摘要:

A theoretical model was developed to identify anthropometric variables relevant to success in swimming. Frontal areas, cross-sectional areas (XSA), and lengths of body segments were measured oh twelve members of a men's college team using a photographic procedure. Motion-picture films were taken of the subjects competing in freestyle events and were analyzed to determine the average stroke length (S&OV0226;), average stroke frequency (S&OV0460;), and average stroking speed (&OV0408;). Correlation arid multiple regression procedures were used to determine the relationships among the anthropometric variables and S&OV0226;, S&OV0460;, and &OV0408;, respectively. Of the 21 anthropometric variables selected with the aid of the theoretical model, 6 were found to be significantly related to one or more of the measures of swimming performance when the influence of event distance was partialled out (P≤ 0.05). The anthropometric variables characterizing the subjects accounted for 89% (S&OV0226;), 41% (S&OV0460;), and 17% (&OV0408;) of the variances in the measured characteristics of their strokes. The axilla XSA was shown to have the largest influence on both S&OV0226; and S&OV0460;, accounting for 57% of the variance in the S&OV0226; and 24% in the S&OV0460;. These results suggest that although &OV0408; is little influenced by the physique of a swimmer, the combination of S&OV0226; and S&OV0460; used to attain a given &OV0408; is very much a function of his physique.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Alterations in Golgi tendon organs' (Ib afferent receptors) stretch sensitivity were assessed in fatigued gastrocnemius muscle of cats. Muscle fatigue to 60–50% peak tension was induced in 13 cats by electrical stimulation of L7and S1ventral roots. Forty-three group Ib afferent fibers were recorded in L7or S1dorsal root filaments before and during fatigue. Fiber activity was assessed by applying to the Achilles tendon a 5-mm ramp stretch at 5 or 25–30 mm·s-1. Group Ib afferent responses to both velocities of stretch were either completely abolished or depressed over several seconds compared to pre-fatigue firing frequencies. When responding, longer latencies (measured at 5 mm·s-1only) to firing onset occurred during fatigue. Increasing the rate of stretch (250 mm·s-1) to produce a 5-mm stretch approximately equivalent to twitch tension time revealed a depression more selective to static stretch sensitivity. Post-excitation depression of the Ib receptor potential appears to be one possible mechanism. These acute adaptations in Ib afferent discharge to muscle stretch were opposite in direction to those recently reported in fatigued muscle for group la and group II muscle spindle afferents. Functional implications of these results are discussed.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In this study 11 subjects performed exercise resulting in delayed onset muscular soreness in m. gastrocnemius with one leg, the experimental leg. The other leg served as control. Pre-exercise and 24, 48 and 72 h postexercise, soreness perception, resting EMG level of m. gastrocnemius, and volume and skin temperature of both legs were measured, and a leukocyte count was performed. Perception of soreness in m. gastrocnemius reported 24, 48, and 72 h postexercise was not accompanied by an increase in resting EMG level. This result indicates that soreness perception is not related to a tonic localized spasm in sore muscles. A rise in volume of the experimental leg relative to volume of the control leg was found 24, 48, and 72 h postexercise (P< 0.05). It is suggested that the volume rise is due to edema formation in the experimental leg and that this edema formation is responsible for soreness perception. Since granulocytosis was not found, the hypothesis that edema formation reflects muscle inflammation is not substantiated.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The present study examines the acute effects of two different exercise intensities on erythrocyte 2,3;diphosphoglycerate (2,3-DPG) concentration. Thirty-one females (&OV0398; ± SD age = 23.7 ± 3.37 yr; &OV0312;O2max= 44.3 ± 5.40 ml · kg-1· min-1) completed 2 separate 15-min constant load cycling tests at exercise intensities representing 35 and 75% of &OV0312;O2max. Venous blood was obtained pre-exercise (PRE), immediately post-exercise (POST), 15 min post-exercise (POST 15), and 30 min post-exercise (POST30) to determine lactic acid, 2,3-DPG, and hemoglobin concentrations and hematocrit. Significant increases (P< 0.01) in lactic acid concentration (1.1 ± 0.14 at PRE to 6.2 ± 0.48 m·mol-1·l-1at POST), 2,3-DPG concentration (1.9 ± 0.06 at PRE to 2.1 ± 0.06 ¶mol·ml-1at POST), and 2,3-DPG corrected for plasma volume shift (PVC 2,3-DPG) (1.9 ± 0.06 at PRE to 2.4 ± 0.07 ¶mol · ml-1at POST 15) were observed only following the 75% submaximal exercise. At POST30 (75% &OV0312;O2max) PVC 2,3-DPG and lactic acid remained 5.3 and 97% (P< 0.05) above baseline, respectively. An exercise intensity effect was observed only in lactic acid response (P< 0.05) but not in 2,3-DPG (¶mol·ml-1and μmol·g-1hemoglobin or PVC 2,3-DPG. A significant time-intensity interaction (P< 0.05) for PVC 2,3-DPG suggests that PVC 2,3-DPG response over time was different between the two exercise intensity levels, with the 75% intensity eliciting a greater increase in PVC 2,3-DPG. However, it is concluded that 15-min acute constant-load exercise at low and high intensities does not alter 2,3-DPG (¶mol · g-1hemoglobin) concentration.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The purpose of this study was to compare the effects of exercise and/or caloric restriction for 12 wk on body composition, maximal aerobic power (VO2max), and serum lipids and lipoproteins in overweight individuals. Forty-eight males and 48 females (&OV0398; age = 36.6 yr), 120–140% of ideal body weight, were randomly assigned to groups (N = 12 each) of diet-exercise (DE), diet (D), exercise (E), and sedentary control (C). The dietary regimen consisted of 1,200 kcal·d-1, while exercise consisted of 5 d·wk-1of 30 min of walk/ running. For the males, body weight (BW) and fat weight loss in the DE group (-11.8 and 23%, respectively) were significantly greater than in the D group (-9.1 and −18%), with both groups significantly greater than for E and C. In the females, BW and fat weight loss for DE (-10.4 and −24%) were significantly greater than for D (-7.8 and −20%), with both groups significantly greater than E and C. Both DE and D males and females had a decrease in fat-free weight of −4.5 and −2.4%, respectively. In both sexes, the increase in &OV0312;O2max-BW(ml·kg-1·min-1) in DE(25%) was significantly greater than for E (15%), D (11%), and C (0%), with differences between E and D nonsignificant. However, increases in absolute &OV0312;O2max(1·min-1) and &OV0312;O2max-fat-free weight (ml·kg-1·min-1) were similar (P≥ 0.05) for DE and E (14%) but significantly greater compared to D and C (2%). The DE males had significant decreases in total cholesterol and very low-density lipoprotein cholesterol after weeks 4, 8, and 12 and in triglycerides after weeks 8 and 12. In the DE females, triglycerides were significantly decreased after weeks 4 and 8. High-density lipoprotein cholesterol remained constant across time for all groups of males (35.8 ± 7.4 mg·dl-1) and females (47.8 ± 10.7 mg·dl-1), respectively. Thus, in overweight men and women, DE will produce a greater loss of BW and fat weight and a greater increase in &OV0312;O2maxcompared to D alone. High-density lipoprotein cholesterol is unaffected by diet and/or exercise, while triglycerides and very low-density lipoprotein cholesterol may be decreased.