Anthropometric and performance variables discriminating elite American junior men weightlifters

The purpose of this study is to identify physical and performance variables that discriminate elite American junior-aged men weightlifters from nonelite performers. Using a cross-sectional design, multiple discriminant analysis was used to determine field tests identifying elite male junior weightlifters. Young men who were participants (n = 115) at the Junior National and Junior Olympics Weightlifting Championships volunteered as subjects (mean +/- SD age = 14.8 +/- 2.3 years). Elite weightlifters (n = 20) were identified as the top 17.5% of national-level competitors when weightlifting performances were adjusted for body mass using the Sinclair equation. All other weightlifters were classified as nonelite (n = 95). Test batteries were performed immediately upon completion of a national-level weightlifting competition. Variables measured included easily-administered field tests of physical dimensions and body composition, muscular strength and power, flexibility, and gross motor control. The resulting regression equations correctly classified 84.35% of the weightlifters as elite or nonelite. Five variables significantly contributed to the discriminant analysis (Wilks Lambda = 0.6637392, chi(2) = 44.880, df = 5, p < 0.0001, adjusted R(2) = 0.67). Body mass index accounted for 23.13% of the total variance, followed by vertical jump (22.78%), relative fat (18.09%), grip strength (14.43%), and torso angle during an overhead squat (0.92%). The use of these 5 easily administered field tests is potentially useful as a screening tool for elite American junior men weightlifters.     

Physiological and anthropometric correlates of tackling ability in junior elite and subelite rugby league players

This study investigated the tackling ability of junior elite and subelite rugby league players, and determined the relationship between selected physiological and anthropometric characteristics and tackling ability in these athletes. Twenty-eight junior elite (mean ± SD age, 16.0 ± 0.2 years) and 13 junior subelite (mean ± SD age, 15.9 ± 0.6 years) rugby league players underwent a standardized 1-on-1 tackling drill in a 10-m grid. Video footage was taken from the rear, side, and front of the defending player. Tackling proficiency was assessed using standardized technical criteria. In addition, all players underwent measurements of standard anthropometry (stature, body mass, and sum of 7 skinfolds), acceleration (10-m sprint), change of direction speed (505 test), and lower body muscular power (vertical jump). Junior elite players had significantly greater (p < 0.05) tackling proficiency than junior subelite players (65.7 ± 12.5 vs. 54.3 ± 16.8%). Junior elite players tended to be taller, heavier, leaner, and have greater acceleration, change of direction speed, and muscular power, than the junior subelite players. The strongest individual correlates of tackling ability were acceleration (r = 0.60, p < 0.001) and lower body muscular power (r = 0.38, p < 0.05). When multiple linear regression analysis was performed to determine which of the physiological and anthropometric characteristics predicted tackling ability, fast acceleration was the only variable that contributed significantly (r2 = 0.24, p < 0.01) to the predictive model. These findings demonstrate that fast acceleration, and to a lesser extent, lower body muscular power contribute to effective tackling ability in junior rugby league players. From a practical perspective, strength and conditioning coaches should emphasize the development of acceleration and lower body muscular power qualities to improve tackling ability in junior rugby league players.     

Do skill-based conditioning games offer a specific training stimulus for junior elite volleyball players?

This study investigated the specificity of skill-based conditioning games and compared the effectiveness of skill-based conditioning games and instructional training for improving physical fitness and skill in junior elite volleyball players. Twenty-five junior volleyball players (mean age +/- SE, 15.6 +/- 0.1 years) participated in this study. Heart rate data were collected on all players during the Australian Junior Volleyball Championships. After the competition, players were randomly allocated into a skill-based conditioning games group (n = 12) or an instructional training group (n = 13). Each player participated in a 12-week training program that included 3 organized court training sessions per week. No significant differences (P > 0.05) were detected between competition and skill-based conditioning games for the percentage of time spent in low-intensity, moderate-intensity, and high-intensity activities. Skill-based conditioning games induced improvements in vertical jump, spike jump, speed, agility, upper-body muscular power, and estimated maximal aerobic power, whereas technical instruction improved only spike jump and speed. Conversely, instructional training induced meaningful improvements in all measurements of skill, whereas improvements in technical skill after skill-based conditioning games were uncommon and typically small. The results of this study show that skill-based conditioning games offer a specific training stimulus to simulate the physiological demands of competition in junior elite volleyball players. Although the improvements in physical fitness after training were greater with skill-based conditioning games, instructional training resulted in greater improvements in technical skill in these athletes. These findings suggest that a combination of instructional training and skill-based conditioning games is likely to confer the greatest improvements in fitness and skill in junior elite volleyball players.     

