摘要:

Nine male and five female college students were tested on four occasions to determine the effects of various exhaustive weight-lifting stimuli on forearm blood flow as measured by strain-gauge plethysmography. Maximum voluntary dynamic wrist curl strength was determined in the first session, which was followed by random treatments of exercise with 70, 80, and 90% of the weight subjects could curl only one time (1 RM) on three separate days. During each treatment, after a 15-min rest, subjects performed three sets of exercise movements at a pace of 0.5 Hz until voluntary exhaustion. Each set of continuous repetitions was followed by a 166-s recovery period. Blood flows (ml flow·100 ml tissue-1·min-1) were determined at 10, 36, 62, 88, 114, 140, and 166 s of recovery. Data were analyzed using ANOVA tests for a three (intensities) by three (sets) complete factorial design with repeated measures on all factors. Generally, 90% flows were significantly (P<0.05) lower than both 70 and 80% flows. Also, 70% flows were statistically equal to 80% flows. There were significant (P<0.05) set effects at 10, 36, 114, and 166 s of recovery. Blood flows for set 3 exceeded those for set 1 at 10, 36, 114, and 166 s of recovery, and blood flows for set 2 exceeded those for set 1 at 166 s of recovery.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The effects of endurance training on coronary vascular resistance, myocardial blood flow, and oxygen consumption during tachycardia, and with adenosine-induced coronary dilation, were studied in a group of exercise-trained dogs. Seven mongrel clogs were conditioned by 8 wk of running on a motor-driven treadmill. Following conditioning, aortic pressure was unchanged in trained compared to a non-trained group, while cardiac output was somewhat lower in the trained group. Left ventricular myocardial blood Dow determined by the microsphere technique was not different at rest or with tachycardia in trained vs control animals, and no significant differences in oxygen consumption were observed between trained and nontrained animals under any experimental conditions. Coronary resistance during pacing (NT: 1.00 ± 0.09, T: 0.79 ± 0.06 mmHg/ml·min-1·100 g-1) in the trained group was similar to the nontrained group, and both groups had the same resistance during adenosine infusion (NT: 0.49 ± 0.20, T: 0.44 ± 0.08). In addition, there were no differences in coronary A-V oxygen difference or coronary sinus saturation after training. The data indicate that little change occurs in the maximum flow capacity of the coronary bed following exercise training, and the trained heart responds to tachycardia with a reduced vascular resistance and increase coronary flow in a fashion similar to untrained animals.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

ABSTRACTSix low-altitude natives (LAN) (373 in or less, aged 19–25 yr) and eight moderate-altitude natives (MAN) (1830–2200 m, aged 19–23 yr) were studied at both their residence (home) altitude (740 Torr and 587 Torr, respectively) and in a hypobaric chamber at a simulated altitude of 4270 m (447 Torr). Following a 2-d adaptation period, subjects performed an incremented test on the cycle ergometer until voluntary exhaustion. Significantly (P<0.05) greater differences in percent change of maximum exercise variables (total exercise time, exercise intensity, VO2, VCO2, VE/VO2and HR) were noted in the LAN group than in the MAN group, going from their residence altitude to 447 Torr. The decrement in VO2max, was 15% in the MAN group compared to 34% in the LAN group. The anaerobic threshold (% VO2max), estimated from VE BTPS measurements, was similar in both groups at residence altitude and at 447 Torr. In the morning prior to exercise testing at 447 Torr, LAN subjects reported greater (P<0.001) symptoms of acute mountain sickness (AMS) than MAN subjects. Our results indicate that, with respect to maximum exercise performance, moderate-altitude natives are at an advantage during early adaptation to hypobaric hypoxia.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Inadequate carbohydrate and fluids can limit physical performance; optimal delivery of both should be the goal of any beverage designed especially for the athlete. In this study, the gastric-emptying characteristics of two carbohydrate-eleclrolyte solutions were compared with water. The 5% carbohydrate solution contained 3% Polycose glucose polymers and 2% fructose, whereas the 7% solution contained 5% Polycose glucose polymers and 2% fructose. Both solutions contained similar amounts of sodium, potassium, calcium, magnesium, and chloride in the range suggested by the American College of Sports Medicine for rehydration solutions. Four hundred milliliters of each solution were administered to six male subjects and the amount of fluid emptied at 30 and 60 min by each subject was calculated. A non-absorbable dye, phenol red, was used to correct for gastric secretion. The gastric emptying of the 7% solution in healthy adult male subjects was not significantly different from the 5% solution or cold water. Inclusion of a polymerized form of glucose in a 7% glucose polymer-fructose solution can supply 70 g of carbohydrate per liter and also maximizes rehydration. This solution may be particularly useful in those activities where fluid and energy loss are particularly important.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The purpose of this study was to investigate the significance of the freely-chosen stroke rate (S) in swimming to attain maximum velocity. Seven club swimmers swam five 366-m freestyle trials, the first three at low to maximum velocities and the next two at higher stroke rates in an attempt to increase velocity further. A clear “inverted U” pattern was observed, the optimal stroke rate (Sopt) being the median rate of 45.8 (range 42–49) S · min-1. Each subject then performed a maximal experimental test on five separate occasions, simulating the freestyle arm action on a biokinetic swim bench. Stroke rate was manipulated according to the five rates used by each subject in the swim trials. The mean Vo2pekon the biokinetic bench also varied as an “inverted U” curvilinear function of S, with the correlation between Sopt and the S at the highest VO2peakbeing 0.98 (P<0.001). Peak values for VO2VE, and heart rate in simulated swimming were, respectively, 73%, 52%, and 85% of the maximal rates determined on a cycle ergometer. Maximum swimming velocity was not significantly correlated with VO2max, or with VO2peakon the swim bench (P>0.05). Results confirm that freely-chosen S produces the top performance in swimming to attain maximum velocity and the highest peak VO2values in simulated swimming on a biokinetic bench.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Control of the amount and/or rate of pronation of the foot which occurs during distance running has been cited as an important consideration for runners when selecting a running shoe. In this study, high-speed movie film was taken from the rear while 10 subjects ran on a treadmill at a pace of 3.8 m·s-1. These subjects wore 36 different shoes in combinations of three midsole hardnesses, three heel Dares, and four heel heights. The film data were digitized and used to determine the eversion or inversion of the heel relative to the lower leg throughout foot contact. Because eversion of the foot is a component of pronation it was used as a predictor of how much pronation was occurring. It was found that shoes with soft midsoles (25 durometer, Shore A scale) allowed significantly more maximum pronation (MP) and total rearfoot movement (TRM) than shoes with either medium (35 durometer) or hard (-15 durometer) midsoles. Shoes with 0° heel Dare allowed significantly more MP and TRM than shoes with either 15° or 30° heel flares. Heel height was found to have no significant effect on either MP or TRM. These data provide guidelines for the construction of running shoes designed to limit rearfoot movement.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

