摘要:

HALL, S. J. Mechanical contribution to lumbar stress injuries in female gymnasts.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 599–602, 1986. Because female gymnasts as a group display higher than average incidences of stress-related pathologies of the lumbar spine, it was of interest to evaluate mechanical factors which are potential contributors. Lumbar hyperextension and impact forces were quantified for performances of five commonly executed gymnastics skills by four competitive collegiate women gymnasts. The skills performed were the front walkover, the back walkover, and the front handspring, the back handspring, and the handspring vault. Wielke's (1983) radius method was used to quantify lumbar curvatures from film data during normal relaxed standing postures and during subject performances of the five selected skills. A force platform was used to monitor vertical and lateral ground reaction forces at the terminations of the respective skill performances. Of the skills examined, the handspring vault produced the highest vertical and lateral impact forces, and the back handspring and back walkover required the greatest amounts of lumbar hyperextension. During the front and back walkovers and during the back handspring, maximum lumbar hyperextension occurred very close to the time that impact force was sustained by either the hands or the feet.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

MURRAY, D. A. Optimal filtering of constant velocity torque data.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 603–611, 1986. The purpose of this investigation was to implement an optimal filtering strategy for processingin vivodynamometric data. The validity of employing commonly accepted analog smoothing methods was also appraised. An inert gravitational model was used to assess the filtering requirements of two Cybex II constant velocity dynamometers at 10 pre-set speeds with three selected loads. Speed settings were recorded as percentages of the servomechanism's maximum tachometer feedback voltage (10 to 100% Vfbmax). Spectral analyses of unsmoothed torque and associated angular displacement curves, followed by optimized low-pass digital filtering, revealed the presence of two superimposed contaminating influences: i) a damped oscillation, representing successive sudden braking and releasing of the servo-mechanism control system; ii) a relatively stationary oscillatory series, which was attributed to the Cybex motor. The optimal cutoff frequency for any data set was principally a positive function of % Vfbmax. This association was represented for each machine by a different, but reliable, third order least-squares polynomial, which could be used to accurately predict the correct smoothing required for any speed setting. Unacceptable errors may be induced, especially when measuring peak torques, if data are inappropriately filtered. Over-smoothing disguises inertial artefacts. The use of Cybex recorder damping settings should be discouraged. Optimal filtering is a minimal requirement of valid data processing.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

MURRAY, D. A. and E. HARRISON. Constant velocity dynamometer: an appraisal using mechanical loading.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 612–624, 1986. Measurement characteristics of two constant velocity dynamometers (Cybex II, Lumex, Inc., NY) were evaluated at 11 selected speeds (0 to 5 rad-5-1) under various conditions of inert gravitational loading. A linear acceler-ometer was affixed to the lever arm. Speed settings were standardized percentages of each machine's maximum tachometer feedback voltage (0 to 100% Vfbmax). Regression of Cybex transducer-observed voltages (Vfb) on true, i.e., expected, torques (Mc) revealed that, for any static loading condition or angle, the measurement system was essentially linear and valid, although greater variance was evident for smaller torques. However, different calibrations, i.e., regression lines, were required for different speed settings. The error in predicting Mc from Vfbincreased substantially with increased % Vfbmax. Methodologies which assume constant velocity dynamic loading induce questionable, often invalid, results and inferences. Dynamic Vorepresents both gravitational and inertial components. Considerable fluctuations in lever arm instantaneous velocity were ascribed to the combined influence of load and % Vfbmax upon the servomotor. After computing inertia-corrected Mfbcalibration variability and prediction error were markedly reduced. Unexplained variability may be due to poor proximity of the Cybex transducer to the force application point. We concluded that: i) Cybex II should be calibrated only statically; ii) use of an optimal filter will avoid false estimates of joint torque; iii) inertial corrections must be applied in order to minimize potentially serious errors due to system angular acceleration; and iv) reported muscle function relationships might be usefully re-assessed in view of these findings.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ROBINSON, J. R., E. C. FREDERICK, and L. B. COOPER. Systematic ankle stabilization and the effect on performance.Med Sci. Sports Exerc.,Vol. 18, No. 6, pp. 625–628, 1986. Stabilization of the ankle joint is used as a deterrent to injury, however, insufficient or excessive ankle control can cause negative effects. This study determined the effects of systematic changes in ankle and subtalar joint stabilization on performance through an obstacle course. Data were collected on six subjects as they completed two test procedures. Ankle range of motion in the sagittal and frontal planes was determined using a modified Inman apparatus. Completion time through an obstacle course, set up on a basketball court, was used as a measure of performance. High-top basketball shoes were constructed with pockets which allowed strips of plastic (stiffeners) to be positioned just anterior and posterior to the medial and lateral malleoli. Four shoe conditions were used including the shoe with no stiffeners. Significant differences (P< 0.05) in eversion, flexion, and inversion were found between the shoe conditions. A general trend of decreased range of motion with increased restriction was observed. Significant differences (P< 0.05) in performance were found between the shoe conditions, with a general trend of increased times with increased restriction. These results indicate that systematic changes in the range of motion of the ankle and subtalar joints can measurably affect performance.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

