Long lasting periods in quiet stance, thanks to the

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1 2092-J.SM./Original articles. J SPORTS MED PHYS FITNESS 2006;46:00-00 Effects of compression tights on calf muscle oxygenation and venous pooling during quiet resting in supine and standing positions Aim. We applied near-infrared spectroscopy (NIRS) to evaluate in resting conditions the effects of compression tights (CT) on calf muscle oxygenation and venous pooling compared with Lycra elastic tights (ET) and shorts (no compression) according to the body posture (supine vs standing). Methods. Twelve sportsmen regularly involved in endurance training volunteered to this study. Their average age, height and weight (±SD) were 26.5±2.6 years, 177±6 cm and 70.1±4 kg, respectively. Tissue oxygenation index (TOI), deoxyhemoglobin (HHb), and blood pooling (Hbtot) of the right gastrocnemius medialis were continuously monitored at 2 Hz using a NIRS device (NIRO-300, Hamamatsu Photonics, Japan). A home made transducer was used to measure applied pressure at the interface between skin and clothing over the calf area. Subjects were asked to realize a supine-standing protocol (5 min for each position) by wearing CT, ET or shorts in a counterbalanced order on the same day. Results. HHb and Hbtot concentration changes were significantly lower whereas TOI was significantly higher by wearing CT compared with shorts and ET (P<0.001) as did supine compared to upright postures. The mean pressures applied over the calf were 5.6 and 23.2 mmhg during supine and 5 and 24.1 mmhg during standing for ET and CT, respectively. Pressures were significantly different among clothing according to the following rank order: CT>ET>shorts (P<0.001). Conclusion. CT compared to ET have positive effects on calf This study was supported by Decathlon, Inc. Received November 2, Accepted for publication February 9, Address reprint requests to: S. Perrey, PhD, EA 2991 Motor Efficiency and Deficiency Lab, 700 Avenue Du Pic Saint Loup, Montpellier, France. stephane.perrey@univ-montp1.fr A. BRINGARD 1, 2, R. DENIS 1, N. BELLUYE 2, S. PERREY 2 muscle oxygenation and venous pooling in quiet resting positions. KEY WORDS: Muscle oxygenation - Tights - External pressure - Recovery. Long lasting periods in quiet stance, thanks to the effects of the orthostatic stress are known to increase lower limbs volume and affect venous function, increasing in turn leg swelling. The use of compression stockings is a well-established therapy, which can have positive effects on leg swelling in both patients and healthy subjects. Wearing compression stockings decreased significantly leg swelling that occurs after a working day spent sitting or standing upright. 1 Numerous studies demonstrated that an external pressure (ranging from (10 to 30 mmhg at the ankle) applied by compression stockings induced venous return and/or blood flow increases in healthy subjects and patients with chronic venous insufficiency (CVI). 2-5 A better venous return due to the use of compression stockings can increase in turn the cardiac output. 6 Note that studies aiming for a better understanding of compression stockings effects have been mainly conducted on lower limbs oxygenation among CVI 1Motor Efficiency and Deficiency Lab (EA 2991) Faculty of Sports Science, University of Montpellier I Montpellier, France 2Decathlon Test and Research Center, France Vol No. THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 1

2 BRINGARD EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION patients. 5 Altogether, the above cited studies provided insights about the use and utility of compression stockings in patients and even in healthy subjects. Regarding the case of sportsmen, it is now rather common to see them wearing compression or elastic tights (ET) especially during recovery period after a strenuous physical exercise inducing deleterious effects on muscle function. However, to our knowledge, no research has been conducted investigating the effects of compression and ET on lower limbs muscle oxygenation among active subjects regularly involved in aerobic sports. Running is a typical endurance activity that causes several muscle fatigue-related symptoms (e.g. metabolic acidosis, delayed onset muscle soreness, leg cramps, and weakness). To avoid a possible negative effect of a long lasting recovery time between workouts in physical training, it would be interesting to know in a first time the influence of compression and ET on muscle oxygenation and blood volume during resting conditions. According to some authors, the aerobic training-related increase in venous compliance would predispose athletes to varicose veins. 