摘要:

MITTLEMAN, K. D. and E. J. ZAMBRASKI. Exercise-induced proteinuria is attenuated by indomethacin.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1069–1074, 1992. The role of the prostaglandin (PG) and renin-angiotensin hormonal systems in exercise-induced proteinuria following 30 min of submaximal, steady-state exercise was evaluated. Eight healthy males performed cycle ergometry at 75% of &OV0312;O2peakon three occasions after the administration of a placebo (PLACEBO), a prostaglandin inhibitor (indomethacin, INDO), and an angiotensin converting enzyme inhibitor (captopril, CAPTO). Urine and blood samples were collected prior to, immediately following exercise, and over 40-min recovery. Data were evaluated for differences among drug treatments and measurement phases. During PLACEBO, exercise increased total protein excretion from 64.9 ± 9.5 to 408.6 ± 160.8 μg·min-1(P< 0.05). PG inhibition with INDO significantly attenuated the increased proteinuria due to exercise (149.2 ± 64.0 μg·min-1). The proteinuric response to exercise was not altered by CAPTO. Resting plasma renin activity (PRA) and aldosterone (ALDO) were significantly reduced during the INDO trial. Although the twofold increment in ALDO with exercise remained intact during the INDO trial, the PRA response to exercise was significantly blunted. No treatment differences were observed for mean arterial pressure, sodium excretion, urine flow, or creatinine clearance values during rest or exercise. These results suggest that the proteinuria associated with steady-state exercise is PG dependent and not related to hemodynamic influences.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

GRABINER, M. D., T. J. KOH, and G. F. MILLER. Further evidence against a direct automatic neuromotor link between the ACL and hamstrings.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1075–1079, 1992. The purpose of this experiment was to determine whether reflexive, or more broadly, automatic hamstrings excitation could be elicited during isometric, maximum effort, step increases in knee extension torque. Eight healthy subjects without lower extremity dysfunction or injury performed maximum effort isometric knee extension at 15 and 85 degrees of knee flexion in minimum elapsed time. Surface electromyography was used to record medial (semi-membranosis and semitendinosis) and lateral (biceps femoris—long head) hamstrings excitation that was subsequently normalized to the excitation during maximum isometric knee flexion. To assess whether automatic hamstrings excitation was elicited, the amplitude of the EMG signals was analyzed and compared for 50 ms prior to peak knee extension torque, and three consecutive 50 ms windows following peak knee extension torque. The amplitude of the EMG subsequent to the peak knee extension torque failed to support the contention of an automatic hamstrings excitation mediated by neural circuitry from the ACL. The present results, in conjunction with previous work, suggest that a protective automatic hamstrings contraction is not normally elicited in response to conditions subjecting the anterior cruciate ligament to strain.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

KOHL, H. W., Ill, N. F. GORDON, C. B. SCOTT, H. VAANDRAGER, and S. N. BLAIR. Musculoskeletal strength and serum lipid levels in men and women.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1080–1087, 1992. There currently is inconsistent information regarding the role that musculoskeletal strength (one component of musculoskeletal fitness) may have in lipid and lipoprotein metabolism, and consequently the risk of cardiovascular disease. Results of existing studies have been conflicting and have been influenced by several weaknesses. We provide cross-sectional analyses of the relation between muscular strength and serum lipid and lipoprotein status in a group of 1,193 women and 5,460 men. The large proportion of patients were not involved in formal weight training. As part of a preventive medical examination, patients were tested for maximal upper and lower body strength (one repetition maximum (1RM) bench and leg press). Fasting serum total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), triglyceride (TG), and high density lipoprotein (HDLC) were evaluated for their relation to muscle strength, after adjusting for simultaneous associations with age, body composition, and cardiovascular fitness. Results showed no association between muscular strength and serum TC or LDLC for either men or women and a direct association between upper and lower body strength and TG in men. The direct association between strength and TG in women was not significant. A statistically significant inverse association was seen between muscular strength and HDLC in men only. These data suggest no beneficial effect, and perhaps an adverse association of muscular strength on lipid and lipoprotein status.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

