一次大负荷跑台运动后大鼠心脏力-电变化和组织病理学观察

目的:观察一次定量大负荷跑台运动后大鼠心脏心肌力-电变化和心肌组织病理学变化。方法:22只心电图正常SD大鼠随机分为对照组(n=8)和运动组(n=14)。采用BL-420E+型四道生理记录仪连续测定运动组一次定量大负荷跑台运动后0、5、10、20、30、50、70、90、110 min的心电图和左心室收缩功能,并于运动后110 min处死;对照组安静状态麻醉测定心电图和左心室收缩功能,麻醉后110 min处死。取材行心肌苏木精-伊红染色。根据运动后的心电变化,又将运动组分为心电异常组(ST段下压为异常,n=8)和心电无异常组(n=6)。结果:(1)大负荷运动后心电异常组大鼠左心室心肌收缩压和最大上升速率的时相变化不同步,运动后20和70 min心肌收缩力出现阶段性低值,而运动后15、90 min时+dp/dtmax出现阶段性低值,运动后110 min均恢复正常。(2)运动后心电异常组心电图出现T波倒置或低平、ST-T下移、J点下移等现象,T波和J点值均在运动后15、50min出现阶段性低值,T波运动后110 min恢复,接近正常,而J点值尚未完全恢复。(3)三组苏木精-伊红染色评分,两两组间比较均无显著性差异。结论:大负荷运动后大鼠心肌组织染色未见病理性改变,大鼠恢复期心脏力-电变化表现为短时可逆性心肌收缩功能障碍和心电异常变化。     

Post-exercise palpation of pulse rates: its applicability to habitual exercisers

Despite the increased popularity of heart rate (HR) monitors, endurance-trained adults as well as habitual exercisers often use pulse rate palpation to periodically monitor exercise intensity. However, due to the rapid recovery of HR following exercise bouts, post-exercise palpation of pulse rates may underestimate exercise HR. To test this hypothesis, we studied 20 young physically active adults performing two sets of exercise for 5 min at 70% and 85% of maximal HR on the treadmill; one with carotid and another with radial pulse count. Post-exercise palpation of pulse rate was lower (P < 0.01) than the actual HR during exercise, underestimating exercise HR by 20-27 bpm (beats per min). Even when ECG tracings of HR were analyzed immediately after exercise (0-15 s), a significant underestimation of exercise HR (7-9 bpm) still persisted (P < 0.05). Following exercise, pulse rate obtained by carotid palpation at both intensities and radial palpation at the lower intensity was no different from the corresponding HR measured with ECG. In the radial artery trial at the higher exercise intensity, pulse rate following exercise was lower (10 bpm; P < 0.05) than ECG-derived HR. Arterial stiffness, which is closely associated with arterial baroreflex sensitivity, was not significantly related to the changes in HR with carotid palpation. We concluded that post-exercise pulse palpations may not be appropriate as an indicator of exercise intensity in habitual exercisers.     

Peak cardiorespiratory responses during aquatic and land treadmill exercise

PURPOSE: Aquatic treadmill exercise has traditionally been used for aerobic training during rehabilitation; however, its ability to elicit comparable cardiorespiratory stress compared with land exercise is unclear. The purpose of this study was to investigate the cardiorespiratory (CR) responses elicited during maximal-effort protocols using an aquatic treadmill (ATM) and a land treadmill (TM). METHODS: Twenty-three college runners participated in two continuous, incremental peak oxygen consumption protocols (ATM and TM) until volitional exhaustion. For the ATM protocol, subjects were submerged in 28 degrees C water to the xiphoid process. ATM speed was increased incrementally to 206.8+/-23.1 m.min, and water jet resistance was increased 10% every minute thereafter. For the TM protocol, speed was increased to 205.3+/-22.3 m.min, and grade was increased 2% every minute thereafter. Rest between sessions was at least 48 h. Oxygen consumption (VO2), heart rate (HR), minute ventilation (VE), tidal volume (VT), breathing frequency (f), and respiratory exchange ratio (RER) were measured continuously, with peak values used for analysis. Rating of perceived exertion (RPE) was recorded immediately after each test, and blood lactate (LA) was measured 3 min afterward. RESULTS: VE and f were significantly greater in ATM versus TM; however, VO2, HR, VT, RER, LA, RPE, speed, and exercise times were similar for both protocols. CONCLUSIONS: Despite differences in VE and f, it seems that the fluid resistance created by water and jets in an ATM elicits peak CR responses comparable with those seen with inclined TM. These findings suggest that ATM running may be as effective as TM running for aerobic conditioning in fit individuals.     

