Skip to main content
Journal of Wood Science

Official Journal of the Japan Wood Research Society

Download PDF

Psychological and physiological effects of sole contact with oil-finished wood

Journal of Wood Science volume 70, Article number: 21 (2024) Cite this article

Abstract

In Japanese households, it is customary to walk barefoot on wooden floors. Previous reports on the psychological and physiological relaxing effects of feet contact with uncoated solid wood have already been published. However, there are no studies on the effects of feet contact with coated wood, which is commonly used for residential floors. This study aimed to validate the psychological and physiological relaxing effects of sole contact with oil-finished wood. In total, 27 women university students (mean age: 21.9 ± 1.9 years) participated in this study. Psychological indices such as the modified semantic differential method and the Profile of Mood States Second Edition were used. The oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex were determined using near-infrared time-resolved spectroscopy. The sympathetic nervous activity and the parasympathetic nervous activity were measured using heart rate variability. The flat plate for tactile stimulation was oil-finished wood, and uncoated wood and marble were used for comparison. The sole of the feet of each participant touched each material for 90 s. Feet contact with oil-finished and uncoated wood had relaxing effects on psychological and physiological responses compared with marble. The relaxing effects of oil-finished wood and uncoated wood were similar. That is, they significantly increased subjective feelings of comfort and relaxation, improved mood states, and decreased oxy-Hb concentration in the left prefrontal cortex compared with marble. However, there were no statistically significant differences in terms of right prefrontal cortex and sympathetic nervous activities between oil-finished wood and marble. Oil-finished wood had a slightly weaker physiological relaxation effect than uncoated wood.

Introduction

Wood is a common representative natural material as it has long been used for housing and other construction purposes. Empirically, it has a relaxing effect among humans. Miyazaki advocated the “back to nature theory,” which states that our bodies can naturally adapt and that we relax by coming into contact with natural stimuli [1]. For approximately 6–7 million years, our ancestors have started evolving into the modern humans we are today [2]. Over 99.99% of our evolutionary timeline involved living in a natural environment, and our bodies have evolved to cope with the natural environment. In stressful situations currently experienced in urban environments, exposure to nature-derived stimuli such as wood promotes relaxation and brings us physiologically closer to our original state as human beings.

Hand or feet contact with wood promotes a sense of relaxation. However, data on the physiological relaxation effect based on physiological indicators such as brain activity, autonomic nervous activity, and endocrine activity are limited [3]. The accumulation of scientific data began with palm [4,5,6,7] and feet contact [8, 9] studies. Palm contact with uncoated solid wood, Japanese cedar [4], Japanese cypress [5], and white oak [6, 7] promotes physiological relaxing effects by calming the prefrontal cortex activity, increasing the parasympathetic nervous activity and decreasing the sympathetic nervous activity. The physiological relaxing effects of sole contact with uncoated Japanese cedar [8] and Japanese cypress [9] is similar to those of palm contact. Previous studies have shown that palm and feet contact with uncoated solid wood has physiological relaxing effects on the human body and brain.

However, in wood actually use, various types of coating are often applied to prevent staining and scratching. The effects of contact with coated wooden materials among humans should be validated. In a palm contact experiment, the participants were exposed to different coated wooden materials crafted from white oak [7]. Uncoated solid wood has physiological relaxation effects compared with other varieties of coated wood such as urethane- or glass-finished. However, contact with oil-finished wood increased the parasympathetic nervous activity, which indicates physiological relaxation. Hence, oil-coated wood had a physiological relaxing effect that fell between that of uncoated solid wood and various types of coated wood.

This study aimed to assess the effects of sole contact with oil-finished wood on psychological and physiological responses.

