Observations on experimental muscular soreness

The repeated bout effect evokes the training-induced skeletal muscle cellular memory

Physical exercise is well-established as beneficial for health. With the 20th-century epidemiological transition, promoting healthy habits like exercise has become crucial for preventing chronic diseases. Stress can yield adaptive long-term benefits, potentially transmitted trans-generationally. Physical training exposes individuals to metabolic, thermal, mechanical, and oxidative stressors, activating cell signaling pathways that regulate gene expression and adaptive responses, thereby enhancing stress tolerance - a phenomenon known as hormesis. Muscle memory is the capacity of skeletal muscle to respond differently to environmental stimuli in an adaptive (positive) or maladaptive (negative) manner if the stimuli have been encountered previously. The Repeated Bout Effect encompasses our skeletal muscle capacity to activate an intrinsic protective mechanism that reacts to eccentric exercise-induced damage by activating an adaptive response that resists subsequent damage stimuli. Deciphering the molecular mechanism of this phenomenon would allow the incorporation of muscle memory in training programs for professional athletes, active individuals looking for the health benefits of exercise training, and patients with "exercise intolerance." Moreover, enhancing the adaptive response of muscle memory could promote healing in individuals who traditionally do not recover after immobilization. The improvement could be part of an exercise program but could also be targeted pharmacologically. This review explores Repeated Bout Effect mechanisms: neural adaptations, tendon and muscle fiber property changes, extracellular matrix remodeling, and improved inflammatory responses.

Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness

We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.

Can Anthocyanins Reduce Delayed Onset Muscle Soreness or Are We Barking Up the Wrong Tree?

Exercise-induced muscular overload can trigger delayed onset muscle soreness (DOMS). DOMS is related to the indiscriminate use of analgesics and nonsteroidal anti-inflammatory drugs without proper guidance, decreased physical exercise adherence and degenerating sports performance, increased risk of injury, and reduced muscle strength and function. Dietary anthocyanins have been extensively studied as potential natural treatments for DOMS, but the indication, dosage, and form of use remain highly variable. Therefore, this review aims to synergize and present evidence relating to the effect of anthocyanins on DOMS in clinical studies. Notably, the results of anthocyanin supplementation for DOMS were found to be inconclusive. The use of protocols with lower anthocyanin doses yielded better results than those with high-dose supplements, suggesting that anthocyanin-rich foods are more accessible as therapeutic tools, leading to the conclusion that these foods could be used to prevent and treat DOMS. However, consumption protocols for this purpose are not yet well established, and the answer is dependent on the methodological quality of future studies.

Muscle activity during low-speed rear impact

PURPOSE

Whiplash associated disorders remain a major health problem in terms of impact on health care and on societal costs. Aetiology remains controversial including the old supposition that the cervical muscles do not play a significant role. This study examined the muscle activity from relevant muscles during rear-end impacts in an effort to gauge their influence on the aetiology of whiplash associated disorders.

METHODS

Volunteers were subjected to a sub-injury level of rear impact. Surface electromyography (EMG) was used to record cervical muscle activity before, during and after impact. Muscle response time and EMG signal amplitude were analysed. Head, pelvis, and T1 acceleration data were recorded.

RESULTS

The activities of the cervical muscles were found to be significant. The sternocleidomastoideus, trapezius and erector spinae were activated on average 59 ms, 73 ms and 84 ms after the impact stimulus, respectively, prior to peak head acceleration (113 ms).

CONCLUSION

The cervical muscles reacted prior to peak head acceleration, thus in time to influence whiplash biomechanics and possibly injury mechanisms. It is recommended therefore, that muscular influences be incorporated into the development of the new rear-impact crash test dummy in order to make the dummy as biofidelic as possible.

Does vibration benefit delayed-onset muscle soreness?: a meta-analysis and systematic review

OBJECTIVE

Delayed-onset muscle soreness (DOMS) is a symptom of exercise-induced muscle injury that is commonly encountered in athletes and fitness enthusiasts. Vibration is being increasingly used to prevent or treat DOMS. We therefore carried out a meta-analysis to evaluate the effectiveness of vibration in patients with DOMS.

METHOD

We searched nine databases for randomized controlled trials of vibration in DOMS, from the earliest date available to 30 May 2018. Visual analogue scale (VAS) and creatine kinase (CK) levels were set as outcome measures.

RESULTS

The review included 10 identified studies with 258 participants. The meta-analysis indicated that vibration significantly improved the VAS at 24, 48, and 72 hours after exercise, and significantly improved CK levels at 24 and 48 hours, but not at 72 hours.

CONCLUSION

Vibration is a beneficial and useful form of physiotherapy for alleviating DOMS. However, further studies are needed to clarify the role and mechanism of vibration in DOMS.

Insights into the molecular etiology of exercise-induced inflammation: opportunities for optimizing performance

The study of exercise-induced muscle damage (EIMD) is of paramount importance not only because it affects athletic performance but also because it is an excellent model to study the mechanisms governing muscle cachexia under various clinical conditions. Although, a large number of studies have investigated EIMD and its associated inflammatory response, several aspects of skeletal muscles responses remain unclear. In the first section of this article, the mechanisms of EIMD are reviewed in an attempt to follow the events that result in functional and structural alterations of skeletal muscle. In the second section, the inflammatory response associated with EIMD is presented with emphasis in leukocyte accumulation through mechanisms that are largely coordinated by pro- and anti-inflammatory cytokines released either by injured muscle itself or other cells. The practical applications of EIMD and the subsequent inflammatory response are discussed with respect to athletic performance. Specifically, the mechanisms leading to performance deterioration and development of muscle soreness are discussed. Emphasis is given to the factors affecting individual responses to EIMD and the resulting interindividual variability to this phenomenon.

