Various treatment techniques on signs and symptoms of delayed onset muscle soreness

Eccentric activities are an important component of physical conditioning and everyday activities. Delayed onset muscle soreness (DOMS) can result from strenuous eccentric tasks and can be a limiting factor in motor performance for several days after exercise. An efficacious method of treatment for DOMS would enhance athletic performance and hasten the return to activities of daily living. The purpose of this study was to identify a treatment method which could assist in the recovery of DOMS. In the selection of treatment methods, emphasis was directed toward treatments that could be rendered independently by an individual, therefore making the treatment valuable to an athletic trainer in team setting. DOMS was induced in 70 untrained volunteers via 15 sets of 15 eccentric contractions of the forearm extensor muscles on a Lido isokinetic dynamometer. All subjects performed a pilot exercise bout for a minimum of 9 weeks before data collection to assure that DOMS would be produced. Data were collected on 15 dependent variables: active and passive wrist flexion and extension, forearm girth, limb volume, visual analogue pain scale, muscle soreness index, isometric strength, concentric and eccentric wrist total work, concentric and eccentric angle of peak torque. Data were collected on six occasions: pre- and post-induced DOMS, 20 minutes after treatment, and 24, 48, and 72 hours after treatment. Subjects were randomly assigned to 1 of 7 groups (6 treatment and 1 control). Treatments included a nonsteroidal anti-inflammatory drug, high velocity concentric muscle contractions on an upper extremity ergometer, ice massage, 10-minute static stretching, topical Amica montana ointment, and sublingual A. montana pellets. A 7 x 6 ANOVA with repeated measures on time was performed on the delta values of each of the 15 dependent variables. Significant main effects (p < .05) were found for all of the dependent variables on time only. There were no significant differences between treatments. Therefore, we conclude that none of the treatments were effective in abating the signs and symptoms of DOMS. In fact, the NSAID and A. montana treatments appeared to impede recovery of muscle function.     

Eccentric exercise, isokinetic muscle torque and delayed onset muscle soreness: the role of reactive oxygen species

There is growing evidence that reactive oxygen species (ROS) are involved in the muscular damage and soreness that is observed following strenuous or unaccustomed exercise. This study investigated the relationship between delayed onset muscle soreness (DOMS), muscle function and ROS following downhill running using electron spin resonance (ESR) spectroscopy and plasma malonaldehyde (MDA) concentrations. Eight physically active male subjects participated in two trials consisting of 30 min of running at ~65% O_2max on the flat (FLA) or a 15% downhill (DWN) gradient. Venous blood samples were drawn before, immediately after, and then 24, 48 and 72 h post exercise, and at the same time DOMS and muscle function were assessed. Blood was analysed for markers of ROS, total and differential white blood cell count, and creatine kinase. Muscle function was measured on an isokinetic dynamometer, whilst DOMS was assessed using a visual analogue scale. An increase in ROS, detected via ESR spectroscopy and MDA, was observed following DWN (P<0.05) but not following FLA. Increased DOMS and loss of muscle function were observed following DWN (P<0.05) but not following FLA (P>0.05). DWN resulted in a transient leukocytosis (P<0.05) occurring immediately post-exercise but returning to pre-exercise levels by 24 h. Although DWN resulted in an increase in ROS production, the increase occurred after the peak decline in muscle function and DOMS, suggesting that there may be a disassociation in the temporal relationship between ROS, loss of muscle function and DOMS.     

