Gait & Posture 39 (2014) 804–809
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
What is the effect of compression garments on a balance task in female athletes? Jacob S. Michael a, Sera N. Dogramaci a,*, Kylie A. Steel b, Kenneth S. Graham a a b
Applied Research Program, New South Wales Institute of Sport, 6 Figtree Drive, Sydney Olympic Park, NSW 2127, Australia School of Science and Health, University of Western Sydney, Penrith Campus, Locked Bag 1797, Penrith South, NSW 1797, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 March 2013 Received in revised form 24 September 2013 Accepted 4 November 2013
Objectives: To investigate the effect of long leg compression garments on the postural sway and balance ability of female athletes at a state sports institute. Design: A laboratory was set up to analyse kinetic and kinematic variables using a double blind, randomised controlled repeated measures cross over design. Method: Participants were required to perform a single leg balance task for up to 60 s across six conditions; including eyes-open and eyes-closed while wearing conventional shorts (control), loosefitted compression garment and well-fitted compression garments. Simultaneous measurements of ground reaction forces and full body joint kinematics were recorded. Postural stability was assessed by measuring the overall stabilisation time as well as the movement of the centre of pressure (CoP) and centre of mass (CoM) from baseline measures. Results: During one leg stance, significantly greater postural stability (p < 0.01) was observed with eyes open vs eyes closed, irrespective of compression group. A significantly greater (p < 0.05) balance time was observed with eyes closed when wearing well-fitted compression garments compared to conventional shorts. Differences were not present with use of the loose-fitted garment. Additionally, a significant interaction effect between compression condition and vision was observed analysing the variation about the sway (swaySD) of the CoP and CoM data (p < 0.05). The interaction effect revealed greater variability of movement with eyes closed as participants’ level of compression decreased. No significant differences were observed with eyes open. Conclusions: The difficulties of postural stability while maintaining the single leg stance wearing conventional shorts were improved with use of the well-fitted compression garments (in the eyes-closed condition). Proper fitted compression garments may be beneficial for injury management and injury prevention. ß 2013 Elsevier B.V. All rights reserved.
Keywords: Proprioception Compression garment Motor learning Female Athlete
1. Introduction Compression based garments have been used in the medical field to optimise circulatory dynamics for many years [1,2]. Compression garments (CGs) provide a means of creating an external pressure gradient at the surface of the body [2], that demonstrates improved venous return [3] and a reduction in peripheral swelling [4]. Although a significant amount of research exists describing these positive roles of CGs within therapeutic settings, research examining sports-specific use of CGs have revealed mixed results, with only a few reporting performance benefits. Research data related to exercise and wearing CGs has demonstrated a decrease in blood lactate concentrations during
* Corresponding author. Tel.: +612 9763 0267. E-mail address: [email protected] (S.N. Dogramaci). 0966-6362/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2013.11.001
and after maximal exercise [5] and improvements in maximal aerobic performance in repeated 5 min maximal cycle efforts [6]. The results suggested that the CGs were better able to improve recovery via increasing venous return and aid in the removal of waste products. Moreover, it has been demonstrated that enhanced repetitive jump performance [7,8] and an increased vertical jump height [9] resulted with use of CGs. In addition to those mentioned above, possible mechanisms may include enhanced joint proprioception [7] and muscle coordination [10], as well as assisting muscle contraction via the reduction in muscle oscillation during jump landings [9]. Contrary to these reports however, no improvements in maximal throwing distance [1], repeat sprint performance [1,9] or prolonged running/cycling performance times [3] were gained whilst wearing CGs. Recently Pearce et al. [11] found visuomotor tracking performance improved while participants wore CGs during and after repetitive eccentric arm exercise. The CG is thought to have
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produced increased cutaneous stimulation allowing for improved proprioceptive feedback and joint positional awareness. Furthermore, Cameron et al. [12] investigated the effect of CGs on a leg swing task in Australian Rules football players and found high performing players demonstrated decreased swing discrimination score compared to less skilled players who improved. In contrast to the results found by Pearce et al. [11] the increased feedback presented to the elite players via the cutaneous sensory receptors in the skin, may have presented unfamiliar feedback that was difficult to ignore by the feedback system. Further, less skilled players may have been less attuned to their own intrinsic feedback and so profited from the novel presentation of feedback in this case. Despite the aforementioned studies there is a paucity of research in the application of CGs in motor control, e.g. balance. Balance ability in sport ranges from maintaining an upright posture to executing complex sporting skills, and is required to keep the vertical projection of the centre of mass over the base of support [13]. Constant adjustments and counter-adjustments of joint position exist (postural sway) which maintain equilibrium and prevent falling [14]. Given control of posture is maintained by a complex interrelationship between sensory information obtained from the somatosensory, visual, and vestibular systems and responses of the musculoskeletal system regulating body posture and movement [15] it is possible that these systems may benefit from the use of CGs. Further, research has shown that superior balance enhances postural control [16] athletic performance [17], and is associated with a reduction in injury rates [18]. Therefore the purpose of this study was to assess the effectiveness of wearing CGs on the balance ability of elite athletes, and to investigate the effects of compression garment sizing on postural control. We hypothesised that greater conscious awareness of the body’s position would occur as a result of wearing CGs during a 60 s single-leg balance task. 2. Methods Twelve healthy and active females (24 7.2 yrs; 57.8 6.1 kg; 168.3 6.3 cm) volunteered to participate in this study. Participants were free of neurological illness, musculoskeletal injury or any disease/condition that would interfere with their normal balance. University Human Ethics Committee (ref. H8620) was provided prior to the commencement of the study and participants gave informed consent before participating. Kinetic and kinematic variables were measured using a double blind, randomised controlled repeated measures cross over design to assess the effects CGs had on balance during single leg stance (SLS). Participants were required to perform three balance trials: wearing conventional shorts (control); loose fitted CGs (LF-CG); and well fitted CGs (WF-CG), on two occasions: eyes open and eyes closed (visual occlusion). The CGs were fitted to participants on the basis of the company’s guidelines using height and weight. LF-CG was classified as loose-fitted compared to the normal recommended size. Both pairs of CGs looked identical to minimise any placebo effects. Each testing session began with the conventional shorts condition which provided baseline measurements for balance ability. The two remaining compression garment conditions were then randomised for each subject to minimise any learning effect that may occur with familiarity. The CGs used were standard commercial sportswear (itsports, Sydney, Australia) which covered the area from the waist to the ankle with a stirrup under the foot. All participants had worn compression garments during their sporting careers; however, in this instance the athletes had not worn this brand of garment. Prior to each testing condition, instructions were given directing the participant to stand in a comfortable stance, balancing on their dominant leg (stance leg) near the centre of
