Training college-age women to perform the pull-up exercise.

The purpose of this investigation was to determine the effect of a combined strength and aerobic conditioning program on the ability of college-age women to perform the pull-up exercise and to identify the characteristics of women successful in performing a pull-up at the end of the program. Participants significantly increased upper body strength and fat-free mass and deceased fat mass and percentage of body fat. Participants successful at performing a pull-up had significantly greater 1 repetition maximum strength, strength to mass ratio, and strength to fat-free mass ratio. A two variable equation (% body fat and strength to fat-free mass ratio) was developed to predict which women would be successful at completing a pull-up at the end of a similar training program.

Modeling a two-mile run age and body weight handicap for men and women.

PURPOSE: To develop a weight and age handicap model for Two-Mile Run Test (2MRT) performance for adult men and women using dimensional analysis and recent empirical data. METHODS: Models of the body composition- and physical activity-adjusted effect of age on VO2max and the allometric model of body size and 5 K run time for men and women (adjusted for the 2MRT distance) were employed. RESULTS: Two tables were developed, one for each gender. Each provides a simple index (sec) of run time based on body weight and age, that are subtracted from actual 2MRT time to yield adjusted run time. CONCLUSION: Such a handicap model, which grants a handicap based only on the independent effects of age and weight (not fatness or lack of physical conditioning, for example), is the first to be based on physiologically sound theory and empirical data. It may prove useful for military fitness testing particularly in situations where higher achievement is rewarded and/or control for age and weight differences in warranted.

The backpack run test: a model for a fair and occupationally relevant military fitness test.

Our purpose in this investigation was to develop and validate a theoretical model for a backpack run test based on how fast one can run 2 miles while wearing a backpack. Using actual unloaded (no backpack) 2-mile-run test data from 59 male service academy cadets, we calculated the average oxygen cost during the run, the equivalent cost if wearing additional weight, and the corresponding estimated run time with the backpack. The correlations between body weight and loaded (backpack weight = 30 kg) run times (r = 0.55 [p < 0.05] and r = 0.12 [p > 0.05], respectively) demonstrate that the bias against heavier runners is eliminated with the backpack run. Given that the backpack run test requires only standard-issue equipment, demonstrates clear occupational and health-related fitness relevance, predicts no apparent body-size bias, and measures work- and health-related components of fitness, we recommend that the military services consider the present data when developing or modifying tests of physical fitness.

Cardiovascular fitness in premenarcheal girls and young women.

Maximal oxygen uptake (VO2max) in females, expressed as ml x kg(-1) x min(-1), declines steadily during the first three decades of life. The contribution of diminished cardiovascular function to this apparent fall in aerobic fitness is unknown. Cardiac responses to maximal cycle exercise were compared in 24 premenarcheal females (mean age 11.7 years) and 17 young adult women (mean age 27.4 years) using Doppler echocardiography. Mean VO2max was 40 ml x kg(-1) x min(-1) and 34.7 ml x kg(-1) x min(-1) in the girls and women, respectively (p < 0.05). When VO2max was expressed relative to allometrically-derived mass(0.52), however, no significant difference was observed in aerobic fitness between the two groups. Similar allometric analyses revealed no significant differences in average maximal cardiac output (10.50 vs 10.07 L x min(-1) BSA(-1.11) for girls and women, respectively) nor maximal stroke volume (53 vs 56 ml BSA(-1.13) respectively). These findings suggest that 1) allometric scaling is important in eliminating the effects of body size on VO2max, 2) body dimension differences can account for variations in VO2 in young females, and 3) cardiac functional reserve is similar in premenarcheal girls and young adult women.

Considering body mass differences, who are the world's strongest women?

PURPOSE: Allometric modeling (AM) has been used to determine the world's strongest body mass-adjusted man. Recently, however, AM was shown to demonstrate body mass bias in elite Olympic weightlifting performance. A second order polynomial (2OP) provided a better fit than AM with no body mass bias for men and women. The purpose of this study was to apply both AM and 2OP models to women's world powerlifting records (more a function of pure strength and less power than Olympic lifts) to determine the optimal model approach as well as the strongest body mass-adjusted woman in each event. METHODS: Subjects were the 36 (9 per event) current women world record holders (as of Nov., 1997) for bench press (BP), deadlift (DL), squat (SQ), and total (TOT) lift (BP + DL + SQ) according to the International Powerlifting Federation (IPF). RESULTS: The 2OP model demonstrated the superior fit and no body mass bias as indicated by the coefficient of variation and residuals scatterplot inspection, respectively, for DL, SQ, and TOT. The AM for these three lifts, however, showed favorable bias toward the middle weight classes. The 2OP and AM yielded an essentially identical fit for BP. CONCLUSIONS: Although body mass-adjusted world records were dependent on the model used, Carrie Boudreau (U.S., 56-kg weight class), who received top scores in TOT and DL with both models, is arguably the world's strongest woman overall. Furthermore, although the 2OP model provides a better fit than AM for this elite population, a case can still be made for AM use, particularly in light of theoretical superiority.

