Comparison of three methods of assessing strength imbalances at the knee.

Three strength measurement methods for determining muscle imbalances at the knee were compared in 24 male athletes. Peak quadriceps extensions and hamstring flexions were measured isotonically, isometrically, and isokinetically. Isokinetic measurement was performed at 60, 180, and 300 degrees /sec. Repeated measures ANOVA revealed no significant difference among the three methods for bilateral imbalance ratio measurement. However, hamstring/quadricep ratios were significantly greater when measured isokinetically than when measured by the other methods. It was concluded that strength measurement methods may be used interchangeably when determining bilateral strength imbalance ratios at the knee but they may not be used interchangeably when assessing hamstring/quadricep ratios. Determinations of excess imbalance ratios (>10%) showed no consistent pattern across methods and may indicate problems associated with attempts to identify safety limits from muscle testing.J Orthop Sports Phys Ther 1988;10(4):134-137.

Selection and classification of high school volleyball players from performance tests.

The purpose of this study were to determine the accuracy of general and specific tests for identifying the players on freshmen (FR), junior varsity (JV), and varsity (VR) teams and the precision of tests to differentiate between starters and nonstarters at each level of play. Fifty high school volleyball players were tested during the first week of practice for six general and four specific motor performance tests. The specific tests included the overhead volley, forearm pass, wall spike, and self bump/set test. The general tests included height, weight, percent body fat, agility run, vertical jump, and two flexibility maneuvers. VR players were significantly better in vertical jump, agility, and all specific ball-handling tests than FR and VJ players. The combination of forearm pass, overhead volley, vertical jump, and weight correctly classified 68% of the players to their team level. The combination of bump-set, height, weight, and shoulder flexibility allowed correct classification of 78% of the starters and nonstarters. General and specific tests can successfully select and classify high school volleyball players.

Anthropometric correlates with strength performance among resistance trained athletes.

The purpose of this study was to determine the relationship between selected anthropometric dimensions and strength performance in resistance trained athletes. Fifty-eight college football players were measured following the completion of a 10-week resistance training program for one-repetition maximum (1-RM) lifts in the bench press, squat, and dead lift and for 11 anthropometric dimensions. Results indicated that the highest relationships existed between estimates of regional muscle mass (arm circumference, arm muscle cross-sectional area, and thigh circumference) and lifting performance. Multiple regression analysis selected arm size and %fat as variables common to the prediction of all three lifts. The fewer joints and muscle groups involved in a lift, the greater the predictive accuracy from structural dimensions. It was concluded that body structure and conformation make significant contributions to maximum strength performance in highly trained strength athletes.

The influence of muscle group location and race on the relationship between muscle strength and power.

OBJECTIVE: This study investigated the influence of muscle group location and racial background on the relationship between measures of muscle strength and power. It was hypothesized that both African American (AA) and Caucasian American (CA) males would exhibit similar strength-power relationships, but these relationships would be dependent upon muscle group location. EXPERIMENTAL DESIGN: A cross-sectional, comparative design was used. SETTING: The Human Performance Laboratory at the U. of Oklahoma. SUBJECTS: Normal, healthy college-aged AA (n = 14) and CA (n = 15) males volunteered for this study. MEASURES: Upper and lower body strength (IRM) was assessed using a Smithpress bench press and Polaris leg press, and upper and lower body power was measured with a piezoresistive accelerometer. RESULTS: When comparing power between upper and lower body muscle groups, both AA and CA groups exhibited similar relationships (r = 0.68 and r = 0.61, respectively), however, the relationship between upper and lower body strength was relatively stronger for the AA group (r = 0.65 vs r = 0.42). When evaluating the strength-power relationship within a given muscle group, i.e., upper or lower body, there were no racial differences, but the relationship between strength and power did differ with respect to muscle group location. CONCLUSIONS: There were stronger relationships between measures of muscular strength and power for the lower limbs when compared to the upper body indicating the importance of muscle group location rather than racial ethnicity as a confounding factor that can affect neuromuscular force production. This information is important when attempting to characterize neuromuscular function relative to specific skills or motor sport performance, thus emphasizing the principle of specificity.

Determination of player potential in volleyball: coaches' rating versus game performance.

The purpose of this study was to determine if the factors which coaches feel indicated superior player potential were the same as those factors which contribute to successful competition outcome. Players from two colleges were evaluated for general and specific performance variables prior to a regular season match between the teams. A player's ability rating was the total of four coaches' ranking on a 1-to-10 scale. Multiple regression analysis to predict player ability rating selected age, vertical jump, total body movement time, and agility (R = 0.87). However, step-wise discriminant analysis to differentiate winning and losing team members selected shoulder flexibility, agility, forearm bump, and sit-and-reach flexibility. The canonical correlation between the winning-losing dichotomy and these skills was 0.74 and resulted in proper classification of 84.6% of the correct team members. It was concluded that the skills coaches consider indicative of superior ability are not necessarily the factors which dictate winning performance.

Anthropometric dimensions to predict 1-RM bench press in untrained females.

