Introduction

Exercise-induced muscle damage (EIMD) often occurs after strenuous physical activity, particularly when the exercise has an eccentric component or is of a prolonged duration, both of these characteristics are typical of long-distance running (7,29). This phenomenon is characterized by a number of symptoms including pain, inflammation, and reduced capacity of the affected muscle to produce force (10,11). The negative symptoms associated with muscle damage are likely to affect the functional capability of the individual, resulting in a reduction in subsequent exercise performance (13). Strategies that may reduce symptoms of EIMD and enhance the recovery process are desirable, to enable the athlete to tolerate a higher training volume, frequency, or intensity (8).

Prolonged endurance running is reported to cause damage to the muscle fiber and associated structures, and this damage arises from several contributing processes (5). The initial damage is considered to be mechanical in nature resulting from repetitive loading on the muscle fibers (6). After the initial mechanical damage, a secondary inflammatory process arises that is accompanied by oxidative stress. The experience of oxidative stress can further exacerbate the initial mechanical stress in a so-called vicious cycle (4,22). Elevations in markers of muscle damage and inflammation have been observed after a marathon run (24), confirming that the event causes significant ultrastructural disruption. It may therefore be possible to apply an intervention that can effectively manage the processes associated with secondary damage, either by reducing the magnitude of damage or by accelerating the recovery process.

Knowledge regarding the potential mechanisms underpinning the efficacy of compression is limited; however, it is suggested that compression garments may be effective in reducing the swelling and inflammatory processes associated with muscle damage (20). It is suggested that the garment works by creating an external pressure gradient that reduces the space available for swelling to occur, thereby reducing the secondary inflammatory response (13). It has also been suggested that the use of compression can improve venous return, reduce venous pooling, and enhance the removal of metabolites, this is perhaps because of an enhanced muscle pump function (1,26). Previous research has observed reduced perceptions of muscle soreness; (1,13), reduced concentrations of serum creatine kinase (CK) (1,13), and a reduced inflammatory response (17,28) with the use of compression garments. In contrast, research has also demonstrated that compression garments have no effect on muscle soreness (2,17), CK concentration (2,13), lactate dehydrogenase concentration (13), and thigh girth (13). Although the physiological and biochemical effects of wearing compression garments remain poorly understood, the positive claims associated with the garments may have led to an increase in the use of compression garments in sport.

Differences in experimental design including exercise modality, duration of the application of compression, and the participant's training status may explain some of the inconsistencies within the literature. Furthermore, the majority of studies have focused on power sports (14,16,27). Participation in endurance events such as marathon running is increasing in popularity, and the use of compression garments as training aids is also increasing (14). Thus, there is a need to focus on the efficacy of compression garments on recovery in endurance-based sports. To the knowledge of the authors, the use of compression after prolonged endurance running has not been examined. Accordingly, the purpose of this study was to investigate the effects of wearing a commercially available lower limb compression garment on the recovery of strength, soreness, and indices of muscle damage after a marathon run.

