Hypertrophic response to unilateral concentric isokinetic resistance training.

The purposes of this study were to 1) determine the effect of concentric isokinetic training on strength and cross-sectional area (CSA) of selected extensor and flexor muscles of the forearm and leg, 2) examine the potential for preferential hypertrophy of individual muscles within a muscle group, 3) identify the location (proximal, middle, or distal level) of hypertrophy within an individual muscle, and 4) determine the effect of unilateral concentric isokinetic training on strength and hypertrophy of the contralateral limbs. Thirteen untrained male college students [mean age 25.1 +/- 6.1 (SD) yr] volunteered to perform six sets of 10 repetitions of extension and flexion of the nondominant limbs three times per week for 8 wk, using a Cybex II isokinetic dynamometer. Pretraining and posttraining peak torque and muscle CSA measurements for both the dominant and nondominant limbs were determined utilizing a Cybex II isokinetic dynamometer and magnetic resonance imaging scanner, respectively. The results indicated significant (P less than 0.0008) hypertrophy in all trained muscle groups as well as preferential hypertrophy of individual muscles and at specific levels. None of the muscles of the contralateral limbs increased significantly in CSA. In addition, significant (P less than 0.0008) increases in peak torque occurred for trained forearm extension and flexion as well as trained leg flexion. There were no significant increases in peak torque, however, for trained leg extension or for any movement in the contralateral limbs. These data suggest that concentric isokinetic training results in significant strength and hypertrophic responses in the trained limbs.

The accuracy of coaches' estimates of minimal wrestling weight.

The purpose of this study was to compare estimations of minimal wrestling weight (MWW) from experienced high school wrestling coaches and anthropometric equations with those from underwater weighing. Eighty-two wrestlers (X age +/- SD = 16.54 +/- 1.05 yr) volunteered to be assessed via anthropometry and underwater weighing, with percent body fat calculated from body density (BD) using both the conversion constants of Lohman [percent body fat = [5.03/BD) - 4.59) x 100] and Brozek [percent body fat = [4.57/BD) - 4.142) x 100]. In addition, five head coaches, who had between 5 and 24 yr of experience, were asked to estimate within 1 lb the MWW for each of their athletes. The validity of four selected anthropometric equations and the coaches' estimates were compared with the actual MWW from underwater weighing by examining the constant error (CE), r, SEE, and total error (TE) values. The results indicated that the skinfold equation (EQ1) of Lohman provided the most accurate estimates of MWW (TE = 1.90-2.09 kg) and is therefore recommended over the subjective estimates of high school coaches.

Anthropometric growth patterns of high school wrestlers.

The purpose of this investigation was to examine the anthropometric growth patterns of high school wrestlers; 477 high school wrestlers volunteered as subjects for this study. The total sample was divided into four independent age groups: Age group 1 (AG1) = 14.00-14.99 yr (N = 38); AG2 = 15.00-15.99 yr (N = 130); AG3 = 16.00-16.99 yr (N = 163); and AG4 = 17.00-17.99 yr (N = 146). Thirteen anthropometric dimensions (seven diameters and six circumferences) were taken on each subject. To examine normal growth patterns, the anthropometric data were compared with values from a national representative sample of adolescent males. The results indicated that there were few differences between the wrestlers and the national sample for yearly changes in the anthropometric dimensions. These findings suggest that participation in high school wrestling, which typically includes repeated bouts of weight cycling, does not adversely affect normal anthropometric growth patterns.

Validity of skinfold estimates of percent fat in high school female gymnasts.

A preseason estimation of body composition may be useful for assigning a safe minimal body weight for female gymnasts. The present investigation examined the validity of 11 skinfold equations for predicting percent body fat (%fat) in high school female gymnasts (X age +/- SD = 15.7 +/- 1.2 yr) by comparing the values with those obtained from underwater weighing. Seventy-three gymnasts (X %fat +/- SD = 18.6 +/- 4.5%fat) volunteered to serve as subjects. The statistical analyses included examination of the constant error (CE), standard error of estimate (SEE), correlation coefficient (r), and total error (TE). The results of this investigation indicated that 7 of the 11 equations resulted in TE values that were < or = 3.9%fat (range, 3.3-3.9%fat). Of these, the quadratic sum-of-three skinfold equation of Thorland et al. (37) satisfies the most cross-validation criteria and, therefore, is recommended for estimating body composition and minimal body weight in high school female gymnasts. The other six equations with TE values of < or = 3.9%fat should be considered acceptable alternatives.