HAGAN, R. D., S. E. WEIS, and P. B. RAVEN. Effect of pedal rate on cardiorespiratory responses during continuous exercise.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1088–1095, 1992. The role of cycle ergometer pedal rate on the gradual increase in ventilation (&OV0312;E), heart rate (HR), and oxygen uptake (&OV0312;O2) accompanying continuous submaximal exercise is unknown. To examine this problem, five trained males (&OV0312;O2peak= 4.00 ± 0.27 1-min-1) performed 45 min of moderate intensity (MI, 127 W) and high-moderate intensity (HMI, 166 W) cycle ergometry both at pedal rates of 60 rpm and 90 rpm. Power output and pedal rate had an additive effect on the overall mean responses for &OV0312;E, HR, and &OV0312;O2, producing significantly higher values as power output and pedal rate increased. During continuous exercise, &OV0312;E, HR, and &OV0312;O2increased progressively from the 10th to the 45th minute for all tests. However, the rates of increase and factors modifying the &OV0312;E, HR, and &OV0312;O2responses were different. HR increased during all exercise tests an average of 10.8% independent of power output and pedal rate. &OV0312;Eincreased 7.4% during MI exercise and 10% during HMI exercise independent of pedal rate. Similar power output dependent responses were observed for rectal temperature (Tr) and blood lactate. &OV0312;O2increased 4.4% for MI and HMI exercise at 60 rpm, and 8.2% for the same power outputs at 90 rpm, respectively. Increases in Tr, the oxygen cost of pulmonary ventilation and fat oxidation, and lactate removal were estimated to account for only 31–36% of the slow rise in &OV0312;O2for any single test. This suggests that 64–69% of the rise in &OV0312;O2was due to factors related to muscle use. Our findings suggest that increases in HR during continuous exercise are influenced by thermoregulatory factors independent of exercise intensity and leg pedal rate. However, fast pedal rates potentiate the rate of &OV0312;o2increase, while power output potentiates the rate of increase for &OV0312;E. These findings suggest that gradual increases in respiration and energy expenditure during continuous cycle ergometry are influenced differentially by neuromuscular reflex mechanisms related to power output and pedal rate.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

DENGEL, D. R., P. G. WEYAND, D. M. BLACK, and K. J. CURETON. Effect of varying levels of hypohydration on responses during submaximal cycling.Mecl. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1096–1101, 1992. The effect of varying levels of hypohydration on hemodynamic, cardiorespiratory, and metabolic responses to progressive incremental submaximal cycling was examined in nine male subjects. Subjects cycled in a neutral (22°C) environment under euhydration (EU), moderate hypohydration (MH), and severe hypohydration (SH). To achieve the desired level of hypohydration, subjects cycled at 50% &OV0312;O2maxfor 1.5 h in a 38°C environment on two separate occasions, 36 h prior to testing. Mean (+SE) percent losses in body weight from baseline during EU, MH, and SH were 0.6 ± 0.3%, 3.3 ± 0.1%, and 5.6 ± 0.4%, respectively. Ventilation, O: uptake, respiratory exchange ratio, heart rate, plasma free fatty acids, plasma glycerol, blood lactate, and hematocrit were not significantly altered by hypohydration. During EU, hemoglobin concentration was significantly lower than during both MH and SH, but no significant difference was observed for plasma volume loss. Plasma glucose was significantly higher during SH compared with EU and MH. These results suggest that hypohydration of up to 5.6% caused by exercise and fluid manipulation over 36 h docs not alter cardiorespiratory or blood lactate responses during progressive incremental submaximal cycling in a neutral environment. However, hepatic metabolism may be altered during hypohydration as indicated by higher plasma glucose levels.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