Validation of the Wilks powerlifting formula.

PURPOSE: Because maximal strength varies with body mass, the International Powerlifting Federation (IPF) has adopted a method of adjusting powerlifting events (bench press, BP; squat, SQ; deadlift, DL, and total lift (the sum of BP, DL, and SQ), TOT) by body mass. This method, the Wilks formula, multiplies one's lift by an index based on body mass so that lifters of different size can be compared on the same event. The Wilks formula is not, however, based on published data and has yet to be critically evaluated. The purpose of this investigation, then, was to validate the Wilks formula. METHODS: This was performed by 1) examining residuals bias to verify that the adjusted score does, in fact, lead to no systematic bias based on body mass and 2) by applying a more theoretically supportable allometric model to the same data and comparing the fit with the Wilks approach. Subjects were the current men's and women's world record holders as well as the top two performers for each event in the IPF's 1996 and 1997 World Championships (a total of 30 men and 27 women for each lift). RESULTS: Results of data analysis regarding the Wilks formula indicate that: 1) there is no bias for men's or women's BP and TOT; 2) there is a favorable bias toward intermediate weight class lifters in the women's SQ with no bias for men's SQ; and 3) there is a linear unfavorable bias toward heavier men and women in the DL. Furthermore, the allometric approach indicated a bias against light and heavy men and women which may be considered acceptable given that half as many lifters are found in the lightest and heaviest weight classes as in the intermediate weight classes. CONCLUSION: As used currently (BP and TOT only), the Wilks formula appears to be a valid method to adjust powerlifting scores by body mass.

Modeling the influence of body size on V(O2) peak: effects of model choice and body composition.

This study examined the bivariate relationship between peak oxygen uptake (V(O2) peak); l/min) and body size in adult men (n = 1,314, age 17-66 yr), using both "simple" and "full" iterative nonlinear allometric models. The simple model was described by V(O2) peak = M(b) (or FFM(b)) exp(c SR-PA) exp(a + d age) epsilon (where M is body mass in kg; FFM is fat-free mass in kg; SR-PA is self-reported physical activity; epsilon is a multiplicative error term; and exp indicates natural antilogarithms). The full model was described by V(O2) peak = M(b) (or FFM(b)) exp(c SR-PA) exp(a + d age) + e (epsilon), where e is a permitted Y-intercept term. The M exponent obtained from simple allometry was 0.65 [95% confidence interval (CI), 0.59-0.71], suggestive of a curvilinear relationship constrained to pass through the origin. This "zero Y-intercept" assumption was examined via the full allometric model, which revealed an M exponent of 1.00 (95% CI, 0.7-1.31), together with a positive Y-intercept term (e) of 1.13 (95% CI, 0.54-1.73). The FFM exponents were not significantly different from unity in either the simple or full allometric models. It appears that the curvilinearity of the simple allometric model (using total M) is fictitious and is due to the inappropriate forcing of the regression line through the origin. Utilizing FFM as the body-size variable revealed a linear relationship between body size and V(O2) peak, irrespective of model choice. We conclude that the population mass exponent for V(O2) peak is close to unity.

Gender effects on submaximal energy expenditure in children.

Previous studies have suggested that submaximal energy expenditure relative to body mass during weight-bearing exercise may be greater in boys compared to girls. This two-part study examined a) gender-related five-year longitudinal changes in submaximal walking economy and b) gross, net, and delta muscle work efficiency during submaximal cycle exercise in a cross-sectional analysis of boys and girls. In the longitudinal study, the influence of pre-exercise metabolic expenditure, stride frequency, and substrate utilization (by RER) on changes in economy were examined. During the five years, mean VO2 per kg during submaximal treadmill walking (measured at 8% slope, 3.25 mph) decreased 16% in girls and 13% in boys (p > 0.05 for gender). Likewise, no significant gender differences were observed in decline of stride frequency over time. RER values were similar between sexes except in the final two years when girls had significantly greater values than the boys. No gender-related differences were observed in any measure of muscle work efficiency. This study failed to reveal significant gender differences in utilization of energy during submaximal exercise in children.