Delayed onset muscle soreness: Involvement of neurotrophic factors

Delayed-onset muscle soreness (DOMS) is quite a common consequence of unaccustomed strenuous exercise, especially exercise containing eccentric contraction (lengthening contraction, LC). Its typical sign is mechanical hyperalgesia (tenderness and movement related pain). Its cause has been commonly believed to be micro-damage of the muscle and subsequent inflammation. Here we present a brief historical overview of the damage-inflammation theory followed by a discussion of our new findings. Different from previous observations, we have observed mechanical hyperalgesia in rats 1-3 days after LC without any apparent microscopic damage of the muscle or signs of inflammation. With our model we have found that two pathways are involved in inducing mechanical hyperalgesia after LC: activation of the B2 bradykinin receptor-nerve growth factor (NGF) pathway and activation of the COX-2-glial cell line-derived neurotrophic factor (GDNF) pathway. These neurotrophic factors were produced by muscle fibers and/or satellite cells. This means that muscle fiber damage is not essential, although it is sufficient, for induction of DOMS, instead, NGF and GDNF produced by muscle fibers/satellite cells play crucial roles in DOMS.

Effects of load magnitude, muscle length and velocity during eccentric chronic loading on the longitudinal growth of the vastus lateralis muscle

The present study investigated the longitudinal growth of the vastus lateralis muscle using four eccentric exercise protocols with different mechanical stimuli by modifying the load magnitude, lengthening velocity and muscle length at which the load was applied. Thirty-one participants voluntarily participated in this study in two experimental and one control group. The first experimental group (N=10) exercised the knee extensors of one leg at 65% (low load magnitude) of the maximum isometric voluntary contraction (MVC) and the second leg at 100% MVC (high load magnitude) with 90 deg s(-1) angular velocity, from 25 to 100 deg knee angle. The second experimental group (N=10) exercised one leg at 100% MVC, 90 deg s(-1), from 25 to 65 deg knee angle (short muscle length). The other leg was exercised at 100% MVC, 240 deg s(-1) angular velocity (high muscle lengthening velocity) from 25 to 100 deg. In the pre- and post-intervention measurements, we examined the fascicle length of the vastus lateralis at rest and the moment-angle relationship of the knee extensors. After 10 weeks of intervention, we found a significant increase (~14%) of vastus lateralis fascicle length compared with the control group, yet only in the leg that was exercised with high lengthening velocity. The findings provide evidence that not every eccentric loading causes an increase in fascicle length and that the lengthening velocity of the fascicles during the eccentric loading, particularly in the phase where the knee joint moment decreases (i.e. deactivation of the muscle), seems to be an important factor for longitudinal muscle growth.

Establishment of an animal model for delayed-onset muscle soreness after high-intensity eccentric exercise and its application for investigating the efficacy of low-load eccentric training

BACKGROUND

Delayed-onset muscle soreness (DOMS) occurs after unaccustomed exercise and is particularly associated with eccentric exercise. Previous studies have proposed the use of a single bout of eccentric exercise to prevent the muscle damage subsequent to a bout of eccentric exercise. This study aimed to establish a suitable animal model to evaluate the pain in DOMS and to assess whether low-load eccentric training confers a protective effect against a subsequent high-intensity eccentric exercise bout.

METHODS

Thirty-six female Wistar rats were divided into five groups: rats that received muscular compression only (Comp); those that received high-intensity eccentric exercise only (HE); those that received muscular compression at 3, 24, 48, and 96 h after high-intensity eccentric exercise (HE + Comp/3, 24, 48, and 96 h); those that received muscular compression 48 h after a single low-load eccentric exercise (LE); and those that received a week of low-load eccentric training before high-intensity eccentric exercise, which was followed by muscular compression 48 h later (LET). Immunohistochemistry was used to investigate c-fos expression in the dorsal horn of the spinal cord.

RESULTS

For the HE + Comp/48 h rats, the total number of c-fos-positive neurons at the L2-3 segments was significantly greater than that in the Comp and HE rats in the same segments. A week of low-load eccentric training resulted in a decreased number of c-fos-ir neurons relative to that in the HE + Comp/48 h rats.

CONCLUSIONS

Muscle tenderness after high-intensity eccentric exercise was evaluated by c-fos expression in the dorsal horn of the rat spinal cord. Using this rat model, the present study clarified that the muscle tenderness following high-intensity eccentric exercise is inhibited by prior low-load eccentric training.

Can a standard dose of eicosapentaenoic acid (EPA) supplementation reduce the symptoms of delayed onset of muscle soreness?

Background

Unaccustomed exercise can result in delayed onset of muscle soreness (DOMS) which can affect athletic performance. Although DOMS is a useful tool to identify muscle damage and remodelling, prolonged symptoms of DOMS may be associated with the over-training syndrome. In order to reduce the symptoms of DOMS numerous management strategies have been attempted with no significant effect on DOMS-associated cytokines surge. The present study aimed to investigate the acute and chronic effects of a 2 × 180 mg per day dose of eicosapentaenoic acid (EPA) on interleukin-6 (IL-6) mediated inflammatory response and symptoms associated with DOMS.