Methods

Experimental Approach to the Problem

Subjects were required to complete a 26.2-mile self-paced run in an outside environment. Subjects could select when to complete the marathon on 1 of 3 dates, the course remained the same on each date. The mean environmental conditions for the 3 days were a barometric pressure of 762 ± 12 mm Hg (750–771 mm Hg), an air temperature of 9 ± 2° C (6–10° C), a wind speed of 16 ± 4 km·h−1 (12–20 km·h−1), and a relative humidity of 73 ± 6% (66–77%). At least 7 days before the marathon run, subjects reported to the laboratory to complete a submaximal lactate profile and a maximal exercise test on a treadmill (H/P Cosmos Pulsar 4.0; H/P Cosmos Sports and Medical, Nussdorf-Traunsdein, Germany) to characterize the physiology of the group and establish baseline data. The submaximal lactate profile consisted of a series of stages each lasting 3 minutes with 30 seconds rest between each stage to enable the collection of a blood lactate sample, the sample was immediately analyzed using an automated analyzer (Biosen C-Line; EKF Diagnostic, Ebendorfer Chaussee 3, Barleben, Germany). At the start of each new stage, the treadmill speed was increased by 1 km·h−1, heart rate (Polar A1; Polar Electro OY, Kempele, Finland) was recorded throughout the test, and a 1 minute average was taken during the last minute of each stage. Ratings of perceived exertion were assessed using the Borg scale. Subjects were asked to indicate their perception of exertion on a scale ranging from 6 (very, very light) to 20 (very, very hard) during the last 30 seconds of each stage. Expired air was analyzed continuously using an online gas analyzer (Jaeger Oxycon Pro; Jaeger Ltd., Hoechberg, Germany). The submaximal test was terminated when blood lactate concentration exceeded 4 mmol·L−1. The participant was given 10 minutes rest before commencing the maximal exercise test. The test began 2 km·h−1 slower than the finishing speed of the submaximal test. Throughout the test, the treadmill speed remained constant, and the gradient was increased by 1% every minute. The test was terminated when the participant reached volitional exhaustion. Expired air was analyzed continuously, and maximal oxygen uptake (V[Combining Dot Above]O 2 max) was determined as the highest 30-second average. Verbal encouragement was given throughout. Subjects were matched based on V[Combining Dot Above]O 2 max and then were randomly assigned to a compression garment group (compression) or a sham ultrasound group (sham). Dependent measures included perceived muscle soreness, maximal voluntary isometric contraction (MVIC) of the knee extensors, CK, and C-reactive protein (C-RP) and were assessed immediately before the marathon, within 1 hour after marathon, and at 24, 48, and 72 hours after marathon.

Subjects

After approval from the University's research ethics committee, in accordance with the Declaration of Helsinki, 24 recreational marathon runners (male, n = 17; female, n = 7) volunteered to participate in this investigation. All subjects completed a health screening questionnaire and gave written informed consent. Participant characteristics, marathon time, and marathon history are presented in Table 1. Subjects were asked to refrain from heavy exercise in the 48 hours preceding the marathon. Subjects were also asked to refrain from using any recovery strategy, such as water immersion, non-steroidal anti-inflammatory drugs, massage, and alcohol consumption for the duration of the study.

Table 1: Descriptive characteristics of the participants in the compression and ultrasound groups.*

Treatment Groups

The sham group received 15 minutes (5 minutes of quadriceps, 5 minutes of hamstrings, and 5 minutes of gastrocnemius) of sham ultrasound (Combined therapy ultrasound/inferential; Shrewsbury Medical, Shropshire, United Kingdom) within 1 hour of the completion of the marathon run. A water-soluble hypoallergenic ultrasound gel (Aquasonic 100 ultrasound transmission gel; Parker Laboratories, Fairfield NJ, USA) was applied to the leg, and the ultrasound head was used to spread the gel over the skin in circular patterns. The ultrasound unit was turned off throughout the duration, and the unit was obscured from view. The compression garment group was given a pair of compression tights (2XU, MA1551b men's compression tights and WA1552b women's compression tights, Melbourne, Australia) fitted according to the manufacturer's instructions. Subjects were instructed to shower and put on the garments within 1 hour of the completion of the marathon run. The garments were worn for 72 hours after the run, subjects were asked to wear them continuously, only removing them to shower. The degree of pressure exerted on the leg was measured using a body pressure–measuring device (Kikuhime; TT Medi Trade, Søleddet, Denmark). Pressure was measured at the medial aspect of the calf at the site of maximal girth and also at the front thigh at the midpoint between the inguinal crease and the superior aspect of the patella. Pressure measurements at each site were taken with the subject standing in the anatomical position and also during a contraction of each muscle group. Measurements were repeated 3 times with the mean value recorded.

Dependent Variables

Muscle soreness was obtained using a 200-mm visual analog scale with “no pain” at 0 mm and “unbearable pain” at 200 mm (24). Subjects stood with their feet shoulder width apart with hands on hips and were asked to perform a squat to 90° and return to standing and mark their subjective feeling of pain on the scale. Maximal voluntary isometric contraction was assessed using a strain gauge (MIE Medical Research Ltd., Leeds, United Kingdom). Subjects were seated on a platform, with their hip and knee joints flexed at 90°. The strain gauge was attached 2 cm above the malleoli of the left ankle. Subjects were asked to maximally extend the knee against the device for 3 seconds. Each participant was given 3 maximal attempts each separated by 1 minute, the highest of which was recorded as MVIC. Verbal encouragement was given (23).