WELTMAN, A., C. JANNEY, C. B. RIANS, K. STRAND, B. BERG, S. TIPPITT, J. WISE, B. R. CAHILL, and F. I. KATCH. The effects of hydraulic strength training in pre-pubertal males.Med. Sci. Sports Exerc.,Vol. 18, No. 6, 629–638, 1986. In order to examine the effectiveness and safety of hydraulic resistance strength training in young males, 26 pre-pubertal males (&OV0077; age = 8.2 ± 1.3 yr) completed a 14-wk strength training study. Subjects were evaluated before and after the 14-wk experimental period for pubertal state (Tanner's sexual maturity rating, serum testosterone, and serum dihydroepian-drosterone sulfate). Effectiveness of the strength training program was determined by measuring pre-post differences in: isokinetic strength for flexion and extension at the knee and elbow joints at two speeds (30° and 90°.s-1) (KIN COM, Chattecx, Inc., Chattanooga, TN), flexibility, standing long jump, vertical jump, body composition parameters, maximal oxygen consumption, and creatinine phospho-kinase. Safety of strength training was assessed by biphasic musculo-skeletal scintigraphy before and after the program and by physician evaluation of complaints by subjects. Strength training subjects (N = 16) participated in a 45 min/session, 3 session/wk, 14-wk supervised strength training program with an attendance rate of 91.5%. Participants performed concentric work using hydraulic resistance equipment (Hydra-Fitness Industries, Belton, TX). Eccentric work was not performed. Control subjects (N = 10) did not strength train but did participate in sport activities and activities of daily living. Results indicated that strength training subjects increased isokinetic strength as a result of strength training (average concentric work/repetition ◯ by 18.5 to 36.6% for the eight motions tested; torque scores over the first 90% of the range of motion ◯ by 13.1 to 45.1% for the eight motions tested). These changes were significantly greater than changes seen in the control group (P< 0.05). Strength training subjects also demonstrated significant improvements (as compared to control subjects) in vertical jump (+10.4%), flexibility (+8.4%), and maximal oxygen consumption [+19.4% (1-min-1), +13.8% (ml-kg-min-1)] after the experimental period. Musculoskeletal scintigraphy revealed no evidence of damage to epiphyses, bone, or muscle as a result of strength training. Only one strength training-related injury was reported (left shoulder pain, 3 strength training sessions missed). In contrast, six strength training subjects sustained injuries during activities of daily living, resulting in 47 missed strength training sessions. It was concluded that, in the short term, supervised concentric strength training using hydraulic resistance equipment is safe and effective in pre-pubertal boys.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