Methods

Seventeen healthy non-smoking females (age 20.4 ± 2.1 years, height 161.2 ± 8.3 cm and mass 61.48 ± 7.4 kg) were randomly assigned to either placebo (N = 10) or EPA (N = 7). Serum IL-6, isometric and isokinetic (concentric and eccentric) strength, and rating of perceived exertion (RPE) were recorded on four occasions: i-prior to supplementation, ii-immediately after three weeks of supplementation (basal effects), iii-48 hours following a single bout of resistance exercise (acute training response effects), and iv-48 hours following the last of a series of three bouts of resistance exercise (chronic training response effects).

Results

There was only a group difference in the degree of change in circulating IL-6 levels. In fact, relative to the first baseline, by the third bout of eccentric workout, the EPA group had 103 ± 60% increment in IL-6 levels whereas the placebo group only had 80 ± 26% incremented IL-6 levels (P = 0.020). We also describe a stable multiple linear regression model which included measures of strength and not IL-6 as predictors of RPE scale.

Conclusion

The present study suggests that in doubling the standard recommended dose of EPA, whilst this may still not be beneficial at ameliorating the symptoms of DOMS, it counter intuitively appears to enhance the cytokine response to exercise. In a context where previous in vitro work has shown EPA to decrease the effects of inflammatory cytokines, it may in fact be that the doses required in vivo is much larger than current recommended amounts. An attempt to dampen the exercise-induced cytokine flux in fact results in an over-compensatory response of this system.

Maximum symmetric and asymmetric isoinertial lifting capabilities from floor to knuckle height

Ten young male participants were recruited to test their maximum symmetric and asymmetric isoinertial lifting capabilities from floor to the knuckle height in different container dimensions varied in both width and length. The results showed that the order from the highest to lowest lifting capability for the lifting modes was symmetric lifting, asymmetric lifting with leg rotation and asymmetric lifting with trunk rotation, and for the container dimensions was 50 x 35 x 15 cm, 70 x 35 x 15 cm and 50 x 50 x 15 cm. Participants' lifting capabilities differed significantly (p<0.05) among lifting modes and container dimensions. This study recommends that asymmetric lifting with leg rotation should be encouraged as compared with asymmetric lifting with trunk rotation when performing heavy asymmetric lifting tasks.

Localization and quantification of muscle damage by magnetic resonance imaging following step exercise in young women

Eccentric exercise affects muscles differentially according to intensity, duration, and previous exposure to the specific exercise activity. We used T2-weighted magnetic resonance imaging sequences to localize and quantify muscle damage following step exercise and to determine correlations between transverse relaxation time (T2) and other markers of muscle damage. Eight women performed two-step exercise bouts (30 min) separated by 8 weeks. Blood samples, MR scans, measurements of muscle strength, and muscle soreness were obtained immediately before, after, and up to 9 days after each bout. Resting muscle T2 (40.3+/-0.6 ms) increased exclusively in m. Adductor magnus (AM) in the thigh performing eccentric contractions and peaked 3 days after bout 1 (73.5+/-9.7 ms, P<0.05). Plasma creatine kinase (CK) activity peaked on day 3 after bout 1 and correlated with T2 in AM (r=0.96, P<0.001). After bout 2 CK and T2 were almost unaffected. This indicates that T2-weighted MRI can be applied to identify muscles from which enzymes are being released into the circulation.

Effect of aqua exercise on recovery of lower limb muscles after downhill running

The aim of the present study was to examine how the recovery of physiological functioning of the leg muscles after high-intensity eccentric exercise such as downhill running could be promoted by aqua exercise for a period until the damaged muscle had recovered almost completely. Ten male long-distance runners were divided equally into an aqua exercise group and a control group. From the first day (Day 0) to the fourth day (Day 3), the participants completed a questionnaire on muscle soreness, and serum creatine kinase activity, muscle power, flexibility, whole-body reaction time and muscle stiffness were measured. After measurements on Day 0, the participants performed downhill running (three 5 min runs with a 5 min rest interval at -10%, 335.7 +/- 6.1 m . min-1). The aqua exercise group performed walking, jogging and jumping in water on three successive days following the downhill running on Day 0 for 30 min each day. Muscle power was reduced on Day 1 in the control group (P < 0.05). Muscle soreness in the calf on Day 3 was greater in the control group than that in the aqua exercise group (P < 0.05). In the aqua exercise group, muscle stiffness in the calf was less than that in the control group over 4 days (time main effect: P < 0.05; group x time interaction: P < 0.05). We conclude that aqua exercise promoted physiological functioning of the muscles in the legs after high-intensity downhill running for a period until the damaged muscles had recovered almost completely.

