Mechanisms of exercise-induced muscle fibre injury

Muscle damage and repeated bout effect following blood flow restricted exercise

PURPOSE

Blood-flow restricted resistance exercise training (BFRE) is suggested to be effective in rehabilitation training, but more knowledge is required about its potential muscle damaging effects. Therefore, we investigated muscle-damaging effects of BFRE performed to failure and possible protective effects of previous bouts of BFRE or maximal eccentric exercise (ECC).

METHODS

Seventeen healthy young men were allocated into two groups completing two exercise bouts separated by 14 days. One group performed BFRE in both exercise bouts (BB). The other group performed ECC in the first and BFRE in the second bout. BFRE was performed to failure. Indicators of muscle damage were evaluated before and after exercise.

RESULTS

The first bout in the BB group led to decrements in maximum isometric torque, and increases in muscle soreness, muscle water retention, and serum muscle protein concentrations after exercise. These changes were comparable in magnitude and time course to what was observed after first bout ECC. An attenuated response was observed in the repeated exercise bout in both groups.

CONCLUSION

We conclude that unaccustomed single-bout BFRE performed to failure induces significant muscle damage. Additionally, both ECC and BFRE can precondition against muscle damage induced by a subsequent bout of BFRE.

Effects of traditional Thai self-massage using a Wilai massage stick(TM) versus ibuprofen in patients with upper back pain associated with myofascial trigger points: a randomized controlled trial

[Purpose] The aim of this study was to examine the effects of traditional Thai self-massage using a Wilai massage stick^TM versus ibuprofen on reducing upper back pain associated with myofascial trigger points. [Subjects and Methods] Sixty patients who were diagnosed as having upper back pain associated with myofascial trigger points were randomly allocated to either a massage group using a Wilai massage stick^TM or a medication group taking ibuprofen for 5 days. Both groups were advised to perform the same daily stretching exercise program. Pain intensity, pressure pain threshold, tissue hardness, and cervical range of motion were assessed at baseline, immediately after the first treatment session, and on the fifth day after the last treatment session. [Results] The massage group had significant improvement in all parameters at all assessment time points. Similar changes were observed in the medication group except for the pressure pain threshold and tissue hardness. The adjusted post-test mean values for each assessment time point were significantly better in the massage group than in the medication group. [Conclusion] Tradition Thai self-massage using a Wilai massage stick^TM provides better results than taking ibuprofen for patients who have upper back pain associated with myofascial trigger points. It could be an alternative treatment for this patient population.

Whole-Body Vibration While Squatting and Delayed-Onset Muscle Soreness in Women

CONTEXT

Research into alleviating muscle pain and symptoms in individuals after delayed-onset muscle soreness (DOMS) has been inconsistent and unsuccessful in demonstrating a useful recovery modality.

OBJECTIVE

To investigate the effects of short-term whole-body vibration (WBV) on DOMS over a 72-hour period after a high-intensity exercise protocol.

DESIGN

Randomized controlled clinical trial.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty women volunteered to participate in 4 testing sessions and were assigned randomly to a WBV group (n = 16; age = 21.0 ± 1.9 years, height = 164.86 ± 6.73 cm, mass = 58.58 ± 9.32 kg) or a control group (n = 14; age = 22.00 ± 1.97 years, height = 166.65 ± 8.04 cm, mass = 58.69 ± 12.92 kg).

INTERVENTION(S)

Participants performed 4 sets to failure of single-legged split squats with 40% of their body weight to induce muscle soreness in the quadriceps. The WBV or control treatment was administered each day after DOMS.

MAIN OUTCOME MEASURE(S)

Unilateral pressure-pain threshold (PPT), range of motion (ROM), thigh circumference, and muscle-pain ratings of the quadriceps were collected before and for 3 days after high-intensity exercise. Each day, we collected 3 sets of measures, consisting of 1 measure before the WBV or control treatment protocol (pretreatment) and 2 sets of posttreatment measures.

RESULTS

We observed no interactions for PPT, thigh circumference, and muscle pain (P > .05). An interaction was found for active ROM (P = .01), with the baseline pretreatment measure greater than the measures at baseline posttreatment 1 through 48 hours posttreatment 2 in the WBV group. For PPT, a main effect for time was revealed (P < .05), with the measure at baseline pretreatment greater than at 24 hours pretreatment and all other time points for the vastus medialis, greater than 24 hours pretreatment through 48 hours posttreatment 2 for the vastus lateralis, and greater than 24 hours pretreatment and 48 hours pretreatment for the rectus femoris. For dynamic muscle pain, we observed a main effect for time (P < .001), with the baseline pretreatment measure less than the measures at all other time points. No main effect for time was noted for thigh circumference (P = .24). No main effect for group was found for any variable (P > .05).

CONCLUSIONS

The WBV treatment approach studied did not aid in alleviating DOMS after high-intensity exercise. Further research is needed in various populations.

Job characteristics and musculoskeletal pain among shift workers of a poultry processing plant in Southern Brazil

OBJECTIVES

The purpose of this study was to evaluate the association between job characteristics and musculoskeletal pain among shift workers employed at a 24-hour poultry processing plant in Southern Brazil.

METHODS

This was a cross-sectional study of 1,103 production line workers aged 18-52 years. The job characteristics of interest were shift (day/night), shift duration, and plant sector ambient temperature. Musculoskeletal pain was defined as self-reported occupational-related pain in the upper or lower extremities and trunk, occurring often or always, during the last 12 months.

RESULTS

The mean (SD) participant age was 30.8 (8.5) years, and 65.7% of participants were women. The prevalence of musculoskeletal pain was greater among female participants than male participants. After adjustment for job characteristics and potential confounders, the prevalence ratios (PR) of lower extremity musculoskeletal pain among female workers employed in extreme-temperature conditions those working the night shift, and those who had been working longer on the same shift were 1.75 (95% CI 1.12, 2.71), 1.69 (95% CI 1.05, 2.70), and 1.64 (95% CI 1.03, 2.62), respectively. In male workers, only extreme-temperature conditions showed a significant association with lower extremity musculoskeletal pain (PR=2.17; 95% CI 1.12, 4.22) after adjustment analysis.

CONCLUSIONS

These findings suggest a need for implementation of measures to mitigate the damage caused by nighttime work and by working under extreme temperature conditions, especially among female shift workers, such as changing positions frequently during work and implementation of rest breaks and a workplace exercise program, so as to improve worker quality of life.