Physiological and anthropometric characteristics of Australian junior national, state, and novice volleyball players

The purpose of this study was to investigate the physiological and anthropometric characteristics of junior volleyball players competing at the elite, semi-elite, and novice levels and to establish performance standards for these athletes. One hundred and fifty-three junior national (N = 14 males; N = 20 females), state (N = 16 males; N = 42 females), and novice (N = 27 males; N = 34 females) volleyball players participated in this study. Subjects underwent measurements of standard anthropometry (body mass, height, standing reach height, and sum of 7 skinfolds), lower-body muscular power (vertical jump and spike jump), upper-body muscular power (overhead medicine ball throw), speed (5-m and 10-m sprint), agility (T-test), and estimated maximal aerobic power (multistage fitness test) during the competitive phase of the season, after obtaining a degree of match fitness. Significant differences (p < 0.05) were detected among junior national, state, and novice volleyball players for height, standing reach height, skinfold thickness, lower-body muscular power, agility, and estimated maximal aerobic power, with the physiological and anthropometric characteristics of players typically improving with increases in playing level. Male players were taller, heavier, leaner, and had greater standing reach height, speed, agility, muscular power, and estimated maximal aerobic power than female players. These findings provide normative data and performance standards for junior volleyball players competing at the elite, semi-elite, and novice levels. Given the improvements in lower-body muscular power, agility, and estimated maximal aerobic power with increased playing level, and given the importance of these qualities to competitive performances, conditioning coaches should train these qualities to improve the playing performances of junior volleyball players.     

Ventilatory response to rowing and cycling in elite oarswomen

Rowing is a unique exercise for humans, and the imposed biomechanical motion may alter both respiratory mechanics and timing. To investigate the ventilatory patterns of competitive rowers while rowing, we studied the pulmonary function of eight members of the University of Washington Women's Crew and one former member of the 1984 Women's Olympic Rowing Team on a rowing ergometer. Ventilatory performance of the oarswomen was compared both with their performance to exhaustion on a cycle ergometer and with the ventilatory response of six untrained controls on a rowing and a cycle ergometer. We found rowing elicited a higher ventilatory response in both the oarswomen and controls in submaximal and maximal work loads (P less than 0.001). Both oarswomen and controls had higher maximal breathing frequencies when rowing compared with cycling [rowers, 54.7 +/- 1.9 vs 49.8 +/- 0.09 (SE) breaths/min, P less than 0.05; and controls, 53.6 +/- 2.5 vs. 49.2 +/- 4.7, P less than 0.05] and lower maximal tidal volumes (rowers, 1.94 +/- 0.12 vs. 2.21 +/- 0.09 liters, P less than 0.01; controls, 1.59 +/- 0.09 vs. 1.68 +/- 0.19, difference not significant). Both oarswomen and controls were more hypocapnic while rowing compared with cycling (rowers, P less than 0.001; controls, P less than 0.02), although oarswomen were less hypocapnic while rowing than nonrowers (P less than 0.03). These results indicate that rowing causes hyperventilation with a higher breathing frequency and lower tidal volume. This alteration of pattern is possibly secondary to a change in mechanics, which possibly arises from the generation of high exercise ventilation in a variable seated position.     

内蒙古汉族、蒙古族与日本学生身高和体质量的最大发育年龄段差异

分析2014年7-18岁内蒙古汉族、蒙古族和日本学生身高及体质量最大发育年龄差异。汉族和蒙古族数据来自《2014年内蒙古自治区学生体质与健康调查研究》;日本数据来源于"平成26年(2014年)度体育与运动调查统计情报"。结果显示:7-18岁各年龄段汉族男女生身高分别比蒙古族高出1.98 cm和1.54 cm;高出日本2.59 cm和2.91 cm(P<0.05)。汉族男生体质量平均高出蒙古族1.97 kg、高出日本4.01 kg;汉族和蒙古族女生体质量分别比日本高出2.59 kg(P<0.05)和2.67 kg(P<0.05)。2014年内蒙古汉族和蒙古族学生身高和体质量发育水平优于日本学生。汉族男生身高最大发育年龄分别提前蒙古族和日本1.73岁和0.9岁;汉族和蒙古族男生体质量最大发育年龄分别比日本滞后1.17和1.07岁;日本女生身高最大发育年龄比汉族和蒙古族提前0.68岁和0.37岁。     