肌内效贴对延迟性肌肉酸痛影响的Meta分析

文题释义：肌内效贴：作为一种临床辅助治疗手段被广泛应用于与运动相关的损伤。通过不同的肌内效贴贴扎方式产生不同的治疗效果,在损伤后减轻疼痛、消除肿胀、改善活动度以及改善运动表现等方面具有一定疗效,但也有学者指出其疗效存在安慰剂效应。作者针对肌内效贴对延迟性肌肉酸痛的是否具有疗效以及其疗效是否为安慰剂效应进行分析。 延迟性肌肉酸痛：是指由于不习惯的或离心的运动导致迟发性地肌肉疼痛、压痛以及肌肉功能障碍等症状,通过休息一般在一周内可完全恢复,但其造成的炎症、肿胀和疼痛等症状会阻碍运动员或其他体力劳动者达到最佳运动水平。目前,临床采用治疗手段效果尚可,尚不明确最佳治疗策略。因此,如何有效预防和缓解延迟性肌肉酸痛一直是体育领域和医学领域的热点问题。 背景：既往研究显示肌内效贴对延迟性肌肉酸痛疗效尚不一致。 目的：运用Meta分析方法综合定量评价肌内效贴对延迟性肌肉酸痛的疗效,旨在为此技术的临床应用提供理论依据。方法：检索从中国知网、万方数字资源数据库、Web of Science、PubMed、EBSCO等数据库中关于肌内效贴治疗延迟性肌肉酸痛的随机对照试验,检索时限从数据库建库至2019年10月。采用Cochrane协作网中随机对照试验偏倚风险评价标准进行方法学质量评估,采用RevMan 5.3软件进行Meta分析。采用Stata 15.0进行Meta回归分析。结果与结论：最终纳入9项随机对照试验,共382例患者。Meta分析发现,肌内效贴组主观疼痛评分(目测类比评分)明显低于无刺激组[SMD=-0.85,95%CI(-1.32,-0.39),P=0.000 3],肌内效贴组肌酸激酶水平较无刺激组差异无显著性意义[SMD=0.30,95%CI(-0.17,0.76),P=0.21];与假刺激组相比,主观疼痛评分[SMD=-0.20,95%CI(-0.46,0.06),P=0.13]和肌酸激酶水平[SMD=0.22,95%CI(-0.06,0.49),P=0.12]差异均无显著性意义。提示肌内效贴可能有利于减轻延迟性肌肉酸痛患者主观疼痛程度,其疗效存在安慰剂效应。ORCID: 0000-0001-8000-4236(耿治中) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Effect of hydrotherapy on the signs and symptoms of delayed onset muscle soreness

This study independently examined the effects of three hydrotherapy interventions on the physiological and functional symptoms of delayed onset muscle soreness (DOMS). Strength trained males (n = 38) completed two experimental trials separated by 8 months in a randomised crossover design; one trial involved passive recovery (PAS, control), the other a specific hydrotherapy protocol for 72 h post-exercise; either: (1) cold water immersion (CWI: n = 12), (2) hot water immersion (HWI: n = 11) or (3) contrast water therapy (CWT: n = 15). For each trial, subjects performed a DOMS-inducing leg press protocol followed by PAS or one of the hydrotherapy interventions for 14 min. Weighted squat jump, isometric squat, perceived pain, thigh girths and blood variables were measured prior to, immediately after, and at 24, 48 and 72 h post-exercise. Squat jump performance and isometric force recovery were significantly enhanced (P < 0.05) at 24, 48 and 72 h post-exercise following CWT and at 48 and 72 h post-exercise following CWI when compared to PAS. Isometric force recovery was also greater (P < 0.05) at 24, 48, and 72 h post-exercise following HWI when compared to PAS. Perceived pain improved (P < 0.01) following CWT at 24, 48 and 72 h post-exercise. Overall, CWI and CWT were found to be effective in reducing the physiological and functional deficits associated with DOMS, including improved recovery of isometric force and dynamic power and a reduction in localised oedema. While HWI was effective in the recovery of isometric force, it was ineffective for recovery of all other markers compared to PAS. An erratum to this article can be found at     

Absence of mechanical hyperalgesia after exercise (delayed onset muscle soreness) in neonatally capsaicin-treated rats