Isokinetic strength and body composition of high school wrestlers across age.

The purpose of this study was to determine the changes in body composition as well as absolute and relative isokinetic forearm and leg strength of high school wrestlers across age. One hundred ninety-five wrestlers (means age +/- SD = 16.36 +/- 1.12 yr) volunteered to be measured for strength using a Cybex II dynamometer at 30, 180, and 300 degrees.s-1. In addition, underwater weighing was used to determine body composition characteristics. The subjects were divided into four age groups: group 1 (G1) = 14.17-15.00 yr (N = 20); group 2 (G2) = 15.01-16.00 yr (N = 60); group 3 (G3) = 16.01-17.00 yr (N = 52); and group 4 (G4) = 17.01-18.50 yr (N = 63). One-way ANOVA or ANCOVA with Tukey post hoc comparisons indicated significant (P less than 0.05) changes across age for height, body weight, and fat-free weight, as well as absolute and relative forearm and leg strength. The results of this study indicated that, while a large portion of the improvements in strength across age were associated with increases in lean tissue, there was an additional "age effect" which could not be accounted for by changes in fat-free weight. Although the mechanism responsible for the "age effect" is unclear, it is possible that neural development contributed to the strength increases across age.

Validity of bioelectrical impedence equations for estimating fat-free weight in high school female gymnasts.

The present study examined the validity of bioelectrical impedence (BIA) equations for estimating fat-free weight (FFW) in female gymnasts by comparing the values to those obtained from underwater weighing (UWW). Ninety-seven female Caucasian high school gymnasts (mean age +/- SD = 15.7 +/- 1.1 yr) participated in the study. FFW from UWW was calculated from percent fat using the revised formula of Brozek et al. (mean FFW +/- SD = 43.8 +/- 4.5 kg) and the age-specific constants of Lohman (mean FFW +/- SD = 44.8 +/- 4.6 kg). Cross-validation analyses included examination of the constant error (CE), SEE, r, and total error (TE). The results indicated similar trends between equations when based on either the Brozek or Lohman conversions; however, the CE, SEE, and TE values were consistently lower for the majority of the equations using the revised formula of Brozek et al. Based upon the results of the cross-validation analyses, the equation of Houtkooper et al. and the interlaboratory equations of Van Loan et al. and Lohman, which resulted in identical TE values of 2.4 kg are recommended for use with young high school gymnasts.

Anthropometric estimation of thigh muscle cross-sectional area.

The purpose of this investigation was to derive and validate circumference and skinfold equations for estimating the anatomical cross-sectional area (CSA) of the quadriceps, hamstrings, and total thigh muscles. Forty-three adult male (mean age +/- SD = 25 +/- 5 yr) volunteers underwent magnetic resonance imaging (MRI) to determine the CSA of the thigh muscles at the midfemur level as well as midthigh circumference and anterior thigh skinfold assessment. Multiple regression analyses were used to derive equations for predicting quadriceps, hamstrings, and total thigh muscle CSA of the dominant limb from the anthropometric dimensions on a random sample of 30 of the subjects. Cross-validation (CV) analyses were performed for each equation on: (a) the nondominant thigh of the derivation group (N = 30); (b) the dominant thigh of the CV group (N = 13); and (c) the nondominant thigh of the CV group (N = 13). The CV total error values for the quadriceps, hamstrings, and total thigh muscle CSA ranged from 5.4 to 14.4, 3.3 to 5.5, and 10.0 to 25.4 cm2, respectively. The anthropometric equations are recommended for one-time estimates of muscle CSA values in healthy, well-nourished young adult males when more sophisticated procedures are not available.