Seasonal changes in performance and free testosterone: cortisol ratio of elite female rowers

The aim of this study was to investigate the seasonal behaviour of the plasma free testosterone: cortisol ratio (FTCR) and to relate hormonal changes to daily training volume and performance parameters on a rowing ergometer in elite female rowers. During 9 months of training preceding the 1988 Olympic Games the resting values of the FTCR in six elite female rowers were regularly (ten times) studied. Daily training volume was analysed in terms of rowed distance (l _rowad) and time (t). In addition, two performance parameters, the power at 4.0 mmol·l^–1 lactate concentration in the blood and the maximal power, were determined by a test on a rowing ergometer. The results indicated that the mean FTCR test value did not differ significantly from the level of the initial test or from the mean value of the directly preceding test. A significant negative correlation (r=–0.98, P<0.01) between FTCR and l _rowed was found in a period i.e. at a training camp, when there was a sudden increase in training volume. When FTCR was related to t a significant positive correlation (r=0.88, P<0.05) was found only for the period at the training camp. Our data further suggested that the FTCR alone was not an adequate indicator for the anabolic/catabolic balance in elite female rowers. This finding was contrary to previous findings in elite male rowers. However, in training practice the FTCR seems useful as an indicator of the hormonal training status of elite female rowers when complemented with data about total and free testosterone, performance parameters and knowledge concerning cyclic variations of the FTCR.Both departments co-operate in the working group Janus Jongbloed Research Centre, Utrecht, The Netherlands     

Accounting for elite indoor 200 m sprint results

Times for indoor 200 m sprint races are notably worse than those for outdoor races. In addition, there is a considerable bias against competitors drawn in inside lanes (with smaller bend radii). Centripetal acceleration requirements increase average forces during sprinting around bends. These increased forces can be modulated by changes in duty factor (the proportion of stride the limb is in contact with the ground). If duty factor is increased to keep limb forces constant, and protraction time and distance travelled during stance are unchanging, bend-running speeds are reduced. Here, we use results from the 2004 Olympics and World Indoor Championships to show quantitatively that the decreased performances in indoor competition, and the bias by lane number, are consistent with this 'constant limb force' hypothesis. Even elite athletes appear constrained by limb forces.     

Plyometric jumping performances of male and female gymnasts from different heights

The objective of this study was to investigate and compare the factors influencing plyometric jumping performance between well-trained gymnasts and a control group. Seventy-six gymnasts and 91 moderately active subjects volunteered to participate in this study. Drop jumps (DJ) were performed from 20-, 40-, 60-, 80-, and 100-cm heights. Flight time (FT) and contact time (CT) were recorded using contact mat. Flight time to contact time (FC) ratio and Bosco expression (BE) were calculated. Male gymnasts scored similar FT to their controls, whereas female gymnasts had significantly longer FT compared with their peers. The gymnasts obtained significantly shorter CT than their control groups, whereas their FC ratios were significantly higher and increased when the height of the drops was close to 60 cm. Moreover, gymnasts' BE was greater in comparison to their respective control groups independent of the drop height. The height of the drop that produced the best FC ratio and BE varied between the groups. The best performances were obtained between 40- and 60-cm drop height for both groups. Female control group showed a trend toward a continuing decline with the increase of the drop height. The best gymnasts (finalists at World Championships) obtained their best performance at 80-cm drop. Flight time is the less discriminating factor distinguishing gymnasts' DJ performances. Considering CT, FC, and BE results all together could better profile the gymnasts rather than taken separately. Bosco expression was shown to be more sensitive to the increase in FT; we suggest BE as the best criteria to assess the appropriate drop height for plyometric training purposes in gymnasts as it has been significantly correlated to FT.     

Secular trend in body size among college athletes.

Height and weight were compared across five birth decades (1850-1899) among 1,121 Harvard athletes who were lettermen in various sports. There were considerable differences in the magnitude of the secular trend among the sport categories (crew, baseball, football, track, ice hockey, and two or more sports). Comparing the 1890-1899 and 1860-1869 birth-cohort samples, football lettermen were 2.6 inches (6.6 cm) taller (p less than 0.001) and 20 pounds (9.1 kg) heavier (p less than 0.001). Crew lettermen were 2.6 inches taller (p less than 0.001) and 8.5 pounds (3.9 kg) heavier (p less than 0.05). For lettermen in other sports, changes in mean height and weight were smaller in magnitude. Differential selection for body size may explain the differences in the magnitude of the secular trend when analyzed by specific sport.     

