Historical trends in height, weight, and body mass: Data from U.S. Major League Baseball players, 1869-1983

We employ a unique dataset of Major League Baseball (MLB) players - a select, healthy population - to examine trends in height, weight, and body mass in birth cohorts from 1869 to 1983. Over that 115-year time period, U.S. born MLB players have gained, on average, approximately 3 in. (7.6 cm) in height and 27.0 lb (12.2 kg) in weight, which has contributed a 1.6-unit increase in the body mass index. Where comparable data are available, U.S. born MLB players are about 2.0 in. (5.1 cm) taller and 20.0 lb (9.1 kg) heavier but substantially less obese than males in the general U.S. population. But both groups exhibit similar height and weight trends; the majority of height and weight gains take place in cohorts that were born prior to World War II, followed by slower gains and occasional declines in height and weight for cohorts born in 1939 and later.     

Epidemiology of Down syndrome (Trisomy 21), Hawaii, 1986-97

BACKGROUND: The live birth prevalence of Down syndrome is approximately 10 per 10,000 live births in the United States. Down syndrome prevalence has been reported to change over time and to vary by selected demographic factors. METHODS: Data from a population-based birth defects registry in Hawaii involving 363 Down syndrome cases delivered during 1986-97 were used to calculate overall prevalence and to investigate secular trends and differences by selected demographic factors. RESULTS: The total (live birth, fetal death, and elective termination) prevalence was 14.74 per 10,000 live births and fetal deaths. The unadjusted live birth prevalence was 8.67 per 10,000 live births. The adjusted live birth (live births and proportion of elective terminations expected to have resulted in live births) prevalence was 12.59 per 10,000 live births. No significant secular trends were observed for either total prevalence (P = 0.688) or adjusted live birth prevalence (P = 0.604). The total Down syndrome prevalence per 10,000 live births was highest for Far East Asians (22.01), followed by whites (17.06), Filipinos (15.94), and Pacific Islanders (9.21). Prevalence per 10,000 births was higher in metropolitan Honolulu (18.57) than in the rest of Hawaii (14.15). After adjusting for maternal age, however, the differences within the demographic groups were not statistically significant. CONCLUSIONS: The live birth prevalence of Down syndrome in Hawaii during 1986-97 was lower than reported in the literature. Prevalence did not change significantly over time. Any differences in prevalence by maternal race/ethnicity and place of residence appeared to result from differences in maternal age distribution.     

It’s All in the Timing: Birth Seasonality and Infant Survival in <Emphasis Type="BoldItalic">Eulemur rubriventer</Emphasis>

Highly seasonal breeding has been considered one of the keys to understanding Malagasy primate socioecology. Strict seasonal breeding may be particularly critical for Malagasy primates because they live in such energetically challenging seasonal environments. Lemurs also live in highly unpredictable environments, and there is growing evidence that reproductive timing may be mediated by additional factors, suggesting that more relaxed breeding seasonality is adaptive in some cases. I tested the adaptive breadth of the birth peak in Eulemur rubriventer, which breed in several different months. I describe reproduction in the species by determining the timing and extent of the birth season (period in which all births occur) and birth peak (period in which the majority of births occur); test whether relaxed reproductive seasonality might increase reproductive success by comparing infant mortality within and outside the birth peak; and model the extent to which fruit availability has an influence on the timing of reproduction. I collected birth data on 5 groups in 2003–2005, which I combined with demographic data that D. Overdorff collected from 5 focal groups and additional censused groups between 1988 and 1996. Thirty births occurred in 8 different months. Births were significantly seasonal, with a unimodal birth peak in late August/September/October, and a mean birth date of October 11. Twenty-three births (76.7%) occurred within 54 d (14.79%) of the year. No births occurred May–July, indicating that conceptions did not occur from late December through late February, and cycling (estimated using gestation length) did not occur until ca. 101 d after the austral summer solstice (December 21). Of 22 infants followed regularly, 18 were born in the birth peak, of which 2 died (11%). All 4 infants born out of season died. Based on fruit availability, I calculated a Theoretical Overlap index (T), which indicated a 3-mo window with optimal food conditions for reproduction. This window corresponded to the timing and breadth of the birth peak in Eulemur rubriventer. These results indicate that a breeding season >3 mo within a given year is not adaptive in the species, likely due in large part to the availability of fruit during key reproductive stages, particularly before breeding.     

