A comparison of strength and muscle endurance in strength-trained and untrained women

Muscular strength and fatigability of strength-trained (ST) and untrained (UT) women were compared during a 6-min bout of maximal rhythmic exercise involving the elbow flexor muscles given at a rate of 30 contractions.min-1. Fifteen ST and 15 UT subjects, aged 18-34 years and pair-matched for body size, were tested for differences in initial strength, final strength, absolute endurance, relative endurance, and rate of fatigue. Results revealed a significant difference in initial strength, final strength, and absolute endurance in favor of ST subjects. No significant difference was found for relative endurance, and rates of fatigue were similar for both groups. It is concluded that muscular strength and endurance are enhanced in women engaged in a training program designed primarily to increase muscular strength and hypertrophy, but fatigability is not affected.     

Validity of ultrasound muscle thickness measurements for predicting leg skeletal muscle mass in healthy Japanese middle-aged and older individuals

Background

The skeletal muscle mass of the lower limb plays a role in its mobility during daily life. From the perspective of physical resources, leg muscle mass dominantly decreases after the end of the fifth decade. Therefore, an accurate estimate of the muscle mass is important for the middle-aged and older population. The present study aimed to clarify the validity of ultrasound muscle thickness (MT) measurements for predicting leg skeletal muscle mass (SM) in the healthy Japanese middle-aged and older population.

Findings

MTs at four sites of the lower limb and the bone-free lean tissue mass (LTM) of the right leg were determined using brightness-mode ultrasonography and dual-energy X-ray absorptiometry (DXA), respectively, in 44 women and 33 men, 52- to 78-years old. LTM was used as a representative variable of leg skeletal muscle mass. In the model-development group (30 women and 22 men), regression analysis produced an equation with R² and standard error of the estimate (SEE) of 0.958 and 0.3 kg, respectively: LTM (kg) = 0.01464 × (MT_SUM×L) (cm²) - 2.767, where MT_SUM is the sum of the product of MTs at four sites, and L is length of segment where MT is determined. The estimated LTM (7.0 ± 1.7 kg) did not significantly differ from the measured LTM (7.0 ± 1.7 kg), without a significant systematic error on a Bland-Altman plot. The application of this equation for the cross-validation group (14 women and 11 men) did not yield a significant difference between the measured (7.2 ± 1.6 kg) or estimated (7.2 ± 1.6 kg) LTM and systematic error.

Conclusion

The developed prediction equation may be useful for estimating the lean tissue mass of the lower extremity for the healthy Japanese middle-aged and older population.     

MR assessment of bile duct size in healthy individuals: comparison with US measurements

The purpose of the study was to determine the difference in extrahepatic bile duct (EBD) size measured by magnetic resonance (MR) compared with those measured by ultrasound (US). Changes of EBD size related to aging were analyzed too. Size of EBD was measured in 76 randomly selected healthy individuals. Three radiologists blinded to the result of other study preformed measurements by US and three different T2 weighted MR sequences. Correlation and linear regression analysis of obtained data were performed. The mean diameter of EBD measured by US was 3.17 mm and by MR was 3.14 mm on thick slab rapid acquisition with relaxation enhancement (TSE), 3.26 mm on thin section single-shot TSE (HASTE) and 3.30 mm on coronal fully rewound gradient echo (True FISP). There was no statistical difference between US and different MR sequences (p < 0.05). A trend of increase of EBD with age (0.0155 mm per year, p = 0.0954) was observed. Size of EBD highly correlated for each MR sequence with US measurement validating use of MR as a reliable method for evaluation of EBD size. This conclusion is stressed by increase of EBD size with age demonstrated by all measuring methods.     

Prolonged electrical muscle stimulation exercise improves strength and aerobic capacity in healthy sedentary adults.