The repeated bout effect of typical lower body strength training sessions on sub-maximal running performance and hormonal response

PURPOSE

This study examined the effects of two typical strength training sessions performed 1 week apart (i.e. repeated bout effect) on sub-maximal running performance and hormonal.

METHODS

Fourteen resistance-untrained men (age 24.0 ± 3.9 years; height 1.83 ± 0.11 m; body mass 77.4 ± 14.0 kg; VOpeak 48.1 ± 6.1 M kg(-1) min(-1)) undertook two bouts of high-intensity strength training sessions (i.e. six-repetition maximum). Creatine kinase (CK), delayed-onset muscle soreness (DOMS), counter-movement jump (CMJ) as well as concentrations of serum testosterone, cortisol and testosterone/cortisol ratio (T/C) were examined prior to and immediately post, 24 (T24) and 48 (T48) h post each strength training bout. Sub-maximal running performance was also conducted at T24 and T48 of each bout.

RESULTS

When measures were compared between bouts at T48, the degree of elevation in CK (-58.4 ± 55.6 %) and DOMS (-31.43 ± 42.9 %) and acute reduction in CMJ measures (4.1 ± 5.4 %) were attenuated (p < 0.05) following the second bout. Cortisol was increased until T24 (p < 0.05) although there were no differences between bouts and no differences were found for testosterone and T/C ratio (p > 0.05). Sub-maximal running performance was impaired until T24, although changes were not attenuated following the second bout.

CONCLUSIONS

The initial bout appeared to provide protection against a number of muscle damage indicators suggesting a greater need for recovery following the initial session of typical lower body resistance exercises in resistance-untrained men although sub-maximal running should be avoided following the first two sessions.

Benefits of dietary phytochemical supplementation on eccentric exercise-induced muscle damage: Is including antioxidants enough?

The purpose of this review was to critically discuss studies that investigated the effects of supplementation with dietary antioxidant phytochemicals on recovery from eccentric exercise-induced muscle damage. The performance of physical activities that involve unaccustomed eccentric muscle actions-such as lowering a weight or downhill walking-can result in muscle damage, oxidative stress, and inflammation. These events may be accompanied by muscle weakness and delayed-onset muscle soreness. According to the current evidences, supplementation with dietary antioxidant phytochemicals appears to have the potential to attenuate symptoms associated with eccentric exercise-induced muscle damage. However, there are inconsistencies regarding the relationship between muscle damage and blood markers of oxidative stress and inflammation. Furthermore, the effectiveness of strategies appear to depend on a number of aspects inherent to phytochemical compounds as well as its food matrix. Methodological issues also may interfere with the proper interpretation of supplementation effects. Thus, the study may contribute to updating professionals involved in sport nutrition as well as highlighting the interest of scientists in new perspectives that can widen dietary strategies applied to training.

An examination of the strength and electromyographic responses after concentric vs. eccentric exercise of the forearm flexors

The purpose of this study was to examine the strength and electromyographic (EMG) responses in exercised and nonexercised limbs after concentric (CON) vs. eccentric (ECC) exercise of the forearm flexors. Twenty-five men (mean ± SD age, 23.6 ± 3.8 years; height, 179.7 ± 6.6 cm; body weight, 87.4 ± 14.6 kg) performed 6 sets of 10 maximal CON isokinetic (CON exercise) or ECC isokinetic (ECC exercise) muscle actions of the dominant (DOM) forearm flexors on 2 separate randomly ordered visits. Each subject performed isometric maximal voluntary contractions (MVCs) of both the DOM and nondominant (NONDOM) forearm flexors before (PRE) and immediately after (POST) the exercise interventions. The DOM limb was the only limb exercised for both interventions. A bipolar EMG signal was detected from the biceps brachii during each MVC. The results showed that there were significant 17 and 21% decreases in maximal strength after the CON exercise and ECC exercise, respectively. When collapsed across exercise conditions, strength for the DOM and NONDOM limbs significantly decreased 36 and 4% after exercise, respectively. Accompanied with the strength losses, normalized EMG amplitude for the DOM and NONDOM limbs also reduced 21 and 7%, respectively. These findings suggested that the CON exercise and ECC exercise interventions caused similar strength losses for the exercised arm. There was also a strength loss in the contralateral nonexercised arm that was likely because of neural factors.

Cellular mechanism of eccentric-induced muscle injury and its relationship with sarcomere heterogeneity

Activity-induced muscle injury and dysfunction have been identified as key components of musculoskeletal injuries. These injuries often occur following eccentric contractions, when the muscle is under tension and stretched by a force that is greater than the force generated by the muscle. Many daily activities require muscles to perform eccentric contractions, including walking (or running) downhill or down stairs, lowering heavy objects, and landing from a jump. Injuries often occur when these activities are performed at high intensity or for prolonged periods of time. General features of eccentric-induced muscle injury are well documented and include disruption of intracellular muscle structure, prolonged muscle weakness and dysfunction, a delayed-onset muscle soreness, and inflammation. Several weeks are required for the affected tissue to fully regenerate and recover from eccentric-induced muscle injury. Possible mechanisms responsible for eccentric-induced muscle injury are activation impairment and structural disruption of the sarcomere. These two factors seem to be the main sources of eccentric-induced muscle injury. Rather than being separate mechanisms they may be complimentary and interact with each other. Therefore, in this review we will focus on the two main cellular mechanism of muscle cell injury following accustomed eccentric contraction.

In vivo calcium regulation in diabetic skeletal muscle

In skeletal muscle, dysfunctional contractile activity has been linked to impaired intracellular Ca(2+) concentration ([Ca(2+)]i) regulation. Muscle force production is impaired and fatigability and muscle fragility deteriorate with diabetes. Use of a novel in vivo model permits investigation of [Ca(2+)]i homeostasis in diabetic skeletal muscle. Within this in vivo environment we have shown that diabetes perturbs the Ca(2+) regulatory system such that resting [Ca(2+)]i homeostasis following muscle contractions is compromised and elevations of [Ca(2+)]i are exacerbated. This review considers the impact of diabetes on the capacity of skeletal muscle to regulate [Ca(2+)]i, following muscle contractions and, in particular, the relationship between muscle fatigue and elevated [Ca(2+)]i in a highly ecologically relevant circulation-intact environment. Importantly, the role of mitochondria in calcium sequestration and the possibility that diabetes impacts this process is explored. Given the profound microcirculatory dysfunction in diabetes this preparation offers the unique opportunity to study the interrelationships among microvascular function, blood-myocyte oxygen flux and [Ca(2+)]i as they relate to enhanced muscle fatigability and exercise intolerance.