The Stretch-Shortening Cycle

Neuromuscular fatigue has traditionally been examined using isolated forms of either isometric, concentric or eccentric actions. However, none of these actions are naturally occurring in human (or animal) ground locomotion. The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched (eccentric action) and then followed by the shortening (concentric) action. As the SSC taxes the skeletal muscles very strongly mechanically, its influence on the reflex activation becomes apparent and very different from the isolated forms of muscle actions mentioned above. The ground contact phases of running, jumping and hopping etc. are examples of the SSC for leg extensor muscles; similar phases can also be found for the upper-body activities. Consequently, it is normal and expected that the fatigue phenomena should be explored during SSC activities. The fatigue responses of repeated SSC actions are very versatile and complex because the fatigue does not depend only on the metabolic loading, which is reportedly different among muscle actions. The complexity of SSC fatigue is well reflected by the recovery patterns of many neuromechanical parameters. The basic pattern of SSC fatigue response (e.g. when using the complete exhaustion model of hopping or jumping) is the bimodality showing an immediate reduction in performance during exercise, quick recovery within 1-2 hours, followed by a secondary reduction, which may often show the lowest values on the second day post-exercise when the symptoms of muscle soreness/damage are also greatest. The full recovery may take 4-8 days depending on the parameter and on the severity of exercise. Each subject may have their own time-dependent bimodality curve. Based on the reviewed literature, it is recommended that the fatigue protocol is 'completely' exhaustive to reduce the important influence of inter-subject variability in the fatigue responses. The bimodality concept is especially apparent for stretch reflex responses, measured either in passive or active conditions. Interestingly, the reflex responses follow parallel changes with some of the pure mechanical parameters, such as yielding of the braking force during an initial ground contact of running or hopping. The mechanism of SSC fatigue and especially the bimodal response of performance deterioration and its recovery are often difficult to explain. The immediate post-exercise reduction in most of the measured parameters and their partial recovery 1-2 hours post-exercise can be explained primarily to be due to metabolic fatigue induced by exercise. The secondary reduction in these parameters takes place when the muscle soreness is highest. The literature gives several suggestions including the possible structural damage of not only the extrafusal muscle fibres, but also the intrafusal ones. Temporary changes in structural proteins and muscle-tendon interaction may be related to the fatigue-induced force reduction. Neural adjustments in the supraspinal level could naturally be operative, although many studies quoted in this article emphasise more the influences of exhaustive SSC fatigue on the fusimotor-muscle spindle system. It is, however, still puzzling why the functional recovery lasts several days after the disappearance of muscle soreness. Unfortunately, this and many other possible mechanisms need more thorough testing in animal models provided that the SSC actions can be truly performed as they appear in normal human locomotion.

Maximum isoinertial lifting capabilities for different lifting ranges and container dimensions

The aim of this study was to examine the effects of lifting range and container dimension on human maximum isoinertial lifting capability in the sagittal plane. Ten young and experienced lifters were tested for their maximum isoinertial lifting capabilities for 12 different lifting conditions (three lifting ranges x four container dimensions). The results showed that lifting range and container dimension significantly affected human maximum isoinertial lifting capability. The order for the highest to lowest lifting capability for the three lifting ranges was FK (from floor to knuckle height, 0-74 cm), FS (from floor to shoulder height, 0-141 cm) and KS (from knuckle height to shoulder height, 74-141 cm) regardless of the container dimension, and for the four container dimensions was 50 x 35 x 15 cm(3), 70 x 35 x 15 cm(3), 50 x 50 x 15 cm(3) and 70 x 50 x 15 cm(3) regardless of the lifting range. The mean(SD) maximum isoinertial lifting capability ranged from 29.3(3.3) kg for the combination of KS range and 70 x 50 x 15 cm(3) container to 53.2(5.7)kg for the combination of FK range and 50 x 35 x 15 cm(3) container. The results of this study can help our knowledge of human maximum isoinertial lifting capability and designing the upper limit of lifting weight.

Douleurs musculaires posteffort

Muscle intolerance to exercise may result from different processes. Diagnosis involves confirming first the source of pain, then potential pathological myalgia. Delayed-onset muscle soreness (DOMS), commonly referred as tiredness, occurs frequently in sport. DOMS usually develops 12-48 h after intensive and/or unusual eccentric muscle action. Symptoms usually involve the quadriceps muscle group but may also affect the hamstring and triceps surae groups. The muscles are sensitive to palpation, contraction and passive stretch. Acidosis, muscle spasm and microlesions in both connective and muscle tissues may explain the symptoms. However, inflammation appears to be the most common explanation. Interestingly, there is strong evidence that the progression of the exercise-induced muscle injury proceeds no further in the absence of inflammation. Even though unpleasant, DOMS should not be considered as an indicator of muscle damage but, rather, a sign of the regenerative process, which is well known to contribute to the increased muscle mass. DOMS can be associated with decreased proprioception and range of motion, as well as maximal force and activation. DOMS disappears 2-10 days before complete functional recovery. This painless period is ripe for additional joint injuries. Similarly, if some treatments are well known to attenuate DOMS, none has been demonstrated to accelerate either structural or functional recovery. In terms of the role of the inflammatory process, these treatments might even delay overall recovery.

Le travail musculaire excentrique : intérêts dans la prise en charge thérapeutique du sportif

OBJECTIVES

To review the research on the effects and indications of eccentric muscular contraction in the athlete.

METHODS

We searched the Medline database using the key words eccentric and negative work for reports of eccentric muscular contraction published from 1993 to 2004.