Results and discussion

In the modified SD method, oil-finished and uncoated wood were rated as slightly comfortable. Hence, contact with oil-finished and uncoated wood were significantly more comfort than contact with marble (oil-finished wood: p < 0.001, PSdep = 0.857; uncoated wood: p < 0.001, PSdep = 0.929; Fig. 1A). Oil-finished and uncoated wood were rated as slightly relaxed. Thus, contact with oil-finished and uncoated wood were significantly more relaxation than contact with marble (oil-finished wood: p < 0.001, PSdep = 0.964; uncoated wood: p < 0.001, PSdep = 0.964; Fig. 1B). Oil-finished and uncoated surfaces were rated as slightly natural. Therefore, there was a significant difference between oil-finished and uncoated wood and marble (oil-finished wood: p < 0.001, PSdep = 0.929; uncoated wood: p < 0.001, PSdep = 0.964, respectively; Fig. 1C). Significant differences were also observed between oil-finished and uncoated wood and marble in terms of warm–cold feeling (oil-finished wood: p < 0.001, PSdep = 0.893; uncoated wood: p < 0.001, PSdep = 0.964; Fig. 1D), uneven–flat feeling (oil-finished wood: p < 0.001, PSdep = 0.964; uncoated wood: p < 0.001, PSdep = 0.929; Fig. 1E), and soft–hard feeling (oil-finished wood: p < 0.001, PSdep = 0.821; uncoated wood: p < 0.001, PSdep = 0.857; Fig. 1G). For dry–moist feeling (Fig. 1F), significant differences were found between marble and oil-finished wood only (p = 0.014, PSdep = 0.536). Although there was no significant difference, a similar change was also observed in uncoated wood (p = 0.067, PSdep = 0.536). In terms of contact with uncoated wood, the results of subjective evaluations using the modified SD method were consistent with those of previous studies on feet contact with Japanese cedar [8] and Japanese cypress [9]. Comfortable feeling, relaxed feeling, natural feeling, warm–cold feeling, uneven–flat feeling, and soft–hard feeling were almost identical between oil-finished and uncoated materials.

Fig. 1
figure 1

Subjective evaluation using the modified semantic differential method after sole contact with oil-finished wood, uncoated wood, and marble. A Comfortable feeling, B relaxed feeling, C natural feeling, D warm–cold feeling, E uneven–flat feeling, F dry–moist feeling, and G soft–hard feeling. N = 28, mean ± standard error. *p < 0.05 as determined using the Wilcoxon signed-rank test with Holm correction

Full size image

The POMS2 scores (Fig. 2) for the negative subscales anger–hostility (oil-finished wood: p = 0.007, PSdep = 0.357; uncoated wood: p = 0.006, PSdep = 0.357), tension–anxiety (oil-finished wood: p < 0.001, PSdep = 0.893; uncoated wood: p < 0.001, PSdep = 0.929), and total mood disturbance (oil-finished wood: p < 0.001, PSdep = 0.857; uncoated wood: p < 0.001, PSdep = 0.821) were significantly lower after contact with the oil-finished or uncoated wood rather than contact with the marble. The friendliness scale scores of oil-finished food and uncoated wood were significantly higher than those of marble (oil-finished wood: p < 0.001, PSdep = 0.571; uncoated wood: p < 0.001, PSdep = 0.643). The depression–dejection scale score was significantly lower only with an oil-finished wood (p = 0.002, PSdep = 0.429). However, similar changes were observed in uncoated wood (p = 0.045, PSdep = 0.321). No significant differences were found in confusion–bewilderment (oil-finished wood: p = 0.088, PSdep = 0.500; uncoated wood: p = 0.108, PSdep = 0.429), fatigue–inertia (oil-finished wood: p = 0.229, PSdep = 0.286; uncoated wood: p = 0.239, PSdep = 0.250), and vigor–activity (oil-finished wood: p = 0.027, PSdep = 0.464; uncoated wood: p = 0.222, PSdep = 0.464). The results on contact with uncoated wood were consistent with those of previous studies on feet contact with Japanese cedar [8] and Japanese cypress [9]. The POMS2 results of both uncoated and oil-finished wood were almost identical.

Fig. 2
figure 2

Subjective feelings using the Profile of Mood States Second Edition after sole contact with oil-finished wood, uncoated wood, and marble. A–H: anger–hostility, C–B: confusion–bewilderment, D–D: depression–dejection, F–I: fatigue–inertia, T–A: tension–anxiety, V–A: vigor–activity, F: friendliness, TMD: total mood disturbance. N = 28, mean ± standard error. *p < 0.05 as determined using the Wilcoxon signed-rank test with Holm correction

