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.     

Relationship between post-exercise plasma CK elevation and muscle mass involved in the exercise.

The purpose of this study was to investigate whether a larger post-exercise increase in plasma creatine kinase (CK) activity would be produced when a larger amount of muscle is damaged by eccentric exercise. Twenty-two non-weight trained females were placed into two groups; Group A (n = 12) and Group B (n = 10). Both groups performed 24 maximal eccentric actions of the forearm flexors on each bout. The right and left arm were exercised on the same day for Group A (24 eccentric actions per arm, a total of 48 actions). In contrast, Group B performed 24 actions with either the right or the left arm on the first bout and performed 24 eccentric actions with the opposite arm on the second bout 3-5 weeks later. Blood samples were taken before and for 5 days after each exercise and plasma CK activity was determined. Forearm flexion isometric force (ISO), range of motion evaluated by relaxed elbow joint angle (RANG) and flexed elbow joint angle (FANG), and perceived muscle soreness (SOR) were also examined to indirectly assess muscle damage. All of the muscle damage indicators changed significantly over time (p < 0.01) for both groups, but changes were not significantly different between arms or between groups. Because it seemed that both arms were equally "damaged" for each group, it was expected that Group A (two arms were exercised on the same day) should show an approximate two-fold increase in plasma CK compared to Group B when one arm was exercised on each bout.(ABSTRACT TRUNCATED AT 250 WORDS)     

Muscle damage and soreness after endurance exercise of the elbow flexors

PURPOSE: This study investigated changes in indirect markers of muscle damage after endurance exercise of the elbow flexors and compared the changes with those after maximal eccentric actions (Max-ECC) of the elbow flexors. METHODS: Eighteen male students rhythmically lifted (1 s) and lowered (1 s) a light dumbbell (1.1-1.8 kg: 9% of MIF) in 60-180 degrees of elbow joint angle for 2 h (2-h Ex). Maximal isometric force (MIF), relaxed (RANG) and flexed elbow joint angles (FANG), upper-arm circumference (CIR), muscle soreness (SOR), B-mode ultrasound (US), and plasma creatine kinase (CK) activity were assessed before and immediately after, and up to 96 h after exercise. RESULTS: All measures were altered significantly (P < 0.05) after 2-h Ex in a similar time course to Max-ECC; however, changes in RANG, FANG, CIR, US, and CK (peak: 356 +/- 121 IU.L-1) were significantly (P < 0.05) smaller compared with those after Max-ECC. SOR developed immediately after 2-h Ex and peaked 24-48 h after exercise. MIF dropped to 44.1% of the preexercise level, which was significantly (P < 0.05) lower than that after Max-ECC (58.1%), immediately postexercise. MIF recovered to 79.8% at 24 h, and 97.8% at 96 h postexercise, which was a significantly (P < 0.05) faster recovery compared with that of Max-ECC (73.1% at 96 h). CONCLUSION: These results showed low-intensity continuous muscle contractions (3600 times) resulted in muscle damage; however, the magnitude of the muscle damage was less severe, and the recovery was faster compared with 12 maximal eccentric muscle actions.     

Differential expression of muscle damage in humans following acute fast and slow velocity eccentric exercise

We sought to determine if the velocity of an acute bout of eccentric contractions influenced the duration and severity of several common indirect markers of muscle damage. Subjects performed 36 maximal fast (FST, n = 8: 3.14 rad x s(-1)) or slow (SLW, n = 7: 0.52 rad x s(-1)) velocity isokinetic eccentric contractions with the elbow flexors of the non-dominant arm. Muscle soreness, limb girth, plasma creatine kinase (CK) activity, isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad x s(-1) were assessed prior to and for several days following the eccentric bout. Peak plasma CK activity was similar in SLW (4030 +/- 1029 U x 1(-1)) and FST (5864 +/- 2664 U x 1(-1)) groups, (p > 0.05). Both groups experienced similar decrement in all strength variables during the 48 hr following the eccentric bout. However, recovery occurred more rapidly in the FST group during eccentric (0.52 and 3.14 rad x s(-1)) and concentric (3.14 rad x s(-1)) post-testing. The severity of muscle soreness was similar in both groups. However, the FST group experienced peak muscle soreness 48 hr later than the SLW group (24 hr vs. 72 hr). The SLW group experienced a greater increase in upper arm girth than the FST group 20 min, 24 hr and 96 hr following the eccentric exercise bout. The contraction velocity of an acute bout of eccentric exercise differentially influences the magnitude and time course of several indirect markers of muscle damage.     