RESULTS

The physiologic features of eccentric contraction remain unknown but significantly differ from concentric contraction. Eccentric contraction has a specific effect: during sports practice, it permits the muscular and tendinous complex to support strain and strengthens the muscular action of articular stabilization. But eccentric contraction produces injuries: delayed-onset muscle soreness, and muscle rupture and tendinous injuries such as luxation, rupture, and tendinitis.

CONCLUSION

Treatment and prevention must have controlled protocols. In therapy, eccentric contraction must be realized at progressive speeds and resistances. Prevention of tendinous injury necessitates quantifying eccentric activity during training.

MRI evaluation of topical heat and static stretching as therapeutic modalities for the treatment of eccentric exercise-induced muscle damage

The aim of this study was to monitor the effects of topical heat and/or static stretch treatments on the recovery of muscle damage by eccentric exercise. For this purpose, 32 untrained male subjects performed intense eccentric knee extension exercise, followed by 2 weeks of treatment (heat, stretch, heat plus stretch) or no treatment (control, n=8/group). Isometric strength testing, pain ratings, and multi-echo magnetic resonance imaging of the thigh were performed before and at 2, 3, 4, 8, and 15 days following the exercise. Increased T2 relaxation time, muscle swelling, pain ratings, and strength loss confirmed significant muscle damage during the post-exercise period. Pain ratings and muscle volume recovered to baseline by 15 days, although muscle strength remained lower [77 (4) vs. 95 (3) kg pre-exercise, mean (SE)] and T2 values higher [32.2 (0.8) vs. 28.6 (0.2) ms pre-exercise]. Our results indicate that heat and/or static stretching does not consistently reduce soreness, swelling or muscle damage. The practical implication of our findings is that clinicians should be aware that prescribing heat and/or static stretching following intense eccentric or unaccustomed exercise will not enhance the recovery of damaged muscles.

Neuromuscular function after exercise-induced muscle damage: theoretical and applied implications

Exercise-induced muscle damage is a well documented phenomenon particularly resulting from eccentric exercise. When eccentric exercise is unaccustomed or is performed with an increased intensity or duration, the symptoms associated with muscle damage are a common outcome and are particularly associated with participation in athletic activity. Muscle damage results in an immediate and prolonged reduction in muscle function, most notably a reduction in force-generating capacity, which has been quantified in human studies through isometric and dynamic isokinetic testing modalities. Investigations of the torque-angular velocity relationship have failed to reveal a consistent pattern of change, with inconsistent reports of functional change being dependent on the muscle action and/or angular velocity of movement. The consequences of damage on dynamic, multi-joint, sport-specific movements would appear more pertinent with regard to athletic performance, but this aspect of muscle function has been studied less often. Reductions in the ability to generate power output during single-joint movements as well as during cycling and vertical jump movements have been documented. In addition, muscle damage has been observed to increase the physiological demand of endurance exercise and to increase thermal strain during exercise in the heat. The aims of this review are to summarise the functional decrements associated with exercise-induced muscle damage, relate these decrements to theoretical views regarding underlying mechanisms (i.e. sarcomere disruption, impaired excitation-contraction coupling, preferential fibre type damage, and impaired muscle metabolism), and finally to discuss the potential impact of muscle damage on athletic performance.

Central sensitization in fibromyalgia and other musculoskeletal disorders

Muscle hyperalgesia and referred pain play an important role in chronic musculoskeletal pain. New knowledge on the involved basic mechanisms and better methods to assess muscle pain in the clinic are needed to revise and optimize treatment regimens. Increased muscle sensitivity is manifested as pain evoked by a normally non-nociceptive stimulus (allodynia), increased pain intensity evoked by nociceptive stimuli (hyperalgesia), or increased referred pain areas with associated somatosensory changes. Some manifestations of sensitization, such as expanded referred muscle pain areas in patients with chronic musculoskeletal pain, can be explained from animal experiments showing extrasegmental spread of sensitization. An important part of the pain manifestations (eg, tenderness and referred pain) related to chronic musculoskeletal disorders may result from peripheral and central sensitization, which may play a role in the transition from acute to chronic pain.

Use of nonsteroidal anti-inflammatory drugs following exercise-induced muscle injury

The objective of this article is to examine the use of NSAIDs for attenuating exercise-induced muscle injuries (EIMI), with an emphasis on their safety and usefulness for improving muscle function and reducing soreness. NSAIDs are some of the most widely consumed medications in the world, and NSAID use as therapy for EIMI has increased dramatically over the last 20 years. However, there is a lack of agreement concerning NSAID effectiveness for this purpose. The lack of consensus about the efficacy of NSAID use in relation to EIMI has spawned a recent interest in sports medicine research regarding NSAIDs. The application of a variety of methods used to induce, assess and quantify muscle injury has contributed to the inconsistency among the findings regarding the efficacy of NSAIDs for EIMI. Therefore, future studies should focus on the evaluation of muscle injury and function, with the use of better functional measurement tools and more uniformity in the assessment tools used. However, from review of the current literature, it is concluded that NSAID use for brief periods of time is beneficial for short-term recovery of muscle function and is an important laboratory tool for the study of EIMI.