7 Whatever the population considered, sportsmen exhibiting a high venous compliance or patients with CVI, standing upright compared to lying supine may predispose further to increase leg swelling. Applying a sufficient external pressure on lower limb muscles may counteract these issues and finally relieve muscle fatigue-related symptoms at rest. Compression tights (CT) could decrease venous stasis while improving muscle oxygenation, allowing in turn to delay varicose veins occurrence in runners. The pressure exerted by ET used by sportsmen may be insufficient to increase venous return compared to CT. 8 We can wonder at first what changes are occurring regarding muscle oxygenation parameters and venous pooling in runners, when wearing different tights (elastic vs compression) in sportsmen during two resting positions (upright vs supine). Ergogenic properties of CT have been mentioned by Berry et al. s studies but have never been estimated in terms of muscle oxygenation and venous function. 8, 9 Surprisingly, it is still unknown whether such tights compromise or improve muscle oxygenation of the lower limbs at rest. We were therefore interested to look at the effects of compression and ET on muscle oxygenation at rest (i.e. without muscle contraction). Results of this study could highlight about possible benefits of wearing compression and ET at rest. This issue may be important in the management of the recovery after fatiguing physical activity in sportsmen. Therefore, the purpose of this study was to compare muscle oxygenation responses to different clothing conditions (CT, ET and no CT) during two body posture positions at rest in runners. We hypothesized that CT would decrease blood volume and enhance muscle oxygen saturation compared to ET and with no CT or shorts. The hemodynamics changes associated with gravitational factors (supine vs upright) would contribute also to influence differently blood volume and muscle oxygenation as a function of the clothing conditions. In this work, we used near-infrared spectroscopy (NIRS), a non-invasive technique to investigate calf venous function and oxygen saturation. Previous studies defined this technique as accurate and able to provide reproducible measurements. 5, 10, 11 Materials and methods Subjects Twelve sportsmen regularly involved in aerobicoriented training (more than 3 workouts a week since at least 3 years) participated to this study. Their average age, height and weight (±SD) were 26.5±2.6 years, 177±6 cm and 70.1±4 kg, respectively. We chose sportsmen with a great experience in running due to the important solicitation of the calves muscles in this activity. The study protocol complied with the Helsinki declaration for human experimentation and was approved by the local human ethics committee. Possible risks and benefits were explained and written informed consent was obtained from each subject prior all testing. No one suffered from severe muscle soreness, knee injury, or known peripheral vascular disorder, besides the subject number 11 who had a mild internal saphenous varicose vein on the right calf. For this subject, measurements were therefore carried out on the left side. Test protocol For all conditions, all subjects rested in a quiet room with constant temperature (~22 C) to eliminate possible environmental influences on leg volume. 12 They were evaluated on a single session (no fatigue effect) in a counterbalanced order under the following three conditions: custom-made CT (Decathlon ), commer- 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS Mese 2006

3 EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION BRINGARD cially ET (Lycra ), no compression (shorts). For the latter control condition, subjects wore their own shorts. The CT were made by a commercial manufacturer specialized in that field to deliver an appropriate compression profile (pressure gradient of ~20 mmhg at the calf). CT were not washed before testing since this was likely to alter the requisite compression profile. The size of all tights was based on measurements of the volunteer s legs made previously to allow for proper fitting. Before measurements for any experimental clothing conditions, subjects lay supine for 5 min in the control condition. This condition allowed us to get individual baseline values, without compression effects over the leg. Then, 3 postures of 5 min duration each were investigated for each clothing condition. After a second set of 5 min spent lying supine, subjects were asked to sit down with the knees flexed at 90 for 5 further min, then to stand up and finally to stay upright for 5 last min. Under each condition, they were asked to stay as quiet as possible in order to avoid any movements, particularly calf muscle contractions. Transitions between postures had to be as smooth as possible. In all cases 5 min was of sufficient duration to observe a steady state level during the last minute between each transition. During each transition, assistance was given when subjects had to change clothing, in order to minimize leg movements and muscle contractions. At last, to avoid any blood pooling (Hbtot) due to a prolonged period spent in quiet stance, subjects were asked to lay supine for few minutes between each condition. Muscle oxygenation measurements Muscle oxygenation was assessed using the NIRS technique. The NIRS signal provides continuous, noninvasive monitoring of the relative concentration changes in oxyhemoglobin (HbO 2 ) and deoxyhemoglobin (HHb). 