Time-course of changes in inflammatory response after whole-body cryotherapy multi exposures following severe exercise

The objectives of the present investigation was to analyze the effect of two different recovery modalities on classical markers of exercise-induced muscle damage (EIMD) and inflammation obtained after a simulated trail running race. Endurance trained males (n = 11) completed two experimental trials separated by 1 month in a randomized crossover design; one trial involved passive recovery (PAS), the other a specific whole body cryotherapy (WBC) for 96 h post-exercise (repeated each day). For each trial, subjects performed a 48 min running treadmill exercise followed by PAS or WBC. The Interleukin (IL) -1 (IL-1), IL-6, IL-10, tumor necrosis factor alpha (TNF-α), protein C-reactive (CRP) and white blood cells count were measured at rest, immediately post-exercise, and at 24, 48, 72, 96 h in post-exercise recovery. A significant time effect was observed to characterize an inflammatory state (Pre vs. Post) following the exercise bout in all conditions (p<0.05). Indeed, IL-1β (Post 1 h) and CRP (Post 24 h) levels decreased and IL-1ra (Post 1 h) increased following WBC when compared to PAS. In WBC condition (p<0.05), TNF-α, IL-10 and IL-6 remain unchanged compared to PAS condition. Overall, the results indicated that the WBC was effective in reducing the inflammatory process. These results may be explained by vasoconstriction at muscular level, and both the decrease in cytokines activity pro-inflammatory, and increase in cytokines anti-inflammatory.     

Muscle damage alters the metabolic response to dynamic exercise in humans: a 31P-MRS study

We used 31P-magnetic resonance spectroscopy to test the hypothesis that exercise-induced muscle damage (EIMD) alters the muscle metabolic response to dynamic exercise, and that this contributes to the observed reduction in exercise tolerance following EIMD in humans. Ten healthy, physically active men performed incremental knee extensor exercise inside the bore of a whole body 1.5-T superconducting magnet before (pre) and 48 h after (post) performing 100 squats with a load corresponding to 70% of body mass. There were significant changes in all markers of muscle damage [perceived muscle soreness, creatine kinase activity (434% increase at 24 h), and isokinetic peak torque (16% decrease at 24 h)] following eccentric exercise. Muscle phosphocreatine concentration ([PCr]) and pH values during incremental exercise were not different pre- and post-EIMD (P > 0.05). However, resting inorganic phosphate concentration ([P(i)]; pre: 4.7 ± 0.8; post: 6.7 ± 1.7 mM; P < 0.01) and, consequently, [P(i)]/[PCr] values (pre: 0.12 ± 0.02; post: 0.18 ± 0.05; P < 0.01) were significantly elevated following EIMD. These mean differences were maintained during incremental exercise (P < 0.05). Time to exhaustion was significantly reduced following EIMD (519 ± 56 and 459 ± 63 s, pre- and post-EIMD, respectively, P < 0.001). End-exercise pH (pre: 6.75 ± 0.04; post: 6.83 ± 0.04; P < 0.05) and [PCr] (pre: 7.2 ± 1.7; post: 14.5 ± 2.1 mM; P < 0.01) were higher, but end-exercise [P(i)] was not significantly different (pre: 19.7 ± 1.9; post: 21.1 ± 2.6 mM, P > 0.05) following EIMD. The results indicate that alterations in phosphate metabolism, specifically the elevated [P(i)] at rest and throughout exercise, may contribute to the reduced exercise tolerance observed following EIMD.     

