The lability of the human background alpha rhythm under functional loads

Some characteristics of electroencephalographic reaction (alpha frequency, whole alpha range power spectrum and alpha index) have been studied. In the first series the indifferent single, rhythmic and complex stimuli were presented to the test subjects, in another series a conditioned motor reflex was elaborated, in the third series the test subjects rhythmically reproduced fixed temporal interval. It has been shown that the functional loads lead to higher alpha frequency. The alpha rhythm frequency was higher in subjects verbally underestimating and reproducing intervals with some delay than in ones overestimating intervals and reproducing them in advance. It has been suggested that alpha rhythm instability is due to reorganization processes in neuronal complexes of different lability.     

Variations in electroencephalographic alpha activity under conditions of differential lighting and auditory feedback

The electroencephalographic alpha activity of 13 college students was monitored under conditions of darkness or dim light for six sessions, and for a seventh under the opposite condition. Auditory feedback was given for the presence of alpha activity during a 5-min orientation period, and then during ten 2-min trial periods. The results indicated that: (1) alpha production in the presence of feedback did not exceed initial eyes-closed base line production; (2) introducing feedback immediately enhances alpha activity, rather than increasing production gradually; (3) under certain circumstances, dim light is sufficient to suppress alpha; and (4) after many sessions of alpha production in darkness, subjects maintain a given amount of alpha even when visual stimulation is present.     

Factors affecting postural stability of healthy young adults

The objective of this paper was to examine the relationship between body balancing functions and body characteristics, motor abilities and reaction time. Subjects were 33 university students and 11 professional basketball players sorted into four groups of athletic and non-athletic women and men. Each group consisted of eleven subjects. The body height, weight was measured and the body mass index (BMI) calculated. A bioelectrical device computed the body fat (%). Static and dynamic motor tests, as well as static and dynamic balance tests were used. The reaction time (RT) to sound and light stimuli was measured. The regression analysis of the data revealed significant linear relationship between the amplitude of body sways (BS) and BMI in all groups. Also high correlation was found between back muscle strength and BS in all groups except the non-athletic women. Negative correlation was found between endurance capacity and BS in basketball players, i.e. at higher endurance capacity smaller amplitude BS occurred (r = -0.620, p < 0.04). The RT values showed significant correlations with BS only in the basketball players (r = 0.620, p < 0.04). It is concluded that increase in BMI, back muscle strength and endurance capacity is associated with better postural stability. Some motor abilities (hip flexibility, vertical jumping) show no significant correlations with body balancing, while other motor performances (static hanging) and RT values correlate well with BS only in the well-trained elite basketball players.     

Persistence of social jetlag and sleep disruption in healthy young adults

Sleep disruption has been associated with increased risks for several major chronic diseases that develop over decades. Differences in sleep/wake timing between work and free days can result in the development of social jetlag (SJL), a chronic misalignment between a person’s preferred sleep/wake schedule and sleep/wake timing imposed by his/her work schedule. Only a few studies have examined the persistence of SJL or sleep disruption over time. This prospective investigation examined SJL and sleep characteristics over a 2-year period to evaluate whether SJL or poor sleep were chronic conditions during the study period. SJL and sleep measures (total sleep time [TST], sleep onset latency [SOL], wake after sleep onset [WASO]), and sleep efficiency [SE]), were derived from armband monitoring among 390 healthy men and women 21–35 years old. Participants wore the armband for periods of 4–10 days at 6-month intervals during the follow-up period (N = 1431 repeated observations).

The consistency of SJL or sleep disruption over time was analyzed using generalized linear mixed models (GLMMs) for repeated measures. Repeated measures latent class analysis (RMLCA) was then used to identify subgroups among the study participants with different sleep trajectories over time. Individuals in each latent group were compared using GLMMs to identify personal characteristics that differed among the latent groups.

Minor changes in mean SJL, chronotype, or TST were observed over time, whereas no statistically significant changes in SOL, WASO, or SE were observed during the study period. The RMLCA identified two groups of SJL that remained consistent throughout the study (low SJL, mean ± SE: 0.4 ± 0.04 h, 42% of the study population; and high SJL, 1.4 ± 0.03 h, 58%). Those in the SJL group with higher values tended to be employed and have an evening chronotype.