Delayed onset muscle soreness : treatment strategies and performance factors

Delayed onset muscle soreness (DOMS) is a familiar experience for the elite or novice athlete. Symptoms can range from muscle tenderness to severe debilitating pain. The mechanisms, treatment strategies, and impact on athletic performance remain uncertain, despite the high incidence of DOMS. DOMS is most prevalent at the beginning of the sporting season when athletes are returning to training following a period of reduced activity. DOMS is also common when athletes are first introduced to certain types of activities regardless of the time of year. Eccentric activities induce micro-injury at a greater frequency and severity than other types of muscle actions. The intensity and duration of exercise are also important factors in DOMS onset. Up to six hypothesised theories have been proposed for the mechanism of DOMS, namely: lactic acid, muscle spasm, connective tissue damage, muscle damage, inflammation and the enzyme efflux theories. However, an integration of two or more theories is likely to explain muscle soreness. DOMS can affect athletic performance by causing a reduction in joint range of motion, shock attenuation and peak torque. Alterations in muscle sequencing and recruitment patterns may also occur, causing unaccustomed stress to be placed on muscle ligaments and tendons. These compensatory mechanisms may increase the risk of further injury if a premature return to sport is attempted.A number of treatment strategies have been introduced to help alleviate the severity of DOMS and to restore the maximal function of the muscles as rapidly as possible. Nonsteroidal anti-inflammatory drugs have demonstrated dosage-dependent effects that may also be influenced by the time of administration. Similarly, massage has shown varying results that may be attributed to the time of massage application and the type of massage technique used. Cryotherapy, stretching, homeopathy, ultrasound and electrical current modalities have demonstrated no effect on the alleviation of muscle soreness or other DOMS symptoms. Exercise is the most effective means of alleviating pain during DOMS, however the analgesic effect is also temporary. Athletes who must train on a daily basis should be encouraged to reduce the intensity and duration of exercise for 1-2 days following intense DOMS-inducing exercise. Alternatively, exercises targeting less affected body parts should be encouraged in order to allow the most affected muscle groups to recover. Eccentric exercises or novel activities should be introduced progressively over a period of 1 or 2 weeks at the beginning of, or during, the sporting season in order to reduce the level of physical impairment and/or training disruption. There are still many unanswered questions relating to DOMS, and many potential areas for future research.

Desmin cytoskeletal modifications after a bout of eccentric exercise in the rat

Desmin content and immunohistochemical appearance were measured in tibialis anterior muscles of rats subjected to a single bout of 30 eccentric contractions (ECs). Ankle torque was measured before EC and at various recovery times, after which immunohistochemical and immunoblot analyses were performed. Torque decreased by approximately 50% immediately after EC and fully recovered 168 h later (P < 0.001). Loss of desmin staining was maximal 12 h after EC and recovered by 72 h. Immunoblots unexpectedly demonstrated a significant increase in the desmin-to-actin ratio by 72 h after EC (P < 0.01) and was still increasing after 168 h (P < 0.0001). These data demonstrate a relatively rapid qualitative loss of desmin immunostaining immediately after a single EC bout but a tremendous quantitative increase in desmin content 72-168 h later. This dynamic restructuring of the muscle's intermediate filament system may be involved in the mechanism of EC-induced muscle injury and may provide a structural explanation for the protective effects observed in muscle after a single EC bout.

The effects of fish oil and isoflavones on delayed onset muscle soreness

INTRODUCTION/PURPOSE

Fish oils (FO) have been shown to modulate the inflammatory response through alteration of the eicosanoid pathway. Isoflavones (ISO) appear to reduce the inflammatory pathway through their role as a tyrosine kinase inhibitor. Delayed onset muscle soreness (DOMS) develops after intense exercise and has been associated with an inflammatory response. Therefore, we hypothesized that physical parameters associated with DOMS could be decreased via the modulation of the inflammatory response by supplementing subjects with either FO or ISO.

METHODS

22 subjects were recruited and randomly assigned to one of three treatment groups: FO (1.8 g of omega-3 fatty acids x d(-1)), ISO (120 mg soy isolate x d(-1)), or placebo (PL) (Western fat blend and/or wheat flour). All treatment groups received 100-IU vitamin E x d(-1) to minimize lipid peroxidation of more highly unsaturated fatty acids. Subjects were supplemented 30 d before the exercise and during the week of testing and were instructed to refrain from unusual exercise. DOMS was induced by 50 maximal isokinetic eccentric elbow flexion contractions. Strength parameters, pain, arm circumference, and relaxed arm angle (RANG) were measured at 48, 72, and 168 h post exercise. Cortisol, creatine kinase (CK), interleukin-6 (IL-6), tumor necrosis factor (TNFalpha), malondialdehyde (MDA), and serum iron were measured before supplementation, after supplementation, and post exercise.

RESULTS

Significant decreases were observed in RANG and strength 48 h postexercise among all groups, and there were significant increases in pain and arm circumference. There were no significant changes among all groups from baseline at 168 h (7 d) post exercise. There were no significant treatment effects between groups for the physical parameters or for cortisol, CK, IL-6, TNFalpha, MDA, or serum iron.

CONCLUSION

These data indicate FO or ISO, at the doses supplemented, were not effective in ameliorating DOMS with the above-cited protocol.

MR imaging in nonneoplastic muscle disorders of the lower extremity

The exquisite tissue contrast and multiplanar capability of MRI make it the optimal imaging modality for diagnosing muscle injuries and other muscle disorders. These examinations can be performed with increasing speed because of improvements in gradient strength and software and coil design. Presently, some of the limitations of MRI of muscle relate to the lack of specificity of the findings. The advent of functional muscle MR[ will increase the understanding of human muscle diseases, and increasingly place MRI in a central role for diagnosis and follow-up analysis.