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the force platform. Participants were instructed to keep their nonweight bearing leg (swing leg) in approximately 158 of flexion, so that their foot was level with, but not touching, the calf of their stance leg. Additionally, participants’ arms were kept in a flexed position, with their hands resting on their hips. Participants were allowed to move their arms and swing leg during the trial as a strategy to regain balance if required, but were instructed to return their arms and swing leg to the initial position immediately after sway was controlled. This movement was allowed to represent balance strategies used during normal balance control. Each trial began once the subject was in a ‘‘ready’’ position and gave a verbal cue to indicate she felt comfortable in a quiet, balanced stance. Similar to previous studies measuring healthy and active participants [19] the participants in the current study were required to maintain this SLS for a maximum of 60 s. If the subject became unbalanced during the trial and touched the floor with the swing leg, the test was terminated and the total time of the test was recorded. An eight camera motion analysis system (Vicon MX 13; Oxford Metrics Ltd., Oxford, United Kingdom) and one force plate (Kistler 9281CA, Winterthur, Switzerland) were used to sample the participant’s kinematic and kinetic motion data, respectively. Subjects’ 3D trajectories and 3D reaction forces were captured using a motion capture, measurement and analysis software (Vicon Motion Systems, Nexus v1.6, Oxford, United Kingdom) using the plug-in gait full body model. Raw marker trajectories were filtered using Vicon’s Woltring quintic spline algorithm with a MSE value of 20. The motion analysis software enabled synchronised recording of the three dimensional motion data with the analogue force channel simultaneously recorded during each balance trial (sampled at 250 and 500 Hz respectively). Thirty-five spherical shaped retro-reflective markers were used to define 15 rigid, linked segments of the participant (head, trunk, upper arms, forearms, hand, pelvis, thighs, shanks and feet) during each trial (Fig. 1). The 3D trajectories of the reflective markers (14 mm diameter) were computed with a dynamic accuracy of 0.5 mm [20]. Centre of mass (CoM) was determined from the anthropometric and kinematic analysis of all body segments. The position the participant applied weight onto the force platform was calculated as the centre of pressure (CoP) which was computed using the digitised output signals of the force platform amplifiers.
Fig. 1. An example of the anatomical landmark locations used in the biomechanical analysis of the participants in this study.
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Each balance trial was analysed for all participants. The main outcome measures for this study included the overall stabilisation time and measurements of CoM/CoP path lengths. Path length measurements include CoM and CoP range differences within the sagittal plane (antero-posterior axis) and the frontal plane (mediolateral axis); average sway within the CoM and CoP time series and standard deviations of this range of movement. All computations were based on the total stabilisation time acquired. The antero-posterior (AP) and medio-lateral (ML) coordinates that define the CoM and CoP path were computed using the digitised output signals of the force platform amplifiers. The participant was positioned on the force platform facing the positive AP direction. Thus the location and movements of the CoM and CoP in the AP and ML axis during SLS were recorded. The range referred to the maximum movement of the CoM and CoP, in both the AP and ML directions. Range was calculated as the maximum distance between any two points on the time series path. The CoP range in the AP direction for example, was the absolute value of the difference between the smallest and largest values in the AP time series for CoP data. Similarly, ML range was calculated. The ability to keep the CoM above the CoP is reflected in the absolute difference between the two variables in both the AP and ML directions (the CoM–CoP range difference). This measurement of path lengths has been used in previous research [21] and shown to be a valid and reliable measure of standing balance [21–23]. Furthermore, postural sway was also calculated, and defined as the average displacement spent away from the central point of origin in both the CoM and CoP coordinate time series. The origin of the CoM and CoP path was X–Y coordinate recorded at the beginning of each trial. The resultant distance was calculated as the vector distance from the CoM and CoP origin to each consecutive point on the CoM and CoP path respectively. Average postural sway, the mean of the resultant distance time series, was recorded, along with the variability (standard deviations) of the postural sway in the CoM and CoP time series. The swaySD has been successfully used as an indicator of postural sway by previous researchers [24]. All statistical procedures were conducted with SYSTAT (SYSTAT, Inc., Evanston, IL). A two-way analysis of variance (compression condition vision) with repeated measures was used to test the significance of any observed differences in the means of the primary variables and to determine any interaction effects. A probability level of p < 0.05 was accepted to indicate a statistically significant difference in the individual comparisons. Where significance was reached, a Student–Newman–Keuls post hoc analysis was used to isolate differences among conditions [10]. All data are presented as mean standard deviation (SD). 3. Results The results for the overall stabilisation time are presented in Fig. 2. A significant main effect was observed when analysing the effect of vision (F[1,11] = 21.40, p < 0.05) and compression condition (F[2,22] = 5.34, p < 0.05). A significant interaction effect was also observed between compression condition and vision for total stabilisation time (F[2,22] = 4.94, p < 0.05). Post hoc tests revealed that with eyes closed, total balance time wearing WF-GG was significantly greater than wearing shorts (Fig. 2). No significant differences among the three compression conditions were observed in the eyes open condition, with all subjects maintaining the 60 s stance balanced on one leg. Representative graphs for the maximum displacement of the CoM and CoP within the AP and ML directions are presented in Fig. 3. Analysis of the CoM and CoP range allowed for the CoM–CoP range differences. No significant main effects were observed between compression conditions when analysing the CoM and CoP
Fig. 2. Total stabilisation time (s) for each compression condition with eyes open and eyes closed with their respective SD values. *Significant difference between shorts and well fitted compression garments (p < 0.05).
