Field-based team sports incorporate a unique activity profile of prolonged high-intensity intermittent exercise (PHIIE) that imposes specific physiological demands on athletes (4,8,12,14,18). Team sport-specific PHIIE consists of repetitive bouts of high-intensity activities (HIAs) (e.g., fast running, sprinting) interspersed with periods of low-intensity activity (LIA) (e.g., walking, jogging) (4,18,28,31), which places high metabolic demands on both the aerobic and anaerobic energy systems (12,14,18,27). For example, soccer players have been observed to complete an HIA every 30 seconds during a match, whereas the LIA:HIA time ratio of their match play is approximately 12:1 (4,28). Similarly, hockey players carry out an HIA every 27 seconds, with an LIA:HIA ratio of approximately 10:1 (31). Further, team-sport athletes are typically reported to maintain average heart rates (HRs) between 155 and 170 b·min−1, (12,14,27) and blood-lactate concentrations ([BLa−]) of between 4 and 8 mmol·L−1 (12,14,27). These high physiological intensities, in combination with tactical and nutritional considerations, may help to explain the reported decline in physical performance and sprinting ability across a match (4,12,27,28).
Team-sport physical performance (i.e., distance covered) has previously been related to several physiological capacities, quality of play, maintenance of HIA, and repeat sprint ability (4,20,27,28). Investigators have suggested that either reducing the physiological demands or increasing the distance covered during PHIIE may improve factors related to field-based team-sport performance (18,20,27,28). Team-sport athletes may benefit from improving the total distance covered and the frequency of HIA across a match that may allow superior tactical positioning. In turn, this is hypothesized to enable more advantageous personal performance and team scoring opportunities (4,8).
Previously, wearing compression garments (CGs) has been reported to ergogenically aid performance and recovery across athletic populations (6,7,15,25,26). Past studies have suggested that wearing CGs reduces muscle oscillation (15,25) and venous blood pooling (26). In addition, investigators have identified that wearing CGs accelerates metabolic recovery after anaerobic exercise (6,10) and improves exercise efficiency (7,29), anaerobic threshold (29), and muscle oxygenation responses (2,29). Such benefits are primarily attributed to the circulatory benefits associated with wearing CGs, including improvements in venous return and subsequent increases in stroke volume and cardiac output (3).
To date, limited data exist on the effects of wearing CGs on the physical performance and physiological responses during intermittent exercise (16,21,23). Original data from Duffield and Portus (16) compared 3 brands of whole-body compression garments (WBCGs) on selected physiological and performance measures during a 30-minute exercise protocol comprised of repeated 20-m sprints interspersed with LIA. No significant improvement was observed in mean sprint time, fatigue decrement, and distance covered in any WBCG brand compared with the control condition. In addition, no effect was observed in the physiological intensities during the intermittent protocol in any WBCG condition. However, a significant increase was reported in skin temperature in all WBCG conditions, suggesting that the garments were responsible for some thermoregulatory effects during the intermittent exercise protocol. Similarly, Houghton et al. (23) completed an investigation detailing the thermoregulatory and performance effects of wearing short sleeve and leg WBCGs across the Loughborough Intermittent Shuttle Test. The investigators reported that although wearing the WBCGs did not benefit physical performance, nor significantly elevate core temperature, a significant increase in skin temperature was observed between the 2 conditions. Therefore, wearing CGs may have some thermoregulatory effects although this may be on peripheral musculature. A further study from Higgins and associates (21) identified no significant performance or physiological effects of lower-body CGs during a field-based netball simulation in comparison with placebo and control conditions. However, this study did identify a large effect size observation in distance covered at HIA speeds in the CG condition. Interestingly, although the wearing of CGs offered limited performance benefits in previous research (16,21), the intermittent protocols implemented during these studies may not have validly represented the frequency of HIA reported for team sport-specific PHIIE (4,28,31). Given the previously reported anaerobic and circulatory benefits of CGs (6,10,26) along with the observation that CGs may increase distance covered during HIA within intermittent exercise (21), it may be hypothesized that the benefits of wearing WBCGs may be more pronounced with the higher frequencies of HIA. Thus, the purpose of the current study was to determine the effects of wearing WBCGs on selected physical and physiological measures during a team sport-specific PHIIE protocol.
