
==== Front
BMC Res Notes
BMC Res Notes
BMC Research Notes
1756-0500
BioMed Central London

39227898
6918
10.1186/s13104-024-06918-1
Research Note
Crocus Sativus Linnaeus (Saffron) intake does not affect physiological and perceptual responses during a repeated sprint test in healthy active young males
http://orcid.org/0000-0002-8840-1735
Ouerghi Nejmeddine 123
http://orcid.org/0000-0001-6418-6711
Abassi Wissal 1
http://orcid.org/0000-0002-6328-4915
Jebabli Nidhal 1
http://orcid.org/0000-0003-1585-4052
Feki Moncef 2
http://orcid.org/0000-0003-0971-0183
Bouassida Anissa 1
http://orcid.org/0000-0003-1247-6754
Weiss Katja 4
http://orcid.org/0000-0002-6436-6306
Rosemann Thomas 4
http://orcid.org/0000-0002-2412-9103
Knechtle Beat beat.knechtle@hispeed.ch

45
1 https://ror.org/000g0zm60 grid.442518.e 0000 0004 0492 9538 Research Unit “Sport Sciences, Health and Movement” (UR22JS01) High Institute of Sport and Physical Education of Kef, University of Jendouba, Kef, 7100 Tunisia
2 Faculty of Medicine of Tunis, University of Tunis El Manar, Rabta Hospital, Tunis, LR99ES11, 1007 Tunisia
3 https://ror.org/01kzjzn40 grid.442516.0 0000 0004 0475 6067 University of Gafsa, High Institute of Sport and Physical Education of Gafsa, Gafsa, 2100 Tunisia
4 https://ror.org/02crff812 grid.7400.3 0000 0004 1937 0650 Institute of Primary Care, University of Zurich, Zurich, 8000 Switzerland
5 grid.491958.8 0000 0004 6354 2931 Medbase St. Gallen Am Vadianplatz, Vadianstrasse 26, St. Gallen, 9000 Switzerland
3 9 2024
3 9 2024
2024
17 24622 6 2024
28 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, 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 you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. 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-nc-nd/4.0/.
The study aimed to investigate the effects of acute ingestion of saffron (SAF) on physiological (i.e., heart rate and blood lactate) and perceptual (i.e., ratings of perceived exertion [RPE] and feeling scale) measures in response to a repeated-sprint ability test (RSS) in healthy young males (N = 22; mean ± SD: age, 21.7 ± 1.24 yrs.). All participants completed two experimental trials with a one-week washout period using a double-blind, placebo-controlled, crossover design. In each session, the participants were randomly chosen to receive either a capsule of saffron (300 mg) (SAF session) or a capsule of lactose (PLB session) two hours before performing the RSS.

No significant differences (p > 0.05) were found for heart rate, RPE, and feeling scale between the SAF or PLB sessions at pre- and post-RSS. There were no significant changes (p > 0.05) in peak time, total time, fatigue index, and blood lactate in either the SAF or PLB sessions. Acute SAF ingestion did not significantly improve RSS performance nor physiological and perceptual measures in active young males. Future trials should address the topic by using shortened/prolonged higher doses of SAF on biological, physical, physiological, and perceptual responses to acute and chronic exercise.

Keywords

Anaerobic performance; dietary supplement
Physical exertion
Repeated-sprint ability test
Saffron
issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcIntroduction

Athletes’ use of herbal medicinal products has increased during the past decade [1]. It is well established that nutritional supplements include nutrients not designated as doping agents that have a positive physiological or nutritional effect on physical performance without negative effects [2, 3]. Crocus sativus L., commonly known as “saffron crocus” is a plant belonging to the Iridaceae family from which the spice saffron (SAF) is derived. SAF has gained significant interest as a dietary supplement due to its potential physiological and perceptual benefits. It has a beneficial role in the nervous and cardiovascular systems by modulating the levels of neurotransmitters in the brain, maintaining healthy blood vessels, and lowering cholesterol and blood pressure [4, 5]. The effects of SAF are primarily attributed to its bioactive compounds, including crocin, crocetin, picocrocin, and flavonoids (quercetin, kaempferol, and naringenin) [4, 5]. The compounds exhibit antioxidant, anti-inflammatory, and anti-depressive, anti-tumor activities, which makes SAF a potential protective agent against cardiovascular and mental diseases, cancer, skeletal muscle injury, and more [6–11]. For example, crocin enhances mood and cognitive function by modulating neurotransmitter systems, offering potential therapeutic benefits for depressive symptoms and overall mental health [12]. Crocin and crocetin reduce oxidative stress and perceptual symptoms increasing people’s quality of life [13]. Safranal, a derivative of picocrocin hydrolysis possesses antidepressant, and neuroprotective effects [14]. SAF/quercetin supplementation improved physical strength and endurance performance [15–21] but some studies showed no impact on physical performance [22–24]. Previous studies mainly investigated the role of chronic SAF/quercetin supplementation. The role of acute SAF supplementation on anaerobic performance was rarely investigated [25], and no study has investigated effects of SAF or components on the ability to repeat sprints. According to previous studies, acute/prolonged intake of 300 mg of SAF was sufficient to produce potential antioxidant and ergogenic effects, improve isometric and isotonic force and anaerobic performance, and delay-onset muscle soreness [19, 20, 25]. The herein studies examined the impact of a single dose of 300 mg SAF on the ability to repeat sprint and physiological and perceptual measures in young males.

Methods

Participants

The study’s power calculation was computed using G*Power (Version 3.1.9.2, University of Kiel, Kiel, Germany) to estimate the sample size. The analyses of the T student mean showed that the study needed 22 participants to prove 80% power with a significance level of α = 0.05 to detect an effect size (d = 0.55). Participants were students at the High Institute of Sports and Physical Education of Kef (ISSEP of Kef, Tunisia) who volunteered to participate. Inclusion criteria were consenting male students aged 18 to 25 years. Non-inclusion criteria were acute/chronic illness, conditions that contraindicate intense physical exercise, participation in another physical program within the past 6 months, and recent (within 3 months) medication, or dietary supplementation/restriction. Exclusion criteria were consenting retirement, non-compliance to the physical program, and incomplete data. Of 38 eligible participants, 22 male students aged 21.7 ± 1.24 years responded to the inclusion and exclusion criteria and were included. As sports science students, participants are physically active subjects. They undertake 6 h of physical education classes per week. During the study, participants were asked to maintain their usual tasks, habitual physical activity, and eating behavior. All participants provided written consent after being informed of the study’s aims, benefits, and risks. The Ethics Committee of the ISSEP of Kef approved the study protocol (ISSEP-UR22JS01). All the procedures were performed in agreement with the Declaration of Helsinki. The study is registered in the Pan African Clinical Trial Registry (https://pactr.samrc.ac.za) with the ID PACTR202402599578303.

Study design

In this double-blind, placebo-controlled crossover trial, participants performed two experimental sessions with a one-week washout period. Each participant received three capsules of 100 mg saffron powder (SAF session) or three visually identical capsules of 100 mg lactose powder (PLB session). Two hours after ingesting the capsule, the participant performed the repeated sprint sets test (RSS) with measures of peak time (PT), total time (TT), and fatigue index (FI). Heart rate (HR) was measured before and during the RSS, and blood lactate (BL) concentration was measured immediately after the test. Ratings of perceived exertion (RPE) and feeling scale (FS) were measured before (Pre-RSS) and after (post-RSS) the test. After consuming the SAF/PLB capsules, participants were not allowed to eat or drink until they completed the RSS test. SAF used in this study is derived from the stigmas of Crocus sativus L. and standardized to contain > 3.5% Lepticrosalides. The product is supplied by Tiki Nature (US) as capsules containing 100 mg of SAF extract. Supplements were randomized and blinded to participants and investigators by a scientist not involved in the study. Research Randomizer (https://www.randomlists.com/team-generator) was used to assign the participant to an experimental condition. All subjects were prohibited from consuming any dietary supplements and were instructed to refrain from vigorous physical exercise for at least 24 h before each test session. To avoid circadian variation, the two sessions were conducted at the same time of day for each participant (± 1 h). The study design is shown in Fig. 1.