range in the AP direction (F[2,22] = 1.58, p = 0.23 and F[2,22] = 0.75, p = 0.48 respectively) or ML direction (F[2,22] = 3.40, p = 0.05, and F[2,22] = 1.93, p = 0.17 respectively). Furthermore, no significant main effect was found analysing the CoM–CoP range differences in the AP (F[2,22] = 0.72, p = 0.50) and ML directions (F[2,22] = 2.57, p = 0.10). Post hoc tests showed that with vision and compression conditions grouped, a significantly greater CoP displacement was found in the AP direction compared to the ML direction (p < 0.05) (Fig. 3B). Alternatively, analysis of the CoM data revealed greater, but not significant, movement in the ML direction compared to the AP direction (p = 0.09). CoM and CoP plots for average sway and swaySD are presented in Fig. 4. A significant main effect was observed when analysing the effect of vision for all variables measured (F[1,11] = 28.27, p < 0.01; F[1,11] = 17.83, p < 0.01; F[1,11] = 19.03, p < 0.01 and F[1,11] = 17.50, p < 0.01, respectively) with greater balance control observed with eyes open compared to eyes closed. Examination of the average postural sway measured from the CoM and CoP time series indicated no significant differences between compression conditions (F[2,22] = 0.18, p = 0.84 and F[2,22] = 0.54, p = 0.59, respectively) (Fig 4A). Similarly, no significant differences were observed when analysing the CoM and CoP swaySD (F[2,22] = 1.33, p = 0.28 and F[2,22] = 1.63, p = 0.22, respectively) (Fig. 4B). A significant interaction effect was observed however, between compression condition and vision when analysing the CoM and CoP swaySD (F[2,22] = 3.92, p < 0.05 and F[2,22] = 4.03, p < 0.05 respectively). The interaction effect revealed greater variability of movement with eyes closed as participants’ level of compression decreased (Fig. 4B). 4. Discussion The aim of this study was to assess the effects of CGs compared to conventional shorts on stability during one leg stance for 60 s with eyes open and eyes closed. The assessment of stability incorporated total balance time as well as measurement of the CoM/CoP and deviations from these points. The results gathered indicate that wearing WF-CGs significantly improved balance time and significantly decreased postural sway variability compared with conventional shorts in the eyes closed condition. However, wearing LF-CGs revealed no significant differences, highlighting the importance of correct sizing control. Furthermore, CGs had no effect on static balance and postural control when vision was present. The removal of vision demonstrated a significant negative effect on balance time and postural sway, which is consistent with
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Fig. 3. Maximum range of the CoM, CoP and CoM–CoP range differences in the AP and ML directions: (A) the effect of compression condition and vision with standard deviations presented only for eyes closed, and (B) with compression condition and vision grouped, analysing the cumulative effect of AP and ML directions. *Significant difference between AP and ML directions with compression and vision grouped (p < 0.05). AP: antero-posterior; CoM: centre of mass; CoP: centre of pressure; LF-CG: loose fitted compression garment; ML: medio-lateral; WF-CG: well fitted compression garment.
previous research examining unperturbed stance. It has been suggested that vision, as well as proprioceptive (somatosensory) inputs, dominate the control of orientation and balance [25]. A number of studies have also isolated specific sensory inputs by altering either vision or the support surface, which has resulted in data that can be used as a baseline for balance assessment [16,25]. Further, the reduction of the base of support present in a one leg balance task significantly increases body sway by up to 8 times [16] compared to bipedal stance [14,25]. This suggests that the proprioceptive feedback extracted when performing a one limb task is not sufficient to overcome the effect of visual occlusion during balance and posture tasks [14]. The results of the current study support this, as vision enabled all participants to maintain balance on one leg, irrespective of compression condition, for the entire 60 s time period with minimal differences in postural movement observed. However, with visual occlusion, the control ‘‘shorts’’ condition demonstrated a significant reduction in balance time and significantly greater body movement variability compared to eyes open. Furthermore, wearing the CGs with visual occlusion resulted in a insignificant reduction in balance time, with these values found closer to those observed with eyes open. This was particularly evident when wearing WF-CG, where participants significantly improved the total time they were able to balance on one leg compared to the control condition. Data analysis of the maximum absolute CoM movement and CoP displacement in the AP and ML directions when vision was occluded indicated a concomitant, though not significant, trend. Results revealed that as surface compression increased (from
shorts to WF-CG), maximum amount of CoM and CoP movement in both the AP and ML directions decreased to values closer to those observed with eyes open (Fig. 3A and B). Although the large variability limited the significance of individual comparisons, a significant interaction effect was found between vision and compression when analysing the movement of the CoP. The results highlighted the decreased movement of the CoP with use of CGs when vision was occluded. Research examining CoM and CoP measures have found increased movement with eyes closed [24]. This was suggested to be due to greater body movements in any given direction before movement was counteracted by corrective muscle action [24]. Considering the reduced body movement found with use of CGs, it may be suggested that CG use may improve joint positional sense to accommodate for visual occlusion, and thus allowing participants to improve postural control while maintaining SLS. Similarly, following fatiguing exercise, where proprioception and sensory awareness would be expected to decline [26], Pearce et al. [11] found significantly better results when participants performed post exercise visuomotor tracking tasks when wearing CGs. This supports the current findings that the compression provided may support the active muscles in a way that decreases dependency upon the visual input [11] and enhances proprioception [27]. It can be suggested that surface compression may act on cutaneous mechanoreceptors to provide an additional sensory input, which in turn, may improve sensation, and thus lead to improved muscle coordination [9] and joint stability [11]. Recent studies have also observed improvements in the stabilisation of
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Fig. 4. Average postural sway (A) and the respective standard deviation (B) for CoP and CoM time series. *Significant interaction effect (p < 0.05). CoM: centre of mass; CoP: centre of pressure; LF-CG: loose fitted compression garment; WF-CG: well fitted compression garment.