Thermosensitivity of muscle: high-intensity thermal stimulation of muscle tissue induces muscle pain in humans

Small-calibre afferent units responding to thermal stimuli have previously been reported to exist in muscle. The question as to whether these receptors in humans mediate subjective thermal sensations from muscle remains unresolved. The aims of the present study were to determine in humans whether intramuscular injection of warm and cold isotonic saline elicits temperature sensations, muscle pain or any other sensations. In 15 subjects, no thermal sensations assessed on a temperature visual analogue scale (VAS) could be detected with intramuscular injections of isotonic saline (1.5 ml) into the anterior tibial muscle at temperatures ranging from 8 to 48 degrees C. The same subjects recorded strongly increasing scores on a temperature VAS when thermal stimuli in the same intensity range were applied to the skin overlying the muscle by a contact thermode. However, I.M. isotonic saline of 48 degrees C induced muscle pain with peak scores of 3.2 +/- 0.8 cm on a VAS scale ranging from 0 to 10 cm. Using the the McGill pain questionnaire a subgroup, of subjects qualitatively described the pain using the 'thermal hot' and 'dullness' word groups. Temperature measurements within the muscle during the stimulating injections showed that the time course of the pain sensation elicited by saline at 48 degrees C paralleled that of the intramuscular temperature and far outlasted the injection time. The present data show that high-intensity thermal stimulation of muscle is associated with muscle pain. High-threshold warm-sensitive receptors may mediate the pain following activation by temperatures of 48 degrees C or more. Taken together, the data indicate that thermosensation from a given volume of muscle is less potent than nociception.

Eccentric exercise-induced injuries to contractile and cytoskeletal muscle fibre components

Exercise involving lengthening of an activated muscle can cause injury. Recent reports documented the mechanics of exercise-induced muscle injury as well as physiological and cellular events and manifestations of injury. Loss of the cytoskeletal protein desmin and loss of cellular integrity as evidenced by sarcolemmal damage occur early during heavy eccentric exercise. These studies indicate that the earliest events in muscle injury are mechanical in nature, while later events indicate that it may be more appropriate to conclude that intense exercise initiates a muscle remodeling process. We conclude that muscle injury after eccentric exercise is differently severe in muscles with different architecture, is fibre type-specific, primarily because of fibre strain in the acute phase, and is exacerbated by inflammation after the initial injury.

Vitamin E, vitamin C, and exercise

Exercise increases the generation of oxygen free radicals and lipid peroxidation. Strenuous exercise in a person who is unconditioned or unaccustomed to exercise will induce oxidative damage and result in muscle injury. However, aerobic exercise training strengthens the antioxidant defense system by increasing superoxide dismutase. Vitamin C and, especially, vitamin E are shown to decrease the exercise-induced increase in the rate of lipid peroxidation. No ergogenic effects of either vitamin C or E have been shown. Vitamin E was shown to significantly increase circulating neutrophils in older, but not younger, subjects performing eccentric exercise that causes an increase in skeletal muscle damage. In addition to its effect in augmenting the neutrophil response to eccentric exercise, vitamin E causes a greater increase in circulating creatine kinase activity, perhaps indicating increased skeletal muscle repair. Increased vitamin E intake has been associated with enhanced glucose tolerance and insulin action as well as improved lipoprotein status. Future research should examine the combined effects of exercise training and vitamins E and C on these health-related outcomes.

Lack of effect of combined low intensity laser therapy/phototherapy (CLILT) on delayed onset muscle soreness in humans

BACKGROUND AND OBJECTIVES

This study, which was approved by the University's Ethical committee, was conducted to investigate the effectiveness of Combined Low Intensity Laser Therapy/Phototherapy (CLILT) in alleviating the signs and symptoms of Delayed Onset Muscle Soreness (DOMS) over an 11-day period.

STUDY DESIGN/MATERIALS AND METHODS

Thirty-six subjects (18 M: 18 F) were randomly allocated, under strictly controlled double-blind conditions, to one of three experimental conditions: Control, Placebo, and CLILT (660-950 nm; 11 J/cm2; pulsed at 73 Hz). DOMS was induced in a standardised fashion in the non-dominant elbow flexors using repeated eccentric contractions until exhaustion was reached. Subjects returned on five consecutive days, and two days during the following week, for treatment according to group, and assessment of outcome variables including range of motion, pain, and tenderness.

RESULTS

While analysis of results using repeated measures and one factor ANOVA with post-hoc tests showed significant changes in all variables over time (P < 0.05) as a result of the induction procedure, there were no significant differences observed between groups.

CONCLUSIONS

CLILT failed to show any beneficial treatment effect on DOMS, at least at the parameters used here. These results therefore provide no evidence for the claimed biostimulating effects of such therapy.

Validity of diagnostic ultrasound as a measure of delayed onset muscle soreness

STUDY DESIGN

Repeated measures were taken to evaluate delayed onset muscle soreness (DOMS) following eccentric bicep contractions of the nondominant arm at 140% of 1 repetition maximum (RM) while the dominant arm served as control.