Fig. 1 Experimental protocol. BL, blood lactate; FI, fatigue index; FS, feeling scale; HR, heart rate; PLB, placebo; PT, peak time; RPE, rating of perceived exertion; RSS, repeated-sprint ability test; SAF, saffron; TT, total time

Repeated sprint sets test (RSS)

The RSS test was performed indoors at the university gymnasium on a synthetic hard floor. The test consisted of 2 sets of 5 × 20 m shuttle sprints, with 15 s active recovery between repetitions and 1 min between sets. Each sprint shuttle was performed with one direction change (180° turn) and was timed using a photocell system (Brower Timing System, Salt Lake City, 174 UT, USA; accuracy of 0.01 s), positioned approximately 3 m apart facing each other on each side located at the start and finish lines. Before beginning the tests, participants completed a 15-minute standardized warm-up. No verbal encouragement was provided during the tests. Participants were informed of the sprint number during each set. The following variables were derived from the RSA test: (a) PT: the best time of each RSA test; (b) TT: the sum of all 10-sprint times; (c) the FI: calculated as recommended by Fitzsimons et al. [26] from sprint running performance using the following formula:

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{FI}}(\% ){\text{ = }}\left( {\frac{{{\text{TT}}}}{{{\text{PT*NUMBER}}\;{\text{OF}}\;{\text{SPRINT}}}} - 1} \right){\text{*100}}$$\end{document}

Psycho-physiological measures

HR was continuously measured, before and during the RSS test, by an individual heart rate monitor (Polar, Lake Succes, NY) with pre (HRpre) and maximum (HRmax) values extracted as outcome variables. The Borg 6–20 scale was selected to rate the perceived intensity of exertion [27] Pre- and Post-RSS. To assess the participants’ mood, we used the FS [28]: FS was measured using Hardy and Rejeski’s bipolar feeling scale. Immediately after the RPE assessments, the participant was asked to respond to the question “How are you feeling right now?” by choosing one on the 11-point scale [from + 5 (very good) to -5 (very bad) with a midpoint of 0 (neutral)]. Furthermore, BL levels were assessed using a portable lactate monitor three minutes following the test (Lactate Pro, Akray, Tokyo, Japan).

Statistical analysis

Data were checked for normality using the Kolmogorov-Smirnov test and are presented as means ± standard deviation (SD). Two-way repeated measures ANOVA (session [PLB/SAF] *time [pre/post]) were used to compare the RPE and FS between sessions across time. Comparisons for TT, PT, FI, BL concentration, and HR were performed using the paired samples t-test. The effect size (ES) was calculated using the following criteria: ≤ 0.2, trivial; >0.2–0.6, small; >0.6–1.2, moderate; >1.2–2.0, large; and > 2.0, very large [29]. A 5% significance level was considered in all cases, and the data were analyzed in SPSS version 18.0 for Windows (SPSS Inc., Chicago, Illinois, USA).

Results

All participants were young males with the following characteristics: age, 21.7 ± 1.24 yrs.; height, 1.77 ± 0.08 m; body mass, 71.8 ± 8.59 kg, and body mass index, 22.8 ± 2.03 kg/m2.

Repeated sprint sets test indices

A descriptive analysis of RSS indices in PLB and SAF sessions was presented in Table 1. No significant changes were observed in TT, PT, and FI (p > 0.05) for both sets and in total time after acute SAF or PLB supplementation.

