Introduction
Compression garments have been used as an intervention in a variety of contexts, such as during recovery from an exercise stimulus, particularly heavy resistance training (8). The key factor is the role a compression garment is expected to play (e.g., mechanical support, proprioceptive cues, etc.). The mechanisms that mediate an effect are related to the type of garment and its compression and construction (e.g., enhanced oxygenation, improved blood flow and removal of metabolites, dynamic casting, extreme mechanical support in lifting suits) (8,9). Thus, matching garments to their intended use is an important consideration in any garment choice.
Compression garments have also been used during the athletic activity itself, and not just for the enhanced comfort but also for improved performance, such as the increase in power endurance shown as a result of wearing compression garments in collegiate volleyball players (6). Some of the benefits on power performance have been suggested to be due to improvements in proprioception. This is most likely due to additional “proprioceptive cues” arising from the compression forces on the skin stimulating mechanoreceptors, which detect pressure enabling an enhanced kinesthetic sense during movement (6). In a later study, Kraemer et al. (7) demonstrated enhanced proprioception with a compression garment enhanced joint position sense at the hip and improved power endurance during the repetitive jumping testing protocol.
As improvements in power endurance have been attributed to compression in a laboratory setting with tasks such as improving repetitive jumping curves, other types of activity may also benefit from proprioceptive enhancements that are more specific sport skills. Although it seems logical that different sport skills that require coordinated movement across multiple joints could be positively affected by increases in proprioception, very little research exists to explore such a concept. In fact, to the authors' knowledge, only 1 study has been previously conducted in this area of investigation. In this classic study, Duffield et al. (1) evaluated the throwing performance of cricketers while wearing a variety of compression garments including a control condition without compression. The authors failed to find any benefit in terms of throwing for maximum distance or accuracy, which one might have expected as maximal power (e.g., maximal power in a countermovement vertical jump) that has not been shown to improve with various types of long-term wear compressive garments because of the lack of any mechanical assistance (6,7).
Another factor that may be impacting performance resulting from compression garments is the perception of benefit on behalf of the athlete. Because of the nature of compression as an intervention, it is difficult to have a true control for comparison that the individual is not obviously aware of. This concept of positive “garment feel” during an activity was demonstrated by Kraemer et al. (7), who measured the subject's perceptions of how they felt the garment was affecting jumping ability without having performance feedback during the set of repetitive jumps. The subjects reported a significant perception of improvement over the control condition of no compression, and it was suggested by the authors that this played a role in improved jumping performance (7). Thus, in addition to proprioception, garment feel and comfort may play a role in any improved performance from compression garments. However, as noted by MacRae et al. (10), few data are available on the comfort of compression garments and wearer acceptability. This becomes a particularly important aspect of this area of research, as if athletes are uncomfortable and do not enjoy wearing the garment, either performance will not improve or the garments will simply not be worn.
Overall, previous research has implicated a link between the use of compression garments and improved proprioception in movements. However, the link between compression garments and ultimately an influence on sport skill performances remains elusive (10), which may be due to the subtlety of benefits from enhanced proprioception. To bring these differences out, perhaps high-level athletes are required who are gifted in reproducible movements where small changes are much more likely to be elucidated. Therefore, the purpose of this study was to assess whether upper-body compression garments can be used to improve proprioception and determine the extent of how comfort may be a factor in their perceived performance. Thus, a secondary purpose of the study is to quantify the comfort of compression garments worn by these athletes.
Methods
Experimental Approach to the Problem
To assess the impact of compression garments on sports performance, 2 sports that are highly technical in nature were chosen: baseball pitching and golf. These skills require the close coordination of gross movements repeatedly and are sports where very small absolute distances can be the difference between success and failure, such as making or missing a putt or throwing a ball or strike. A counterbalanced within-group design was used. At least 7 days before data collection, subjects were provided with an experimental garment and encouraged to familiarize themselves with the garment as much as possible. Subjects performed the respective baseball or golf protocol wearing either their typical noncompressive clothing or the experimental compression garment (described below). Subjects were instructed to wear the same lower-body clothing for each trial and the same footwear. Measures pertaining to velocity and accuracy were chosen for both sports, because changes in power performance and proprioception would be manifested in such dependent variables.