upright posture by providing additional tactile sensory input, particularly, using ‘light touch’ of the index finger with a stationary surface [28,29]. Jeka and Lackner found that contact of the index finger with a stationary bar attenuated postural sway with vision occluded. In a similar way to the current study, the authors suggest that the pattern of somatosensory stimulation from the light touch triggers postural muscles to correct sway. The current findings of improved postural control with CGs together with those examining light touch demonstrate the potential applications for injury management/rehabilitation and injury prevention, where athletes have lost varying levels of sensorimotor processes [30]. Additional data analysis revealed positional changes recorded on the force platform were not always accompanied by corresponding movements of the CoM (Fig. 3B). Consistent with previous research, analysis of the CoP displacement indicated movement in the AP direction was significantly greater compared to the ML direction (p < 0.05) [23,24]. Interestingly however, although not significant, analysis of the CoM data revealed the opposite effect, with greater movement recorded in the ML direction compared to the AP direction (p = 0.09). To maintain a balanced posture on one leg, the postural control system allows for
movements of the body segments to keep the CoM over the base of support [23,25], which may explain this factor. Many perturbations experienced by the participants were accompanied with a counterbalancing of a body segment in the lateral direction in order to prevent falling. During SLS with eyes open all testing conditions revealed that the CoP and the vertical line of the CoM are very close to alignment, as indicated by small differences measured between these two variables (Fig. 3). A close alignment would suggest a small sway path, thus was used as an indication of good postural control. This alignment observation was recorded in both the AP and ML directions. With visual occlusion, differences between the CoM and CoP in both directions were shown to increase. This difference was reported as maximal during the SLS wearing conventional shorts, and again showed a non-significant decrease as surface compression increased. Finally, the swaySD revealed significant interaction effects (Fig. 4B). Results revealed greater variability of movement with eyes closed as participants’ level of compression decreased. The data from the WF-CG in both eyes open and eyes closed were found to lie close to the mean values recorded. These results again indicate a greater musculature control combining with the action
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of the various sensory processes to bring about the appropriate segmental adjustments to keep the CoM over the base of support. Examining the swaySD for CoP data revealed a 16% increase in variation between eyes open and eyes closed with WF-CG, compared to a 100% increase with use of conventional shorts. A similarly large difference between WF-CG and conventional shorts was found with analysis of the CoM swaySD data (25% and 146% increase respectively). Further examination of the mean CoM and CoP velocity will provide for a comprehensive balance assessment in an attempt to characterise the regulatory processes underlying postural control. 5. Conclusions Since most athletic performance is associated with various types of dynamic movements with the need for vision, the performance benefits of using CGs in a static balance trial found in the current study may be limited in its application. Considering the specific nature of certain sports, different levels of sensorimotor processes are required to perform skills and reduce the risk of injury. Therefore further research is essential to determine if wearing CGs translates into a useful application for dynamic stabilisation and injury management. Conflicts of interest The authors report no conflicts of interest that could inappropriately influence this work. The authors alone are responsible for the content and writing of the paper. Acknowledgements Grateful acknowledgement is given to the New South Wales Institute of Sport and its staff for the testing location, equipment and the supply of itsports compression garments. No financial assistance was obtained for this project. References [1] Duffield R, Portus M. Comparison of three types of full-body compression garments on throwing and repeat-sprint performance in cricket players. British Journal of Sports Medicine 2007;41:409–14. [2] MacRae BA, Cotter JD, Laing RM. Compression garments and exercise: garment considerations, physiology and performance. Sports Medicine 2011;41:815– 43. [3] Ali A, Caine MP, Snow BG. Graduated compression stockings: physiological and perceptual responses during and after exercise. Journal of Sports Sciences 2007;25:413–9. [4] Mayberry JC, Moneta GL, DeFrang RD, Porter JM. The influence of elastic compression stockings on deep venous hemodynamics. Journal of Vascular Surgery 1991;13:91–9. [5] Berry MJ, McMurray RG. Effects of graduated compression stockings on blood lactate following an exhaustive bout of exercise. American Journal of Physical Medicine 1987;66:121–32. [6] Chatard JC, Atlaoui D, Farjanel J, Louisy F, Rastel D, Guezennec CY. Elastic stockings, performance and leg pain recovery in 63-year-old sportsmen. European Journal of Applied Physiology 2004;93:347–52.
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[7] Kraemer WJ, Bush JA, Bauer JA, Triplett-McBride NT, Paxton NJ, Clemson A, et al. Influence of compression garments on vertical jump performance in NCAA division I volleyball players. Journal of Strength and Conditioning Research 1996;10:180–3. [8] Kraemer WJ, Bush JA, Newton RU, Duncan ND, Volek JS, Denegarb CR, et al. Influence of a compressive garment on repetitive power output production before and after different types of muscle fatigue. Sports Medicine Training and Rehabilitation 1998;8:163–84. [9] Doan BK, Kwon YH, Newton RU, Shim J, Popper EM, Rogers RA, et al. Evaluation of a lower-body compression garment. Journal of Sports Sciences 2003;21:601–10. [10] Bringard A, Perrey S, Belluye N. Aerobic energy cost and sensation responses during submaximal running exercise – positive effects of wearing compression tights. International Journal of Sports Medicine 2006;27:373–8. [11] Pearce AJ, Kidgell DJ, Grikepelis LA, Carlson JS. Wearing a sports compression garment on the performance of visuomotor tracking following eccentric exercise: a pilot study. Journal of Science and Medicine in Sport 2009;12:500–2. [12] Cameron ML, Adams RD, Maher CG. The effect of neoprene shorts on leg proprioception in Australian football players. Journal of Science and Medicine in Sport 2008;11:345–52. [13] Adlerton AK, Moritz U, Moe-Nilssen R. Forceplate and accelerometer measures for evaluating the effect of muscle fatigue on postural control during onelegged stance. Physiotherapy Research International 2003;8:187–99. [14] O’Connell M, George K, Stock D. Postural