BOUCHARD, C, R. LESAGE, G. LORTIE, J.-A. SIMONEAU, P. HAMEL, M. R. BOULAY, L. PÉARUSSE, G. THÉARIAULT, and C. LEBLANC. Aerobic performance in brothers, dizygotic and monozygotic twins.Med. Sci. Sports Exerc., Vol. 18, No. 6, pp. 639–646, 1986. Forty-two brothers, 66 dizygotic twins of both sexes and 106 monozygotic twins of both sexes, 16 to 34 yr of age, took part in this study that was designed to investigate the effect of heredity in aerobic performance. Maximal oxygen uptake (VO2max), maximal heart rate (HRmax), maximal ventilation, and maximal oxygen pulse were obtained from a progressive ergocycle test to exhaustion. Total work output in a 90-min maximal ergocycle test was also determined in the twins. Fat-free weight was estimated from body density measurements obtained through underwater weighing. Aerobic performance scores were adjusted for age (brothers), and age and sex (dizygotic and monozygotic twins) by regression procedures. Dizygotic twins and brothers of same sibship exhibited about the same level of resemblance for all variables or were only slightly different, with the exception of HRmax.Monozygotic pairs were generally more alike than the other sibs, as suggested by the intra-class coefficients. Twin data were used to compute the genetic effects. The within-pair estimate of genetic variance revealed that it was significant (P< 0.05) for all variables except VO2ma-kg-1fat-free weight.min-1.In the case of HRmaxthe among-pairs component estimate had to be used, and it also proved significant (P< 0.01). The size of the genetic effect was computed from three different methods, and it reached about 40% for VO2max-kg-1-min-1, 50% for HRmax60% for maximal oxygen pulse and maximal ventilation, and 70% for 90-min work output-kg-1. Estimates for aerobic performances decreased when reported per kilogram of fat-free weight, i.e., to about 10% for VO2maxand 60% for 90-min work output. These data indicate that a significant genetic effect is present in the population for endurance performance but that a much lower heritability exists for VO2max.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

MORROW, J. R., Jr., A. S. JACKSON, P. W. BRADLEY, and G. H. HARTUNG. Accuracy of measured and predicted residual lung volume on body density measurement.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 647–652, 1986. The effects of measured and predicted residual lung volume on the accuracy of body density and percent fat (%Fat) were investigated. Adult fitness subjects (N = 46) had residual lung volume measured with the oxygen dilution method while those from an athlete sample (N = 134) utilized the nitrogen washout technique. Residual lung volume was also predicted with gender-specific regression equations using height and age and from 24% of vital capacity (%FVC). Residual lung volume alpha reliability for the average of four residual lung volume trials exceeded 0.90 (SEM < = 161 ml) for the oxygen dilution method and 0.99 (SEM = 30 ml) for the average of two nitrogen washout measures. The standard errors for predicted residual lung volume were 579 and 355 ml, respectively, for the men and women in the adult sample and 288 ml for the trained athlete sample. Estimating residual lung volume from %FVC yielded a SEE of 318 ml for the trained athlete sample. Measured residual lung volume errors resulted in errors of 1.04%Fat, 0.87%Fat, and 0.21 %Fat for the men, women, and trained athlete samples, respectively. In contrast, predicted residual lung volume measurement errors resulted in errors of 3.70%Fat, 2.85%Fat, and 1.98%Fat for the respective samples and 2.l8%Fat when using %FVC with the trained athletes. Measured residual lung volume introduces little %Fat error while predicted residual lung volume introduces a substantial source of measurement error.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

COOK. T. C. R. E. LAPORTE, R. A. WASHBURN, N. D. TRAVEN. C. W. SLEMENDA. and K. F. METZ. Chronic low level physical activity as a determinant of high density lipoprotein cholesterol and subfractions.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 653–657, 1986. Physical activity has been associated with reduced risk of coronary heart disease. A mechanism for the reduced risk may be through increased high density lipoprotein cholesterol (HDL-C) and subfractions, in particular HDL2-C. Research associated with increased physical activity investigating HLD-C have assessed the effects of intense aerobic activity. The current research evaluated the relationship between low intensity, long duration activity to HDL-C and subfractions in 35 active postal carriers. Measurements of physical activity via the Large Scale Integrated monitor and reported miles walked, and lipoproteins were assessed at 3-month intervals over a 1-year period. Reported miles walked/day (5.3) was significantly correlated with HLD2-C (r= 0.50, P = 0.003) and approached significance for HDL-C (r= 0.29, P = O.06). The Large Scale Integrated measures were correlated with HDL-C (r= 0.44,P= 0.O08) and HDL2-C (r= 0.44, P = 0.007). Controlling for either age, alcohol consumption, body mass index, or leisure time activity did not reduce the relationship between reported miles walked or Large Scale Integrated readings and HDL2-C, suggesting that the increased HDL-C was the result of long duration, low intensity physical activity.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

