Effects of phosphatidylserine on oxidative stress following intermittent running

PURPOSE: The aim of the study was to investigate the effects of 750 mg of soybean-derived phosphatidylserine or a glucose polymer placebo, administered daily for 10 d, on markers of oxidative stress, perceived soreness, and muscle damage initiated by intermittent exercise (designed to simulated soccer match play) immediately followed by an exhaustive run. METHODS: Following familiarization, 16 male soccer players completed an exhaustive intermittent exercise protocol on two further occasions (T1 and T2) separated by approximately 14 d. Ten days before T2, the subjects were assigned, in a double-blind manner, to receive either phosphatidylserine (PS) or a placebo (P). Exercise time to exhaustion, sprint performance, ratings of perceived exertion, and HR were recorded throughout both main exercise trials. Venous blood samples were obtained at rest (preexercise), 15 min following exercise (postexercise), 24 h after exercise (post-24 h), and 48 h after exercise (post-48 h). RESULTS: Preexercise and postexercise concentrations of plasma gamma-tocopherol were increased following supplementation in PS, although supplementation had no effect on plasma concentrations of other nonenzymatic antioxidants (vitamin C, alpha-tocopherol, retinol, and beta-carotene). Serum cortisol concentrations, perceived soreness, markers of muscle damage (creatine kinase (CK) and myoglobin (Mb)), and lipid peroxidation (hydroperoxides and conjugated diene lag times) were elevated to an equal extent in PS and P following exhaustive exercise before and following supplementation. The changes in running times to exhaustion from T1 to T2 in PS and P were 4.2 +/- 0.7 and -3.7 +/- 4.2%, respectively (P = 0.084). CONCLUSION: Supplementation with phosphatidylserine was not effective in attenuating the cortisol response, perceived soreness, and markers of muscle damage and lipid peroxidation following exhaustive running; however, supplementation tended to increase running time to exhaustion. Therefore, future research should be undertaken to investigate the potential ergogenic properties of this supplement.     

Effect of vitamin C supplementation on lipid peroxidation, muscle damage and inflammation after 30-min exercise at 75% VO2max

AIM: Hypothetically, supplementation with the antioxidant vitamins C could alleviate exercise-induced lipid peroxidation. The purpose of this study was to evaluate the effect of vitamin C supplementation on exercise-induced lipid peroxidation, muscle damage and inflammation. METHODS: Sixteen healthy untrained male volunteers participated in a 30-min exercise at 75% Vo2max. Subjects were randomly assigned to one of two groups: 1) placebo and 2) vitamin C (VC: 1 000 mg vitamin C). Blood samples were obtained prior to supplementation (baseline), 2 h after supplementation (immediately pre-exercise), post-exercise, 2 and 24 h after exercise. Plasma levels of VC, total antioxidant capacity (TAC), creatine kinase (CK), malondealdehyde (MDA), total leukocytes, neutrophils, lymphocytes, interleukin-6 (IL-6) and cortisol were measured. RESULTS: Plasma vitamin C concentrations increased significantly in the VC in response to supplementation and exercise (P<0.05). TAC decreased significantly in Placebo group 24 h after exercise compared to pre-exercise (P<0.05). Although MDA levels were similar between groups at baseline, it increased significantly 2 h after exercise only in the Placebo group (P<0.05). CK increased immediately and 2 h after exercise in both groups and 24 h after exercise only in placebo group compared to pre-exercise (P<0.05). Markers of inflammation (total leukocyte counts, neutrophil counts and IL-6) were increased significantly in response to the exercise (P<0.05). In VC group, there was significant increase in lymphocyte counts immediately after exercise compared with pre-exercise (P<0.05). Serum cortisol concentrations significantly declined after supplementation compared with baseline (P<0.05) as well as declined 2 and 24 h after exercise compared with immediately after exercise in VC group (P<0.05). CONCLUSION: VC supplementation prevented endurance exercise-induced lipid peroxidation and muscle damage but had no effect on inflammatory markers.     