Experimental Approach to the Problem
Several manufacturers claim that wearing CGs will improve performance during team sport-specific PHIIE with limited empirical evidence being available within the scientific literature (16,21,23). However, there are presently no data examining the effects of wearing WBCGs on controlled team sport-specific PHIIE that validly represents match play within a controlled environment. This study attempted to examine the performance and physiological effects of wearing WBCGs on team sport-specific PHIIE using a laboratory-based simulation on a nonmotorised treadmill. Each subject completed the 45-minute PHIIE protocol, which has previously been developed using several time-motion analysis studies of team-sport match play (1), in randomly assigned WBCG and control conditions. During the protocol, physical performance measures of total distance, velocity-specific distances, and HIA speeds were analyzed because of their relationship with team-sport performance (4,27). Selected physiological measures included HR, o2, [BLa−], and tissue oxygenation index (TOI) and tissue hemogolobin index (nTHi) were recorded and analyzed to explain any performance effects of WBCGs. Based on the findings of previous studies examining the effects of wearing WBCGs (6,7,10,25), it was hypothesized that wearing WBCGs would enhance PHIIE performance and provide significant physiological benefits.
Eight amateur male team-sport athletes ([ ± SD] age: 20.6 ± 1.2 years; body mass: 72.9 ± 5.9 kg; body fat: 10.1 ± 2.0%; and o2max: 57.5 ± 3.7 ml·kg−1·min−1) volunteered to participate in the current study. This sample size was proposed by Sirotic and Coutts (30) who suggested that between 5 and 9 subjects would be required to detect a 10% change in the majority of physiological and performance variables across a similar nonmotorised intermittent protocol. All subjects were competitive for a minimum of 3 years before testing, which occurred during the middle of the competition season after 2-4 months of sport-specific base and precompetition training. All subjects trained for 2 hours, 3 times a week while also competing in 1 weekly match. Before participating, subjects were informed of the experimental risks and provided written informed consent. All subjects were also screened for medical contraindications that may have excluded them from participation. Ethical approval for the research was granted by a University Human Ethics Committee.
Whole-Body Compression Garments
The WBCGs used in the present study were unisex full-length bottoms and long-sleeved tops (Sport Skins Classic, Skins™, Campbelltown, NSW, Australia), which comprised of 76% nylon and meryl microfiber, and 24% roica spandex. Each WBCG was fit according to manufacturer's guidelines using each subject's stature and body mass. The lower-body CG ran from the superior aspect of the medial malleolus of the ankle to fractionally superior to the iliac crest. The upper-body CG covered the whole torso and ran to the radiocarpal joint of both arms. A Kikuhime pressure monitor (TT MediTrade, SorØ, Denmark) measured the compression of the WBCG at several locations (Figure 1). The control condition consisted of wearing regular running shorts and a loose playing shirt, typical of that worn by soccer players.
Initially, all subjects completed a 15-minute familiarization run on the nonmotorized treadmill (NMT) (Tramp Model, Woodway, Waukesha, WI, USA). In a separate session, subjects completed a second 10-minute familiarization session that was followed by an assessment of peak sprint speed (PSS). The PSS was measured to determine the target speeds for each movement category defined in the PHIIE protocol. Ten minutes after the completion of the PSS test, subjects completed a discontinuous incremental test to exhaustion to determine o2max. After this, on 2 separate occasions, subjects returned to the laboratory to complete the 45-minute PHIIE protocol in randomly assigned control and WBCG conditions. Before each session, subjects were instructed not to undertake any high-intensity exercise for 24 hours, and not to consume food or drink fluids containing caffeine for 2 hours before each testing session. All subjects were given a minimum of 72 hours of rest between testing sessions. Subjects completed a Dietary Record Sheet before the first testing session, which was photocopied and returned to the subject to be replicated before to subsequent testing sessions. All tests were completed within standardized laboratory conditions at 22 ± 2° C and <70% relative humidity and at the same time of day to avoid circadian variances. Participants completed all exercise testing on the NMT wearing regular running footwear.