Effect of various warm-up devices on bat velocity of intercollegiate baseball players

A variety of warm-up devices are available to baseball players to use before their game at-bat. Past baseball research evaluating warm-up devices indicates that implements that are ±12% of standard game bat weight produce the greatest bat velocities for high school and intercollegiate players. The purpose of this study was to examine the effect of various warm-up devices on bat velocity (BV) of intercollegiate baseball players. Twenty-two Division I intercollegiate baseball players (age = 20.0 ± 1.5 years, height = 182.6 ± 8.3 cm, body mass = 91.4 ± 11.4 kg, lean body mass = 78.8 ± 8.9 kg, % body fat = 13.6 ± 3.8) participated in a warm-up with 1 of 10 weighted devices on separate days. Each of the 10 testing sessions consisted of a standardized warm-up, 3 dry swings as hard as possible with the assigned warm-up device, 2 comfortable dry swings with a standard game baseball bat followed by 3 game swings (20-second rest between swings) while hitting a baseball off of a batting tee with the same standard game baseball bat. Results indicated that there were no statistically significant differences in BV after using any of the 10 warm-up devices. For male intercollegiate baseball players, results indicate that warm-up devices varying from 623.7 to 2,721.5 g (22-96 oz.) did not change mean BV of a standard game baseball bat, suggesting that intercollegiate players can use any of the 10 warm-up devices in the on-deck circle and maintain their BV. Therefore, personal preference as to which warm-up implement to use in the on-deck circle is advised.     

The seasonality of births in Canada

Earlier studies on the seasonality of births indicate that a major peak occurs in August and September and a minor peak in January and February. This study uses the 1984 Canadian Fertility Survey data on reproductive history to examine birth and pregnancy seasonalities, and shows that the 'worst' months for births are January and February and the 'best' months are March, April and May. There is no systematic pattern in the seasonality of pregnancies, possibly because effective birth control allows couples to plan the timing of births.     

Effects of a 4-week youth baseball conditioning program on throwing velocity

Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (each 75 minutes) weekly for 4 weeks, which comprised a sport specific warm-up, resistance training with elastic tubing, a throwing program, and stretching. Throwing velocity was assessed initially and at the end of the 4-week conditioning program for both control and training groups. The level of significance used was p < 0.05. After the 4-week conditioning program, throwing velocity increased significantly (from 25.1 ± 2.8 to 26.1 ± 2.8 m·s) in the training group but did not significantly increase in the control group (from 24.2 ± 3.6 to 24.0 ± 3.9 m·s). These results demonstrate that the short-term 4-week baseball conditioning program was effective in increasing throwing velocity in youth baseball players. Increased throwing velocity may be helpful for pitchers (less time for hitters to swing) and position players (decreased time for a runner to advance to the next base).     

Astrovirus MLB1 is not associated with diarrhea in a cohort of Indian children

Astroviruses are a known cause of human diarrhea. Recently the highly divergent astrovirus MLB1 (MLB1) was identified in a stool sample from a patient with diarrhea. It has subsequently been detected in stool from individuals with and without diarrhea. To determine whether MLB1 is associated with diarrhea, we conducted a case control study of MLB1. In parallel, the prevalence of the classic human astroviruses (HAstVs) was also determined in the same case control cohort. 400 cases and 400 paired controls from a longitudinal birth cohort in Vellore, India were analyzed by RT-PCR. While HAstVs were associated with diarrhea (p = 0.029) in this cohort, MLB1 was not; 14 of the controls and 4 cases were positive for MLB1. Furthermore, MLB1 viral load did not differ significantly between the cases and controls. The role of MLB1 in human health still remains unknown and future studies are needed.     