Phosphatidylserine supplementation and recovery following downhill running

PURPOSE: This study investigated the effects of 750 mg of soybean-derived phosphatidylserine (S-PtdSer), administered daily for 7 d prior to a bout of eccentric exercise and for 2d following exercise, on delayed onset of muscle soreness and markers of muscle damage, inflammation, and oxidative stress that followed prolonged downhill running. METHODS: Following preliminary testing and a familiarization session, eight recreationally active males repeated an individualized downhill run at -16.5% for 51.0 +/- 1.5 min at 8.7 +/- 0.3 km x h(-1) on four occasions (trials 1-4). Trials 1 and 37 were presupplementation control trials. After trials 1 and 3 the subjects received, in a double-blind and crossover fashion, either S-PtdSer or a glucose polymer placebo. Trials 2 and 3 were separated by a 4-wk washout period. Venous blood, perceived soreness ratings, and feeling states were assessed prior to exercise, after exercise, and at 24 and 48 h after exercise during each trial. RESULTS: Downhill running led to elevations in perceived soreness (P < 0.05), creatine kinase activities (P < 0.001), myoglobin concentrations (P < 0.001), interleukin-6 (IL-6) concentrations (P < 0.001), and lipid hydroperoxide concentrations (P < 0.01). However, supplementation did not significantly attenuate these responses. CONCLUSION: These results suggest that supplementation with 750 mg x d(-1) S-PtdSer for 10 d does not afford additional protection against delayed onset of muscle soreness and markers of muscle damage, inflammation, and oxidative stress that follow prolonged downhill running.     

Effect of Vitamin C and E supplementation on biochemical and ultrastructural indices of muscle damage after a 21 km run.

This study investigated whether 4 weeks of daily supplementation with 500 or 1000 mg of Vitamin C and 500 or 1000 IU of Vitamin E could modify biochemical and ultrastructural indices of muscle damage following a 21 km run. Fifteen experienced male distance runners were divided into two groups (vitamin or placebo) and received supplementation for four weeks before completing the first 21 km run in as fast a time as possible. A four-week "washout" period followed before the subjects crossed over and received the alternate supplement for the next four weeks. They then completed a second 21 km run. Before, immediately after and 24 h after each run venous blood samples were taken and analysed for serum creatine kinase, myoglobin, malondialdehyde and vitamin C and E (before-samples only) concentrations. A subgroup of six subjects also had muscle biopsy (gastrocnemius) samples taken 24 h before and 24 h after each 21 km run, which were later analysed by electron microscopy. The two dosages of supplementation produced similar results, so a single vitamin group was formed for further analysis of results. Significant increases (p < 0.05) in creatine kinase and myoglobin, but not in malondialdehyde, were found post-run in both groups. However, no significant differences were found between the vitamin and placebo groups for creatine kinase, myoglobin and malondialdehyde concentrations recorded after the 21 km runs. A qualitative ultrastructural examination of pre-run muscle samples revealed changes consistent with endurance training, but little further change was seen after the 21 km run in either the vitamin or placebo groups. It was concluded that vitamin C and E supplementation (500 or 1000 mg or IU per day) for four weeks does not reduce either biochemical or ultrastructural indices of muscle damage in experienced runners after a half marathon.     

Influence of tart cherry juice on indices of recovery following marathon running

This investigation determined the efficacy of a tart cherry juice in aiding recovery and reducing muscle damage, inflammation and oxidative stress. Twenty recreational Marathon runners assigned to either consumed cherry juice or placebo for 5 days before, the day of and for 48 h following a Marathon run. Markers of muscle damage (creatine kinase, lactate dehydrogenase, muscle soreness and isometric strength), inflammation [interleukin‐6 (IL‐6), C‐reactive protein (CRP) and uric acid], total antioxidant status (TAS) and oxidative stress [thiobarbituric acid reactive species (TBARS) and protein carbonyls] were examined before and following the race. Isometric strength recovered significantly faster (P=0.024) in the cherry juice group. No other damage indices were significantly different. Inflammation was reduced in the cherry juice group (IL‐6, P<0.001; CRP, P<0.01; uric acid, P<0.05). TAS was ～10% greater in the cherry juice than the placebo group for all post‐supplementation measures (P<0.05). Protein carbonyls was not different; however, TBARS was lower in the cherry juice than the placebo at 48 h (P<0.05). The cherry juice appears to provide a viable means to aid recovery following strenuous exercise by increasing total antioxidative capacity, reducing inflammation, lipid peroxidation and so aiding in the recovery of muscle function.     