Creatine kinase isoenzyme activity during and after an ultra-distance (200 km) run

It is commonly assumed that creatine kinase (CK) activity in plasma is related to the state of an inflammatory response at 24-48 h, and also it has shown biphasic patterns after a marathon run. No information is available on CK isoenzymes after an ultra-marathon run. The purpose of the present study is to examine the CK isoenzymes after a 200 km ultra-marathon run and during the subsequent recovery. Blood samples were obtained during registration 1 2 h before the 200-km race and during the race at 100 km, 150 km and at the end of 200 km, as well as after a 24 h period of recovery. Thirty-two male ultra-distance runners participated in the study. Serum CPK showed a marked increase throughout the race and 24 h recovery period (p < 0.001). Serum CK during the race occurs mostly in the CK-MM isoform and only minutely in the CK-MB isoform and is unchanged in the CK-BB isoform. High-sensitivity C-reactive protein (hs-CRP), oestradiol, AST and ALT increased significantly from the pre-race value at 100 km and a further increase took place by the end of the 200 km run. The results of our study demonstrate a different release pattern of creatine kinase after an ultra-distance (200 km) run compared to the studies of marathon running and intense eccentric exercise, and changes in several biomarkers, indicative of muscle damage during the race, were much more pronounced during the latter half (100–200 km) of the race. However, the increases in plasma concentration of muscle enzymes may reflect not only structural damage, but also their rate of clearance.     

Circulating soluble intercellular adhesion molecule-1 (sICAM-1) after exercise-induced muscular damage: Does the use of whole-body cryostimulation influence its concentration in blood?

As soluble intercellular adhesion molecule-1 (sICAM-1) was recently hypothesized to be a key player in the mechanisms involved in exercise-induced muscular damage (EIMD), we investigated its circulating concentration changes in athletes before and after EIMD with and without the use of whole-body cryostimulation (WBC; 3 min at −110 °C) at the exercise end and repeated once a day during 4 days.We previously characterized plasma specimens from 11 endurance athletes who performed twice (randomized crossover design) strenuous running leading to EIMD, followed by passive recovery or WBC. Muscle soreness and inflammatory response were observed in both cases but the use of WBC induced a significant reduction in these responses (PlosOne 2011; 6:e22748). We now found that sICAM-1 concentration slightly increased in both circumstances and remained elevated for 24 h (p < 0.01). However, no significant WBC effect was observed concerning sICAM-1 changes indicating that this compound is not a major player both in EIMD and WBC physiological impacts.     

Efficacy of lower limb compression and combined treatment of manual massage and lower limb compression on symptoms of exercise-induced muscle damage in women

Strategies to manage the symptoms of exercise-induced muscle damage (EIMD) are widespread, though are often based on anecdotal evidence. The aim of this study was to determine the efficacy of a combination of manual massage and compressive clothing and compressive clothing individually as recovery strategies after muscle damage. Thirty-two female volunteers completed 100 plyometric drop jumps and were randomly assigned to a passive recovery (n = 17), combined treatment (n = 7), or compression treatment group (n = 8). Indices of muscle damage (perceived soreness, creatine kinase activity, isokinetic muscle strength, squat jump, and countermovement jump performance) were assessed immediately before and after 1, 24, 48, 72, and 96 hours of plyometric exercise. The compression treatment group wore compressive tights for 12 hours after damage and the combined treatment group received a 30-minute massage immediately after damaging exercise and wore compression stockings for the following 11.5 hours. Plyometric exercise had a significant effect on all indices of muscle damage (p < 0.05). The treatments significantly reduced decrements in isokinetic muscle strength, squat jump performance, and countermovement jump performance and reduced the level of perceived soreness in comparison with the passive recovery group (p < 0.05). The addition of sports massage to compression after muscle damage did not improve performance recovery, with recovery trends being similar in both treatment groups. The treatment combination of massage and compression significantly moderated perceived soreness at 48 and 72 hours after plyometric exercise (p < 0.05) in comparison with the passive recovery or compression alone treatment. The results indicate that the use of lower limb compression and a combined treatment of manual massage with lower limb compression are effective recovery strategies following EIMD. Minimal performance differences between treatments were observed, although the combination treatment may be beneficial in controlling perceived soreness.     