HOWARD, M. C, S. E. DICARLO, and J. N. STALLONE. Acute exercise attenuates phenylephrine-induced contraction of rabbit-isolated aortic rings.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1102–1107, 1992. Factors associated with a single bout of dynamic exercise (increased circulating catecholamines, increased body temperature, and decreased pH) are known to attenuate the vascular response to n-adrenergic receptor activation. Therefore, we postulate that an acute bout of dynamic exercise may decrease the vascular response to catecholamines. To test this hypothesis, we evaluated contractile responsiveness to phenylephrine (PE) in aortae of two groups of New Zealand white rabbits, a control group (no exercise) and an exercise group (treadmill running, 24m·min-1; 16 ± 2.0 min). Aortic rings were prepared from age-matched control (N= 6) and exercise rabbits (N= 5) and mounted for isometric tension recording (in Krebs-Henseleit-bicarbonate solution, 37°C, 1.5 g passive tension). After equilibration (2 h) a cumulative concentration-response curve to PE (10-7M-10-2M) was obtained. The results demonstrate that a single bout of dynamic exercise attenuates (P< 0.05) the maximal contractile tension (2,457 ± 120 vs 3,620 ± 321 mg tension·mg-1ring wt), gain (602 ± 31 vs 878 ± 87 mg·M-1PE), and rate of contraction (6.2 ± 0.3 vs 4.7 ± 0.3 mg tension-s-1). In addition, contraction threshold was significantly increased in exercise (2.6 ± 0.4 × 10-6M) vs control aortae (1.03 ± 0.4 × 10-6M). A single bout of dynamic exercise did not alter the contractile response to 70 mM KC1 (3,555 ± 270 vs 3,083 ± 233 mg tension·mg-1ring weight). These data suggest that an acute bout of dynamic exercise significantly attenuates α-adrenergic receptor-mediated contraction of vascular smooth muscle.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

BOONE, J. B. JR., M. LEVINE, M. G. FLYNN, F. X. PIZZA, E. R. KUBITZ, and F. F. ANDRES. Opioid receptor modulation of post-exercise hypotension.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1108–1113, 1992. Previous studies of both hypertensive and normotensive individuals have indicated a prolonged reduction in blood pressure for several hours after aerobic exercise. In related studies of spontaneously hypertensive rats, this postexercise hypotension has been prevented with naloxone. The purpose of the present investigation was to examine whether the postexercise hypotension may be reversed by antagonism of opioid sensitive receptors with naloxone in normotensive humans. Eight males 22–34 yr of age, participated in two 60-min cycling trials at 60% of &OV0312;O2peak, followed by 29 min of recovery. Beginning at 7-min recovery, naloxone or saline (control) was administered intravenously through an indwelling catheter. Blood pressure and heart rate were monitored every 15 min during exercise and every 2 min during recovery. Heart rate was significantly elevated. (P< 0.05) over basal levels for the first 11 min of recovery, but from 13 to 29 min was not different from that measured at rest. In both trials, after 11 min of recovery, systolic and mean arterial blood pressures were significantly (P< 0.05) lower than pre-exercise levels (9 ± 1 mm Hg and 4 ± 1 mm Hg, respectively). Injection of naloxone (0.1 mg·kg-1) reversed the hypotensive response. However, the reversal was transient, lasting from minutes 15 to 27. Since naloxone reverses postexercise hypotension, opioid sensitive receptors appear to be involved in the reduction in systolic blood pressure following a single bout of submaximal exercise in normotensive humans.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

HULL, M. L, M. WILLIAMS, K. WILLIAMS, and S. KAUTZ. Physiological response to cycling with both circular and noncircular chainrings.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1114–1122, 1992. The purpose of this study was to compare physiological variables of endurance-trained cyclists riding with four different chainring designs: round, Shimano Biopace, and two engineered ellipse designs. The ellipse designated Eng10 had the crank arm oriented 10 degrees forward of the major (i.e. longer) axis. Eighty degrees further forward, along the minor axis, was the crank arm orientation for the second ellipse, Eng90. With the major to minor axis ratio of 22.9 cm/16.8 cm (1.36), both ellipses imposed a crank angular velocity variation of 27% relative to the highest velocity assuming constant chain velocity. Best described as a skewed ellipse (i.e., major and minor axes not perpendicular), the Biopace had a major to minor axis ratio of 1.09 thus giving a crank angular velocity variation of 8%. Eleven male cyclists rode at a high (80% of maximum&OV0312;O2)and a low (60% of maximum &OV0312;O2) workrate using each chainring. The study was conducted over four consecutive days with the presentation order of the chainrings randomized. Open circuit spirometry was used to collect continuous respiratory data. Heart rate, blood lactate, and cadence values also were measured. None of the physiological variables including rates of oxygen consumption showed significant differences among the chainrings. Thus, the gross efficiency of cycling was not improved by any of the noncircular chainrings. For cycling events where efficiency is a determinant of performance, the noncircular chainrings do not offer any advantage over round chainrings.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

