摘要:

ABSTRACTBERGH, ULF, ALF THORSTENSSON, BERTIL SJÖDIN, BODIL HULTEN, KARIN PIEHL, and JAN KARLSSON. Maximal oxygen uptake and muscle fiber types in trained and untrained humans.Med. Sci. Sports.Vol. 10, No. 3, pp. 151‐154, 1978.—Maximal oxygen uptake (&OV0312;o2max) was determined in 138 male and 41 female human subjects and muscle fiber composition (gastrocnemius and vastus lateralis) in 53 of the males. Highest values for &OV0312;o2max were 7.38 1x min‐1and 4.34 l x min‐1in males and females, respectively. In relation to body weight the highest values were 94 and 77 ml x (kg x min)‐1. Athletes participating in endurance events had very high &OV0312;o2max and predominantly slow twitch (ST) fiber populations whereas weight lifters attained rather low values for &OV0312;o2max and had a higher percentage of fast twitch (FT) fibers. Among subjects with the same fiber composition, &OV0312;o2max was higher in the athletes than in the moderately trained. All groups taken together demonstrated a positive relationship between &OV0312;o2max and the relative number of ST fibers (r = 0.67). For endurance and strength athletes r = 0.72 and for the moderately trained r = 0.34, both correlation coefficients being significant.ENDURANCE, STRENGTH, SKELETAL MUSCLE FIBER TYPES, MAXIMAL OXYGEN UPTAKE, GENETIC FACTORS

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTCOSTILL, D. L., G. P. DALSKY and W. J. FINK. Effects of caffeine digestion on metabolism and exercise performance.Med. Sci. Sports.Vol. 10, No. 3, pp. 155‐158, 1978.—In an effort to assess the effects of caffeine ingestion on metabolism and performance during prolonged exercise, nine competitive cyclists (two females and seven males) exercised until exhaustion on a bicycle ergometer at 80% of &OV0312;o2max. One trial was performed an hour after ingesting decaffeinated coffee (Trial D), while a second trial (C) required that each subject consume coffee containing 330 mg of caffeine 60 min before the exercise. Following the ingestion of caffeine (Trial C), the subjects were able to perform an average of 90.2 (SE ± 7.2) min of cycling as compared to an average of 75.5 (SE ± 5.1) min in the D Trial. Measurements of plasma free fatty acids, glycerol and respiratory exchange ratios evidenced a greater rate of lipid metabolism during the caffeine trial as compared to the decaffeinated exercise treatment. Calculations of carbohydrate (CHO) metabolism from respiratory exchange data revealed that the subjects oxidized roughly 240 g of CHO in both trials. Fat oxidation, however, was significantly higher (P < 0.05) during the C Trial (118 g or 1.31 g/min) than in the D Trial (57 g or 0.75 g/min). On the average the participants rated (Perceived Exertion Scale) their effort during the C Trial to be significantly (P < 0.05) easier than the demands of the D treatment. Thus, the enhanced endurance performance observed in the C Trial was likely the combined effects of caffeine on lipolysis and its positive influence on nerve impulse transmission.LIPID METABOLISM, PERCEIVED EXERTION, CARBOHYDRATE OXIDATION, RESPIRATORY EXCHANGE RATIO