This investigation evaluated training responses to prolonged electrical muscle stimulation (EMS) in sedentary adults. Fifteen healthy subjects (10 men, 5 women) with a sedentary lifestyle completed a 6-wk training program during which they completed an average of 29 1-h EMS sessions. The form of EMS used by the subjects was capable of eliciting a cardiovascular exercise response without loading the limbs or joints. It achieved this by means of inducing rapid, rhythmical contractions in the large leg muscles. A crossover study design was employed with subjects undergoing their habitual activity levels during the nontraining phase of the study. The training effect was evaluated by means of a treadmill test to determine peak aerobic capacity [peak oxygen consumption (Vo(2))], a 6-min walking distance test, and measurement of body mass index (BMI) and quadriceps muscle strength. At baseline, the mean values for peak Vo(2), 6-min walking distance, quadriceps strength, and BMI were 2.46 +/- 0.57 l/min, 493.3 +/- 36.8 m, 360.8 +/- 108.7 N, and 26.9 +/- 3.4 kg/m(2), respectively. After training, subjects demonstrated statistically significant improvements in all variables except BMI. Peak Vo(2) increased by an average of 0.24 +/- 0.16 l/min (P < 0.05), walking distance increased by 36.6 +/- 19.7 m (P < 0.005), and quadriceps strength increased by 87.5 +/- 55.9 N (P < 0.005); we did not observe a significant effect due to training on BMI (P > 0.05). These results suggest that EMS can be used in sedentary adults to improve physical fitness. It may provide a viable alternative to more conventional forms of exercise in this population.     

Steroid profiles of healthy individuals

Urine steroid profiles of healthy individuals can be divided into two groups according to greatly different excretion rates of dehydroepiandrosterone (DHEA). About 80% of the population show an excretion of DHEA in urine of just above the detection limit or less of the main androgens androsterone (A) and etiocholanolone (E). This excretion is only enhanced in psychological stress situations. The remaining 20% excrete DHEA in roughly equal amounts as A and E.While the relation of excreted steroids is rather constant, the absolute amounts may vary greatly. In contrast to the behaviour of all other steroids DHEA excretion is not in relation to other steroids. The group of “high DHEA” producing individuals in particular shows drastic changes in the excretion during a day: the DHEA excretion rapidly rises from morning until afternoon and then drops to rather low values in the resting period during the night. A recognizable DHEA production seems to be closely related to the waking period.     

Autoreactive T cells in healthy individuals

The presence of autoreactive CD4(+) T cells in the peripheral blood of healthy human subjects was investigated after removal of CD4(+)CD25(+) regulatory T cells (Treg). CD4(+) T cells that were directed against the type 1 diabetes-associated autoantigen glutamic acid decarboxylase 65, the melanocyte differentiation Ag tyrosinase, and the cancer/testis tumor Ag NY-ESO-1 were readily derived from PBMC of healthy individuals. These autoreactive T cells could be visualized, using Ag-specific class II tetramer reagents, in the peripheral blood of most individuals examined. Addition of CD4(+)CD25(+) Treg back to the CD4(+)CD25(-) population suppressed the expansion of the autoreactive T cells. Autoreactive T cells were cloned based on tetramer binding, and expressed characteristic activation markers upon self-Ag stimulation. These results show that autoreactive T cells are present in most healthy individuals and that Treg likely play an important role of keeping these autoreactive T cells in check.     

A comparison of prehension force control in young and elderly individuals

Age-related changes were investigated in the control of precision grip force during the lifting and holding of objects with slippery (silk) and nonslippery (sandpaper) surface textures. Two groups of active elderly adults comprising individuals aged 69–79 years (n = 10), and 80–93 years (n = 10) together with a group of young adults aged 18–32 years (n = 10) participated in the study. Each subject lifted a free weight (3N) during which time gripping and lifting forces were monitored. The elderly subjects, especially the individuals in the 81–93 year group, had a larger number of fluctuations in the grip force rate curve and longer force application time than the younger subjects during lifting. The effect of prior experience with one surface on the following different surface was more pronounced in the younger subjects than the elderly subjects. These results suggest a decline in programmed force production capacity with increased age. The fingers of the elderly subjects were more slippery and they exhibited a greater safety margin of the grip force while holding the object than the younger adults. The overall results demonstrated that precision grip force control capacity declines with advancing age. It is suggested that this decline is due mainly to age-related changes in skin properties, and cutaneous sensibility functions, and in part to central nervous system function.     

