A Four‐Day Cold Shower Protocol Does Not Increase Salivary Testosterone in a Small Cohort of Male Athletes: A Research Communication

ABSTRACT

Background and Aim

Testosterone is an important hormone in male physiology, playing a key role in reproductive function, muscle growth, bone mineral density, and metabolic regulation. Cold exposure is celebrated in fitness and wellness communities for its potential to elevate testosterone levels and improve performance and recovery. While enthusiasm runs high, it's essential to explore and appreciate the scientific evidence behind these exciting claims. Cold showers have become popular among athletes as a form of cold exposure and serve as a practical alternative to traditional cryotherapy. While some cold exposure treatments have been linked to temporary increases in testosterone levels, the effects of daily cold showers on salivary testosterone concentrations have not been thoroughly investigated.

Methods

In this study, 11 male current or former college athletes participated in a cold shower protocol. Baseline salivary testosterone samples were collected before the first cold shower. The participants underwent 10‐min cold showers at 17°C for four consecutive days. A final saliva sample was taken within 24 h after the cold shower sessions to assess changes in salivary testosterone levels, which were then compared to the average pre‐intervention values.

Results and Conclusion

The results showed varied individual responses: some participants experienced increased testosterone levels, others had reduced levels, and several showed negligible changes. Overall, the group‐level analysis indicated no statistically significant changes in salivary testosterone following the cold shower intervention. These findings suggest that short‐term, moderate exposure to cold showers does not consistently affect salivary testosterone levels in young adult male athletes. Future studies should examine the minimum number of cold shower exposures needed to improve salivary testosterone levels in athletes and investigate the small effects.

1. Introduction

Testosterone is a crucial hormone in males, significantly influencing reproductive functions, muscle growth, bone density, and overall metabolic health. Recently, there has been growing interest in sports science in non‐pharmacological methods that can positively influence hormonal responses, such as increasing testosterone levels to enhance recovery and overall performance [1, 2, 3].

Research on the effects of cold exposure on hormonal responses has yielded inconclusive results. Some studies indicate that short‐term cold exposure, whether through cold water immersion, cryotherapy, or winter swimming, may temporarily alter endocrine markers [4]. Cold water immersion is effective in reducing inflammation and muscle damage after exercise; its effects on testosterone levels can vary significantly [2, 3]. This variability may be attributed to factors such as exposure duration, cold intensity, baseline fitness levels, and the timing of exercise relative to cold exposure [5]. Recent reports suggest that there is insufficient evidence to support a consistent effect on testosterone levels; therefore, more well‐controlled studies are necessary to better understand these effects [3, 5].

Research has shown that cold showers can aid cardiovascular recovery in well‐conditioned athletes. These athletes often recover more quickly, exhibiting faster declines in heart rate and systolic blood pressure after training [6]. Taking cold showers after exercise helps stabilize skin and core temperatures, which in turn improves the accuracy of hydration assessments following intense activity [7]. Studies also indicate that cold showers after exercising in hot conditions can enhance thermal comfort and accelerate heart rate recovery [8]. Furthermore, regular exposure to cold showers may enhance the body's temperature regulation and aid athletes in performance and recovery [9].

Despite the growing popularity of cold exposure techniques among athletes, there is a notable lack of research on the short‐term effects of daily cold showers. Thus, in this study, we hypothesize that four consecutive days of cold showers will elevate salivary testosterone levels in adult male athletes.

2. Materials and Methods

2.1. Experimental Design and Participant Recruitment

This study employed a single‐arm pre‐post intervention design with within‐subject repeated measures (Figure 1). The study sample included 11 adult male athletes aged 18–24 years (mean age 21.2 years, SD = 1.3) (Figure 2). Body composition was measured with a whole−body dual−energy X−ray absorptiometry scan (iDXA, GE Healthcare Lunar). On average, they had a height of 1.8 m (SD = 0.1) and a total body weight of 87 kg (SD = 15). The average fat‐free mass was 69 kg (SD = 9), while the mean body fat percentage was 19.3% (SD = 7.6). All participants were current or former college athletes in volleyball, lacrosse, wrestling, and football. Descriptive characteristics for the study sample are provided in Table 1. The Adrian College Institutional Review Board for research involving human participants approved this study (IRB number: 09‐23‐18). All procedures were conducted in accordance with the Declaration of Helsinki. Participant data were anonymized and encrypted to ensure confidentiality and data integrity.

Figure 1.

Timeline for testing and cold shower intervention. CS, a cold shower for 10 min of exposure to water maintained at 17°C (n = 11).

Figure 2.

Standards for reporting in the present study: a flow diagram of participant enrollment, non‐randomized assignment to interventions, and analysis of the cold shower intervention (n = 11) [10].

Table 1.

Male participant characteristics (n = 11).