Effects of downhill and uphill exercises of equivalent submaximal intensities on selected blood cytokine levels and blood creatine kinase activity

The study was aimed at comparing the effects of concentric (CONC) and eccentric (ECC) exercises of equivalent (in terms of relative work load expressed as a percentage of VO2max) moderate intensity on selected blood cytokine levels and blood creatine kinase (CK) activity. Twenty recreationally active healthy young male volunteers were randomized between two groups that performed a single 1 h bout of CONC (uphill running) or ECC (downhill running) exercise at 60% of the respective individual VO2max. Venous blood taken 1 h before, at the end, and 24 h after the exercise was processed for plasma and analyzed for CK activity and IL-6, IL-1β and TNFα levels. There was no between-group difference in these cytokines prior to or just after the exercise, and in pre-exercise CK activity. The cytokines elevated significantly and similarly in both groups during the exercise, with no significant change in CK activity. Twenty-four hours later, CK activity and IL-6 were at pre-exercise levels in the CONC group, but showed further major increases in the ECC group, resulting in marked between-group differences in these indices. Changes in IL-1β and TNFα levels during the recovery period showed only minor differences between the study groups and produced no significant between-group difference in these cytokines. However, IL-1β level normalized in the ECC but not in the CONC group. The study suggests that moderate intensity ECC exercise compared to CONC exercise of equivalent relative work load results in considerably greater muscle damage and its related elevation in circulating IL-6, but it does not cause a major systemic inflammatory response.

L-arginine supplementation protects exercise performance and structural integrity of muscle fibers after a single bout of eccentric exercise in rats

Eccentric exercise is known to disrupt sarcolemmal integrity and induce damage of skeletal muscle fibers. We hypothesized that L-arginine (L-Arg; nitric oxide synthase (NOS) substrate) supplementation prior to a single bout of eccentric exercise would diminish exercise-induced damage. In addition, we used N-nitro-L-arginine methyl ester hydrochloride (L-NAME; NOS inhibitor) to clarify the role of native NOS activity in the development of exercise-induced muscle damage. Rats were divided into four groups: non-treated control (C), downhill running with (RA) or without (R) L-Arg supplementation and downhill running with L-NAME supplementation (RN). Twenty four hours following eccentric exercise seven rats in each group were sacrificed and soleus muscles were dissected and frozen for further analysis. The remaining seven rats in each group were subjected to the exercise performance test. Our experiments showed that L-Arg supplementation prior to a single bout of eccentric exercise improved subsequent exercise performance capacity tests in RA rats when compared with R, RN and C rats by 37%, 27% and 13%, respectively. This outcome is mediated by L-Arg protection against post-exercise damage of sarcolemma (2.26- and 0.87-fold less than R and RN groups, respectively), reduced numbers of damaged muscle fibers indicated by the reduced loss of desmin content in the muscle (15% and 25% less than R and RN groups, respectively), and diminished µ-calpain mRNA up-regulation (42% and 30% less than R and RN groups, respectively). In conclusion, our study indicates that L-Arg supplementation prior to a single bout of eccentric exercise alleviates muscle fiber damage and preserves exercise performance capacity.

Effect of wearing compression stockings on recovery after mild exercise-induced muscle damage

BACKGROUND

Compression garments are increasingly popular in long-distance running events where they are used to limit cumulative fatigue and symptoms associated with mild exercise-induced muscle damage (EIMD). However, the effective benefits remain unclear.

OBJECTIVE

This study examined the effect of wearing compression stockings (CS) on EIMD indicators. Compression was applied during or after simulated trail races performed at competition pace in experienced off-road runners.

METHODS

Eleven highly trained male runners participated in 3 simulated trail races (15.6 km: uphill section 6.6 km, average gradient 13%, and downhill section 9.0 km, average gradient -9%) in a randomized crossover trial. The effect of wearing CS while running or during recovery was tested and compared with a control condition (ie, run and recovery without CS; non- CS). Indicators of muscle function, muscle damage (creatine kinase; CK), inflammation (interleukin-6; IL-6), and perceived muscle soreness were recorded at baseline (1 h before warm-up) and 1, 24, and 48 h after the run.

RESULTS

Perceived muscle soreness was likely to be lower when participants wore CS during trail running compared with the control condition (1 h postrun, 82% chance; 24 h postrun, 80% chance). A likely or possibly beneficial effect of wearing CS during running was also found for isometric peak torque at 1 h postrun (70% chance) and 24 h postrun (60% chance) and throughout the recovery period on countermovement jump, compared with non-CS. Possible, trivial, or unclear differences were observed for CK and IL-6 between all conditions.

CONCLUSION

Wearing CS during simulated trail races mainly affects perceived leg soreness and muscle function. These benefits are visible very shortly after the start of the recovery period.

Role of oxidative stress in impaired insulin signaling associated with exercise-induced muscle damage

Skeletal muscle is a major tissue that utilizes blood glucose. A single bout of exercise improves glucose uptake in skeletal muscle through insulin-dependent and insulin-independent signal transduction mechanisms. However, glucose utilization is decreased in muscle damage induced by acute, unaccustomed, or eccentric exercise. The decrease in glucose utilization is caused by decreased insulin-stimulated glucose uptake in damaged muscles with inhibition of the membrane translocation of glucose transporter 4 through phosphatidyl 3-kinase/Akt signaling. In addition to inflammatory cytokines, reactive oxygen species including 4-hydroxy-2-nonenal and peroxynitrate can induce degradation or inactivation of signaling proteins through posttranslational modification, thereby resulting in a disturbance in insulin signal transduction. In contrast, treatment with factors that attenuate oxidative stress in damaged muscle suppresses the impairment of insulin sensitivity. Muscle-damaging exercise may thus lead to decreased endurance capacity and muscle fatigue in exercise, and it may decrease the efficiency of exercise therapy for metabolic improvement.