The effects of accentuated eccentric loading on strength, muscle hypertrophy, and neural adaptations in trained individuals

The purpose of this study was to compare the strength and neuromuscular adaptations for dynamic constant external resistance (DCER) training and dynamic accentuated external resistance (DAER) training (resistance training employing an accentuated load during eccentric actions). Male subjects active in resistance training were assigned to either a DCER training group (n = 10) or a DAER training group (n = 8) for 9 weeks. Subjects in the DCER group performed 4 sets of 10 repetitions with a load of 75% concentric 1 repetition maximum (RM). Subjects in the DAER group performed 3 sets of 10 repetitions with a concentric load of 75% of 1RM and an eccentric load of approximately 120% of concentric 1RM. Three measures reflecting adaptation of elbow flexors and extensors were recorded pretraining and posttraining: concentric 1RM, muscle cross-sectional area (CSA), and specific tension. Strength was assessed at midtraining periods. No significant changes in muscle CSA were observed in either group. Both training groups experienced significant increases in concentric 1RM and specific tension of both the elbow flexors and extensors, but compared with DCER training, DAER training produced significantly greater increases in concentric 1RM of the elbow extensors. These results suggest that, for some exercises, DAER training may be more effective than DCER training in developing strength within a 9-week training phase. However, for trained subjects, neither protocol is effective in eliciting muscle hypertrophy.     

A comparison of phasing algorithms for trios and unrelated individuals

Knowledge of haplotype phase is valuable for many analysis methods in the study of disease, population, and evolutionary genetics. Considerable research effort has been devoted to the development of statistical and computational methods that infer haplotype phase from genotype data. Although a substantial number of such methods have been developed, they have focused principally on inference from unrelated individuals, and comparisons between methods have been rather limited. Here, we describe the extension of five leading algorithms for phase inference for handling father-mother-child trios. We performed a comprehensive assessment of the methods applied to both trios and to unrelated individuals, with a focus on genomic-scale problems, using both simulated data and data from the HapMap project. The most accurate algorithm was PHASE (v2.1). For this method, the percentages of genotypes whose phase was incorrectly inferred were 0.12%, 0.05%, and 0.16% for trios from simulated data, HapMap Centre d'Etude du Polymorphisme Humain (CEPH) trios, and HapMap Yoruban trios, respectively, and 5.2% and 5.9% for unrelated individuals in simulated data and the HapMap CEPH data, respectively. The other methods considered in this work had comparable but slightly worse error rates. The error rates for trios are similar to the levels of genotyping error and missing data expected. We thus conclude that all the methods considered will provide highly accurate estimates of haplotypes when applied to trio data sets. Running times differ substantially between methods. Although it is one of the slowest methods, PHASE (v2.1) was used to infer haplotypes for the 1 million-SNP HapMap data set. Finally, we evaluated methods of estimating the value of r(2) between a pair of SNPs and concluded that all methods estimated r(2) well when the estimated value was >or=0.8.     

Multiple Epstein-Barr virus infections in healthy individuals

We employed a newly developed genotyping technique with direct representational detection of LMP-1 gene sequences to study the molecular epidemiology of Epstein-Barr virus (EBV) infection in healthy individuals. Infections with up to five different EBV genotypes were found in two of nine individuals studied. These results support the hypothesis that multiple EBV infections of healthy individuals are common. The implications for the development of an EBV vaccine are discussed.     

Anti-cytokine autoantibodies are ubiquitous in healthy individuals

Anti-cytokine autoantibodies in healthy individuals have been widely reported but the occurrence is variable and inconstant. We hypothesized that cytokine-binding in vivo may explain their variable and infrequent detection. Therefore, we focused on the detection of the cytokine-autoantibody complexes and found that anti-cytokine autoantibody to IL-2, IL-8, tumor necrosis factor-alpha, vascular endothelial growth factor and granulocyte-colony stimulating factor were present in all 15 individuals evaluated, while those to IL-3, osteopontin and macrophage-colony stimulating factor were not detected in anyone. Autoantibodies against IL-4, IL-6, IL-10, and interferon-gamma were variously detected. Thus, we discovered that anti-cytokine autoantibodies to multiple cytokines are ubiquitous in healthy individuals.     