Effects of ibuprofen on exercise-induced muscle soreness and indices of muscle damage.

Thirty-two volunteers participated in a two-period crossover study in which ibuprofen was tested against an identical placebo for its effectiveness in reducing muscle soreness and damage after two bouts of downhill running. Subjective soreness, quadriceps isometric strength and isometric endurance time at 50 percent of maximum strength, serum activities of creatine kinase, lactate dehydrogenase and aspartate transaminase and serum levels of creatinine and urea were recorded at intervals up to 72 hours after exercise. Each downhill run produced muscle soreness, and a decline in muscle strength and 50 percent endurance time, although these parameters were unaffected by ibuprofen treatment. All serum parameters measured increased after both runs, but for the three enzymes this increase was smaller after the second run. Serum creatine kinase and urea levels were higher in the ibuprofen group after both runs. These results indicate that ibuprofen is not an appropriate treatment for delayed onset muscle soreness and damage.     

Effects of a non-steroidal anti-inflammatory drug on delayed onset muscle soreness and indices of damage.

Twenty untrained male volunteers were required to run downhill for 45 minutes on a motor driven treadmill to induce muscle soreness. The volunteers took diclofenac or placebo before and for 72 hours after two runs 10 weeks apart, in a randomised double blind crossover design. Subjective soreness was assessed before and at intervals up to 72 hours after each run; venous blood samples, collected at the same time intervals, were used to estimate serum activities of creatine kinase, lactate dehydrogenase and aspartate aminotransferase and serum concentrations of creatinine and urea. Subjective soreness and the biochemical parameters increased after both runs, although the serum enzyme response to the second run was reduced. Diclofenac had no influence on the serum biochemical response to downhill running. Although overall soreness was not affected by diclofenac, individual soreness measurements were reduced by diclofenac at the first period of the study. These results suggest that diclofenac does not influence muscle damage, but may slightly reduce the associated soreness.     

Acute alcohol consumption aggravates the decline in muscle performance following strenuous eccentric exercise

This study investigated the effects of acute moderate alcohol intake on muscular performance during recovery from eccentric exercise-induced muscle damage. Eleven healthy males performed 300 maximal eccentric contractions of the quadriceps muscles of one leg on an isokinetic dynamometer. They then consumed a beverage containing 1 g/kg bodyweight ethanol (as vodka and orange juice) (ALC). On another occasion they performed an equivalent bout of eccentric exercise on the contralateral leg after which they consumed an isocaloric quantity of orange juice (OJ). Measurement of maximal isokinetic (concentric and eccentric) and isometric torque produced across the knee, plasma creatine kinase (CK) concentrations and muscle soreness were made before and at 36 and 60 h following each exercise bout. All measures of muscle performance were significantly reduced at 36 and 60 h post-exercise compared to pre-exercise measures (all p < 0.05). The greatest decreases in peak strength were observed at 36 h with losses of 12%, 28% and 19% occurring for OJ isometric, concentric, and eccentric contractions, respectively. However, peak strength loss was significantly greater in ALC with the same performance measures decreasing by 34%, 40% and 34%, respectively. Post-exercise plasma creatine kinase activity and ratings of muscle soreness were not different between conditions (both p > 0.05). These results indicate that consumption of even moderate amounts of alcohol following eccentric-based exercise magnifies the normally observed losses in dynamic and static strength. Therefore, to minimise exercise related losses in muscle function and expedite recovery, participants in sports involving eccentric muscle work should avoid alcohol-containing beverages in the post-event period.     