SWAIN, D. P. and J. P. WILCOX. Effect of cadence on the economy of uphill cycling.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1123–1127, 1992. Competitive cyclists generally climb hills at a low cadence despite the recognized advantage in level cycling of high cadences. To test whether a high cadence is more economical than a low cadence during uphill cycling, nine experienced cyclists performed steady-state bicycling exercise on a treadmill under three randomized trials. Subjects bicycled at 11.3 km·h-1up a 10% grade while 1) pedalling at 84 rpm in a sitting position—84 Sit, 2) pedalling at 41 rpm in a standing position—41 Stand, and 3) pedalling at 41 rpm in a sitting position—41 Sit. Heart rate (HR), oxygen consumption (&OV0312;O2), ventilation (&OV0312;E), and respiratory exchange ratio were measured continuously during 5-min trials and averaged over the last 2 min. Additionally, rating of perceived exertion was recorded during the fifth minute of each trial, and blood lactate concentration was recorded immediately before and after each trial. Significantly lower values for HR, &OV0312;O2and VE were recorded during 84 Sit (164 ± 3 bpm, 51.8 ±0.8 ml·min-1·kg-1, 94 ± 5 1·min-1) than for either the 41 Stand (171 ±2 bpm, 53.1 ± 0.7 ml·min-1·kg-1, 105 ± 6 1·min-1) or 41 Sit (168 ±2 bpm, 53.1 ± 0.8 ml·min-1·kg-1, 101 ±61·min-1) trials. No other differences were noted between trials for any of the measured variables. We conclude that uphill cycling is more economical at a high versus a low cadence.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

PATE, R. R., C. A. MACERA, S. P. BAILEY, W. P. BARTOLI, and K. E. POWELL. Physiological, anthropometric, and training correlates of running economy.Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1128–1133, 1992. Potential physiological, anthropometric, and training determinants of running economy (RE) were studied in a heterogeneous group of habitual distance runners (N= 188, 119 males, 69 females). RE was measured as &OV0312;O2(ml·kg-1·min-1) during level treadmill running at 161 m·min-1(6 mph) (&OV0312;O2-6). Examined as potential determinants of RE were heart rate and ventilation while running at 6 mph (HR6, &OV0312;E6), &OV0312;O2max(ml·kg-1·min-1).%fat, age, gender, height, weight, estimated leg mass, typical training pace, training volume, and sit-and-reach test performance. RE was entered as the dependent variable and the potential determinants as independent variables in zero-order correlation and multiple regression analyses. Zero-order correlation analysis found &OV0312;O2max, HR6, and &OV0312;E6 to be significantly, positively correlated with VO2-6 (P< 0.001). Multiple regression analysis, in which the independent effect of each predictor variable was examined, revealed &OV0312;O2-6 to be positively correlated with &OV0312;O:max(P< 0.001), HR6 (P< 0.001), &OV0312;E6 (P< 0.001), and age (P< 0.05) and negatively correlated with weight (P< 0.01). These findings indicate that, in a diverse group of runners, better RE (&OV0312;O2-6) is associated with lower &OV0312;O2max, lower submaximal exercise &OV0312;E and HR, lower age, and greater weight.

ISSN:0195-9131    

出版商:OVID    

年代:1992

数据来源: OVID