Assessment of Peak Sprint Speed
Before the assessment of PSS, subjects completed a warm-up consisting of 10 minutes of jogging and then 5 minutes of dynamic stretching. To minimize intersubject variability, subjects were assessed for their individual PSS as the target speeds for each movement category for the PHIIE protocol remained relative to their maximum speed. Each subject completed 3 maximal 3-second sprints that were separated by 2 minutes of jogging. Peak sprint speed was taken as the highest speed recorded during any 3-second sprint.
Assessment of Maximal Oxygen Uptake
After PSS assessment, each subject completed an incremental run to exhaustion to determine o2max in the control condition. The test commenced at a speed of 8 km·h−1, and increased by 2 km·h−1 every 3 minutes until a [BLa−] of 4 mmol·L−1 was reached. Each stage was separated by a minute rest to allow for capillary blood sampling. Once a [BLa−] of 4 mmol·L−1 was reached, the subjects ran continuously with their speed increasing by 0.5 km·h−1 every minute until volitional fatigue or o2max was attained. Determination of o2max involved the observation of any 2 of the following criteria: (a) volitional exhaustion; (b) a respiratory exchange ratio to or greater than 1.15; (c) a plateau in oxygen consumption (increase <2 ml·kg−1·min−1) despite an increase in workload; and (d) attainment of age-predicted maximal HR (220 − age). o2max was defined as the highest 30-second average observed during the incremental test (24).
Prolonged High-Intensity Intermittent Exercise Protocol
The 45-minute PHIIE protocol was based on several time-motion analysis studies of team-sport match play and has previously been reported (1). The protocol consisted of 3 repetitions of a 15-minute activity profile that incorporated 6 individual running speeds (standing [0% of maximal sprint speed (PSS)], walking [20% PSS], jogging [35% PSS], running [50% PSS], fast running [70% PSS], and sprinting [100% PSS]). The final 2 minutes of each 15-minute period included a series of self-selected high-intensity runs (variable runs), during which each subject was instructed to cover as much distance as possible across the interval without sprinting. Walking, jogging, and running were classified as LIA, whereas fast running, sprinting, and variable runs were HIA. A graphical representation of the protocol is given in Figure 2.
Before commencing the PHIIE protocol, subjects completed a 15-minute warm-up, which consisted of 5 minutes of jogging, dynamic stretching, and then a series of high-intensity activities, which included at least 2 6-second sprints. During the protocol, subjects were attached to a wall with a tether belt that was adjusted to allow maximal stride length during sprinting.
Subjects were requested to follow specific target speeds as close as possible throughout the protocol. A computer monitor was placed at eye level that displayed both target speed and actual speed of the treadmill belt. A custom-written Labview program (National Instruments, Austin, TX, USA) provided audible commands and displayed target speeds for each activity mode. Before each change in speed, 3 audible tones were played, which was followed by an audible command to inform the subject of the upcoming activity. For example, if the participant was walking and the next speed was a run, then the audio sequence “beep”…“beep”…“beep”…“run” would be heard. When the “run” instruction occurred, the target speed on the monitor changed to the corresponding speed. During a variable run, the monitor displayed “999” and subjects were instructed to run as fast as possible without sprinting. During sprinting, subjects were instructed to simply sprint as fast as possible regardless of the target speed.
Treadmill running belt velocity and distance were measured using a reflective object sensor (OPTEK OPB608B, OPTEK Technology, Carrollton, TX, USA). All measures of velocity and distance were collected at a sampling rate of 10 Hz and averaged every second using custom-written Labview software (National Instruments). Reliability trials of the total distance covered and maximal sprint speed during the PHIIE protocol were acceptable (distance covered: TEM% = 2.3; maximal sprint speed; Technical Error of Measurement% = 4.0).
Blood-lactate concentration was determined from capillary blood samples drawn from hyperaemic fingertips. Samples were analyzed using an Accusport Portable Lactate Analyzer (Boehringer Mannheim, Mannheim, Germany). Capillary blood samples were taken during the minute-rest period during and at the completion of the incremental test. During the PHIIE protocol, [BLa−] samples were taken at the 13th, 26th, and 39th minutes.