Contraction-induced muscle damage is unaffected by vitamin E supplementation

PURPOSE: Vitamin E supplementation may confer a protective effect against eccentrically biased exercise-induced muscle damage through stabilization of the cell membrane and possibly via inhibition of free radical formation. Evidence supporting a protective role of vitamin E after contraction-induced muscle injury in humans is, however, inconsistent. The present study sought to determine the effect of vitamin E supplementation on indices of exercise-induced muscle damage and the postexercise inflammatory response after performance of repeated eccentric muscle contractions. METHODS: Young healthy men performed a bout of 240 maximal isokinetic eccentric muscle contractions (0.52 rad.s-1) after being supplemented for 30 d with either vitamin E (N = 9; 1200 IU.d-1) or placebo (N = 7; safflower oil). RESULTS: Measurements of torque (isometric and concentric) decreased (P < 0.05) below preexercise values immediately post- and at 48 h post-exercise. Biopsies taken 24 h postexercise showed a significant increase in the amount of extensive Z-band disruption (P < 0.01); however, neither the torque deficit nor the extent of Z-band disruption were affected by vitamin E. Exercise resulted in increased macrophage cell infiltration (P = 0.05) into muscle, which was also unaffected by vitamin E. Serum CK also increased as a result of the exercise (P < 0.05) with no effect of vitamin E. CONCLUSION: We conclude that vitamin E supplementation (30 d at 1200 IU.d-1), which resulted in a 2.8-fold higher serum vitamin E concentration (P < 0.01), had no affect on indices of contraction-induced muscle damage nor inflammation (macrophage infiltration) as a result of eccentrically biased muscle contractions.     

Combined antioxidant treatment effects on blood oxidative stress after eccentric exercise

PURPOSE: This study was designed to ascertain the effects of a combination antioxidant therapy on plasma protein carbonyls (PC), malondialdehyde (MDA), and whole blood total (TGSH), oxidized (GSSG), and reduced (GSH) glutathione in non-resistance trained females after eccentric resistance exercise. METHODS: Eighteen women (aged 19-31 yr) were randomized in a double-blind manner to either an antioxidant supplement (N = 9; 400 IU vitamin E, 1 g vitamin C, and 90 mug selenium per day) or a lactose placebo (N = 9) for 14 d before and for 2 d after eccentric elbow flexor exercise. Blood samples taken before and immediately, 2, 6, 24, and 48 h postexercise were analyzed for PC, MDA, TGSH, and GSSG. RESULTS: No treatment by time interaction was noted for any variable, with all blood markers experiencing a change after the exercise in both conditions. Time main effects were observed for PC, MDA, and GSSG, with values elevated above preexercise after the eccentric exercise, whereas GSH concentration decreased after the eccentric exercise. Antioxidant supplementation resulted in a condition main effect for PC and MDA, with lower values compared with placebo. The antioxidant treatment attenuated the rise in both PC (75%) and MDA (100%). CONCLUSION: These data suggest that eccentric resistance exercise can increase blood biomarkers of oxidative stress in non-resistance trained females, and this vitamin E, C, and selenium supplementation can attenuate the rise in PC and MDA.     

Human hamstring muscles adapt to eccentric exercise by changing optimum length

PURPOSE: It is now established that unaccustomed eccentric exercise leads to muscle fiber damage and to delayed-onset muscle soreness (DOMS) in the days after exercise. However, a second bout of eccentric exercise, a week after the first, produces much less damage and soreness. The purpose of this study was to provide evidence from muscle mechanical properties of a proposed mechanism for this training effect in human hamstring muscles. METHODS: The eccentric exercise involved 12 sets of 6 repetition "hamstring lowers," performed on specially designed equipment. Hamstring angle-torque curves were constructed for each of 10 subjects (8 male and 2 female) while they performed maximum voluntary knee extension and flexion movements on an isokinetic dynamometer. Testing sessions were performed over the week before eccentric exercise, immediately post exercise, and daily, up to 8 d post exercise. Subject soreness ratings and leg girth measurements were also made post exercise. Six subjects performed a second bout of eccentric exercise, 8 d after the first, and measurements were continued up to 10 d beyond that. RESULTS: There was a significant shift in the optimum angle for torque generation (Lo), to longer muscle lengths immediately post exercise (7.7 degrees +/- 2.1 degrees, P < 0.01), indicating an increase in series compliance within some muscle fibers. Subsequent measurements showed increases in leg girth and some muscle soreness, suggesting muscle damage. The shift in Lo persisted, even after other injury parameters had returned to normal, consistent with a training effect. Subjects also showed fewer signs of muscle damage after the second exercise bout. CONCLUSION: This is the first study to show a sustained shift in optimum angle of human muscle as a protective strategy against injury from eccentric exercise. Implications of this work for athletes, particularly those prone to hamstring strains are discussed.     