Full size image

Figure 3 depicts the average Δoxy-Hb concentrations in the left and right prefrontal cortex during 90 s of contact with three materials. In the left prefrontal cortex, the values were − 0.58 ± 0.16 µM (mean ± standard error) for oil-finished wood, − 0.45 ± 0.14 µM for uncoated wood, and 0.04 ± 0.16 µM for marble. Oil-finished wood and uncoated wood were associated with significantly decreased oxy-Hb concentration compared with marble (oil-finished wood: t(27) =  − 2.744, p = 0.011, d = 0.54; uncoated wood: t(27) =  − 2.524, p = 0.018, d = 0.43; Fig. 3A). In the right prefrontal cortex, the concentrations were − 0.33 ± 0.15 µM in oil-finished wood, − 0.54 ± 0.13 µM in uncoated wood, and 0.04 ± 0.19 µM in marble. In comparisons between materials, contact with uncoated wood showed a significant decrease compared to contact with marble (t(27) =  − 2.792, p = 0.010, d = 0.44, Fig. 3B), which is consistent with previous studies on feet contact with Japanese cypress wood [9]. There was no significant difference between oil-finished wood and marble (t(27) =  − 1.793, p = 0.084, d = 0.25, Fig. 3B). In the left prefrontal cortex activity, contact with oil-finished wood and uncoated wood significantly decreased compared to contact with marble. Only uncoated wood had a significant difference in terms of right prefrontal cortex activity, and oil-finished wood had a similar change. Both oil-finished wood and uncoated wood could relax the prefrontal cortex activity.

Fig. 3
figure 3

Prefrontal cortex activity during sole contact with oil-finished wood, uncoated wood, and marble. A The average oxy-hemoglobin (oxy-Hb) concentration in the left prefrontal cortex for 90 s during sole contact. B The average value of oxy-Hb concentration in the right prefrontal cortex. N = 28, mean ± standard error. *p < 0.05 as determined using the paired t-test with Holm correction

Full size image

No significant difference was observed in terms of respiratory rate; therefore, a statistical analysis of HRV data was performed. Figure 4 shows the average values of sympathetic nervous activity over 90 s. In Δln(LF/HF), which reflects sympathetic nervous activity, oil-finished wood − 0.21 ± 0.17, uncoated wood − 0.33 ± 0.17 and marble 0.26 ± 0.20, with uncoated wood showing a significant decrease compared to marble (t(27) =  − 2.663, p = 0.013, d = 0.50, Fig. 4). The oil finish wood had similar changes. However, it was not significant (t(27) =  − 2.663, p = 0.097, d = 0.33, Fig. 4). For contact with uncoated wood, the results were consistent with those of a previous study on feet contact with Japanese cypress wood [9]. In Δln(HF), which reflects parasympathetic nervous activity, there was an increase of 0.31 ± 0.13 lnms2 for oil-finished and 0.30 ± 0.14 lnms2 for uncoated compared to − 0.14 ± 0.16 lnms2 for marble, but the difference was not significant (oil-finished wood: t(27) = 2.191, p = 0.037, d = 0.42; uncoated wood: t(27) = 2.178, p = 0.038, d = 0.41).

Fig. 4
figure 4

Sympathetic nervous activity during sole contact with oil-finished wood, uncoated wood, and marble. The average value of the natural logarithm of the LF/HF of HRV for 90 s of sole contact. N = 28, mean ± standard error. *p < 0.05 as determined using the paired t-test with Holm correction

Full size image

Conclusions

Sole contact with both oil-finished and uncoated solid wood compared with marble induced psychological and physiological relaxation effects. Oil-finished wood had analogous relaxing effects compared with uncoated wood. In particular, tactile stimulation with oil-finished wood significantly increased the subjective feelings of comfort and relaxation, improved mood states, and decreased oxy-Hb concentrations in the left prefrontal cortex compared with tactile stimulation with marble. The right prefrontal cortex activity and the sympathetic nervous activity significantly differed between contact with uncoated wood and marble. Meanwhile, there were no significant differences between contact with oil-finished wood and marble. Hence, oil-finished wood can have a slightly diminished physiological relaxation effect compared with uncoated wood.

Materials and methods

Twenty-eight Japanese women (mean age: 21.7 ± 1.3 years) consented to participate in this study, which was conducted by the principles outlined in the Declaration of Helsinki. This study was approved by the Ethics Committee of the Center for Environment, Health and Field Sciences, Chiba University, Japan (Project Identification Code Number 41). This study is registered in the University Hospital Medical Information Network of Japan (Unique ID issued: UMIN000038729).

