Effects of Water Temperature during Foot Bath in Young Females (2025)

Abstract

We examined the effects of environmental and water temperatures of foot baths on pulse rate,blood pressure, mean skin temperature, salivary amylase (SA) activity, relaxation level and thermalsensation during winter. Five females participated in the study. The subjects rested in a chairfor 20 min and the above-noted physiological reactions during the last 5 min of the resting periodwere recorded as baseline (BASE) values. Next, the subjects received a 15-min foot bath in water at40 °C (WT40) or 45 °C (WT45), with a 15-min recovery period. Although SA is thought to bean indicator of stress via the sympathetic nervous system, we did not find a correlationbetween SA activity and relaxation state. We considered the possible effect of seasonal variationon the physiological reaction to foot bathing.

SUBJECTS AND METHODS

Five 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 was approved by the Ethics Committee ofTottori University (approval number 2074).

All subjects wore T-shirts and shorts during the experiment. The room temperature was maintainedat 20 °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 minof the resting period were recorded as baseline (BASE) values. Next, the subjects receiveda 15-min foot bath in water at 40 °C (WT40) or 45 °C (WT45), with a 15-min recovery period.Pulse rate, blood pressure and skin temperature were measured by digital electronic sphygmomanometerES-P110 (Terumo, Tokyo, Japan) at the end of BASE recording and at 5, 10 and 15 min ofthe foot immersion and recovery periods.

Skin temperatures were obtained from the chest, arm and thigh using thermistor thermometer NT LoggerN542R and thermistor probe ITP082-25 (NIKKISO-THERM, 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 activityis used as an indicator of stress via the sympathetic nervous system.2, 3 The relaxation level andthermal sensation of the whole body and foot were similarly measured on a numerical rating scale.Foot baths under each condition (WT40 and WT45) were performed between 1100 hours and 1300 hourson different days, but always at the same time. The room temperature was maintained at 20 °C.

All data were presented as mean and standard deviation. A two-way analysis of variance withrepeated measures was used to test for a physiological difference between water temperatures.Tukey’s post-hoc test was used to test significant differences. The subjective scale was assessedby the Friedman and Wilcoxon signed rank tests. The data were analyzed using the PASW Statisticssoftware for Windows ver. 18.0 (IBM, Tokyo, Japan). The significance level was setat P < 0.05.

RESULTS AND DISCUSSION

Compared to the BASE values, the pulse rate and systolic and diastolic blood pressures did notchange under either bathing condition. Foot immersion probably puts a less severe load thanusual bathing does on the circulatory system, and it induceshyperthermia.4

The main effect of time was significant for the mean skin temperature (P < 0.05).Mean skin temperature was affected by the heat stimulation of the foot bath under both temperatureconditions.

The main effect of water temperature was not significant for SA activity (P= 0.057) (Fig. 1a). We considered the possibilitythat cardiac vagal modulation was enhanced under the WT45 condition. We did note a different resultwhen the experiment was performed in summer.5

Compared to the BASE values, the relaxation level (Fig. 1b)and thermal sensation of the whole body and foot under both conditions increased significantlyduring the foot immersion and recovery periods in this study (P < 0.05). Therewere no significant differences between the foot bath and the recovery period. However, thermalsensation decreased during the recovery period in comparison to the foot bath period,when we performed the experiment under the same conditions in summer.5 We hypothesized the difference between mean skin temperature and foot temperatureduring the rest period influenced thermal sensation. In addition, we considered the possible effectof seasonal variation on physiological reactions to foot bathing.

Although SA is thought to be an indicator of stress via the sympathetic nervous system,2, 3we did not find a correlation between SA activity and relaxation level. These data suggest the needto investigate the validity of using 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 was provided at an environmental temperaturearound 20 °C and water temperatures of 40 °C and 45 °C in winter. We consideredthe possible effect of body temperature during rest, and seasonal variation on the physiologicalreaction to foot bathing.

Acknowledgments

Acknowledgments: This work was supported by JSPS Grant-in-Aidfor Young Scientists (B) 22792144.

The authors declare no conflict of interest.

REFERENCES