Impact of body size on women's military obstacle course performance.

The United States Military Academy uses an Indoor Obstacle Course Test (IOCT) to assess military-relevant physical fitness. There are both anaerobic and aerobic fitness components to this test. Recent attention has been focused on the apparent difficulty of heavier female cadets to succeed on the IOCT. The purpose of this study was to use allometric scaling to examine the effects of body weight (BW), fat-free mass (FFM), percent body fat (%BF), and fat mass (FM) on IOCT performance for female cadets. The sample included 38 female cadets who successfully completed the IOCT. Performance was defined by the time, T, to complete the entire course. FFM was determined via a three-site skinfold test. Allometric modeling was used to determine the exponent in the following index: T*BW2 such that the independent contributions of body size are partialled out. This analysis was used for all four independent variables simply by substituting BW with the other independent variables. The following exponents were found to be significant (p < 0.05): 0.45 +/- 0.13 for %BF and 0.24 +/- 0.12 for FM indicating that these independent variables play a significant role in female performance on the IOCT. For example, if a female cadet could decrease her %BF from 20% to 18%, which would be decrement of ten percent, then her estimated decrease in IOCT time is 4%. In addition, a trend (p = 0.06) was found for FFM meaning that as FFM increases, T decreases. We conclude that, among USMA female cadets, small decreases in %BF may be significantly advantageous to IOCT performance.

Gender differences in muscular strength: an allometric model approach.

Despite the fact that allometric modeling has been shown to be a more valid technique for group comparisons of body-size-adjusted muscular strength, no study to date has compared gender differences using absolute (no adjustment for body mass, BM), ratio (force/BM) and allometric (force/BMa) models for an active duty military population. Our purpose in this study was to use these models to compare gender differences in three strength tasks: maximal weight lifted to 152 cm height, maximal isometric force on an upright cable pull and maximal isometric handgrip force. Subjects were 989 and 987 active duty men and women, respectively, each of whom had fat-free mass (FFM) assessed hydrostatically. Results indicate that the ranges of gender difference in strength (%) were 57.9-103.7, 14.5-64.7 and 18.7-77.9 for absolute, ratio and allometrically scaled expressions, respectively, for BM and FFM. We conclude: 1. Men exhibit greater strength than women for all three indices regardless of model approach. 2. The magnitude of these differences is smaller when considering FFM rather than BM, but is larger when considering allometric vs. ratio models.

The influence of short-term aerobic training on blood lipids in healthy 10-12 year old children.

This study was designed to examine the ability an endurance exercise training program to alter blood levels of cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides in children. Thirty-one sixth grade students age 10-12 years (20 girls, 11 boys) who were healthy and active volunteered for participation. The training program consisted of 13 weeks of aerobic activities three days a week, 25 minutes per session, with training intensity assessed by heart rate monitors. Serum lipids and maximal oxygen uptake (VO2max) were measured at the beginning of a control period, 13 weeks later at the beginning of the training program, and at the termination of 13 weeks of training. VO2max values for the group improved 5.4%, but no significant changes were observed in any of the blood lipid levels between the control and training periods. These findings suggest that aerobic training of 13-weeks duration is not an effective means of altering blood lipids in healthy normolipemic children.

Ratio scaling of VO2max penalizes women with larger percent body fat, not lean body mass.

VO2max expressed in ml.BM-1.min-1 (BM = body mass) has been shown to unduly penalize heavier subjects and instead should be expressed as ml.BM-0.7.min-1. Such findings support the "theory of similarity" (TofS) that proposes the BM exponent should be 2/3 (0.67). The TofS, however, applies better to lean body mass (LBM) that is uninfluenced by fat mass. For young adults, the actual scaling exponent of LBM has yet to be satisfactorily determined. We used allometric scaling (AS) to scale VO2max by BM and LBM in 94 women (age = 27.4 +/- 6.7 yr, BM = 60.3 +/- 8.4 kg). Treadmill VO2max was assessed by indirect calorimetry and LBM was determined from hydrostatic weighing. AS yielded the following exponents (+/- 95% C.I.): BM: 0.61 +/- 0.27, and LBM: 1.04 +/- 0.26. We conclude that VO2max in ml.BM-1.min-1 indeed penalizes heavier women, but this penalty applies only to those who are heavier because of larger percent body fat, not LBM. If one takes the position that excess fatness is undesirable, then from a health and performance perspective, expressing VO2max in ml.BM-1.min-1 may provide an unbiased and useful expression of VO2max in young women.

