Introduction
Athletes continue to search for ergogenic aids that can enhance performance during competition and training so as to gain an advantage over their opponents (3). Competitive runners have worn graduated compression stockings (GCS)-a form of mechanical ergogenic aid-during races to enhance their potential to run faster. Despite the scarcity of scientific research, world records have been set wearing GCS for 20 km (Lornah Kiplagat, 1:02:57, October 14, 2007, Udine, Italy) and treadmill marathon performance (Michael Wardian, 2:23:58, December 11, 2004, Arlington, TX, USA). Though these world record performances were undoubtedly the combination of exceptional athletic talent and comprehensive training, the runners' choice to wear GCS indicates these athletes place considerable faith in their performance effects.
In support of anecdotal claims made by athletes and manufacturers, previous research suggests that there may be some performance benefits from using compression garments. Recreational athletes ran 5-km races faster wearing elastic tights (30 mm Hg at the ankle) than without tights (9); the authors suggest that the compression tights improved the stride length of the runners, which resulted in the 2.3% better performance. Further, moderately trained athletes demonstrated improved running performance, as shown by time under load, total work, and maximum speed, when wearing compression stockings (15). Kemmler et al. (15) did not provide a specific mechanism for the improvement in performance but suggested it could be because of improved aerobic efficiency (8) or some other biological or biomechanical effect of compression. However, the participants in these studies were not blinded to the experimental procedures, so there remains the possibility of ‘placebo’ effects improving performance.
During competition, endurance runners need to maintain muscle power for high-intensity or sprint exercise, and some studies have reported that muscle power may be enhanced when wearing compression garments (11,16). Track athletes showed improved countermovement jump (CMJ) height while wearing compression shorts as opposed to loose-fitting gym shorts (11). Moreover, athletes and nonathletes wearing graduated compression shorts demonstrated improved vertical jump height after endurance exercise, possibly as a result of improved proprioception (16). However, single and repeated-sprint performances were not altered by wearing compression garments (11,12), so the relationship between compression garments, jumping and sprinting performance remains to be clarified. Nevertheless, no studies have examined the impact of wearing GCS during fast-paced running on muscle power.
Previous investigations have used garments with a range of compression levels. However, no study has attempted to examine the effects of varying grades of compression on running or jumping performance in endurance athletes. Moreover, no study has attempted to examine the effect of graduated compression per se by using an appropriate control garment. Though clinical trials recommend compression at the ankle between 15 and 30 mm Hg (that dissipates to the knee) this may not be appropriate for healthy athletes. Indeed, Lawrence and Kakkar (18) showed that increasing compression to 30 mm Hg at the ankle caused too much compression and decreased subcutaneous blood flow and deep-vein velocity, possibly via a tourniquet effect. Therefore, this may have an impact not only on blood flow but also on the comfort of the athlete, which may result in an ergolytic effect on the individual. Nevertheless, the possibility also exists that a comfortable stocking may not necessarily be the most effective garment for performance.
Therefore, the main aim of this study was to examine the effects of wearing different grades of GCS on 10-km running performance in well-trained athletes. A secondary aim was to assess the effects of wearing GCS on various physiological and perceptual responses after exercise.
Methods
Experimental Approach to the Problem
This study used a randomized counterbalanced design, which was blinded to both the participants and experimenters, to examine the effect of wearing GCS on 10-km running performance in well-trained runners. We used a within-subjects design that enabled subjects to act as their own control. Subjects wore different grades of GCS to investigate dose-response issues, and a control garment (no compression) was used to offset ‘placebo’ effects.
Subjects
Twelve participants provided informed consent to take part in this study, which complied with the Massey University Human Ethics Committee guidelines. All participants completed and signed health screening questionnaires before beginning any exercise tests. The athletes were well-trained, competitive male and female runners who were (mean ± SD) 33 ± 10 years old, 68.5 ± 6.2 kg in body mass, 1.74 ± 0.06 m in stature, and had a o2max of 68.7 ± 5.8 ml·kg−1·min−1. The participants competed regularly in 800 m to marathon distances during the previous 12 months. Run training time ranged from 7 to 16 h·wk−1, interspersed with competitive events. No participants suffered from deep-vein thrombosis, varicose veins, or other vascular illnesses. The personal best times for 10 km were (mean ± SD; minutes:seconds) 37:30.4 ± 2:00.4 (men) and 40:52.2 ± 3:23.4 (women).
Procedures
Preliminary Procedures
Participants completed a concurrent o2max and lactate test protocol within 2 weeks of beginning the first trial. Leg measurements were taken to ensure that participants received the correct stocking size for each time trial run. The GCS worn by each participant during the time trials was determined by a partial counterbalanced design that was double blinded to the experimenters and participants. Participants were also familiarized with the correct CMJ technique. An experimenter described and demonstrated the correct movements and stressed the importance that each attempt was a maximal effort. The perceptual scales used during the study were explained to participants so as to ensure they gave correct answers for subjective perception.
Compression Garments
The compression garments were knee-high stockings that provided greatest compressive pressure at the ankle, which gradually dissipated to the knee (Julius Zorn GmbH, Aichach, Germany; Figure 1). The correct fit for each participant was determined (according to the manufacturer's guidelines) by measuring the distance from the ground to the popliteal line behind the knee, the leg circumference immediately below the knee, the leg circumference at the widest part of the calf and leg circumference at the narrowest part of the ankle. Participants donned the GCS by turning the stocking inside out and rolling the sock over the toes, foot, and leg. The stocking was adjusted so that the top was flush below the knee and above the calf muscles. Any bunching was smoothed over to prevent a tourniquet effect. Four different types of stocking were used. The stocking used for the familiarization (Fam) and control (Con) trials was designed to have minimal compression at the ankle or calf (0 mm Hg). The 3 types of GCS used were designated as low (Low), medium (Med), and high (Hi) grade compression (Table 1). The different compression grades at the ankle and calf were achieved by the length, width, and weave of the garment; tighter weave produced greater compression around the leg tissues.
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Figure 1: Graduated compression stockings (GCS) correctly fitted over legs, flush under the knee, and smoothed to avoid bunching.
Table 1: Compression applied by GCS at the ankle and below the knee according to the manufacturer's guidelines when fitted correctly.*
Countermovement Jumps
Countermovement jump performance was measured pre and postrun to estimate changes in leg power. Participants were instructed to step on to a jump mat (Just Jump, Probotics Inc. Huntsville, AL, USA), place their hands on their hips, and use a countermovement to optimize jump height. Three maximal-effort jumps were performed by participants with the best jump used for comparison with postrun CMJ. All CMJ efforts were separated by at least a 10-second rest.
Perceptual Measures
The Feeling Scale (FS) was used to measure the level of pleasure or displeasure before and after exercise using an 11-point scale ranging from −5 (very bad), 0 (neutral), to +5 (very good) with markers at each odd integer (13). The Felt Arousal Scale (FAS) was used to measure participants' level of arousal-activation before and after exercise using a 6-point scale that ranged from 1 (bored, apathetic, tired) to 6 (excited, angry, energetic (19)). The ratings of perceived exertion (RPE) scale was used to measure how hard the participants perceived they were running during the trials, ranging from 6 (very, very light) to 20 (very, very hard (7)). A number of other Likert scales were used to assess the comfort, tightness, and (where applicable) any induced pain from wearing GCS (1). Responses for each factor ranged from 1 (very uncomfortable, slack, no pain) through to 10 (very comfortable, very tight, very painful).
Experimental Procedures
Five 10-km time trials (1 familiarization and 4 main trials) were run on an artificial surface outdoor 400-m track interspersed by at least 7 days of recovery. All participants were advised to prepare for the trial with the same routines they followed before a running race and to maintain consistency with their preparation in the 48-hour period leading up to each trial. An 8-week testing period was booked to allow for wet weather, high wind speeds, or extenuating circumstances preventing participants from running the time trials. If track conditions were wet or wind speeds exceeded 5 m·s−1 the participants were informed of an alternative testing date. Participants arrived at the same time and day of the week for each time trial 20 minutes before they were due to start the run. During this period the participants were fitted with a pair of GCS, a downloadable heart rate (HR) monitor (Polar Team System, Polar, Kempele, Finland), and reported perceptual ratings. Participants were allowed a 10-minute warm-up (consisting of running and stretching) period before the assessment of CMJ. Blood lactate (La−) concentration was measured from finger-prick samples (Lactate Pro, Arkray Inc. Kyoto, Japan) immediately before beginning the time trial run. Environmental conditions including wind speed, wind direction, ambient temperature, relative humidity, and barometric pressure were recorded using a portable weather station (Kestrel 4500 Portable Weather Tracker, Neilsen-Kellerman, Boothwyn, PA, USA).
Each participant was started for the 10-km run individually and separated from the next runner by a 60-second gap in order from slowest to fastest. The runners were separated to avoid pacing strategies affecting performance time. Athletes were also given incentives for achieving a personal best time or gift rewards for finishing ahead of the runner who started in front of them. During the run, HR was recorded every 5 seconds and lap counters recorded splits for every 400 m. Run time was measured with 2 stopwatches to ensure the correct finishing time. Participants received feedback about the number of laps they had completed but not HR or lap time information.
Immediately after completing the run, participants' blood La−, leg power, and perceptual ratings were determined. The starting times and participant running order was unchanged between trials. No performance feedback was given to participants until after the final trial.
Statistical Analyses
Data collected for all measured variables were compared between trials using 1-way or 2-way repeated-measures analysis of variance (ANOVA, SPSS version 15.0). Mauchly's test of sphericity was used to identify when sphericity was violated. When the assumption of sphericity was violated, the Huynh-Feldt correction was used. Delta change values between groups comparing pre and postrun measures were also assessed using 1-way ANOVA. When significant differences between GCS interventions were identified paired t-tests, using the Holm-Bonferroni adjustment, were applied. Relative effect sizes for performance data were calculated using Cohen's d and defined as small (d = 0.2), medium (d = 0.5), or large (d = 0.8). The coefficient of variation (CV) was calculated to indicate within-participant variation between the familiarization and Con trials. Correlations between variables were verified using simple linear regression equations and reported as Pearson's correlation coefficient. Data are presented as mean ± SD (unless otherwise indicated) and statistical significance was set at p ≤ 0.05.
Results
Time trials were run at an average temperature of 18°C (14-22°C), 71% humidity (53-94%), 2.1 m·s−1 wind speed (0.5-5.0 m·s−1), on a dry 400-m synthetic track under sunny or overcast conditions at the same time of day (18:00-20:00 hours). The average group run time for the Fam trial (minutes:seconds, wearing control GCS) was 39:38; the CV between Fam and Con was 1.6%. No order effect was observed between GCS conditions.
Performance Data
No significant differences were observed between interventions for 10-km performance time (minutes:seconds; Con 39:50 ± 4:58, Low 39:26 ± 3:57, Med 39:41 ± 3:46, Hi 39:51 ± 4:01; p = 0.99; Cohen's d < 0.10; Figure 2).
Figure 2: Performance time for participants completing 10-km time trials wearing different graduated compression stockings (GCS); filled bars show mean ± 95% CI, whereas lines represent individual responses; Con (control); Low (low-grade GCS); Med (medium-grade GCS); Hi (high-grade GCS).
The 2-way ANOVA performed on the CMJ data revealed no main effects of treatment or time (Table 2). However, the change in CMJ from pre to postrun was significantly lower in Con (−2.9 ± 3.9 cm) than Low (+1.2 ± 6.0 cm; p < 0.05; Cohen's d = 0.63) and Med (+1.7 ± 4.8 cm; p < 0.05; Cohen's d = 1.03) but not Hi GCS (−0.6 ± 5.3 cm; Figure 3).
Table 2: Maximum countermovement jump height achieved over 3 attempts before and after 10-km time trial running wearing different GCS.*†
Figure 3: Change in countermovement jump height from pre- to post-10-km time trial runs; filled bars show mean ± 95% CI, whereas lines represent individual responses; Con (control); Low (low-grade GCS); Med (medium-grade GCS); Hi (high-grade GCS); *Significant mean difference when compared with Con, p < 0.05.
Physiological Data
The mean HR was not significantly different between trials (168-169 b·min−1; Table 2). There was a main effect of time for La− that changed significantly from prerun to postrun measures in all trials (p < 0.001); however, there were no differences between trials (Table 3).
Table 3: Changes in La− (mmol·L−1) from pre- to post-10-km run and heart rate at each 2-km mark of the time trial run.*†
Perceptual Data
Ratings of perceived exertion was not significantly different between trials. Participants consistently reported ratings of 16-18 at the end of the run (17 = very hard; Table 4). There were no significant time or treatment effects for ratings of pleasure-displeasure (FS) or perceived activation (FAS). Feelings of pleasure-displeasure for running were rated as neutral (between 0 and 1) for pre and postexercise in each trial. Participant ratings of activation and pleasure-displeasure were similar between control and GCS trials.
Table 4: Subjective RPE, pleasure/displeasure (FS), and perceived activation (FAS) experienced by participants during each trial.*†
There was a main effect of treatment for perceptions of GCS comfort (p < 0.05). Specifically, Con was more comfortable than Med and Hi (p < 0.05) and Low was comfortable than Med (p < 0.05) and Hi (p < 0.05; Figure 4). There was no main effect of time indicating that GCS comfort did not change from pre to postrun. There was no correlation between perceived comfort and 10 km run time (r = 0.15; p = 0.31) or jump performance (r = 0.18; p = 0.21).
Figure 4: Ratings of perceived comfort (mean ± 95% CI) when wearing graduated compression stockings (GCS) recorded pre- and post-10-km running time trials; Con (control); Low (low-grade GCS); Med (medium-grade GCS); Hi (high-grade GCS).
There was a main effect of treatment for ratings of perceived tightness of GCS (p < 0.001; Figure 5). Post hoc analyses revealed Hi was perceived as tighter than all other groups (p < 0.05) and Med was tighter than Low and Con (p < 0.05). There was no statistically significant difference between Con and Low. There was no main effect of time indicating tightness ratings remained consistent throughout each trial. There was a weak negative correlation between ratings of tightness and jump performance (r = −0.312; p < 0.05) but not run time (r = 0.21; p = 0.15).
Figure 5: Ratings of perceived tightness (mean ± 95% CI) when wearing graduated compression stockings (GCS) recorded pre- and post-10-km running time trials; Con (control); Low (low-grade GCS); Med (medium-grade GCS); Hi (high-grade GCS).
There were main effects of time (p < 0.05) and treatment (p < 0.001) for perceptions of pain wearing different GCS. Post hoc tests showed that Hi induced more pain than Con and Low (p < 0.05), and Med induced more pain than Con and Low (p < 0.05; Figure 6). There was a weak negative correlation between ratings of pain and jump performance (r = −0.297; p < 0.05) but not run time (r = 0.13; p = 0.40).
Figure 6: Ratings of perceived pain (mean ± 95% CI) when wearing graduated compression stockings (GCS) recorded pre- and post-10-km running time trials; Con (control); Low (low-grade GCS); Med (medium-grade GCS); Hi (high-grade GCS).
Discussion
The aim of this study was to examine the efficacy of wearing different grades of compression stockings (GCS) on 10-km running performance in well-trained runners. There was no effect of wearing different GCS on performance time when compared with a non-GCS control. However, vertical jump height was better maintained from pre to postexercise when wearing Low (12-15 mm Hg) and Med (18-21 mm Hg) relative to Con (0 mm Hg). Furthermore, subjective perceptions of comfort, tightness, and pain were most favorable during Low and Con trials.
Participants underwent 2 10-km runs wearing the control (0 mm Hg) garment (Fam and Con) so that they were fully familiarized with the experimental procedures and so that a measure of reliability could be obtained. The CV of 1.6% indicated that the 10-km run was a reliable measure of performance (14). However, there was no difference in run times between trials (Figure 2). In contrast, other studies have shown improved running performance when subjects wore compression garments (9,15). However, these studies used moderately trained athletes and did not use an appropriate control garment. Although elite athletes continue to wear GCS during competition and training (indeed some world records have been set when wearing GCS) our results suggest that GCS do not affect endurance running performance in well-trained runners.
Countermovement jump height from pre to postrun was increased when wearing Low (+3.6%) and Med (+4.9%) GCS but decreased when wearing Con (−8.5%). Greater jump height postrun may indicate improved muscle power maintenance (16,17); however, running speed was not measured for the finishing straight of the run. Therefore, any beneficial effects of maintenance of leg power toward the latter stages of endurance exercise when wearing low-medium grade GCS remain speculative and thus warrant further research.