Variable	Mean ± SD
Age (years)	21.2 ± 1.3
Height (m)	1.8 ± 0.1
Body weight (kg)	87 ± 15
Fat‐free mass (kg)	69 ± 9
Body fat (%)	19.3 ± 7.6

Note: Values are means ± SD, standard deviation.

2.2. Study Procedures and Sample Collection

Salivary testosterone reflects the unbound, bioactive fraction of the hormone, which is the most physiologically relevant. Research has demonstrated moderate‐to‐strong correlations between salivary and serum free testosterone concentrations [11, 12]. Participants were instructed to avoid eating, drinking (particularly caffeine), smoking, vigorous exercise, or consuming alcohol within 6 h of sample collection. Adhering to these pre‐collection guidelines enhances confidence that any observed variability is attributable to true biological differences rather than modifiable pre‐analytical factors, and it facilitates replication in future research. Furthermore, saliva samples were obtained both pre‐intervention (pretest‐one and pretest‐two) and post‐intervention, aligning with the study's objective to examine short‐term, repeated effects. Baseline salivary testosterone samples were collected before the first cold shower. Over four consecutive days, participants completed a supervised daily cold shower protocol consisting of 10 min of exposure to water maintained at 17°C, with temperature verified at each session. Prior research indicates that even brief exposure to cold water, commonly incorporated into regular shower routines at temperatures between 10°C and 17°C for 30 s to 15 min, can be sufficient to produce both immediate and delayed physiological responses [1, 13, 14, 15, 16, 17]. During the pre‐intervention phase, we calculated the average values from two testing trials, referred to as pre‐test one and pre‐test two.

We then compared the averages to the values obtained after the cold shower protocol (post‐intervention) within 24 h after repeated cold shower exposure [18]. All saliva samples were collected at 8:00 a.m. during each visit and multiple pre‐intervention measurements were taken to account for within‐person biological variability differences (Supporting Information S1: Figures S1,S2). Saliva samples were brought to room temperature, vortexed to mix thoroughly, and then centrifuged for 15 min at approximately 3000 rpm. Testosterone levels were measured using a highly sensitive enzyme immunoassay, using 25 μL of saliva for each measurement.

The assay had a detection limit of 1 pg/mL, with a standard curve ranging from 6.1 to 600 pg/mL. The average intra‐assay variability was 4.60%, while inter‐assay variability averaged 9.85% (Salimetrics, Carlsbad, CA). To determine the differences between the pre‐intervention and post‐intervention measurements of salivary testosterone, we conducted a two‐sided paired samples t‐test using GraphPad Prism (version 10.0). In addition, for the supplementary data, we conducted a one‐way repeated‐measures ANOVA to analyze salivary testosterone using GraphPad Prism (version 10.0). The significance level for all comparisons was set at α ≤ 0.05.

3. Results and Discussion

The mean testosterone levels were 303.5 pg/mL (SD = 68.9) for pre‐intervention and 305.6 pg/mL (SD = 108.3) for the post‐intervention. The mean change in testosterone (post‐intervention minus averaged pre‐intervention) was 2.14 units (95% CI: −62.03 to 66.31). The standardized within‐subject effect size was negligible (Cohen's d_z = 0.02) (Table 2).

Table 2.

Summary of pre‐intervention (average of pretest‐one and pretest‐two), post‐intervention, and change in salivary testosterone (pg/mL) in male participants (n = 11).

	Pre‐intervention	Post‐intervention	Δ
n	11	11	11
Mean ± SD	303.5 ± 68.9	305.6 ± 108.3	2.14 ± 95.5
Median (IQR)	279.3 (261.7–347.8)	296.7 (227.1–362.9)	−29.15 (−55.45 to 67.65)
Mean (95% CI)	257.2–349.7	232.9–378.3	2.14 (−62.03 to 66.31)

Note: Values are means ± SD, standard deviations, medians (IQR, interquartile ranges), and means (95% CI, confidence intervals).

The results showed no consistent changes across the sample (Figure 3), with some individuals experiencing slight increases and others showing decreases (Figure 4). Contrary to our hypothesis, testosterone levels did not show a clear pattern of change, indicating that repeated cold shower exposure over 4 days does not significantly affect testosterone concentrations measured in saliva in college male athletes.

Figure 3.

The effects of cold‐water showers on salivary testosterone levels (pg/mL). The pre‐intervention phase was the average of two testing days (pretest‐one and pretest‐two). The post‐intervention phase occurred after four days of cold shower exposure consisting of 10 min of exposure to water maintained at 17°C. There were no pre‐intervention to post‐intervention changes (p > 0.05) in salivary testosterone among male athletes (n = 11). Values are presented as box‐and‐whisker plots with the whiskers showing maximum and minimum values, the box the IQR, and the line is the median.

Figure 4.