Training responses of plasma beta-endorphin, adrenocorticotropin, and cortisol

The purpose of this study was to examine the effects of three different run training programs on plasma responses of beta-endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol to maximal treadmill exercise. Subjects were randomly assigned to one of three training groups: sprint intervals (SI) (N = 8), endurance (E) (N = 10), or combination (C) (N = 7). Training was monitored for 10 wk, and maximal treadmill exercise tests were administered pre-training and after 2, 4, 6, 8, and 10 wk of training. Blood samples were obtained (pre-training and after 10 wk) before, immediately after, and 5 and 15 min following the maximal exercise tests. All groups significantly (P less than 0.05) increased maximal oxygen consumption values at 8 and 10 wk of the training period. Significant exercise-induced increase in plasma beta-EP, ACTH, cortisol, and blood lactate were observed for both pre- and post-training tests in all training groups. The SI group demonstrated significant post-training increases in beta-EP, ACTH, cortisol, and 5 min post-exercise blood lactate concentrations in response to maximal exercise. No training-induced hormonal changes were observed for the E group. While exercise-induced increases were observed, the C group exhibited significant post-training reductions in plasma responses of beta-EP, ACTH, and blood lactate concentrations in response to maximal exercise. Still, resting and post-exercise increases in plasma cortisol concentrations were significantly higher in magnitude in the post-training test. Lactate was significantly correlated with beta-EP (r = 0.72), ACTH (r = 0.70), and cortisol (r = 0.64).(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic responses associated with four modes of prolonged exercise

The purpose of this study was to compare energy expenditure and substrate utilization during 60 min of steady state-exercise at similar heart rates (HR) using four exercise modes: stationary cycle (C), rower (R), ski simulator (S), and treadmill (walking) (T). Five subjects (means age = 23 +/- 4 yr) performed 60 min of continuous exercise at 65% HR max on each of the four modes in random order. Total energy (TE) and fat energy (FE) expenditure were determined from VO2 and respiratory exchange ratio (RER). VO2 during exercise averaged 2.427 for C, 2.167 for R, 2.242 for S, and 2.420 l min-1 for T and were not significantly different by repeated measures ANOVO (p greater than 0.05). RER, TE, and FE also were not statistically different among exercise modes. However, walking and skiing tended to use more fat; the average 60 min cumulative exercise values were 960 for C, 871 for R, 1088 for S, and 1188 kJ for T. The rate of fat expenditure generally increased after 20 min on all modes. These results indicate that the energy expended at comparable relative HR's is similar for four aerobic exercise modes.     

Children's OMNI Scale of Perceived Exertion: walking/running evaluation

PURPOSE: The Children's OMNI-walk/run Scale of Perceived Exertion (category range, 0-10) was evaluated using male and female children (6-13 yr of age) during a treadmill graded exercise test. METHODS: A cross-sectional, perceptual estimation paradigm using a walking/running test protocol was administered. Oxygen uptake (VO(2), mL x min(-1)), %VO(2max), ventilation (VE, L x min(-1)), respiratory rate (RR, breaths x min(-1)), respiratory exchange ratio (RER), heart rate (HR, beats x min(-1)), V(E)/VO(2) ratio, and ratings of perceived exertion (RPE) measurements were made every minute throughout the test. RESULTS: Significant correlations were found between OMNI-walk/run Scale RPE responses and VO(2), %VO(2max), HR, V(E)/VO(2) ratio, and RR throughout the maximal treadmill exercise test. The strongest correlations were found between RPE and %VO(2max) (r = 0.41-0.60, P < 0.001) and HR (r = 0.26-0.52, P < 0.01). CONCLUSION: The psychophysiological responses provide validity evidence for use of the Children's OMNI-walk/run Scale over a wide range of exercise intensities during both walking and running.     