Age, fat-free weight, and isokinetic peak torque in high school female gymnasts.

The purpose of this study was to examine the covariate influence of fat-free weight (FFW) on age-related increases in isokinetic peak torque for leg flexion and extension in high school female gymnasts. Seventy-two gymnasts (X age +/- SD = 15 7 +/- 1.2 yr) volunteered to be measured for isokinetic leg flexion and extension strength using a calibrated Cybex II dynamometer at 30, 180, and 300 degrees*s(-1) as well as for body composition from underwater weighing. The results indicated that there were significant (P < 0.05) zero-order correlations for age versus leg flexion (r = 0.36-0.47) and extension (r = 0.51-0.57) peak torque, as well as FFW versus leg flexion (r = 0.50-0.66) and extension (r = 0.620.73) peak torque. There were also significant (P < 0.05) first-order partial correlations between age and peak torque (covaried for FFW) for leg extension at 30 (r = 0.25), 180 (r = 0.36-0.39), and 300 degrees*s(-1) (r = 0.25-0.28) but not for leg flexion. These findings indicated that for the high school female gymnasts in the present study, there were age-related increases in strength that could not be accounted for by changes in FFW. It is possible that factors such as an increase in muscle mass per unit of FFW and/or neural maturation contribute to strength increases during adolescence in female athletes.

Validity of skinfold equations for estimating body density in youth wrestlers.

The present investigation examined the validity of 16 skinfold equations for predicting body density (BD) in youth wrestlers (mean age +/- SD = 11.0 +/- 1.3 yr) by comparing the values to those obtained from underwater weighing. Forty-eight members of youth wrestling clubs (mean BD +/- SD = 1.0634 +/- 0.0125 g.cm-3) volunteered to serve as subjects. The statistical analyses included examination of the constant error (CE), standard error of estimate (SEE), correlation coefficient (r), and total error (TE). The results of this investigation indicated that all of the equations resulted in TE values that were > or = 0.0106 g.cm-3 (range = 0.0106-0.0229 g.cm-3) which corresponded to > or = 4.9% body fat. The TE values were too large to provide accurate estimates of body composition in the present sample of youth wrestlers. Future studies should use the CE values from the present investigation to adjust the intercepts of the skinfold equations in the present study and cross-validate the modified equations on young male athletes.

The effects of unilateral velocity-specific concentric strength training.

There is conflicting evidence regarding the efficacy of various resistance training programs for increasing strength in trained and contralateral limbs. The purposes of this investigation were to examine the effects of unilateral velocity-specific concentric isokinetic training of the extensor and flexor muscles of the elbow and knee on: 1) the carry-over effect in strength increases to velocities other than the training velocity in the trained limbs and 2) the cross-training effect at various velocities in the contralateral limbs. Twelve adult men (mean age +/- SD = 24 +/- 6 years) volunteered to train their nondominant extremities three times per week (six sets of 10 maximal repetitions) for 8 weeks at 120 degrees/sec using a Cybex II isokinetic dynamometer. The subjects were tested for increases in peak torque at 60, 120, 180, 240, and 300 degrees/sec. The training resulted in significant (p < 0.05) increases in peak torque on the trained side of the body for elbow extension and flexion as well as knee extension and flexion at all velocities tested. These findings indicated that the velocity-specific training resulted in increases in peak torque at velocities that were both greater and less than the training velocity. In addition, there was a cross-training effect, with significant (p < 0.05) increases in peak torque on the contralateral side of the body for elbow extension (all velocities except 300 degrees/sec) as well as knee extension and flexion (all velocities). These results indicate that unilateral velocity-specific concentric isokinetic training is adequate stimulus for eliciting strength gains at a wide range of velocities in both the trained and contralateral limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Isokinetic leg flexion and extension strength of university football players.

