Allometric relationship between body size and peak VO2 relative to age at menarche

The present study examined allometric coefficients relating peak VO₂ and body size relative to the time of menarche. Peak oxygen uptake (peak VO₂     

Age at menarche in relation to adult body size and physique

The relationship of early and late menarche with adult body dimensions has been studied on a sample of 147 young adult women drawn from an urban Punjabi population of Chandigarh and Ludhiana. The results indicate that girls with early menarche (age 10 to 11) have significantly smaller skeletal dimensions (both longitudinal and transverse) and more subcutaneous fat than those with average or late menarche. The girls with late menarche have on average more height for weight than early maturers. Results indicate that there is a biological determinant of the observed association between menarcheal age and fatness and adult body size.     

Age at menarche in relation to adult body size and physique

The relationship of early and late menarche with adult body dimensions has been studied on a sample of 147 young adult women drawn from an urban Punjabi population of Chandigarh and Ludhiana. The results indicate that girls with early menarche (age 10 to 11) have significantly smaller skeletal dimensions (both longitudinal and transverse) and more subcutaneous fat than those with average or late menarche. The girls with late menarche have on average more height for weight than early maturers. Results indicate that there is a biological determinant of the observed association between menarcheal age and fatness and adult body size.     

The relationship between body composition and onset of menarche

Background: A late age of menarche in elite adolescent athletes is frequently attributed to low body fat/weight. If a critical body weight/fat is necessary for menarche, a reduction in the variability of these parameters would be observed at menarche compared to times before and after this event.

Aim: The study determined the variability in body mass (BM), per cent body fat (%BF) and total body fat (TBF) of girls between ?2 and +2 years from menarche.

Methods: Participants were part of the Saskatchewan Pediatric Bone Mineral Accrual Study (1991–1998). Body composition was assessed using dual X-ray absorptiometry (DXA). An individual's data was retained for analysis if they had at least four DXA scans between ?3 and +3 years from menarche. Values were interpolated from the cubic spline at whole years between ?2 and +2 years from menarche. Coefficient of variation (CV) was used to assess variability.

Results/Conclusion: Data on 61 girls were retained for analysis. The range in BM, TBF and %BF at menarche was 50.10 kg, 35050.06 g and 31.61%, respectively. Reductions in variability of body fat and weight were not apparent at menarche, which does not provide support for the hypothesis that a critical body weight/fat is required for menarche.     

The relationship between body composition and onset of menarche

BACKGROUND: A late age of menarche in elite adolescent athletes is frequently attributed to low body fat/weight. If a critical body weight/fat is necessary for menarche, a reduction in the variability of these parameters would be observed at menarche compared to times before and after this event. AIM: The study determined the variability in body mass (BM), per cent body fat (%BF) and total body fat (TBF) of girls between -2 and +2 years from menarche. METHODS: Participants were part of the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-1998). Body composition was assessed using dual X-ray absorptiometry (DXA). An individual's data was retained for analysis if they had at least four DXA scans between -3 and +3 years from menarche. Values were interpolated from the cubic spline at whole years between -2 and +2 years from menarche. Coefficient of variation (CV) was used to assess variability. RESULTS/CONCLUSION: Data on 61 girls were retained for analysis. The range in BM, TBF and %BF at menarche was 50.10 kg, 35050.06 g and 31.61%, respectively. Reductions in variability of body fat and weight were not apparent at menarche, which does not provide support for the hypothesis that a critical body weight/fat is required for menarche.     

Allometric scaling of strength measurements to body size

For comparative purposes, normalisation of strength measures to body size using allometric scaling is recommended. A wide range of scaling exponents have been suggested, typically utilising body mass, although a comprehensive evaluation of different body size variables has not been documented. Differences between force (F) and torque (T) measurements of strength, and the velocity of measurement might also explain some of the variability in the scaling exponents proposed. Knee extensor strength of 86 young men was assessed with measurement of torque at four velocities (0–4.19 rad s⁻¹) and force measured isometrically. Body size variables included body mass, height and fat-free mass. Scaling exponents for torque were consistently higher than for force, but the velocity of torque measurement had no influence. As the confounding effects of fat mass were restricted, scaling exponents and the strength of the power-function relationships progressively increased. Fat-free mass determined a surprisingly high proportion of the variance in measured strength (F, 31%; T, 52–58%). Absolute force and torque measurements, and even torque normalised for body mass, were significantly influenced by height, although strength measures normalised to fat-free mass were not. To normalise strength measurements to body mass, for relatively homogenous lean populations (body fat <20%), exponents of 0.66 (F) and 1.0 (T) are appropriate. For more adipose populations (body fat >20%) lower body mass exponents appear more suitable (F, 0.45; T, 0.68). Nevertheless, fat-free mass is the recommended index for scaling strength to body size, and higher exponents (F, 0.76; T, 1.12) are advocated in this case.     