Activity and immobilization after eccentric exercise: I. Recovery of muscle function

PURPOSE: The purpose of the present study was to determine whether activity would affect the recovery of muscle function after high-force eccentric exercise of the elbow flexors. METHODS: Twenty-six male volunteers were randomly assigned to one of three groups for a 4-d treatment period: immobilization (N = 9), control (N = 8), and light exercise (N = 9). Relaxed arm angle (RANG), flexed arm angle (FANG), maximal isometric force (MIF), and perceived muscle soreness (SOR) were obtained for 3 consecutive days pre-exercise (baseline), immediately post-exercise, and for 8 consecutive days after the 4-d treatment period (recovery). During the treatment period, the immobilization group had their arm placed in a cast and supported in a sling at 90 degrees. The control group had no restriction of their arm activity. The light exercise group performed a daily exercise regimen of 50 biceps curls with a 5-lb dumbbell. RESULTS: All subjects showed a prolonged decrease in RANG, increase in FANG, loss in MIF, and increase in SOR in the days after eccentric exercise. During recovery, there was no significant interaction observed among groups over time in RANG (P > 0.05) or FANG (P > 0.05), but there was a significant interaction observed among groups over time in both MIF (P < 0.01) and SOR (P < 0.01). Recovery of MIF was facilitated by light exercise and immobilization, whereas recovery from SOR was facilitated by light exercise and delayed by immobilization. CONCLUSIONS: The recovery of MIF in both the light exercise and immobilization groups suggests that more than one mechanism may be involved in the recovery of isometric force after eccentric exercise.     

Muscle soreness and serum creatine kinase activity following isometric, eccentric, and concentric exercise

Serum creatine kinase (CK) activity and subjective ratings of muscle soreness were assessed in 28 college women following three different arm flexion exercise regimens. The subjects were randomly assigned to an eccentric, isometric, or concentric exercise regimen. Each regimen was equated for total work time and work-to-rest ratio. Blood samples for determination of serum CK activity and perceived soreness ratings were obtained prior to and 5, 10, and 25 h following each exercise. Significant increases in perceived soreness ratings were observed for each exercise regimen. The magnitude of the post-exercise increase in perceived soreness was greatest for the eccentric and the isometric exercises with minimal soreness following the concentric exercise. A small but significant increase in serum CK activity was observed following the three exercises (eccentric = 35.8%, concentric = 37.6%, isometric = 34.0%). The post-exercise serum CK increases did not differ significantly among the three regimens. The rise in serum CK activity suggests that muscle damage occurred during all three tasks. However, due to multiple factors which can affect serum CK levels, the increase in serum CK activity may not provide a sensitive indicator of the magnitude of the injury.     

How long does the protective effect on eccentric exercise-induced muscle damage last?

PURPOSE: One bout of eccentric exercise produces an adaptation that reduces muscle damage in subsequent bouts. Because it is not known how long this adaptation lasts, the present study investigated the maximal length of the attenuated changes in muscle damage indicators after high-force eccentric exercise. METHODS: Male students (N = 35) were placed into three groups and performed two bouts of eccentric exercise of the nondominant elbow flexors separated by either 6 (N = 14), 9 (N = 11), or 12 (N = 10) months. Maximal isometric force (MIF), range of motion (ROM), upper arm circumference (CIR), muscle soreness (SOR), and plasma creatine kinase activity (CK) were measured before and for 5 d after exercise. Magnetic resonance (MR) images of the transverse and longitudinal scans of the upper arm were taken 4 d after exercise. Changes in the criterion measures were compared between the first and second bouts and between groups by a two-way repeated measures ANOVA. RESULTS: A faster recovery in MIF was evident after a second bout performed at 6 or 9 months, and reduced SOR as well as smaller increases in CIR, CK, and T2 relaxation time of MR images also occurred after the second exercise bout at 6 months compared with initial responses. No significant differences between the bouts were found for ROM, and the 12-month group did not show any repeated bout effect. CONCLUSION: These results show that the repeated bout effect for most of the criterion measures lasts at least 6 months but is lost between 9 and 12 months.     

