amplitude (MMG_RMS)-torque relationships of the vastus lateralis (VL) during a prolonged contraction. Methods: Twenty-four sedentary, young adults performed maximal voluntary contractions (MVCs) and a prolonged isometric trapezoidal contraction at the same absolute 40% MVC for the knee extensors before (PRE) and after training (POST_ABS). Individual b- (slopes) and a-terms (y-intercepts) were calculated from the log-transformed electromyographic amplitude (EMG_RMS)- and mechanomyographic amplitude (MMG_RMS)-torque relationships during the increasing and decreasing segments of the trapezoid. EMG_RMS and MMG_RMS was normalized for the 45-s steady torque segment. Results: At PRE, b-terms for the EMG_RMS-torque relationships during the linearly decreasing segment were greater than the increasing segment (p < .001), and decreased from PRE to POST_ABS (p = .027). a-terms were greater during the linearly increasing than decreasing segment at PRE, while the a-terms for the linearly decreasing segment increased from PRE to POST_ABS (p = .027). For the MMG_RMS-torque relationships, b-terms during the linearly decreasing segment decreased from PRE to POST_ABS (p = .013), while a-terms increased from PRE to POST_ABS when collapsed across segments (p = .022). Steady torque EMG_RMS increased for POST_ABS (p < .001). Conclusion: Although cycling training increased aerobic endurance, incorporating resistance training may benefit athletes/individuals as the alterations in neuromuscular parameters post-training suggest a greater neural cost (EMG_RMS) and mechanical output (MMG_RMS) to complete the same pre-training fatiguing contraction.

Method of analysis influences interpretations of sex-related differences in firing rates during prolonged submaximal isometric contractions

OBJECTIVE

This study examined motor unit (MU) firing rates during a prolonged isometric contraction of the vastus lateralis (VL) for females and males.

METHODS

Surface electromyographic (sEMG) signals were recorded from the VL for eleven females and twelve males during a 45-second isometric trapezoid muscle actions at 40% of maximal voluntary contraction (MVC). For each MU, mean firing rate (MFR) was calculated for the initial and final 10-second epochs of the steady torque segment and regressed against recruitment threshold (RT, expressed as %MVC), as well as time at recruitment (T_REC, seconds). MFR was also averaged for each subject.

RESULTS

Significant differences existed across epochs for the y-intercepts (P=0.009) of the MFR vs. T_REC relationship, as well as the grouped MFR analysis (P<0.001); no differences were observed between epochs for the MFR vs. RT relationship. Significant differences existed between sexes for the grouped MFR analysis (P=0.049), but no differences were observed for the MFR vs. T_REC or MFR vs. RT relationships.

CONCLUSION

Analysis method may impact interpretation of firing rate behavior; increases in MU firing rates across a prolonged isometric contraction were observed in the MFR vs. T_REC relationship and the grouped MFR analysis.

The reliability of the slopes and y-intercepts of the motor unit firing times and action potential waveforms versus recruitment threshold relationships derived from surface electromyography signal decomposition

PURPOSE

Changes in motor unit (MU) activity pre- to post-interventions is of high interest. However, there is minimal information regarding day-to-day changes or the reliability of measuring MU activity. This study examined the reliability of relationships calculated via the MU action potential (AP) trains derived from surface electromyography signal decomposition. A comparison between reliability statistics was made between MUAP trains verified with only the reconstruct-and-test versus verification including reconstruct-and-test with spike trigger average (STA) procedures.

METHODS

Twenty-one individuals performed isometric muscle actions at 50% of maximal voluntary contraction of the first dorsal interosseous on two separate visits. MUs included for reliability analyses initially met the > 90% accuracy from the reconstruct-and-test. STA was applied as an additional exclusionary procedure. Linear regressions were applied to the firing rate and AP amplitude versus recruitment threshold relationships with and without MUs that met the STA criteria. Reliability statistics were also performed on relationships that met a strict range of recruitment thresholds. Reliability was established with intraclass correlation coefficients (ICC) along with other traditional parameters.

RESULTS

The firing rate versus recruitment threshold relationships were reliable (ICC > 0.56) and improved (ICC > 0.84) when recruitment ranges were controlled. The slopes of the MUAP amplitude versus recruitment threshold relationships were reliable (ICC > 0.78) while the y-intercepts were reliable (ICC > 0.81) once corrections were made to combat negative scores.

CONCLUSIONS

Electromyographic signal decomposition without the secondary STA verification procedures can be used to detect intervention-related changes in neural drive with confidence when recorded MU recruitment thresholds are similar across days.

Supplemental Creatine Modified With Polyethylene Glycol Effectively Loads Skeletal Muscle With Lower Doses

ABSTRACT

Fry, AC, Parra, ME, and Cabarkapa, D. Supplemental creatine modified with polyethylene glycol effectively loads skeletal muscle with lower doses. J Strength Cond Res 35(5): 1256-1261, 2021-The purpose of this study was to compare the efficacy of skeletal muscle uptake of creatine monohydrate (Cr H2O) with that of creatine bound to polyethylene glycol (Cr PEG). Healthy men (X ± SE; age = 23.5 ± 1.0 years) were divided into control (Con, n = 9, 20 g·d-1 of Cr H2O) and experimental (Exp, n = 8, 10 g·d-1 of Cr PEG) groups. Blood samples and muscle biopsies were used to determine acute gastrointestinal absorption over 5 hours and muscle cellular uptake over 5 days. Both groups exhibited significantly (p < 0.05) elevated concentrations of muscle-free Cr (M·gdw-1; Con, pre = 23.0 ± 4.2, post = 39.2 ± 2.7; Exp pre = 22.1 ± 2.9, post = 33.6 ± 3.2), total Cr (M·gdw-1, Con pre = 94.7 ± 5.4, post = 114.8 ± 7.4; Exp pre = 92.6 ± 5.4, post = 106.6 ± 8.4), which were also elevated when these values were normalized for adenosine triphosphate using molar ratios. Circulatory uptake of Cr was significantly different between the groups, with blood concentrations (mg·dL-1) for the Con group peaking at 2 hours post-ingestion (25.99 ± 2.96), whereas the concentrations for the Exp group were lower and were still rising at 5 hours (4.05 ± 0.87). The integrated area under the curve for the 5-hour postingestion period was 7-fold greater for the Con group. Although total Cr ingested over the 5 days supplementation period was less for the Cr PEG group, skeletal muscle uptake of Cr PEG was similar to Cr H2O. Based on circulating Cr concentrations, it seems that Cr PEG is cleared more slowly from the gastrointestinal tract. Thus, lower dosages of Cr may be ingested while maintaining optimal loading kinetics.

