Yonago Acta medica 2013;56:79–80

Short Communication

Effects of Water Temperature during Foot Bath in Young Females
Masahiro Nishimura,* Tatsuya Saito,† Toshiaki Kato* and Sho Onodera‡*Division of Medical Science in Sports and Exercise, Department of Social Medicine, School of Medicine, Tottori University Facultyof Medicine, Tottori 680-8550, Japan, †Doctoral Program in Health Science, Graduate School of Health Science and Technology,Kawasaki University of Medical Welfare, Kurashiki 701-0193, Japan and ‡Department of Health and Sports Science, Faculty of Health
Science and Technology, Kawasaki University of Medical Welfare, Kurashiki 701-0193, JapanABSTRACTWe examined the effects of environmental and watertemperatures of foot baths on pulse rate, blood pressure,mean skin temperature, salivary amylase (SA) activity,relaxation level and thermal sensation during winter.
Five females participated in the study. The subjects
rested in a chair for 20 min and the above-noted physiological reactions during the last 5 min of the resting period were recorded as baseline (BASE) values. Next, thesubjects received a 15-min foot bath in water at 40 ˚C(WT40) or 45 ˚C (WT45), with a 15-min recovery period. Although SA is thought to be an indicator of stress
via the sympathetic nervous system, we did not find acorrelation between SA activity and relaxation state. We
considered the possible effect of seasonal variation on
the physiological reaction to foot bathing.

(WT45), with a 15-min recovery period. Pulse rate,
blood pressure and skin temperature were measured bydigital electronic sphygmomanometer ES-P110 (Terumo,Tokyo, Japan) at the end of BASE recording and at 5, 10
and 15 min of the foot immersion and recovery periods.
Skin temperatures were obtained from the chest,arm and thigh using thermistor thermometer NT Logger
N542R and thermistor probe ITP082-25 (NIKKISOTHERM, Tokyo), and mean levels were calculated.1 SA
activity was measured by Salivary Amylase Monitor(NIPRO, Osaka, Japan) at each end of BASE recording,foot immersion and recovery periods. SA activity is used
as an indicator of stress via the sympathetic nervous
system.2, 3 The relaxation level and thermal sensation ofthe whole body and foot were similarly measured on anumerical rating scale. Foot baths under each condition(WT40 and WT45) were performed between 1100 hoursand 1300 hours on different days, but always at the sametime. The room temperature was maintained at 20 ˚C.
All data were presented as mean and standard deviation. A two-way analysis of variance with repeatedmeasures was used to test for a physiological difference
between water temperatures. Tukey’s post-hoc test wasused to test significant differences. The subjective scale
was assessed by the Friedman and Wilcoxon signed
rank tests. The data were analyzed using the PASW
Statistics software for Windows ver. 18.0 (IBM, Tokyo,Japan). The significance level was set at P < 0.05.

Key words

foot; immersion; salivary alpha amylase;seasonal variation; thermosensing
Foot immersion is particularly effective for inducing relaxation and sleep. We hypothesized effects of environmental and water temperatures and seasonal variation on
the physiological reaction to foot bathing, and examinedthe effects of both temperatures of foot baths on pulse
rate, blood pressure, mean skin temperature, salivary
amylase (SA) activity, relaxation level and thermal sensation during the winter.

RESULTS AND DISCUSSION
Compared to the BASE values, the pulse rate and systolic and diastolic blood pressures did not change undereither bathing condition. Foot immersion probably puts
a less severe load than usual bathing does on the circulatory system, and it induces hyperthermia.4
The main effect of time was significant for the mean
skin temperature (P < 0.05). Mean skin temperature was

