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Biomedical subjects

G O Johnson

Publications and source records attributed to G O Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1995

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.

Body Composition↗
PubMed1994

Validity of percent body fat estimations in males.

The present investigation examined the validity of selected skinfold (Sum3), near-infrared interactance (F5000 and F1000), and bioelectrical impedance (BIA) equations for estimating percent body fat (% fat) in young adult males (mean age +/- SD = 22 +/- 3 yr) by comparing the estimates with values obtained from underwater weighing. Fifty-seven Caucasian male (mean % fat +/- SD = 15.1 +/- 6.2) volunteers served as subjects. The statistical analyses included examination of constant error (CE), standard error of estimate (SEE), r, and total error (TE). The results indicated that the Sum3 equation had the lowest SEE (2.7% fat) and TE (3.6% fat) as well as the highest validity coefficient (r = 0.90). The F5000, however, had the lowest CE (-1.0% fat). Based on these findings, the Sum3 equation is recommended over the F5000 (TE = 4.2% fat), F1000 (TE = 6.1% fat), and BIA (TE = 5.0% fat) equations for estimating % fat in young adult males.

Adipose Tissue↗
PubMed1993

An examination of the electromyographic fatigue threshold test.

The purpose of this investigation was to examine times to exhaustion at various percentages of the electromyographic fatigue threshold (EMGFT). Eight adult males [mean (SD), 21 (1) years] volunteered for the investigation. EMGFT was derived by determining the rate of rise in the electrical activity of the vastus lateralis [using integrated electromyography (iEMG)] over time (iEMG slope) for four fatiguing power outputs during cycle ergometry. The four power outputs were then plotted as a function of the four iEMG slope coefficients. The y-intercept of the power output versus iEMG slope coefficient graph was defined as the EMGFT. The intraclass correlation for repeated EMGFT tests was R = 0.65 (SEE = 7 W) and there was no significant (P > 0.05) difference between the mean (SD) values for test [260 (11) W] versus retest [262 (32) W]. Actual times to exhaustion were determined for work bouts at power outputs equal to 85, 100, 115, 130, and 145% of EMGFT. The mean (SD) times to exhaustion for these work bouts were 495 (231), 225 (72), 135 (35), 94 (17), and 72 (14) s, respectively. A power curve was derived using the mean power outputs and mean times to exhaustion from the five rides at various percentages of EMGFT. The power curve provided estimates of the power outputs which could be maintained for 30 and 60 min. There were significant (P < 0.05) differences between the mean EMGFT (260 W) and the power outputs which could be maintained for 30 (151 W) and 60 (125 W) min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The effect of dynamic constant external resistance training on the isokinetic torque-velocity curve.

The purpose of this investigation was to examine the effects of dynamic constant external resistance (DCER) training on isokinetic peak torque (PT) and constant joint angle (CJA) torque at velocities from zero to 5.03 rad.s-1. Twelve male volunteers (mean age +/- SD = 21.67 +/- 2.61 years) were trained using DCER exercises (leg extension and squat) for eight weeks. The subjects were tested pre-training and post-training for isokinetic leg extension PT as well as CJA torque (0.26 rad below the horizontal plane) at multiple velocities (zero, 0.84, 1.68, 2.51, 3.35, 4.19 and 5.03 rad.s-1) using a Cybex II isokinetic dynamometer. Film analyses indicated that the mean training velocities for leg extension and squat were 1.50 +/- 0.20 rad.s-1 and 1.41 +/- 0.26 rad.s-1, respectively. Univariate two-way repeated measures (within subjects design) ANOVAs [time (pre-training versus posttraining) x velocity] were used to analyze the changes in PT and CJA torque across the training period. There was no interaction but a significant (p < 0.05) main effect for time for the CJA torque measures. The increases in CJA torque ranged from 6.3 to 10.7%. For PT, there was a significant (p < 0.05) time x velocity interaction. Post-hoc comparisons showed that PT increased significantly at all velocities (p < 0.0083) as a result of the training (8.1 to 10.9%). The results of this investigation indicated that DCER training significantly increased isokinetic PT and CJA torque values at velocities up to 3.53 rad.s-1 above the training velocity.

Adult↗
PubMed1993

Acute effects of different intensities of weight lifting on serum testosterone.