Subjects
Eleven National Collegiate Athletic Association (NCAA) Division I collegiate male pitchers (starters and relievers) (age: 21.0 ± 2.9 years; height: 181.0 ± 4.6 cm; weight: 89.0 ± 13.0 kg; body fat: 12.0 ± 4.1%) and 10 NCAA Division I collegiate male golfers (age: 20.0 ± 1.3 years; height: 178.1 ± 3.9 cm; weight: 76.4 ± 8.3 kg; body fat: 11.8 ± 2.6%) were recruited from the University of Connecticut athletic teams. The study was approved by the Institutional Review Board for use of human subjects in research at the University of Connecticut. Each subject signed a university-approved informed consent document after the risks and benefits of the study were explained to them.
Garment
The garment was custom-made for the study by Under Armour but will soon be made commercially available. The body of the garment was 85% nylon and 15% elastane (also known as spandex). An insert was added to the garment, in the shape of an X (Figure 1) with the objective of coordinating the extreme positions of the trunk from top to bottom. The insert was 80% nylon and 20% elastane.
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Figure 1: The compression garment that was used in the study. The body of the garment was 85% nylon and 15% elastane. The insert of the garment, the “X” shape, was 80% nylon and 20% elastane.
Baseball
Logistics
The pitchers used the University's indoor baseball facility, which ensured a consistent environment across testing sessions. All pitchers had complete familiarity with the environment because it was where all their winter practices took place. A strike zone–sized net was placed over home plate, and a small target was placed in exactly the center of the strike zone. Pitchers threw off of an indoor mound at regulation height (25 cm) and distance from home plate (18.66 m). A video recorder (Panasonic 3CCD, Secaucus, NJ, USA) was placed directly behind home plate, which was later analyzed with the use of Dartfish (Fribourg, Switzerland) technology to measure the distance each pitch crossed home plate from the center of the strike zone. The velocity of each pitch was measured with a radar gun (Stalker, Plano, TX, USA). All testing was performed in isolation, with only the study personnel observing each testing session.
Procedures
For assessment, an analysis of a typical bullpen session was used to assess the impact of the garment. After consulting with the coaches, a session of 25 pitches was chosen to allow a sample large enough to stimulate an element of fatigue. The velocity and location of each pitch were assessed because these are 2 of the most important variables in pitching performance. On arrival to the baseball facility, subjects performed their own typical warm-up routine consisting of dynamic stretches and soft toss. Each pitcher then performed 10-15 warm-up pitches from the mound. Once the subject indicated that they were ready to begin data collection, the velocity of the next 25 pitches was recorded and was later analyzed for location. Pitchers were instructed to throw only their typical fastball at a previously described target placed in the center of the strike zone.
Golf
Procedures
Golf data collection took place at the University's indoor golf facility. All of the facilities used by the golfers were provided by the athletic department's golf facility, and therefore all subjects had complete familiarity with the equipment. A range of golf skills were chosen, ranging from simulated shots from the tee, to the approach, to shots around the green and putting to assess the impact of the garment on a wide variety of aspects of the golf game.
Subjects were instructed to carry out their typical warm-up routine, which consisted of dynamic stretches and dry swings. The first test drill consisted of 10 full swings with the subject's own driver within a golf simulator (Full Swing Golf, San Diego, CA, USA), which measured the total distance the ball would have traveled and the total deviation of the ball from the center line. The subjects were instructed to take typical swings with the aim of maximizing both distance and accuracy. The next test drill was aimed to assess approach shot accuracy, where subjects were instructed to aim at a target 120 yards (109.7 m) away. This drill used TrackMan (Brighton, MI, USA) technology, which recorded the total distance the ball would have been from the target. The chipping and putting test drills then used an indoor putting green. The chipping drill consisted of 10 chips, with the subjects club of choice 25 feet (7.62 m) from the target. After each chip, the distance of the ball from the center of a hole-sized target was recorded before removing the ball from the green so that it would not obstruct the subsequent attempts. The putting drill involved 10 attempts at a hole placed 10 feet (3.04 m) away. If the putt was unsuccessful, the total distance from the ball to the center of the hole was measured. If the putt was successful, it was recorded as a putt made. All testing was performed in isolation, with only the study personnel observing each testing session.