The effects of estrogen on indices of skeletal muscle tissue damage after eccentric exercise in postmenopausal women

This study examined if estrogen (E) usage (in the form of hormone replacement therapy [HRT]) has a protective effect on skeletal muscle damage in postmenopausal women. Nine postmenopausal women (age 55.2 +/- 9.9 [mean +/- SD]) performed two exercise sessions at 70% of their maximal heart rate on HRT (E-HI) and without HRT (E-LO; following a 28-45 day HRT washout). All subjects followed a condition order of E-HI then E-LO with at least 42 days between exercise sessions. Serum creatine kinase (CK), perceived delayed onset muscle soreness (DOMS), and maximal quadriceps isometric force (MIF) were taken pre-exercise, 24, 48 and 72-hr post exercise. E-HI and E-LO conditions produced a rise in CK (p < 0.001) after exercise; but CK after E-HI was greater than in E-LO (p < 0.001) at 24 hours and at 48 hours. DOMS was significantly elevated at 24, 48, and 72-hr post each exercise session (p < 0.05). The greatest peak DOMS score occurred during the E-HI condition. MIF was similarly reduced after each exercise session (p < 0.05). These results suggest elevated E does not offer a protective effect to skeletal muscle; however, design limitations (i.e., condition order) confound the present data. Interestingly, an association between peak-CK during the E-LO condition and the number of washout days (r = +0.707, p < 0.05) between conditions existed. This suggests a longer washout period may be necessary to elucidate the actual E effects on skeletal muscle. These findings suggest that more work correcting for the present design limitations is warranted on this topic.     

The effect of contrast water therapy on symptoms of delayed onset muscle soreness

This study examined the effect of contrast water therapy (CWT) on the physiological and functional symptoms of delayed onset muscle soreness (DOMS) following DOMS-inducing leg press exercise. Thirteen recreational athletes performed 2 experimental trials separated by 6 weeks in a randomized crossover design. On each occasion, subjects performed a DOMS-inducing leg press protocol consisting of 5 x 10 eccentric contractions (180 seconds recovery between sets) at 140% of 1 repetition maximum (1RM). This was followed by a 15-minute recovery period incorporating either CWT or no intervention, passive recovery (PAS). Creatine kinase concentration (CK), perceived pain, thigh volume, isometric squat strength, and weighted jump squat performance were measured prior to the eccentric exercise, immediately post recovery, and 24, 48, and 72 hours post recovery. Isometric force production was not reduced below baseline measures throughout the 72-hour data collection period following CWT ( approximately 4-10%). However, following PAS, isometric force production (mean +/- SD) was 14.8 +/- 11.4% below baseline immediately post recovery (p < 0.05), 20.8 +/- 15.6% 24 hours post recovery (p < 0.05), and 22.5 +/- 12.3% 48 hours post recovery (p < 0.05). Peak power produced during the jump squat was significantly reduced (p < 0.05) following both PAS (20.9 +/- 13.4%) and CWT (12.8 +/- 8.0%), with the mean reduction in power for PAS being marginally (not significantly) greater than for CWT (effect size = 0.76). Thigh volume measured immediately following CWT was significantly less than PAS. No significant differences in the changes in CK were found; in addition, there were no significant (p > 0.01) differences in perceived pain between treatments. Contrast water therapy was associated with a smaller reduction, and faster restoration, of strength and power measured by isometric force and jump squat production following DOMS-inducing leg press exercise when compared to PAS. Therefore, CWT seems to be effective in reducing and improving the recovery of functional deficiencies that result from DOMS, as opposed to passive recovery.     

The effects of exercise-induced muscle damage on cycling time-trial performance

Previous research has advocated that plyometric training improves endurance performance. However, a consequence of such a training is the immediate and prolonged appearance of exercise-induced muscle damage (EIMD). This study examined whether a single bout of plyometric exercise, designed to elicit muscle damage, affected cycling endurance performance. Seventeen participants were randomly assigned to either a muscle damage (n = 7 men, 1 woman) or nonmuscle damage (n = 8 men, 1 woman) group. Before and at 48 hours, participants were measured for perceived muscle soreness, peak isokinetic strength, and physiological, metabolic, and perceptual responses during 5-minute submaximal cycling at ventilatory threshold (VT) and a 15-minute time trial. Perceived muscle soreness and isokinetic strength (p < 0.05) were significantly altered in the muscle damage group after EIMD. No changes in heart rate or blood lactate were evident during submaximal exercise (p > 0.05). However, VO2, V(E), and rating of perceived exertion (RPE) values were increased at VT in the muscle damage group at 48 hours after EIMD (p < 0.05). During the time trial, mean power output, distance covered, and VO2 were lower in the muscle damage group at 48 hours after EIMD (p < 0.05). However, there was no change in RPE (p > 0.05), suggesting effort perception was unchanged during time-trial performance after EIMD. In conclusion, individuals using concurrent plyometric and endurance training programs to improve endurance performance should be aware of the acute impact of muscle-damaging exercise on subsequent cycling performance.     