Heart rate was continually recorded at 5-second intervals during all exercise testing using a Polar s610i HR monitor (Polar Electro, Oy, Finland). After testing, HR data were downloaded to a personal computer for analysis using Polar Precision Performance Software v4.0 (Polar Electro).
Expired gas measures were continuously measured across the incremental test, and for repeated 5-minute periods that commenced at the ninth, 13th, and 23rd minutes of the PHIIE protocol. Expired gas analysis was performed using a TrueOne™ 2400 Metabolic Measurement system (Parvomedics®, Sandy, UT, USA). Subjects wore a headpiece containing a mouthpiece and flowmeter along with a nose clip during all respiratory gas testing (Parvomedics®). Before each test, the flowmeter was calibrated with a 3-L syringe (Hans Rudolph Inc., Shawnee, KS, USA) and the analyzers were calibrated against gases of known concentrations (Reference: 21 ± 0.2% O2; Calibration: 12.1 ± 0.2% O2, 5.05 ± 0.1% CO2) according to the manufacturer's instructions. Real-time display of gas concentration and flow measures for each test was performed and displayed using a personal computer.
Local measures of muscle oxygenation from the v. lateralis muscle were continuously monitored using a NIRO-200 near-infrared spectroscopy (NIRS) system (Hamamatsu Photonics, Hamamatsu City, Japan). The NIRS probe consisted of 2 laser diodes that directed light at 4 different wavelengths (775, 810, 850, and 910 nm) into the working muscle. The use of the NIRO-200 has been previously documented (13,32). The NIRS system provided measures of changes in hemoglobin [Hb (μM)], oxyhemoglobin [HbO2 (μM)], tissue oxygenation index [TOI (HbO2/Hb) (%)], and tissue hemoglobin index [nTHI (HHb + HbO2) (AU)]. Before the application of NIRS assembly, the application area was shaved to remove excess hair and covered with clear plastic to ensure that sweat and oils did not disturb optode sensitivity. The probe was placed 14 cm superior to the border of the patella on the left leg over the belly of the v. lateralis. The optodes were placed in a dark plastic holder, which maintained their position of fixation to each other. The interoptode spacing was maintained at 4 cm throughout all testing. The optode assembly was secured to the skin with tape, covered in dark cloth, and secured to the thigh using an elastic bandage. This provided free movement, while restricting the NIRS assembly from large movement artifacts, and any reductions in incidental light interference. All leads from the NIRS were secured using tape to further reduce any movement artifact.
Before each test, the subject was instructed to stand stationary while the NIRS signal was manually zeroed, to ensure changes in muscle oxygenation measures were relative to rest. This was performed after the subject was standing for at least 30 seconds. Measures of TOI and nTHI were continually recorded across the PHIIE protocol.
Means and SDs [ ± SDs] were calculated for all descriptive, physiological, and performance measures. A Greenhouse-Geisser adjustment was used to ensure the sphericity of all measures and reduce the likelihood of a type I error. Paired sample t-tests were used to determine significant conditional differences in total distance covered and distances covered in LIAs and HIAs during the PHIIE protocol. Furthermore, a 2 (condition) × 3 (time) repeated-measures analysis of variance was used to examine changes in speed measurements and physiological characteristics across the 3 15-minute repetitions. All parametric statistical analyses were performed using Statistical Package for Social Sciences software (SPSS Inc., Chicago, IL, USA). Statistical significance was accepted at p ≤ 0.05.