A light load eccentric exercise confers protection against a subsequent bout of more demanding eccentric exercise

This study investigated the hypothesis that a light eccentric exercise (ECC) that does not induce a loss of muscle function and delayed onset muscle soreness would confer a protective effect against a more strenuous ECC. Eighteen young men were randomly placed into two groups: 10–40% (n = 9) and 40% (n = 9). Subjects in the 10–40% group performed ECC of the elbow flexors (six sets of five reps) using a dumbbell set at 10% of maximal isometric strength (MVC) at an elbow joint angle of 90°, followed 2 days later by ECC using a dumbbell weight of 40% MVC. Subjects in the 40% group performed the 40% ECC only. Changes in MVC, range of motion (ROM), upper arm circumference (CIR), plasma creatine kinase (CK) activity and muscle soreness before, immediately after, 1–5 and 7 days following the 40% ECC were compared between groups by a two-way repeated measures ANOVA. No significant changes in any of the criterion measures were found immediately and 1–2 days after the 10% ECC. Following the 40% ECC, the 10–40% group showed significantly (P < 0.05) smaller decreases in MVC and ROM, and smaller increases in muscle soreness compared with the 40% group, but no significant differences between groups were evident for CIR and plasma CK activity. These results suggest that the 10% ECC induced some protection against a subsequent bout of 40% ECC performed 2 days later. It appears that the light eccentric exercise preconditioned the muscles for exposure to the subsequent damaging eccentric exercise bout.     

Plasma creatine kinase activity and glutathione after eccentric exercise

PURPOSE: This study examined whether plasma total glutathione levels could explain the intersubject variability in the creatine kinase (CK) response to eccentric exercise. We hypothesized that the increase in plasma CK activity after eccentric exercise would be lower for individuals with low plasma total glutathione (<2.5 micromol x L-1) compared with individuals with high total glutathione (>3.8 micromol x L-1), but other indicators of muscle damage would be the same between groups. METHODS: Resting blood samples were obtained over 2 d from 60 subjects and analyzed for plasma total glutathione. Eight subjects who had total glutathione values below 2.5 micromol x L-1 (LG), and nine who had values above 3.8 micromol x L-1 (HG) performed 50 maximal eccentric actions of the elbow flexors. Maximal voluntary isometric contraction (MVC), relaxed arm angle (RANG), and blood samples for CK, myoglobin (Mb), and total glutathione were obtained pre, post (except blood samples), 24, 48, 72, 96, and 120 h after exercise. RESULTS: There was a significant group-by-time interaction in analysis of MVC, RANG, total glutathione, CK, and Mb response to exercise. Although LG showed a smaller CK response to eccentric exercise compared with HG, LG also showed a smaller increase in plasma Mb, a faster recovery of MVC and RANG, and an increase in plasma total glutathione. CONCLUSION: Subjects with low plasma total glutathione levels had a smaller plasma CK and Mb response and a faster recovery from eccentric exercise compared with subjects having high plasma total glutathione levels. We suggest that a blunted inflammatory response in subjects with low plasma glutathione may be one explanation for these findings.     

Is recovery from muscle damage retarded by a subsequent bout of eccentric exercise inducing larger decreases in force?

The aim of this study was to investigate whether a subsequent bout of eccentric exercise inducing larger decreases in force than the initial bout would exacerbate muscle damage and retard recovery. Changes in indirect markers of muscle damage were measured over 14 days when 24 maximal eccentric actions of the elbow flexors were performed on days 1 (ECC1) and 7 (ECC2], with electrical stimulation superimposed percutaneously to the elbow flexors during maximal eccentric actions in ECC2. Maximal isometric force (MIF), range of motion (ROM), upper arm circumference, muscle soreness, B-mode ultrasound, and several muscle proteins in the blood were assessed before, immediately after and for 5 days after both bouts. Magnetic resonance Imaging (MRI) was assessed 4 days after both bouts. MIF decreased to 45% of the pre-exercise value immediately after ECC 1 and recovered to 59% by day 7 post-exercise. MIF decreased to 22% of pre-ECC1 value immediately after ECC2, but recovered to 105% of pre-ECC2 value 5 days following ECC2. Recovery of MIF and ROM was slightly retarded for 1-2 days after ECC2. However circumference, muscle soreness, and biochemical parameters did not increase following ECC2. There were no signs of additional damage in ultrasound and MRI after ECC2. It was concluded that a second bout of maximal eccentric exercise with electrical stimulation slightly retarded recovery of muscle function with minimal muscle damage.     

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.     

Concentric or eccentric training effect on eccentric exercise-induced muscle damage.