Body size and fatness in young adults in relation to age at menarche

The relationships among age at menarche, body size, and body composition were considered in university students surveyed in 1970 (n = 342) and 1987 (n = 109). Recalled ages at menarche, stature, weight, and the triceps skinfold thickness were measured. Subjects ranged in age from 17.5 to 22.5 years in both surveys and were divided into four categories by age at menarche: before 12 years, 12.0 through 12.99 years, 13.0 through 13.99 years, and older than 14 years. In both the 1970 and 1987 surveys, later maturers had significantly more linear physiques than those experiencing menarche earlier. Late maturers also showed a tendency to lower values for the body mass index (BMI) and triceps skinfold compared with early maturers. Comparative data for women of the same age from the Fels Longitudinal Study (n = 234) showed similar findings. Women who reached menarche at ages older than 14 years were significantly taller than women with menarcheal ages less than 13 years. Women with menarcheal ages younger than 12 years were significantly heavier and had higher BMIs than those from any older menarcheal category. They also had significantly thicker triceps skinfolds than those with menarcheal ages older than 14 years. © 1992 Wiley-Liss, Inc.     

In utero exposure to organochlorines and age at menarche

BACKGROUND: To examine the effect of in utero exposure to polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) on age at menarche in offspring, we conducted a cohort study over two generations. METHODS: Female participants (and their offspring) in a Michigan angler cohort in which organochlorine levels had been determined previously were studied. Of their 213 female offspring aged 20-50 years, 151 participated in the study (71%). We retrospectively determined age at first menstrual bleeding. Based on repeated maternal serum measurements between 1973 and 1991, we extrapolated PCB and DDE serum levels at the time of pregnancy. To estimate the association between in utero PCB and DDE exposure and age at menarche, we used linear regression analyses controlling for birth date period, maternal age at delivery, birth weight, breastfeeding, education status and maternal height. RESULTS: An increase in the in utero DDE exposure of 15 micro g/l reduced age at menarche by 1 year (P = 0.04). There was no association with maternal PCB exposure. When controlling for estimated body size at menarche, the DDE association was no longer significant, based on a subsample of 102 women. CONCLUSION: The DDE effect on age at menarche encourages further research about in utero exposures. Prospective studies including the offspring's DDE level before menarche are of particular interest.     

The age at menarche and age at first birth in an undernourished population

A statistically significant relationship has been found between the age at menarche and the age at first birth among chronically-malnourished, lower-class Viennese women born in the late nineteenth century. Because the age at menarche depends on nutritional status, the above relationship is an indication that nutritional status must also have correlated positively with fertility rate, and therefore with population growth in societies with similar characteristics as this sample. Thus, the nutrition sensitivity of the age of first birth, and therefore of population growth are established in a chronically malnourished non-contraceptive historical population.     

Reproducibility of the cycling time to exhaustion at .VO2peak in highly trained cyclists.

The purpose of the present study was to examine, in highly trained cyclists, the reproducibility of cycling time to exhaustion (T(max)) at the power output equal to that attained at peak oxygen uptake (.VO2peak) during a progressive exercise test. Forty-three highly trained male cyclists (M +/- SD; age = 25 +/- 6 yrs; weight = 75 +/- 7 kg; .VO2peak = 64.8 +/- 5.2 ml.kg-1.min-1) performed two T(max) tests one week apart. While the two measures of T(max) were strongly related (r = 0.884; p < 0.001), T(max) from the second test (245 +/- 57 s) was significantly higher than that of the first (237 +/- 57 s; p = 0.047; two-tailed). Within-subject variability in the present study was calculated to be 6 +/- 6%, which was lower than that previously reported for T(max) in sub-elite runners (25%). The mean T(max) was significantly (p < 0.05) related to both the second ventilatory turnpoint (VT(2); r = 0.38) and to .VO2peak (r = 0.34). Despite a relatively low within-subject coefficient of variation, these data demonstrate that the second score in a series of two T(max) tests may be significantly greater than the first. Moreover, the present data show that T(max) in highly trained cyclists is moderately related to VT(2) and .VO2peak.     

