Effects of Skin Pressure Applied by Cuffs on Resting Salivary Secretion

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1 Effects of Skin Pressure Applied by Cuffs on Resting Salivary Secretion Journal of PHYSIOLOGICAL ANTHROPOLOGY and Applied Human Science Kaori Okura #, Tomoko Midorikawa-Tsurutani and Hiromi Tokura Department of Environmental Health, Nara Women s University, Abstract The effects of pressure applied by cuffs to the abdomen, thighs and legs on resting salivary flow rate and digestive function of saliva were investigated in 9 healthy female students, aged 18 to 33 yrs (Experiment I) in a climatic chamber (T a: 28 C, RH: 50%). Each participant changed from street clothing into loose-fitting experimental garments so as to avoid any skin pressure on the body, and sat calmly in a reclining chair throughout the experimental period (195 min). After 90 min (FREE period), the physiological effects of skin pressure applied by their own clothing disappeared, and skin pressure was applied for the next 60 min to the abdomen (40 mmhg) and thighs (40 mmhg) then to the legs (60 mmhg) by the use of air-inflated cuffs (PRESSURE period). During the next 45 min, the skin pressure was again removed by letting the air of the cuffs out (FREE period). The resting salivary flow rate was significantly suppressed while the skin pressure was applied by the cuffs. The digestive time for starch investigated in terms of the iodine starch reaction was longer with the skin pressure than without. The concentration of amylase measured in 20 female participants aged 21 to 23 yrs, decreased with skin pressure applied by the usage of the rubber tape (Experiment II). These results suggest that the pressure applied to the body can influence the digestive response by decreasing the amount of saliva via the autonomic nervous system. (J Physiol Anthropol 19 (2): , 2000) Keywords: clothing pressure, salivary flow rate, digestive time, amylase, autonomic nervous system Introduction It has been widely recognized that skin pressure on specific areas of the body could cause a decrease in the sweating rate (Takagi, 1972). Ogawa et al. (1979) # Present: Human Science Research Center, Wacoal Co., Ltd. demonstrated that skin pressure of up to 5 kg/50 cm 2 may exert a sweat-inhibiting effect. Murata and Tokura (1988) observed that skin pressure due to swimsuits having a clothing pressure of 20, 25 and 60 g/cm 2 had inhibitory effects on sweating. Tokura et al. (1983) found that there were some inhibitory effects on the weight loss due to the circumferential skin pressure around the waist and torso, resulting from wearing a skirt which was 4 cm shorter than the actual girth. Furthermore, some effects of skin pressure on the central processing activity have been studied. Sugimoto et al. (1990) indicated that the urinary excretion of norepinephrine increased when wearing a girdle regardless of the type of girdle or its intensity of compression. Ohtsuki et al. (1993) observed that voluntary reaction time to light stimulation was longer with skin pressure caused by compressive sportswear than without pressure, and Zhang and Tokura (1995) showed that the duration of the endurance performance in handgrip exercises was shorter when skin pressure was applied by a cuff than without skin pressure. Also, Tokura (1989) disclosed that skin pressure due to bodysuit could reduce the secretion of saliva from the parotid gland. Based upon these results, we could guess that the skin pressure has indirect as well as direct effects physically through the autonomic process. We investigated whether the skin pressure may have some effects not only on the secretion of saliva, but also on digestive response. Methods Experiment I Nine healthy females, aged 18 to 33 yrs served as participants. They had standard physical characteristics: height ± 7.1 cm and weight 51.2 ± 9.2 kg. The purpose of this study and the experimental procedures were explained to the participants before voluntary consent was obtained. Individuals were asked to eat nothing for at least one hour before the commencement of the experiment. In a climatic chamber (28 C, 50%RH), the participant changed from her street clothing into loose-fitting