PURPOSE: The purpose of this study was to compare changes in muscle damage indicators following 24 maximal eccentric actions of the elbow flexors (Max-ECC) between the arms that had been previously trained either eccentrically or concentrically for 8 wk. METHODS: Fifteen subjects performed three sets of 10 repetitions of eccentric training (ECC-T) with one arm and concentric training (CON-T) with the other arm once a week for 8 wk using a dumbbell representing 50% of maximal isometric force of the elbow flexors (MIF) determined at the elbow joint of 90 degrees (1.57 rad). The dumbbell was lowered from a flexed (50 degrees, 0.87 rad) to an extended elbow position (180 degrees, 3.14 rad) in 3 s for ECC-T, and lifted from the extended to the flexed position in 3 s for CON-T. Max-ECC was performed 4 wk after CON-T and 6 wk after ECC-T. Changes in MIF, range of motion (ROM), upper arm circumference (CIR), muscle soreness (SOR), and plasma creatine kinase (CK) activity were compared between the ECC-T and CON-T arms. RESULTS: The first ECC-T session produced larger decreases in MIF and ROM, and larger increases in CIR and SOR compared with CON-T. CK increased significantly (P < 0.01) and peaked 4 d after the first training session, but did not increase in the following sessions. All measures changed significantly (P < 0.01) following Max-ECC; however, the changes were not significantly different between ECC-T and CON-T arms. CONCLUSION: These results showed that ECC-T did not mitigate the magnitude of muscle damage more than CON-T, and CON-T did not exacerbate muscle damage.     

Muscle soreness, swelling, stiffness and strength loss after intense eccentric exercise.

High-intensity eccentric contractions induce performance decrements and delayed onset muscle soreness. The purpose of this investigation was to study the magnitude and time course of such decrements and their interrelationships in 26 young women of mean(s.d.) age 21.4(3.3) years. Subjects performed 70 maximal eccentric contractions of the elbow flexors on a pulley system, specially designed for the study. The non-exercised arm acted as the control. Measures of soreness, tenderness, swelling (SW), relaxed elbow joint angle (RANG) and isometric strength (STR) were taken before exercise, immediately after exercise (AE), analysis of variance and at 24-h intervals for 11 days. There were significant (P < 0.01, analysis of variance) changes in all factors. Peak effects were observed between 24 and 96 h AE. With the exception of STR, which remained lower (P < 0.01), all variables returned to baseline levels by day 11. A non-significant correlation between pain and STR indicated that pain was not a major factor in strength loss. Also, although no pain was evident, RANG was decreased immediately AE. There was no relationship between SW, RANG and pain. The prolonged nature of these symptoms indicates that repair to damaged soft tissue is a slow process. Strength loss is considered particularly important as it continues when protective pain and tenderness have disappeared. This has implications for the therapeutic management of patients with myopathologies and those receiving eccentric exercise for rehabilitation.     

Do dominant and non-dominant arms respond similarly to maximal eccentric exercise of the elbow flexors?

ObjectivesTwo common models to investigate the effect of interventions on muscle damage include using two groups in which one group receives an intervention while the other acts as control, and using contralateral limbs of one group. The latter model is based on the assumption that changes in markers of muscle damage are similar between limbs, but this has not been examined systematically.DesignThis study compared changes in muscle damage markers between dominant and non-dominant arms following maximal eccentric exercise of the elbow flexors.MethodsEighteen men performed 60 maximal eccentric elbow flexions of each arm separated by 4 weeks with the order of testing between arms randomised. Maximal voluntary isometric torque, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and muscle soreness before and for 7 days following exercise were compared between arms using two-way repeated measures ANOVA.ResultsNo significant differences between arms were evident for any of the markers, but significant (P < 0.05) differences between first and second bouts were evident for changes in strength, circumference and CK with smaller changes following the second bout. A poor correlation was found for the magnitude of changes in the markers between dominant and non-dominant arms, suggesting that responses to eccentric exercise were not necessarily the same between arms.ConclusionsThese results show that the order affected the responses of dominant and non-dominant arms to the eccentric exercise; however, the contralateral limb design appears to be usable if bout order is counterbalanced and randomised among participants.     

Acute adaptation to low volume eccentric exercise.