17-beta-estradiol in relation to age at menarche and adult obesity in premenopausal women

BACKGROUND: We hypothesize that premenopausal endogenous estradiol may beassociated with age at menarche and adult overweight and obesity,potentially contributing to breast cancer risk. METHODS: We assessed age at menarche by questionnaire among 204 healthyNorwegian women, aged 25–35 years. Measures of body compositionincluded body mass index (BMI, kg/m²), waist circumference (WC,cm), waist-to-hip ratio (WHR) and fat percentage dual energyX-ray absorptiometry, (DEXA). Daily salivary 17-β-estradiol(E₂) concentrations were collected throughout one entire menstrualcycle and assessed by radioimmunoassay (RIA). Linear regressionanalyses and linear mixed models for repeated measures wereused and potential confounding factors and effect modifierswere tested. RESULTS: Among women with an early age at menarche (12 years), the overallmean salivary E₂ concentration increased by 3.7 pmol/l (95%confidence interval, 1.8–5.7 pmol/l) with each 9.8 cm(1 SD) increase in WC, which represents a 20.7% change in themean for the total group. Among the same early maturers, a 1SD (0.06) change in WHR was directly associated with a 24.0%change in mean E₂ concentration for the total group. CONCLUSIONS: Our findings support the hypothesis that early age at menarche,together with adult overweight and obesity, result in high levelsof 17-β-estradiol throughout the menstrual cycle.     

Sex differences in corpus callosum size: relationship to age and intracranial size.

This quantitative MRI study reports measurement of corpus callosum area taken from midsagittal brain images in 51 healthy men and 41 healthy women, spanning the adult age range (22 to 71 years). Men had larger brains and corpora callosa than women, but callosal size did not correlate with age in either sex. Intracranial (i.c.) volume (ICV) and midsagittal i.c. area (ICA) of brain were used in covariate, regression, and ratio analyses to determine whether sex differences in the corpus callosum endured with statistical adjustment for sex differences in maximally attained brain size. With the exception of one ratio measure, the different statistical adjustments for the contribution of sex differences in brain size to corpus callosum size all indicated that men had larger corpora callosa than women for their brain size. A subsample of men and women selected to be matched on i.c. volume and age confirmed this statistical observation. Sexual dimorphism in the corpus callosum is not a simple artifact of sex differences in brain size and may reflect differences in connectivity necessitated by differences in brain size.     

VO2 responses to different intermittent runs at velocity associated with VO2max.

The purposes of this study were (1) to determine the time sustained above 90% of VO2max in different intermittent running sessions having the same overall time run at the velocity (vVO2max) associated with VO2max, and (2) to test whether the use of a fixed-fraction (50%) of the time to exhaustion at vVO2max (Tlim) leads to longer time spent at a high percentage of VO2max. Subjects were 8 triathletes who, after determination of their track vVO2max and Tlim, performed three intermittent running sessions alternating the velocity between 100% and 50% of vVO2max, termed 30 s-30 s, 60 s-30 s, and 1/2 Tlim, where the overall time at vVO2max was similar (= 3 x Tlim). VO2max achieved in the incremental test was 71.1 +/- 3.9 ml.min-1.kg-1 and Tlim was 236 +/- 49 s. VO2peak and peak heart rate were lower in 30 s-30 s than in the other intermittent runs. The time spent above 90% of VO2max was significantly (p < 0.001) longer either in 60 s-30 s (531 +/- 187 s) or in 1/2 Tlim-1/2 Tlim (487 +/- 176 s) than in 30 s-30 s (149 +/- 33 s). Tlim was negatively correlated with the time (in % of Tlim) spent above 90% of VO2max in 30 s-30 s (r = -0.75, p < 0.05). Tlim was also correlated with the difference of time spent over 90% of VO2max between 60 s-30 s and 30 s-30 s (r = 0.77, p < 0.05), or between 1/2 Tlim-1/2 Tlim and 30 s-30 s (r = 0.97, p < 0.001). The results confirm that vVO2max and Tlim are useful for setting interval-training sessions. However, the use of an individualized fixed-fraction of Tlim did not lead to longer time spent at a high percentage of VO2max compared to when using a fixed work-interval duration.     