After this, magnitude-based inferences were used to identify practical differences in the performances and physiological responses between conditions (22). This method computes the chance that the true effects are substantial when a value for the smallest worthwhile change is entered. The magnitude of the observed differences across conditions was quantified using effect size statistics (η2) where 0.6, 1.2, and 2.0 were representative of moderate, large, and very large effects, respectively (11). Confidence limits for the true mean values were estimated with the unequal-variances statistic computed between the control and WBCG conditions. The likelihood of the true effects was practically beneficial, neutral, or detrimental for the smallest worthwhile change. If the likelihood of benefit and detriment were both larger than 5%, then the true effect was considered unclear. If the likelihood of benefit and detriment were equal to or less than 5%, quantitative probabilities of their practical significance were assessed qualitatively as previously used (22). The smallest worthwhile change for the performance variables of interest was approximately equal to the TE of the PHIIE protocol that was used. The smallest worthwhile changes for the physiological variables investigated were calculated as one-fifth of the between-subject SD for each condition (22). All magnitude-based inferences were performed using Microsoft Excel (Microsoft Corporation™, Redmond, WA, USA).
The distance covered during the LIA and HIA movement categories along with total distance covered in the control and WBCG conditions along are displayed in Figure 3. The total distance covered was likely to be practically greater (88:10:2%; η2 = 0.6) in the WBCG condition (5.88 ± 0.64 km) than in the control condition (5.42 ± 0.63 km). A likely practical increase (83:14:3%; η2 = 0.6) was also observed in distance covered during LIA movements in the WBCG condition (4.58 ± 0.57 km) compared with the control condition (4.21 ± 0.51 km).
The mean speeds of each HIA movement category across the PHIIE protocol for each condition are given in Table 1. The mean variable run speed was observed to be likely greater (92:6:1%; η2 = 0.6) in the WBCG condition (19.7 ± 1.5 km·h−1) when compared with the control condition (18.4 ± 2.4 km·h−1).
The mean physiological responses across the PHIIE protocol are displayed in Table 2. A significant effect of time was observed for mean HR [F(2,7) = 28.211; p < 0.01)], average nTHI [F(2,7) = 5.497; p < 0.05)], and postsprint TOI [F(2,7) = 4.177; p < 0.05)] across the repeated 15-minute periods. Further, there was a significant interaction between condition and time for HR [F(2,7) = 40.410; p < 0.01)] and average nTHI [F(2,7) = 4.732; p < 0.05)]. Magnitude-based inferences revealed that average TOI (87:11:2%; η2 = 0.6) and postsprint TOI (75:20:5%; η2 = 0.6) were likely to be higher in the WBCG condition. Figure 4 displays a typical TOI response in the control and WBCG conditions across the PHIIE protocol from a single representative subject.
The purpose of the current investigation was to examine the performance and physiological effects of wearing WBCG during a team sport-specific PHIIE simulation. To date, limited research has reported on the effect of wearing WBCG on simulated team-sport match play, and little is known about their effect on intermittent exercise (16,21,23). From the present study, with a moderate-strength effect, a likely benefit of wearing WBCG was observed on total distance covered, distance covered during LIA, and the variable self-selected high-intensity running speed. In combination with these physical benefits, a likely increase was observed in both the average and postsprint TOI in the WBCG condition. Although limited data are available to demonstrate a strong relationship between increased TOI and physical performance, it may be likely that this remains a physiological mechanism associated or responsible for the likely performance benefits observed.
The likely increases in total distance covered and distance covered during LIA in the WBCG contrasts previous work that has investigated the effect of WBCG on intermittent exercise performance (16,21). Duffield and Portus (16) reported no significant effect of 3 different WBCGs on total distance covered or sprint ability in 10 amateur cricket players during a 30-minute intermittent running protocol. Similarly, Higgins et al. (21) reported no significant effect of lower-body CG on total or LIA distance covered. However, the intermittent protocols in these studies may have underestimated the frequency of HIA bouts during field-based team-sports (∼1:20) (4,28,31). Further, these studies may not have had relative target speeds for all movement categories assessed that may have reduced the accuracy of distance measures and consistency of LIA movements. The increase in HIA frequency in the present study further highlights the possibility of faster anaerobic recovery in the WBCG condition (6,10). The faster recovery may be the result of a more active recovery (increased LIA speed) between or after HIA bouts, which may help explain the increased distance covered across the protocol. Further, the increase in LIA distance may possibly be related to previously reported improvements in energy efficiency at low-intensity speeds (i.e., 12 km·h−1) from wearing only lower-body CG (7).