A survey on growth and sexual development of adolescent students in Changhua City: growth of body height and weight

In order to understand the physical growth and sexual development of contemporary adolescents, a cross-sectional survey was conducted during the period September 1983 to May 1984. The population came from all the pupils from 4th grade up, and all the junior and senior high students of Changhua City. By using stratified cluster sampling, 1419 boys and 1599 girls participated, ranging in age from 8 to 19 years. Body weight and height were measured. Growth spurt is a unique event during adolescence. It is well shown in the distance curves and pseudo-velocity curves of body height and weight. In boys, the growth spurt of height spanned from 12.0 to 14.8 years, with peak height velocity (PHV) at 13.5 years. In girls it was from 10.0 to 12.6 years and peaked at 11.5 years. The growth spurt of weight occurred from 12.0 to 15.9 years in boys with peak weight velocity (PWV) at 14.5 years, while girls had a growth spurt at 10.0-12.7 years with PWV at 11.5 years. Girls entered into the growth spurt about 2 years earlier, and also entered into PHV, PWV, two and three years earlier respectively than boys, while boys had a more intense and longer growth during the growth spurt than girls. Between 10.0-13.0 years girls were taller than boys, and between 12.0-13.0 years they were heavier than boys. However, from 13.5 years onward girls were soon surpassed by boys both in height and weight. Growth in height after 16.5 years in boys and after 15.5 in girls was minimal. Growth in weight in boys also became minimal after 16.5 years while girls weight even dropped a little bit after 16.5 years. At the mean age of 17.5 years, boys were 168.1 cm, girls were 156.2 cm in average, boys being 12 cm taller than girls after reaching their final height.     

Sport for tall.

Eight new events (handball, basketball, and six rowing events) were introduced for women in the Olympic Games at Montreal in 1976. Of 187 women rowers who competed at Montreal, none was shorter than the mean height (162 cm, 64 in) of women aged 18-24 in the United States. In team events only two out of 250 participants were shorter than the reference mean. Even among the tall, it was the taller participants who won medals. What does the slogan "Sport for All" mean in this context? Moreover, the physical size required of champion rowers and basketball players is not to be found in some Asian, African, and Latin American populations. International contests in many such events therefore seem to be at variance with the first charter of the Olympic Games. An independent reviewing body is urgently needed to examine the merits of man made rules in many sporting contests.     

Recent growth of children in the two Koreas: A meta-analysis

Height differences between the two Koreas were injected into the U.S. presidential debate. The purpose of this article is to report briefly the height, weight, and body mass index (BMI) differences between North and South Korean children by using previous sources and new data. This study employs South Korean data published by the Korean Research Institute for Standards and Science in 1997 and by the Korean Agency for Technology and Standards in 2004, comparing them to North Korean data stemming from the 1997 and 2002 nutritional surveys conducted by the United Nations. Furthermore, this article makes use of anthropometric measurements of North Korean refugee children immigrating to South Korea from 2000 to 2007. In 1997, South Korean preschool children were found on average to be 6-7 cm (2-3 in.) taller and about 3 kg (6.6 pounds) heavier than their Northern counterparts; in 2002, the average gap was about 8 cm (3 in.) and 3 kg (6.6 pounds), and the BMI gap was about 1. North Korean boys and girls escaping to South Korea were also found to be on average about 3-4 cm (1-1.6 in.) shorter and 1 kg (2.2 pounds) lighter than their Southern peers.     