A single session of resistance exercise induces oxidative damage in untrained men

PURPOSE: During exercise, the production of reactive oxygen and nitrogen species significantly increases. The aim of the present study was to investigate the effects of a single session of resistance exercise on antioxidant capacity, oxidative damage, and inflammation. METHODS: Muscle biopsies, urine, and blood samples were collected from seven healthy men before and after a single bout of resistance exercise. RESULTS: A single session of resistance exercise was found to induce oxidative damage, as shown by a 40% increase in the concentration of urinary F2alpha-isoprostanes (P < 0.05). Total antioxidant capacity of plasma increased 16% (P < 0.05). This increase seemed to be predominantly attributable to an increase in plasma uric acid concentrations of 53% (P < 0.05). Similar to uric acid, but to a relatively much smaller extent, vitamin C and vitamin E levels in plasma were also elevated (P < 0.05). Moreover, the erythrocyte glutathione (GSH) [corrected] concentration increased 47% during exercise (P < 0.05). Also in skeletal muscle, uric acid levels were found to increase after exercise (P < 0.05). Moreover, 30 min after exercise, skeletal muscle glutathione S-transferase (GST) and glutathione reductase activity increased 28 and 42%, respectively (P < 0.05). Skeletal muscle reduced GSH [corrected] and GSH [corrected] disulphide (GSSG) concentrations were not affected by exercise. The Nuclear Factor kappa B (NF-kappaB) activity in peripheral blood mononuclear cells (PBMC) was not increased by exercise, indicating that a NF-kappaB-mediated inflammatory response does not occur. CONCLUSION: We conclude that a single session of resistance exercise induces oxidative damage despite an adaptive increase in antioxidant capacity of blood and skeletal muscle.     

Oxidative stress response to aerobic exercise: comparison of antioxidant supplements

PURPOSE: To compare the effects of two antioxidant formulas on biomarkers of oxidative stress before and after aerobic exercise. METHODS: Aerobically trained men (N=25) and women (N=23) were assigned to one of three treatments: 400 IU of vitamin E+1 g of vitamin C (V; N=15), a fruit and vegetable juice powder concentrate (FV; N=16), or a placebo (P; N=17). Subjects ran for 30 min at 80% VO(2 max) before, after 2 wk of supplementation, and after a 1-wk washout period. Blood samples were taken before and immediately after exercise and analyzed for protein carbonyls (PC), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), and vitamins C and E. RESULTS: The V treatment increased plasma vitamin C and E after 2 wk (P 相似文献   

Branched-chain amino acid supplementation does not enhance athletic performance but affects muscle recovery and the immune system

Since the 1980's there has been high interest in branched-chain amino acids (BCAA) by sports nutrition scientists. The metabolism of BCAA is involved in some specific biochemical muscle processes and many studies have been carried out to understand whether sports performance can be enhanced by a BCAA supplementation. However, many of these researches have failed to confirm this hypothesis. Thus, in recent years investigators have changed their research target and focused on the effects of BCAA on the muscle protein matrix and the immune system. Data show that BCAA supplementation before and after exercise has beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis. Muscle damage develops delayed onset muscle soreness: a syndrome that occurs 24-48 h after intensive physical activity that can inhibit athletic performance. Other recent works indicate that BCAA supplementation recovers peripheral blood mononuclear cell proliferation in response to mitogens after a long distance intense exercise, as well as plasma glutamine concentration. The BCAA also modifies the pattern of exercise-related cytokine production, leading to a diversion of the lymphocyte immune response towards a Th1 type. According to these findings, it is possible to consider the BCAA as a useful supplement for muscle recovery and immune regulation for sports events.     