BACKGROUND: Previous research has indicated a strong relationship between anthropometric dimensions and strength in males. To date, little work has been done to explore this topic in females. The purpose of this study was to determine the relationships between selected anthropometric dimensions and 1-RM bench press in untrained college females. METHODS: Untrained college females (n = 113) were evaluated for 18 measured and seven derived anthropometric variables to predict 1-RM bench press strength. Triplicate measurements were averaged for five skinfolds, five circumferences, and six skeletal widths. Derived measurements included Body Mass Index, percent fat, fat-free mass (FFM), flexed arm cross-sectional area (CSA), shoulder width: hip width ratio, androgyny index, and somatotype. RESULTS: Highest zero-order correlations with bench press were arm CSA (r = 0.45), flexed arm circumference (r = 0.45), mesomorphy (r = 0.44), and forearm circumference (r = 0.42). First-order partial correlations holding constant body mass or FFM generally decreased most correlations with bench press (r < 0.30). Factor loadings were used to produce muscle, length, and fat components which were placed in a multiple regression analysis to predict bench press but resulted in only limited success (R = 0.58, SEE = +/- 5.6 kg). Coefficients of variation (SEE/Mean x 100) for the equations ranged from was 18.9% to 21.0%. CONCLUSIONS: Prediction of bench press strength from anthropometric dimensions does not appear to be practical or accurate in untrained females.

Anthropometric and somatotype variables related to strength in American football players.

The purpose of this study was to investigate the differences in somatotype, % fat, and strength in relation to body mass of two groups of American football players. One hundred and forty-three football players (85 high school and 58 college) were classified into five weight groups (< 73 kg, 73-82 kg, 83-91 kg, 91-100 kg, > 100 kg). Body composition was estimated from skinfold, and somatotype was determined using the Heath-Carter method. Strength was measured from one-repetition maximum (1-RM) lifts in the bench press and deadlift. Most of the somatotypes were dominant mesomorphs for the high school player and endomesomorphs for the college player. The weight groups in both the high school and college footballer showed significant differences in % fat, somatotype, and strength measures between the lower and higher weight categories. Weight was a greater factor dictating strength in either lift in the high school player than in the college player. A higher mesomorphic component was a more important factor determining strength in the college player while a lower ectomorphic component contributed more in the high school player. The proportion of the variance accounted for by regression equations for the bench press and deadlift was 17% to 41% in the high school player and 35% to 61% in the college player. Although football requires a large individual at certain positions, the question remains concerning overall size versus muscularity to achieve a superior performance level.

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.

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.

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.

Muscular endurance repetitions to predict bench press strength in men of different training levels.

The purpose of this study was to determine the accuracy of predicting maximal bench press (BP) strength (1-RM) from relative endurance performance in various groups of men. The subjects included untrained students (n = 35), resistance trained students (n = 28), college wrestlers (n = 21), soccer players (n = 22), football players (n = 51), high school students (n = 35), and resistance-trained middle-aged men (n = 24). Each subject performed a 1-RM test according to the same standard procedure. Within 4-10 days, the subject selected a weight to perform as many repetitions as possible to failure. Six relative endurance prediction equations produced validity coefficients of r = 0.86 to 0.98 in each group and r = 0.82 to 0.98 in the composite group (n = 220). In subjects completing < or = 10 repetitions-to-failure, three equations significantly overpredicted and two significantly underpredicted 1-RM scores. The Brzycki equation was the most accurate. In subjects completing > 10 repetitions to failure, three equations significantly overpredicted and three significantly underpredicted 1-RM scores. While caution should be used when employing relative muscular endurance performance to estimate 1-RM strength in the bench press, the average of two equations may reduce the error.

Validation of the NFL-225 test for predicting 1-RM bench press performance in college football players.

BACKGROUND: The purpose of this study was to evaluate the accuracy of repetitions-to-fatigue (RTF) using an absolute load of 102.3 kg (225 lbs) to estimate one-repetition maximum (1-RM) bench press performance in college football players using various prediction equations. EXPERIMENTAL DESIGN: a prospective study on the association between muscular endurance and muscular strength. PARTICIPANTS: 260 players from NCAA Division IA (n=43), IAA (n=63), II (n=129), and red-shirts (n=25) were evaluated at the conclusion of a minimum of eight weeks of heavy-resistance training during the off-season. MEASURES: all subjects performed a 1-RM bench press and RTF using an absolute load of 102.3 kg. RESULTS: The Mayhew et al. NFL-225 equation nonsignificantly overestimated 1-RM from RTF by 0.5 kg, while the Chapman et al. NFL-225 equation significantly underpredicted by 3.2 kg, although both equations were comparable in the number of players predicted within +/-4.5 kg of actual 1-RM (52% vs 51%, respectively). Only two of nine RTF equations currently in use produced predicted 1-RM values that were not significantly different from actual 1-RM performance. CONCLUSIONS: Specific NFL-225 equations are more accurate in estimating 1-RM bench press from absolute muscle endurance in college football players than previous published RTF equations. The accuracy of prediction decreases at higher repetitions.