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTPERRINE, JAMES J. and V. REGGIE EDGERTON. Muscle force‐velocity relationships under isokinetic loading.Med. Sci. Sports.Vol. 10, No. 3, pp. 159‐166, 1978.—Various studies have indicated that human musclesin‐vivomanifest a substantially similar, if not the identical force‐velocity relationship established for isolated, maximally stimulated animal muscles. In the present study, fifteen healthy males and females, 18 to 38 years old and representing varied activity patterns from sedentary to athletic, performed maximal dynamic knee extensions on an isokinetic loading dynamometer. Maximal torque forces attained at a specific point in the range (30° before full extension) and at seven loading velocities from 0 (isometric) to 288° /sec were recorded. The maximum 30° torques exhibited by the various subjects ranged from 29 to 245 Newton‐meters. However, over the four lower test velocities (0, 48, 96 & 144° /sec), all subjects exhibited less than a 15% deviation from their respective maximum 30° torque values, which occurred most often at the 96° /sec test velocity. Maximal instantaneous power output at the 30° position ranged from 98 to 680 Watts. In all 15 subjects this was attained at and remained generally constant over the three highest test velocities (192 to 288° /sec). A neural mechanism that restricts a muscle's maximal tensionin‐vivois postulated as being responsible for the marked difference between the force‐velocity relationship found for human musclesin‐vivoand that exhibited by isolated animal muscles.FORCE‐VELOCITY VS. LOAD‐VELOCITY, POSITION AND VELOCITY‐SPECIFIC FORCES, INSTANTANEOUS POWER OUTPUT, EXCITATION INTENSITY, NEUROMUSCULAR INHIBITION

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTWILSON, BRIAN A., and WENDELL N. STAINSBY. Effects of O2breathing on RQ, blood flow, and developed tension in in situ dog muscle.Med. Sci. Sports.Vol. 10, No. 3, pp. 167‐170, 1978.—The &OV0312;o2, &OV0312;CO2, RQ, blood flow and developed tension of in situ dog gastrocnemius muscle were studied during contractions at 2.5 tw/sec for both normoxic and hyperoxic breathing conditions. &OV0312;o2and developed tension were not significantly altered by the breathing gas changes. CaO2rose by 11% during O2‐breathing, however, a significant decrease of 15% in muscle blood flow resulted in no significant change in O2‐transport (CaO2X Q) to muscle comparing hyperoxia to normoxia. Hyperoxia resulted in a significant decrease in muscle &OV0312;CO2and RQ. The cause of the RQ change with breathing gas O2content is not certain, however, evidence is presented indicating that infused epinephrine and propranolol can effect the response.MUSCLE METABOLISM, HYPEROXIA, MUSCLE TWITCH CONTRACTIONS, LOCAL FLOW CONTROL

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTGETTMAN, LARRY R., JOHN J. AYRES, MICHAEL L. POLLOCK, and ANDREW JACKSON. The effect of circuit weight training on strength, cardiorespiratory function, and body composition of adult men.Med. Sci. Sports.Vol. 10, No. 3, pp. 171‐176, 1978.—The purpose of this study was to determine the changes elicited by circuit weight training (CWT) and running (RN) programs conducted 3 days/week for 20 weeks. Subjects were randomly assigned to one of three groups: CWT (n = 11); RN (n = 16); and control (n = 14). CWT consisted of 10 exercises performed in 2 sets of 15 reps with 20 to 25 sec rest between exercises. CWT workout time decreased from 30 min to 23 min; exercise heart rate (HR) increased from 79% to 84% max; average weight increased from 42% to 56% of max 1 RM strength and total weight increased 81% (1506 to 2720 lbs/workout). The RN group exercised at 85% max HR for 23 to 27 min/workout. Multivariate and step‐down analyses showed the CTW group to be significantly different from the control group at the end of 20 weeks in leg press strength, fat weight, and &OV0312;o2max (1/min). The RN group was significantly different from the CWT group in &OV0312;o2max and treadmill time. Univariate analyses revealed no differences between the CWT and control groups in &OV0312;o2max expressed as ml/kg LBW•min but did show a significant superiority of the RN group over the other two groups in this variable. It was concluded that the CWT program was most specific in improving strength and changing body composition and produced only a small aerobic effect as measured on the treadmill running test.STRENGTH TRAINING, MAXIMUM OXYGEN UPTAKE, RUNNING