The purpose of this study was to evaluate the difference between positions for absolute and relative isokinetic leg flexion and extension strength as well as ipsilateral and bilateral ratios of NCAA Division II university football players. Fifty-five players (19.8 +/- 1.4 years) volunteered to be measured using a Cybex IP dynamometer at 180 and 300 degrees /sec. The players were grouped into four positions: offensive backs and receivers (OB), offensive linemen (OL), defensive linemen (DL), and defensive backs (DB). One-way ANOVA with Scheffe post hoc comparisons indicated that for absolute flexion and extension strength the linemen (OL and DL) tended to be stronger than the backs (06 and DB); however, these relationships were reversed (backs were stronger than linemen) when differences in body weight were considered (peak torque/body weight). There were no significant (p < 0.05) differences between positions for ipsilateral comparisons at 180 or 300 degrees /sec. However, the magnitude of the ratio was specific to the speed of contraction. Significant differences between positions were found for bilateral strength ratios measured at 180 degrees /sec; however, all values were within 7% of equity and therefore were of little physiological consequence.J Orthop Sports Phys Ther 1988;9(11):365-369.

The effect of unilateral concentric weight training and detraining on joint angle specificity, cross-training, and the bilateral deficit.

Changes in strength following concentric-only weight training and detraining are poorly understood. The purpose of this investigation was to examine the effects of unilateral concentric leg extension weight training and detraining on joint angle specificity, cross-training, and the bilateral deficit (individual limb strength > bilateral strength/2). Sixteen males volunteered to be subjects for this investigation (concentric training group, N = 8; control group, N = 8). The training group performed 8 weeks of training with the nondominant limb three times per week (3-5 sets X six repetitions), followed by 8 weeks of detraining. These subjects were tested pretraining, posttraining, and following detraining for maximal isometric strength at three joint angles (15, 45, and 75 degrees) in both limbs as well as for the one repetition maximum (1-RM) concentric strength of the trained limb, untrained limb, and bilaterally. The results of this investigation indicated that the effects of the concentric weight training were not joint angle specific as the isometric strength increases occurred at all three joint angles. This effect was found in both limbs, indicating that cross-training occurred. The results of the 1-RM analyses showed that initially there was a bilateral deficit (untrained limb > bilateral, trained limb at pretraining). While the concentric training resulted in increases in 1-RM strength in the trained limb, untrained limb, and bilaterally, differences between bilateral strength and the untrained limb were reversed posttraining and the trained limb values exceeded both the bilateral and untrained limb values. Finally, the effects of detraining were more pronounced for isometric strength vs. 1-RM strength as there was a significant decrease from posttraining in the isometric scores, but the detraining 1-RM values were not significantly decreased from posttraining for either limb or bilaterally.

The effect of unilateral eccentric weight training and detraining on joint angle specificity, cross-training, and the bilateral deficit.

Eccentric resistance training is an important component of many rehabilitation protocols. The adaptations following eccentric training are poorly understood in relation to concentric training. The purpose of this investigation was to examine the effects of unilateral eccentric leg extension weight training and detraining on joint angle specificity, cross-training, and the bilateral deficit. Seventeen males volunteered to be subjects for this investigation and were divided into an eccentric training group (N = 9) and a control group (N = 8). The eccentric group performed 8 weeks of unilateral eccentric weight training with the nondominant limb three times per week (3-5 sets of six repetitions) followed by 8 weeks of detraining. These subjects were tested pretraining, posttraining, and following detraining for maximal isometric strength at three joint angles (15, 45, and 75 degrees) in both limbs as well as for the one-repetition maximum (1-RM) eccentric strength of the trained limb, untrained limb, and bilaterally. The results of this investigation indicated that the effects of the eccentric weight training were joint angle specific [significant increases at 45 and 75 degrees (p < 0.05)]. This effect was found in both limbs, indicating a cross-training effect that was joint angle specific. The results from the 1-RM analyses indicated that the bilateral deficit exists for eccentric contractions (untrained limb > bilateral at pretraining) and that unilateral eccentric training increases this effect (trained and untrained limbs > bilateral posttraining); however, the unilateral training also resulted in increased bilateral strength. Both the 1-RM and isometric analyses showed that the training effects persisted over 8 weeks of detraining.