2 108 Clothing Pressure and Salivary Secretion experimental garments (one-piece with short sleeves and panties) which had nearly no skin pressure to the body. Then, the participant sat in a reclining seat calmly throughout the experimental period for 195 min, which included a state having nearly no skin pressure for the first 90 min, a state having skin pressure of 40 mmhg applied to the abdomen and thighs and 60 mmhg to the legs for the next 60 min by the use of inflatable cuffs and then a state having nearly no skin pressure after releasing the air from the cuffs for the last 45 min. The cuffs used in this experiment were 25 cm wide and 120 cm long for the abdomen, 25 cm wide and 90 cm long for the thighs and 15 cm wide and 50 cm long for the legs. Resting salivary secretion was measured every 15 min. The collection started 55 min after the beginning of the experiment and was performed a total of 10 times (Fig. 1). Throughout each 5 min period, the participant was asked not to swallow saliva but to spit it out into a beaker whose weight had been measured. The resting salivary secretion was obtained by subtracting the weight of the beaker from that containing saliva. We also investigated the digestive time of starch in terms of iodine-starch reaction. After the saliva weight was measured, the saliva (1 ml) was blended with 1% solution of starch (10 ml) in another beaker, which was kept at 37 C (oral temperature) in a constant-temperature water bath. Then, the solution of saliva-starch (1 ml) was put on a glass slide every minute using a pipet, and 100 µl of iodine was dropped on it. The iodine-starch reaction test was repeated until the starch was completely digested. If the reaction color was blue, it meant that the starch was not yet digested by the saliva. If the reaction color remained yellow, it meant that the starch had been digested completely by the saliva. We took photographs of each reaction and determined the digestive time from the pictures. Experiment II The participants were twenty healthy females, aged 21 to 23 yrs. In this experiment, all participants served simultaneously. The skin pressure was circumferentially applied at the same time in the areas around the bust and waist with 1 cm wide elastic waistbands fastened with pins. The lengths of the waistbands were 15 cm shorter than the circumferences of the bust and waist, respectively. The skin pressure by the waistbands is presumed to be far lower than that by the cuffs in Experiment I, because the waistbands are 1 cm wide and commonly used as those of Fig. 1 Time schedule. In Experiment I, skin pressure was applied for the period from 90 min to 150 min. The darkshaded blocks represent the times of saliva collection during the experimental period. F60 denotes the time of saliva collection for 5 min from 55 to 60 and so on, and P15 denotes the time of saliva collection from 10 to 15 min of the skin pressure by cuffs, and so on. F 15 denotes the time of saliva collection from 10 to 15 min, and so on after the skin was released. In Experiment II, skin pressure was given by elastic waistbands. The dark-shaded blocks represent the times of saliva collection during the experimental period.

3 Okura, K et al. 109 conventional shorts. After sitting calmly for 90 min without skin pressure due to clothing, the skin pressure was applied for 30 min using the waistbands and then the bands were released for the next 30 min. The saliva which was obtained at 90 min of the control period (F90), at 30 min of the skin pressure period (P30) and at 30 min of the recovery (F 30) was placed immediately in a freezer for storage. The concentration of amylase in the saliva was then analyzed (Heckle et al., 1984). The data were analyzed statistically using the student t-test for paired data. P value less than 0.05 was accepted as significant. Results Fig. 2 Average resting salivary secretion per 5 min with (darker shades) and without skin pressure (lighter shades). Mean ± SEM. N=9. Conventions as Fig. 1. Experiment I Fig. 2 shows distinctly that resting salivary secretion was clearly inhibited by skin pressure applied by the cuffs (p<0.05). After the pressure was removed, it increased gradually. The values at F 30 and F 45 were significantly higher than those at P60 (p<0.05 and, p<0.01, respectively). Fig. 3 shows a typical example of digestive time in a participant under the influence of skin pressure. The blue colors were observed more frequently during the skin pressure period (P15, P30, P45, P60). As there were great individual differences, the average digestive time during skin pressure was represented in a relative value in Fig. 4. Fig. 3 Typical example of digestive time during the periods of control, skin pressure and recovery in a participant.