The Effects of Estrogen on Indices of Skeletal Muscle Tissue Damage after Eccentric Exercise in Postmenopausal Women

This study examined if estrogen (E) usage (in the form of hormone replacement therapy (HRT)) has a protective effect on skeletal muscle damage in postmenopausal women. Nine postmenopausal women (age 55.2 ± 9.9 [mean ± SD]) performed two exercise sessions at 70% of their maximal heart rate on HRT (E-HI) and without HRT (E-LO; following a 28–45 day HRT washout). All subjects followed a condition order of E-HI and then E-LO with at least 42 days between exercise sessions. Serum creatine kinase (CK), perceived delayed onset muscle soreness (DOMS), and maximal quadriceps isometric force (MIF) were determined before exercise and 24, 48, and 72 h after exercise. E-HI and E-LO conditions produced a rise in CK (p < 0.001) after exercise, but CK after E-HI was greater than in E-LO (p < 0.001) at 24 and 48 h. DOMS was significantly elevated at 24, 48, and 72 h after each exercise session (p < 0.05). The greatest peak DOMS score occurred during the E-HI condition. MIF was similarly reduced after each exercise session (p < 0.05). These results suggest that elevated E does not offer a protective effect to skeletal muscle; however, design limitations (i.e., condition order) confound the present data. Interestingly, an association between peak CK during the E-LO condition and the number of washout days (r = +0.707, p < 0.05) between conditions existed. This suggests that a longer washout period may be necessary to elucidate the actual effects of E on skeletal muscle. These findings suggest that more work on this topic, correcting for the present design limitations, is warranted.     

Enhanced Glycogen Storage of a Subcellular Hot Spot in Human Skeletal Muscle during Early Recovery from Eccentric Contractions

Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen synthesis, as described by the product of glycogen particle size and number, is dependent on the time course of recovery after exercise and carbohydrate availability. In the present study, we investigated the subcellular distribution of glycogen in fibers with high (type I) and low (type II) mitochondrial content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies for analysis included time points 3, 24 and 48 h post exercise from the exercising leg, whereas biopsies corresponding to prior to and at 48 h after the exercise bout were collected from the non-exercising, control leg. Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles. In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber’s oxidative capacity, and the time course of recovery. The early enhanced storage of intramyofibrillar glycogen after the eccentric contractions may entail important implications for muscle function and fatigue resistance.     

Assessment of eccentric exercise-induced muscle damage of the elbow flexors by tensiomyography

Exercise induced muscle damage (EIMD) impairs maximal torque production which can cause a decline in athletic performance and/or mobility. EIMD is commonly assessed by using maximal voluntary contraction (MVC), creatine kinase (CK) and muscle soreness. We propose as an additional technique, tensiomyography (TMG), recently introduced to measure mechanical and muscle contractile characteristics. The purpose of this study was to determine the validity of TMG in detecting changes in maximal torque following EIMD. Nineteen participants performed eccentric elbow flexions to achieve EIMD on the non- dominant arm and used the dominant elbow flexor as a control. TMG parameters, MVC and rate of torque development (RTD) were measured prior to EIMD and repeated for another six consecutive days. Creatine kinase, muscle soreness and limb girth were also measured during this period. Twenty four hours after inducing EIMD, MVC torque, RTD and TMG maximal displacement had significantly (p<0.01) declined by 37%, 44% and 31%, respectively. By day 6 MVC, RTD and TMG recovered to 12%, 24% and 17% of respective pre-EIMD values. In conclusion, as hypothesised TMG maximal displacement significantly followed other standard EIMD responses. This could therefore be useful in detecting muscle damage from impaired muscle function and its recovery following EIMD.     