Timing of births in sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus).

We monitored the birth patterns of sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus) during a 4‐yr period from October 1996 to August 2000 at the Estação Biológica de Caratinga, Minas Gerais, Brazil. Brown howler monkey births (n = 34) occurred throughout the year, and birth frequencies did not differ between rainy and dry season months. The aseasonal birth patterns of the howler monkeys differed significantly from the dry season concentration and dry month peak in muriqui births (n = 23). We found no effects of infant sex or the number of females on interbirth intervals (IBIs) in our 10 howler monkey study troops. IBIs of brown howler monkeys averaged 21.2 ± 2.5 mo (n = 8, median = 21.0 mo), and were significantly shorter following dry season births than rainy season births. Their IBIs and yearling survivorship (74%) were similar to those reported for other species of howler monkeys, but yearling survivorship was much lower than that of muriquis (94%), whose IBIs were more than 12 mo longer than those of the howler monkeys. Our study extends comparative knowledge of birth patterns in Alouatta to a poorly known species, and provides insights into the different ways in which diet and life history may affect the timing of births in large‐bodied platyrrhines under the same seasonal ecological conditions. Am. J. Primatol. 55:87–100, 2001. © 2001 Wiley‐Liss, Inc.     

Birth seasonality and interbirth intervals in free-ranging formosan macaques,Macaca cyclopis, at Mt. Longevity, Taiwan

Thebirth season of Formosan macaqueM. cyclopis during our study started in February and ended in August with a peak in the second half of April and the first half of May. The average birth rate was 82%±21 for 114 females with four years of breeding records. Our study reports that a time span of one year between births can be considered as the norm for the wildM. cyclopis. Of the 288 inter-birth intervals (IBI), 88.5% showed a 1-year interval (mean 364±SD 29 days); 11% showed 2-year interval (727±36 days); and 1% (2 females) had 3-year interval (range 1030–1040 days). The IBI for females that had infant loss within six months of life were the shortest. But there was no significant difference from that of females that had stillbirth (p>0.9) and infant that survived for first six months of life (p>0.06). However, among 255 cases of 1-year IBI, stillbirth or following infant loss within six months of life did significantly shorten IBI for ten days (F _1,253=5.74,p<0.05).     

我国优秀青少年田径运动员相对年龄分布特征及原因分析

目的：基于国外学者对相对年龄在体育运动中的研究,观察我国优秀田径运动员中是否存在＂相对年龄＂优势的现象,进而对其产生的原因及调控措施进行探讨。方法：采用文献资料调查法,收集了2007年国家注册的田径运动员的出生日资料进行统计分析。依照国际田径竞赛规则,样本分为少年乙组（15岁、16岁）、少年组（17岁、18岁）和青年组（19岁、20岁）。计数资料采用卡方检验进行统计学分析。结果：各组男子田径运动员的相对年龄分布经卡方检验,差异均十分显著,并且各组出生月份分布明显偏向比赛赛程的开始月份（1月）,尤其是出生在Q1时间段的运动员占所在年龄组人数的比例最大。在以每两岁为划分标准的同一比赛年龄组中,前一年出生的运动员的＂相对年龄＂优势现象更为显著。结论：我国男子和女子田径运动员各年龄组中均存在着＂相对年龄＂优势现象,且出生日明显偏向于选择日,随年龄的增长相对年龄影响有减小趋势。     

National estimates and race/ethnic-specific variation of selected birth defects in the United States, 1999-2001