Investigation of readiness and perceived workload in junior female basketball players during a congested match schedule

This study aimed to: a) investigate the differences in workload and readiness between two junior female national basketball teams competing at different European Championships (EC); b) compare workload, readiness and match performance for players with longer and shorter playing times, and; c) examine the relationship between workload, readiness and match performance variables. Under-18 (U18) (n = 10, height = 179.9 ± 6.6 cm, body mass = 70.2 ± 5.1 kg) and under-20 (U20) female national basketball teams (n = 11, height = 178.4 ± 8.8 cm, body mass = 73.0 ± 9.7 kg) were monitored during congested match schedules encompassing 7 matches within 9 days. Daily workload was determined via the session rating of perceived exertion (sRPE workload); readiness was measured by heart-rate variability (HRV) and well-being (WB); and match performance was assessed using the efficiency statistic and playing time. Analysis of workload and readiness during the EC showed no statistically significant between-team differences in any variables except WB for the U18 team, which was lower on Day 8 compared to the U20 team (p = 0.03; effect size [ES] = large). Players accumulating longer playing time showed a higher sRPE workload (p = 0.01, ES = moderate) and efficiency statistic (p = 0.04, ES = moderate) while no readiness variable differed significantly (p > 0.05) compared to players with shorter playing time. Trivial-to-small correlations were observed between workload, readiness and match performance variables. The study shows that junior female basketball players were able to cope with a congested schedule of 7 matches in 9 days irrespective of the competition context or individual differences in workload. Finally, combining objective and subjective methods to assess workload and readiness is recommended due to the weak relationships observed between these methods.     

Digit ratio (2D:4D) and rowing ergometer performance in males and females

Fetal and adult testosterone may be vital in the establishment and maintenance of sex-dependent abilities associated with male physical competitiveness. It has been shown that digit ratio (2D:4D) is negatively associated with prenatal testosterone, and it is also negatively associated with ability in sports such as football, skiing, middle distance running, and endurance running, which are dependent upon an efficient cardiovascular system. The relationship between digit ratio and sports requiring high power (physical strength) output in addition to well-developed cardiovascular systems has not been defined. This study investigated this association in male and female young adult rowers. Participants (77 male and 70 female) were student rowers encompassing a range of abilities from the University of Cambridge. Bilateral digit measurements were taken blind from each subject using Mitutoyo vernier calipers. Rowing performance over 2,000 m was assessed using the Concept 2 rowing ergometer. Significant negative correlations were observed between 2,000 m ergometer performance and male digit ratios, which persisted following adjustment for rowing experience and height. However, no such significant association was found in females despite a comparable sample size. Our data indicate that digit ratio is a predictor of ability in rowing, a sport which requires both cardiovascular efficiency and high power output, in males but not females. This in turn suggests that fetal testosterone exposure has long-term effects on traits associated with physical power in males but not females, suggesting a sex-difference in the capacity to respond to such exposures.     

The Electrophoretic Mobility of Cell Nuclei (EMN) index and changes in acid-base homeostasis under conditions of the intensive physical exercise

The relationship between the Electrophoretic Mobility of Cell Nuclei (EMN) index before and after super-maximal and maximal exercises and changes in physiological parameters associated with acid-base balance of the blood (pH, BE) and lactic acid concentration (LA) were examined in junior (N = 33, X = 15.6 y.o. SD = 1.16 y.), and senior (N = 10, X = 22.0 y.o. SD = 2.70 y.) female rowers. The following parameters: pH, BE and LA changed significantly (p < 0.05) from pre- to post-exercise status, while the EMN index changed only in junior female rowers under super-maximal conditions. Correlations between the EMN index and physiological parameters reflect the homeostatic disturbance associated with intensive exercise conditions. The decline in the EMN index appears to depend on the post-exercise changes of an organism's acidity. The results suggest that changes in the EMN index are associated with variation in physiological parameter, i.e. changes in acidity. We conclude that the EMN index reflects acid-base alterations and may be useful in evaluating systematic reactions to stress.     

Investigation of the kinetics of anaerobic metabolism by analysis of the performance of elite sprinters

The principal motivation for the present work was the study of the kinetics of anaerobic metabolism. A new mathematical model of the bioenergetics of sprinting, incorporating a three-equation representation of anaerobic metabolism, is developed. Results computed using the model are compared with measured data from the mens' finals of the 100m event at the 1987 World Championships. The computed results closely predict the overall average performance of the competitors over the course of the entire race. Further calculations show the three-equation model of anaerobic metabolism to be a significant improvement over the previous one-equation model. Representative values of time constants that govern the rate of anaerobic energy release have been determined for elite male athletes. For phosphocreatine utilisation, values for lambda(2)=0. 20s(-1) and psi(2)=3.0s(-1) are consistent with data previously reported in the literature. New values of lambda(3)=0.033s(-1) and psi(3)=0.34s(-1) are proposed as offering an improved representation of the kinetics of oxygen-independent glycolysis. For the first time, tentative values for the time constants of ATP utilisation, lambda(1)=0.9s(-1) and psi(1)=20s(-1), are suggested. The maximum powers developed during sprinting by oxygen-independent glycolysis, PCr utilisation and endogenous ATP utilisation were calculated as 34. 1, 30.1 and 16.6Wkg(-1), respectively, with an overall maximum anaerobic power of 51.6Wkg(-1). Sample calculations show the mathematical model can be used in principle to derive data on the kinetics of anaerobic metabolism of individual athletes.     