MUSCLE DAMAGE AFTER A TENNIS MATCH IN YOUNG PLAYERS

The present study investigated changes in indirect markers of muscle damage following a simulated tennis match play using nationally ranked young (17.6 ± 1.4 years) male tennis players. Ten young athletes played a 3-hour simulated match play on outdoor red clay courts following the International Tennis Federation rules. Muscle soreness, plasma creatine kinase activity (CK), serum myoglobin concentration (Mb), one repetition maximum (1RM) squat strength, and squat jump (SJ) and counter movement jump (CMJ) heights were assessed before, immediately after, and 24 and 48 h after the simulated match play. All parameters were also evaluated in a non-exercised group (control group). A small increase in the indirect markers of muscle damage (muscle soreness, CK and Mb) was detected at 24-48 hours post-match (p < 0.05). A marked acute decrement in neuromuscular performance (1RM squat strength: -35.2 ± 10.4%, SJ: -7.0 ± 6.0%, CMJ: -10.0 ± 6.3%) was observed immediately post-match (p < 0.05). At 24 h post-match, the 1RM strength and jump heights were not significantly different from the baseline values. However, several players showed a decrease of these measures at 24 h after the match play. The simulated tennis match play induced mild muscle damage in young players. Coaches could monitor changes in the indirect markers of muscle damage to assess athletes’ recovery status during training and competition.     

Plyometric exercise increases serum indices of muscle damage and collagen breakdown

The aim of the present study was to examine the effect of acute plyometric exercise on indices of muscle damage and collagen breakdown. Nine untrained men performed an intense bout of plyometric jumping exercises (experimental group) and nine men remained at rest (control group). Seven days before and 24, 48, and 72 hours after plyometric exercise or rest, several physiological and biochemical indices of muscle damage and two biochemical indices of collagen damage were determined. No significant changes in concentric and eccentric peak torque of knee extensors and flexors or flexion and extension range of motion were found after the plyometric exercise. Delayed-onset muscle soreness increased 48 hours after exercise. Creatine kinase increased 48 and 72 hours post exercise, whereas lactate dehydrogenase increased 24, 48, and 72 hours post exercise. Serum hydroxyproline increased 24 hours post exercise, peaked at 48 hours, and remained elevated up to 72 hours post exercise. Hydroxylysine (which was measured only before exercise and at 48 hours) was found increased 48 hours post exercise. No differences were found in any physiological or biochemical index in the control group. Intense plyometric exercise increased muscle damage, delayed-onset muscle soreness, and serum indices of collagen breakdown without a concomitant decrease in the functional capacity of muscles. Hydroxyproline and hydroxylysine levels in serum seem promising measures for describing exercise-induced collagen degradation. Coaches need to keep in mind that by using plyometric activities, despite the increased muscle damage and collagen turnover that follow, it is not necessarily accompanied by decreases in skeletal muscle capacity.     

The effects of ibuprofen on delayed muscle soreness and muscular performance after eccentric exercise

The purpose of this study was to examine the effects of ibuprofen on delayed onset muscle soreness (DOMS), indirect markers of muscle damage and muscular performance. Nineteen subjects (their mean [+/- SD] age, height, and weight was 24.6 +/- 3.9 years, 176.2 +/- 11.1 cm, 77.3 +/- 18.7 kg) performed the eccentric leg curl exercise to induce muscle soreness in the hamstrings. Nine subjects took an ibuprofen pill of 400 mg every 8 hours within a period of 48 hours, whereas 10 subjects received a placebo randomly (double blind). White blood cells (WBCs) and creatine kinase (CK) were measured at pre-exercise, 4-6, 24, and 48 hours after exercise and maximal strength (1 repetition maximum). Vertical jump performance and knee flexion range of motion (ROM) were measured at pre-exercise, 24 and 48 hours after exercise. Muscle soreness increased (p < 0.05) in both groups after 24 and 48 hours, although the ibuprofen group yielded a significantly lower value (p < 0.05) after 24 hours. The WBC levels were significantly (p < 0.05) increased 4-6 hours postexercise in both groups with no significant difference (p > 0.05) between the 2 groups. The CK values increased (p < 0.05) in the placebo group at 24 and 48 hours postexercise, whereas no significant differences (p > 0.05) were observed in the ibuprofen group. The CK values of the ibuprofen group were lower (p < 0.05) after 48 hours compared with the placebo group. Maximal strength, vertical jump performance, and knee ROM decreased significantly (p < 0.05) after exercise and at 24 and 48 hours postexercise in both the placebo and the ibuprofen groups with no differences being observed (p > 0.05) between the 2 groups. The results of this study reveal that intake of ibuprofen can decrease muscle soreness induced after eccentric exercise but cannot assist in restoring muscle function.     