PURPOSE: Many symptoms of eccentric muscle damage can be substantially reduced if a similar eccentric bout is repeated within several weeks of the initial bout. The purpose of this study was to determine whether a nondamaging, low repetition, low volume eccentric exercise bout could also provide a protective/adaptive effect. METHODS: Subjects were assigned to a control (CON), eccentric exercise (ECC), or low volume familiarized eccentric exercise group (LV+ECC). Before the study, the LV+ECC group performed six maximal eccentric contractions during two familiarization sessions. The main eccentric bout targeted the elbow flexor muscle group and consisted of 36 maximal eccentric contractions. Muscle soreness, upper arm girth, elbow angle, creatine kinase activity, isometric torque, and concentric and eccentric torque at 0.52 and 3.14 rad.s-1 were assessed 0, 1, 2, 3, 4, 7, and 10 d postexercise. RESULTS: No evidence of muscle damage was observed as a result of the low volume eccentric bouts. Nevertheless, with the exception of muscle soreness and concentric torque, all variables recovered more rapidly in the LV+ECC group (P < 0.05). CONCLUSION: Adaptation to eccentric exercise can occur in the absence of significant muscle damage. Exposure to a small number of nondamaging eccentric contractions can significantly improve recovery after a subsequent damaging eccentric bout. Furthermore, this adaptation appears to be mode-specific and not applicable to concentric contractions.     

Repeated bout effect after maximal eccentric exercise

We hypothesized that a bout of high or low volume eccentric exercise would protect against muscle damage following a subsequent high volume bout and that adaptation would be attributable to neural changes, independent of the initial exercise volume. Sixteen males performed either 45 (ECC45) or 10 (ECC10) maximal eccentric contractions using the elbow flexors, followed by an ECC45 bout 2 weeks later. Damage markers were measured for the following 96 h; EMG and work done during the first 10 eccentric contractions were also recorded. CK, soreness, and decrements in MVC and range of motion (ROM) were greater in bout 1 than bout 2 (p < 0.01). Soreness, MVC and ROM were greater after the initial ECC45 bout compared to the initial ECC10 bout and the repeated bouts of ECC45 exercise in both groups (p < 0.01). Median frequency decreased from bout 1 to bout 2 (p < 0.001), no differences between groups were observed. An ECC45 bout of maximal eccentric exercise causes more initial damage than an ECC10 bout of maximal eccentric exercise, although both confer protection from subsequent ECC45 bouts of maximal eccentric contractions, which are attributable, at least in part, to a shift in the frequency content of EMG.     

The effects of a repeated bout of eccentric exercise on indices of muscle damage and delayed onset muscle soreness

This study examined markers of muscle damage following a repeated bout of maximal isokinetic eccentric exercise performed prior to full recovery from a previous bout. Twenty non-resistance trained volunteers were randomly assigned to a control (CON, n=10) or experimental (EXP, n=10) group. Both groups performed 36 maximal isokinetic eccentric contractions of the elbow flexors of the non-dominant arm (ECC1). The EXP group repeated the same eccentric exercise bout two days later (ECC2). Total work and peak eccentric torque were recorded during each set of ECC1 and ECC2. Isometric torque, delayed onset muscle soreness (DOMS), flexed elbow angle and plasma creatine kinase (CK) activity were measured prior to and immediately following ECC1 and ECC2. at 24h intervals for 7 days following ECC1 and finally on day 11. In both groups, all dependent variables changed significantly during the 2 days following ECC1. A further acute post-exercise impairment in isometric torque (30 +/- 5%) and flexed elbow angle (20 +/- 4%) was observed following ECC2 (p<0.05), despite EXP subjects producing uniformly lower work and peak eccentric torque values during ECC2 (p<0.05). No other significant differences between the CON and EXP groups were observed throughout the study (p>0.05). These findings suggest that when maximal isokinetic eccentric exercise is repeated two days after experiencing of contraction-induced muscle damage, the recovery time course is not significantly altered.     