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Young, healthy, previously inactive men were trained aerobically 40 to 50 min·d-1, 5 d·wk-1for 15 wk. They were randomly assigned to one of three medication groups: placebo, propranolol (160 mg·d-1), or atenolol (100 mg·d-1). All subjects lost weight and decreased relative body fat as a result of training. Following training, submaximal steady-state heart rates were reduced in ail groups. Maximal oxygen uptake and maximal treadmill times were also increased in all groups. The &OV0312;O2maxof the placebo increased 18.4%. While that of the atenolol group increased 19.4%, the propranolol group went up 17.0%. Aftertraining the maximal heart rate did not change in the placebo group, while treatment with propranolol and atenolol reduced at 24.6 and 21.9%, respectively. Training caused a significant decrease in the natural killer cell activity in all three groups. The placebo group had 38.8% ± 3.8 (SD) before and 29.3 ± 3.2% lysis of target cells by natural killer cells after physical conditioning, which was significantly lower (P< 0.01). The groups treated with propranolol and atenolol were also similarly decreased. The use of propranolol or atenolol had no additional significant effect on natural killer cell activity. T-cell mitogenesis stimulated with a mitogen significantly increased with conditioning. The groups given atenolol or propranolol tended to increase somewhat more than the placebo group, although this difference was not statistically significant. There was no significant change in the percentage of total lymphocytes isolated due to training or blockade. The number of mature T-lymphocytes measured by the E-rosetting technique increased significantly consequent to physical conditioning, with propranolol and/or atenolol having no additional effect. The placebo group had 65 ± 1.3% of lymphocytes as T-lymphocytes before and 74 ± 1.4% after conditioning (P< 0.05). The increased percentage of lymphocytes which formed E-rosettes (mature T-lymphocytes) occurred as activity of the natural killer cells declined. This suggests that exercise training may influence the maturation and/or function of cells of the cellular immune system.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The purpose of these experiments was to determine the effects of oral caffeine ingestion on the kinetics of oxygen uptake (VO2), expired carbon dioxide output (&OV0312;CO2), and expired ventilation (VE) in the transition from rest to exercise. Nine male subjects underwent three repetitions of constant load cycle ergometer exercise (≈80% ventilatory threshold) on two occasions. A single blind experimental procedure was followed, with one trial being performed 60 min after the subject ingested caffeine (7 mg·kg-1), while the second trial required the subject to ingest a placebo with the treatment order being counterbalanced. Ventilation and gas exchange were monitored by open circuit techniques. The data from three repetitions of the same protocol were pooled and modeled with a single-component exponential function incorporating a time delay:δf(X)t = δf(X)ss(1 - e-(t-TD/r))Kinetic analysis of &OV0312;O2revealed no significant difference (P> 0.05) in the mean response time between treatments. In contrast, the mean response time for &OV0312;CO2and &OV0312;Ewere longer (P< 0.05) for the caffeine trial when compared to the control experiment. These data suggest that caffeine will influence both &OV0312;CO2and &OV0312;Ekinetics in the transition from rest to work and should be considered by investigators when planning experiments to study ventilatory and gas exchange kinetics during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Recent reports have suggested that running economy (RE) defined as oxygen consumption at standardized treadmill speeds may be an important determinant for successful distance running performance. The purpose of this study was to examine the additional role, if any, played by anaerobic factors in distance running performance. Highly trained male cross-country runners (N = 12) were administered a battery of standardized aerobic and anaerobic laboratory evaluations. Maximal oxygen uptake (&OV0312;O2max) and RE (ml · kg-1) were measured using open circuit spirometry during treadmill exercise. RE was measured at 241 and 295 m·min-1, and ventilatory threshold (Tvent) was determined and verified using a number of non-invasive ventilatory measures (&OV0312;E, &OV0312;E/&OV0312;O2, &OV0312;E/&OV0312;CO2, &OV0312;CO2, FECO2). Anaerobic measures included the Margaria power test and the Monod critical power test to determine anaerobic work capacity (AWC). The data were subjected to a SAS-STEPWISE analysis which combines stepwise addition and backward elimination and were used to predict performance time in a 8.05-km (5-mile) cross-country race in which all the runners participated. The subjects averaged 26.21 min for the 8.05 km run, with 72.1 ml · kg-1· min-1for the &OV0312;O2maxwith a Tventat 60.4 ml · kg-1· min-1(84% &OV0312;02max). AWC (Monod) was 17400 Joules with a range of 8,000–28,400 Joules. The STEPWISE procedure reveals that AWC contributes significantly (P< 0.003) to a 3 variable model predicting race performance (R2= 0.76,P< 0.01). AWC accounts for 58% of total shared variance with &OV0312;O2maxand an indirect measure of Tventaccounting for the remaining 17%. The results of this study underline the importance of a multifactorial approach to predicting race performance and the contribution of anaerobic systems to success in cross-country race performance.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Ten male subjects underwent exercise testing in three modes, arms (A), legs (L), and arms + legs (A + L), after ingesting 0.3 g·kg-1body weight of either NaHCO3to induce alkalosis or CaCO3 as a placebo (i.e, six exercise trials). Ratings of perceived exertion (RPE: Borg, 15-pt scale) for the arms (RPE-A), legs (RPE-L), chest (REP-C), and overall body (RPE-O) did not differ between acid-base conditions at 20, 40, or 60% &OV0312;O2maxfor all three exercise modes. At 80% &OV0312;O2max, 1) RPE-A was lower (P< 0.01) during A; 2) RPE-L was lower (P< 0.01) during L; and 3) RPE-A and RPE-L were lower (P< 0.01) during A + L under the NaHCO3as compared to the CaCO3condition. Differences were not found for RPE-L during A or for RPE-A during L. RPE-C and RPE-O were lower (P< 0.01) under NaHCO3during A, L, and A + L. Blood acid-base, &OV0312;O2, and cardiorespiratory responses were not differentially influenced by exercise mode. Blood pH was significantly higher under NaHCO3than CaCO3at pre-exercise and 80% &OV0312;o2max, &OV0312;o2, heart rate, and tidal volume did not differ between acid-base conditions at any exercise intensity. &OV0312;Eand respiratory rate did not differ between acid-base conditions at 20,40, or 60% &OV0312;o2maxbut were significantly lower under NaHCO3at 80% &OV0312;o2max. RPE-A and L were positively related to blood [H+], and RPE-C was positively related to &OV0312;Efor all exercise modes.