The purpose of this investigation was to determine the effect of moderate weight lifting (MWL) and light weight lifting (LWL) on concentrations of serum testosterone in males. Baseline testosterone concentrations were determined via an indwelling catheter in the median cubital vein. An initial sample of blood was followed 7 min later by five samples taken at 4-min intervals. A final sample was taken 10 min after the last 4-min blood draw. Blood samples were obtained at similar times and intervals on the weight lifting days. The MWL consisted of four sets of six squats at 90-95% of a six-repetition maximum (RM), while the LWL consisted of four sets of 9 or 10 repetitions at 60-65% of the weight used for the sets during MWL. There was a significant increase in serum testosterone concentrations following the fourth set for both MWL and LWL when compared with baseline concentrations and both MWL and LWL testosterone concentrations returned to baseline levels at 10 min postexercise. These results indicate that MWL and LWL caused increases in serum testosterone that were greater than those associated with baseline levels. Postexercise responses for the MWL and LWL were similar.

Adult↗
PubMed1993

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.

Adolescent↗
PubMed1992

The accuracy of the critical velocity test for predicting time to exhaustion during treadmill running.

The purpose of this investigation was to determine the accuracy of the critical velocity (CV) test for predicting time to exhaustion (time limit = TL) during treadmill running. Ten adult males (mean +/- SD of age = 23 +/- 2 years) volunteered to perform a maximal treadmill test, a CV test, and five exhaustive treadmill runs at 70%, 85%, 100%, 115% and 130% of CV for the determination of actual TL. Related t-tests revealed significant (p less than 0.05) differences between the predicted and actual TL values for velocities equal to 100 and 130% of CV. The correlations between predicted and actual TL values for velocities above CV ranged from r = 0.957 to 0.980 (SEE = 0.28-0.82 minutes). At 100% of CV, the subjects maintained the running pace for an average of 16.43 +/- 6.08 minutes (range = 9.96-31.90 minutes) while, at 85% of CV, 8 of the 10 subjects were able to maintain the running pace for 60 minutes. These findings did not support the validity of the CV test for predicting the actual TL during treadmill running and indicated that, in 20% of the cases, CV overestimated the running velocity that could be maintained for 60 minutes by greater than 15%.

Adult↗
PubMed1992

The effect of exercise training on salivary immunoglobulin A and cortisol responses to maximal exercise.

The salivary immunoglobulin A (s-IgA) and cortisol responses to maximal exercise were examined in 24 adult males (X +/- SD; 22.1 +/- 3.0 yrs) before and after 10 weeks of run training. The subjects performed an incremental treadmill test to exhaustion and were randomly assigned to one of three groups: control (CON; n = 5), low intensity training (LO; n = 8), or high intensity training (HI; n = 11). Following the ten weeks of training, the subjects performed a second maximal treadmill test. Saliva samples were collected before, as well as immediately and 1 hr following each of the maximal treadmill tests and were analyzed for s-IgA and salivary cortisol. Maximal oxygen consumption (VO2max) increased significantly (p < 0.05) in the LO and HI groups but remained unchanged in the CON group. The s-IgA levels decreased significantly (p < 0.05) immediately post-exercise but returned to pre-exercise levels by one hour recovery. In addition, s-IgA and cortisol levels were not significantly (p > 0.05) correlated at any of the sampling times. These findings indicated that the s-IgA response to maximal exercise was unaffected by moderate (70% of VO2 max) to heavy (86% of VO2max) training (designed to develop cardiorespiratory fitness in healthy non-athletic adults) and independent of salivary cortisol.

Adult↗
PubMed1992

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.

Adult↗
PubMed1992

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.

Adolescent↗
PubMed1992

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.

Adult↗
PubMed1992

Validity of bioelectrical impedance equations for estimating fat-free weight in lean males.

The present study examined the validity of bioelectrical impedance (BIA) equations for estimating fat-free weight (FFW) in lean males (X +/- SD = 9.1 +/- 2.2% fat) by comparing the estimates with values obtained from underwater weighing. Sixty-eight Caucasian male volunteers served as subjects. Cross-validation analyses included examination of the constant error (CE), standard error of the estimate (SEE), r, and total error (TE). The results indicated that the equations of Oppliger et al. (16), which resulted in small TE (1.70 kg) and CE (-0.02 kg) values, most accurately estimated FFW. Simple linear regression showed that FFW was more highly correlated with body weight (BW) (r = 0.98, P < 0.0001) and resulted in a lower SEE (1.68 kg) than either height2/resistance (Ht2/R) (r = 0.81, P < 0.0001; SEE = 5.12 kg) or the independent variable (weight x resistance)/height2 [WR/Ht2] utilized by the manufacturer of the BIA analyzer (r = 0.15, P > 0.05; SEE = 8.59 kg). Multiple regression showed that when WR/Ht2, Ht2/R, resistance, body mass index, Ht2, and/or Ht was added to the prediction equation, which utilized BW alone, they accounted for less than 1% additional variance and reduced the SEE by < or = 0.16 kg. The results indicated that BW alone estimated FFW as accurately as any of the BIA equations in lean males.