BACKGROUND: In the United States, birth defects affect approximately 3% of all births, are a leading cause of infant mortality, and contribute substantially to childhood morbidity. METHODS: Population-based data from the National Birth Defects Prevention Network were combined to estimate the prevalence of 21 selected defects for 1999-2001, stratified by surveillance system type. National prevalence was estimated for each defect by pooling data from 11 states with active case-finding, and adjusting for the racial/ethnic distribution of US live births. We also assessed racial/ethnic variation of the selected birth defects. RESULTS: National birth defect prevalence estimates ranged from 0.82 per 10,000 live births for truncus arteriosus to 13.65 per 10,000 live births for Down syndrome. Compared with infants of non-Hispanic (NH) white mothers, infants of NH black mothers had a significantly higher birth prevalence of tetralogy of Fallot, lower limb reduction defects, and trisomy 18, and a significantly lower birth prevalence of cleft palate, cleft lip with or without cleft palate, esophageal atresia/tracheoesophageal fistula, gastroschisis, and Down syndrome. Infants of Hispanic mothers, compared with infants of NH white mothers, had a significantly higher birth prevalence of anencephalus, spina bifida, encephalocele, gastroschisis, and Down syndrome, and a significantly lower birth prevalence of tetralogy of Fallot, hypoplastic left heart syndrome, cleft palate without cleft lip, and esophageal atresia/tracheoesophageal fistula. CONCLUSIONS: This study can be used to evaluate individual state surveillance data, and to help plan for public health care and educational needs. It also provides valuable data on racial/ethnic patterns of selected major birth defects.     

A demographic analysis of the Wisconsin Regional Primate Center rhesus colony, 1962–1982

A detailed demographic analysis was made of the Wisconsin Regional Primate Research Center rhesus colony from vital statistics recorded over a 20-year period. Techniques used were based on demographic and epidemiological methods developed for human populations, which provide the potential for making standardized measurements within captive primate colonies. A life table based on 1,086 deaths showed an abnormally high survivorship at the older ages, probably caused by a tendency to retain especially robust animals for breeding purposes. During the period of study, 2,194 animals were removed for sale or research. Removal rates were relatively uniform across ages. Age-specific fertility rates based on 1,616 births occurring during the second decade showed a relatively rapid increase in births from about age 2 through age 12, with peak fertility persisting until about age 20. Vital events showed significant seasonality, with a birth peak in April and May. Analysis of the stable age structure (excluding removal) showed an intrinsic growth rate of 6.3%. With removal rates added, the growth rate dropped to ?0.3%. Although the use of these methods is probably warranted onlyby the level of detail found in captive colony records, analysis of captive colonies can provide information relevant to the demography of wild primates.     

Comparison of three baseball-specific 6-week training programs on throwing velocity in high school baseball players

Throwing velocity is an important baseball performance variable for baseball pitchers, because greater throwing velocity results in less time for hitters to make a decision to swing. Throwing velocity is also an important baseball performance variable for position players, because greater throwing velocity results in decreased time for a runner to advance to the next base. This study compared the effects of 3 baseball-specific 6-week training programs on maximum throwing velocity. Sixty-eight high school baseball players 14-17 years of age were randomly and equally divided into 3 training groups and a nontraining control group. The 3 training groups were the Throwers Ten (TT), Keiser Pneumatic (KP), and Plyometric (PLY). Each training group trained 3 d·wk(-1) for 6 weeks, which comprised approximately 5-10 minutes for warm-up, 45 minutes of resistance training, and 5-10 for cool-down. Throwing velocity was assessed before (pretest) and just after (posttest) the 6-week training program for all the subjects. A 2-factor repeated measures analysis of variance with post hoc paired t-tests was used to assess throwing velocity differences (p < 0.05). Compared with pretest throwing velocity values, posttest throwing velocity values were significantly greater in the TT group (1.7% increase), the KP group (1.2% increase), and the PLY group (2.0% increase) but not significantly different in the control group. These results demonstrate that all 3 training programs were effective in increasing throwing velocity in high school baseball players, but the results of this study did not demonstrate that 1 resistance training program was more effective than another resistance training program in increasing throwing velocity.     