sway and balance testing: a comparison of normal and anterior cruciate ligament deficient knees. Gait and Posture 1998;8:136–42. [15] Winter DA, Patla AE, Frank JS. Assessment of balance control in humans. Medical Progress Through Technology 1990;16:31–51. [16] Era P, Heikkinen E. Postural sway during standing and unexpected disturbance of balance in random samples of men of different ages. The Journals of Gerontology 1985;40:287–95. [17] Myer GD, Ford KR, Brent JL, Hewett TE. The effects of plyometric vs. dynamic stabilization and balance training on power, balance, and landing force in female athletes. Journal of Strength and Conditioning Research 2006;20:345– 53. [18] Irrgang J, Whitney J, Cox E. Balance and proprioceptive training for rehabilitation of the lower extremity. Journal of Sport Rehabilitation 1994;3:68–83. [19] Santos BR, Delisle A, Lariviere C, Plamondon A, Imbeau D. Reliability of centre of pressure summary measures of postural steadiness in healthy young adults. Gait and Posture 2008;27:408–15. [20] Richards JG. The measurement of human motion: a comparison of commercially available systems. Human Movement Science 1999;18:589–602. [21] Clark RA, Bryant AL, Pua Y, McCrory P, Bennell K, Hunt M. Validity and reliability of the Nintendo Wii balance board for assessment of standing balance. Gait and Posture 2010;31:307–10. [22] Murray MP, Seireg A, Scholz RC. Center of gravity, center of pressure, and supportive forces during human activities. Journal of Applied Physiology 1967;23:831–8. [23] Prieto TE, Myklebust JB, Hoffmann RG, Lovett EG, Myklebust BM. Measures of postural steadiness: differences between healthy young and elderly adults. IEEE Transactions on Biomedical Engineering 1996;43:956–66. [24] Goldie PA, Bach TM, Evans OM. Force platform measures for evaluating postural control: reliability and validity. Archives of Physical Medicine and Rehabilitation 1989;70:510–7. [25] Berg K. Balance and its measure in the elderly: a review. Physiotherapy Canada 1989;41:240–6. [26] Saxton JM, Clarkson PM, James R, Miles M, Westerfer M, Clark S, et al. Neuromuscular dysfunction following eccentric exercise. Medicine and Science in Sports and Exercise 1995;27:1185–93. [27] Feuerbach JW, Grabiner MD, Koh TJ, Weiker GG. Effect of an ankle orthosis and ankle ligament anesthesia on ankle joint proprioception. American Journal of Sports Medicine 1994;22:223–9. [28] Krishnamoorthy V, Slijper H, Latash ML. Effects of different types of light touch on postural sway. Experimental Brain Research 2002;147:71–9. [29] Jeka JJ, Lackner JRJ. Fingertip contact influences human postural control. Experimental Brain Research 1994;100:495–502. [30] Freeman MA, Dean MR, Hanham IW. The etiology and prevention of functional instability of the foot. The Journal of Bone & Joint Surgery British Volume 1965;47:678–85.
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
What is the effect of compression garments on a balance task in female athletes? Jacob S. Michael a, Sera N. Dogramaci a,*, Kylie A. Steel b, Kenneth S. Graham a a b
Applied Research Program, New South Wales Institute of Sport, 6 Figtree Drive, Sydney Olympic Park, NSW 2127, Australia School of Science and Health, University of Western Sydney, Penrith Campus, Locked Bag 1797, Penrith South, NSW 1797, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 March 2013 Received in revised form 24 September 2013 Accepted 4 November 2013
Objectives: To investigate the effect of long leg compression garments on the postural sway and balance ability of female athletes at a state sports institute. Design: A laboratory was set up to analyse kinetic and kinematic variables using a double blind, randomised controlled repeated measures cross over design. Method: Participants were required to perform a single leg balance task for up to 60 s across six conditions; including eyes-open and eyes-closed while wearing conventional shorts (control), loosefitted compression garment and well-fitted compression garments. Simultaneous measurements of ground reaction forces and full body joint kinematics were recorded. Postural stability was assessed by measuring the overall stabilisation time as well as the movement of the centre of pressure (CoP) and centre of mass (CoM) from baseline measures. Results: During one leg stance, significantly greater postural stability (p < 0.01) was observed with eyes open vs eyes closed, irrespective of compression group. A significantly greater (p < 0.05) balance time was observed with eyes closed when wearing well-fitted compression garments compared to conventional shorts. Differences were not present with use of the loose-fitted garment. Additionally, a significant interaction effect between compression condition and vision was observed analysing the variation about the sway (swaySD) of the CoP and CoM data (p < 0.05). The interaction effect revealed greater variability of movement with eyes closed as participants’ level of compression decreased. No significant differences were observed with eyes open. Conclusions: The difficulties of postural stability while maintaining the single leg stance wearing conventional shorts were improved with use of the well-fitted compression garments (in the eyes-closed condition). Proper fitted compression garments may be beneficial for injury management and injury prevention. ß 2013 Elsevier B.V. All rights reserved.
Keywords: Proprioception Compression garment Motor learning Female Athlete
1. Introduction Compression based garments have been used in the medical field to optimise circulatory dynamics for many years [1,2]. Compression garments (CGs) provide a means of creating an external pressure gradient at the surface of the body [2], that demonstrates improved venous return [3] and a reduction in peripheral swelling [4]. Although a significant amount of research exists describing these positive roles of CGs within therapeutic settings, research examining sports-specific use of CGs have revealed mixed results, with only a few reporting performance benefits. Research data related to exercise and wearing CGs has demonstrated a decrease in blood lactate concentrations during
* Corresponding author. Tel.: +612 9763 0267. E-mail address: [email protected] (S.N. Dogramaci). 0966-6362/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2013.11.001
and after maximal exercise [5] and improvements in maximal aerobic performance in repeated 5 min maximal cycle efforts [6]. The results suggested that the CGs were better able to improve recovery via increasing venous return and aid in the removal of waste products. Moreover, it has been demonstrated that enhanced repetitive jump performance [7,8] and an increased vertical jump height [9] resulted with use of CGs. In addition to those mentioned above, possible mechanisms may include enhanced joint proprioception [7] and muscle coordination [10], as well as assisting muscle contraction via the reduction in muscle oscillation during jump landings [9]. Contrary to these reports however, no improvements in maximal throwing distance [1], repeat sprint performance [1,9] or prolonged running/cycling performance times [3] were gained whilst wearing CGs. Recently Pearce et al. [11] found visuomotor tracking performance improved while participants wore CGs during and after repetitive eccentric arm exercise. The CG is thought to have