Delayed onset muscle soreness (DOMS) appears with some delay after unaccustomed, strenuous exercise, especially after lengthening contraction (LC). It is characterized by tenderness and movement related pain, namely muscular mechanical hyperalgesia. To clarify the involvement of C-fibers in this mechanical hyperalgesia, we examined whether DOMS could be induced in rats treated neonatally with capsaicin. We confirmed that a large portion of unmyelinated afferent fibers were lost in capsaicin treated rats. In these animals, LC failed to induce muscular mechanical hyperalgesia. mRNA of nerve growth factor (NGF) in the muscle, which plays a pivotal role in maintaining mechanical hyperalgesia, was upregulated in the capsaicin treated animals similar to the vehicle treated animals. These results demonstrate that C-fiber afferents are essential in transmitting the nociceptive information from exercised muscle in DOMS.     

Enhanced temporal summation of pressure pain in the trapezius muscle after delayed onset muscle soreness

Temporal summation of muscle pain is an important factor in musculoskeletal pain as central integration of repetitive nociceptive input can be facilitated in musculoskeletal pain patients. The aim of this study is to evaluate changes in temporal summation of pressure pain after induction of delayed onset muscle soreness (DOMS) of the trapezius muscle. Sixteen healthy volunteers participated in the study. Temporal summation of pain was induced by sequential pressure stimulation by a computer-controlled algometer. Sequential stimulation consisting of ten stimuli (at pressure pain threshold intensity) was applied over the trapezius muscle. Stimulus duration was 1 s and inter-stimulus intervals (ISI) were 1, 5, 10, and 30 s, respectively. The pain was rated on a continuous visual analogue scale (VAS, 10 cm) after each stimulus and normalised to the VAS score from the first stimulus. DOMS was induced in the right trapezius muscle by eccentric shoulder exercises while the left trapezius muscle served as control. Temporal summation of pressure evoked pain was measured before and 24 h after the exercise. At 24 h after exercise, soreness intensity during shoulder elevation was 3.7±0.2 cm, while no soreness was observed on the control side. When sequential pressure stimulation was applied to the DOMS muscle, VAS scores for 1 s ISI progressively increased to a higher level than before exercise (VAS increase for the last stimulus: 0.8±0.2 cm vs. 0.6±0.1 cm, P<0.05), while VAS scores for ISI 5, 10, and 30 s were not increased. On the control side, significant increases in VAS scores was observed for all ISIs but not affected by contralateral DOMS. Facilitation of temporal summation for 1 s ISI indicated that DOMS may increase the central excitability besides involving peripheral sensitisation. During DOMS there was no potential for further nociceptor sensitisation by repeated noxious pressure stimuli, which may account for the diminishment of temporal summation evoked by pressure stimuli with ISI 5, 10, and 30 s. These data indicate that muscle soreness might facilitate the central components of temporal summation to mechanical stimulation.     

延迟性肌肉酸痛动物模型的建立及组织形态学观察

背景：延迟性肌肉酸痛和骨骼肌微损伤有密切关系,但对于骨骼肌微损伤的确切机制还不太清楚。 目的：通过离心运动建立骨骼肌微损伤模型,通过其组织形态学和超微结构变化。 方法：将40只雄性SD大鼠随机等分为安静对照组、运动后即刻组、运动后24 h组、运动后48 h组和运动后72 h组。后4组大鼠进行一次间歇性下坡跑运动,速度为16 m/min,坡度为-16°,5 min运动,2 min休息,共120 min。运动后即刻组、运动后24 h组、运动后48 h组和运动后72 h组大鼠分别于运动后即刻、24,48,72 h进行观察。 结果与结论：离心运动后,大鼠骨骼肌组织形态结构和超微结构都发生了程度不同的变化,骨骼肌组织中结蛋白和波形蛋白出现不同程度的抗结蛋白抗体染色脱染。表明一次性离心运动能引起延迟性骨骼肌微损伤。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Effects of massage on delayed-onset muscle soreness, swelling, and recovery of muscle function

