The Effects of Compression Pants on Oxygen Consumption and Heart Rate during Long-Distance Running

Abstract

The purpose of this study was to compare average rate of oxygen consumption (VO₂), slow component of oxygen consumption (VO₂ drift), heart rate (HR) and rating of perceived exertion (RPE) while wearing compression pants vs. a control garment during long-distance running. Methods: Nine injury-free and recreationally active participants (32 ± 11 years) were recruited for this study. Participants ran in full-leg compression pants (COMP) and a loose-fitting control garment (CON). Participants ran in each condition for 40 min at a preferred submaximal speed. The rate of oxygen consumption (VO₂) was measured continuously via a metabolic cart throughout each condition. Both HR and RPE were recorded every 5 min during each condition. Oxygen consumption was averaged across the entirety of the steady state during the 40 min conditions for analysis. Additionally, the average from the first five minutes of the steady state was subtracted from the average of the last five minutes to assess VO₂. A paired t-test was used to assess for differences for both variables. Both HR and RPE were each compared between conditions using 2 (garment) × 8 (time) repeated measure ANOVAs (α = 0.05). Results: There were no differences between VO₂ or VO₂ drift while running with full-leg compression pants vs. the control garment (p > 0.05). Neither RPE nor HR were influenced by the garments (p > 0.05) or time (p > 0.05) during each condition. Conclusion: Wearing compression pants did not result in reduced VO₂, VO₂ drift, HR or RPE during a long-distance run. Although measured performance variables were not aided using compression pants, there were no negative effects to the use of compression pants.

1. Introduction

Traditionally, running is one of the most common modalities of exercise. It requires little to no equipment and can be used as sport if runners competitively race one another. In recent years, participation in running events has grown to one of the most popular activities for adults [1]. Therefore, recent literature has explored ways to increase athletic performance and decrease injury through different techniques and equipment. Currently, one of the largest industries in running equipment is compression garments. In a recently published market research report, the compression and shapewear industries were reported to be valued at $5.63 billion with an expected 6.2% growth in the next decade [2]. Despite the clothing’s massive popularity, there is limited research into the effect it may have on running performance. A recent meta-analysis investigating the effects of lower leg compression garments on fatigue found conflicting results from the current literature [3]. These results are common among reviews of this topic which highlights the need for more research to establish real trends in a variety of variables.

A runner’s performance is a combination of many different variables. For instance, blood lactate levels may be informative of an athlete’s level of fatigue as well as recovery, as lactate is a byproduct of anaerobic metabolism and glycogen utilization. With depleted muscle glycogen stores being widely associated with fatigue, elevated blood lactate levels may further represent glycogen depletion and thus fatigue [4]. Compression garments have been shown to decrease these variables and increase force production [5,6]. Importantly, the potential benefit of lowered lactate is considered to be due more so to lactate clearance/removal as opposed to decreased overall production [7]. Compression garments may also aid cycling performance by enhancing blood flow and decreasing muscle soreness [8]. Additionally, it has been reported that compression garments improved lactic acid release and reduce muscle soreness during a high intensity workout and received small effects in post exercise blood lactate levels following a sprint, a 40 min run and an endurance run [9,10]. Thus, it is important to examine many variables that could contribute to performance enhancement while wearing compression garments during an aerobic run.

One major link between compression garments and running performance comes down to the mechanical effect of applying pressure to soft tissue. The pressure added with compression garments may reduce muscle vibration as well as soft tissue oscillation. This would help reduce muscle tissue damage and it could provide insight into their role in injury prevention [11,12]. During running events, repeated and forceful muscle oscillation of the leg tissues was attributed to an increased risk of lower extremity injuries [13]. In a vast study, 243 out of 512 athletes reported that their primary reason for wearing compression garments was to prevent secondary sporting injuries [14]. Compression garments are shown to reduce muscle oscillation during running, which can enhance peripheral blood circulation [15,16]. A similar study that tested oxygen consumption during a 40 min run wearing control garments or low- or high-grade compression garments reported that there was no difference between any of the trials. Additionally, heart rate increased during all trials and there was no difference between the trials [17]. Compression may also reduce the energy expenditure of lower extremity muscles through reducing the need for muscle tuning [18,19,20,21]. A recent study [18] evaluated runners using compression pants and measured muscle oscillation, muscle activation time and oxygen consumption. They concluded that compression reduced muscle oscillation and muscle activation time; however, oxygen consumption was unaffected. This study only observed six-minute steady state trials and was not indicative of a longer endurance run. It is possible that over a longer period of time, compression may reduce the oxygen demand of the runner and may slow down VO₂ drift at a steady workload.