Motor performance during adolescence and age thirty as related to age at peak height velocity

Relationships between motor performance, as measured by various fitness tests, and age at peak height velocity have been studied in a sample of 173 Flemish boys, measured yearly between +/- 13 and +/- 18 years and again as adults at 30 years of age. In addition to correlation studies, comparisons were made between boys with an early, average and late age at peak height velocity. To summarize the successive measurements during adolescence, a longitudinal principal component analysis was carried out. The first component can be interpreted as an average percentile level component. During adolescence, three performance tasks, namely speed of limb movement, explosive strength and static strength, are negatively related to age at peak height velocity; thus early maturers performed significantly better than late maturers. However, between late adolescence and adulthood, a cross-over of the average distance curves between 18 and 30 years of age was noted for almost all motor tasks. The late maturers not only caught up the early maturers, but there were significant differences for explosive strength and functional strength in favour of late maturers. In order to predict performance in adulthood from measures during adolescence, the following hypothesis is suggested: the best results at adulthood are obtained by those men who were already good performers during adolescence and who were late maturers, while the worst results are obtained by poor performers during adolescence who were early maturers.     

Lack of association between age at menarche and age at menopause: Pró-Saúde Study,Rio de Janeiro,Brazil

Objective

To investigate the association between age at menarche and age at menopause among Brazilian women.

Methods

This study is based on cross-sectional data obtained in 1999 from technical and administrative employees who were recruited for participation at the Pró-Saúde cohort study in Rio de Janeiro, Brazil. The final study population consisted of 1462 women. Participants completed a self-administered multidimensional questionnaire. In addition to the study exposure (age at menarche) and outcome (age at menopause) variables, the following independent variables were selected: parity; schooling; self-classified race; use of oral contraceptives; smoking; and body mass index (BMI). Median ages at natural menopause and the survival curves were estimated by the Kaplan–Meier method. To estimate the association between age at menarche and age at natural menopause, a Cox semi-parametric model was fitted. Women who were still menstruating, who had undergone surgery for the removal of the uterus or ovaries, or who were in perimenopause were censored.

Results

Natural menopause occurred in 205 women. The median and mode for natural menopause were 51.7 and 50 years of age, respectively. In the multivariate analysis, no statistically significant association was observed between age at menarche and age at menopause (HR: 1.01; 95% CI: 0.93–1.11).

Conclusion

In the current study, the hypothesis of an association between age at menarche and age at natural menopause was not confirmed. Specific studies on the determinants of age at menopause should be conducted, due to the importance of menopause in the causality of diseases with high case mortality rate.     

The effects of recreational sport on VO2peak, VO2 kinetics and submaximal exercise performance in males and females

The purpose of the present study was to examine changes in VO_2peak, VO₂ kinetics and steady-state exercise performance following 4 weeks of participation in recreational sport. Subjects (male n = 8, female n = 9) participated in recreational sport (basketball, floor hockey and soccer) four times per week for 4 weeks. Both before and after training, VO_2peak was measured on a cycle ergometer, VO₂ kinetics was determined as the average of three transitions to 80 W, and heart rate (HR) and respiratory exchange ratio (RER) were measured during 60 min at a work rate corresponding to 50 % of pre-training VO_2peak. HR was also monitored during all training sessions. After training, VO_2peak was increased in females, but not males, while VO₂ kinetics (τVO₂) were sped in both males and females. HR during constant load exercise was reduced in both males and females, but exercise RER was only reduced in females. Mean HR during participation in sport was higher in males than females and higher during basketball than both floor hockey and soccer. These results demonstrate that training adaptations traditionally associated with endurance exercise can also be obtained through regular participation in recreational sport.