Context: Delayed-onset muscle soreness (DOMS) describes muscle pain and tenderness that typically develop several hours postexercise and consist of predominantly eccentric muscle actions, especially if the exercise is unfamiliar. Although DOMS is likely a symptom of eccentric-exercise–induced muscle damage, it does not necessarily reflect muscle damage. Some prophylactic or therapeutic modalities may be effective only for alleviating DOMS, whereas others may enhance recovery of muscle function without affecting DOMS.Objective: To test the hypothesis that massage applied after eccentric exercise would effectively alleviate DOMS without affecting muscle function.Design: We used an arm-to-arm comparison model with 2 independent variables (control and massage) and 6 dependent variables (maximal isometric and isokinetic voluntary strength, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness). A 2-way repeated-measures analysis of variance and paired t tests were used to examine differences in changes of the dependent variable over time (before, immediately and 30 minutes after exercise, and 1, 2, 3, 4, 7, 10, and 14 days postexercise) between control and massage conditions.Setting: University laboratory.Patients or Other Participants: Ten healthy subjects (5 men and 5 women) with no history of upper arm injury and no experience in resistance training.Intervention(s): Subjects performed 10 sets of 6 maximal isokinetic (90°·s⁻¹) eccentric actions of the elbow flexors with each arm on a dynamometer, separated by 2 weeks. One arm received 10 minutes of massage 3 hours after eccentric exercise; the contralateral arm received no treatment.Main Outcome Measure(s): Maximal voluntary isometric and isokinetic elbow flexor strength, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness.Results: Delayed-onset muscle soreness was significantly less for the massage condition for peak soreness in extending the elbow joint and palpating the brachioradialis muscle (P < .05). Soreness while flexing the elbow joint (P = .07) and palpating the brachialis muscle (P = .06) was also less with massage. Massage treatment had significant effects on plasma creatine kinase activity, with a significantly lower peak value at 4 days postexercise (P < .05), and upper arm circumference, with a significantly smaller increase than the control at 3 and 4 days postexercise (P < .05). However, no significant effects of massage on recovery of muscle strength and ROM were evident.Conclusions: Massage was effective in alleviating DOMS by approximately 30% and reducing swelling, but it had no effects on muscle function.     

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.     

The respiratory response to passive and active arm movements is enhanced in delayed onset muscle soreness

We previously reported that ventilatory response at the onset of light leg exercise was augmented in delayed onset muscle soreness (DOMS) after eccentric exercise (ECC) utilizing the leg. In this study, we examined whether the same result would appear in light exercise in which an arm with DOMS was utilized. Eleven subjects performed ECC using one arm, and we measured ventilatory responses to a 20-s single-arm extension–flexion exercise and to passive movement (PAS) before and 2 days after ECC (D2). We found that ventilatory response to both the exercise and PAS in which all subjects perceived DOMS was augmented at D2. It was concluded that initial hyperpnea, which occurred during arm exercise in DOMS, was enhanced, and from examining the result of PAS, enhanced initial exercise hyperpnea may be due in part to an exaggerated peripheral neural reflex.     

The effects of a single bout of downhill running and ensuing delayed onset of muscle soreness on running economy performed 48 h later

Delayed onset of muscle soreness (DOMS) is a common response to exercise involving significant eccentric loading. Symptoms of DOMS vary widely and may include reduced force generating capacity, significant alterations in biochemical indices of muscle and connective tissue health, alteration of neuromuscular function, and changes in mechanical performance. The purpose of the investigation was to examine the effects of downhill running and ensuing DOMS on running economy and stride mechanics. Nine, well-trained distance runners and triathletes participated in the study. Running economy was measured at three relative intensities [65, 75, and 85% of maximal aerobic capacity (V̇O_2peak)] before (RE1) and 48 h after (RE2) a 30-min downhill run (−10%) at 70% V̇O_2peak. Dependent variables included leg muscle soreness, rate of oxygen consumption (V̇O₂), minute ventilation, respiratory exchange ratio, lactate, heart rate, and stride length. These measurements were entered into a two-factor multivariate analysis of variance (MANOVA). The analysis revealed a significant time effect for all variables and a significant interaction (time × intensity) for lactate. The energy cost of locomotion was elevated at RE2 by an average of 3.2%. This was coupled with a significant reduction in stride length. The change in V̇O₂ was inversely correlated with the change in stride length (r= −0.535). Lactate was significantly elevated at RE2 for each run intensity, with a mean increase of 0.61 mmol l⁻¹. Based on these findings, it is suggested that muscle damage led to changes in stride mechanics and a greater reliance on anaerobic methods of energy production, contributing to the change in running economy during DOMS.     