J.S. Michael et al. / Gait & Posture 39 (2014) 804–809
produced increased cutaneous stimulation allowing for improved proprioceptive feedback and joint positional awareness. Furthermore, Cameron et al. [12] investigated the effect of CGs on a leg swing task in Australian Rules football players and found high performing players demonstrated decreased swing discrimination score compared to less skilled players who improved. In contrast to the results found by Pearce et al. [11] the increased feedback presented to the elite players via the cutaneous sensory receptors in the skin, may have presented unfamiliar feedback that was difficult to ignore by the feedback system. Further, less skilled players may have been less attuned to their own intrinsic feedback and so profited from the novel presentation of feedback in this case. Despite the aforementioned studies there is a paucity of research in the application of CGs in motor control, e.g. balance. Balance ability in sport ranges from maintaining an upright posture to executing complex sporting skills, and is required to keep the vertical projection of the centre of mass over the base of support [13]. Constant adjustments and counter-adjustments of joint position exist (postural sway) which maintain equilibrium and prevent falling [14]. Given control of posture is maintained by a complex interrelationship between sensory information obtained from the somatosensory, visual, and vestibular systems and responses of the musculoskeletal system regulating body posture and movement [15] it is possible that these systems may benefit from the use of CGs. Further, research has shown that superior balance enhances postural control [16] athletic performance [17], and is associated with a reduction in injury rates [18]. Therefore the purpose of this study was to assess the effectiveness of wearing CGs on the balance ability of elite athletes, and to investigate the effects of compression garment sizing on postural control. We hypothesised that greater conscious awareness of the body’s position would occur as a result of wearing CGs during a 60 s single-leg balance task. 2. Methods Twelve healthy and active females (24 7.2 yrs; 57.8 6.1 kg; 168.3 6.3 cm) volunteered to participate in this study. Participants were free of neurological illness, musculoskeletal injury or any disease/condition that would interfere with their normal balance. University Human Ethics Committee (ref. H8620) was provided prior to the commencement of the study and participants gave informed consent before participating. Kinetic and kinematic variables were measured using a double blind, randomised controlled repeated measures cross over design to assess the effects CGs had on balance during single leg stance (SLS). Participants were required to perform three balance trials: wearing conventional shorts (control); loose fitted CGs (LF-CG); and well fitted CGs (WF-CG), on two occasions: eyes open and eyes closed (visual occlusion). The CGs were fitted to participants on the basis of the company’s guidelines using height and weight. LF-CG was classified as loose-fitted compared to the normal recommended size. Both pairs of CGs looked identical to minimise any placebo effects. Each testing session began with the conventional shorts condition which provided baseline measurements for balance ability. The two remaining compression garment conditions were then randomised for each subject to minimise any learning effect that may occur with familiarity. The CGs used were standard commercial sportswear (itsports, Sydney, Australia) which covered the area from the waist to the ankle with a stirrup under the foot. All participants had worn compression garments during their sporting careers; however, in this instance the athletes had not worn this brand of garment. Prior to each testing condition, instructions were given directing the participant to stand in a comfortable stance, balancing on their dominant leg (stance leg) near the centre of
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the force platform. Participants were instructed to keep their nonweight bearing leg (swing leg) in approximately 158 of flexion, so that their foot was level with, but not touching, the calf of their stance leg. Additionally, participants’ arms were kept in a flexed position, with their hands resting on their hips. Participants were allowed to move their arms and swing leg during the trial as a strategy to regain balance if required, but were instructed to return their arms and swing leg to the initial position immediately after sway was controlled. This movement was allowed to represent balance strategies used during normal balance control. Each trial began once the subject was in a ‘‘ready’’ position and gave a verbal cue to indicate she felt comfortable in a quiet, balanced stance. Similar to previous studies measuring healthy and active participants [19] the participants in the current study were required to maintain this SLS for a maximum of 60 s. If the subject became unbalanced during the trial and touched the floor with the swing leg, the test was terminated and the total time of the test was recorded. An eight camera motion analysis system (Vicon MX 13; Oxford Metrics Ltd., Oxford, United Kingdom) and one force plate (Kistler 9281CA, Winterthur, Switzerland) were used to sample the participant’s kinematic and kinetic motion data, respectively. Subjects’ 3D trajectories and 3D reaction forces were captured using a motion capture, measurement and analysis software (Vicon Motion Systems, Nexus v1.6, Oxford, United Kingdom) using the plug-in gait full body model. Raw marker trajectories were filtered using Vicon’s Woltring quintic spline algorithm with a MSE value of 20. The motion analysis software enabled synchronised recording of the three dimensional motion data with the analogue force channel simultaneously recorded during each balance trial (sampled at 250 and 500 Hz respectively). Thirty-five spherical shaped retro-reflective markers were used to define 15 rigid, linked segments of the participant (head, trunk, upper arms, forearms, hand, pelvis, thighs, shanks and feet) during each trial (Fig. 1). The 3D trajectories of the reflective markers (14 mm diameter) were computed with a dynamic accuracy of 0.5 mm [20]. Centre of mass (CoM) was determined from the anthropometric and kinematic analysis of all body segments. The position the participant applied weight onto the force platform was calculated as the centre of pressure (CoP) which was computed using the digitised output signals of the force platform amplifiers.
Fig. 1. An example of the anatomical landmark locations used in the biomechanical analysis of the participants in this study.