Japanese cedar (Cryptomeria japonica) wood was used as the base material for this experiment. Five wooden laminae without vertical joints (600 mm × 120 mm × 20 mm) were bonded together along their width. Furthermore, a second bonding was performed using plywood (600 mm × 600 mm × 24 mm) to prevent bending. The total thickness of the finished product was 44 mm. The surface was brushed with a stainless-steel wire brush and finished via either (1) plant oil containing perilla oil as the main ingredient applied once as a topcoat using a roll coater (hereafter referred to as “oil-finished wood”), or (2) uncoated solid wood with physiological relaxing effects based on previous studies [4, 8] on palm/sole contact (hereafter referred to as “uncoated wood”). A marble is a common building material. However, its properties differ significantly from those of wood. In this study, it was used for comparison. The physical properties of these materials are listed in Table 1.

Table 1 Details of the samples
Full size table

The within-subject experiment was conducted in a soundproof artificial climate chamber with a room temperature of 24 °C and humidity of 50%. Figure 5 depicts the measurement flow. The participants passively touched the samples with their soles for 90 s after resting for 60 s with their eyes closed. The oil-finished wood, uncoated wood, and marble used as tactile stimuli were acclimated to an environment of 24 °C and 50% humidity in the chamber the day before the experiment. Physiological indicators (Near-infrared time-resolved spectroscopy (TRS [10,11,12]) and heart rate variability (HRV [13,14,15,16,17,18,19])) were continuously measured from the start of rest to the end of stimulation. Subjective evaluations (The modified semantic differential (SD [20]) method and Profile of Mood States Second Edition (POMS 2 [21, 22])) were completed by participants after each sample exposure.

Fig. 5
figure 5

Measurement flow. TRS near-infrared time-resolved spectroscopy, HRV heart rate variability, Instr. instruction to the participants

Full size image

The Statistical Package for the Social Sciences software (v29.0; IBM Corp., Armonk, NY, the USA) was used in all statistical analyses. A p-value of < 0.05 was considered statistically significant in all cases. Holm correction was applied thrice to adjust the Familywise error rate in the comparison between stimuli [23]. Cohen’s d (d) [24] was calculated as the effect size for the physiological indices. Probability of superiority (PSdep) [25] was calculated as the effect size for each psychological index.

Other detailed materials and methods are available as Additional file 1.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Abbreviations

TRS:

Near-infrared time-resolved spectroscopy

oxy-Hb:

Oxyhemoglobin

HRV:

Heart rate variability

HF:

High frequency

LF:

Low frequency

SD:

Semantic differential

POMS 2:

Profile of Mood State Second Edition

T–A:

Tension–anxiety

D–D:

Depression–dejection

A–H:

Anger–hostility

F–I:

Fatigue–inertia

C–B:

Confusion–bewilderment

V–A:

Vigor–activity

F:

Friendliness

TMD:

Total mood disturbance

References

  1. Song C, Ikei H, Miyazaki Y (2016) Physiological effects of nature therapy: a review of the research in Japan. Int J Environ Res Public Health 13:781. https://doi.org/10.3390/ijerph13080781

    Article  PubMed  PubMed Central  Google Scholar 

  2. Brunet M, Guy F, Pilbeam D, Mackaye HT, Likius A, Ahounta D, Beauvilain A, Blondel C, Bocherens H, Boisserie JR, De Bonis L, Coppens Y, Dejax J, Denys C, Duringer P, Eisenmann V, Fanone G, Fronty P, Geraads D, Lehmann T, Lihoreau F, Louchart A, Mahamat A, Merceron G, Mouchelin G, Otero O, Pelaez Campomanes P, Ponce De Leon M, Rage JC, Sapanet M, Schuster M, Sudre J, Tassy P, Valentin X, Vignaud P, Viriot L, Zazzo A, Zollikofer C (2002) A new hominid from the Upper Miocene of Chad, Central Africa. Nature 418:141–151. https://doi.org/10.1038/nature00879

    Article  CAS  Google Scholar 

  3. Ikei H, Song C, Miyazaki Y (2017) Physiological effects of wood on humans: a review. J Wood Sci 63:1–23. https://doi.org/10.1007/s10086-016-1597-9