Adipose Tissue↗
PubMed1992

The validity of visual estimations of percent body fat in lean males.

The present study compared the validity of visual estimations of percent fat (% fat) in lean males (mean +/- SD = 9.6 +/- 2.3 % fat) to the validity of bioelectrical impedance analysis (BIA) and skinfold equations. Thirty-five Caucasian male volunteers (mean +/- SD = 23 +/- 5 yr; range = 19-40) served as subjects. Visual estimations of % fat were performed by two experienced male raters. The validity (compared to underwater weighing) for each procedure was determined by examining the constant error (CE), standard error of the estimate (SEE), r, and total error (TE). The results indicated that rater 1 (TE = 2.3% fat) could visually estimate % fat as accurately as the skinfold equations (TE = 2.4% fat). However, based on low TE, SEE, and CE values as well as considerable variability (mean difference = 2.7% fat) between the % fat estimates of the two raters, skinfold equations are recommended over visual inspection and BIA (TE = 5.0% fat) for estimating % fat in lean males.

Adult↗
PubMed1991

The effect of exercise intensity and duration on salivary immunoglobulin A.

Two experiments were performed to examine salivary immunoglobulin A (s-IgA) responses to varying levels of exercise intensity and duration. For experiment 1, 9 college men (mean age, SD = 23.56, 1.64 years) completed treadmill runs of 15, 30, and 45 min at approximately 60% of maximum oxygen consumption (VO2max). For experiment 2, 9 other college men (mean age, SD = 23.67, 2.0 years) ran for 20 min at approximately 50, 65 and 80% of VO2max. Unstimulated salivary samples were collected before, and immediately, 1 and 2 h after the exercise. Samples were assayed for s-IgA using an enzyme-linked immunosorbent assay. Mean s-IgA levels did not change significantly (P greater than 0.05) at any of the post-exercise collection times when compared to pre-exercise levels. The results of this investigation indicated that running at intensities of 50-80% of VO2max and for durations of 15-45 min did not affect s-IgA levels.

Adult↗
PubMed1991

The effect of ammonium chloride and sodium bicarbonate ingestion on the physical working capacity at the fatigue threshold.

The purpose of this investigation was to examine the effect of ammonium chloride (NH4Cl) and sodium bicarbonate (NaHCO3) ingestion on the physical working capacity at the fatigue threshold (PWCFT). Eighteen adult males (mean age, SD = 23, 2 years) volunteered for two experiments (experiment 1, n = 9; experiment 2, n = 9). In both experiments, the subjects orally ingested 0.3 g.kg-1 body weight of NH4Cl and NaHCO3 over a 3-h period in random order on days separated by 72 h or more. In experiment 1, following ingestion of the substance, the subjects performed a discontinuous incremental cycle ergometer test to the onset of PWCFT which was estimated from integrated electromyography voltages at the vastus lateralis muscle. In experiment 2, the subjects performed a continuous PWCFT test. The results of these experiments indicated that NH4Cl and NaHCO3 ingestion had no significant (P greater than 0.05) effect on PWCFT (experiment 1: NH4Cl = 257, SD 26 W; NaHCO3 = 256, SD 22 W; t = 0.06; r = 0.866; experiment 2: NH4Cl = 231, 14 W; NaHCO3 = 216, 16 W; t = 1.78; r = 0.857).

Administration, Oral↗
PubMed1991

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.

Adult↗
PubMed1991

The effect of exercise at various temperatures on salivary levels of immunoglobulin A.

The purpose of this investigation was to determine the effect of ambient temperature on the salivary immunoglobulin A (s-IgA) response to submaximal exercise. Nine adult males (x age +/- SD = 22 +/- 2 yrs) volunteered to perform an incremental treadmill test to exhaustion for the determination of VO2max and three 30-minute treadmill runs at 80% VO2max in an environmental chamber at temperatures of approximately 6, 19 and 34 degrees C. Saliva samples were collected prior to each submaximal workbout as well as immediately and 1 hr post-exercise. A 2 within subjects factors (temperature, sample time) repeated measures ANOVA indicated no significant interaction or main effects for sampling time or temperature. The results of this study indicated that 30 minutes of non-competitive exercise at temperatures ranging from 6 to 34 degrees C had no effect on s-IgA. These findings suggest that moderate intensity exercises at a wide range of ambient temperatures does not increase the susceptibility to upper respiratory infection by decreasing s-IgA.

Adult↗