A comparison of methods used to determine VO2 of exercising humans and animals

The purpose of these experiments was to compare two systems for measuring oxygen uptake (VO2): the open circuit method of indirect calorimetry (Rv), which is commonly used in human studies, and the open flow method, which has been adopted in a variety of animal studies. VO2 measured using the Rv system (procedure 1) was accepted as the criterion value. Two procedures were used to calculate VO2 in the open flow system: MCO2 (where O2 and CO2 were measured in mixed expired gas) and MO2 (O2 measured only). VO2 was measured in ten human subjects during three continuous incremental cycling tests to peak power output administered on three separate occasions--once using each of the three procedures. The results indicated a relatively small difference in VO2 between the Rv and MCO2 procedures (6.2 +/- 4.5%) and between the Rv and MO2 procedures (3.7 +/- 1.7%), across a broad range of power outputs (40-100% VO2 peak). The difference between the Rv and MCO2 procedures decreased as power output increased, while that between the Rv and MO2 procedures remained relatively constant. Therefore, the open flow method is shown to be a valid and reproducible technique for assessment of the metabolic activity of humans and animals.     

Heart rate recovery from submaximal exercise in boys and girls

PURPOSE: To examine the changes in heart rate (HR) after two different submaximal exercise bouts in boys and girls. METHODS: Eleven boys (10.5 +/- 1.0 yr) and 10 girls (10.8 +/- 0.7 yr) participated in this study. Each child completed an initial graded exercise test to determine peak VO2. On subsequent and separate days, a 5-min submaximal exercise bout on a cycle ergometer was performed. One bout was conducted at 70 W, and the other bout corresponded to an intensity of 85-90% of peak VO2. VO2 and HR were measured during and after (1 min and 3 min). HR recovery responses from each submaximal exercise bout were analyzed using a group by time ANOVA, and Pearson-product correlations were determined between resting HR, peak VO2, and postexercise HR responses. RESULTS: HR in the boys was lower at the end of exercise and the first minute of recovery versus girls but not at the 3rd min of recovery. There were no differences in HR recovery after the relative exercise bout. Resting HR was significantly correlated with postexercise HR from both bouts (r = 0.52-0.69), whereas peak VO2 did not correlate to postexercise HR. ANCOVA using resting HR as the covariate eliminated the gender different noted with the recovery from the 70-W bout. CONCLUSIONS: In summary, postexercise HR responses differed between boys and girls when submaximal exercise was performed at an absolute work rate. When exercise was performed at a relative intensity, HR recovery responses were similar between the two groups. Resting HR appears to account for variations in postexercise HR better than peak VO2.     

Comparison of incremental treadmill exercise and free range running

PURPOSE: The aim of this study was to compare physiological responses during incremental treadmill exercise and free range running. METHODS: Fifteen competitive cross-country runners performed an incremental treadmill test and an unpaced 1-mile run on an indoor 200-m track. Physiological variables (VO(2peak), HR(peak), VO(2) x HR(-1)(peak), V(Epeak)) were measured using a portable metabolic analyzer. Blood lactate was measured post exercise. Outcome variables were analyzed with repeated measures ANOVA. RESULTS: Although directionally similar to previous studies with cycle ergometry, the observed peak values (track vs treadmill) for VO(2) (63.0 +/- 7.4 vs 61.9 +/- 7.2 mL x kg(-1) x min(-1)), V(E) (147 +/- 37 vs 144 +/- 30 L x min(-1)), HR (188 +/- 5 vs 189 +/- 7 beats.min-1), and VO(2) x HR(-1) (22.1 +/- 4.4 vs 21.5 +/- 4.5) were not significantly different. The observed peak values for blood lactate (14.4 +/- 3.3 vs 11.7 +/- 3.0 mmol x L(-1)) were significantly (P < 0.05) different. CONCLUSIONS: The results are not in full agreement with previous findings from cycling studies with the exception of post exercise blood lactate. Whether this represents a fundamental lack of effect of free range exercise or is related to mode specificity remains to be determined.     

The effects of oral smokeless tobacco on the cardiorespiratory response to exercise.