Lack of effect of acupuncture upon signs and symptoms of delayed onset muscle soreness.

The effect of acupuncture upon experimentally induced delayed onset muscle soreness (DOMS) was assessed in a placebo-controlled study under blinded conditions. Volunteers (n = 48; 24 M & 24 F) were randomly allocated to one of four groups: control (20 min rest), placebo (minimal needling at non-acupuncture points), treatment group 1 (acupuncture at classic acupuncture points) and treatment group 2 (acupuncture at 'tender' points). DOMS was induced in the elbow flexors of the non-dominant arm using a standardized eccentric exercise regime. Measurements of elbow range of movement (flexion, extension, relaxed angle), and pain as well as visual analogue scores (VAS), tenderness (using a pressure algometer) were employed as indices of treatment efficacy. Measurements of elbow range of movement and tenderness were made prior to DOMS induction on the first day, and repeated pre- and post-treatment on subsequent days; pain was assessed using visual analogue scales post-induction and post-treatment on the first day, and pre- and post-treatment thereafter. For all conditions, subjects rested supine for a period of 20 min, during which treatment was delivered according to group allocation. Repeated measures and one-way analysis of variance (ANOVA) demonstrated no significant interactive (AB) effects, except for visual analogue scores (P = 0.0483); one factor ANOVA on the second day of the experiment (pre-treatment) indicated significant differences between the control and all other groups. However, such differences were not found on any other day of the experiment. It is concluded that acupuncture has little effect upon the cardinal signs and symptoms of DOMS, at least under the conditions of the current experiment.     

Effect of transcutaneous electrical nerve stimulation, cold, and a combination treatment on pain, decreased range of motion, and strength loss associated with delayed onset muscle soreness

Athletic trainers have a variety of therapeutic agents at their disposal to treat musculoskeletal pain, but little objective evidence exists of the efficacy of the modalities they use. In this study, delayed onset muscle soreness (DOMS) served as a model for musculoskeletal injury in order to: (1) compare the changes in perceived pain, elbow extension range of motion, and strength loss in subjects experiencing DOMS in the elbow flexor muscle group following a single treatment with either transcutaneous electrical nerve stimulation (TENS), cold, a combination of TENS and cold, sham TENS, or 20 minutes of rest; (2) compare the effects of combining static stretching with these treatments; and (3) determine if decreased pain is accompanied by a restoration of strength. DOMS was induced in the non-dominant elbow flexor muscle group in 40 females (age = 22.0 ± 4.3 yr) with repeated eccentric contractions. Forty-eight hours following exercise, all subjects presented with pain, decreased elbow extension range of motion, and decreased strength consistent with DOMS. Subjects were randomly assigned to 20-minute treatments followed by static stretching. Cold, TENS, and the combined treatment resulted in significant decreases in perceived pain. Treatments with cold resulted in a significant increase in elbow extension range of motion. Static stretching also significantly reduced perceived pain. Only small, nonsignificant changes in muscle strength were observed following treatment or stretching, regardless of the treatment group. These results suggest that the muscle weakness associated with DOMS is not the result of inhibition caused by pain. The results suggest that these modalities are effective in treating the pain and muscle spasm associated with DOMS, and that decreased pain may not be an accurate indicator of the recovery of muscle strength.     

Effects of tender point acupuncture on delayed onset muscle soreness (DOMS) – a pragmatic trial

Background  

Acupuncture is used to reduce inflammation and decrease pain in delayed onset muscle soreness (DOMS). This study investigates the efficacy of acupuncture on the symptoms of DOMS.     