Serum CK and C-RP were measured at each time point. Approximately 8.5 ml of blood was collected from the antecubital fossa into serum separation vacutainers (BD Vacutainer Systems, Plymouth, United Kingdom). After collection, the sample was immediately placed in a refrigerated centrifuge (Mikro 220R D-78532, Tuttlingen, Germany) and spun at 3,500 rpm, a relative centrifugal force of 3,000g, for 20 minutes at 4° C to enable the separation of serum. The serum was immediately frozen at −80° C for later analysis.

Creatine kinase was analyzed in duplicate using an automated clinical chemistry analyzer (Modular P; Roche Diagnostics, West Sussex, United Kingdom). C-reactive protein was analyzed in duplicate from serum samples using a high-sensitivity C-reactive protein ELISA kit (Kalon Biological, Guildford, United Kingdom). The absorbance of each sample was read at 405 nm (Biochrom Ltd., Cambridge, United Kingdom).

Statistical Analyses

All data analyses were carried out using SPSS for Windows version 18, and values are reported as mean ± SD. An independent samples t-test was used to identify any differences in group characteristics at baseline. To account for interindividual variation, MVIC was expressed as a percentage change from baseline. All dependent variables were assessed using a treatment by time repeated-measures analysis of variance. Maulchy's test of sphericity was used to check homogeneity of variance for all analysis. The Greenhouse-Geisser correction factor was used where violations of the assumption occurred. Where a significant effect was observed, interaction effects were further examined using an LSD post hoc analysis. A significance level of p ≤ 0.05 was applied.

Results

The mean pressure of the garment exerted on the front thigh was 9.9 ± 2 mm Hg in the anatomical position and 17.5 ± 3.5 mm Hg during muscle contraction. The mean pressure exerted on the calf was 19.3 ± 2.6 mm Hg in the anatomical position and 24.4 ± 5 mm Hg during muscle contraction. There were no significant differences in V[Combining Dot Above]O 2 max, marathon history, average weekly training distance, and marathon finish time between groups (Table 1). All dependent variables showed a significant time effect (p ≤ 0.004).

Muscle soreness exhibited a significant time by group effect (F (4,1) = 30.8, p < 0.001) and a significant group effect (F (1,22) = 4.451, p = 0.046), with those in the compression group experiencing reduced muscle soreness (Figure 1). A post hoc LSD test indicated that this difference occurred at 24 hours after exercise in the compression group. At this time point, the sham group increased in mean soreness from 26.8 to 36.4 mm, whereas the compression group decreased in mean soreness from 31 to 13.9 mm.

Figure 1: Perceived rating of muscle soreness for the compression and sham groups before and after the marathon. *Significantly different from compression group (gray lines denote individual participant results and black line denotes the group mean withSD values).

Postmarathon concentrations for CK were elevated at 24 and 48 hours after exercise, with the highest values occurring at 24 hours (692.1 ± 625.6 and 1022.3 ± 1439 U/L in the compression and sham groups, respectively). C-reactive protein concentrations were also elevated at 24 and 48 hours after marathon, with the highest values occurring at 24 hours after marathon (7.4 ± 4.6 and 10.3 ± 9.0 mg·L−1 in the compression and sham groups, respectively); however, there was no significant difference between groups for either marker (p ≥ 0.05; Figures 2 and 3).

Figure 2: Serum C-RP values for the compression and sham groups before and after the marathon. No significant differences were observed between treatment groups (gray lines denote individual participant results and black line denotes the group mean withSD values). C-RP = C-reactive protein. Figure 3: Serum CK values for the compression and sham groups before and after the marathon. No significant differences were observed between treatment groups (gray lines denote individual participant results and black line denotes the group mean withSD values). CK = creatine kinase.

Maximal voluntary isometric contraction (MVIC) was reduced immediately after marathon, returning to normal at 72 hours after marathon. The largest measured decrease in MVIC occurred immediately after the marathon (82.8 ± 13.9 and 77 ± 14.8 percent of max in the compression and sham groups, respectively); however, no significant group effect (F (1,22) = 2.256, p = 0.124) or interaction (F (4,1) = 0.688, p = 0.543) was observed (Figure 4).