Effect of BCAA intake during endurance exercises on fatigue substances,muscle damage substances,and energy metabolism substances

The increase rate of utilization of branched-chain amino acids (BCAA) by muscle is reduced to its plasma concentration during prolonged exercise leading to glycogen. BCAA supplementation would reduce the serum activities of intramuscular enzymes associated with muscle damage. To examine the effects of BCAA administration on fatigue substances (serotonin, ammonia and lactate), muscle damage substances (CK and LDH) and energy metabolism substances (FFA and glucose) after endurance exercise. Subjects (n = 26, college-aged males) were randomly divided into an experimental (n = 13, EXP) and a placebo (n = 13, CON) group. Subjects both EXP and CON performed a bout of cycle training (70% VO₂max intensity) to exhaustion. Subject in the EXP were administrated BCAA (78ml/kg·w) prior to the bout of cycle exercise. Fatigue substances, muscle damage substances and energy metabolism substances were measured before ingesting BCAAs and placebos, 10 min before exercise, 30 min into exercise, immediately after exercise, and 30 min after exercise. Data were analyzed by two-way repeated measure ANCOVA, correlation and statistical significance was set at p < 0.05. The following results were obtained from this study; 1. In the change of fatigue substances : Serotonin in the EXP tended to decreased at the 10 min before exercise, 30 min into exercise, post exercise, and recovery 30 min. Serotonin in the CON was significantly greater than the EXP at the10 min before exercise and recovery 30. Ammonia in the EXP was increased at the 10 min before exercise, 30 min into exercise, and post exercise, but significantly decreased at the recovery 30min (p < 0.05). Ammonia in the CON was significantly lower than the EXP at the 10 min before exercise, 30 min into exercise, and post exercise (p < 0.05). Lactate in the EXP was significantly increased at the 30 min into exercise and significantly decreased at the post exercise and recovery 30 min. Lactate in the CON was significantly lower than the EXP at the post exercise (p < 0.05). 2. In the change of muscle damage substances : CK in the EXP was decreased at the 10 min before exercise and increased at the 30 min into exercise and then decreased at the post exercise and recovery 30 min. CK in the CON was greater than the EXP. LDH in the EXP was decreased at the 10 min before exercise and increased at the 30 min into exercise and then decreased at the post exercise and recovery 30 min. LDH in the CON was higher than the EXP. 3. In the change of energy metabolism substances :Glucose in the EXP tended to decrease at the 10 min before exercise, 30 min into exercise, post exercise and recovery 30 min. Glucose in the CON was significantly greater than the EXP at the recovery 30 min (p < .05). FFA in both EXP and CON was increased at the post exercise and recovery 30 min. % increase for FFA in the EXP was greater than the CON at the post exercise and recovery 30 min. 4. The relationship of the fatigue substances, muscle damage substances and energy metabolism substances after endurance exercise indicated strongly a positive relationship between LDH and ammonia and a negative relationship between LDH and FFA in the EXP. Also, there were a strong negative relationship between glucose and FFA and a positive relationship between glucose and serotonin in the EXP. There was a strong positive relationship between CK and LDH and a strong negative relationship between FFA and glucose in the CON. These results indicate that supplementary BCAA decreased serum concentrations of the intramuscular enzymes as CK and LDH following exhaustive exercise. This observation suggests that BCAA supplementation may reduce the muscle damage associated with endurance exercise.     