Habitat and reproductive phenology of wild boar (Sus scrofa) in the western Iberian Peninsula

We examined the reproductive phenology of wild boar populations in four regions of the western Iberian Peninsula during the 1999/2000 hunting season (October–February). To estimate conception dates and birth distribution frequencies, we used foetal weights. Regions differed significantly, and we detected a relationship between region and birth distribution frequencies. Throughout the year, food availability had a major influence on the distribution of farrowing. Although a short period of high food availability leads to highly synchronous births, even in relatively harsh environmental conditions, adult females that exploit low-quality food items appear to be able to give birth at any time of the year.     

Differences in the Head Movement During Baseball Batting between Skilled Players and Novices

ABSTRACT: Nakata, H, Miura, A, Yoshie, M, and Kudo, K. Differences in the head movement during baseball batting between skilled players and novices. J Strength Cond Res 26(10): 2632-2640, 2012-We investigated the pattern of head movement during baseball batting in 8 skilled players and 9 unskilled novices, using a high-speed video camera. The 2 directions of head movement were analyzed as an X-axis (from the home plate to the pitcher's plate) and Z-axis (vertical downward). On the X-axis, peak latency, peak value, the distance from the peak to the value at bat-ball impact, and data variability were compared between the 2 groups. On the Z-axis, peak latency, downward distance, and data variability were analyzed. Peak latency on the X-axis occurred significantly earlier in baseball players than in novices (p < 0.001), and the difference between the minimum peak and impact was significantly larger in the players (p < 0.05). The variability in peak latency on the X-axis was significantly larger in the novices (p < 0.05). The variability in peak value on the Z-axis was also significantly larger in the novices (p < 0.05). Our findings showed that the significant differences in head movement between the 2 groups should help baseball players, beginners, coaches, and strength and conditioning professionals to improve performance, be effectively applied to actual practice, and enhance coaching for batting.     

Strength and conditioning practices of Major League Baseball strength and conditioning coaches

This study describes the results of a survey of the practices of Major League Baseball strength and conditioning (MLB S&C) coaches. The response rate was 70.0% (21 of 30). This survey examines (a) background information, (b) physical testing, (c) flexibility development, (d) speed development, (e) plyometrics, (f) strength/power development, (g) unique aspects, and (h) comments. Results indicate, in part, that coaches assess an average of 3.6 parameters of fitness, with body composition testing being the most commonly assessed parameter. All coaches use a variety of flexibility development strategies. All coaches use speed development strategies, with form running drills being the most common. Twenty of 21 (95.2%) coaches employ plyometric exercises with their athletes. Eighteen of 21 (85.7%) of MLB S&C coaches follow a periodization model (PM). Five of 21 coaches (23.8%) indicated that their athletes use Olympic-style lifts. The squat and its variations and the lunge and its variations were most frequently identified as the first and second most important exercises used to train the athletes. This survey provides detailed information about strength and conditioning practices at the most competitive level of baseball and serves as a review, as well as a source of applied information and new ideas.     

Seasonal Parameters in Newborns under Conditions of the European North

Data on all births in women of the city of Syktyvkar and adjacent villages (38 377 and 3828 births, respectively) were analyzed for the period from 1980 to 1999. Data on the women's age at childbirth, the delivery time, the body weight and length of the newborns, and their scores on the Apgar scale were taken into account. The season was found to be of importance for pregnancy and was associated with the woman's age at conception. The birth outcome parameters were identified as sensitive markers of the effect of unavoidable environmental factors of the North on the bodies of its residents.     