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Each balance trial was analysed for all participants. The main outcome measures for this study included the overall stabilisation time and measurements of CoM/CoP path lengths. Path length measurements include CoM and CoP range differences within the sagittal plane (antero-posterior axis) and the frontal plane (mediolateral axis); average sway within the CoM and CoP time series and standard deviations of this range of movement. All computations were based on the total stabilisation time acquired. The antero-posterior (AP) and medio-lateral (ML) coordinates that define the CoM and CoP path were computed using the digitised output signals of the force platform amplifiers. The participant was positioned on the force platform facing the positive AP direction. Thus the location and movements of the CoM and CoP in the AP and ML axis during SLS were recorded. The range referred to the maximum movement of the CoM and CoP, in both the AP and ML directions. Range was calculated as the maximum distance between any two points on the time series path. The CoP range in the AP direction for example, was the absolute value of the difference between the smallest and largest values in the AP time series for CoP data. Similarly, ML range was calculated. The ability to keep the CoM above the CoP is reflected in the absolute difference between the two variables in both the AP and ML directions (the CoM–CoP range difference). This measurement of path lengths has been used in previous research [21] and shown to be a valid and reliable measure of standing balance [21–23]. Furthermore, postural sway was also calculated, and defined as the average displacement spent away from the central point of origin in both the CoM and CoP coordinate time series. The origin of the CoM and CoP path was X–Y coordinate recorded at the beginning of each trial. The resultant distance was calculated as the vector distance from the CoM and CoP origin to each consecutive point on the CoM and CoP path respectively. Average postural sway, the mean of the resultant distance time series, was recorded, along with the variability (standard deviations) of the postural sway in the CoM and CoP time series. The swaySD has been successfully used as an indicator of postural sway by previous researchers [24]. All statistical procedures were conducted with SYSTAT (SYSTAT, Inc., Evanston, IL). A two-way analysis of variance (compression condition vision) with repeated measures was used to test the significance of any observed differences in the means of the primary variables and to determine any interaction effects. A probability level of p < 0.05 was accepted to indicate a statistically significant difference in the individual comparisons. Where significance was reached, a Student–Newman–Keuls post hoc analysis was used to isolate differences among conditions [10]. All data are presented as mean standard deviation (SD). 3. Results The results for the overall stabilisation time are presented in Fig. 2. A significant main effect was observed when analysing the effect of vision (F[1,11] = 21.40, p < 0.05) and compression condition (F[2,22] = 5.34, p < 0.05). A significant interaction effect was also observed between compression condition and vision for total stabilisation time (F[2,22] = 4.94, p < 0.05). Post hoc tests revealed that with eyes closed, total balance time wearing WF-GG was significantly greater than wearing shorts (Fig. 2). No significant differences among the three compression conditions were observed in the eyes open condition, with all subjects maintaining the 60 s stance balanced on one leg. Representative graphs for the maximum displacement of the CoM and CoP within the AP and ML directions are presented in Fig. 3. Analysis of the CoM and CoP range allowed for the CoM–CoP range differences. No significant main effects were observed between compression conditions when analysing the CoM and CoP
Fig. 2. Total stabilisation time (s) for each compression condition with eyes open and eyes closed with their respective SD values. *Significant difference between shorts and well fitted compression garments (p < 0.05).
range in the AP direction (F[2,22] = 1.58, p = 0.23 and F[2,22] = 0.75, p = 0.48 respectively) or ML direction (F[2,22] = 3.40, p = 0.05, and F[2,22] = 1.93, p = 0.17 respectively). Furthermore, no significant main effect was found analysing the CoM–CoP range differences in the AP (F[2,22] = 0.72, p = 0.50) and ML directions (F[2,22] = 2.57, p = 0.10). Post hoc tests showed that with vision and compression conditions grouped, a significantly greater CoP displacement was found in the AP direction compared to the ML direction (p < 0.05) (Fig. 3B). Alternatively, analysis of the CoM data revealed greater, but not significant, movement in the ML direction compared to the AP direction (p = 0.09). CoM and CoP plots for average sway and swaySD are presented in Fig. 4. A significant main effect was observed when analysing the effect of vision for all variables measured (F[1,11] = 28.27, p < 0.01; F[1,11] = 17.83, p < 0.01; F[1,11] = 19.03, p < 0.01 and F[1,11] = 17.50, p < 0.01, respectively) with greater balance control observed with eyes open compared to eyes closed. Examination of the average postural sway measured from the CoM and CoP time series indicated no significant differences between compression conditions (F[2,22] = 0.18, p = 0.84 and F[2,22] = 0.54, p = 0.59, respectively) (Fig 4A). Similarly, no significant differences were observed when analysing the CoM and CoP swaySD (F[2,22] = 1.33, p = 0.28 and F[2,22] = 1.63, p = 0.22, respectively) (Fig. 4B). A significant interaction effect was observed however, between compression condition and vision when analysing the CoM and CoP swaySD (F[2,22] = 3.92, p < 0.05 and F[2,22] = 4.03, p < 0.05 respectively). The interaction effect revealed greater variability of movement with eyes closed as participants’ level of compression decreased (Fig. 4B). 4. Discussion The aim of this study was to assess the effects of CGs compared to conventional shorts on stability during one leg stance for 60 s with eyes open and eyes closed. The assessment of stability incorporated total balance time as well as measurement of the CoM/CoP and deviations from these points. The results gathered indicate that wearing WF-CGs significantly improved balance time and significantly decreased postural sway variability compared with conventional shorts in the eyes closed condition. However, wearing LF-CGs revealed no significant differences, highlighting the importance of correct sizing control. Furthermore, CGs had no effect on static balance and postural control when vision was present. The removal of vision demonstrated a significant negative effect on balance time and postural sway, which is consistent with
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Fig. 3. Maximum range of the CoM, CoP and CoM–CoP range differences in the AP and ML directions: (A) the effect of compression condition and vision with standard deviations presented only for eyes closed, and (B) with compression condition and vision grouped, analysing the cumulative effect of AP and ML directions. *Significant difference between AP and ML directions with compression and vision grouped (p < 0.05). AP: antero-posterior; CoM: centre of mass; CoP: centre of pressure; LF-CG: loose fitted compression garment; ML: medio-lateral; WF-CG: well fitted compression garment.