The relationship between anaerobic running capacity and peak plasma lactate.

The purpose of this study was to examine the relationship between anaerobic running capacity and peak plasma lactate. Twelve adult males (mean age +/- SD = 21.9 +/- 1.2 yrs) performed a critical velocity test from which anaerobic running capacity was determined and a maximal treadmill running test from which peak plasma lactate was determined from post-exercise blood samples taken at one minute intervals. The results indicated that anaerobic running capacity (mean +/- SD = 0.18 +/- 0.04 km) was not significantly (r = -0.06, p greater than 0.05) correlated with peak plasma lactate (9.3 +/- 1.8 mM). These findings do not support anaerobic running capacity as an indirect indicator of anaerobic capabilities.

The relationship between critical power and the onset of blood lactate accumulation.

The purpose of this investigation was to determine the contribution of the onset of blood lactate accumulation (OBLA), the heartrate-workload slope (HR-WL) and the efficiency of electrical activity (EEA = slope of IEMG vs. workload) of the leg extensor muscles to Critical Power (CP). Twelve adult males (mean age +/- SD = 24.5 +/- 2.8 yrs) volunteered as subjects for this study. Zero-order correlations indicated that OBLA was significantly (p less than 0.05) related to CP (r = 0.616) and EEA (r = -0.577). Stepwise multiple regression resulted in a one variable model with OBLA the only significant (p less than 0.05) predictor of CP. Furthermore, a related t-test resulted in a significant difference between the means of the power out-put at CP (mean +/- SD = 230.0 +/- 22.1 watts) and OBLA (179.6 +/- 31.8 watts). The results of this study indicated that the two threshold parameters, CP and OBLA, were significantly related and therefore it is likely that the physiological factors responsible for OBLA also influence CP. However, the significant mean differences indicated that the mechanisms which underly CP and OBLA were not identical. Furthermore, the HR-WL slope (mean +/- SD = 0.343 +/- 0.071 beats per watt) and EEA (0.969 +/- 0.572 microvolts per watt) were not potent predictors of CP.

The effect of exhaustive exercise on salivary immunoglobulin A.

The purpose of this study was to examine salivary immunoglobulin A (s-IgA) responses to exhaustive exercise. Twenty-nine, college age (means +/- SD = 21.45 +/- 3.1 yrs; range 18-29 yrs) moderately active males (running < 10 miles per week) performed an incremental treadmill test to exhaustion. Unstimulated salivary samples, collected before as well as immediately and one hour following the test, were analyzed for s-IgA using an enzyme-linked immunosorbent assay (ELISA). Mean s-IgA levels decreased significantly (24.4%, p < 0.05) immediately following the maximal test, and remained depressed (16.9%) one hour after the test. Of the 29 subjects, five exhibited an increase (range = 1.3 to 53.3%) in s-IgA following the exercise bout. The results of this study suggest that exhaustive exercise may temporarily reduce salivary IgA levels.

Neuromuscular fatigue thresholds of the vastus lateralis, vastus medialis and rectus femoris muscles.

The purpose of this study was to compare the power outputs associated with the onset of neuromuscular fatigue in the superficial muscles of the quadriceps femoris group by simultaneously monitoring the EMG activity from the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles during a Physical Working Capacity at the Fatigue Threshold (PWCFT) test. Eleven adult males (mean +/- SD = 24 +/- 3y) served as subjects. There were no significant (p > 0.05) differences among the mean PWCFT values for the VL (226 +/- 58 W), VM (223 +/- 58 W) and RF (203 +/- 54 W) muscles. These findings indicates that the superficial muscles of the quadriceps femoris group generally responded as a unit with respect to the onset (threshold) of neuromuscular fatigue as measured by the PWCFT test.

The accuracy of the critical power test for predicting time to exhaustion during cycle ergometry.