    Article  Google Scholar 

  4. Ikei H, Song C, Miyazaki Y (2019) Physiological effects of touching sugi (Cryptomeria japonica) with the palm of the hand. J Wood Sci 65:48. https://doi.org/10.1186/s10086-019-1827-z

    Article  CAS  Google Scholar 

  5. Ikei H, Song C, Miyazaki Y (2018) Physiological effects of touching hinoki cypress (Chamaecyparis obtusa). J Wood Sci 64:226–236. https://doi.org/10.1007/s10086-017-1691-7

    Article  Google Scholar 

  6. Ikei H, Song C, Miyazaki Y (2017) Physiological effects of touching wood. Int J Environ Res Public Health 14:801. https://doi.org/10.3390/ijerph14070801

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Ikei H, Song C, Miyazaki Y (2017) Physiological effects of touching coated wood. Int J Environ Res Public Health 14:773. https://doi.org/10.3390/ijerph14070773

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  8. Ikei H, Miyazaki Y (2020) Positive physiological effects of touching sugi (Cryptomeria japonica) with the sole of the feet. J Wood Sci 66:29. https://doi.org/10.1186/s10086-020-01876-1

    Article  CAS  Google Scholar 

  9. Ikei H, Song C, Miyazaki Y (2018) Physiological effects of touching the wood of hinoki cypress (Chamaecyparis obtusa) with the soles of the feet. Int J Environ Res Public Health 15:2135. https://doi.org/10.3390/ijerph15102135

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Torricelli A, Contini D, Pifferi A, Caffini M, Re R, Zucchelli L, Spinelli L (2014) Time domain functional NIRS imaging for human brain mapping. Neuroimage 85:28–50. https://doi.org/10.1016/j.neuroimage.2013.05.106

    Article  PubMed  Google Scholar 

  11. Ohmae E, Oda M, Suzuki T, Yamashita Y, Kakihana Y, Matsunaga A, Kanmura Y, Tamura M (2007) Clinical evaluation of time-resolved spectroscopy by measuring cerebral hemodynamics during cardiopulmonary bypass surgery. J Biomed Opt 12:062112. https://doi.org/10.1117/1.2804931

    Article  CAS  PubMed  Google Scholar 

  12. Ohmae E, Ouchi Y, Oda M, Suzuki T, Nobesawa S, Kanno T, Yoshikawa E, Futatsubashi M, Ueda Y, Okada H, Yamashita Y (2006) Cerebral hemodynamics evaluation by near-infrared time-resolved spectroscopy: correlation with simultaneous positron emission tomography measurements. Neuroimage 29:697–705. https://doi.org/10.1016/j.neuroimage.2005.08.008

    Article  PubMed  Google Scholar 

  13. Task Force of the European Society of Cardiology, the North American Society of Pacing and Electrophysiology (1996) Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation 93:1043–1065. https://doi.org/10.1161/01.CIR.93.5.1043

    Article  Google Scholar 

  14. Kobayashi H, Ishibashi K, Noguchi H (1999) Heart rate variability; an index for monitoring and analyzing human autonomic activities. Appl Human Sci 18:53–59. https://doi.org/10.2114/jpa.18.53

    Article  CAS  PubMed  Google Scholar 

  15. Kanaya N, Hirata N, Kurosawa S, Nakayama M, Namiki A (2003) Differential effects of propofol and sevoflurane on heart rate variability. Anesthesiology 98:34–40. https://doi.org/10.1097/00000542-200301000-00009

    Article  CAS  PubMed  Google Scholar 

  16. Sawada Y, Ohtomo N, Tanaka Y, Tanaka G, Yamakoshi K, Terachi S, Shimamoto K, Nakagawa M, Satoh S, Kuroda S, Iimura O (1997) New technique for time series analysis combining the maximum entropy method and non-linear least squares method: its value in heart rate variability analysis. Med Biol Eng Comput 35:318–322. https://doi.org/10.1007/BF02534083

    Article  CAS  PubMed  Google Scholar 

  17. Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan RA, Pizzinelli P, Sandrone G, Malfatto G, Dell’Orto S, Piccaluga E (1986) Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog. Circ Res 59:178–193. https://doi.org/10.1161/01.res.59.2.178