previous research examining unperturbed stance. It has been suggested that vision, as well as proprioceptive (somatosensory) inputs, dominate the control of orientation and balance [25]. A number of studies have also isolated specific sensory inputs by altering either vision or the support surface, which has resulted in data that can be used as a baseline for balance assessment [16,25]. Further, the reduction of the base of support present in a one leg balance task significantly increases body sway by up to 8 times [16] compared to bipedal stance [14,25]. This suggests that the proprioceptive feedback extracted when performing a one limb task is not sufficient to overcome the effect of visual occlusion during balance and posture tasks [14]. The results of the current study support this, as vision enabled all participants to maintain balance on one leg, irrespective of compression condition, for the entire 60 s time period with minimal differences in postural movement observed. However, with visual occlusion, the control ‘‘shorts’’ condition demonstrated a significant reduction in balance time and significantly greater body movement variability compared to eyes open. Furthermore, wearing the CGs with visual occlusion resulted in a insignificant reduction in balance time, with these values found closer to those observed with eyes open. This was particularly evident when wearing WF-CG, where participants significantly improved the total time they were able to balance on one leg compared to the control condition. Data analysis of the maximum absolute CoM movement and CoP displacement in the AP and ML directions when vision was occluded indicated a concomitant, though not significant, trend. Results revealed that as surface compression increased (from
shorts to WF-CG), maximum amount of CoM and CoP movement in both the AP and ML directions decreased to values closer to those observed with eyes open (Fig. 3A and B). Although the large variability limited the significance of individual comparisons, a significant interaction effect was found between vision and compression when analysing the movement of the CoP. The results highlighted the decreased movement of the CoP with use of CGs when vision was occluded. Research examining CoM and CoP measures have found increased movement with eyes closed [24]. This was suggested to be due to greater body movements in any given direction before movement was counteracted by corrective muscle action [24]. Considering the reduced body movement found with use of CGs, it may be suggested that CG use may improve joint positional sense to accommodate for visual occlusion, and thus allowing participants to improve postural control while maintaining SLS. Similarly, following fatiguing exercise, where proprioception and sensory awareness would be expected to decline [26], Pearce et al. [11] found significantly better results when participants performed post exercise visuomotor tracking tasks when wearing CGs. This supports the current findings that the compression provided may support the active muscles in a way that decreases dependency upon the visual input [11] and enhances proprioception [27]. It can be suggested that surface compression may act on cutaneous mechanoreceptors to provide an additional sensory input, which in turn, may improve sensation, and thus lead to improved muscle coordination [9] and joint stability [11]. Recent studies have also observed improvements in the stabilisation of
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Fig. 4. Average postural sway (A) and the respective standard deviation (B) for CoP and CoM time series. *Significant interaction effect (p < 0.05). CoM: centre of mass; CoP: centre of pressure; LF-CG: loose fitted compression garment; WF-CG: well fitted compression garment.
upright posture by providing additional tactile sensory input, particularly, using ‘light touch’ of the index finger with a stationary surface [28,29]. Jeka and Lackner found that contact of the index finger with a stationary bar attenuated postural sway with vision occluded. In a similar way to the current study, the authors suggest that the pattern of somatosensory stimulation from the light touch triggers postural muscles to correct sway. The current findings of improved postural control with CGs together with those examining light touch demonstrate the potential applications for injury management/rehabilitation and injury prevention, where athletes have lost varying levels of sensorimotor processes [30]. Additional data analysis revealed positional changes recorded on the force platform were not always accompanied by corresponding movements of the CoM (Fig. 3B). Consistent with previous research, analysis of the CoP displacement indicated movement in the AP direction was significantly greater compared to the ML direction (p < 0.05) [23,24]. Interestingly however, although not significant, analysis of the CoM data revealed the opposite effect, with greater movement recorded in the ML direction compared to the AP direction (p = 0.09). To maintain a balanced posture on one leg, the postural control system allows for
movements of the body segments to keep the CoM over the base of support [23,25], which may explain this factor. Many perturbations experienced by the participants were accompanied with a counterbalancing of a body segment in the lateral direction in order to prevent falling. During SLS with eyes open all testing conditions revealed that the CoP and the vertical line of the CoM are very close to alignment, as indicated by small differences measured between these two variables (Fig. 3). A close alignment would suggest a small sway path, thus was used as an indication of good postural control. This alignment observation was recorded in both the AP and ML directions. With visual occlusion, differences between the CoM and CoP in both directions were shown to increase. This difference was reported as maximal during the SLS wearing conventional shorts, and again showed a non-significant decrease as surface compression increased. Finally, the swaySD revealed significant interaction effects (Fig. 4B). Results revealed greater variability of movement with eyes closed as participants’ level of compression decreased. The data from the WF-CG in both eyes open and eyes closed were found to lie close to the mean values recorded. These results again indicate a greater musculature control combining with the action
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of the various sensory processes to bring about the appropriate segmental adjustments to keep the CoM over the base of support. Examining the swaySD for CoP data revealed a 16% increase in variation between eyes open and eyes closed with WF-CG, compared to a 100% increase with use of conventional shorts. A similarly large difference between WF-CG and conventional shorts was found with analysis of the CoM swaySD data (25% and 146% increase respectively). Further examination of the mean CoM and CoP velocity will provide for a comprehensive balance assessment in an attempt to characterise the regulatory processes underlying postural control. 5. Conclusions Since most athletic performance is associated with various types of dynamic movements with the need for vision, the performance benefits of using CGs in a static balance trial found in the current study may be limited in its application. Considering the specific nature of certain sports, different levels of sensorimotor processes are required to perform skills and reduce the risk of injury. Therefore further research is essential to determine if wearing CGs translates into a useful application for dynamic stabilisation and injury management. Conflicts of interest The authors report no conflicts of interest that could inappropriately influence this work. The authors alone are responsible for the content and writing of the paper. Acknowledgements Grateful acknowledgement is given to the New South Wales Institute of Sport and its staff for the testing location, equipment and the supply of itsports compression garments. No financial assistance was obtained for this project. References [1] Duffield R, Portus M. Comparison of three types of full-body compression garments on throwing and repeat-sprint performance in cricket players. British Journal of Sports Medicine 2007;41:409–14. [2] MacRae BA, Cotter JD, Laing RM. Compression garments and exercise: garment considerations, physiology and performance. Sports Medicine 2011;41:815– 43. [3] Ali A, Caine MP, Snow BG. Graduated compression stockings: physiological and perceptual responses during and after exercise. Journal of Sports Sciences 2007;25:413–9. [4] Mayberry JC, Moneta GL, DeFrang RD, Porter JM. The influence of elastic compression stockings on deep venous hemodynamics. Journal of Vascular Surgery 1991;13:91–9. [5] Berry MJ, McMurray RG. Effects of graduated compression stockings on blood lactate following an exhaustive bout of exercise. American Journal of Physical Medicine 1987;66:121–32. [6] Chatard JC, Atlaoui D, Farjanel J, Louisy F, Rastel D, Guezennec CY. Elastic stockings, performance and leg pain recovery in 63-year-old sportsmen. European Journal of Applied Physiology 2004;93:347–52.
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