An augmented cubic spline function was evaluated as an alternative solution to the end-point problem which frequently arises in the smoothing and differentiation of biomechanical position-time data. The usual procedures of natural cubic spline functions and digital filtering have the undesirable effect of forcing the accelerations to zero at the ends of the data set. The proposed augmented cubic spline procedure does not have this characteristic but rather requires the curve to pass through a single extra point at each end of the data set. Using two different criteria with large acceleration magnitudes near the end of the data set, we have compared the effectiveness of all three methods in terms of the total curve (root mean square error) and in terms of the last few points (percent and algebraic error). In both experiments the augmented cubic spline procedure was found to be superior to both digital Gltering and natural cubic spline functions. It was concluded that this technique could be used for smoothing and differentiating biomechanical data in instances where the underlying function is unknown and the accelerations at the end points of the data set are suspected of being non-zero.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Several investigators have demonstrated experimentally that ball-rebound velocity after an eccentric impact against a tennis racket remains unchanged for two extreme conditions of grip firmness, i.e., when the grip is firmly clamped and when it is allowed to stand freely on its butt. The present study utilized a simple mathematical model from classical impact theory to provide analytical support for their experimental findings. It was shown that the functional relationship between the approach and rebound velocity of the ball is dependent on five dimensionless numbers: 1) the ratio of the ball to racket mass; 2) the ratio of the radius of gyration about the racket pivot to the distance of the geometric center of the racket head to the pivot; 3) the coefficient of restitution between the ball and the racket string ensemble; 4) the ratio of the distances of the center of mass and the center of the strings to the pivot; and 5) the ratio of the grip length to the distance from the pivot to the center of the strings. Because the mass and length ratios are very small numbers for tennis, the rebound-to-approach velocity of the ball is principally a function of the coefficient of restitution, which is practically independent of the conditions of grip firmness. Using published data generated from other experiments, analytical estimates were obtained for the values of the coefficient of restitution between a tennis ball and a racket strung to typical tensions for various rebound-to-approach velocity ratios. These estimates were validated directly by an independent experiment.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The results of 66 training studies involving the measurement of human blood lipid and lipoprotein changes over time, conducted over the last 26 yr, and representing 2925 subjects (2086 experimental and 839 control) were collected and statistically aggregated using the meta-analysis technique. Across all types of subjects, treatments, sources, and research designs, the average exercising subject was found to have a reduction in total cholesterol of 10 mg·dl-1(P>0.01), total triglyceride decreased by 15.8 mg·dl-1(P>0.01), HDL-C increased by 1.2 mg·dl-1(NS), LDL-C decreased by 5.1 mg·dl-1(P>0.05), and total/HDL-C ratio showed a large decrease of 0.48 (P>0.01). None of the changes for the control groups were significant. Initial levels of total cholesterol, total triglyceride, HDL-C, and total/ HDL-C ratio were strongly correlated with their respective changes as a result of training, regardless of the data partitioning. Higher initial levels of total cholesterol, total triglyceride, and total/HDL-C ratio resulted in greater decreases post-exercise (r=0.48, 0.76, and 0.75, respectively;P>0.01), and lower initial levels of HDL-C resulted in greater post-exercise increases (r=0.50;P>0.01). Overall, physical training seemed to produce beneficial changes in blood lipids and lipoproteins. However, researchers must be careful when examining the relationship between physical training and serum lipids and lipoproteins because initial levels, age, length of training, intensity, VO2max, body weight, and percent body fat have been shown in this meta-analysis to interact with exercise and serum lipid and lipoprotein changes.

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A small portable accelerometer was developed to estimate the energy expenditure of daily activities. The accelerometer is reported to be an improvement over movement counters currently on the market. The oxygen requirement of 14 different activities was measured in 21 subjects while each wore the accelerometer on the waist. A movement counter (mercury switch), which is available commercially, was also worn on the waist and another was worn on the left wrist. The reproducibility of the accelerometer readings was high (4 subjects, 14 activities; r=0.94) and was superior to either the waist movement counter (r=0.63) or the wrist movement counter (r=0.74). In estimating oxygen requirement (Vo2) the standard error of estimate, based on 21 subjects and 14 activities, was 6.6 ml·min-1·kg-1for the accelerometer. This was also better (smaller) than for the waist movement counter (9.2 ml·min-1·kg-1) or for the wrist movement counter (7.9 ml·min-1·kg-1).

ISSN:0195-9131    

出版商:OVID    

年代:1983

数据来源: OVID