Prior eccentric exercise reduces v[combining dot above]o2peak and ventilatory threshold but does not alter movement economy during cycling exercise

Exercise-induced muscle damage (EIMD) has been shown to reduce force production and result in delayed-onset soreness and pain in the damaged muscle(s). Cycling in the presence of EIMD reduces peak power output and time-trial performance. However, its effect on peak aerobic capacity has not been widely studied. The purpose of this study was to examine the impact of EIMD targeted specifically to the quadriceps muscle group on peak oxygen consumption (V[Combining Dot Above]O2peak) during cycling. Ten participants (4 men, 6 women) completed a V[Combining Dot Above]O2peak test on a cycle ergometer before and 48 hours after performing 24 eccentric contractions with their right and left quadriceps with a weight equal to 120% of 1-repetition maximal concentric strength (1RM). The EIMD was assessed using 1RM, and muscle soreness was assessed using a 100-mm visual analog scale. The presence of EIMD was confirmed by a 9% reduction in 1RM (p = 0.0001) and increased ratings of soreness from 2.4 ± 2.1 to 24.6 ± 10.8 mm (p = 0.001). The V[Combining Dot Above]O2peak was reduced from 46.2 ± 9.7 to 41.8 ± 10.7 ml·kg·min (10%; p = 0.01) with participants terminating exercise at lower heart rates 191 ± 9 vs. 186 ± 10 b·min (p = 0.02) and power output 248 ± 79 vs. 238 ± 81 W (p = 0.02) after EIMD. Additionally, ventilatory threshold decreased from 34.2 ± 7.8 to 30.5 ± 8.5 ml·kg·min (11%; p = 0.031). Despite the reduction in V[Combining Dot Above]O2peak, cycling economy (p = 0.17) did not differ pre-EIMD and post-EIMD. These findings indicate that EIMD reduced peak aerobic exercise capacity to an extent that could result in meaningful reductions in exercise performance. The reduction is likely attributable to a combination of reduced strength, earlier accumulation of lactic acid, and heightened muscle pain during exercise.     

Effects of unaccustomed downhill running on muscle damage,oxidative stress,and leukocyte apoptosis

[Purpose]

The purpose of this study was to investigate the effect of unaccustomed downhill running on muscle damage, oxidative stress, and leukocyte apoptosis.

[Methods]

Thirteen moderately trained male subjects performed three 40 min treadmill runs at ~70% VO_2max on separate days: a level run (L) followed by two downhill runs (DH1 and DH2). Blood samples were taken at rest (PRE) and immediately (POST), 2 h, 24 h, and 48 h after each run. Data were analyzed using 2-way repeated measures ANOVA with post hoc Tukey tests.

[Results]

Creatine kinase (CK) activity and oxidative stress level were significantly elevated at 24 h and 48 h following DH1 (P < 0.05). The level of oxidative stress at the POST measurement following DH1 and DH2 was greater than PRE. The rate of leukocyte apoptosis was significantly increased at the POST measurement following all three runs, and remained elevated for up to 48 h following DH1 (P < 0.01).

[Conclusion]

CK activity and oxidative stress were elevated following an acute bout of moderate intensity downhill running, resulting in a greater apoptotic response at 24 h and 48 h post-exercise in comparison with level grade running or a second downhill run. These elevations were blunted following DH2. Although the link between exercise-induced muscle damage and leukocyte apoptosis is currently unknown, the differential response to DH1 vs. L and DH2 indicates that it may be mediated by the elevation of oxidative stress.     

