Contributions of strength and body composition to the gender difference in anaerobic power.

BACKGROUND: The purpose of this study was to determine the significant factors contributing to the difference between men and women in anaerobic power (AP) generation. METHODS. PARTICIPANTS: College men (n = 113) and women (n = 175) were randomly selected for evaluation from a fitness class prior to training. MEASURES: AP was determined from the Margaria-Kalamen stair run. Dynamic strength was evaluated from the 1-RM single-leg extension. Body composition was estimated from gender-specific skinfold prediction equations. RESULTS: Discriminant analysis identified %fat, fat-free mass (FFM), and leg extension strength as significant components differentiating between men and women and allowed proper gender classification in 99% of the cases. When both strength and body composition variables were held constant by covariance, there was no significant difference between men and women in AP (F = 1.25). A multiple regression equation using %fat, FFM, and leg extension strength predicted AP (R = 0.91) with an error of 150 W. When the multiple regression equations was applied to a cross-validation sample, AP could be accurately predicted (r = 0.91, t = 0.17) with an average error of 3% +/- 21%. CONCLUSIONS: Body size and dynamic strength are the major factors explaining the explosive leg power difference between men and women without a specific or unique gender quality.

Intra-abdominal pressure and rowing: the effects of inspiring versus expiring during the drive.

BACKGROUND: The lumbar vertebrae of rowers are subjected to high levels of shear and compression at mid-drive, but intra-abdominal pressure (IAP) may partially neutralize these forces. IAP fluctuates with breathing. This study compared the IAP between inspiring during the drive and expiring during the drive. EXPERIMENTAL DESIGN: ten volunteers performed one 5x2-minute repetition test while inspiring during the drive and one 5x2-minute repetition test while expiring during the drive on a rowing ergometer. The five work rates were: 100, 125, 150, 175 and 200 watts at 22, 24, 26, 28 and 30 strokes per minute, respectively. MEASURES: the movement of the body while rowing was analyzed using a position sensor, and IAP was measured using a pressure transducer catheter. RESULTS: A 2x5 repeated measures analysis of variance showed that there was a significant interaction for the dependent variable mid-drive IAP (p<0.05), with the mid-drive IAP increasing at a greater rate while expiring during the drive relative to inspiring during the drive. Across work rate, the mid-drive IAP and minimal IAP were significantly higher while expiring during the drive than inspiring during the drive (p<0.05). Across breathing pattern, the minimal IAP, maximal IAP, average change in IAP and mid-drive IAP increased significantly with work rate (p<0.05). CONCLUSIONS: The data show that expiring during the drive leads to a greater mid-drive IAP than inspiring during the drive.

Physiologic responses to forward and retrograde simulated stair stepping.

This study compared the physiologic responses to forward and retrograde simulated stair stepping on the StairMaster 4000 PT. Twenty male subjects (mean age 23.65 +/- 1.63 years) volunteered for this study. Subjects completed a practice trial of 6 minutes of both forward and retrograde stepping at Level 5. Each experimental trial was divided into four 3-minute stages: Level 3, Level 5, Level 7, and Level 9. Heart rate, blood pressure, and rating of perceived exertion (RPE) were recorded during the second minute of each stage. Expired gases were analyzed and averaged over the last 2 minutes of each stage. Caloric expenditure and delta efficiency were later calculated. Data were analyzed using a 2 x 4 ANOVA (direction by level) and 2 x 3 ANOVA (for delta efficiency). Compared to forward responses, retrograde heart rates were significantly higher at Levels 7 and 9 (p < 0.01). Retrograde responses for RPE, metabolic equivalents (METS), and caloric expenditure were significantly higher at (p < 0.01) Levels 5, 7, and 9 when compared to forward responses. However, the results of this study show that these differences between forward and retrograde stepping are not practically meaningful.

The relative contribution of strength and physique to running and jumping performance of boys 7-11.

The purpose of this study was to determine the association of static strength with motor performance of 7 through 11 year old boys (N = 60) after accounting for differences in physique, i.e., body size, shape, and composition. Static strength measures included thigh extension, leg extension and plantar flexion measured by electronic transducer and back lift, leg lift, and right and left grips measured by spring dynamometer. Measures of body composition consisted of fat estimated from triceps, subscapsular and calf skinfolds, and fat-free body weight estimated from potassium-40 measurements. Body structure consisted of skeletal widths, and segment girths, lengths and volumes. The dependent variables were vertical jump, standing broad jump, 50-yard dash, 600-yard run and mile run. The measures of strength increased the variance accounted for from 10 to 23% over that when body size, composition and structure were used without strength. An exception was vertical jump where no increase in the variance accounted for was found with the addition of strength variables. The regression equations determined for the sample of 60 boys rendered multiple R's ranging from 0.64 (mile run) to 0.75 (50-yard dash). It was concluded that strength has a significant relation to motor performance and that its contribution can be better assessed after accounting for differences in body size, shape, and composition.

Biological and performance variables in relation to age in male and female adolescent athletes.