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTPINEL, JOHN P.J., and TERRY D. SCHULTZ. Effect of antecedent muscle tension levels on motor behavior.Med. Sci. Sports.Vol. 10, No. 3, pp. 177‐182, 1978.—In Experiment 1 there was an appreciable elevation in the levels of electromyographic activity recorded from the right forearm flexor of intercollegiate wrestlers prior to an important competition. With the aid of biofeedback, subjects in the second experiment maintained these same elevated levels of electromyographic activity before performing a battery of simple motor tasks. These elevated levels of antecedent muscle tension were found to disrupt hand steadiness and grip strength. Thus, the high levels of pre‐competition muscle tension occurring in athletes are capable of disrupting performance. The use of biofeedback relaxation techniques in the pre‐competition period may significantly improve the performance of competitive athletes hampered by particularly high levels of pre‐competition muscle tension.BIOFEEDBACK, ELECTROMYOGRAM, WRESTLING, REACTION TIME, GRIP STRENGTH, HAND STEADINESS

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTGREEN, H.J. Glycogen depletion patterns during continuous and intermittent ice skating.Med. Sci. Sports.Vol. 10, No. 3, pp. 183‐187, 1978.—The glycogen depletion patterns in the vastus lateralis muscle were studied during ice skating using eight hockey players. For each subject, exercise consisted of either repeated bouts (10) of high intensity work (120% &OV0312;o2max) or continuous work (60 min) of low intensity (55% &OV0312;o2max). During continuous skating, glycogen showed a 29% decline (p<0.05) over the 60 min. In the intermittent condition, there was a two fold greater depletion (p<0.05) with the most rapid loss occurring during the first five, one min work bouts. Histochemical analysis by fiber type indicated that the most pronounced glycogen loss was from the Type I fibers during continuous skating whereas during the intermittent condition, a preferential loss occurred in the Type II fibers, most notably the Type IIB fibers. Measurements of muscle metabolites during continuous skating indicated no change for ATP from the rest condition at 30 or 60 min, a reduction (p<0.05) in CP (4.1 mmoles•kg‐1) at 60 min and an elevation (p<0.05) in lactate (0.85 mmoles•kg‐1) at 60 min. In the intermittent condition, reductions (p<0.05) in ATP (0.47 mmoles•kg‐1) and CP (8.7 mmoles•kg‐1) and elevations (p<0.05) in lactate (21.7 mmoles•kg‐1) were found following 5 work bouts. Thereafter, no significant changes were observed. It is concluded that the glycogen depletion patterns and alteration in muscle metabolites are similar to those seen during cycling at similar percentages of &OV0312;o2max.VASTUS LATERALIS, ATP, CP, LACTATE, TYPE IIA, IIB FIBERS, CONTINUOUS, INTERMITTENT, ICE SKATING

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTBLIMKIE, CAMERON J. R., DAVID A. CUNNINGHAM AND FRED Y. LEUNG. Urinary catecholamine excretion during competition in 11 to 23 year old hockey players.Med. Sci. Sports.Vol. 10, No. 3, pp. 183‐193, 1978.—Stress experienced by young athletes (ages 11 to 23 years) during competition was studied by comparing urinary epinephrine (E) and norepinephrine (NE) excretion at rest, during bicycle exercise (55% max) and during a hockey game. Athletes were divided into four groups: 11, 12, 16, and 23 year olds with four subjects in each group. Urinary production rates were similar between experimental conditions and age groups. Both resting E and NE levels were constant across all ages. Game E levels were significantly higher (P<0.05) than resting and bicycle levels in both the 16 and 23 year old groups. Epinephrine excretion during hockey was also significantly higher (P<0.05) in the 23 year old athletes than in the 11 and 12 year olds and in the 16 year olds compared to the 11 year olds. Game NE was significantly elevated (P<0.05) above resting levels in the 16 and 23 year olds. Submaximal NE excretion was not significantly different from resting levels in any of the age groups (P>0.05). Physical stress as reflected by NE excretion was constant across all ages within each experimental condition. Generally, sympathetic stimulation and NE excretion appeared to be related to intensity of physical activity, being greater during hockey than during submaximal exercise. Significant adrenal medullary activation and E excretion was evident only during hockey and then, only in the older athletes.SUBMAXIMAL EXERCISE, HOCKEY GAME, EPINEPHRINE, NOREPINEPHRINE, LACTATE, EMOTIONAL STRESS, PHYSICAL STRESS