Similarly, two distinct subgroups were observed for SOL, WASO, and SE; one group with a pattern suggesting disrupted sleep over time, and another with a consistently normal sleep pattern. Analyses of TST identified three latent groups with relatively short (5.6 ± 1.0 h, 21%), intermediate (6.5 ± 1.0 h, 44%), and long (7.3 ± 1.0 h, 36%) sleep durations, all with temporally stable, linear trajectories. The results from this study suggest that sleep disturbances among young adults can persist over a 2 year period. Latent groups with poor sleep tended to be male, African American, lower income, and have an evening chronotype relative to those with more normal sleep characteristics. Characterizing the persistence of sleep disruption over time and its contributing factors could be important for understanding the role of poor sleep as a chronic disease risk factor.     

Radiographic joint space of the knee in healthy young adults

The primary objective of this study was to characterize normal variation in radiographic joint space of the knee in a large sample of healthy young adults and to identify factors that contribute to this variation. We measured radiographic knee joint space in 279 skeletally mature subjects, age between 16 and 22 years, who participated in the Fels Longitudinal Study. Minimum joint space was measured in the medial and lateral knee compartments. Independent sample t tests and correlation analyses were performed to examine sex differences and associations between joint space, joint size, and body size [weight, stature, body mass index (BMI)]. Results show that young men have thicker articular cartilage than young women in both the medial and lateral compartments of the knee. Significant positive correlations were found between joint space and body size measures in the total sample. When the sexes were considered independently, however, correlations between joint space and body size were significant in men only. Regression analyses of the combined-sex sample identified sex, BMI, and joint width as significant explanatory factors of medial joint space, together accounting for 26% of the observed variance. In contrast, sex was the sole significant explanatory factor of lateral joint space, explaining 19% of the observed variance. Results of this study show that during early adulthood, when articular cartilage is healthy and at its peak thickness, men have thicker knee cartilage than women. At this young age body size accounts for a modest proportion of the variation observed in knee cartilage thickness.     

The effects of walking speed on obstacle crossing in healthy young and healthy older adults

The effects of walking speed and age on the peak external moments generated about the joints of the trailing limb during stance just prior to stepping over an obstacle and on the kinematics of the trailing limb when crossing the obstacle were investigated in 10 healthy young adults (YA) and 10 healthy older adults (OA). The peak hip and knee adduction moments in OA were 21-43% greater than those in YA (p相似文献   

Interaction between resistance training and flexibility training in healthy young adults

To test the hypothesis that increases in muscle strength and flexibility are developed by specific training programs, 43 healthy young adults were tested before and after 4 different interventions conducted twice a week for 12 weeks: (a) resistance training only (n = 13); (b) flexibility training only (n = 11); (c) resistance and flexibility training (n = 9); and (d) no intervention (n = 10). There was no change in either strength or flexibility in the control group (p > 0.05). Resistance training improved muscle strength either alone (+14%; effect size = 0.53; p < 0.001) or in combination with flexibility training (+16%; effect size = 0.66; p = 0.032), but did not change flexibility (p = 0.610). Flexibility increased with specific training alone (+33%; p < 0.001) or in combination with resistance training (+18%; p < 0.001). In conclusion, in young, healthy subjects, resistance training alone did not increase flexibility, but resistance training did not interfere with the increase in joint range of motion during flexibility training. These results support the concept that specific training should be employed in order to increase either muscle strength or flexibility.     