Aging, functional capacity and eccentric exercise training

Aging is a multi-factorial process that ultimately induces a decline in our physiological functioning, causing a decreased health-span, quality of life and independence for older adults. Exercise participation is seen as a way to reduce the impact of aging through maintenance of physiological parameters. Eccentric exercise is a model that can be employed with older adults, due to the muscle's ability to combine high muscle force production with a low energy cost. There may however be a risk of muscle damage before the muscle is able to adapt. The first part of this review describes the process of aging and how it reduces aerobic capacity, muscle strength and therefore functional mobility. The second part highlights eccentric exercise and the associated muscle damage, in addition to the repeated bout effect. The final section reviews eccentric exercise interventions that have been completed by older adults with a focus on the changes in functional mobility. In conclusion, eccentric endurance exercise is a potential training modality that can be applied to older adults for improving muscle strength, aerobic capacity and functional ability. However, further research is needed to assess the effects on aerobic capacity and the ideal prescription for eccentric endurance exercise.

Effects of taurine supplementation following eccentric exercise in young adults

The purpose of the present study was to investigate the effects of taurine supplementation on muscle performance, oxidative stress, and inflammation response after eccentric exercise (EE) in males. Twenty-one participants (mean age, 21 ± 6 years; weight, 78.2 ± 5 kg; height, 176 ± 7 cm) were selected and randomly divided into two groups: placebo (n = 10) and taurine (n = 11). Fourteen days after starting supplementation, subjects performed EE (3 sets until exhaustion, with EE of the elbow flexors on the Scott bench, 80% 1 repetition maximum (RM)). Blood samples were collected and muscle performance was measured on days 1, 14, 16, 18, and 21 after starting the supplements. Then, performance, muscle damage, oxidative stress, and inflammatory markers were analyzed. The taurine supplementation resulted in increased strength levels and thiol total content and decreased muscle soreness, lactate dehydrogenase level, creatine kinase activity, and oxidative damage (xylenol and protein carbonyl). Antioxidant enzymes (superoxide dismutase, catalase, and gluthatione peroxidase) and inflammatory markers (tumor necrosis factor, interleukin-1β (IL-1β), and interleukin-10 (IL-10)) were not altered during the recovery period compared with the placebo group. The results suggest that taurine supplementation represents an important factor in improving performance and decreasing muscle damage and oxidative stress but does not decrease the inflammatory response after EE.

Expression pattern of potential biomarker genes related to growth, ion regulation and stress in response to ammonia exposure, food deprivation and exercise in common carp (Cyprinus carpio)

Waterborne ammonia has become a persistent pollutant of aquatic habitats. During certain periods (e.g. winter), food deprivation may occur simultaneously in natural water. Additionally, under such stressful circumstances, fish may be enforced to swim at a high speed in order to catch prey, avoid predators and so on. Consequently, fish need to cope with all these stressors by altering physiological processes which in turn are controlled by their genes. In this present study, toxicogenomic analyses using real time PCR was used to characterize expression patterns of potential biomarker genes controlling growth, ion regulation and stress responses in common carp subjected to elevated ammonia (1 mg/L; Flemish water quality guideline for surface water) following periods of feeding (2% body weight) and fasting (unfed for 7 days prior to sampling). Both feeding groups of fish were exposed to high environment ammonia (HEA) for 0 h (control), 3h, 12h, 1 day, 4 days, 10 days, 21 days and 28 days, and were sampled after performing swimming at different speeds (routine versus exhaustive). Results show that the activity and expression of Na(+)/K(+)-ATPase, an important branchial ion regulatory enzyme, was increased after 4-10 days of exposure. Effect of HEA was also evident on expression patterns of other ion-regulatory hormone and receptor genes; prolactin and cortisol receptor mRNA level(s) were down-regulated and up-regulated respectively after 4, 10 and 21 days. Starvation and exhaustive swimming, the additional challenges in present study significantly further enhanced the HEA effect on the expression of these two genes. mRNA transcript of growth regulating hormone and receptor genes such as Insulin-like growth factor I, growth hormone receptor, and the thyroid hormone receptor were reduced in response to HEA and the effect of ammonia was exacerbated in starved fish, with levels that were remarkably reduced compared to fed exposed fish. However, the expression of the growth hormone gene itself was up-regulated under the same conditions. Expression of somatolactin remained unaltered. Stress representative genes, cytochrome oxidase subunit 1 showed an up-regulation in response to HEA and starvation while the mRNA level of heat shock protein 70 was increased in response to all the three stressors. The expression kinetics of the studied genes could permit to develop a "molecular biomarker system" to identify the underlying physiological processes and impact of these stressors before effects at population level occur.

Effects of repetitive lifting on kinematics: inadequate anticipatory control or adaptive changes?

In the present study, the effects of repetition on the kinematics in discrete lifting were studied in 10 subjects who lifted a barbell weighing 10% of body mass at a determined speed and along a determined trajectory 630 times during about 40 min. Three-dimensional (3-D) kinematics of the feet, lower and upper legs, pelvis, and trunk were recorded in the first 3 and the final 3 lifting movements of each set of 70 lifts. Over time, trunk extension velocity in the initial 250 ms of the lifting movement decreased, reaching negative (increasing flexion) values in most subjects. In contrast, hip extension velocity increased. Those changes resulted in an increased phase lag between hip and trunk extension. Also, over time, subjects started the lifting movement with their legs more extended and their trunks further flexed. Finally, the motion of the trunk around its longitudinal axis (twisting) increased. The increase in phase lag between hip and trunk extension is interpreted as a consequence of fatigue-more specifically, as the result of a decreased rate of force development of the back muscles. The change in initial posture more likely is an adaptation that functions to retard further fatigue development.

Cytokine and satellite cell responses to muscle damage: interpretation and possible confounding factors in human studies

It is plausible that multiple muscle biopsies following a muscle damaging intervention can exacerbate the inflammatory and subsequent satellite cell responses. To elucidate confounding effects of muscle biopsy procedure on satellite cell number, indirect markers of damage and the inflammatory response following acute downhill running (DHR) were investigated. 10 healthy male participant were divided into a non-exercising control (n = 4) and DHR (12 × 5min bouts, 10 % decline at 85 % VO(2)max) (n = 6) group. Blood samples were taken pre, post and every 24 h for 9 days. Serum was analysed for creatine kinase (CK), myoglobin (Mb), lactate dehydrogenase (LDH), TNF-α, IL-6 and IL-10. Muscle biopsies taken on days 1 and 2 post intervention from opposing legs were analysed for Pax7(+) satellite cells. In the DHR group, Mb (536 ± 277 ng mL(-1)), IL-6 (12.6 ± 4.7 pg mL(-1)) and IL-10 (27.3 ± 11.5 pg mL(-1)) peaked immediately post DHR, while CK (2651 ± 1911 U L(-1)), LDH (202 ± 47 U L(-1)) and TNF-α (25.1 ± 8.7 pg mL(-1)) peaked on day 1. A 30 % increase in Pax7(+) satellite cells on day 1 in the DHR group was no longer apparent on day 2. H&E staining show evidence of phagocytosis in the DHR group. No significant changes over time were observed in the control group for any of the variables measured. Events observed in the DHR group were as a result of the intervention protocol and subsequent muscle damage. The relationship between SC proliferation and pro-inflammatory cytokine release appears to be complex since the IL-6/IL-10 response time differs significantly from the TNF-α response.