Differences in the firing rate versus recruitment threshold relationships of the vastus lateralis in children ages 7-10 years and adults

Motor unit (MU) firing rates of the vastus lateralis in children and adults were examined. Seven healthy adult males (mean ± SD, age = 21 ± 2.6 yrs) and six healthy male children (mean ± SD age = 8.8 ± 1.7) volunteered. Surface electromyography (EMG) signals were recorded from 20% and 60% maximal voluntary contractions (MVC). Surface EMG signals were decomposed into firing events of individual MUs and slopes and y-intercepts were calculated for the mean firing rate (MFR, pps) at steady torque vs. recruitment thresholds (RT) relationships for each subject. Muscle cross-sectional area (mCSA) was measured, via ultrasonography, with specific torque calculated (MVC/mCSA). Adults possessed greater mCSA (p = .002; children = 11.5 ± 2.1 cm²; adults = 31.80 ± 12.15 cm²) and greater specific torque (p = .018; children = 4.63 ± 1.4 Nm/cm²; adults = 7.1 ± 1.8 Nm/cm²) compared to children. The y-intercepts were significantly (p < .001) greater during the 60% (28.91 ± 4.56 pps) than the 20% MVC (23.5 ± 4.9 pps) collapsed across groups while the children had significantly (p = .036) lower y-intercepts (23.9 ± 5.4 pps) than the adults (28.2 ± 4.8 pps) when collapsed across intensities. Slopes of the MFR vs RT relationships were greater for the 60% (-0.342 ± 0.127 pps/%MVC) contraction than the 20% (-0.50 ± 0.159 pps/%MVC) MVC when collapsed across groups. Adults had greater firing rates regardless of recruitment threshold than children. This may be due to lower recruitment potential and overall excitation to the motoneuron pool of children as indicated with differences in specific torque and/or differences in antagonist co-activation.

Measuring the accuracies of motor unit firing times and action potential waveforms derived from surface electromyographic decomposition

This study included spike trigger averaging (STA) procedures to examine the acceptability of the Precision Decomposition (PD) III derived motor unit action potential (MUAP) trains that met the >90% accuracy criteria from the reconstruct-and-test. MUs met the >90% accuracy criteria from the reconstruct-and-test with STA procedures then applied. Y-intercepts and slopes were calculated for the firing rate- and MUAP amplitude-recruitment threshold relationships. Gaussian noise (1% of the SD of the mean interspike interval) was added to the firing times with the changes in MUAPs quantified. A total of 455 MUs were decomposed with 155 MUs removed as a result of the reconstruct-and-test. Five additional MUs were excluded via the STA criteria. The MUAP waveforms deteriorated with the inclusion of Gaussian noise. There were differences in the derived action potentials amplitudes of higher-threshold MUs between the PD III algorithm and the STA procedure. There was excellent agreement among the slopes and y-intercepts between the relationships that included or excluded MUs that did not meet the STA criteria. There was good agreement between the MUAP amplitude-recruitment threshold relationships derived from the PD III and STA procedure. The addition of the STA procedures did not alter the MU-derived relationships.

Identification of Plasmodium falciparum histidine-rich protein 2 in the plasma of humans with malaria

Plasmodium falciparum histidine-rich protein 2 (PfHRP-2) is a water-soluble protein released from parasitized erythrocytes into in vitro culture supernatants. This study sought to determine whether PfHRP-2 could be detected in the plasma of humans with P. falciparum malaria. A monoclonal antibody (1E1) is described that binds to PfHRP-2. By using monoclonal antibody 1E1, PfHRP-2 was identified by Western blot (immunoblot) analysis in the plasma of 37 of 39 (95%) patients experiencing either a first or repeat episodes of P. falciparum malaria and by dot blot analysis in the plasma of 40 of 41 patients tested. PfHRP-2 was not detected in 30 control, uninfected subjects. The current demonstration of PfHRP-2 in plasma, plus the fact that it is a structurally well-characterized molecule present in all natural isolates of P. falciparum tested, makes PfHRP-2 of interest for its potential effects on the host immune system and as an antigen for specific diagnosis of malaria.

[A comparison of the life habits of abstemious patients and drinkers]

The life habits of 358 males abstemious (ABS) and 248 male risky or with harmful alcohol consumption (BRD) are compared; selected from the patients attending to a clinic of familiar medicine, of the Instituto Mexicano del Seguro Social (IMSS) and to General Hospital of the Secretaria de Salubridad y Asistencia (SSA). BRD are different from ABS because of a sedentary life, tobacco consumption, higher frequency of other drug use, poor nutrition, over weighted and poor physical condition. The difference between ABS and BRD is not only due to the alcohol consumption and related problems, but two groups of individuals with different ways of life. The present paper shows the first Mexican results of an International Multicentric Investigation coordinated by World Health Organization (WHO).