The effects of cold‐water showers on individual salivary testosterone levels (pg/mL). The pre‐intervention phase was the average of two testing days (pretest‐one and pretest‐two). The post‐intervention phase occurred after four days of cold shower exposure consisting of 10 min of exposure to water maintained at 17°C. There were no pre‐intervention to post‐intervention changes in salivary testosterone (p > 0.05) in male athletes (n = 11). Values are also presented as box‐and‐whisker plots with the whiskers showing maximum and minimum values, the box the IQR, the cross (+) shows the mean, and the line is the median.

This supports our conclusion that practical cold‐exposure methods, such as cryotherapy, immersion, or showers, do not consistently alter testosterone levels in male athletes. While Grasso et al. [19] documented acute increases in salivary testosterone after extreme cryotherapy (−110°C), these results likely stem from the highly stressful, short‐term nature of exposure in elite athletes. Earp et al. [20] demonstrated a reduction in post‐exercise serum testosterone levels following cold‐water immersion, which only occurred when cold exposure coincided with heightened endocrine responses to resistance exercise. Conversely, our intervention was carried out during rest, where the potential for hormonal changes appears minimal. Future studies should investigate the minimum number of cold shower exposures required to enhance salivary testosterone levels in athletes and analyze the subtle effects.

Salivary testosterone reflects the unbound, biologically active fraction of circulating testosterone and correlates well with serum levels [12, 21, 22]. Cold exposure, particularly cold showers, is widely promoted in fitness and wellness circles as an easy way to “boost testosterone” and enhance performance or recovery. However, the popularity and marketing of these claims often outpace the available scientific evidence. Our findings demonstrate that cold showers did not produce a measurable increase in morning salivary testosterone levels. While the present data offer preliminary insights into the effects of cold shower exposure on testosterone, several limitations must be acknowledged. The sample size in this study is relatively small. We recognize that larger and better‐controlled studies, such as those including a control condition, longer follow‐up periods, or additional physiological outcomes, will be essential to determine whether cold showers can influence testosterone in specific contexts or subgroups. Due to inter‐individual differences in salivary testosterone levels, the study may be underpowered to detect differences between pre‐intervention and post‐intervention measurements, potentially leading to the observation of natural variance rather than true effects. To address this variation, multiple baseline samples were collected to illustrate this likely trend. The absence of a consistent upward or downward trend in the data supports the conclusion that short‐term cold shower exposure exerts minimal effects on salivary testosterone levels. Further research may also help clarify whether commonly reported effects are due to expectancy, behavioral changes, or mechanisms unrelated to testosterone.

Cold showers are beneficial due to their accessibility, affordability, and ease of standardization in both research and applied contexts. Our results suggest that such interventions are unlikely to increase testosterone levels. In conclusion, contrary to our hypothesis, salivary testosterone levels did not change after 4 days of daily cold showers. These findings are specific to a 4‐day, 17°C, 10‐min cold shower protocol conducted in a small sample of male athletes with morning salivary sampling and may not be generalizable beyond these conditions. Our findings suggest that cold showers do not trigger a significant hormonal response in adult male athletes, as there were no consistent increases in salivary testosterone under the conditions we tested. However, we cannot rule out the possibility of small effects occurring in this population.

Author Contributions

D. A. Traylor and S. M. Phillips designed the research. D. A. Traylor, E. A. Nunes, M. J. Lees, and S. M. Phillips conducted the research. D. A. Traylor, E. A. Nunes, M. J. Lees, and S. M. Phillips performed the statistical analysis. D. A. Traylor, E. A. Nunes, M. J. Lees, E. Cudaback, and S. M. Phillips wrote the manuscript. All authors have read and approved the final version of the manuscript.

Funding

The authors have nothing to report.

Ethics Statement

This study received approval from the Adrian College Institutional Review Board for research involving human participants.

Consent

The participants have read and understand the provided information and have had the opportunity to ask questions. The participants voluntarily agreed to take part in this study.

Conflicts of Interest

D.A.T. reports owning Nutraceutical Innovations LLC. D.A.T. is listed as an inventor on US Patent 14/800,775. SMP reports grants or research contracts from the US National Dairy Council, Canadian Institutes for Health Research, Dairy Farmers of Canada, Roquette Freres, Ontario Centre of Innovation, Nestle Health Sciences, Myos, National Science and Engineering Research Council, Friesland Campina, and the US NIH during the conduct of the study; personal fees from Nestle Health Sciences, non‐financial support from Enhanced Recovery, outside the submitted work. S.M.P. has patents licensed to Exerkine but reports no financial gains from patents or related work. E.A.N., M.L., and E.C. declare no conflicts of interest.

Transparency Statement

The lead author, D. A. Traylor, affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Supporting information

Supporting File 1

Supporting Figures

Data Availability Statement

Data will be provided upon request and made available on public repositories where ethically appropriate.