Questionnaires
Both golfers and pitchers completed a questionnaire after each respective visit. All questions were answered pertaining to a 5-point scale. The first 3 questions pertained to comfort, the perception of the garment improving performance, and a rating of how much the subject enjoyed wearing the garment. These questions were answered using the following scale: 1: strongly disagree, 2: disagree, 3: neutral, 4: agree, 5: strongly agree. The final question asked the subject to complete the sentence “The amount of compression was…” with the possible answer being: 1: far too much, 2: too much, 3: just right, 4: too little, 5: far too little.
Statistical Analyses
Statistical evaluation of the data was accomplished using a 2-way analysis of variance with repeated-measures or a 2-way analysis of variance with a block design (i.e., garment or control) when and where appropriate, and Fisher's or Tukey post hoc tests were used when appropriate. Data sets went through initial analysis for statistical assumptions and missing data. If not met, data were transformed (i.e., log10) and data were reanalyzed. Thus, all of the assumptions for linear statistics were checked and were met before analyses. Statistical significance in this study was chosen as p ≤ 0.05.
Results
In the baseball subjects, there was a significant (p ≤ 0.05) improvement in pitching accuracy, as measured by the mean distance from the target while wearing the compression garment (Figure 2). It was also identified that the compression garment led to a significant (p ≤ 0.05) improvement on the X axis, but not the Y axis.
Figure 2: Pitching accuracy of 11 Division I collegiate pitchers, assessed by mean distance (in meters) of pitches from the center of the strike zone while wearing control and compression garments. *Significantly (p ≤ 0.05) different from the corresponding group.
There were no differences in strikes thrown or fastball velocity (Table 1).
Table 1: Pitching performance of 11 Division I collegiate pitchers while wearing a compression or a control garment.*
For the golf subjects, there were no differences in driving distance (Figure 3A), but there were, however, significant (p ≤ 0.05) improvements in driving accuracy (Figure 3B), as well as approach shot and chipping accuracy (Figures 4 and 5, respectively).
Figure 3: Driving distance (A) and accuracy (B) results of 10 Division I collegiate golfers while wearing control and compression garments. *Significantly (p ≤ 0.05) different from the corresponding group.
Figure 4: Accuracy, as measured by deviation (in feet) of an approach shot from a target 120 yards away in 10 Division I collegiate golfers while wearing control and compression garments. *Significantly (p ≤ 0.05) different from the corresponding group.
Figure 5: Chipping accuracy, as measured by deviation (in inches) of a chip shot taken 25 feet from the target in 10 Division I collegiate golfers while wearing control and compression garments. *Significantly (p ≤ 0.05) different from the corresponding group.
There were no differences in putting accuracy or putts made (Table 2).
Table 2: Putting performance of 10 Division I collegiate golfers, as measured by distance from target after a 10-foot putt and total putts made, while wearing a compression or a control garment.*
In the perceptual scales, pitchers reported a significant (p ≤ 0.05) improvement in performance and a significantly (p ≤ 0.05) greater level of enjoyment in wearing the compression garment (Table 3). Golfers reported significantly (p ≤ 0.05) greater comfort while wearing the compression garment.
Table 3: Scores related to perceptual scales while wearing a compression or a control garment in 11 Division I collegiate baseball pitchers and 10 Division I collegiate golfers, respectively.
Discussion
The primary finding of this study is that the certain aspects of performance of baseball and golf skills that require coordinated movements across multiple joints can be enhanced with the use of compression garments in high-level collegiate athletes. These performance improvements were manifested as improved accuracy in both baseball pitching and a variety of golf shots. In accordance with a paradigm put forward in previous work (6), it seems the act of providing a compressive force on the skin can enhance proprioception of upper-body movements in these sports.