Effects of vitamin E supplementation on oxidative stress at rest and after exercise to exhaustion in athletic students

AIM: The purpose of this study is to determine the effect following exercise to exhaustion of vitamin E supplementation on oxidative stress in athletic students. METHODS: Twenty male students voluntarily participated in the study and were randomly assigned (double blind) to either a vitamin E (daily dose of 450 mg of a-tocopherol for a period of 8 weeks) or a placebo group (took capsules containing 450 mg of lactose for 8 weeks). Before and after 8 weeks blood samples were collected at rest and after exercise to exhaustion. Oxidative stress markers were malondialdehyde (MDA), carbonylated proteins (CP) and creatine kinase (CK). Also, the effect of vitamin E on ergometer cycling time, as an example of endurance performance, was evaluated. RESULTS: ANOVA and independent t-tests indicated that vitamin E supplementation did not significantly change (P > 0.05) MDA, CP and CK values at rest, after exercise to exhaustion, and cycling time, but plasma volume after exercise to exhaustion significantly decreased (P < 0.05). CONCLUSIONS: Although vitamin E supplementation had no effect on exercise performance or capacity in athletic students, further investigation is required using larger numbers of subjects and measures of vitamin E before unequivocal conclusion can be stated.     

Whey protein-containing product reduces muscle damage induced by running in male adults

Purpose

Whey protein has been reported to reduce exercise-induced muscle damage. Previous reports have focused mainly on post-exercise data, with results obtained before or during exercise being limited. This study examined the effect of consuming whey protein on muscle damage before, during (three times), and immediately after a 60-min running session.

Methods

The study was designed as a placebo-controlled, two-period cross-over trial. Fourteen male adults were enrolled in the study and completed a 60-min running session at an intensity >70 % of maximal oxygen uptake ( \(\dot {\text{V}}\text {O}_{2\text{max}}\) ). Once before, three times during, and once after this exercise the subjects consumed a serving of a test product that contained 22.8 g of whey protein as the main ingredient, or a similar placebo product made by removing only the whey protein. Blood samples were collected during the pre-exercise period to 24 h after the running session was completed.

Results

Compared to the placebo product, the test product significantly suppressed the elevation of serum creatine kinase (CK) and myoglobin after exercise (P < 0.05) and suppressed the elevation of plasma interleukin (IL)-6, but not significantly (P = 0.055). Plasma amino acid (AA) concentrations increased immediately after exercise following ingestion of the test product, and negative correlations (P < 0.05) were observed between AA and both serum CK and plasma IL-6 concentrations immediately after exercise.

Conclusions

Whey protein consumption likely plays an important role in the increase of AA concentrations in the blood, even during exercise, and was associated with a decrease in exercise-related muscle damage and inflammation.     

Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise

BACKGROUND: The aim of this study was to examine the effects of branched-chain amino acid (BCAA) supplementation on serum indicators of muscle damage after prolonged exercise. We hypothesized that BCAA supplementation would reduce the serum activities of intramuscular enzymes associated with muscle damage. METHODS: To test this hypothesis, sixteen male subjects were assigned to one of two groups: the supplemental group (consuming 12 g x d(-1) BCAA for 14 d in addition to their normal diet) or the control group (normal diet only). Baseline serum creatine kinase (CK) and lactate dehydrogenase (LDH), shown to be accurate indicators of muscle damage, were determined during the week before the exercise test. The exercise test was administered on day seven and required the subjects to cycle for 120 min on an ergometer at approximately 70% VO2max. Blood samples were taken prior to and immediately following exercise and at 1 hr, 2 hrs, 3 hrs, 4 hrs, 1 d, 3 d, 5 d and 7 d postexercise. All subjects were required have their diets analyzed daily during the 14 d. RESULTS: Dietary analyses indicated that all subjects consumed the recommended daily intake of BCAA (0.64 g x kg(-1)) in their normal diets. Baseline serum values for CK and LDH were not different between groups in the 7 d prior to the test (p>0.05). However there were significant increases (p<0.05) between the pre-exercise and postexercise values for LDH and CK until 5 d postexercise test. Importantly, the BCAA supplementation significantly reduced this change in LDH from 2hrs to 5 d posttest, and CK from 4 hrs to 5 d post-test (p<0.05). CONCLUSIONS: These results indicate that supplementary BCAA decreased serum concentrations of the intramuscular enzymes CK and LDH following prolonged exercise, even when the recommended intake of BCAA was being consumed. This observation suggests that BCAA supplementation may reduce the muscle damage associated with endurance exercise.     