To observe the cross-sectional nature of the effect of age, height, and body mass on motor performance during adolescence (13-18 years), 103 boy and 65 girl athletes were measured for motor performance and anthropometric variables. Motor performances included tests of strength, muscular endurance, flexibility, aerobic capacity, anaerobic power, speed, and agility. Anthropometric determinations included height, body mass, lean body mass, %fat, and somatotype. Boys were significantly different from girls in all measurements except endomorphy, while girls were significantly superior to boys only in flexibility. Physical maturation, as reflected by height and body mass, was a major contributor to increases in motor performance. Somatotype did not differ greatly across the age groups. Boys were significantly more mesomorphic than girls, while girls were significantly more ectomorphic than boys. Higher %fat and more endomorphy were significantly related to poorer performance for relative aerobic capacity, 40-yd dash, and agility in boys but only for upper body muscular endurance in girls. Mesomorphy had higher relationships with performance variables among boys than among girls. Growth would appear to contribute significantly to enhanced motor performance with age, and its effect may be different in boys than in girls.

Relationships of structural dimensions to bench press strength in college males.

The purpose of this study was to determine the relationships between structural dimensions and bench press performance in college males. Members of required fitness classes (n = 170) were measured after 14 weeks of strength and aerobic endurance training. Anthropometric dimensions included upper arm and chest circumferences, upper and lower arm lengths, shoulder and hip widths, %fat, and height. Arm muscle cross-sectional area (CSA) was calculated from upper arm circumference corrected for triceps skinfold. Drop distance was measured from the bar to the pectoral muscles. Multiple regression analysis selected upper arm CSA, %fat, and chest circumference as the best items to predict bench press strength (R = 0.83; SEE = 11.6 kg). Cross-validation of the prediction equation on a similar sample (n = 89) produced an r = 0.74 between predicted and actual bench press (t = 0.53, p greater than 0.50). In a second cross validation sample (n = 57) who had trained more extensively with weights, the correlation between predicted and actual bench press was r = 0.57 (p less than 0.05). The prediction equations significantly (t = 6.59, p less than 0.01) underestimated bench press performance in the more extensively weight trained subjects. The results of this study suggest that bench press performance is related to structural dimensions in males and that extensive strength training may alter the relationship between size and strength.

Sex differences in static strength and fatigability in three different muscle groups.

Maximal voluntary static muscle force production was assessed both in strength trials and during 2-min contractions by three muscle groups (right-hand finger flexors [RHF], right-leg extensors [RLE], and both leg extensors [BLE]) in young males (n = 13) and females (n = 14). There was a significant difference (p less than .01) between males and females for RHF strength and BLE strength but no significant difference between sexes for RLE strength. During the 2-min task, impulse (force x time) declined significantly (p less than .001) and there was a significant difference (p less than .001) between muscle groups, but there was no difference between sexes. There was a significant (p less than .05) sex x time interaction for the impulse values indicating that the fatigability was greater in males than females.

Cardiovascular response to sustained maximal voluntary static muscle contraction.

The cardiovascular response to maximal, voluntary, sustained 2-min static contraction by three different muscle groups (right hand finger flexors [RHF], right leg extensors [RLE], and both leg extensors [BLE]) was studied in young adult males (N = 13) and females (N = 14). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were recorded at 30 s intervals prior to, during, and after exercise. Mean arterial blood pressure (MABP) and pulse pressure (PP) were computed from SBP and DBP. The force of muscle contraction was monitored continuously throughout the 2-min task. Data were analyzed by MANOVA. The results showed that impulse (force x time) declined significantly throughout exercise, and there were significant differences in impulse among muscle groups. SBP, DBP, PP, and MABP increased significantly throughout the 2-min contraction period, while heart rate increased initially and then leveled off. The magnitudes of the blood pressure and HR responses were related to the muscles involved: BLE greater than RLE greater than RHF. Blood pressures during rest and exercise were significantly lower for females than for males, but there was no sex effect for heart rate. These findings suggest that blood pressure increases throughout sustained static muscular contractions despite significant reductions in force production. Heart rate, on the other hand, does not increase throughout exercise under these conditions. It appears that heart rate and blood pressure responses to sustained static contraction are mediated by different mechanisms, but these mechanisms are similar for males and females.

Factors affecting anaerobic power output in the Margaria-Kalamen test.

The purpose of this study was to determine the effect of three approach distances and two vertical ascent methods on approach velocity, vertical velocity and power output of the Margaria-Kalamen test. Male (n = 43) and female (n = 53) university students were tested using a traditional and a modified (ramp) Margaria-Kalamen test with approaches of 2, 6 and 10m. The average of five trials for each approach distance was used to calculate anaerobic power. Males averaged 14.0% greater approach velocity, 28.8% greater vertical velocity and 41.1% greater power output than females, regardless of approach distance or vertical ascent method. Anaerobic power output was not significantly different between the sexes for any method when the effects of the percentage of fat and lean body mass were removed by the covariance technique. The 2m approach produced significantly slower approach velocity, vertical velocity and power output than the other approaches. The ramp method resulted in significantly greater approach velocity (11.5%), vertical velocity (9.6%) and anaerobic power output (9.4%) than the stair method. Males averaged 8.4% higher power output using the ramp, while females averaged 11.0% higher than the conventional stair method. Females appeared to benefit more than males from using a ramp in the anaerobic power test. Anaerobic power measurement from the Margaria-Kalamen method can be maximized using a ramp method.