11, 13 Total hemoglobin concentration changes (Hbtot) are the sum of HHb and HbO 2 concentrations and give an index of the blood volume. 11 Because of the overlap of the spectrum, it is however not possible to distinguish between changes in hemoglobin (Hb) and myoglobin (Mb). However, in human skeletal muscle, the ratio of Hb to Mb concentration is >5 so the signal is usually considered as deriving mainly from Hb. 13 In the present study, only changes in muscle oxygenation of the right gastrocnemius medialis (GM) were continuously monitored at 2 Hz using a near infrared spatially resolved spectroscopy oximeter (NIRO-300, Hamamatsu Photonics, Japan). 14 GM muscle was chosen due to its great involvement in running. Data were simultaneously transmitted to a personal computer using a RS-232C wire. NIRO-300 optodes were housed in an optically dense plastic holder, ensuring that their position relative to each other was fixed and invariant. The probe (i.e. the optodes support) was secured on the cleaned skin surface with tape. The probe was placed over the GM muscle belly (excepted for the subject who suffered from varicose vein on the right limb), parallel to the major axis of the shin. The position of the probe on the calf muscle was marked carefully. The detector in the NIRS probe was separated from the light source by 40 mm. The light emitted by the near infrared probe is assumed to depth tissues at 50% of the interoptode spacing (space between emitting and receiving probe).15 Skinfold thickness was measured between the NIRS optodes using a skinfold caliper (Holtain Ltd., Crymmych, UK), and was divided by 2 to determine the adipose tissue thickness (i.e. fat + skin layer) covering the muscle. The obtained values of adipose tissue thickness were 2.8±0.9 mm, allowing the NIRS photons to penetrate through the muscle. 15 The absorption of light at different wavelengths (775, 810, 850 and 910 nm) was analysed according to the modified Beer-Lambert s law. Because the differential path length factor (DPF) reported in the literature is estimation from a particular group of subjects, and hence just represents a mean value for that group, no DPF was utilized in the present study. Changes in HbO 2, HHb and Hbtot concentration were reported as a change from baseline values in micromolar units per centimeter (µm.cm). The HHb signal can be regarded as being essentially blood-volume insensitive during exercise, thus it was assumed to be a reliable estimator of changes in intramuscular oxygenation status and O 2 extraction in the field of interrogation. 16, 17 Moreover, the NIRO-300 provides directly tissue hemoglobin oxygen saturation [tissue oxygenation index, TOI=HbO 2 /(HbO 2 +HHb) 100, expressed in percentage] calculated independently by using the spatially resolved spectroscopy method which exploits the source detector multidistance approach. 14, 17 Pressure measurements Before realizing the supine-sitting-standing protocol, the pressure exerted by clothing was measured at the interface between skin and clothing over the posterior part of the calf muscle, where the circumfer- Vol No. THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 3

4 BRINGARD EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION Applied pressure (mmhg) Shorts ET CT Figure 1. Mean values (±SD, n=12) of pressure (in mmhg) applied by the different clothing (CT: compression tights; ET: elastic tights; shorts). The pressure with shorts is zero. +P<0.001, significantly different from shorts. P<0.001, significantly different from CT. ence was the greatest (37.1±1 cm). While subjects were staying in quiet stance, an investigator was setting the pressure transducer whether underneath the tights or over the skin, according to the experimental conditions. In this study, a home made pressure transducer connected to an acquisition A/D system (MP-30, Biopac Inc., USA) and a personal computer was used to record the pressure under the tights for s at 500 Hz; by this time the investigator was checking the curve displayed on the computer screen to ensure that the pressure was constant and subjects motionless. The pressure was then averaged for 3-5 s using the Biopac Student Lab software (Acqknowledge, BSL Pro 3.6.7, USA). Data analysis The NIRS data (HHb, HbO 2,Hb tot and TOI) were