OBJECTIVES

To explore the usefulness of a noninvasive method to assess delayed onset muscle soreness.

BACKGROUND

Although many methods have been proposed to assess DOMS, most are somewhat subjective or require a blood sample. This study compared the assessment of DOMS following eccentric exercise using common assessment techniques with diagnostic ultrasound (US).

METHODS AND MEASURES

Forty nonimpaired women (18-40 years) used a Cybex isotonic biceps curl machine to eccentrically lower, using their nondominant arm, 140% of their dominant arm 1 RM to induce muscle soreness. Four assessment methods, (1) goniometry assessing spontaneous muscle shortening (SMS); (2) subjective muscle soreness ratings (MSRs); (3) serum creatine kinase (CK); and (4) diagnostic US scans of muscle cross-sectional area (CSA), were conducted at 5 different assessment times: (1) pre-eccentric exercise; (2) postexercise; (3) 24 hours postexercise; (4) 48 hours postexercise; and (5) 72 hours postexercise.

RESULTS

Significant differences existed across assessment times for 3 of the 4 assessment techniques, CK, SMS, and MSR.

CONCLUSIONS

Previously published methodologies used to assess DOMS (CK, SMS, and MSR) were able to provide consistent and expected results relative to the onset and progression of soreness with a high degree of relatedness (r = 0.48-0.84). However, it appeared that the ability to assess muscle soreness by diagnostic US, as evidenced by intramuscular swelling, was limited. Thus, the technique was not sensitive enough to detect any statistically significant changes in muscle CSA.

Eccentric exercise markedly increases c-Jun NH(2)-terminal kinase activity in human skeletal muscle

Eccentric contractions require the lengthening of skeletal muscle during force production and result in acute and prolonged muscle injury. Because a variety of stressors, including physical exercise and injury, can result in the activation of the c-Jun NH(2)-terminal kinase (JNK) intracellular signaling cascade in skeletal muscle, we investigated the effects of eccentric exercise on the activation of this stress-activated protein kinase in human skeletal muscle. Twelve healthy subjects (7 men, 5 women) completed maximal concentric or eccentric knee extensions on a KinCom isokinetic dynamometer (10 sets, 10 repetitions). Percutaneous needle biopsies were obtained from the vastus lateralis muscle 24 h before exercise (basal), immediately postexercise, and 6 h postexercise. Whereas both forms of exercise increased JNK activity immediately postexercise, eccentric contractions resulted in a much higher activation (15.4 +/- 4.5 vs. 3.5 +/- 1.4-fold increase above basal, eccentric vs. concentric). By 6 h after exercise, JNK activity decreased back to baseline values. In contrast to the greater activation of JNK with eccentric exercise, the mitogen-activated protein kinase kinase 4, the immediate upstream regulator of JNK, was similarly activated by concentric and eccentric exercise. Because the activation of JNK promotes the phosphorylation of a variety of transcription factors, including c-Jun, the results from this study suggest that JNK may be involved in the molecular and cellular adaptations that occur in response to injury-producing exercise in human skeletal muscle.

Delayed onset muscle soreness: lack of effect of therapeutic ultrasound in humans

OBJECTIVE

To investigate the effects of two dosages of pulsed ultrasound therapy (1 MHz, spatial averaged peak intensity 0.8 W/cm2, mark space ratio of 1:4) on acute-stage delayed onset muscle soreness (DOMS).

DESIGN

Double-blind, placebo-controlled, randomized trial.

SETTING

Laboratory of a university physiotherapy department.

PARTICIPANTS

Forty-eight healthy volunteers (24 men, 24 women) with no arm pathology or pain at the time of the study.

INTERVENTIONS

Subjects were randomly allocated to one of four treatment groups: control, placebo (sham insonation), low-dosage pulsed ultrasound (mean dosage 172.8 J), or high-dosage pulsed ultrasound (mean dosage 345.6 J). DOMS was induced in the nondominant elbow flexors in a standardized fashion through repeated eccentric exercise until exhaustion.

MAIN OUTCOME MEASURES

Elbow extension, flexion, and resting angles (universal goniometer), pain (visual analogue scale), mechanical pain threshold/tenderness (pressure algometer), and a McGill pain questionnaire. Measurements were taken before and after treatment each day except for the McGill pain questionnaire, which was completed at the end of the trial.

RESULTS

Significant differences were seen between groups in relation to range of flexion (p = .0032), with the control group losing least range of flexion. There were no other significant differences between the groups.

CONCLUSION

No convincing evidence was found to support the use of pulsed ultrasound therapy in the management of DOMS at the parameters discussed here.

Does post-exercise massage treatment reduce delayed onset muscle soreness? A systematic review

BACKGROUND

Delayed onset muscle soreness (DOMS) is a frequent problem after unaccustomed exercise. No universally accepted treatment exists. Massage therapy is often recommended for this condition but uncertainty exists about its effectiveness.

AIM

To determine whether post-exercise massage alleviates the symptoms of DOMS after a bout of strenuous exercise.

METHOD

Various computerised literature searches were carried out and located seven controlled trials.

RESULTS

Most of the trials were burdened with serious methodological flaws, and their results are far from uniform. However, most suggest that post-exercise massage may alleviate symptoms of DOMS.

CONCLUSIONS

Massage therapy may be a promising treatment for DOMS. Definitive studies are warranted.