    Article  CAS  PubMed  Google Scholar 

  18. Kobayashi H, Park BJ, Miyazaki Y (2012) Normative references of heart rate variability and salivary alpha-amylase in a healthy young male population. J Physiol Anthropol 31:9. https://doi.org/10.1186/1880-6805-31-9

    Article  PubMed  PubMed Central  Google Scholar 

  19. Schäfer A, Kratky KW (2008) Estimation of breathing rate from respiratory sinus arrhythmia: comparison of various methods. Ann Biomed Eng 36:476–485. https://doi.org/10.1007/s10439-007-9428-1

    Article  PubMed  Google Scholar 

  20. Osgood CE, Suci GJ, Tannenbaum P (1957) The measurement of meaning. University of Illinois Press, Urbana, IL

    Google Scholar 

  21. Heuchert JP, McNair DM (2012) POMS 2, Profile of Mood States, 2nd edn. Multi-Health Systems Inc., New York

    Google Scholar 

  22. Heuchert JP, McNair DM (2015) Japanese translation of POMS2: Profile of mood states. Yokoyama K, Watanabe K (eds). Kaneko Shobo, Tokyo, Japan, pp. 1–156.

  23. Victor A, Elsässer A, Hommel G, Blettner M (2010) Judging a plethora of p-values: how to contend with the problem of multiple testing–part 10 of a series on evaluation of scientific publications. Dtsch Arztebl Int 107:50–56. https://doi.org/10.3238/arztebl.2010.0050

    Article  PubMed  PubMed Central  Google Scholar 

  24. Cohen J (1988) Statistical power for the Behavioral Sciences, 2nd edn. Erlbaum, Hillsdale, New Jersey, pp 1–579

    Google Scholar 

  25. Grissom RJ, Kim JJ (2012) Effect sizes for research: univariate and multivariate applications, 2nd edn. Routledge, New York, pp 1–456

    Book  Google Scholar 

Download references

Acknowledgements

This paper is an achievement of the “physiological effects of visual and tactile stimulation by solid wood” commissioned from the Tokyo Log Wholesalers’ Association. We would also like to express our gratitude to MARUHON, Inc. who provided sugi and marble samples and performed the surface processing of the samples. We are grateful to Hiromitsu Kobayashi of the Ishikawa Prefectural Nursing University for his contribution of analyzing the HRV signals to estimate the respiratory rate.

A part of this study was presented at the 70th Annual Meeting of the Japan Wood Research Society, Tottori, March 2020.

Funding

This work was performed as part of a research project funded by Tokyo Log Wholesalers’ Association.

Author information

Author notes

  1. Harumi Ikei and Yoshifumi Miyazaki are the co-corresponding authors and they contributed equally to this work.

Authors and Affiliations

  1. Center for Environment, Health and Field Sciences, Chiba University, 6-2-1 Kashiwa-no-ha, Kashiwa, Chiba, 277-0882, Japan

    Harumi Ikei, Hyunju Jo & Yoshifumi Miyazaki

  2. Institute for Advanced Academic Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan

    Harumi Ikei

Authors
  1. Harumi Ikei
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Hyunju Jo
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Yoshifumi Miyazaki
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

HI and YM contributed to the study conceptualization. HI and YM contributed to establishing the study design. HI and HJ performed data collection. HI conducted statistical analysis and interpretation. HI wrote the first draft of the manuscript. YM substantially contributed to the interpretation of the data and made important manuscript revisions. Each author is accountable for all aspects of the work. All authors read and approved the final manuscript.

Corresponding authors

Correspondence to Harumi Ikei or Yoshifumi Miyazaki.

Ethics declarations

Ethics approval and consent to participate

This study was conducted in accordance with the Declaration of Helsinki. It adhered to the regulations set by the Ethics Committee of the Center for Environment, Health, and Field Sciences, Chiba University, Japan (Project Identification Code Number 41). This study is registered in the University Hospital Medical Information Network of Japan (Unique ID: UMIN000038729).

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Additional file 1.

Detailed materials and methods.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ikei, H., Jo, H. & Miyazaki, Y. Psychological and physiological effects of sole contact with oil-finished wood. J Wood Sci 70, 21 (2024). https://doi.org/10.1186/s10086-024-02134-4

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s10086-024-02134-4

Keywords