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The purpose of this study was to characterize triathletes and to assess their responses to prolonged, strenuous competition, Nine triathletes (6 males, 3 females) participated. Mean &OV0312;02maxand percentage of body fat were 72.0 ml·kg-1·min-1and 7.1%, respectively, in the four males who finished in the top 15. This compared to values of 58.4 ml·kg-18min-1/10.2% and 58.7 ml·kg-1·min-1/12.6% in the other males and females, respectively. In the 5 wk preceding competition (Hawaii “Ironman Triathlon World Championship”) the average daily training of the four top 15 male competitors consisted of swimming 2720 m, running 13.6 km, and biking 84.0 km. This was approximately 1.5 times greater than that of the other athletes. The average training diet was 59% carbohydrate, 21% fat, and 20% protein. Immediately following competition, SGOT, SGPT, and serum LDH were increased 700, 262, and 222% (P< 0.004), respectively, and still remained marginally elevated 5–6 d later (P< 0.02). Immediately following competition, serum triglycerides remained unchanged, while serum glucose, glycerol, and nonesterified fatty acids increased 52, 248, and 191% (P< 0.005), respectively. By 5–6 d post-competition glucose had returned to normal, while triglycerides were elevated 94% (P< 0.005) and nonsterified fatty acids were decreased 58% (P< 0.01).

ISSN:0195-9131    

出版商:OVID    

年代:1986

数据来源: OVID