Linear and nonlinear analyses of multi-channel mechanomyographic recordings reveal heterogeneous activation of wrist extensors in presence of delayed onset muscle soreness

In this study, we applied multi-channel mechanomyographic (MMG) recordings in combination with linear and nonlinear analyses to investigate muscular and musculotendinous effects of high intensity eccentric exercise. Twelve accelerometers arranged in a 3 × 4 matrix over the dominant elbow muscles were used to detect MMG activity in 12 healthy participants. Delayed onset muscle soreness was induced by repetitive high intensity eccentric contractions of the wrist extensor muscles. Average rectified values (ARV) as well as percentage of recurrence (%REC) and percentage of determinism (%DET) extracted from recurrence quantification analysis were computed from data obtained during static–dynamic contractions performed before exercise, immediately after exercise, and in presence of muscle soreness. A linear mixed model was used for the statistical analysis. The ARV, %REC, and %DET maps revealed heterogeneous MMG activity over the wrist extensor muscles before, immediately after, and in presence of muscle soreness (P < 0.01). The ARVs were higher while the %REC and %DET were lower in presence of muscle soreness compared with before exercise (P < 0.05). The study provides new key information on linear and nonlinear analyses of multi-channel MMG recordings of the wrist extensor muscles following eccentric exercise that results in muscle soreness. Recurrence quantification analysis can be suggested as a tool for detection of MMG changes in presence of muscle soreness.     

Stretching before and after exercise: effect on muscle soreness and injury risk

Reference: Herbert RD, Gabriel M. Effects of stretching before and after exercise on muscle soreness and risk of injury: systematic review. BMJ. 2002;325:468.Clinical Question: Among physically active individuals, does stretching before and after exercise affect muscle soreness and risk of injury?Data Sources: Studies were identified by searching MEDLINE (1966–February 2000), EMBASE (1988–February 2000), CINAHL (1982–1999), SPORT Discus (1949–1999), and PEDro (to February 2000). I searched the reference lists of identified studies manually until no further studies were identified. The search terms stretch, exercise, warm-up, and cool down were used in all databases except MEDLINE. In MEDLINE, an optimized OVID search strategy was used. This strategy included the terms searched in the other databases as well as terms such as flexibility, athletic injuries, sports, soreness, and muscle.Study Selection: The search was limited to English-language articles obtained from the electronic searches and the subsequent manual searches. This review included randomized or quasirandomized investigations that studied the effects of any stretching technique, before or after exercise, on delayed-onset muscle soreness, risk of injury, or athletic performance. Studies were included only if stretching occurred immediately before or after exercising.Data Extraction: Data extraction and assessment of study quality were well described. The principal outcome measures were measurements of muscle soreness and indices of injury risk. Results from the soreness studies were pooled by converting the numeric scores to percentages of the maximum possible score. These data were then reported as millimeters on a 100-mm visual analogue scale. Results of comparable studies were pooled using a fixed-effects model meta-analysis. Survival analysis using a Cox regression model was calculated on the time-to-event (injury) data.Main Results: The total number of articles identified using the search criteria was not provided; however, 5 studies on stretching and muscle soreness met inclusion and exclusion criteria. All of the studies meeting the criteria employed static stretching. One group reported the findings from 2 experiments, resulting in 6 studies meeting the inclusion and exclusion criteria. For the risk of injury, 2 studies, both investigating lower extremity injury risk in army recruits undergoing 12 weeks of basic training, met inclusion and exclusion criteria. On the basis of the PEDro scale, the methodologic quality of the studies included in the review was moderate (range, 2–7 of 10), with a mean of 4.1. For the studies on muscle soreness, 3 groups evaluated postexercise stretching, whereas 2 evaluated preexercise stretching. The participant characteristics from the 5 studies were noted to be reasonably homogeneous. Subjects in all studies were healthy young adults between the ages of 18 and 40 years (inclusive). For all studies but one, total stretching time per session ranged from 300 to 600 seconds. The exception was one study in which total stretching time was 80 seconds. Data from 77 subjects were pooled for the meta-analysis of muscle soreness outcomes at 24, 48, and 72 hours after exercising. At 24 hours postexercise, the pooled mean effect of stretching after exercise was −0.9 mm (on a 100-mm scale; negative values favor stretching), with a 95% confidence interval (CI) of −4.4 to 2.6 mm. At 48 hours, the pooled mean effect was 0.3 mm (95% CI = −4.0 to 4.5 mm), whereas at 72 hours, the pooled mean effect was −1.6 mm (95% CI = −5.9 to 2.6 mm). In each of these analyses, the results were not statistically significant in favor of either stretching or not stretching. For the studies on risk of lower extremity injury, the authors provided time-to-event (injury) data from 2630 subjects (65 military trainee platoons). These data were then combined and resulted in the allocation of 1284 subjects to stretching groups and 1346 subjects to control groups. The survival analysis identified a pooled estimate of the all-injuries hazard ratio of 0.95 (ie, a 5% decrease in injury risk; 95% CI = 0.78 to 1.16), which was not statistically significant.Conclusions: The data on stretching and muscle soreness indicate that, on average, individuals will observe a reduction in soreness of less than 2 mm on a 100-mm scale during the 72 hours after exercise. With respect to risk of injury, the combined risk reduction of 5% indicates that the stretching protocols used in these studies do not meaningfully reduce lower extremity injury risk of army recruits undergoing military training.     