The purpose of this study was to determine the relationship between actual time to exhaustion or time limit (ATLIM) during bicycle ergometry and predicted time to exhaustion (PTLIM) from the Critical Power (CP) test. fourteen males (means +/- SD = 22.36 +/- 2.13 years) volunteered as subjects for this investigation. The subjects visited the laboratory on seven occasions separated by at least 24 h. The first two visits were used for the determination of CP; during the remaining sessions the subjects rode a Monarch bicycle ergometer at power loadings of CP - 20%, CP, CP + 20%, CP + 40% and CP + 60% for the determination of ATLIM. Theoretically, power loadings less than or equal to CP can be maintained indefinitely without exhaustion and the PTLIM for power loadings greater than CP can be estimated from the results of the CP test. The accuracy of the CP test for estimating the time to exhaustion during bicycle ergometry was determined by comparing ATLIM to PTLIM using correlation coefficients, standard error of estimates and related t-tests. The results of this study indicated that there were no significant (p greater than 0.05) differences between ATLIM and PTLIM for power loadings greater than CP (ATLIM vs PTLIM at CP + 20% = 8.19 +/- 3.90 vs 7.13 +/- 2.69 min, t = 2.106, r = 0.893, SEE = 1.21 min; CP + 40% = 3.60 +/- 1.37 vs 3.46 +/- 1.18 min, t = 0.842, r = 0.882, SEE = 0.556 min; CP + 60% = 2.36 +/- 0.95 vs 2.32 +/- 0.79 min; t = 0.328 r = 0.841, SEE = 0.428 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological responses at the fatigue threshold.

The purpose of this investigation was to determine the oxygen consumption, heart rate and plasma lactate responses at the fatigue threshold (FT) and estimate the length of time the FT could be maintained. Ten adult males (mean age +/- SD = 21.1 +/- 1.3 yrs) volunteered to perform a maximal treadmill test and FT test. During the maximal test, VO2 heart rate and plasma lactate measurements were taken. The results of the investigation indicated that the FT (14.0 +/- 1.2 km.hr-1, 197 +/- 8 bpm; 47.5 +/- 5.7 ml/kg.min-1, 5.4 +/- 1.3 mM) was very close to a maximal effort (VO2max = 14.4 +/- 1.2 km.hr-1, 203 +/- 10 bpm; 49.5 +/- 6.1 ml/kg.min-1, 7.4 +/- 2.1 mM) and could be maintained for only 0.16 to 0.28 hrs. These findings do not support the validity of the FT as a measure of the maximal running velocity that can be continued for an extended period of time without exhaustion.

Effects of eccentric-only resistance training and detraining.

The purposes of this investigation were to examine the effects of unilateral eccentric-only dynamic constant external resistance (DCER) training of the leg extensor muscles on: (a) eccentric DCER strength in the trained and untrained limbs, (b) concentric isokinetic leg extension peak torque-velocity curves in the trained and untrained limbs, and (c) retention of eccentric DCER strength and concentric isokinetic peak torque in the trained and untrained limbs following detraining. Seventeen adult male (X age +/- SD = 24 +/- 3 yr) volunteers comprised training (TR, n = 9) and control (CTL, n = 8) groups. The TR group trained the leg extensor muscles of the nondominant limb with eccentric-only DCER exercise (3 - 5 sets of 6 repetitions at 80% of the eccentric one-repetition maximum [1-RM] load) for eight weeks followed by eight additional weeks of detraining. The CTL group did not train. All subjects were tested pretraining, posttraining, and after detraining for 1-RM unilateral eccentric DCER strength of the leg extensor muscles as well as concentric isokinetic leg extension peak torque at 1.05, 2.09, 3.14, 4.19, and 5.24 rad.s(-1) in both limbs. Mixed factorial ANOVAs, follow-ups, and post-hoc analyses indicated that the training resulted in increased eccentric DCER strength in both the trained (29 %) and untrained (17 %) limbs, but no change in isokinetic peak torque at any of the velocities of contraction in either limb. Furthermore, the training-induced increases in eccentric DCER strength for both limbs were retained across eight weeks of detraining.