The purpose of this investigation was to determine the effects of oral smokeless tobacco (OST) usage on oxygen uptake (VO2), cardiac output (Qc), stroke volume (SV), heart rate (HR), and plasma lactate concentration (Lc) during rest and exercise. Fifteen asymptomatic subjects were recruited from 18 to 33-yr-old male users of OST. Comparisons of the responses of VO2, Qc, SV, HR, and Lc were made between 2.5-g OST and placebo experimental conditions during rest and at 60% and 85% maximal VO2 treadmill exercise. Plasma nicotine concentrations (Nc) were determined by radioimmunoassay. There were significant increases in HR and Lc and a decrease in SV during rest and at 60% and 85% maximal exercise (P less than 0.05). Furthermore, there were no significant differences in maximal HR, Lc, and VO2 (P greater than 0.05). In conclusion, these data indicate that the increased Nc incurred by OST usage increases anaerobic energy production and produces an increased tachycardiac response to a given relative submaximal workload.     

Heart rate variability after isocaloric exercise bouts of different intensities

PURPOSE: To examine cardiac autonomic modulation, via heart rate variability (HRV), after exercise bouts at 50% (LO) and 80% (HI) of VO2 reserve (VO2R). METHODS: Thirteen male volunteers (age: 25.7+/-3 yr) exercised on a treadmill at either LO or HI (randomly assigned) on separate days, expending 300 kcal during each bout. During each visit, electrocardiogram (ECG) recordings were obtained during a supine 5-min period before exercise (PRE) and during 30 min of postexercise supine recovery (POST). The last 25 min of POST was divided into five 5-min segments to closely examine postexercise HRV. ECG segments were analyzed for the standard deviation of RR intervals (SDNN), whereas total- (lnTP), low- (lnLF), and high-frequency (lnHF) power were obtained via spectral analysis. LF and HF were further normalized (LFNU and HFNU) to better quantify autonomic balance. RESULTS: There were main effects of time and intensity on SDNN such that it was lower than PRE until 15 min POST, and lower after HI. There were significant intensity x time interactions on lnTP, lnLF, lnHF, LFNU, HFNU, and lnLF/lnHF. Post hoc analysis revealed that lnTP and lnLF were lower than PRE up to 20 min POST after HI. lnHF was lower than PRE for 25 min POST for HI, and for 10 min POST for LO. LFNU and lnLF/lnHF were greater, whereas HFNU was lower, compared with PRE up to 15 min POST, and from 20-25 min POST for HI only. CONCLUSION: Exercise at 50% VO2R caused less of a shift in the cardiac autonomic balance, with a quicker restoration of vagal modulation than exercise at 80% VO2R.     

Lower body negative pressure treadmill exercise is more comfortable and produces similar physiological responses as weighted vest exercise

Lower body negative pressure (LBNP) treadmill exercise can generate a hypergravity load on the lower body that may improve athlete performance by mechanical and cardiovascular adaptations. This study compared the cardiovascular responses, subjective exertion and discomfort levels produced by LBNP exercise with those generated by a weighted vest (WV). We hypothesized that LBNP exercise is more comfortable than WV exercise at comparable levels of exercise. Nine subjects exercised on a treadmill at nine conditions, at 5.5 mph for 15 minutes, in which they ran in random order to avoid confounding effects: 100 %, 110 %, 120 %, 130 %, and 140 % body weight (BW), the latter four conditions were achieved by either LBNP chamber or WV. Heart rate (HR) and oxygen consumption (.VO(2)) were monitored continuously using ECG and open circuit spirometry. At the end of each test, subjects were asked to give discomfort and exertion scores using a ten-point visual analog scale (10 = maximal discomfort and exertion). For both HR and .VO(2), no significant differences were observed between LBNP and WV. Subjects reported significantly higher discomfort levels when exercising with the WV than with the LBNP at 120 % BW (5.1 +/- 0.55 vs. 3.1 +/- 0.64; p < 0.05), 130 % BW (6.2 +/- 0.42 vs. 2.3 +/- 0.44; p < 0.01) and 140 % BW (6.9 +/- 0.27 vs. 4.7 +/- 0.60; p < 0.01), while maintaining similar exertions at all conditions. Based on these results, LBNP exercise is more comfortable than standard WV exercise, while maintaining similar exertion, HR and .VO(2) values.     

Effects of a proposed challenge on effort sense and cardiorespiratory responses during exercise.

PURPOSE: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency. METHODS: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min. RESULTS: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change. CONCLUSION: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.     