Therefore, the purpose of our study was to evaluate three physiological variables while running with the use of compression pants (COMP) and without the use of compression garments (CON). First, the present study aimed to examine oxygen consumption and VO₂ drift during a 40 min run. Additionally, to assess changes in objective and subjective exercise intensity, heart rate and rating of perceived exertion (RPE) were monitored during exercise and compared between conditions. While previous studies are inconclusive with respect to oxygen consumption and compression use, there is clear evidence for a reduction in muscle oscillation with the use of compression pants. Therefore, under the premise that reduced muscle oscillation decreases muscle activity, and decreased muscle activity requires less oxygen, we hypothesize that average oxygen consumption would be reduced and VO₂ drift would be lessened with the use of compression. Also, we hypothesize that heart rate and RPE would be significantly reduced, over the course of the 40 min run, in the compression condition relative to the control. This would coincide with a lower demand of oxygen.

2. Materials and Methods

2.1. Participants

All participants (n = 9; 1.71 ± 0.05 m; 67.35 ± 10.11 kg; 32 ± 11 years.; 3M6F) were over the age of 18, were at least one year free of lower extremity injury and were self-described recreational runners. The participants confirmed they ran at least 5 miles per week for at least the six previous weeks, with a range from 8.7 to 87.5 miles/week with an average of 37.8 miles/week. Average preferred speed of the participants was 6.1 ± 1.2 mph. Participants completed and signed an informed consent form that was approved by the University Biomedical Institutional Review Board.

2.2. Measures

2.2.1. Compression Pants

The compression pants used for this study were from the brand ‘Compression Z’ and were reported to be made of 82% nylon and 18% spandex. The exact pressure imposed by the garment was not reported by the manufacturer; however, compression claims made in advertisements and similar pants by the company were given a pressure range of 30–40 mmHg.

2.2.2. Oxygen Consumption and VO₂ Drift

Oxygen Consumption (VO₂) was measured using the TrueOne metabolic system (Parvo Medics, Salt Lake City, UT, USA). The metabolic cart was calibrated in accordance with the manufacturer’s instructions prior to every use.

2.2.3. Heart Rate (HR)

Heart rate was measured using a Polar RS800CX telemetry system (Polar Electro Inc., Bethpage, NY, USA) and integrated into the TrueOne metabolic software (version 4.3.4).

2.2.4. Rating of Perceived Exertion (RPE)

Perceived exertion was measured using Borg’s 6–20 point RPE scale [22]. This self-report measure of exercise intensity uses a 15-point scale in which participants are asked to indicate how hard they are working right now. The scale ranges from 6 (i.e., “No exertion at all”) to 20 (i.e., “Maximal exertion”), and includes the phrases “Extremely light”, “Very Light”, “Somewhat hard”, “Hard (heavy)”, “Very hard” and “Extremely hard” to help participants indicate the correct number. The RPE is a common tool to assess subjective exercise intensity and has been validated within the exercise literature [23].

2.3. Procedures

All participants attended two visits to complete the trials under the two different conditions, once for the compression pants (COMP) condition and once for the control (CON) condition with no compression garments. Both testing sessions took place at the same time of day in the same research laboratory. This lab is climate controlled to ensure similar conditions across multiple testing sessions. Participants were instructed to keep similar routines on testing days. They were scheduled to test at the same time of day for both visits and were instructed to keep dietary intake the same on both sessions. They were also instructed to alert research staff if anything notably different occurred on the second day of testing compared to the first. Participants were instructed to wear loose-fitting shorts and non-compressive undergarments to testing sessions to serve as the control garments. These shorts were assessed prior to the control condition to ensure no compressive force was applied to the covered area. During COMP, participants wore the compression pants given to them by the research staff and they were fitted for the size of the pants according to manufacturer’s guidelines. Participants had to wait at least 24 h after the first visit but no longer than one week before returning for the second visit.

Upon arrival during the first visit, participants completed a health history questionnaire to clear them for exercise and their anthropometrics were recorded. Participants were given an opportunity to warm up as they saw fit but were limited to no longer than 5 min. Following warm up, each participant’s preferred speed (PS) was collected to determine the running speed to be set for each condition. For this study, PS was described to the participants as the speed at which they would be comfortable to run continuously for at least one hour. To determine this, the investigator set the treadmill speed to just below 1.3 m/s and blocked all speed readings. Participants were then instructed to increase the treadmill speed (i.e., blinded) until they reached their PS. This was performed three times consecutively, and the final PS was calculated as the average of these speeds. Measurement procedures for PS were only taken at the beginning of the first visit regardless of condition being performed. Therefore, both conditions used the same individual PS for the entirety of the running trial. Participants were then equipped with a polar heart rate monitor to record their heart rate during running. Each participant was also equipped with an oxygen mask connected to a metabolic testing cart to record their oxygen consumption (VO₂). Each participant was given time to adjust to wearing the mask and attached tube to ensure comfort throughout the extended running trials. After a five min period of quiet sitting, resting HR was recorded for 30 s and then averaged. This measurement was used to monitor starting excitation between visits.