Effects of a 7-day eccentric training period on muscle damage and inflammation

PURPOSE: This study examined the effects of a 7-d repeated maximal isokinetic eccentric training period on the indicators of muscle damage and inflammatory response. METHODS: Twenty-two college-age males were randomly assigned to eccentric training (ET) (N = 12) and control groups (CON) (N = 10). The initial exercise was 30 repetitions of maximal voluntary isokinetic eccentric contraction (ECC1) on nondominant elbow flexors with Cybex 6000 at 60 degrees.s-1 angular velocity. The ET group performed the same exercise for the following 6 consecutive days (referred to as ECC2 to ECC7) after ECC1. Upper arm circumference (CIR), range of motion (ROM), and maximal isometric force (MIF) were measured before, immediately after, and every 24 h for 7 consecutive days after ECC1. Plasma creatine kinase (CK), lactate dehydrogenase (LDH), glutamic oxaloacetate transaminase (GOT), leukocyte counts, and serum interleukin-1beta and -6 (IL-1beta, IL-6) levels were assessed before; at 2 h; and at 1, 3, 4, 6, and 7 d after ECC1. Muscle soreness was measured before and for 7 consecutive days after ECC1. RESULTS: The ECC1 produced significant changes in most of the measures for both groups (P < 0.05), with the exception of leukocyte counts (P > 0.05). No indicators of increased damage (P > 0.05) were found from ECC2 to ECC7 for the ET group. CONCLUSION: Continuous intensive isokinetic eccentric training performed with damaged muscles did not exacerbate muscle damage and inflammation after ECC1. In addition, a muscular "adaptation effect" may occur as early as 24 h after ECC1, as shown by the ET group's performance for 6 consecutive days after ECC1.     

Eccentric exercise effect on blood oxidative-stress markers and delayed onset of muscle soreness

PURPOSE: This study examined the effects of a single bout of high-intensity eccentric exercise (EE) on blood protein carbonyls, glutathione status, and muscle damage indicators to ascertain whether blood markers of oxidative stress are elevated at the time delayed onset of muscle soreness (DOMS) occurs. METHODS: Eight healthy men (26.5 +/- 1.5 yr) performed 60 eccentric contractions at approximately 135-150% dominant arm maximum isometric force (MIF) using their nondominant arm elbow flexors. DOMS, range of motion (ROM), MIF, and blood were obtained before, immediately after, and 24, 48, 72, and 96 h after the EE. Blood samples were analyzed for plasma creatine kinase (CK) activity, and protein carbonyls (PC), and erythrocyte glutathione status. RESULTS: A significant decrease in MIF occurred at all times after the EE. ROM decreased from 24 to 96 h, and DOMS increased 24 to 72 h in the nondominant arm as indicated by a repeated measure ANOVA. Plasma CK activity peaked at 72 h (1620 +/- 500 IU x L(-1)) compared with baseline (154 +/- 27 IU x L(-1). Erythrocyte-reduced glutathione (GSH) concentration was not significantly affected by the EE but tended to decrease 23% by 24 h and continued at this level for 96 h. Oxidized glutathione (GSSG) and total glutathione were unchanged over time. A significant increase in plasma PC occurred at 24 and 48 h after eccentric exercise. CONCLUSIONS: The results suggest that 60 EE at 135-150% MIF can result in DOMS, with decreased muscle function and increases in plasma PC at 24 and 48 h without alterations in blood glutathione status.     

Sex differences in response to maximal eccentric exercise

PURPOSE: This study examined sex differences in strength loss, muscle soreness, and serum creatine kinase (CK) and myoglobin (Mb) after high-intensity eccentric exercise of the elbow flexors in a large group of men and women. METHODS: One hundred participants (58 women, 42 men) performed 50 maximal eccentric contractions of the elbow flexor muscles of their nondominant arm. Maximum isometric voluntary contraction (MVC) was recorded at baseline, immediately after exercise, and at 0.5 (12-14 h), 3, 4, 7, and 10 d after exercise. Blood samples for serum CK activity and Mb were taken at baseline and at 4, 7, and 10 d after exercise. Soreness was evaluated at baseline and at 0.5, 3, 4, 7, and 10 d after exercise. RESULTS: Women experienced significantly greater relative strength loss immediately after exercise (-57.8% +/- 19.1) than men (-50.4% +/- 16.9%) (independent t-test; P < or = 0.05), and a greater percentage of women experienced more than 70% strength loss immediately after exercise compared with men (34.4% of women; 7.1% of men). Men exhibited a larger CK response compared with women (ANCOVA; P < or = 0.05), partly because there were more men who were high responders. There were no significant differences between the sexes for serum Mb or soreness measures. Generally, stronger relationships among CK, soreness, and strength-loss measures were found in men compared with women (r = 0.55-0.59 for men; r = 0.12-0.49 for women). CONCLUSION: In response to eccentric exercise, women experienced greater immediate strength loss than men and were more likely to be high responders for immediate strength loss; men experienced greater serum CK activity than women and were more likely to be high responders for increased serum CK. Although the explanation for high responders to eccentric exercise remains unknown, we have shown that there are sex-specific differences in CK and strength-loss response after eccentric exercise.