SUBJECTS AND METHODSFive female subjects participated in the study (age, 20.5
years, s = 1.0; height, 157.2 cm, s = 9.3; body weight,
53.9 kg, s = 6.5; body fat, 26.9%, s = 1.8). This study wasapproved by the Ethics Committee of Tottori University(approval number 2074).
All subjects wore T-shirts and shorts during theexperiment. The room temperature was maintained at20 ˚C. The subjects each rested in a chair for 20 min;pulse rate, blood pressure, mean skin temperature, SA
activity, relaxation state and thermal sensation during
the last 5 min of the resting period were recorded asbaseline (BASE) values. Next, the subjects received
a 15-min foot bath in water at 40 ˚C (WT40) or 45 ˚CCorresponding author: Masahiro Nishimura, PhDmnishimura@med.tottori-u.ac.jp
Received 2013 June 26
Accepted 2013 July 5
Abbreviations: BASE, baseline recorded during the last 5 min of
the 20-min resting period; SA, salivary amylase; WT40, 15-minfoot bath in 40 ˚C water; WT45, 15-min foot bath in 45 ˚C water79

M. Nishimura et al.

Fig. 1. Changes in an indicator of stress and relaxation.
a: Changes in SA activity under conditions of WT40 ( ) and WT45 ( ). The main effect of water temperature was marginally significant
for SA activity (P = 0.057).
b: Changes in relaxation level under conditions of WT40 ( ) and WT45 ( ). Compared to the BASE values, the relaxation level underboth conditions increased significantly during the foot immersion and recovery periods. *P < 0.05 versus BASE.
BASE, baseline recorded during the last 5 min of the 20-min resting period; Immersion15, measurement at the end of a 15-min foot immersion period; Recovery15, measurement at the end of a 15-min recovery period; SA, salivary amylase; WT40, 15-min foot bath in40 ˚C water; WT45, 15-min foot bath in 45 ˚C water.

affected by the heat stimulation of the foot bath underboth temperature conditions.
The main effect of water temperature was not significant for SA activity (P = 0.057) (Fig. 1a). We considered the possibility that cardiac vagal modulation
was enhanced under the WT45 condition. We did note a
different result when the experiment was performed insummer.5
Compared to the BASE values, the relaxation level(Fig. 1b) and thermal sensation of the whole body andfoot under both conditions increased significantly during the foot immersion and recovery periods in thisstudy (P < 0.05). There were no significant differences
between the foot bath and the recovery period. However, thermal sensation decreased during the recovery
period in comparison to the foot bath period, when weperformed the experiment under the same conditions
in summer.5 We hypothesized the difference between
mean skin temperature and foot temperature during therest period influenced thermal sensation. In addition, we
considered the possible effect of seasonal variation on
physiological reactions to foot bathing.
Although SA is thought to be an indicator of stress
via the sympathetic nervous system,2, 3 we did not finda correlation between SA activity and relaxation level.
These data suggest the need to investigate the validity ofusing SA activity, determined by a simple assay, for local stimulation. Therefore, SA activity with simple assay
may not be an appropriate biological marker of stress.
Under the tested conditions, a relaxing effect wasprovided at an environmental temperature around 20 ˚C

and water temperatures of 40 ˚C and 45 ˚C in winter.
We considered the possible effect of body temperatureduring rest, and seasonal variation on the physiologicalreaction to foot bathing.
Acknowledgments: This work was supported by JSPS Grant-inAid for Young Scientists (B) 22792144.
The authors declare no conflict of interest.
REFERENCES
1 Roberts MF, Wenger CB, Stolwijk JA, Nadel ER. Skin bloodflow and sweating changes following exercise training andheat acclimation. J Appl Physiol. 1977;43:133-7. PMID:893254.
2 Speirs RL, Herring J, Cooper WD, Hardy CC, Hind CR. The
influence of sympathetic activity and isoprenaline on the secretion of amylase from the human parotid gland. Arch OralBiol. 1974;19:747-52. PMID: 4533726.
3 Yamaguchi M, Hanawa N, Yoshida H. Evaluation of a novel
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amylase activity. Seitai Ikogaku. 2007;45:161-8. Japanese withEnglish abstract.
4 Nishimura M, Onodera S. [Relaxative effects of supine floating on heart rate, blood pressure and cardiac autonomic nervous system activity]. Uchu Koku Kankyo Igaku. 2000;37:4956. Japanese. PMID: 12715823.
5 Nishimurara M, Kato T, Onodera S. Effects of water temperature and environmental temperature during foot bath.
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