Previous research has suggested that distance covered during field-based team sports is positively correlated to competition level (4,28) and increases in physiological capacities (20). Therefore, the observed likely increase in LIA movements has specific implications to team-sport performance, as it is suggested that players may remain continuously active when not undertaking bouts of HIA. Burgess et al. (8) have put forward that continual movement during a soccer match allows players to create more opportunities for attacking plays and reduce player density on the field. Furthermore, Bangsbo (4) suggested that team-sport athletes likely compromise their LIA volume across a match to assist passive recovery between HIA bouts. However, previous research suggests that active recovery, rather than passive recovery, increases time to exhaustion during intermittent exercise (17). This further supports the notion that wearing WBCG during PHIIE allows quicker recovery after bouts of HIA, through an improved ability to complete LIA. The observation that wearing WBCG speeds anaerobic recovery after HIA bouts also lends itself to this hypothesis (6,10). Therefore, the present data are the first to suggest that wearing WBCGs may improve physical performance during team sport-specific PHIIE and further investigation may be required to examine if this remains relevant to actual team-sport performance.
Separately, the present data demonstrated that wearing WBCG did not increase HIA distance covered or PSS across the PHIIE protocol. This finding is in contrast with that of Higgins et al. (21) who reported that wearing CGs provided increases in HIA distance during a netball-specific field protocol. Again, the protocol used by Higgins et al. (21) may have underestimated the HIA demands of team sports, and failed to use relative target speeds for all movement categories within the simulation. This may have exaggerated the affects of CGs on PHIIE. The present study used a valid and team sport-specific pattern of HIA that was relative to each participant's PSS. The present study identified no effect of WBCG on sprinting performance, a result that is supported by past research (5,16). Nevertheless, a likely benefit of wearing WBCG was observed in self-selected high-intensity running speeds across the PHIIE protocol. This suggests that WBCG increased the self-selected high-intensity running speed, which may reflect the previously identified reductions in muscle oscillation during dynamic movements while wearing CGs (15,25). Investigators have speculated that such reductions in oscillation may assist with enhancement of technique during HIA and also minimizing fatigue (25). Alternatively, the increase in self-paced HIA running speed may reflect the circulatory and oxygenation changes with the wearing of WBCG. During repetitive HIA, there is a reported reduction in the glycolytic rate within the working muscle (19) that may reduce the ability to maintain energy provision during the repeat bouts of HIA. In the present study, the wearing of WBCG may have slowed or decreased this reduction in glycolytic rate, through improvements in anaerobic waste removal (6,10) and/or improved oxygen availability as demonstrated by past (2,29) and present data.
The present study is the first to report on the muscle oxygenation responses during team sport-specific PHIIE while wearing WBCG. Wearing WBCGs demonstrated a likely increase in average and postsprint TOI across the PHIIE protocol. This supports previous research that has reported similar effects of wearing CGs on muscle oxygenation trends during low-intensity walking in clinical patients (2) and well-trained cyclists across a 1-hour time trial (29). Investigators have reported that the circulatory benefits associated with wearing CGs are responsible for such increases in muscle oxygenation (2). Nevertheless, previous findings have suggested that similar increases in oxygen availability to the working muscles may minimize the progression of muscular fatigue during intense intermittent exercise (33), either as a result of enhanced anaerobic recovery or a minimized anaerobic energy contribution at the onset of an HIA bout. As such, wearing CGs may help to improve oxygen availability within peripheral musculature during PHIIE, helping to speed the reoxygenation of the depleted oxyhemoglobin and oxymyoglobin stores, and in turn, enhance metabolic recovery after bouts of HIA. Further, wearing WBCGs appeared to improve regional blood flow within peripheral muscles, which may help improve anaerobic waste removal (6). However, the physiological benefits that result from wearing WBCGs appear limited to changes in circulatory and oxygenation responses within the peripheral musculature because no significant effect was observed in o2 or [BLa−] responses during the intermittent exercise. In contrast, a significant increase in o2 has been reported with the wearing of CG; however, this was only during steady-state running at 12 km·h−1 (7). Therefore, wearing WBCG appeared to improve the metabolic environment within peripheral muscles during team sport-specific PHIIE; however, these benefits were not observed in global measures of exercise intensity and efficiency.