NEUFER, P. D., D. L. COSTILL, W. J. FINK, J. P. KIRWAN, R. A. FIELDING, and M. G. FLYNN. Effect of exercise mode and carbohydrate composition on gastric emptying.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 658–662, 1986. To examine the gastric emptying characteristics of selected test drinks varying in carbohydrate composition and concentration, twenty-five runners ingested 400 ml of a solution in one or more of a series of trials followed by either 15 min seated rest or 15 min running(50 to 70% VO2max). The solutions tested at rest included water, 5.0% maltodextrin, 3.0% maltodextrin + 2% glucose (MG5.0), and 4.5% maltodextrin + 2.6% fructose (MF7.I). Solutions tested during running included water, MG5.0, MF7.1, 5.5% maltodexlrin + 2% glucose, and 5.5% maltodextrin + 2% fructose. At rest and during running, water emptied significantly (P< 0.5) faster than all other drinks. In the running trials, the volume of gastric residue of 5.5% maltodextrin + 2% fructose (221.7 ± 11.0 ml) was significantly greater than water (103.4 ± 19.0 ml), MG5.0 (153.3 ± 16.8 ml), and MF7.1 (167.3 ± 14.8), suggesting an inhibitory role of glucose on gastric emptying. Running resulted in a significantly lower volume of gastric residue of water, MG5.0. and MF7.1 (103.4 ± 19.0, 153.3 ± 16.8, and 167.3 ± 14.8 ml, respectively) as compared to the corresponding drinks at rest (209.3 ± 12.6, 287.7 ± 16.0, and 271.0 ± 17.8 ml, respectively). These results suggest a possible advantage for including maltodextrin and fructose as carbohydrate sources in athletic drinks. Furthermore, the rate of gastric emptying is enhanced while running, possibly due to increased mechanical movement of fluid within the stomach.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

LEEDS, E. M., J. E. WILKERSON, G. D. BROWN, G. KAMEN, and D. BREDLE. Effects of jumping exercise and anabolic steroids on plasma total and lipoprotein cholesterol concentrations in male and female rats.Med. Sci. Sports Exerc.,Vol. 18, No. 6, pp. 663–667, 1986. Forty male and 40 female rats were randomly assigned to 1 of 4 experimental groups. Half of the animals of each gender were exercised by jumping (weighted by a vest with up to 70% body weight) to a height of 16 cm 20 times.d-1(30 s between jumps) 5 d.wk-1for 8 wk. Half of the exercised animals and half of the sedentary animals were injected with the anabolic steroid durabolin (0.2 mg in 0.1 ml sesame seed oil) 6 d.wk-1 for the last 3 wk of the 8-wk exercise program. The other animals were injected with 0.1 ml of sesame seed oil (as a placebo) on the same schedule. At the end of the 8-wk program, blood was drawn from the right atria of the anesthetized animals. Plasmas were analyzed for total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) concentrations. Low density lipoprotein cholesterol (LDL-C) concentration was estimated as the difference between these two parameters (TC - HDL-C). A three-factor analysis of variance (2 x 2 x 2) demonstrated that there was a significant (P< 0.05) gender effect (males > females), but no steroid or exercise main effects for TC. There were significant (P< 0.05) steroid and exercise main effects for both HDL-C and estimated LDL-C, as well as a significant gender main effect for estimated LDL-C (but not HDL-C). The results of the present study demonstrate that anabolic steroid administration reduces plasma HDL-C and increases estimated plasma LDL-C levels without altering TC in both male and female animals, regardless of their exercise status. Anaerobic-type exercise alone did decrease estimated LDL-C and increase HDL-C in placebo-injected animals, but not in steroid-injected animals. Thus, anabolic steroid administration resulted in a more atherogenic lipoprotein profile in both male and female animals, changes that were not offset by anaerobic-type exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID