Positive Effect of Lower Body Compression Garments on Subsequent 40-kM Cycling Time Trial Performance

Abstract

de Glanville, KM and Hamlin, MJ. Positive effect of lower body compression garments on subsequent 40-km cycling time trial performance. J Strength Cond Res 26(2): 480–486, 2012—This study aimed to investigate the effect of wearing graduated compression garments during recovery on subsequent 40-km time trial performance. In a randomized single-blind crossover experiment, 14 trained multisport male athletes (mean ± SD: age 33.8 ± 6.8 years, 40-km time 66:11 ± 2:10 minutes:seconds) were given a graduated full-leg-length compressive garment (76% Meryl Elastane, 24% Lycra) or a similar-looking noncompressive placebo garment (92% Polyester, 8% Spandex) to wear continuously for 24 hours after performing an initial 40-km time trial in their normal cycling attire. After the 24-hour recovery period, the compression (or placebo) garments were removed, and a second 40-km time trial was then completed to gauge the effect of each garment on subsequent performance. One week later, the groups were reversed and testing procedures repeated. The participant's hydration status, nutritional intake, and training were similar before each set of trials. Performance time in the second time trial was substantially improved with compression compared with placebo garments (1.2 ± 0.4%, mean ± 90% confidence interval). This improvement resulted in a substantially higher average power output after wearing the compression garment compared with that after wearing the placebo garment (3.3 ± 1.1%). Differences in oxygen cost and rating of perceived exertion between groups were trivial or unclear. The wearing of graduated compressive garments during recovery is likely to be worthwhile and unlikely to be harmful for well-trained endurance athletes.

Introduction

Multisport athletes (individuals competing in events that contain the disciplines of run, cycle, swim or kayak) often compete over several days, in a number of disciplines, over long distances, sometimes with compromised sleeping and rest periods (³), which can result in performance problems. The most effective recovery strategy for such athletes is unclear, but many athletes are turning to compression garments typically worn during rest and sleep breaks, as a means of enhancing recovery for subsequent exercise bouts.

Ergogenic effects of wearing compression garments during training or competition are unclear. Research suggests that wearing compression garments may reduce muscle oscillation (⁷), improve peripheral circulation and venous return (¹), enhance blood flow velocity (³⁵), increase arterial perfusion (⁵), decrease postexercise muscle soreness (^2,27), and enhance the clearance of blood lactate (⁹) and creatine kinase (¹⁷). However, any clear beneficial performance effects while wearing compression garments are mainly limited to anaerobic or explosive forms of exercise (^14,25), which are not always witnessed (^15,26).

Similarly, research into the effects of compression garments on recovery of performance shows equivocal findings. The wearing of compression garments during recovery significantly improved force production (^23,27-29), countermovement and squat jump performance (²³), while decreasing indices of muscle soreness (^23,27-29). However, in a recent study, little difference in the recovery of the 5-m sprint, countermovement jump, or agility-505 performance was found between subjects who wore compression garments for 48 hours compared with that of controls (passive recovery group) (¹³). Moreover, 10- and 20-m sprint performance recovery may have actually been hindered by compression garments in this study (¹³), a result reported previously for 30-m sprint performance after 48 hours of wearing compression garments (¹⁶). Others have also found no beneficial effect of compression garments on strength, speed, and explosive performance during recovery (^8,16,29). These contradictory results on the performance effects of compression garments worn during recovery are highlighted by Montgomery et al. (³³) who found that wearing compression garments (compared with control) for up to 18 hours postexercise during a 3-day basketball tournament situation not only improved the recovery of a number of measures (line drill ability, vertical jump, subjective fatigue, muscle soreness) but also decreased the recovery of others (20-m speed, sit-and-reach) (³³).

To date, the majority of research conducted has been on the effects of compression garments on anaerobic or explosive-type performance recovery, whereas relatively little is known about the effects of such garments on aerobic performance recovery. The only study in this area known to the authors showed a 2.1 ± 1.4% (mean ± SD) improvement in 5-minute maximal power output in well-trained elderly men after wearing compression garments compared with that after wearing control garments during an 80-minute recovery period (⁹). Given the lack of information on the effect of wearing compression garments during recovery on subsequent longer-duration endurance performance, the aim of this study was to determine the effects of wearing commercially available graduated compression garments (garments that apply the highest pressure distally and the lowest pressure proximally) during prolonged recovery (24 hours) on subsequent 40-km cycling time trial performance in trained multisport athletes.

Methods

Experimental Approach to the Problem

This study used a single-blind crossover experiment to determine the effect of wearing full-leg-length graduated compressive garments vs. noncompressive garments during 24 hours of recovery, on 40-km cycling performance in trained multisport athletes. This within-group design allowed subjects to serve as their own control. Each participant performed two 40-km time trials 24 hours apart (set 1), which was repeated after a 1-week washout period (set 2). In a randomized counterbalanced design, the participants were asked to wear commercially available full-leg-length (from ankle to hip) graduated compression garments (Skins compression garments, Sydney, Australia—76% Meryl Elastane, 24% Lycra) or a noncompressive control garment (Nike noncompressive 92% Polyester, 8% Spandex) during the 24-hour recovery period between the 2 time trials of each set. The garments were only put on after the initial time trial of each set was completed in normal cycle training attire (top and shorts); therefore, we feel confident that the experimental effect evaluated in this study is the ability of the garments to cause change during the recovery period. Additionally, in an attempt to blind the participants as to the type of garment being worn, the participants were informed that the study was to compare 2 types of compression garment. A familiarization trial was completed 1 week before testing. The familiarization consisted of a complete run-through of the experimental procedures including a 40-km time trial, how to record and replicate dietary and training information, and familiarization with all the physiological testing equipment and processes. The participants were also advised on ideal hydration techniques to ensure euhydration for all testing sessions. To simulate heavy aerobic exercise sessions typical of multisport events, a 40-km cycling time trial was used because it gives reliable performance results (³⁶) and cycling is usually compulsory in most multisport races.

Subjects

Participants' characteristics are presented in Table 1. All the participants completed a health questionnaire, and no adverse medical conditions were reported. All the study participants gave written informed consent, and the study was approved by the university human ethics committee.

Table 1: Characteristics and baseline performance measures.*†‡

The participants were asked to refrain from intense exercise and alcohol for 24 hours before, and caffeine from 4 hours before each main trial. The participants also recorded their dietary intake 24 hours before each trial to allow replication of diet before subsequent trials. Dietary information was analyzed for total caloric intake and macronutrient composition using FoodWorks 2009 (Xyris Software, Queensland, Australia).

Procedures

Training

The participants were asked to maintain a steady level of training for the length of the study and record the type, duration, and intensity of all activity for 1 week before each set of 2 time trials. To compare the total training load between sets of time trials and among the 2 groups, training impulse (⁴), which has been shown to be a reliable measure of workload (²²), was calculated which was expressed as a product of stress (duration of activity) and strain (subjective rating of training intensity). The participants reported their subjective feelings with the use of the following 5-point Likert-type scale; excellent = 1, good = 2, average = 3, poor = 4, very poor = 5.

Compression Garments

Immediately after the first time trial of each set, full-leg garments were donned and worn continuously until the participants returned to the laboratory 24 hours later. If the participants had to remove the garments (i.e., to shower), they were asked to put them back on as soon as possible. The full lower body garments were fitted to the athlete according to manufacturer's guidelines and covered from the ankle to the waist of the athletes. The absolute pressure exerted by the garments on the participant's lower limbs (mean of 3 values) was measured with a bandage pressure monitor (Kikuhime, Soro, Germany) at 3 standard anthropometric sites of midtrochanterion–tibiale laterale, midcalf, and 10 cm above the sphyrion on the right limb while the athlete was in the prone position (Figure 1).

Figure 1: Mean ± SD compression in millimeters of mercury of the lower body compression garments used in this study.

Performance Tests

Performance was evaluated by a series of 40-km time trials conducted on an electromagnetically braked cycle ergometer (Velotron Pro ergometer Racermate Inc., Seattle, WA, USA). Before each test, the factory calibration was verified, using the Accuwatt ‘run down’ verification program (Racermate Inc.). During the performance tests, the participants consumed no food but were able to drink water ad libitum. The participants used their own pedals and cleated shoes during all testing. The cycle ergometer was adjusted to the athlete's preferred position, which was then replicated in the subsequent trials. The gear ratios of the athlete's personal road bike were entered into the Velotron software (Velotron, RacerMate Inc.), allowing them to change gear as they wished throughout the test. After 4 minutes of resting data collection while supine and 2-minute resting data while seated stationary on the bike, the participants completed a 15-minute self-selected warm-up during which a start gear was selected for the time trial. The participants then completed a simulated 40-km race. The participants were informed of distance covered at 10-, 20-, 30-, 35-km time points and then every 1 km through to 40 km but received no feedback on power output, heart rate, pedal cadence, or performance time.

Physiological Measurements

Ventilation and expired gases were measured breath by breath, and averaged every 5 seconds, for a period of approximately 2 minutes leading up to each measurement point at 10, 20, 30, and 40 km using a portable gas exchange system (MetaMax® 3B; Cortex Biophysik, Leipzig, Germany). The reported gas variables are the average of the final minute of this gas collection. Because the time trial is similar to a steady-state test in that the participants show an initial increase in speed and power over the first minute or so and then tend to maintain a relatively stable power output until the final ‘sprint’ in the last 1–2 minutes of the test, we have been able to calculate oxygen cost. For each participant, the oxygen cost of exercise, expressed as milliliters of oxygen per watt, was calculated for the last minute of each of the first 3 stages (10, 20, and 30 km) and then averaged. Before testing, the gas analyzer was calibrated for volume (Hans Rudolph 5530 3-L syringe; Kansas City, MO, USA) and gas composition (15% O₂ and 5% CO₂). The heart rate was measured at baseline and then recorded continuously throughout the time trial and 30-minute recovery period (S725X; Polar, Kempele, Finland). Blood lactate concentration was determined from a finger-prick sample and analyzed using a portable lactate analyzer (Lactate Pro, Arkray Inc., Kyoto, Japan). Blood pressure of the right arm was measured when supine using an automatic blood pressure monitor (Welch Allyn OSZ-5, New York, NY, USA) at rest, and at the end of the 40 km. The participant rating of perceived exertion was recorded by using a Borg scale at 10, 20, 30, and 40 km. The subjects were asked to drink 500 ml of water approximately 2 hours before testing in an attempt to standardize bodily fluid concentrations. Hydration status (urine specific gravity; Bayer Diagnostics Multistix®, Leverkusen, Germany) and nude body mass were determined on arrival at the laboratory.

Thirty-minute Recovery Testing

Immediately after the first time trial of each set, the garments (compression or placebo) were put on, and the participants lay in the supine position for a 30-minute monitored passive recovery period. The effect of the garment on blood lactate concentration, supine blood pressure, and heart rate was measured at 10-minute intervals during the 30-minute recovery.

Statistical Analyses

To investigate the effects of wearing a compression garment for 24 hours on subsequent 40-km cycling time trial performance, a statistical analysis was performed using a specifically designed spreadsheet available for crossover studies (¹⁸). We used a contemporary statistical approach (²⁰) because small performance changes can be beneficial for elite athletes, whereas conventional statistics can be less sensitive to such small but worthwhile changes. From the spreadsheet, we used magnitude-based inferences about effect sizes, then to make inferences about true (population) values of the effect, the uncertainty in the effect was expressed as 90% confidence limits. Changes and errors were expressed as percents via analysis of log-transformed values, to reduce bias arising from nonuniformity of error and back transformed to obtain changes in means in raw values (²⁰). The probability that the true value of the effect was practically negative, trivial, or positive accounted for the observed difference, and typical error of measurement. The smallest worthwhile change in performance was assumed to be a reduction or increase of 1% because this has been shown to represent the smallest worthwhile enhancement for cyclists competing in track or time trial events (³⁴). To adjust for any confounding effects of fitness level, we adjusted the mean difference between the 2 posttests in each group (compression and placebo) by including the average difference in the pretests between each group as a covariate. We also adjusted the performance changes for the order of testing and amount of training by including these variables as covariates and combined the outcomes using a specialized spreadsheet (¹⁹). For the other physiological measures, the smallest worthwhile value was determined by multiplying the baseline between-subject SD by Cohen's value of the smallest worthwhile effect of 0.2 (¹¹). Effects that were simultaneously both >75% likely positive and <5% negative were considered substantial and beneficial. An effect was deemed unclear if its confidence interval (CI) overlapped the thresholds for substantiveness, that is, if the effect could be substantially positive and negative or beneficial and harmful.

Results

Compared with the placebo garment, wearing the compressive garment produced substantially higher tissue pressures (compression, 6.0 ± 2.4, 14.7 ± 2.5, 11.8 ± 2.5; placebo, 1.5 ± 0.9, 5.7 ± 0.9, 5.9 ± 1.3 mm Hg [raw mean ± SD] for the sphyrion, midcalf, and mid trochanterion sites, respectively).

After adjusting for initial fitness levels and any order or training effects, the mean power output and performance time were clearly improved after wearing the compression garment compared with that obtained after wearing the placebo garment (Table 2). When the time trial was divided into quarters, power output was substantially higher in all quarters in the compression compared with placebo garments (Figure 2). There was no substantial change in the rate of perceived exertion between groups during the 40-km time trial at any of the quarters.

Table 2: Effect size (difference in the performance change of compression-placebo groups) and chances that the true effect represents a substantial improvement or impairment in performance.*

Figure 2: Mean power output during the four quarters of the 40-km time trial between groups (compression-placebo) after 24 hours of wearing garments and adjusting for baseline values. Data are raw mean ± SD. *Substantially different between groups.

Differences in mean oxygen cost during the 40-km time trial (−1.4 ± 3.0%, Table 2) and blood lactate concentration immediately after the time trial were unclear (8.2 ± 2.6, 7.4 ± 2.9 and 8.4 ± 2.9, 6.8 ± 2.9 mmol·L⁻¹ for trials 1 and 2 in the compression and placebo groups, respectively). Wearing placebo garments during recovery resulted in lower heart rates at the 10-km time point compared with compression garments (−3.1 ± 3.5%, mean ± 90% CL); however, all other changes in heart rates during the time trial were unclear.

Observed standard error (typical or within-subject error) of measurement for the experimental measures were 40-km mean power 3.3%, 40-km time 1.2%, and mean oxygen cost 2.9%. The 90% confidence limits for the true errors were approximately ×/÷1.4 for all measures. The SDs representing the observed individual responses in performance were 40-km mean power 3.3% (−1.3 to 4.8%) (mean and 90% confidence interval), 40-km time 1.2% (−0.5 to 1.8%), oxygen cost, −4.7% (−7.1 to 2.8%). However, the uncertainty in both the positive and negative SDs suggests modest individual responses for all measures, relative to the mean effects.

Changes in the physiological measures during the first 30-minute monitored recovery after the first time trial of each set when the participants initially donned the respective garments between groups were either trivial or unclear. However, substantial changes in blood pressure between groups were found immediately after removing the garments (24 hours after initially donning them). Relative to the placebo garment, removing the compressive garments after 24-hour wear resulted in a large drop in blood pressure (−4.3 ± 3.2, −4.6 ± 5.2, −4.4 ± 3.4 mm Hg, mean ± 90% CI for the systolic, diastolic, and mean blood pressures, respectively).

There was no substantial difference in hydration (compression 1.01 ± 0.01, 1.01 ± 0.01; placebo 1.01 ± 0.01, 1.02 ± 0.01, for pretest and 24-hour posttest, respectively; raw mean ± SD) and body mass (compression 74.8 ± 4.4 kg, 75.4 ± 5.4 kg; placebo 74.8 ± 4.4 kg, 74.6 ± 4.5 kg) before all performance exercise trials. The 24-hour dietary analysis revealed that the participant's total caloric intake and the proportion of carbohydrate in the diet were similar across all trials.

Discussion

Our findings have revealed that relative to a placebo garment, wearing a compression garment for a 24-hour recovery period between successive 40-km time trials substantially improved the performance in the second time trial. This study is unique in that we used changes in repetitive 40-km time trials as the performance indicator, we blinded the participants by using similar-looking compression and placebo garments, and finally, garments were used as recovery aids rather than as ergogenic tools to be worn during the activity.

Although compression garments are becoming increasingly popular with many athletes, there remains little evidence-based research on the effects of such garments on longer-duration aerobic performance, particularly when worn as a recovery aid. Previously, 5-minute maximal power output was shown to increase by 2.1% using compression garments compared with that of controls during an 80-minute recovery period (⁹), a magnitude of improvement similar to the performance change in this study. Effects on anaerobic performance after wearing compression garments during recovery remain equivocal (^{8,13,16,23,27-29}). A major problem with many of the previous studies is the failure to use appropriate placebo controls. Earlier researchers have instructed participants to wear either the compression garment or their normal exercise training attire (e.g., gym shorts). The influence of any subjective perceived benefit from the experimental intervention (compression) is therefore not accounted for in the research design and may have influenced the results (¹⁰). Findings from this study (using compression and placebo garments that were similar in looks and feel) indicate that compression garments may enhance 40-km finish times by approximately 1.2%, which represents a small but worthwhile improvement.