Multivariate allometric scaling of men's world indoor rowing championship performance.

The World Indoor Rowing Championship (WIRC) is based on the time (T) to row a simulated 2500 m on a rowing ergometer. In the WIRC there are separate age categories but only two weight classes: light and heavyweight, thus penalizing those just heavier and those significantly lighter than the cut-off weight. Multivariate allometric scaling (MAS) provides an expression of performance free of the confounding effect of more than one scaling variable. We used MAS to scale T by height (H) and age (A) to create a new index of rowing performance, T*H(-a)*A(-b). Subjects were 148 male competitors from the 1995 WIRC. MAS indicated that T*H*A(-0.06) expresses T free of the confounding effect of H and A. We also scaled T only by H on those subjects, A < 40, (N = 109). Results showed that T*H is an optimal and particularly feasible scaling of T. Use of either convention dramatically changed race results. In conclusion, we recommend use of either the T.H (17 < or = A < or = 39) or T*H*A(-0.06) conventions to adjust WIRC performance in adult males.

Plasma norepinephrine responses to cycle exercise in boys and men.

Previous reports have suggested that plasma norepinephrine levels during exercise, an indicator of sympathetic neurologic activity, may be less in children than in adults. This study investigated plasma norepinephrine values at rest, during two submaximal cycle exercise intensities, and at maximal exercise in 11 boys aged 10 to 12 years and 11 men aged 24 to 35 years. Blood specimens were drawn at average submaximal exercise intensities of 58.7% and 73.0% for the boys and 55.3% and 73.3% VO2max for the men. Weight-relative maximal aerobic power was similar in the two groups. No statistically-significant differences were observed in plasma norepinephrine values at rest or during submaximal and maximal exercise between the boys and men. Maximal levels were 1196 (326 SD) and 1385 (612 SD) pg.ml-1 for the boys and men, respectively (p > 0.05). These findings suggest that sympathetic influences during maximal and submaximal exercise are independent of biological maturation.

Periodic carbohydrate replacement during 50 min of high-intensity cycling improves subsequent sprint performance.

The purpose of this study was to investigate the effect of 7% carbohydrate-electrolyte (CE) drink on sprint capacity immediately following 50 min of high-intensity cycling. After an overnight 12-hr fast, 8 trained male cyclists performed two 50-min simulated time trials on a Monark stationary cycle ergometer. Subjects consumed either the CE or a flavored water placebo (PL) at 10, 20, 30, and 40 min during the time trial. At the conclusion of each 50-min time trial, subjects immediately performed a Wingate Anaerobic Power Test. Peak power, mean power, and minimum power were significantly higher for the CE trials, whereas mean RPE was significantly lower. Mean heart rate and fatigue index were not different between trials. These results suggest that sprint performance following a high-intensity simulated time trial of only 50 min can be improved with periodic consumption of CE during the ride, particularly following an overnight fast, when liver glycogen is likely to be low. These findings have implications for competitive cycling, where sprint capacity at the conclusion of a race is an important determinant of success.

Ability of the Army Circumference Method to detect changes in subcutaneous fat over a 9-week period.

The Army Circumference Method (ACM), used to estimate percent body fat for soldiers, has been shown to have questionable validity as applied to women. This study's primary purpose was to examine the ability of this method to detect changes in subcutaneous fat over a 9-week period with men (N = 55) and women (N = 51) enrolled in a weight management program. Changes in percent body fat, based on the ACM, were correlated with the corresponding ones from the Jackson/Pollock skinfold method. Results indicated that the male ACM (r2 = 0.548) could more satisfactorily detect changes in subcutaneous fat than the female ACM (r2 = 0.135).

Fat distribution: its physiological significance, health implications, and its adaptation to exercise training.

Recently, fat distribution has become of clinical interest in assessing one's risk for coronary heart disease (CHD). Investigations have shown stronger relationships between abdominal, or central adiposity, and various well known risk factors for CHD, than peripheral and/or total adiposity. The simple waist-to-hip ratio, shown to be a valid index of such fat distribution, should be considered for use by professionals in military medicine in assessing one's risk for relevant diseases. Consideration must also be made of the role of exercise as an intervention in improving one's fat distribution profile.