Circadian rhythm of double (rate-pressure) product in healthy normotensive young subjects

The double product (DP), systolic blood pressure multiplied by heart rate, is a surrogate measure of myocardial oxygen demand and cardiac workload used increasingly today in medicine. The double product is more strongly correlated with left ventricular mass than the daily blood pressure mean. The purpose of this study was to describe the normative circadian pattern of the double product in healthy normotensive young adults. We studied 125 men and 75 women, 23.0+/-3.3 (mean +/- SD) years of age, without medical history of hypertension and 24h ambulatory systolic/diastolic blood pressure mean consistently below 135/85 mm Hg. Subjects underwent ambulatory blood pressure monitoring at 30-minute intervals for 48 consecutive hours once each season of the year, yielding 930 protocol-correct blood pressure and heart rate time series. Subjects maintained their usual routine of diurnal activity and nocturnal sleep and avoided use of over-the-counter and other medication. Circadian rhythmicity in the double product was established by population multiple-component analysis. The double product rose rapidly from the lowest value, attained 3h before awaking from sleep at night, to a markedly elevated level at the commencement of morning activity. The double product was highest in the afternoon, roughly 7h after the commencement of diurnal activity. In both men and women, the shape of the high-amplitude circadian rhythm in the double product was best described by a complex model composed of three cosine curves having periods of 24h, 12h, and 6h. The 24h mean in the double product of 8092.51+/-42.76 (mean +/- SD) in men was significantly lower than that of 8353.17+/-37.48 in women (P < .001). The circadian double amplitude of the rhythm was statistically significantly greater (P < .001) in men (50% of the 24h mean) than women (44% of the 24h mean). The double product did not differ between seasons in women, but it did in men (P = .017) due to reduced heart rate in summer. The circadian pattern of large amplitude in the double product and its gender differences must be taken into account when using this variable to assess cardiac workload, risk of left ventricular hypertrophy, and efficiency of antihypertensive therapy.     

Vital capacity in trained and untrained healthy young adults in the Netherlands

Slow inspiratory vital capacity was measured in 226 healthy young adults, aged from 17 to 35 years. The group included 119 men and 107 women, 87 trained subjects, 71 untrained subjects who intended to take part in a training program for competitive rowing, and 68 untrained subjects who never took part in any competitive sport. The vital capacity increased with height, weight, fat-free mass, height X fat-free mass, and height-independent fat-free mass, with men having significantly higher vital capacities than women of the same height or weight. In both males and females vital capacity showed the best relation with height X fat-free mass (correlation coefficients are 0.78 and 0.57 respectively). Multiple regression on vital capacity with height, weight, fat-free mass, height X fat-free mass, height-independent fat-free mass, percentage body fat, and age increased the correlation coefficient only slightly (0.80 and 0.59 respectively). The subjects had vital capacities that were much higher than those predicted for them by equations originating from the USA. There was no difference between the observed vital capacities and those predicted by equations originating from Europe. There is a difference in vital capacity between the European subjects studied and subjects of similar height studied in the USA. This implies that equations derived from subjects in the USA cannot be applied to European subjects. From our results we conclude that vital capacity is not increased by physical activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic architecture of knee radiographic joint space in healthy young adults

Evidence of a significant genetic component to the age-related degenerative joint disease osteoarthritis has been established, but the nature of genetic influences on normal joint morphology in healthy individuals remains unclear. Following up on our previous findings on the influence of body habitus on phenotypic variation in knee joint space [Duren et al., Human Biology 78:353-364 (2006)], the objective of the current study was to estimate the heritability of radiographic joint space in the knees of healthy young adults from a community-based sample of families. A sample of 253 subjects (mean age = 18.02 years) from 87 randomly ascertained nuclear and extended families was examined. Joint width (JW) and minimum joint space in the medial (MJS) and lateral (LJS) knee compartments were measured. A maximum-likelihood variance components method was used to estimate the heritability of MJS, LJS, and JW. Covariate effects of age, sex, age-by-sex interactions, stature, weight, and BMI were simultaneously estimated. Genetic correlation analyses were then conducted to examine relationships between trait pairs. MJS, LJS, and JW were each significantly heritable (p < 0.001), with heritabilities of 0.52, 0.53, and 0.63, respectively. The genetic correlation between MJS and LJS was not significantly different from 1. Genetic correlations between each joint space measure and JW were not significantly different from 0. This study demonstrates a significant genetic component to radiographic knee joint space during young adulthood in healthy subjects. This suggests that there are specific but as yet unidentified genes that influence the morphology of healthy articular cartilage, the target tissue of osteoarthritis. Genetic correlation analyses indicate complete pleiotropy between MJS and LJS but genetic independence of joint space and JW.     