Cardio-respiratory responses to rowing ergometry and treadmill exercise soon after myocardial infarction

PURPOSE: The aim of this study was to compare the cardio-respiratory differences between rowing ergometry and treadmill exercise in beta-blocked men participating in exercise rehabilitation soon after myocardial infarction (postMI). METHODS: Eleven males all receiving beta-blockade medication were measured for oxygen consumption (VO2), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) at individualized submaximal exercise target heart rates (THR) during 6 min of exercise on each of a motorized treadmill and a rowing ergometer 2-6 wk (4.9 +/- 1.4) postMI. RESULTS: The mean THR of the group, predetermined from an exercise ECG stress test, was 107 +/- 16 beats x min(-1). No significant difference was found between rowing versus treadmill VO2 (19.4 +/- 3.2 vs 19.7 +/- 4.2 mL x kg(-1) x min(-1); P = 0.53) or RPE (12.6 +/- 1 vs 12.7 +/- 1; P = 0.72). RER was significantly greater (P = 0.02) during rowing (0.99 +/- 0.07) compared with treadmill exercise (0.94 +/- 0.07). CONCLUSION: Exercising at a specified submaximal THR during rowing versus treadmill exercise in beta-blocked men participating in very early cardiac rehabilitation represents the same VO2 and RPE. A significantly greater RER was, however, apparent during rowing compared with treadmill exercise; thus, agreement was shown with previous studies on healthy individuals where rowing ergometry was less metabolically efficient than treadmill exercise. The results suggest that establishing a THR from a standard treadmill stress test soon after MI is not only suitable for walking/treadmill exercise but also in setting exercise intensity for rowing ergometry.     

Effect of hypervolemia on heart rate during 4 days of prolonged exercises

The aim was to evaluate the cardiodynamic adjustment during 4 days of prolonged exercises and to check if the plasma volume (PV) expansion which is observed generally during such events plays a role in this adaptation. Thirteen subjects exercised 5 hours per day on a cycle ergometer alternately with a treadmill for 4 days (D1 to D4) (6 x 50 min sessions per day). The individual cycle ergometer load and the treadmill speed were unchanged during each exercise session and throughout all the sessions, and corresponded to a moderate exercise intensity: 58 - 63 % of peak oxygen uptake (VO (2)peak). Heart rate (HR) was recorded every 15 s during each exercise session and VO (2) was measured from the expired air at the beginning and the end of each exercise session. Relative PV changes were measured from haematocrit and haemoglobin changes in the morning before the exercise bouts. No significant changes of VO (2) were observed between the first and the last exercise session i. e. for cycling: 2.1 +/- 0.2 l/min and for running: 2.4 +/- 0.3 l/min. Between the first and the last day, HR decreased from 143 to 129 bpm for cycle (p < 0.0001) and from 147 to 137 bpm (p = 0.01) for treadmill. As compared to D1, PV increased gradually from D2 (+ 1.8 % +/- 4.7 %) to D4 (+ 8.5 % +/- 4.7 %). The individual PV increases were significantly correlated with cycling HR decreases from D1 to D4 (r (2) = 0.40, p = 0.02). In conclusion, the 4 days' prolonged exercise induced a HR decrease during submaximal exercise without VO (2) drift. Here we suggested that this HR decline could be in part linked to the transient PV expansion.     

A comparison of the perceived and the ECG measured heart rate during cycle ergometer, treadmill and stairmill exercise before and after perceived heart rate training.

The ability to perceive exercise heart rate before and after training was tested in six young male university students, perceptions of heart rate being compared with ECG monitored heart rates during cycle ergometry, treadmill running and stairmill climbing. Between initial and final tests, subjects undertook 13 weeks of running training (2 h/day, 3-4 days/week), and during this period they compared their perceptions of heart rate with values observed on watch-type wrist-mounted pulse monitors. Individual initial perceptions showed only a moderate correlation with ECG values. This correspondence was improved as perceptions were compared with measured heart rates over the course of training, significantly so for the mode of exercise most similar to that adopted in the training sessions (treadmill running at a heart rate of 140 beats/min). The final accuracy of perceptions at a heart rate of 140 beats/min (error 8-9 beats/min during treadmill running) compared favourably with the accuracy of either pulse counting or the traditional rating of perceived exertion as commonly observed in the exercising public. This suggests that there may be an application for perceived heart rates in regulating the intensity of prescribed exercise.     