Effects of whole body vibration on muscle contractile properties in exercise induced muscle damaged females

Determining muscle contractile properties following exercise is critical in understanding neuromuscular function. Following high intensity training, individuals often experience exercise induced muscle damage (EIMD). The purpose of this investigation was to determine the effect of whole-body vibration (WBV) on muscle contractile properties following EIMD. Twenty-seven females volunteered for 7 sessions and were randomly assigned to a treatment or control group. Muscle contractile properties were assessed via voluntary torque (VT), peak twitch torque (TT), time to reach peak torque, half relaxation time of twitch torque, percent activation (%ACT), rate of rise (RR), rate of decline (RD), mean and peak electromyography during maximum voluntary isometric contraction. Two testing sets were collected each day, consisting of pre measures followed by WBV or control and post measures. A mixed factor analysis of variance was conducted for each variable. %ACT measures found baseline being less than day 1 in both measures in the control group. TT was found to be greater in the control group compared to WBV group. TT and VT baseline measures were greater than all other time points. RR showed control group had higher values than WBV group. These results indicate that WBV following EIMD had some positive effects on muscle contractile properties.     

Equal volumes of high and low intensity of eccentric exercise in relation to muscle damage and performance

We examined differences in muscle damage and muscle performance perturbations in relation to the same volumes of high (HI) and low intensity (LI) of eccentric exercise. Untrained young healthy men (n = 12) underwent 2 isokinetic quadriceps eccentric exercise sessions, 1 on each randomly selected leg, separated by a 2-week interval. In the first session subjects performed HI exercise (i.e., 12 sets of 10 maximal voluntary efforts). In the second session, volunteers were subjected to continuous exercise of LI (50% of peak torque) until the total work done was approximately equal to that generated during HI. Muscle damage (serum creatine kinase concentration [CK], delayed onset of muscle soreness, and range of motion) and muscle performance (eccentric [EPT] and isometric peak torque [IPT]) indicators were assessed pre-exercise and 24, 48, 72, and 96 hours postexercise. Compared to baseline data, changes in muscle damage indicators were significantly different (p < 0.05) at almost all postexercise time points in both conditions. However, apart from the significant elevation of CK at 24 hours after HI (p < 0.05), no other significant differences were observed between the 2 exercise conditions (p > 0.05). The main finding in relation to muscle performance was that decrements following HI exercise were significantly greater (p < 0.05) compared to LI. Compared with baseline data, the EPT values following HI and LI exercise were as follows: 24 hours, 72.1% vs. 92%; 48 hours, 81.9% vs. 94.8%; 72 hours, 77.7% vs. 100.6%; 96 hours, 86.8% vs. 107.9%. The corresponding data for IPT were as follows: 24 hours, 86.4% vs. 102.8%; 48 hours, 84.2% vs. 107%; 72 hours, 84.8% vs. 109.2%; 96 hours, 86.8% vs. 114.4%. These results indicate that matching volumes of HI and LI eccentric exercise have similar effects on muscle damage, but HI has a more prominent effect on muscle performance.     

Influence of estrogen on markers of muscle tissue damage following eccentric exercise.

This study tested the hypothesis that estrogen levels of women influences the development of a muscle-tissue damage (creatine kinase, CK) marker and delayed onset muscle soreness (DOMS) following eccentric exercise. Seventeen oral contraceptive (OC) users and ten eumenorrheic (EU) subjects completed a 30-min downhill running bout at approximately 60% VO2max. The OC completed the exercise during the mid-luteal phase (day 22.9 +/- 1.5; high estrogen) while the EU did their exercise in the mid-follicular phase (day 9.6 +/- 4.4; low estrogen) of the menstrual cycle, respectively. The CK activity and DOMS were assessed pre-exercise, immediately post-, 24, 48 and 72 h post-exercise. ANOVA results indicated that there was a significant increase in CK activity in response to the downhill run (p < 0.001), and the interaction of group x time was significantly different (p < 0.01). The OC group had lower CK at 72 h post-exercise than did the EU group. Pre-exercise estrogen levels correlated with the overall mean CK (r = -0.43, p < 0.05) and 72 h (r = -0.38, p < 0.05) responses, respectively. Exercise caused an increase in DOMS in both groups (p < 0.001); but, no significant interaction was observed. These findings suggest that elevated estrogen levels have a protective effect on muscle tissue following eccentric exercise. The mechanism of this protective effect is unclear but may be related to the anti-oxidant characteristics and membrane stability properties associated with estrogen and its derivatives.