The interaction between breathing and swallowing in healthy individuals

In this article, we aimed at investigating the interaction between breathing and swallowing patterns in normal subjects. Ten healthy volunteers were included in the study. Diaphragm EMG activity was recorded by a needle electrode inserted into the 7th or 8th intercostal space. Swallowing was monitored by submental EMG activity, and laryngeal vertical movement was recorded by using a movement sensor. A single voluntary swallow was initiated during either the inspiration or expiration phases of respiration, and changes in EMG activity were evaluated. When a swallow coincided with either inspiration or expiration, the duration of the respiratory phase was prolonged. Normal subjects were able to voluntarily swallow during inspiration. During the inspiration phase with swallowing, diaphragmatic activity did not ceased and during the expiration phase with swallowing, there was a muscle activity in the diaphragm muscle.     

EEG markers of upright posture in healthy individuals

The EEG spectral-coherence parameters were analyzed in 10 healthy individuals (mean age, 22 ± 0.67 years) at different steps of verticalization, from the lying position to the sitting and standing positions. The maximal changes in all EEG parameters were revealed when the upright posture was maintained in the absence of visual control. Under these conditions, a power increase for the fast EEG components (the ??- and ??-bands) was observed, as was an additional increase when the conditions of maintaining the upright posture were complicated. According to the results of the EEG??s coherent analysis, human verticalization revealed a specific increase for most of the EEG rhythm ranges in the right hemisphere, especially in the frontocentral and occipitoparietal regions, as well as for the interhemispheric coherences for these leads reflecting the involvement of both cortical and subcortical structures in these processes. When the posture maintenance conditions were complicated, an additional coherence increase in the fast EEG bands (the ??-rhythm) was observed in the frontal cortical regions, which was evidence of the increase in the executive functions under these conditions.     

Maximal strength testing in healthy children

Strength training has become an accepted method of conditioning in children. However, there is concern among some observers that maximal strength testing may be inappropriate or potentially injurious to children. The purpose of this study was to evaluate the safety and efficacy of 1 repetition maximum (1RM) strength testing in healthy children. Thirty-two girls and 64 boys between 6.2 and 12.3 years of age (mean age 9.3 +/- 1.6 years) volunteered to participate in this study. All subjects were screened for medical conditions that could worsen during maximal strength testing. Under close supervision by qualified professionals, each subject performed a 1RM test on 1 upper-body (standing chest press or seated chest press) and 1 lower-body (leg press or leg extension) exercise using child-size weight training machines. No injuries occurred during the study period, and the testing protocol was well tolerated by the subjects. No gender differences were found for any upper- or lower-body strength test. These findings demonstrate that healthy children can safely perform 1RM strength tests, provided that appropriate procedures are followed.     

Anthropometric parameters as predictors for iliopsoas muscle strength in healthy girls and in girls with adolescent idiopathic scoliosis

In this study iliopsoas muscle strength was measured by portable dynamometer and it was explored to what extent independent predictors (age, body weight, body height and body mass index) affect iliopsoas strength in healthy subjects and in subjects with adolescent idiopathic scoliosis. The study population was consisted of 183 girls (90 healthy girls and 93 girls with adolescent idiopathic scoliosis). Student t test analysis showed no differences in maximal voluntary isometric contraction between healthy girls and girls with scoliosis. Independent variables predicted significantly iliopsoas strength in healthy group (r=0.96, p<0.01) and in scoliosis group (r=0.94, p<0.001). Separate analysis with respect to types of scoliosis demonstrated that independent variables significantly predict iliopsoas strength in right thoracic (r=0.97, p<0.01), left thoracic (r=0.98, p=0.004), right thoracic lumbar (r=0.97, p<0.01) and left lumbar (r=0.96, p<0.01) scoliosis subgroups. In healthy girls iliopsoas strength was mostly predicted by body weight, followed by body height and body mass index. In girls with scoliosis body weigth was the strongest predictor of iliopsoas strength and was followed by curvature angle degree.