Cardiac and metabolic demands of in place shallow water running in trained and untrained men

AIM: The aim of this study was to assess maximal cardiac and metabolic demand imposed by in place shallow water running (SWR) and to compare such responses with those obtained during treadmill running (TMR). METHODS: Twelve males, 6 trained (T) pentathletes (age: 19+/-1 years) and 6 untrained (UT) controls (age: 22+/-1 years), performed one maximal TMR test and one SWR maximal test. Heart rate (HR) and oxygen consumption (VO(2)) were continuously measured in both test conditions. RESULTS: In both groups, resting HR decreased immediately after water immersion (UT group: from 81.8+/-6.2 b x min(-1) to 69.2+/-6 b min(-1); T group: from 71.7+/-2.1 b x min(-1) to 61.7+/-7.7 b x min(-1)). In UT subjects SWR metabolic demand was comparable to that obtained during treadmill (VO(2tmr)=47.9 ml min(-1)+/-3.6; VO(2tmr)=45.2 ml x min(-1) +/- 6.8). In contrast, during shallow SWR, T subjects obtained lower V.O(2max) values with respect to TMR (V.O(2tmr)=68.9 mL x min(-1) +/-5.1; VO(2TMR)=57.2 mL x min(-1)+/-3.9; P<0.05). In the T group maximal HR was lower during SWR (from 191+/-8.1 to 177+/-7.1). At a given stride frequency, SWR was less demanding than treadmill in terms of V.O(2) and HR responses. During SWR the metabolic adjustments were depressed more than the cardiac adjustments. CONCLUSION: These findings suggest that in place SWR may be a useful exercise to reduce the effects of detraining.     

Effects of Panax ginseng extract on exercise-induced oxidative stress

AIM: This study was designed to study the effects of Panax ginseng extract (PGE) on lipid peroxidation and scavenger enzymes induced by an acute exhaustive exercise in sedentary humans. METHODS: Seven healthy male subjects performed 2 exhaustive incremental exercises on the treadmill before and after 8 weeks' PGE ingestion (2 g each time, 3 times a day) as the control and PGE exercise, respectively. VO2, HR, and exercise duration during exercise were measured. Blood samples were collected at rest, and immediately, 10 and 30 min after each test and used to measure malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD). RESULTS: PGE administration significantly increased exercise duration until exhaustion by 1.5 min (p<0.05). MDA was significantly elevated following both trials (p<0.01), however, it was attenuated after PGE administration (p<0.01). CAT and SOD activities following exercise were significantly elevated, but the activities following control exercise were much lower than those following PGE exercise. CONCLUSIONS: These results suggest that the elevation in CAT and SOD activities as scavenger enzymes after PGE administration result in decrease of MDA level as one of PGE action mechanisms and consequently, prolong exercise duration until exhaustion. These findings support scientific claims that ginseng has ergogenic properties in facilitating recovery from exhaustive exercise.     

Effects of acute exercise on plasma erythropoietin levels in trained runners

PURPOSE: The purpose of this study was to investigate further the influence of exercise on erythropoietin. METHODS: We observed the effects of high intensity running on plasma erythropoietin concentration in competitive distance runners. A repeated measures design was used to compare the responses of intermittent high intensity (HIGH) exercise to continuous moderate intensity (MOD) exercise and rest (REST). The HIGH treatment consisted of 60 min of exercise alternating 5 min of running at approximately 90% of VO2max with 5 min of brisk walking. The MOD treatment consisted of a continuous 60-min run on the treadmill at 60% of VO2max. Blood samples were collected immediately before the exercise (PRE), immediately following the exercise (POST), and 4 (heart rate (4HR), 12 (12HR), 24 (24HR), and 48 (48HR)) h following the exercise. The variables examined included plasma erythropoietin concentration ([EPO]), hemoglobin (Hb) concentration ([Hb]), hematocrit (Hct), red blood cell count (RBC), and mean corpuscular volume (MCV). RESULTS: ANOVA revealed the expected treatment-by-time interaction for Hct and [Hb] suggesting a hemodilution at 24 and 48 h postexercise for the MOD and HIGH treatments. However, no significant treatment-by-time interactions were observed for [EPO], RBC, or MCV. CONCLUSION: These results indicate that intermittent high intensity exercise does not have a significant effect on [EPO] in trained distance runners.