Effect of elbow joint angle on the magnitude of muscle damage to the elbow flexors

PURPOSE: It has been shown that eccentric actions at a long muscle length result in a larger decrease in force and more muscle tenderness compared with those at a short muscle length. To further investigate the effect of elbow joint angle on the development of muscle damage, this study compared two maximal eccentric exercise regimens in which the starting position of the action was different, but the range of movement was the same. METHODS: One arm of 10 male students performed 24 maximal eccentric actions of the elbow flexors at the elbow joint angle from 0.87 to 2.27 rad (50-130 degrees: S condition) and the other arm at the elbow joint angle from 1.74 to 3.14 rad (100-180 degrees: L condition). Maximal isometric force, range of motion, muscle soreness, plasma creatine kinase activity, upper arm circumference, and B-mode ultrasound pictures of the elbow flexors (US) were measured before and for 5 d postexercise in both conditions. Magnetic resonance imaging (MRI) of the transverse scans of the upper arm was taken at 4 d after exercise. RESULTS: All measures changed significantly (P < 0.01) after exercise for both conditions; however, significantly (P < 0.01) larger changes in the measures were found in the L condition compared with the S condition. MRI and US displayed that only the brachialis was damaged for the S condition but the biceps brachii was also damaged for the L condition. CONCLUSION: The greater development of muscle damage in the L condition compared with the S condition is likely to be associated with the elbow flexors muscles affected by the exercise.     

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.     

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)     

Acute muscle damage as a stimulus for training-induced gains in strength.

PURPOSE: The purpose of this study was to investigate the effect of a single acute bout of maximal eccentric work upon the strength gains during 9 subsequent weeks of strength training. Eccentric work causes acute muscle damage that may initiate compensatory hypertrophy and enhance training-induced gains in strength. METHODS: Twenty-six healthy adults (21 +/- 1 yr, 7 women) trained the elbow flexors 3 d per week for 9 wk. One arm (C) performed purely conventional isotonic training, i.e., lifting and lowering. The other arm (E) began with a single bout of maximal eccentric work but thereafter undertook identical isotonic training. Every week dynamic lifting strength (1 RM) and isometric strength were measured. RESULTS: The results indicated that an acute bout of eccentric muscle damage does not accentuate training-induced gains in strength. Isometric strength of arm E fell by 15 +/- 2% (mean +/- SEM) 2 d after the bout of eccentric work, and, 4 d afterward, plasma creatine kinase levels were 1502 +/- 397 IU.L-1. Although arm E displayed rapid gains in strength from 2 d after the bout of eccentric work, these were not sustained, and for several weeks arm E showed significantly smaller gains in strength than arm C (isometric strength, 2 wk; dynamic lifting strength, 5 wk). CONCLUSIONS: After 9 wk of training, the gains in both isometric and dynamic lifting strength were similar for the two arms. A single bout of damaging eccentric work did not enhance the response to conventional strength training and significantly compromised strength gains for several weeks.     

Effects of number of eccentric muscle actions on first and second bouts of eccentric exercise of the elbow flexors

This study compared changes in indirect markers of muscle damage following eccentric exercise of the elbow flexors among the exercises consisting of different number of eccentric actions. Sixty male athletes were placed into one of the six groups (n=10 per group) based on the number of eccentric actions for the first (ECC1) and second exercise bouts (ECC2). Single bout groups (30, 50, and 70) performed ECC1 only, and repeated bout groups (30-30, 50-50, and 70-70) performed ECC2 3 days after ECC1. Another 10 male athletes performed different number of eccentric actions for ECC1 (30) and ECC2 (70) separated by 3 days (30-70). Changes in maximal isometric strength (MVC), range of motion (ROM), upper arm circumference (CIR), serum creatine kinase activity, myoglobin, and nitric oxide concentrations and muscle soreness for 10 days following ECC1 were compared among groups by two-way repeated measures ANOVA. Changes in MVC, ROM, and CIR following ECC1 were significantly (P<0.05) smaller for the groups that performed 30 eccentric actions compared with other groups. No significant differences between 30 and 30-30, 50 and 50-50, and 70 and 70-70 were evident for the changes in the measures for 10 days following ECC1 except for the acute decreases in MVC and ROM immediately after ECC2 for the repeated bout groups. The 30-30 and 30-70 groups showed similar changes in all criterion measures. It is concluded that recovery from eccentric exercise is not retarded by the second bout of eccentric exercise regardless of the number of eccentric actions.     