A kinetic and kinematic analysis of the Harai-goshi judo technique

The purpose of this study was to analyze and compare the kinetic and kinematic characteristics of the throwing technique, Harai-goshi of novice and advanced judo competitors. A heterogeneous group of 28 male and female judo competitors participated in this study. Each subject was required to perform three successful trials. Kinetic and kinematic data were collected by utilizing the Kistler Instrument Corporation Multicomponent Force Measuring Platform System and the Peak Technologies Motion Video Analysis System. Data were collected in order to quantitatively and qualitatively analyze the horizontal and vertical forces of the support leg, and the horizontal and vertical velocities of the sweeping leg during execution of the throwing technique, Harai-goshi (hip sweep). The study revealed a significant difference in horizontal force application, between novice and advanced judo competitors. In addition, we found numerous significant relationships among mean horizontal ground reaction force application and horizontal leg sweep velocity in 19 of the 28 participants when analyzed individually. The results suggest (1) leg sweep velocity is a function of ground reaction force application; and (2) horizontal leg sweep velocity plays a primary role in good technical execution of the Harai-goshi throw.     

Effect of prolonged training period on plasma adiponectin in elite male rowers.

Adiponectin is secreted by adipocytes and has been implicated in the regulation of energy homeostasis. Vigorous training program represents a physical stress condition in which heavy changes in energy expenditure might increase adiponectin concentration in athletes. Therefore, the aim of the present study was to investigate if there are changes in fasting adiponectin concentration during preparatory period in elite male rowers. Twelve rowers (mean and SD; age: 20.8+/-3.0 years; height: 192.9+/-4.7 cm; body mass: 91.9+/-5.3 kg; body fat percentage: 11.9+/-1.4%) were tested seven times over a 24-week training season. In addition to adiponectin, leptin, insulin, growth hormone, and glucose values were evaluated. Maximal oxygen consumption (VO (2 max)) and aerobic power (Pa (max)) were determined before and after the training period. Training was mainly organized as low-intensity prolonged training. Significant increases in VO (2 max) (by 3.2+/-1.8%; from 6.2+/-0.5 to 6.4+/-0.4 l/min), VO (2 max/kg) (by 2.2+/-2.0%; from 67.9+/-3.0 to 69.4+/-3.0 ml/min/kg) and Pa (max) (by 4.6+/-6.3%; from 444.6+/-39.1 to 465.8+/-25.0 W) were observed after the 24-week period. All measured body compositional values were similar to pretraining values after the training period. Fasting adiponectin did not change during the preparatory period. Likewise, leptin, insulin, growth hormone, and glucose values were not significantly changed after the training period. Adiponectin concentration was significantly correlated (all p<0.05) with body mass (r=-0.40), body fat mass (r=-0.33), body fat free mass (r=0.38), and leptin (r=-0.31) values. In conclusion, fasting adiponectin does not change throughout the prolonged training period in elite male rowers despite substantial changes in training volume. Further studies are needed to clarify possible mechanisms by which adiponectin might influence energy homeostasis during heavy training in elite athletes.     

SEX DIFFERENCES IN BODY SIZE AND BODY CONDITION OF CALIFORNIA SEA LION (ZALOPHUS CALIFORNIANUS) PUPS FROM THE GULF OF CALIFORNIA

The Gulf of California harbors about 15% of the total California sea lion ( Zalophus californianus californianus ) population. We studied pup morphometrics from eight Gulf of California rookeries during the 1996 and 1997 reproductive seasons to describe sex differences in body size and body condition indices. Newborn pup body size was not different from previous reports. Male pups were heavier and larger than female pups in terms of all linear dimensions. Morphometric relationships, however, showed that males were 3%-4% denser, and that after removing the effects of length, they were about 2% heavier than females. Sculp depth adjusted for length was 12% larger in female than in male pups. Our data provide further evidence that male otariid pups may allocate a larger fraction of milk energy to muscular and skeletal growth compared to female pups.