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTCURETON, K.J., P.B. SPARLING, B.W. EVANS, S.M. JOHNSON, U.D. KONG, and J.W. PURVIS. Effect of experimental alterations in excess weight on aerobic capacity and distance running performance.Med. Sci. Sports.Vol. 10, No. 3, pp. 194‐199, 1978.—To experimentally investigate the effect of excess body weight or fat on maximal oxygen uptake (&OV0312;o2max) and distance running performance, the metabolic response to maximal and submaximal treadmill running and the 12‐min run performance were measured in six subjects under each of four added‐weight (AW) conditions: normal body weight and 5, 10, and 15% additional external weight, added to the trunk. AW was found to systematically and significantly decrease &OV0312;o2max expressed relative to the total weight carried (ml/min•kg TW), maximal treadmill (TM) run time and 12‐min run distance, but not to systematically affect &OV0312;o2max (l/min) or &OV0312;o2max (ml/min•kg FFW). An increase of 5% AW was found, on the average, to decrease &OV0312;o2max (ml/min•kg TW) 2.4 ml, the TM run time 35 sec and the 12‐min run distance 89 m. These decreases were a direct consequence of the increased energy cost of running at submaximal speeds. It was concluded that changes in excess body weight can influence &OV0312;o2max expressed relative to body weight and distance run performance independent of any change in cardiovascular capacity. Failure to distinguish the metabolic effects of body fatness from the influence of cardiorespiratory capacity may result in misleading interpretation of distance run test scores.BODY COMPOSITION, MAXIMAL OXYGEN UPTAKE, ENDURANCE PERFORMANCE

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

ABSTRACTDANIELS, J., N. OLDRIDGE, F. NAGLE and B. WHITE. Differences and changes in &OV0312;o2among young runners 10 to 18 years of age.Med. Sci. Sports.Vol 10, No. 3, pp. 200‐203, 1978—Twenty young males, all active in middle‐distance running, were studied between January 1968 and May 1974 for the purpose of gathering longitudinal data regarding &OV0312;o2during treadmill running. &OV0312;o2submax (measured during the last 2 min of a 6‐min run at 202 m/min) and &OV0312;o2max values (measured during a 5‐8 min increasing‐speed run to exhaustion) were collected approximately every 6 months for 6 years. Different groups, starting at ages of 10, 12 and 13 years were followed for periods of 2 to 5 years continuously. In all longitudinal comparisons, &OV0312;o2max (ml/min) changes paralleled changes in body weight; consequently, &OV0312;o2max (ml/kg•min‐1) did not show a significant change. In every group &OV0312;o2submax (ml/kg•min‐1) dropped significantly over time. All data were pooled by 1 yr age groups, providing cross‐sectional data for active boys 10‐18 yrs of age. &OV0312;o2max ranged from 1933 ml/min for 10‐yr olds to 4082 for 18‐year olds. Concurrent changes in weight resulted in no significant differences in &OV0312;o2max (ml/kg•min‐1) from the overall mean of 61.5. &OV0312;o2submax (ml/kg•min‐1) was highest among 10‐year olds (53.3) and lowest among 18‐yr olds (42.5). Based on these longitudinal and cross sectional findings and significant improvements in times for 1‐ and 2‐mile races, it was concluded that &OV0312;o2max (ml/min) increases no faster than does body weight among moderately active growing boys and that both age and training contribute to a change in &OV0312;o2submax; a factor which accounts greatly for improvements in middle‐distance race performance.&OV0312;o2max, &OV0312;o2submax, aerobic demands of running, growth and &OV0312;o2, growth and performance, age and &OV0312;o2

ISSN:0025-7990    

出版商:OVID    

年代:1978

数据来源: OVID