Supplementation of Acqua Lete® (Bicarbonate Calcic Mineral Water) improves hydration status in athletes after short term anaerobic exercise

BACKGROUND

Experimental studies suggest that mineral waters with high concentrations of calcium and bicarbonate can impact acid-base balance. The purpose of this study was to test the effect on acid-base balance and specific urine gravity, of a bicarbonate calcic mineral water (Acqua Lete®) compared to a minimally mineralized water.

METHODS

88 amateur male athletes underwent two experimental trials with a modified Wingate test: the first was carried out without hydration (Control Test, Test C, n = 88); the second was carried out after one week of controlled hydration (Test with hydration, Test H, n = 88), with 1.5 L/day of a very low mineral content water (Group A, n = 44) or 1.5 L/day of Acqua Lete® (Group B, n = 44). Measure of body temperature, bioimpedance analysis, muscular ultrasound, and urinalysis were taken before (t0), immediately after (t1), 5' (t2), and 30' (t3) after exercise.

RESULTS

Hydration results in a decreased core temperature; muscular ultrasound showed increased muscle thickness after exercise related to content of body water. Regarding urinalysis, in test H, we found in both groups after exercise a significant decrease of specific urine gravity with significantly lower levels in Group B. We also found a significant increase of pH in the same Group B.

CONCLUSIONS

In conclusion all the athletes hydrated with Acqua Lete® showed a positive impact on hydration status after anaerobic exercise with significant decrease of specific urine gravity and a positive effect on pH.

Power loss is greater following lengthening contractions in old versus young women

Compared with isometric and dynamic velocity-constrained (isokinetic) tasks, less is known regarding velocity-dependent (isotonic) muscle power and recovery in older adults following repeated fatiguing lengthening contractions. We investigated voluntary and evoked neuromuscular properties of the dorsiflexors in nine old (68.3 ± 6.1 years) and nine young women (25.1 ± 1.3 years) during and following 150 lengthening contractions for up to 30 min of recovery. At baseline, the old were ~21% weaker for maximum isometric voluntary contraction (MVC) torque (P < 0.05), ~21% slower for peak loaded shortening velocity (P < 0.05), and ~39% less powerful compared with the young (P < 0.05). Following the task, MVC torque was depressed equally (~28%) for both groups (P < 0.05), but power was reduced ~19% in the old and only ~8% in the young (P < 0.05). Both measures remained depressed during the 30-min recovery period. Peak twitch torque (P (t)) was ~50% lower in the old at task termination, whereas the young were unchanged. However, by 5 min of recovery, P (t) was reduced similarly (~50%) in both groups, and neither recovered by 30 min. The old were affected more by low-frequency torque depression than the young, as shown by the ~40% and ~20% decreases in the stimulated 10:50 Hz ratio at task termination respectively, whereas both groups were affected similarly (~50%) 5 min into recovery, and neither recovered by 30 min. Thus, the coexistence of fatigue and muscle damage induced by the repetitive lengthening contractions impaired excitation-contraction coupling and cross-bridge function to a greater extent in the old, leading to a more pronounced initial loss of power than the young for up to 10 min following the exercise However, power remained blunted in both groups during the 30-min recovery period. These results indicate that older women are more susceptible to power loss than young following lengthening contractions, likely owing to a greater impairment in calcium kinetics.

Cytokines in muscle damage

Multiple cellular and molecular processes are rapidly activated following skeletal muscle damage to restore normal muscle structure and function. These processes typically involve an inflammatory response and potentially the consequent occurrence of secondary damage before their resolution and the completion of muscle repair or regeneration. The overall outcome of the inflammatory process is potentially divergent, with the induction of prolonged inflammation and further muscle damage, or its active termination and the promotion of muscle repair and regeneration. The final, detrimental, or beneficial effect of the inflammatory response on muscle repair is influenced by specific interactions between inflammatory and muscle cell-derived cytokines that act as positive and/or negative regulators to coordinate local and systemic inflammatory-related events and modulate muscle repair process. A crucial balance between proinflammatory and anti-inflammatory cytokines appears to attenuate an excessive inflammatory reaction, prevent the development of muscle fibrosis, and adequately promote the regenerative process. In this review, we address the interactive cytokine responses following muscle damage, in the context of induction and progression, or resolution of muscle inflammation and the promotion of muscle repair.

IB4-saporin attenuates acute and eliminates chronic muscle pain in the rat

The function of populations of nociceptors in muscle pain syndromes remain poorly understood. We compared the contribution of two major classes, isolectin B4-positive (IB4(+)) and IB4-negative (IB4(-)) nociceptors, in acute and chronic inflammatory and ergonomic muscle pain. Baseline mechanical nociceptive threshold was assessed in the gastrocnemius muscle of rats treated with IB4-saporin, which selectively destroys IB4(+) nociceptors. Rats were then submitted to models of acute inflammatory (intramuscular carrageenan)- or ergonomic intervention (eccentric exercise or vibration)-induced muscle pain, and each of the three models also evaluated for the transition from acute to chronic pain, manifest as prolongation of prostaglandin E2 (PGE(2))-induced hyperalgesia, after recovery from the hyperalgesia induced by acute inflammation or ergonomic interventions. IB4-saporin treatment did not affect baseline mechanical nociceptive threshold. However, compared to controls, IB4-saporin treated rats exhibited shorter duration mechanical hyperalgesia in all three models and attenuated peak hyperalgesia in the ergonomic pain models. And, IB4-saporin treatment completely prevented prolongation of PGE(2)-induced mechanical hyperalgesia. Thus, IB4(+) and IB4(-) neurons contribute to acute muscle hyperalgesia induced by diverse insults. However, only IB4+ nociceptors participate in the long term consequence of acute hyperalgesia.