In the present study, HR was observed to significantly increase with time across the PHIIE protocol with the wearing of WBCG. Investigators have suggested that the circulatory benefits associated with wearing CGs include improving venous return, subsequently increasing stroke volume and cardiac output, hence lowering HR (3). Nevertheless, previous research has reported minor increases in skin temperature (∼1.5-2.0° C) during intermittent exercise protocols when wearing CGs (16,23). These findings indicate that the heat loss capacity of peripheral muscle may be reduced while wearing CG, as no such effect has been observed in core temperature. As such, HR may have potentially increased in the present study as a result of cardiovascular drift in response to impaired thermoregulation responses. Such a thermoregulatory effect may potentially alter the superficial blood flow responses within peripheral muscles. Although past investigations have reported that NIRS measures are significantly affected by large increases in muscle temperature (∼41° C) (13), no data have reported any effect during exercise with the wearing of CGs under typical temperatures, such as those reported by Houghton et al. (∼27-30° C). Furthermore, the increase in muscle temperature because of energy metabolism, thermoregulation, and other processes are not separately identifiable, and therefore, it is difficult to suggest whether the increased regional blood flow responses cause blood pooling within the peripheral muscle as a result of an impaired heat loss capacity or an improved blood flow to the muscle. Therefore, future research should be directed at identifying the direct cause of increased blood flow responses with the wearing of WBCGs by counteracting any thermoregulatory effects.
The present study has reported a number of performance and physiological benefits of wearing WBCGs during team sport-specific PHIIE, with a small number of practical limitations. Firstly, the PHIIE protocol is not a direct indicator of team-sport performance, because it fails to assess skill, tactical considerations, or the energy cost of performing unorthodox movements. Additionally, the present study focused on regional muscle oxygenation changes in one agonist muscle of the running action (v. lateralis). Although this muscle possesses a primary role in running, other synergistic muscles (e.g., medial gastrocnemius) have been observed to display varied oxygenation responses (9,33). Furthermore, given that the greatest external compression is applied at the ankle, the effects of CG on muscle oxygenation responses may differ across the compression gradient. As such, future research should investigate the effects of wearing WBCG on actual team-sport match play performance, and examine the muscle oxygenation responses at various segments across a limb under graduated compression.
In conclusion, the present data demonstrated that wearing WBCG likely increases the total distance covered during a team sport-specific PHIIE protocol. This benefit resulted from an improved ability to cover distance through LIA between the repeated bouts of HIA. This improvement in distance covered was concomitant with higher muscle oxygenation levels observed in the WBCG condition. This relationship may suggest that the anaerobic energy contribution and/or anaerobic recovery was minimized and quickened, respectively. Past research has suggested that such improvements in distance covered during team-sport match play may be related to improvements in performance or desirable tactical strategies (4,8,28). Therefore, wearing WBCGs appears to be beneficial to PHIIE performance, and may offer possible physiological benefits that require further investigation.
There were 3 main practical applications of the findings from the current study: (a) wearing WBCG is likely to increase the total distance covered during team-sport match play; (b) this is likely to be the result of an increased distance covered throughout low-intensity activities (i.e., walking, jogging) across a match; and (c) wearing WBCGs changes the muscle oxygenation responses of lower-limb muscles, which may help to minimize fatigue across match play. These findings support the wearing of WBCGs throughout team-sport match play or PHIIE because such improvements in distance covered may be beneficial with regards to tactical plans and speeding recovery between bouts of HIA. Therefore, coaches, sport scientists and athletes associated with team sports may implement the wearing of WBCG during training and competition to take advantage of these demonstrated benefits.
The authors would like to acknowledge Skins™ Compression Garments for their contribution of product in kind and Central Queensland University for their financial support. Also, they would like to acknowledge Mr. Gregory Capern for his technical assistance throughout the study.
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Keywords:© 2010 National Strength and Conditioning Association
compression stockings; team sport; muscle oxygenation