averaged over the last minute of each 5 min quiet period set. This was done for each position and condition of clothing (9 conditions per subject). When the knee was 90 flexed, we observed a drastic rise in pressure values. Therefore we decided to not report sitting conditions in the present study due to abnormally high pressure profile generated by other factors than the different tights and positions tested. Haemoglobin concentration changes (mm cm) or saturation (%) HbO 2 HHb Hb tot Statistical analysis A two-way analysis of variance (ANOVA) for repeated measurements was used to test for differences in the NIRS and pressure parameters, with posture (lying supine vs standing upright) and clothing (CT, ET, shorts) as the within-subject factors. Any differences were further analysed with a Student- Newman-Keuls posthoc test. A two-way ANOVA on ranks was systematically performed if data distribution fails the normality or equal variance tests. All values are presented as mean(sd. Statistical significance was accepted at P<0.05. Results The mean pressures applied over the calf were 5.6 and 23.2 mmhg during quiet supine and 5 and 24.1 mmhg during quiet standing for ET and CT, respectively. The analysis revealed a significant effect of clothing on pressure. Mean values of pressure were significantly different among clothing according to the following rank order: CT>ET> shorts (P<0.001, Figure 1). The Figure 2 shows the changes concentration of the four parameters assessed by NIRS for the different clothing conditions. There was a significant effect of CT compared with ET and shorts conditions. Indeed, the increase of HHb and Hb tot was significantly lower [F(2, 11)=32.2 and F(2, 11)=13.1, respectively] while TOI was significantly higher [F(2, 11)=18.9] CT Shorts ET TOI Figure 2. The effect of the clothing (CT: compression tights; ET: elastic tights; shorts) on mean values ((SD, n=12) of HHb, HbO 2,Hb tot and TOI. Since HHb, HbO 2 and Hb tot represent concentration changes, they are expressed in µm.cm. TOI is expressed in percentage. P<0.001, significantly different from CT. 4 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS Mese 2006

5 EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION BRINGARD Haemoglobin concentration changes (mm cm) or saturation (%) HbO 2 HHb Hb tot Supine by wearing CT compared with shorts and ET (P<0.001). There was no significant difference in the decrease of HbO 2 among clothing conditions. The mean results for HHb, HbO 2,Hb tot and TOI during quiet standing upright and lying supine conditions are represented in Figure 3. The analysis revealed a significant effect of the body posture on NIRS parameters. Values of HHb and Hb tot concentration changes were significantly higher during standing compared with supine [F(1, 11)=178.3, P<0.001 and F(1, 11)=102.5, P<0.001, respectively]. Conversely, HbO 2 concentration changes and TOI values were significantly lower during standing compared with supine [F(1, 11)=24.5, P<0.001 and F(1, 11)=144.6, P<0.001, respectively]. There was no significant interaction between clothing and position, except for HbO 2 [F(1, 2)=7.7, P<0.05]; HbO 2 significantly decreased in standing compared to supine with ET and shorts (P<0.001), but not with CT (P=0.3). Discussion Standing TOI Figure 3. The effect of the body posture (standing vs supine) on mean values ((SD, n=12) of HHb, HbO 2, Hbtot and TOI. Since HHb, HbO 2 and Hbtot represent concentration changes, they are expressed in µm.cm. TOI is expressed in percentage. P<0.001, significantly different from standing. Although a variety of compression and especially ET are available for sportsmen for practicing purpose, these tights are considered by many to be beneficial for recovery treatment and related exercise symptom relief, but this is based only on some empiric evidence. The main goal of the present study was to assess whether CT compared to ET and shorts were effective in improving muscle oxygenation and lowering venous pooling (or stasis) in a representative group of trained endurancesubjects during two resting positions (standing vs upright). Our findings showed a significantly lower venous pooling (smaller Hbtot changes) and a higher calf oxygen saturation level with CT in comparison to ET and shorts in both positions tested. Increased muscle oxygenation in the area investigated was discernable by both a significant decrease in HHb and an increase in TOI. Similar results were observed when subjects were lying supine compared to upright standing whatever the clothing conditions considered; Hbtot decreased significantly in supine position. External pressure over the calf muscle applied by CT was 23.6±4.8 mmhg that is about 4.5 fold higher than ET. In the present study, wearing CT was associated with a significantly smaller calf Hbtot concentration change compared to ET and short controls (about mean values of -48%, Figure 2). This finding suggests that CT fulfilled well some of its ergogenic effects by countering venous pooling especially in upright standing but also in lying supine position. The use of compression stockings leading to a venous return enhancement has been showed to increase cardiac output. 