Reproductive parameters of wild Trachypithecus leucocephalus: seasonality,infant mortality and interbirth interval

Understanding the reproductive parameters of endangered primate species is vital for evaluating the status of populations and developing adequate conservation measures. This study provides the first detailed analysis of the reproductive parameters of wild white‐headed langurs (Trachypithecus leucocephalus), based on demographic data collected over an 8‐year period in the Nongguan Karst Hills in Chongzuo County, Guangxi, China. From 1998 to 2002, a total of 133 live births were recorded in the population based on systematic censuses. Births occurred throughout the year, but the temporal pattern was highly correlated with seasonal variation in temperature and rainfall, with the birth peak coinciding with the dry and cold months of November–March. The average birthrate was 0.47±0.13 births per female per year and mortality for infants younger than 20 months was 15.8%. From 1998 to 2006, 14 females gave birth to 41 infants in four focal groups. The average age at first birth for female langurs was 5–6 years (n=5) and the interbirth interval (IBI) was 23.2±5.2 months (median=24.5 months, n=27). Infants are weaned at 19–21 months of age. The IBI for females with infant loss before weaning was significantly shorter than those for females whose infants survived. It appears that birth seasonality in the white‐headed langurs is influenced by seasonal changes in food availability. The timing of conceptions was found to coincide with peak food availability. The reproductive parameters for white‐headed langurs reported here are quite similar to those reported for other colobine species. One major difference is our observation of lower infant mortality in Trachypithecus. Am. J. Primatol. 71:558–566, 2009. © 2009 Wiley‐Liss, Inc.     

Electromyographic activity of lower limbs to stop baseball batting

We investigated the muscle activation pattern of the lower limbs for the stopping motion of baseball batting by recording surface electromyography (EMG) from 8 muscles, the left and right rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) muscles. First, muscle activities for 'Swing' and 'Stopping' trials were examined in 10 skilled baseball players and 10 unskilled novices. Second, the characteristics of EMG activities for 'Stopping' were compared between the 2 groups. The peak latencies of EMG were significantly shorter in 'Stopping' than in 'Swing' at the right-TA, left-BF, and left-MG between both groups. The peak amplitudes of EMG activity were significantly larger in 'Swing' than in 'Stopping' at the right-TA, left-BF, and left-MG in both groups. In addition, the peak amplitudes of EMG activity for 'Stopping' were significantly larger in the players than in novices at the right-RF and right-TA. The characteristics of EMG activity clearly differed between 'Swing' and 'Stopping,' and between baseball players and nonplayers, indicating that evaluating the EMG activity in batting enables the understanding of proficiency. Our findings should help players, novices, and coaches to optimize batting performance.     

Effect of wrist and forearm training on linear bat-end, center of percussion, and hand velocities and on time to ball contact of high school baseball players

This study examined the effects of 12 weeks of wrist and forearm training on linear bat-end velocity (BV), center of percussion velocity (CV), hand velocity (HV), and time to ball contact of high school baseball players. Forty-three baseball players were randomly assigned by a stratified sampling technique to 1 of 2 training groups. Group 1 (n = 23) and group 2 (n = 20) performed the same full-body resistance exercises while training 3 days a week for 12 weeks according to a stepwise periodized model. Group 2 also performed wrist and forearm exercises 3 days a week for 12 weeks. Wrist and forearm strength were measured pre- and posttraining. Linear BV, CV, HV, and time to ball contact were recorded pre- and posttraining by a motion-capture system. A 3 repetition maximum (RM) parallel squat and bench press were measured at baseline and after 4, 8, and 12 weeks of training. Both groups showed statistically significant increases (p < or = 0.01) in linear BV, CV, and HV (m.s(-1) +/- SD) after 12 weeks of training; however, there were no differences between the 2 groups. Both groups statistically increased wrist and forearm strength (p < or = 0.05). Group 2 had statistically greater increases (p < or = 0.05) in 10 of 12 wrist and forearm strength measures than did group 1. Both groups made statistically significant increases in predicted 1RM parallel squat and bench press after 4, 8, and 12 weeks of training; however, there were no differences between groups. These data indicate that a 12-week stepwise periodized training program can significantly increase wrist and forearm strength, linear BV, CV, and HV among high school baseball players. However, increased wrist and forearm strength did not contribute to further increases in linear BV, CV, or HV.