Participants then ran for 40 min on a treadmill at their PS in either CON or COMP. Conditions were counterbalanced between visit 1 and visit 2. Both VO₂ and HR were collected continuously throughout the entirety of the trial. During the trial, RPE was measured and recorded every 5 min. This measurement was taken to ensure the participants were running at an appropriate pace and that the intensity remained sub-maximal. All participants completed both visits and adhered to all requested instructions.

2.4. Analysis

The variable concerning the rate of oxygen consumption was calculated from the onset of the steady state until the end of the trial. The onset of the steady state was determined visually by the analyst and then verified by comparing the VO₂ level against an average of a 10 min window from minute 20 to 30 during the trial. During steady state identification, data were smoothed using a fourth-order five-point moving window average to ensure accuracy of visual determination. After the onset of the steady state was determined, all variables were calculated using raw breath by breath data for analysis. The first variable assessed was an average VO₂ of the entirety of the steady state running. A second rate of oxygen consumption variable was assessed to evaluate the slow component of oxygen consumption (VO₂ drift). Individual VO₂ drift was calculated by subtracting the average VO₂ from the first 5 min of the steady state from the average VO₂ of the last 5 min of the trial.

To assess changes in both subjective (RPE) and objective (HR) measures of exercise intensity, analyses of differences were conducted using a Condition (2: CON, COMP) by Time (8: 1, 2, 3, 4, 5, 6, 7, 8) repeated measure analysis of variance with a Bonferroni correction to protect against multiple comparisons. A paired-sample t-test was used to assess changes in VO₂ and VO₂ drift. Effect sizes were calculated using Cohen’s d [24]. Significance was set to 0.05.

3. Results

The results from comparing average VO₂ (Figure 1) during CON (31.96 ± 8.2 mL/kg/min) to during COMP (32.68 ± 6.9 mL/kg/min) showed there were no significant differences in oxygen consumption (t (8) = 2.30, p = 0.241; Cohen’s d = 0.10) between conditions. Across all trials, participants took 139.2 ± 46.4 s on average to reach steady state VO₂. When viewing the individual responses to wearing compression pants, only 4 participants had more than a 1% change in average VO₂. Within these 4 individuals, two increased oxygen consumption and two decreased oxygen consumption during the run. When analyzing the data regarding the drift in VO₂, it was revealed that there were no significant differences between CON (2.05 ± 3.69 mL/kg/min) and COMP (1.52 ± 2.74 mL/kg/min) in change in VO₂ (Figure 2) over the 40 min run (t (8) = 2.31, p = 0.30; Cohen’s d = 0.16).

To assess exercise intensity, both a subjective (i.e., RPE) and objective (i.e., HR) measure was used. Using a Condition (2: CON, COMP) by Time (8: 1, 2, 3, 4, 5, 6, 7, 8) repeated measure analysis of variance (ANOVA), both RPE (Figure 3) and HR (Figure 4) were examined. For RPE, neither the Condition (p = 0.22) or Time (p = 0.07) main effects were significant. Additionally, the Condition × Time interaction was non-significant (p = 0.06). The Condition main effect (p = 0.75) for HR was not significant, but there was a significant Time main effect (p < 0.001). Specifically, HR increased throughout both conditions. The Condition × Time interaction was non-significant (p = 0.72).

4. Discussion

The present study utilized a randomized, within-subjects design to examine the effects of wearing compression pants relative to a control condition on oxygen consumption, VO₂ drift, RPE and heart rate throughout a 40 min run at the participant’s preferred speed. The main findings of this study were that oxygen consumption, VO₂ drift, heart rate, and RPE were unaffected by the use of compression pants during running. These results indicate that although there were no negative effects, wearing compression pants offers no physiological advantage during a 40 min run. The implications of the study suggest compression pants can be worn at the discretion of athletes/coaches with no adverse effects on oxygen consumption, VO₂ drift, RPE or heart rate.