Skeletal muscle vasodilatation at the onset of exercise

The mechanism for exercise hyperaemia is a century old enigma. Much of the research on the topic has focused on the factors controlling skeletal muscle blood flow during steady-state dynamic exercise. It is likely that the factors which initiate the increase in blood flow are distinct from those which sustain the elevated blood flow. There is now convincing evidence that there is rapid vasodilatation following release of muscle contraction. Metabolic, neural and acetylcholine spillover mechanisms do not appear to explain the initial dilatation. Heretofore there has been only circumstantial evidence regarding the role of potassium released by skeletal muscle fibres. Studies which interrupt potassium-mediated dilatation are just emerging and are not conclusive. In addition, the latency of the vascular smooth muscle response to potassium makes it desirable to identify a mechanism that does not rely on diffusion of a vasoactive agent. Compression of the intramuscular arterioles during contraction could activate a mechanosensitive response by the vascular smooth muscle and/or endothelium. Recent in vitro and in vivo data support the notion that brief periods of mechanical compression elicit rapid vasodilatation. Thus, vascular compression could represent a feedforward mechanism for initiating skeletal muscle vasodilatation at the onset of exercise.     

The consequences of eccentric contractions and their relationship to delayed onset muscle pain

Summary Exercise can cause muscle pain for a number of reasons. Usually the pain is experienced during the exercise and recovers rapidly afterwards. There is one type of muscle pain that has a very different and characteristic time course. In this situation the exercise itself, and the immediate post-exercise period are painfree. The pain is not felt for about eight hours and is maximal 1 or 2 days later. Delayed onset muscle pain occurs after unaccustomed, high force contractions and is particularly associated with eccentric contractions. The concensus of opinion is that the pain is caused by some form of damage, but the mechanism for the pain is not known. This review summarises the literature on the consequences of eccentric contractions and relates them to delayed onset muscle pain. There is clear evidence of damage to the muscle fibres themselves, their membranes and, at a later stage, mononuclear cell infiltration, but all these have very different time courses and none are the same as the pain. Intramuscular pressures are raised in some, but not all, painful compartments and even when raised follow a different time course to the pain. Anti-inflammatory agents do not affect the pain, but due to the incomplete understanding of the action of these drugs, the role of inflammation in delayed onset muscle pain is uncertain.Despite the considerable evidence of damage after eccentric contractions, the cause of delayed onset muscle pain is still unknown.