The reduced jump height postrun during Con could be because of fatigue affecting the contraction-coupling process within the muscle (2), skeletal muscle damage because of repeated contractions and impact causing shear forces (e.g., tearing; [4]), or altered neuromuscular activity. In contrast, CMJ was improved postexercise wearing Low and Med GCS suggesting that muscle function was better maintained during these trials. The GCS may have enhanced proprioceptive mechanisms related to jumping skills (16) or reduced muscle oscillations that lead to muscle exhaustion or damage (11) and therefore maintaining CMJ performance. This is supported by some studies showing reduced postexercise creatine kinase levels during trials when graduated compression garments are worn compared with control (10). Further, Ali et al. (1) showed significant reductions in muscle soreness ratings 24 hours post fast-paced running when wearing GCS. Alternatively, the elasticity of the Low and Med GCS may have improved flexion-extension torque around the ankle joint similarly to the elasticity observed by Doan et al. (11) at the hip joint that allowed a greater jump performance when compression shorts were worn. Although the results of the present study do not provide mechanisms for the greater CMJ during the Low and Med trials, they do indicate that leg muscle function is better maintained after intense endurance exercise using these GCS. Further investigation is required to determine why there was a better maintenance of leg power for participants wearing Low and Med GCS compared with Con.
Another claim purported by many GCS manufacturers is improved removal of blood La−. In the present study, La− samples taken immediately postrun were not different between trials. Some reports have shown that GCS result in reduced postexercise blood La− (6,10), whereas others show no influence of compression garments on La− (5,12). The time trials in the present study were all maximal efforts, and this may explain the similar postrun blood La− values across trials. In these healthy well-trained runners, the muscle pump may be adequate in removing La− anyway thus not necessitating the use of an aid to help this function. Nevertheless, to determine if GCS have any affect on blood La−, further studies should control exercise intensity to determine if there are any differences in the blood La− response during constant load exercise, because the blood La− during the time trials may have been affected by the performance times and pacing strategies the runners used. However, the present study shows that GCS do not affect the immediate postexercise blood La− response during a 10-km time trial in well-trained runners.
Exercising heart rate was not altered by wearing GCS (Table 3). Ali et al. (1) also reported no differences in heart rate in the GCS trial (compared with control) in moderately trained athletes. However, that study did not use a maximal-effort protocol and attempted to pace the participants. There were also no differences in heart rate between graduated compression tights and the control condition during repeated-sprint (12) or endurance (5) exercise. The current investigation required maximal efforts in each 10-km run, and heart rate was the same across all trials, thus indicating that GCS are unlikely to alter venous return in well-trained athletes-possibly because of adequate functioning of the muscle pump in these healthy athletes. However, research using controlled constant pace exercise and more direct measurement techniques are required to examine this further.
All participants reported a similar effort for each trial because there were no significant changes in RPE, FS, or FAS between conditions. The perceptual scales provide a reflection of subjective intensity and, coupled with the physiological measures, the indication is that all participants had performed at the same intensity across all trials. However, the Con and Low garments were rated most comfortable by the runners. Participants could also successfully perceive different GCS grades based on feelings of perceived tightness despite being blinded to the intervention they were assigned to. Hi GCS had no measured physiological effect when compared with the other interventions but showed a weak negative correlation with CMJ performance and higher pain ratings than other garments. Because the change in jump height from pre to postexercise was influenced by the grade of GCS, and Low and Med GCS were preferred by the participants, this highlights the importance of choosing the appropriate garment for well-trained athletes.
Practical Applications
This is the first study that compares the effects of wearing different grades of GCS on running performance relative to a control garment. Wearing GCS had no effect on 10-km time trial performance for well-trained athletes. However, CMJ height was better maintained from pre to postexercise in Low and Med GCS relative to Con, and this may have implications for sprint performance at the end of a race. Well-trained runners rated Low and Con garments as most comfortable; therefore, athletes considering wearing GCS for training and racing should select low-grade compression stockings.
Acknowledgments
The funding source for this research was Invista International S.à.r.l. Geneva, Switzerland, and compression garments were provided by Julius Zorn GmbH, Aichach, Germany. The authors maintained intellectual property of the research outcomes to ensure that commercial bias had no effect on published material. There was no conflict of interest between Invista International, Julius Zorn, and the researchers. The authors and the National Strength and Conditioning Association wish to indicate that the results from this study do not endorse Invista International or Julius Zorn products. We would like to sincerely thank all the participants involved in this study and the research assistants who assisted with data collection; without their efforts this research would not be possible.
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