4 110 Clothing Pressure and Salivary Secretion Fig. 5 Average concentration of resting salivary amylase with and without skin pressure. Mean ± SEM. N=20. Conventions as Fig. 1. Fig. 4 Relative change of average digestive time with and without skin pressure due to the cuffs during the skin pressure period (top) and the recovery period (bottom). The values were expressed as percent of those F90 and P60, respectively. Mean ± SEM. N=8. Conventions as Fig. 1. The digestive time was significantly delayed at P30 and P60 (p<0.05), compared with that at F90 (top of the figure). The digestive time became gradually shorter during the recovery period (P<0.05 at F 45 compared with that at P60) (bottom of the figure). Experiment II Fig. 5 shows the average concentration of salivary amylase (mean ± SEM). It was significantly lower during the skin pressure period, ( ± IU/1) than during the control period ( ± IU/l) (p<0.01), and did not recover to the previous value during the recovery period ( ± IU/1) (p<0.05). Discussion Salivary glands are well supplied with autonomic nerves. The various effector cells of the salivary glands have a dual innervation. However, antagonism between the sympathetic and parasympathetic nerves does not exist with salivary secretion (Emmelin, 1979). Secretion can be activated by both sympathetic and parasympathetic nervous activity. The saliva induced by the stimulation of parasympathetic nerve is serous, and that induced by the sympathetic nerve has a high viscosity (Emmelin, 1979). The saliva collected in our present experiment was a serous fluid, called resting saliva, which contains many digestive enzymes. In our present experiments, the resting salivary secretion was decreased by skin pressure. As to hemihidrosis, sweat-inhibitory responses to skin pressure were reflexly induced in the supraspinal or spinal level by afferent nervous signals activated by skin pressure stimulation (Takagi, 1972; Ogawa et al., 1979; Tadaki et al., 1981). Moreover, Ohtsuki et al. (1993) suggested that the pressure applied to the whole body by sportswear reduced the speed of information processing in the central nervous system. With these in mind, we presumed that the results in our presents experiments were also induced by skin pressure through the afferent nerves to the medulla oblongata playing a central role in salivary secretion (Emmelin, 1979). In other words, it is likely that the decrease in the resting salivary secretion by skin pressure was an outgrowth of the autonomic nervous activity being influenced by skin pressure. The digestive time in the pressure periods was about twice as long as that in the control periods. The secretory cells of resting saliva are usually filled with secretary granules, and amylase is secreted from these granules (Kawamura et al., 1974). The decrease in salivary secretion by skin pressure might originate from a decrease of blood flow through the secretory cell. If the blood volume through the secretary cells might decrease, the secretion of amylase would also decrease, resulting in lower concentration of amylase. When salivary secretion decreases, the concentration of CI in the saliva may decrease (Kawamura et al., 1974) and the salivary CI concentration is positively correlated with the activity of

5 Okura, K et al. 111 Fig. 6 Diagrammatical summary of considerations. amylase (Kawamura et al., 1974). With these facts in consideration, the decrease of CI concentration is responsible for the lower level of amylase activity. These considerations mentioned above were diagrammatically summarized in Fig. 6. It is concluded that the salivary secretion rate was depressed by skin pressure due to clothing under the influence of the autonomic nervous system. However, it remains to be studied how autonomic nervous system and its reflex pathway are involved for inhibitory influence of skin pressure by clothing on salivary secretion. References Emmelin N (1979) Interactions between sympathetic and parasympathetic nerves in control of the salivary glands. In Brooks McC, Koizumi K. and Sato A, eds. Integrative Functions of the Automatic Nervous System. Tokyo, Tokyo University Press, 5-23 Heckle E, Morich S, Henkel R (1984) 2-Chloro-4- nitrophenyl-β-d-maltoheptaoside; A new substrate for the determination of α-amylase in serum and urine. J Clin Chem Clin Biochem 22: Kawamura Y (1974) Digestion. In Yoshii N, Iwama Y, Nakama I, eds. The present physiology. Osaka, Nagaishoten Press, (in Japanese) Maruta N, Tokura H (1988) Effects of skin pressure by swimsuit on local sweat rate, respiratory frequency, heart rate and clothing feeling in sedentary women at an ambient temperature of 35 C. J Home Econ Jpn 39: Ogawa T, Asayama M, Ito M (1979) Significance of skin pressure in body heat balance. Jpn J Physiol 29: Ohno S, Yoshida K, Iizuka S, Kuji R, Taya T (1989) Clothing hygiene and mechanism. Asakurashoten, Tokyo, 125 (in Japanese) Ohtsuki T, Kim HE, Tokura H (1993) Effects of pressure applied to the body by sportswear upon voluntary reaction time. Descent Sports Science 14: (in Japanese with English summary) Sugimoto H (1991) Compression of body by clothing. Increase in urinary norepinephrine excretion caused by foundation garments Jpn J Hyg 46: Tadaki E, Kumazawa T, Mizumura K, Takagi K (1981) Hemihidrosis due to skin pressure with particular remarks on the intensity and area of the pressure stimuli. Jpn J Physiol 31: Takagi K (1972) Functional control of living systems. In Takagi K, eds. Chuo-koronsha, Tokyo, 2-33 (in Japanese) Tokura H (1989) Physiological significance of clothing and human health. In Tokura H, eds. Proceedings of International Symposium of Clothing Comfort Studies in Mt. Fuji. The Japan Research Association for Textile End-Uses Publishing, Osaka, Tokura H, Komatsu Y, Tamura N (1983) Effects of skin pressure applied by clothing upon sweating rates in sedentary women. J Home Econ Jpn 34: Zhang P, Tokura H (1995) Effects of skin pressure by cuffs on endurance performance and voluntary reaction time. Jpn J Cloth Res 38: 7-11 Received: July 13, 1999 Accepted: January 28, 2000 Correspondence to: Hiromi Tokura, Department of Environmental Health, Nara Women s University, Nara , Japan tokura@cc.nara-wu.ac.jp