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.     

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.     

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.     

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.     

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.     

Decreased EMG median frequency during a second bout of eccentric contractions

PURPOSE: Others have reported preferential recruitment of fast motor units in muscles during performance of eccentric contractions and there is evidence that fast muscle fibers are more susceptible to eccentric contraction-induced injury. We tested the hypothesis that during a second bout of maximal eccentric contractions 1 wk after the first, there would be a reduction in the electromyographic (EMG) median frequency (MF) with minimal change in the EMG root-mean-square (RMS), indicating greater reliance on slower motor units. This could provide an explanation for the enhanced resistance to eccentric contraction-induced injury after a single bout of eccentric exercise. METHODS: Human subjects performed 50 maximal voluntary eccentric (N = 10) or concentric (N = 10) contractions of the anterior crural muscles on two occasions separated by 1 wk. To determine whether MF changes during the second bout could be a consequence of injury to fibers in fast motor units, the anterior crural muscles of mice were electrically stimulated to perform 50 maximal eccentric (N = 10) or concentric (N = 9) contractions on two occasions separated by 1 wk. In both the humans and mice, torque production and tibialis anterior muscle RMS and MF were measured during the two exercise bouts. RESULTS: In human tibialis anterior muscle, MF was 30% lower (P < 0.01) during the second eccentric bout although RMS was the same. In the mice, RMS and MF were unchanged at any time after the first eccentric bout despite torque deficits similar to those observed in the humans. CONCLUSIONS: The data indicate that with repetition of maximal voluntary eccentric contractions, there is an increased activation of slow motor units and a concomitant decrease in activation of fast units.     

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.     

Greater muscle damage induced by fast versus slow velocity eccentric exercise

Debate exists concerning the effect of contraction velocity on muscle damage, and few human studies have yet to address this issue. This study examined whether the velocity of eccentric exercise affected the magnitude of muscle damage. Twelve untrained subjects performed a series of slow velocity isokinetic eccentric elbow flexions (SV: 30 degrees . s (-1)) of one arm and a fast velocity exercise (FV: 210 degrees . s (-1)) of the other arm, separated by 14 days. In order to standardise the time under tension (120 s) for the two conditions, the number of muscle actions for SV was 30 and 210 for FV. Criterion measures consisted of maximal voluntary torque for isometric, concentric (4 velocities) and eccentric contractions (2 velocities), range of motion (ROM) and relaxed elbow joint angle (RANG), upper arm circumference, muscle soreness and plasma creatine kinase (CK) activity. Measures were taken before, immediately after, 0.5 hour and 24 - 168 hours (240 hours for CK) after each eccentric exercise protocol, and changes in the measures over time were compared between FV and SV by two-way repeated measures ANOVA. Both protocols resulted in significant decrements in isometric and dynamic torque (p < 0.01), but FV showed significantly (p < 0.05) greater reductions over time ( approximately 55 %) and a slower recovery compared to SV ( approximately 30 %). Significantly (p < 0.05) larger decreases in, and delayed recovery of, ROM and RANG were evident after FV compared to SV. FV had significantly (p < 0.05) larger increases in upper arm circumference and soreness compared to SV, and peak plasma CK activity was 4.5-fold greater (p < 0.05) following FV than SV. These results suggest that, for the same time under tension, fast velocity eccentric exercise causes greater muscle damage than slow velocity exercise in untrained subjects.     

Muscle function after exercise-induced muscle damage and rapid adaptation.

This brief review focuses on the time course of changes in muscle function and other correlates of muscle damage following maximal effort eccentric actions of the forearm flexor muscles. Data on 109 subjects are presented to describe an accurate time course of these changes and attempt to establish relationships among the measures. Peak soreness is experienced 2-3 d postexercise while peak swelling occurs 5 d postexercise. Maximal strength and the ability to fully flex the arm show the greatest decrements immediately after exercise with a linear restoration of these functions over the next 10 d. Blood creatine kinase (CK) levels increase precipitously at 2 d after exercise which is also the time when spontaneous muscle shortening is most pronounced. Whether the similarity in the time courses of some of these responses implies that they are caused by similar factors remains to be determined. Performance of one bout of eccentric exercise produces an adaptation such that the muscle is more resistant to damage from a subsequent bout of exercise. The length of the adaptation differs among the measures such that when the exercise regimens are separated by 6 wk, all measures show a reduction in response on the second, compared with the first, bout. After 10 wk, only CK and muscle shortening show a reduction in response. After 6 months only the CK response is reduced. A combination of cellular factors and neurological factors may be involved in the adaptation process.     