6 In our study, it appears that, due to the external pressure applied by CT on the calf muscle, the blood was likely to leave from the lower limbs to the heart. Compared to ET, the physiological mechanisms by which CT achieve the desired positive effects may reflect the inherent differences in tights manufactory design to exert a sufficient pressure to lower venous pooling. Independently of clothing, we observed logically also a significant increase in Hbtot during upright standing compared to supine position (Figure 3). 18 The erect posture is known to be associated with distal venous pooling owing to gravity. This result confirms in part previous studies conducted about the effect of long lasting upright position on leg swelling and leg blood volume rises. 1, 2 We also observed for both positions, a significant increase in muscle oxygenation (higher TOI and lower HHb, Figure 2) when subjects were wearing CT compared with ET and shorts. Several possible mechanisms may explain the apparent improvement in muscle oxygenation: improved blood flow in the capillary bed and therefore increased oxygen by volume; increased perfusion and better utilization of oxygen Vol No. THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 5

6 BRINGARD EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION within the muscle; changes in skin blood flow. In supine position muscle oxygenation was also significantly improved compared to upright standing (Figure 3). This can be mainly explained by a better venous return due to the higher cardiac output and stroke volume observed in this position. 6 The significant improvement in muscle oxygenation could be in favor of a shortened fatigue muscle recovery rate and an improvement of lactic acid consumption, as muscle deoxygenation induced by exhaustive endurance event while exercising is known to be highly related to lactate concentration. 9, 19 During postexercise recovery, due to the inflammatory processes in active muscles, delayed onset muscle soreness causes discomfort and can lengthen the recovery period. A recent study showed that the magnitude of creatine kinase elevation was depressed by wearing compression sleeves after an eccentric exercise in comparison with a control group (i.e. without compression sleeves); elbow swelling was also reduced. Wearing CT could have the same positive benefits for lower limbs. 20 In the context of the present study we found only an interaction effect for HbO 2. Conversely to ET and shorts, CT wearing induced similar values in HbO 2 between standing and supine positions. Based on the present findings relating to some CT effects (improved calf muscle oxygenation and lower venous pooling), distal venous pooling owing to gravity may be counteracted with efficacy with the help of CT by keeping constant local tissue oxygenation. It is important to note that we observed in upright position, a tendency of a decrease in Hbtot for CT by 20% and by 15% compared to shorts and ET respectively, but statistical significance failed (P<0.1). This lack of any significant effect could be attributed to the low pressure ((5 mmhg, personal data) that CT were applying on the ankles. Regarding to the law of Laplace 21 and some of our personal unpublished data, a higher pressure applied at the ankle level could have differently influenced Hbtot concentration in upright position, since graduated compression stockings have been proved to improve tissue oxygenation and reduce venous pooling. 5 Whereas CT have been shown to improve venous hemodynamics, the pressure profile applied on the legs must be taken into account. 22 Positive compression effects among pathological limbs can be deleterious when applied on healthy legs. When pressure applied on the calf approaches 30 mmhg it may lead to a progressive fall in subcutaneous flow. 23 Measurements were performed where the circumference was the greatest for the shank (see Materials and methods ). Significantly higher pressure (Figure 1) was found with CT compared to ET. These differences indicate that the increase in local pressure could have a beneficial effect on venous blood return. Applying a positive pressure (up to mmhg) on the legs is a widely used therapy which prevent from CVI. However, among healthy subjects such pressure is obviously not needed during recovery. 