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Biomedical subjects

D J Housh

Publications and source records attributed to D J Housh.

34 records · Page 2Linked to original sources
PubMed1993

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)

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

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↗
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↗
PubMed1991

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.

Adult↗
PubMed1991

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.

Adipose Tissue↗
PubMed1990

The effect of glycogen depletion and supercompensation on the physical working capacity at the fatigue threshold.

The purpose of this investigation was to determine the effect of glycogen depletion and supercompensation on the physical working capacity at the fatigue threshold (PWCFT). Ten adult males (mean age 23 years, SD 3) volunteered as subjects for this study. During the first laboratory visit the subjects performed a maximal bicycle ergometer test for the determination of maximum oxygen consumption (VO2max). Between 48 and 72 h later, the subjects pedaled to exhaustion at a power output which corresponded to a mean of 76% of VO2max (range, 72-80%) for the purpose of glycogen depletion. For the next 3 days, the subjects were fed a 10.5 MJ.day-1 low carbohydrate diet which consisted of 7.5% carbohydrates, 22.0% protein and 70.5% fat. The subjects then performed an incremental cycle ergometer test to the onset of fatigue or PWCFT, which was estimated from integrated electromyographic voltages of the vastus lateralis muscle. For the next 3 days the subjects were fed a 10.5 MJ high carbohydrate diet which consisted of 72.2% carbohydrates, 12.4% protein and 15.4% fats for the purpose of glycogen supercompensation. The subjects then performed a second PWCFT test. A paired t-test indicated that there was no significant (p greater than 0.05) difference between the means of the PWCFT values (depletion 246 W, SD 30; supercompensation 265 W, SD 28) and they were highly correlated at r = 0.884. The results of this investigation suggested that the methods commonly used to affect glycogen depletion or supercompensation had no effect on PWCFT.

Adaptation, Physiological↗
PubMed1990

Factors affecting the estimation of physical working capacity at the fatigue threshold.

The purpose of this study was to investigate potential improvements in the methodology associated with the Physical Working Capacity at the Fatigue Threshold (PWCFT) test including: (1) the use of a continuous test protocol; (2) the use of a treadmill; (3) the use of a bipolar EMG lead system for noisy electronic environments; and (4) the potential for residual fatigue from tests repeated 24 hours apart. The results of the continuous test protocol (mean +/- S.D. = 210 +/- 73 watts) correlated well (r = 0.856) with the original discontinuous technique (222 +/- 83 watts) and there was no significant (p greater than 0.05) difference between the mean values (t = 1.146). Treadmill testing required a bipolar lead system to counteract the electrical noise generated by the treadmill motor. The heart rate values which corresponded to PWCFT on the treadmill (mean +/- s.d. = 164 +/- b.p.m.) and bicycle ergometer (153 +/- 18 b.p.m.) were highly correlated (r = 0.833) and there was no significant (p greater than 0.05) difference between the mean values (t = 2.22). The use of a bipolar lead EMG system on the bicycle ergometer resulted in significantly (p less than 0.05) smaller voltage for any given power output, and the PWCFT exhibited a low to moderate correlation (r = 0.60) with PWCFT derived from a unipolar arrangement. The test-retest results of discontinuous PWCFT measurements performed 24 hours apart on the bicycle ergometer were correlated at r = 0.812 with no significant (p greater than 0.05) difference (t = 0.52) between the mean values (test = 198 +/- 60; retest = 191 +/- 63 watts).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

The effects of age and body weight on anthropometric estimations of minimal wrestling weight in high school wrestlers.

The purpose of this study was to determine the effects of age and body weight on anthropometric estimations of minimal wrestling weight (MWW) in high school wrestlers. Five hundred and twenty-two high school wrestlers (M age +/- SD = 16.45 +/- 1.03 years) volunteered as subjects for this study. The total sample (N = 522) was dichotomized by age (less than 16 years, n = 171; greater than or equal to 16 years, n = 351) and body weight (less than or equal to 62.60 kg, n = 252; greater than 62.60 kg, n = 270). Cross-validation analyses included examination of the constant error (CE), standard error of estimate (SEE), r, and total error (TE). The results indicated that the quadratic skinfold equation of Lohman (EQ1; Table 2) most accurately estimated MWW in each group. Furthermore, it was recommended that MWW be calculated from EQ1 using the conversion constants of Lohman ([(5.03/BD)-4.59] x 100) to estimate relative fat from body density.

Adolescent↗
PubMed1989

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)

Adult↗
PubMed1989

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.

Adolescent↗