Meloxicam-induced rhabdomyolysis in the context of an acute ross river viral infection

Acute rhabdomyolysis is a clinical and laboratory syndrome resulting from the breakdown of skeletal muscle, with the release of intracellular contents into the circulatory system, which can cause potentially lethal complications. Here, we present the case of a patient who developed acute rhabdomyolysis after consumption of meloxicam for jaw pain and experienced generalized myalgias in the context of an acute febrile illness with generalized urticaria. Further investigation indicated elevated muscle enzymes and acute renal failure. Serological analysis revealed that the patient was positive for Ross River virus (RRV) IgM. Genetic studies to detect CYP2C9 polymorphisms were negative. Meloxicam was discontinued. He responded to conservative measures within 2 weeks. Oral aspirin challenge was negative, suggesting a drug-specific effect of meloxicam rather than a class effect. Our case indicates a causative role for meloxicam and/or acute RRV in rhabdomyolysis.

The effect of graduated compression stockings on running performance

The aim of this study was to examine the effects of wearing different grades of graduated compression stockings (GCS) on 10-km running performance. After an initial familiarization run, 9 male and 3 female competitive runners (VO₂max 68.7 ± 5.8 ml·kg⁻¹·min⁻¹) completed 4 10-km time trials on an outdoor 400-m track wearing either control (0 mm Hg; Con), low (12-15 mm Hg; Low), medium (18-21 mm Hg; Med), or high (23-32 mm Hg; Hi) GCS in a randomized counterbalanced order. Leg power was assessed pre and postrun via countermovement jump using a jump mat. Blood-lactate concentration was assessed pre and postrun, whereas heart rate was monitored continuously during exercise. Perceptual scales were used to assess the comfort, tightness, and any pain associated with wearing GCS. There were no significant differences in performance time between trials (p = 0.99). The change in pre to postexercise jump performance was lower in Low and Med than in Con (p < 0.05). Mean heart rate (p = 0.99) and blood lactate (p = 1.00) were not different between trials. Participants rated Con and Low as more comfortable than Med and Hi (p < 0.01), Med and Hi were rated as tighter than Low (p < 0.01), all GCS were rated as tighter than Con (p < 0.01), and Hi was associated with the most pain (p < 0.01). In conclusion, GCS worn by competitive runners during 10-km time trials did not affect performance time; however Low and Med GCS resulted in greater maintenance of leg power after endurance exercise. Athletes rated low-grade GCS as most comfortable garments to wear during exercise.

N-acetylcysteine supplementation controls total antioxidant capacity, creatine kinase, lactate, and tumor necrotic factor-alpha against oxidative stress induced by graded exercise in sedentary men

Aim of this study was to evaluate the effects of short-term (7 days) N-acetylcysteine (NAC) at 1,200 mg daily supplementation on muscle fatigue, maximal oxygen uptake (VO_2max), total antioxidant capacity (TAC), lactate, creatine kinase (CK), and tumor necrotic factor-alpha (TNF-α). Twenty-nine sedentary men (13 controls; 16 in the supplement group) from a randomized control were included. At before and after supplementation, fatigue index (FI) was evaluated in the quadriceps muscle, and performed a graded exercise treadmill test to induce oxidative stress, and as a measure of VO_2max. Blood samples were taken before exercise and 20 minutes after it at before and after supplementation, to determine TAC, CK, lactate, and TNF-α levels. Results showed that FI and VO_2max increased significantly in the supplement group. After exercise decreased the levels of TAC and increased lactate, CK, and TNF-α of both groups at before supplementation. After supplementation, lactate, CK, and TNF-α levels significantly increased and TAC decreased after exercise in the control group. Whereas the TAC and lactate levels did not change significantly, but CK and TNF-α increased significantly in the supplement group. Therefore, this results showed that NAC improved the muscle fatigue, VO_2max, maintained TAC, controlled lactate production, but had no influence on CK and TNF-α.

Whole-body vibration and the prevention and treatment of delayed-onset muscle soreness

CONTEXT

Numerous recovery strategies have been used in an attempt to minimize the symptoms of delayed-onset muscle soreness (DOMS). Whole-body vibration (WBV) has been suggested as a viable warm-up for athletes. However, scientific evidence to support the protective effects of WBV training (WBVT) on muscle damage is lacking.

OBJECTIVE

To investigate the acute effect of WBVT applied before eccentric exercise in the prevention of DOMS.

DESIGN

Randomized controlled trial.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 32 healthy, untrained volunteers were randomly assigned to either the WBVT (n  =  15) or control (n  =  17) group.

INTERVENTION(S)

Volunteers performed 6 sets of 10 maximal isokinetic (60°/s) eccentric contractions of the dominant-limb knee extensors on a dynamometer. In the WBVT group, the training was applied using a vibratory platform (35 Hz, 5 mm peak to peak) with 100° of knee flexion for 60 seconds before eccentric exercise. No vibration was applied in the control group.

MAIN OUTCOME MEASURE(S)

Muscle soreness, thigh circumference, and pressure pain threshold were recorded at baseline and at 1, 2, 3, 4, 7, and 14 days postexercise. Maximal voluntary isometric and isokinetic knee extensor strength were assessed at baseline, immediately after exercise, and at 1, 2, 7, and 14 days postexercise. Serum creatine kinase was measured at baseline and at 1, 2, and 7 days postexercise.

RESULTS

The WBVT group showed a reduction in DOMS symptoms in the form of less maximal isometric and isokinetic voluntary strength loss, lower creatine kinase levels, and less pressure pain threshold and muscle soreness (P < .05) compared with the control group. However, no effect on thigh circumference was evident (P < .05).

CONCLUSIONS

Administered before eccentric exercise, WBVT may reduce DOMS via muscle function improvement. Further investigation should be undertaken to ascertain the effectiveness of WBVT in attenuating DOMS in athletes.

Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation

Active myofascial trigger points are one of the major peripheral pain generators for regional and generalized musculoskeletal pain conditions. Myofascial trigger points are also the targets for acupuncture and/or dry needling therapies. Recent evidence in the understanding of the pathophysiology of myofascial trigger points supports The Integrated Hypothesis for the trigger point formation; however unanswered questions remain. Current evidence shows that spontaneous electrical activity at myofascial trigger point originates from the extrafusal motor endplate. The spontaneous electrical activity represents focal muscle fiber contraction and/or muscle cramp potentials depending on trigger point sensitivity. Local pain and tenderness at myofascial trigger points are largely due to nociceptor sensitization with a lesser contribution from non-nociceptor sensitization. Nociceptor and non-nociceptor sensitization at myofascial trigger points may be part of the process of muscle ischemia associated with sustained focal muscle contraction and/or muscle cramps. Referred pain is dependent on the sensitivity of myofascial trigger points. Active myofascial trigger points may play an important role in the transition from localized pain to generalized pain conditions via the enhanced central sensitization, decreased descending inhibition and dysfunctional motor control strategy.

Adaptations in biceps brachii motor unit activity after repeated bouts of eccentric exercise in elbow flexor muscles

The purpose of this study was to examine changes in motor unit activity in the biceps brachii muscle after an initial ( Bout 1) and repeated ( Bout 2) session of eccentric exercise separated by 1 wk. Eight subjects (aged 22 ± 2 yr) participated in experimental assessments of neuromuscular function obtained before, immediately after, 24 h after, and 7 days after each exercise bout. Each experimental session involved assessments of elbow-flexor force and biceps and triceps brachii electromyography during maximum voluntary isometric contractions (MVCs) and constant-force isometric contractions at five contraction intensities (5–50% MVC), along with indicators of muscle damage (muscle pain and passive tension). In addition, motor unit recordings were obtained before exercise, 7 days after Bout 1, and 24 h after Bout 2 to assess motor unit synchronization and recruitment thresholds. Following a single eccentric exercise session that elicited significant indicators of muscle damage, we found a 57% increase in motor unit synchronization 7 days later compared with before exercise, despite the recovery of maximal strength, soreness, and relaxed elbow-joint angle at this time. Furthermore, a second bout of the same eccentric exercise resulted in reduced indicators of muscle damage and a decline in the strength of motor unit synchronization (24 h after Bout 2) toward levels observed before both exercise sessions. In contrast, no changes in motor unit recruitment thresholds were observed 7 days after Bout 1 or 24 h after Bout 2 compared with before exercise. The increased motor unit synchronization 7 days after a single eccentric exercise session provides new evidence of changes in motor unit activity during the putative repair and regeneration phase following eccentric muscle damage.

Changes in human skeletal muscle length during stimulated eccentric muscle actions

Following eccentric exercise, increases in muscle length alter the length-tension relation of skeletal muscle. However, its unclear if this change occurs during eccentric exercise. Therefore, 70 eccentric actions of the knee extensors of one leg (with superimposed electrical stimulation) were performed at 100°/s, from full extension to full flexion. Angle-specific eccentric force was recorded throughout. Force decreased at all angles although this was non-uniform. At 70°, force decreased by 25%, whereas at 130°, force decreased by 41%. Initial peak force was recorded at 100° (590 ± 232 N); the exercise bout induced a 21% decrease in peak force and a 10° shift in the position of peak force production to 90°. The rightward shift in the muscle length-tension relation thus occurred during eccentric exercise, where greater force loss at short muscle lengths suggested an eccentric-induced over-stretching of sarcomeres.

Calcium-activated force of human muscle fibers following a standardized eccentric contraction

Peak Ca2+-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component ( r2 = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.

Sex differences in intracellular Ca2+ accumulation following eccentric contractions of rat skeletal muscle in vivo

It is commonly believed that estrogen and sex influences play significant effects in skeletal muscle damage following eccentric exercise. The mechanistic bases for this sex-specific phenomenon remain to be resolved. The muscle damage has been linked to loss of Ca2+ homeostasis and resultant intramyocyte Ca2+ ([Ca2+]i) accumulation; therefore, we tested the hypothesis that the greater eccentric exercise-induced muscle damage in males would be associated with more pronounced [Ca2+]i accumulation. The intact spinotrapezius muscle of adult Wistar rats [male, female, and ovariectomized (OVX)—to investigate the effects of estrogen] was exteriorized. Tetanic eccentric contractions (100 Hz, 700-ms duration, 20 contractions/min for a total of 10 sets of 50 contractions) were elicited by electrical stimulation during synchronized muscle stretch of 10% resting muscle length. The fluorescence ratio (F340/F380 nm) was determined from images captured following each set of contractions, and fura-2 AM was used to estimate [Ca2+]i and changes thereof. Following eccentric contractions, [Ca2+]i increased significantly in male (42.8 ± 5.3%, P < 0.01) but not in female (9.4 ± 3.5%) rats. OVX evidenced an intermediate response (17.0 ± 1.2%) that remained significantly reduced compared with males. These results demonstrate that females maintain [Ca2+]i homeostasis following novel eccentric contractions, whereas males do not, which is consistent with a role for elevated [Ca2+]i in eccentric exercise-induced muscle damage. The presence of normal estrogen levels is not obligatory for the difference between the sexes.

Effect of delayed-onset muscle soreness on muscle recovery after a fatiguing isometric contraction

An increase to above-baseline levels of electromyography (EMG) mean power spectral frequency (MPF) has been observed previously during muscle recovery following fatiguing contractions and has been explained by membrane hyperpolarization due to increased activation of the Na+-K+ pump. It is hypothesized that this membrane mechanism is impaired by muscle fiber damage following eccentric exercise. Thus, the aim of the study was to investigate surface EMG signal characteristics during recovery from fatigue after eccentric exercise. Ten healthy subjects performed sustained isometric knee extensions at 40% of the maximal torque (MVC) until task failure before, immediately after and 24 and 48 h after eccentric exercise. Bipolar surface EMG signals were recorded from six locations over the quadriceps during the sustained isometric contraction and during 3-s long contractions at 40% MVC separated by 1-min intervals for 15 min (recovery). Before the eccentric exercise, MPF of EMG signals increased to values above baseline during recovery from the fatiguing isometric contraction (P<0.001), whereas immediately after and 24 and 48 h after the eccentric task, MPF was lower than baseline during the entire recovery period (P<0.01). In conclusion, delayed-onset muscle soreness abolished the supranormal increase in EMG MPF following recovery from fatigue.