First, it was hypothesized that oxygen consumption would be significantly reduced during the compression garment condition relative to the control condition. The results of the present study do not support this hypothesis as there was no difference in oxygen consumption between conditions. This is somewhat surprising as numerous studies have shown that the use of compression can decrease energy expenditure [16,17,18,19]. It follows that a decrease in energy expenditure would be accompanied by a reduction in oxygen consumption. This was not observed in the present study. Further, Scanlan et al. found near-significant improvements in muscle oxygenation economy while using lower-body compression garments during endurance cycling. Participants completed two 60 min cycling sessions at a cadence between 90 and 100 RPM. Participants were able to self-select their power output but were encouraged to select the highest power output they could maintain for the 60 min exercise session [25]. However, other studies have shown no changes in oxygen consumption with respect to compression. Creasy and Edge had participants complete three 40 min exercise sessions at a one percent incline at 90 percent of each participant’s best 10 km speed while wearing control, low grade and high grade graduated compression stockings. Their results suggest no differences in oxygen uptake, heart rate or blood lactate between conditions [15]. Overall, the results from various studies assessing changes in oxygen consumption due to compression garment use appear mixed. To the best of our knowledge, no studies have reported a negative effect of compression garments on oxygen consumption, but further randomized controlled trials with larger samples are needed.

Next, it was hypothesized that VO₂ drift would be significantly reduced with the use of compression pants. The results of the present study do not support the hypothesis. While participants did not report a significant difference in VO₂ drift with the use of compression, individual participants responded favorably to the use of compression. Specifically, five of the nine participants reported a favorable (i.e., lower) VO₂ drift during the compression condition relative to the control. Further, these five participants reported a VO₂ drift almost half that experienced during their control condition (i.e., 49.18%). The overall difference in VO₂ drift between conditions of these five participants was on average 0.5 mL/kg/min and the significance of this difference may be situational. Again, the results of the present study do not support the hypothesis, but bring into light the possibility of individual responders vs. non-responders in that some may experience more consistent oxygen utilization over longer periods of time when utilizing compression pants (relative to increased oxygen consumption over time). It would be of value to explore psychological variables to determine if perceived benefits may be a driving force behind these five participants.

Finally, it was hypothesized that heart rate and rating of perceived exertion would be reduced during the compression condition relative to the control. The results of the present study do not support this hypothesis as there was no difference in heart rate or RPE between conditions. This is somewhat surprising as compression pants have been shown to significantly reduce muscle oscillation [13,14]. Reduced muscle oscillation equates to reduced muscle activity, and reduced muscle activity leads to a decrease in oxygen need. Theoretically, a decrease in the need for oxygen should be accompanied by a decrease in heart rate and subjective exertion. However, this was not observed in the present study. The present results are, in part, supported by previous research on performance and recovery variables associated with the use of compression garments. A systematic review and meta-analysis on performance variables associated with compression garment use concluded no significant improvements [26]. Duffield et al. examined numerous performance variables following an 80 min high-intensity circuit exercise in male rugby players with and without the use of compression garments. Their results conclude no significant differences in heart rate, peak power, or 20 m sprint times. However, male rugby players did report a lower subjective rating of perceived muscle soreness with the use of compression [27]. While the use of compression may not directly impact heart rate during exercise, there still may be some perceived benefits associated with wearing compression pants.

There are several limitations to the present study. First, the sample size is relatively small. While it is possible there would be a significant difference in performance variables if examined in a larger sample, this is unlikely. This particular sample size was based on previous research that had enough power to find differences in conditions with similar sizes [15,18,28,29,30,31]. We feel that with a repeated measures design there is enough power to assess differences between conditions. Additionally, a statistical power analysis was not able to be performed as previous effect sizes on similar variables and sample size were not reported. Given the average VO₂ during the compression and control conditions, there is not even a trend for improved VO₂ during the compression condition. Therefore, it is unlikely the inclusion of a larger sample would yield any significant results. This study is further limited by the type of compression garment used. We studied the effects of compression pants and not any other type of compression clothing. It is possible that with additional compression, sleeves, vest, socks, etc., oxygen consumption outcomes may have been different than what we observed. Another limitation associated with the sample was their previous running experience. All participants self-identified as recreational runners who ran at least 5 miles per week over the previous six weeks. While this was necessary for participants to complete each of the 40 min self-paced exercise conditions, it may have hindered any physical benefits of compression pants. Given all participants were at least recreationally active, with the average participant running 37.8 miles per week, it follows that their overall fitness is greater than a sedentary individual. Thus, the potential benefits from compression might be overridden by a trained cardiorespiratory system. It would be of value to explore the same physiological variables in a sample of untrained/sedentary individuals.

5. Conclusions

Overall, there do not appear to be any physiological benefits associated with the use of compression pants during exercise. The results of the present study support this by finding no difference in oxygen consumption, VO₂ drift, or heart rate during a 40 min run while wearing compression relative to a control condition. However, it is important to note that even without an improvement in measured variables, there was no detriment to wearing compression pants. This is a major finding for runners and coaches who may prefer these pants for alternative reasons. Future studies need to explore alternative benefits associated with the use of compression pants. Specifically, it would be of value to examine psychological variables, individual preferences and perceived benefits accompanying the use of compression pants during exercise.