Changes in markers of muscle damage of middle-aged and young men following eccentric exercise of the elbow flexors

It is well documented that unaccustomed eccentric exercise induces muscle damage, but the responses of middle-aged individuals to a bout of eccentric exercise have not been reported. The purpose of this study was to compare changes in indirect markers of muscle damage following eccentric exercise of the elbow flexors between 12 young (age: 19.4+/-0.4 years, height: 173.5+/-2.0cm, body mass: 65.8+/-3.5kg) and 12 middle-aged men (48.0+/-2.1 years, 169.5+/-1.7cm, 67.3+/-1.6kg). It was hypothesized that middle-aged men would be more susceptible to muscle damage than young men. All subjects performed six sets of five eccentric actions of the elbow flexors using a dumbbell of 40% of maximal isometric strength (MVC). Changes in MVC, elbow joint angles and range of motion, upper arm circumference, plasma creatine kinase activity and myoglobin concentration, and muscle soreness before, immediately after, and 1, 2, 3, and 4 days after exercise were compared between the young and middle-aged groups by a two-way repeated measures ANOVA. All criterion measures changed significantly (P<0.05) after exercise, but no significant differences in the changes in the measures except for muscle soreness were evident between groups. Development of muscle soreness after exercise was significantly (P<0.05) lower (approximately a half of the value) for the middle-aged group compared with the young group. These results did not support the hypothesis that middle-aged men would be more susceptible to muscle damage than young men.     

Vitamin E supplementation and endurance exercise: are there benefits?

It has been widely noted that vitamin E shows numerous beneficial effects through and beyond its antioxidative properties; consequently, vitamin E is expected to prevent degenerative diseases. In the field of sports medicine, many studies dealing with vitamin E have been conducted originally from the point of view of its effects on physical performance. Although some earlier studies indicated that vitamin E supplementation could improve physical performance, defects in the study design or statistical analysis were pointed out at a later time. The majority of subsequent well controlled studies have reported no significant effect on physical performance from vitamin E supplementation. Recent studies suggest that endurance exercise may promote free radical generation in the body, and vitamin E may play an important role in preventing the free radical damage associated with endurance exercise. Although there is evidence of free radical involvement in exercise-induced muscle injury, vitamin E supplementation might not be expected to prevent muscle damage caused by exercise in humans without a vitamin E deficiency. Since it is still unclear whether exercise induces lipid peroxidation in the human body, the beneficial effect of vitamin E supplementation on exercise-induced lipid peroxidation has not yet been established. However, it is proposed that as a result of exercise vitamin E may be mobilised from store tissues and redistributed in the body to prevent oxidative damage. Therefore, we are convinced that vitamin E contributes to preventing exercise-induced lipid peroxidation. It has also been indicated that strenuous endurance exercise may enhance the production of oxidised low density lipoprotein (LDL), which plays a key role in the initiation and progression of atherosclerosis. It is also suggested that this enhanced production of oxidised LDL could be reduced if a higher vitamin E status is maintained. Supplementation with 100 to 200mg of vitamin E daily can be recommended for all endurance athletes to prevent exercise-induced oxidative damage and to reap the full health benefits of exercise.     

Early alterations in serum creatine kinase and total cholesterol following high intensity eccentric muscle actions

AIM: The purpose of this experiment was to assess the levels of muscle soreness, serum total cholesterol (TC) and creatine kinase (CK) in the first 48 hours following fatiguing eccentric exercise performed with the triceps brachii. METHODS: Eleven untrained male college students performed a total of 50 eccentric elbow extensions in 8 sets (6 x 7 and 2 x 4) with a load equal to 85% of their maximal concentric elbow extension strength. Isometric elbow extension strength, muscle soreness and circumference, and serum CK and TC concentrations were measured before, immediately after, and 2, 24 and 48 hours after the exercise. RESULTS: Statistically reliable changes in isometric strength, serum CK and TC, muscle soreness and upper arm circumference occurred within the first 48 hours following eccentric exercise. Serum TC concentrations exhibited a very rapid (within 2 hours) reduction from pre-exercise values after eccentric exercise to a relatively stable concentration of approximately 85% of baseline. CONCLUSION: These results suggest that serum TC concentration may follow the time-course of reductions in force generating capacity more closely than other biochemical markers of muscle damage.