Figure 4: Percentage change in MVIC for the compression and sham groups before and after the marathon. No significant differences were observed between treatment groups (gray lines denote individual participant results and black line denotes the group mean withSD values). MVIC = maximal voluntary isometric contraction.

Discussion

To the authors' knowledge, this was the first investigation to examine the efficacy of compression garments in accelerating recovery from endurance running. It was hypothesized that the use of lower limb compression garment would enhance the recovery process after a marathon run. Those in the compression garment group experienced less muscle soreness 24 hours after marathon when compared with the sham group. Despite this finding, there were no significant differences between groups for MVIC, CK, and C-RP; however, there seems to be a trend for improved recovery of MVIC and an attenuation of CK and C-RP in the compression group.

The main finding of this study was that the use of a lower limb compression garment significantly reduced muscle soreness 24 hours after a marathon run (Figure 1). This finding is consistent with other studies that have demonstrated that the use of compression garments results in reduced perceived muscle soreness after damaging exercise (1,13). The experience of muscle soreness is proposed to arise from mechanical trauma to the tissue, giving rise to structural damage and an inflammatory response (12). Therefore, a reduction in soreness may be related to reduced structural damage to the tissue and/or a reduced inflammatory response (1). It is suggested that the application of compression may be effective in reducing this inflammatory process; this may be because compression garments create an external pressure gradient reducing the space available for swelling, hemorrhage, and hematoma (13,20). The chain of events that occur after initial mechanical damage to the muscle fibers can result in an increased osmotic pressure within the tissue, which causes an efflux of fluid from the capillaries into the interstitial spaces (20). The application of compression may lessen the change in osmotic pressure and consequently reduce inflammation, the circulation of inflammatory markers, and the sensation of pain (20). Although this study controlled for a placebo effect by using sham ultrasound, it is possible that the finding of reduced perceived muscle soreness may be linked to the participant's belief that compression garments have a positive response on recovery.

C-reactive protein is a marker of inflammation that has been proposed to reflect the inflammatory load on the body (30). Concentrations of C-RP were elevated after the marathon run, peaking at 24 hours after marathon (Figure 2), which is consistent with previous research (24). There was no significant group effect observed on concentrations of C-RP. Few studies investigating the use of compression garments have measured C-RP; those who have measured this marker have also found no significant effect of compression on concentrations (15). However, several have looked at mid-thigh girth as an indirect measure of inflammation, one such study observed no time or group effect with mid-thigh girth after the application of compression (13). These data differ from the findings of an earlier study that observed an increased thigh circumference in a contrast bathing group and a control group but no increase in thigh circumference in a compression garment group, after a bout of damaging exercise (17). Given that there were no significant reductions in the inflammatory marker C-RP, the reduction of soreness is unlikely to be linked to a reduction in the inflammatory response.

Similarly to C-RP, this study observed no group effect for CK. Creatine kinase, an enzyme that leaks from damaged muscle tissue into the blood stream resulting in an elevated serum concentration of CK (9), is frequently used as a marker of muscle damage. A peak increase in concentration is usually observed 24 hours after exercise with levels remaining elevated at 48 and 72 hours after exercise (9). The CK concentrations observed in this study follow the well-established response to damaging exercise. The concentration of CK was elevated immediately after the marathon run, peaking at 24 hours after exercise. The concentration of CK continued to remain elevated at 48 and 72 hours after exercise (Figure 3). This indicates that the marathon run induced a significant amount of tissue damage. Although it seems that there was a trend for higher concentrations of CK in the sham group, this difference was not statistically significant. This apparent trend is consistent with the findings of previous studies that have found reduced concentrations of CK in those wearing compression garments compared with those in a control group (13,14,18).

Training status is a key factor that may explain why this study has not observed a reduction in CK or C-RP when compared with previous research. Well-trained individuals tend to exhibit lower concentrations of CK after a bout of damaging exercise when compared with their less-trained counterparts (9). This is a reported benefit of the repeated bout effect that suggests that a bout of damaging exercise offers protection against future bouts of damaging exercise whereby the individuals experience less-severe symptoms of EIMD (25). The average number of previous marathons completed by the subjects taking part in this study was 16 ± 24 suggesting that they were experienced marathon runners; it is therefore possible that the marathon and training history of the subjects in this study offered protection in the form of an adaptive response.