Problems in heart rate and alpha electroencephalographic feedback

When a subject has demonstrated successful control over a feedback stimulus, the experimenter should not interpret this to mean that the subject has learned a specific correlated physiological function. Data from two types of experiments — attempted heart rate stoppage and alpha electro-encephalographic feedback control — demonstrate some of the problems. The apparent heart stoppage of one subject was caused by the decrease in arterial pressure which occurred during a Valsalva procedure. The successful control over feedback stimuli during an EEG feedback study led to confused results: in this case the alpha criterion was too broad and was satisfied by different alpha frequencies, amplitudes, phase relations, and toposcopic distributions. Grouped subject data would only confuse the interpretation further. Suggestions to avoid some EEG feedback pitfalls are given.     

Neuropeptide chronomics in clinically healthy young adults: circaoctohoran and circadian patterns

Endothelin-1 (ET-1) undergoes an about 8-h (circaoctohoran) rather than a circadian variation in clinical health. Herein, 24 h plasma concentrations of vasoactive intestinal peptide (VIP), substance P (SP), neuropeptide Y (NpY), and cortisol used as reference, were obtained from 20 healthy young adults starting at 07:00 or 19:00 h. Like ET-1, SP and NpY undergo a circaoctohoran variation, whereas VIP is circadian rhythmic, peaking during the night, some 8 h prior to the circadian acrophase of cortisol. Maps of circadian and extra-circadian patterns may serve for screening, diagnosis and a better understanding of mechanisms underlying the etiology of various diseases.     

Urinary excretion of immunoreactive prostaglandin F2 alpha in healthy children and adults

The 24-hours urinary excretion of immunoreactive prostaglandin F2 alpha (U-iPGF2 alpha) in normal children on a free diet was not significantly different in 30 boys (aged 3-15 years; geometric mean 589 ng/24 h) compared to 27 girls (aged 4-14 years; mean 473 ng/24 h). In both sexes this excretion rose with age until adolescence where it reached a plateau. In normal adults the men had significantly higher (p less than 0.001) excretions of U-iPGF2 alpha than the women; also body weight and urinary creatinine excretion were higher in men (p less than 0.001). In the children, as well as in the total population, U-iPGF2 alpha correlated best with body weight (r = 0.44 and r = 0.48 respectively; p less than 0.001) and the urinary creatinine excretion (r = 0.53 and 0.57 respectively; p less than 0.001); both body weight and urinary creatinine excretion are reflections of total body development. After the correction for urinary creatinine excretion or for body weight, the sex difference in the adult U-iPGF2 alpha totally disappeared.     

Effects of DDAVP on gender-specific verbal and visuospatial tasks in healthy young adults

Although several studies have demonstrated the efficacy of the vasopressin analog DDAVP in enhancing human cognition, few previous studies have explored possible interactions of treatment with DDAVP and gender in healthy young adults. The present study was undertaken to explore the effects of treatment with DDAVP on gender-specific tasks. Male and female volunteers were treated with either DDAVP or saline and asked to recall lists of words and to perform the Paper Folding and Stroop Color Word Tests. Although treatment with DDAVP produced few effects in these tasks, the effects that were noted involved impairment of performance.     

Effects of DDAVP on movement planning and execution processes in healthy young adults

This study investigated the effects of an acute dose of DDAVP on speed and consistency of planning and execution of simple and complex movements in healthy young adults. A simple reaction time task (SRT), a simple movement task (SMT), and a complex movement task (CMT) were performed with and without a 0.6 ml intranasal dose (60 micrograms) of DDAVP. Results indicated DDAVP-treated individuals planned and executed CMT and SRT tasks faster and more consistently than did placebo-treated subjects. There were nonsignificant DDAVP effects on speed and variability of both RT and MT processes involved in the SMT.