Characteristics of isometric and dynamic strength loss following eccentric exercise-induced muscle damage

Angle-specific isometric strength and angular velocity-specific concentric strength of the knee extensors were studied in eight subjects (5 males and 3 females) following a bout of muscular damaging exercise. One hundred maximal voluntary eccentric contractions of the knee extensors were performed in the prone position through a range of motion from 40 degrees to 140 degrees (0 degrees = full extension) at 1.57 rads(-1). Isometric peak torque was measured whilst seated at 10 degrees and 80 degrees knee flexion, corresponding to short and optimal muscle length, respectively. Isokinetic concentric peak torque was measured at 0.52 and 3.14 rad x s(-1). Plasma creatine kinase (CK) activity was also measured from a fingertip blood sample. These measures were taken before, immediately after and on days 1, 2, 4, and 7 following the eccentric exercise. The eccentric exercise protocol resuited in a greater relative loss of strength (P< 0.05) at short muscle length (76.3 +/- 2.5% of pre-exercise values) compared to optimal length (82.1 +/- 2.7%). There were no differences in the relative strength loss between isometric strength at optimal length and isokinetic concentric strength at 0.52 and 3.14 rad x s(-1). CK activity was significantly elevated above baseline at days 4 (P < 0.01) and 7 (P < 0.01). The greater relative strength loss at short muscle length appeared to persist throughout the seven-day testing period and provides indirect evidence of a shift in the angle-torque relationship towards longer muscle lengths. The results lend partial support to the popping sarcomere hypothesis of muscle damage, but could also be explained by an impairment of activation at short muscle lengths.     

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.     

Sensory level electrical muscle stimulation: effect on markers of muscle injury

Background: Monophasic high voltage stimulation (MHVS) is widely prescribed for the treatment of inflammation associated with muscle injury. However, limited scientific evidence exists to support its purported benefits in humans.

Objective: To examine the efficacy of early initiation of MHVS treatment after muscle injury.

Methods: In a randomised, cross over design, 14 men performed repetitive eccentric contractions of the elbow flexor muscles followed by either MHVS or control treatment. MHVS treatments were applied five minutes and 3, 6, 24, 48, 72, 96, and 120 hours after eccentric contractions.

Results: MHVS resulted in a significant reduction (p<0.05) in delayed onset muscle soreness 24 hours after eccentric exercise compared with controls. Elbow extension was significantly increased immediately after administration of MHVS compared with controls. No significant differences were observed between MHVS treatment and controls for maximal isometric strength, flexed arm angle, or arm volume.

Conclusions: Early and frequent application of MHVS may provide transient relief from delayed onset muscle soreness and short term improvements in range of motion after injurious exercise. However, MHVS treatment may not enhance recovery after muscle injury because of lack of improvements in strength and active range of motion.

     

A COX-2 inhibitor reduces muscle soreness, but does not influence recovery and adaptation after eccentric exercise

The aim of this study was to investigate the effect of a cyclooxygenase (COX)-2 inhibitor on the recovery of muscle function, inflammation, regeneration after, and adaptation to, unaccustomed eccentric exercise. Thirty-three young males and females participated in a double-blind, placebo-controlled experiment. Seventy unilateral, voluntary, maximal eccentric actions with the elbow flexors were performed twice (bouts 1 and 2) with the same arm, separated by 3 weeks. The test group participants were administered 400 mg/day of celecoxib for 9 days after bout 1. After both bouts 1 and 2, concentric and isometric force-generating capacity was immediately reduced (∼40–50%), followed by the later appearance of muscle soreness and increased serum creatine kinase levels. Radiolabelled autologous leukocytes (detected by scintigraphy) and monocytes/macrophages (histology) accumulated in the exercised muscles, simultaneously with increased satellite cell activity. These responses were reduced and recovery was faster after bout 2 than 1, demonstrating a repeated-bout effect. No differences between the celecoxib and placebo groups were detected, except for muscle soreness, which was attenuated by celecoxib. In summary, celecoxib, a COX-2 inhibitor, did not detectably affect recovery of muscle function or markers of inflammation and regeneration after unaccustomed eccentric exercise, nor did the drug influence the repeated-bout effect. However, it alleviated muscle soreness.     

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.     

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.