In agreement with Duffield et al. (1) who studied throwing performance in cricketers, this study failed to find any impact on variables related to power, either in driving distance in golfers (Figure 3A) or, just as in the aforementioned study, any change in throwing velocity (Table 2). It seems that although previous research has shown that compression provided benefits of power endurance in repetitive jump tests (6,7), such an endurance effect does not seem to transfer to more complex sport skills with implements. Whether this is influenced by the use of only an upper-body garment remains speculative. In these sport skills, the lower body is still a major contributor to power both the baseball pitch and the golf swing. However, the focus of this study was coordinating the rotational movements involved in these sport skills.
We did find differences in some of the accuracy measures in pitching (Figure 2) and in a variety of golf shots, including driving (Figure 3), approach shots (Figure 4), and chipping (Figure 5). There may be a variety of factors that contributed to these contrasting findings compared with that of Duffield et al. (1) who used only a small number of throwing attempts for assessment of accuracy, totaling 6. Secondly, they did not use exact measurements of distance from a target, but rather used scoring zones and allocated points for each attempt, with less points awarded the further the throw was from the target. We benefitted from their study by increasing the measurement sensitivity in our study and using elite collegiate athletes.
The results of our study clearly implicate a possible role of proprioception feedback in the act of throwing. This is in somewhat contradiction of recent study that suggested proprioception does not play an integral role in throwing performance, at least not when it is measured in isolation (2). These authors acknowledged that the entire kinetic chain should be assessed with the use of an outcome variable from the act of pitching itself. Therefore, not only including both laboratory measurements but also the use of sport-specific tasks in any assessments of the influence of a garment on performance seems to be important.
Of the effects on golf performance, demonstrating improved performance in this study is somewhat of a novel finding. Studies pertaining to golf have previously shown a tenuous link to proprioception, in a very similar manner to those regarding throwing performance, which we have just discussed. Although fatigue has been shown to reduce proprioception and result in changes in biomechanics in resistance exercise (4,5), Higdon et al. (3) demonstrated that fatigue did not affect any biomechanical measurements in the golf swing. However, the authors concluded that perhaps the measurements that were used failed to detect the differences. As can be seen from previous research in both throwing and golf studies, changes in proprioception can be very difficult to detect and the differences may be only be subtle. This again highlights the importance of measuring changes in proprioception in a sports context as it pertains to high-level athletes, because they may be the individuals who have movement patterns ingrained enough to quantify any of these subtle differences.
In addition to demonstrating changes in proprioception, this study quantified the comfort level of compression garments, an area of research that has been documented as lacking (10). Surprisingly, only golf subjects expressed a greater level of comfort for the compression garment than what they typically wear (Table 3) and did not believe this comfort to have improved their performance. However, pitchers did not express greater comfort but did report enjoying wearing the garment and perceived an improvement in performance (Table 3). Although these results likely demonstrate the cultural differences across sports and how different athletes may have different preferences for their uniforms, it is important to note that the baseball pitchers did not find the garment any less comfortable than what they typically wear. In this regard, there is no trade-off for the improved sporting performance, because there is no loss in comfort with the use of these garments.
Practical Applications
An upper-body compression garment that is worn under their uniform could have an impact on their sporting performance, particularly in terms of influencing some aspects related to the accuracy of movements. It seems that high-level athletes may see subtle differences that result from wearing such an upper-body compression garments. In addition to potential performance benefits, there may be psychological advantages in terms of comfort, feel, and perception of performance. There does not seem to be any negative effects of using such an upper-body compression garment worn under typical baseball and golf uniforms.
Acknowledgments
The authors thank their student-athlete subject volunteers and head sport coaches as this made the study possible. They also thank their other undergraduate research assistants and their study physician, Dr. Jeffery Anderson, MD, for his medical supervision of the study. This study was supported by a grant from Under Armour, Baltimore, MD, USA. The results of this study do not constitute endorsement of the product by the National Strength and Conditioning Association or university authors.
References
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