23 During exercise, venous muscle pump efficacy of the healthy human leg is enhanced by a greater rate of muscle activation. In our study, subjects were at rest. Thus the only parameter which could affect muscle oxygenation and venous Hbtot was probably the change in local external pressure, exhibited by CT. Furthermore, we tested sportsmen who are likely to have an increased compliance of the leg venous network due to their aerobic training. 7 In this work, the decrease in Hbtot may be due to a drop in venous compliance when wearing CT. Conclusions To conclude, the major finding of this study was a significant increase in muscle oxygenation only with CT in both resting upright and supine positions, associated with a significant decrease in Hb tot. It appears that CT compared to ET have positive effects on muscle oxygenation and venous function at rest, and could be useful to oxygenate fatigued muscles after exercise. This work also provided further information about the pressure, which should be applied over the calf in healthy subjects, trying to respect the well established physiological balance of the human body and prevent from any disturbance regarding homeostasis. All findings based on the effects of compression after 5 min of application deserve further studies to determine the long-term effects of CT with prolonged use and during recovery after strenuous exercise. Acknowledgements. We wish to acknowledge Dr. Jean-Paul Micaleff (mechanical engineering, INSERM) for his technical assistance regarding the use and development of the pressure transducer. References 1. Partsch H, Winiger J, Lun B. Compression stockings reduce occupational leg swelling. Dermatol Surg 2004;30: Jonker MJ, de Boer EM, Adère HJ, Bezemer PD. The oedema pro- 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS Mese 2006

7 EFFECTS OF COMPRESSION OF THE LOWER LIMBS AND MUSCLE OXYGENATION BRINGARD tective effect of Lycra support stockings. Dermatology 2001;203: Brown JR, Brown AM. Nonprescription, padded, lightweight support socks in treatment of mild to moderate lower extremity venous insufficiency. J Am Osteopath Assoc 1995;95: Ibegbuna V, Delis K, Nicolaides N. Effect of lightweight compression stockings on venous haemodynamics. Int Angiol 1997;16: Agu O, Baker D, Seifalian AM. Effect of graduated compression stockings on limb oxygenation and venous function during exercise in patients with venous insufficiency. Vascular 2004;12: Watanuki S, Murata H. Effects of wearing compression stockings on cardiovascular responses. Ann Physiol Anthrop 1994;13: Donaldson MC. Varicose veins in active people. Physician Sports Med 1990;18:7. 8. Berry MJ, Bailey SP, Simpkins SL, TeWinkle JA. The effects of elastic tights on the post-exercise response. Can J Sport Sci 1990;15: Berry MJ, McMurray RG. Effects of graduated compression stockings on blood lactate following an exhaustive bout of exercise. Am J Phys Med 1987;66: Sako T, Hamaoka T, Higuchi H, Kurosawa Y, Katsumura, T. Validity of NIR spectroscopy for quantitatively measuring muscle oxidative metabolic rate in exercise J Appl Physiol 2001;90: Quaresima V, Lepanto R, Ferrari M. The use of near infrared spectroscopy in sports medicine J Sports Med Phys Fitness 2003;43: Stick C, Hiedl U, Witzleb E. Volume changes in the lower leg during quiet standing and cycling exercise at different ambient temperatures. Eur J Appl Physiol 1993;66: Mancini D. Application of near infrared spectroscopy to the evaluation of exercise performance and limitations in patients with heart failure. J Biomed Optics 1997;2: Suzuki S, Takasaki S, Ozaki T, Kobayashi Y. A tissue oxygenation monitor using NIR spatially resolved spectroscopy. Proc SPIE 1999;3597: Matsushita K, Homma S, Okada E. Influence of adipose tissue on muscle oxygenation measurement with NIRS instrument. Proc SPIE 1998;3194: Ferrari M, Binzoni T, Quaresima V. Oxidative metabolism in muscle. Phil Trans R Soc Lond B Biol Sci 1997;352: Delpy DT, Cope M. Quantification in tissue near-infrared spectroscopy. Phil Trans R Soc Lond B Biol Sci 1997;352: Binzoni T, Quaresima V, Ferrari M, Hiltbrand E, Cerretelli P. Human calf microvascular compliance measured by near-infrared spectroscopy. J Appl Physiol 2000;88: Rundell KW, Nioka S, Chance B. Haemoglobin/myoglobin desaturation during speed skating. Med Sci Sport Exerc 1997;27: Kraemer WJ, Bush JA, Wickham RB, Denegar CR, Gomez AL, Gotshalk LA et al. Influence of compression therapy on symptoms following soft tissue injury from maximal eccentric exercise. J Orthop Sports Phys Ther 2001;31: Basford JR. The law of Laplace and its relevance to contemporary medicine and rehabilitation. Arch Phys Med Rehabil 2002;83: Lawrence D, Kakkar VV. Graduated, static, external compression of the lower limb: a physiological assessment. Br J Surg 1980;67: Kügler C, Strunk M, Rudofsky G. Venous pressure dynamics of the healthy human leg. J Vasc Res 2001;38:20-9. Vol No. THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 7