Previous studies that have indicated a lowered CK concentration after the application of compression have used club level (14) or university level (13) game players who may not be familiar with high training volumes. Howatson etal. (24) observed much higher values of CK (2,814 compared with 1,022 U/L in the placebo groups) and C-RP (27 compared with 10 mg/L in the placebo groups) after a marathon race compared with this study. Higher values of these markers would indicate a greater degree of muscle damage occurred; this could be related to marathon history as the average number of competed marathons for the subjects taking part in Howatson et al. (24) was 6 ± 8 where the average number of completed marathons for the subjects taking part in this study was 16 ± 24, indicating that the subjects in this study were more experienced. It is possible that the potential of the garment to have a beneficial effect is attenuated with a lower magnitude of change in markers of muscle damage and inflammation. This is perhaps why, in this study, there was a trend for reduced concentrations of CK and C-RP but no significant effect.

The use of compression garments did not improve the recovery of muscle force production after a marathon run (Figure 4). This is consistent with the findings of others (14,15). The effects of compression on contractile performance are unclear; it is thought that any improvement or recovery in muscle strength may be related to contractile function. The decrease in MVIC observed immediately after the marathon run may be because of both localized muscle trauma and peripheral muscle fatigue, resulting from the accumulation of H+ ions that will inhibit excitation-contraction coupling (19). The results of this study indicate that, despite the use of compression, the recovery of voluntary muscle function was not improved. It has previously been suggested that equivocal responses in performance standards after the use of a recovery strategy may be because of training status (17). Experienced athletes are more accustomed to the discomfort associated with high-intensity exercise and are better able to reproduce performances (17).

One current argument surrounding the use of commercially available compression garments is whether they can exert enough pressure to be of any benefit (13). In contrast to this research has also suggested that garments exerting high levels of compression (23–32 mm Hg) are not as effective at maintaining leg power as garments exerting low (12–15 mm Hg) or medium (18–21 mm Hg) pressures (3). The pressures observed within this study ranged between 9.9 and 24.4 mm Hg. The fitting of these garments is often based on the manufacturer's guidelines; however, because of differences in body size and tissue structure, the range of sizes available may not be sufficient. Although we measured the degree of compression exerted in this study and our compression level was similar to that achieved in other studies (1,21), more research is needed to ascertain the optimal degree of compression in the recovery from symptoms of EIMD and how the degree of compression varies between individuals wearing the same size garments.

In conclusion, it would seem that the use of a lower limb compression garment, after a marathon run, results in significantly lower perceived muscle soreness at 24 hours after marathon. In addition, the garment had no statistically significant effect on improved recovery of muscle performance or postexercise removal of serum markers of muscle damage and inflammation. However, despite the lack of a statistically significant effect in these markers, a trend for improvement was apparent in the compression group.

Practical Applications

A variety of modalities are frequently used to accelerate recovery from strenuous exercise. A number of investigations have indicated that the use of compression garments may help recovery after damaging exercise (1,13,20). The observation of reduced muscle soreness in this study may have implications for a number of populations, wishing to embark on exercise regimes, who are discouraged because of the experience of soreness. As such compression garments may be of use as a recovery aid when worn during the 24 hours after exercise to reduce the experience of perceived muscle soreness. Although this study investigated the effects of compression in experienced, but nonetheless recreational runners, further research should look to identify whether significantly greater effects are observed in less-experienced runners.

Acknowledgments

The authors thank the subjects for their commitment throughout the completion of this project. The authors also thank Rik Mellor, Hayley Legg, Hayley Morgan, Kylie Ilston, Nicola Brown, Natasha Mistry, Ammi King, Mel Bradley, Hilary Davies, John Pattison, Sunny Pottay, Steve Hiorns, Marcus Docker, Ross MacGregor, and Richard Burden for their valuable help on the day of the marathon. Finally, the authors thank St Mary's University College School Research Fund for supporting this project. This research investigation was carried out in compliance with the ethical laws of Great Britain, and the authors have no conflicts of interest that are relevant to the content of this article. The results of this study do not constitute endorsement of the product by the authors or the NSCA.