Mechanisms behind the improved performance after wearing the compression garments remain unclear. It has been suggested that wearing graduated compression garments postexercise acts to increase venous blood flow thereby enhancing stroke volume and cardiac output (⁹), which may enhance muscle blood flow and subsequent recovery. Liu (³¹) provided some evidence for such a mechanism when he reported that compression garments with 10–14 mm Hg pressure at the ankle increased mean flow velocities in the popliteal veins by 9.6% (³¹). Moreover, in an earlier study, clear and significant increases in stroke volume and cardiac output with subsequent decreases in the heart rate were observed in the standing position in 6 young women 40 minutes after donning compression garments at rest (³⁷). Although the pressures exerted by the compression garments reported in this study are similar to pressures reported to have beneficial effects on venous flow (³¹), many studies have failed to measure such pressures. It is suggested that a pressure range may exist for blood flow changes, such that very little change to blood flow will occur at lower pressures (³²). This pressure-venous flow relationship may explain some of the inconsistencies in performance results in the literature, because in many studies pressure values were either not measured or were too low.

It has also been suggested that the increase in muscle blood flow may be attributed to arterial rather than to venous changes with compression. The pressure externally applied to the muscle may cause compression of the underlying tissues which acts to reduce transmural pressure in local arterioles, causing reflex vasodilation and increased blood flow to the area (⁵). Indeed increased muscle oxygenation (measured using near infrared spectroscopy) has been observed in subjects wearing compression garments compared with that in controls (⁶). Clearly, the effects of compression garments on changes in venous or arterial flow (or some combination of both) require further research.

It is likely that the first 40-km time trial of each set in this study led to significant glycogen depletion, similar to that observed by Costill et al. (¹²) in their classical study on runners after successive daily bouts of heavy exercise (¹²). Such glycogen depletion potentially limits subsequent performance via inadequate muscle glycogen synthesis. Because glucose delivery via the blood stream is an important limiting factor in muscle glycogen synthesis (²⁴), any improvement in blood flow can hypothetically alter glucose availability to the muscle and ultimately glycogen synthesis. We speculate that enhanced muscle blood flow during recovery in participants wearing compression garments (either by increased venous return or reflex arterial vasodilatation) may have assisted in the recovery of the working muscles via a number of processes including but not limited to increased glucose drop-off at the muscle, aerobic resynthesis of ATP, enhanced repair of damaged tissue or removal of waste and cellular breakdown products. Although speculative, a number of indicators found in this study would suggest that enhanced glucose metabolism may play a part in the performance change including a moderately higher (9.3%) but unclear 40-km blood lactate concentration in the compression relative to the placebo group after the second time trial. In addition, although not conclusive, but similar to previous research (⁷), we showed a downward trend in oxygen cost (i.e., improved cycling economy) in the compression compared with that in the placebo group. Lower oxygen consumption may be because of a move toward greater carbohydrate and less fat use in oxidative phosphorylation. An increase in carbohydrate metabolism in the compression group was not because of any change in diet but may have resulted from increased muscle glycogen storage secondary to enhanced glucose availability via the blood; however, more research taking serial blood flow and muscle glycogen measures during exercise and recovery is required to confirm this hypothesis.

The unusual findings of a decrease in blood pressure after the removal of compression but not placebo garments also suggest pressure-related changes with such garments. We speculate that once the compression garments were removed, the elevated pressure applied to the limbs was immediately reduced resulting in a relative decrease in venous return and total peripheral resistance leading to a decreased stroke volume and cardiac output resulting in a drop in blood pressure. However, further research using measures of heart rate, stroke volume, cardiac output, and blood pressure are required to confirm these findings.

We suspect that dehydration was not involved in the change in performance because athletes were at similar levels of hydration during each exercise test; however, it is possible that other mechanisms are responsible for the improved performance in the compression group. We cannot rule out the influence of a placebo effect when wearing the compression garments and mechanical stimulation of muscle afferents is also a possibility. For example, researchers have found indicators of altered autonomic nervous system function (³⁰), or enhanced motor control while wearing compression garments (²¹), but such measures were beyond the scope of this study.

Practical Applications

The practical application of this study is that when worn for a 24-hour period, graduated compression garments, are very likely to improve subsequent 40-km cycling performance. We therefore suggest that compression garments should be considered along with other well-established postperformance regimes for adequate recovery.

Acknowledgments

The authors thank the volunteers involved in this study and acknowledge the New Zealand Science, Mathematics and Technology Teacher Fellowship Scheme and Lincoln University Research Fund for funding the research.