Delayed recovery of velocity-dependent power loss following eccentric actions of the ankle dorsiflexors

Unaccustomed eccentric exercise has been shown to impair muscle function, although little is known regarding this impairment on muscle power. The purpose of this study was to investigate changes in neuromuscular properties of the ankle dorsiflexors during and after an eccentric contraction task and throughout recovery in 21 (10 men, 11 women) recreationally active young adults (25.8+/-2.3 yr). All subjects performed 5 sets of 30 eccentric contractions at 80% of maximum isometric voluntary contraction (MVC) torque. Data were recorded at baseline, during the fatigue task, and for 30 min of recovery. There were no significant sex differences for all fatigue measures; thus data were pooled. After the fatigue task, MVC torque declined by 28% (P<0.05) and did not recover fully, and voluntary activation of the dorsiflexors, as assessed by the interpolated twitch technique, was near maximal (>99%) during and after the fatigue task (P>0.05). Peak twitch torque was reduced by 21% at 2 min of recovery and progressively decreased to 35% by 30 min (P<0.05). Low-frequency torque depression (10-to-50 Hz ratio) was present at 30 s of recovery, increased to 51% by 10 min, and did not recover fully (P<0.05). Velocity-dependent concentric power was reduced by 8% immediately after task termination and did not recover fully within 30 min (P<0.05). The main findings of an incomplete recovery of MVC torque, low-frequency torque depression, and shortening velocity indicate the presence of muscle damage, which may have altered excitation-contraction coupling and cross-bridge kinetics and reduced the number of functional sarcomeres in series, ultimately leading to velocity-dependent power loss.

Effect of milk-based carbohydrate-protein supplement timing on the attenuation of exercise-induced muscle damage

Exercise-induced muscle damage (EIMD) leads to decrements in muscle performance and increases in intramuscular enzymes measured in the plasma, and to delayed onset of muscle soreness (DOMS), partly due to the activation of degradative pathways. It has been shown that milk-based carbohydrate-protein (CHO-P) can limit changes in markers of EIMD, possibly by attenuating protein degradation and (or) increasing protein synthesis. However, the timing of supplementation has received limited attention, and this may alter the response. This study examined the effects of acute milk-based CHO-P supplementation timing on the attenuation of EIMD. Four independent matched groups of 8 healthy males consumed milk-based CHO-P before (PRE), immediately after (POST), or 24 h after (TWENTY-FOUR) muscle-damaging exercise. Active DOMS, isokinetic muscle performance, reactive strength index (RSI), and creatine kinase (CK) were assessed immediately before and 24, 48, and 72 h after EIMD. POST and TWENTY-FOUR demonstrated a benefit in limiting changes in active DOMS, peak torque, and RSI over 48 h, compared with PRE. PRE showed a possible benefit in reducing increases in CK over 48 h and limiting changes in other variables over 72 h. Consuming milk-based CHO-P after muscle-damaging exercise is more beneficial in attenuating decreases in muscle performance and increases in active DOMS at 48 h than ingestion prior to exercise.

Reduced soleus muscle injury at long muscle length during contraction in the rat

Muscle injury was studied to test the hypotheses that maintaining the soleus muscle at a long muscle length during contraction prevents muscle injuries and that the prevention of initial muscle injuries reduces subsequent muscle damage. The rat sciatic nerve was stimulated for 30 min with plantar or dorsal flexion of the foot, and the time course of contraction-induced injuries was examined. The soleus muscle injuries were first classified into one of five types, and the percentages of aberrant sarcomere areas observed in the soleus muscle were then separately quantified by electron microscopy at 0, 1, 6, 12, and 24 h (n = 3) post-stimulation. At a short muscle length (plantar flexion) during contraction, the soleus muscle showed sarcomere hypercontraction (9.8 ± 2.5%, mean ± standard error) and Z-band disarrangement (31.0 ± 4.5%) at 0 h, sarcomere hypercontraction (6.7 ± 1.9%), Z-band disarrangement (28.0 ± 4.9%), and sarcomere hyperstretching (1.3 ± 1.3%) at 1 h, the absence of sarcomere hypercontraction, but Z-band disarrangement (6.7 ± 1.9%) and sarcomere hyperstretching (5.0 ± 1.8%) at 6 h, and myofilament disorganization at 12 and 24 h (5.2 ± 1.5 and 2.5 ± 1.0%, respectively). In contrast, the soleus muscles at a long muscle length (dorsal flexion) during contraction using a self-made brace showed alterations in 1.2-2.4% of sarcomeres at 0 h and afterwards. Desmin disappeared, and α-actinin immunostaining was weaker in areas of sarcomere hypercontraction, whereas dystrophin was always detected along the sarcoplasmic membrane, suggesting that the integrity of the sarcolemma was intact. These results indicate that initial and subsequent muscle injuries were significantly reduced at long muscle length during contraction, probably through the prevention of sarcomere hypercontraction, and that initial muscle injuries rapidly progress to other injuries or normal structure.

Physiological effects of wearing graduated compression stockings during running

This study examined the effect of wearing different grades of graduated compression stockings (GCS) on physiological and perceptual measures during and following treadmill running in competitive runners. Nine males and one female performed three 40-min treadmill runs (80 +/- 5% maximal oxygen uptake) wearing either control (0 mmHg; CON), low (12-15 mmHg; LO-GCS), or high (23-32 mmHg; HI-GCS) grade GCS in a double-blind counterbalanced order. Oxygen uptake, heart rate and blood lactate were measured. Perceptual scales were used pre- and post-run to assess comfort, tightness and any pain associated with wearing GCS. Changes in muscle function, soreness and damage were determined pre-run, immediately after running and 24 and 48 h post-run by measuring creatine kinase and myoglobin, counter-movement jump height, perceived soreness diagrams, and pressure sensitivity. There were no significant differences between trials for oxygen uptake, heart rate or blood lactate during exercise. HI-GCS was perceived as tighter (P < 0.05) and more pain-inducing (P < 0.05) than the other interventions; CON and LO-GCS were rated more comfortable than HI-GCS (P < 0.05). Creatine kinase (P < 0.05), myoglobin (P < 0.05) and jump height (P < 0.05) were higher and pressure sensitivity was more pronounced (P < 0.05) immediately after running but not after 24 and 48 h. Only four participants reported muscle soreness during recovery from running and there were no differences in muscle function between trials. In conclusion, healthy runners wearing GCS did not experience any physiological benefits during or following treadmill running. However, athletes felt more comfortable wearing low-grade GCS whilst running.