Table 1 Performance indices of repeated sprint sets in saffron and placebo trials

		Placebo	Saffron	p-value	Effect Size	
Set 1	Total time, s	17.8 ± 0.99	17.5 ± 1.26	0.160	0.27	
Peak time, s	3.42 ± 0.19	3.35 ± 0.26	0.148	0.31	
Fatigue index, %	3.97 ± 1.96	4.28 ± 1.93	0.616	0.16	
Set 2	Total time, s	18.0 ± 1.11	17.6 ± 1.16	0.107	0.36	
Peak time, s	3.49 ± 0.23	3.40 ± 0.22	0.096	0.41	
Fatigue index, %	3.41 ± 1.70	3.74 ± 1.79	0.575	0.19	
Total	Total time, s	35.8 ± 1.99	35.1 ± 2.39	0.091	0.33	
Peak time, s	3.39 ± 0.19	3.31 ± 0.24	0.066	0.38	
Fatigue index, %	5.51 ± 1.95	5.97 ± 2.05	0.425	0.24	
Data are expressed as mean ± SD

Heart rate and blood lactate concentration

Table 2 shows pre- and post-RSS values for HR and post-RSS BL concentration in PLB and SAF sessions. No significant differences (p > 0.05) were observed for HR before and after the RSS according to the supplement ingested. Similarly, no significant difference was observed for post-RSS BL concentration between PLB and SAF sessions.

Table 2 Heart rate at the inclusion (pre-RSS) and after (post-RSS) the repeated sprint sets (RSS), and Post-RSS blood lactate concentration in saffron and placebo trials

	Placebo	Saffron	p-value	Effect Size	
Pre-RSS heart rate, beat/min	82.8 ± 12.7	84.9 ± 12.2	0.640	0.17	
Post-RSS heart rate, beat/min	180.0 ± 10.5	183.1 ± 9.01	0.129	0.32	
Post-RSS blood lactate, mmol/L	14.4 ± 0.91	14.5 ± 1.02	0.668	0.11	
Data are expressed as mean ± SD

Perceptual indices

Table 3 shows pre- and post-RSS values for perceptual variables in PLB and SAF sessions and session*time interaction. No significant differences (p > 0.05) were observed for RPE and FS before and after the RSS according to the supplement ingested.

Table 3 Perceptual parameters at the inclusion (pre) and after (Post) of the repeated sprint sets (RSS) in saffron and placebo trials

		Placebo session	Saffron session	Paired t-test	session*time interaction	
				p	F	p	ηp2	
Rating of perceived excretion	Pre	12.0 ± 1.56	12.6 ± 2.09	0.158	0.159	0.692	0.004	
Post	13.4 ± 2.72	13.7 ± 1.99	0.586	
Feeling scale	Pre	2.77 ± 1.51	2.55 ± 2.06	0.673	0.450	0.832	0.001	
Post	1.95 ± 1.94	1.91 ± 2.14	0.890	
Data are expressed as mean ± SD

Discussion

The study showed no significant improvement in RSS indices (PT, TT, and FI), HR, BL concentration, or perceptual measures (RPE and FS) following acute ingestion of 300 mg SAF. Only one previous study has examined the acute effect of SAF ingestion (300 mg) in a 30-second Wingate anaerobic test, demonstrating significant improvements in Wingate test indices in young males [25]. Several previous reports have investigated the effects of prolonged SAF/quercetin intake on physical capacity in active and non-active individuals. Prolonged intake resulted in enhanced power output [15], improved exercise performance [16], increased isometric and isotonic force [20], and increased VO2max and endurance capacity [17, 18]. It also prevented the decline of maximum isometric and isotonic forces after eccentric exercise [19]. Other studies showed no effect of prolonged quercetin intake on muscle power in moderately trained individuals [30], on physical parameters in untrained men [31], on aerobic capacity in sedentary individuals [32], and soldiers [33], and on physical endurance in trained athletes [23]. Discrepancies could result from different dosages and duration of the SAF/quercetin intake and different subjects’ characteristics, including health status, tobacco use, dietary intake, body composition, and level of physical activity. The mechanisms by which SAF may affect physical performance are not fully elucidated. SAF and its components could act through their antinociceptive effects [19], facilitation of tissue oxygenation [34], and increase in muscle mitochondrial biogenesis [35].

Our study showed no effect of acute SAF supplementation on HR. The effects of SAF/quercetin intake on HR are controversial. Scholten and Sergeev [23] found no effect of 6 weeks of 1000 mg/day quercetin supplementation. However, Meamarbashi and Hakimi [36] demonstrated that 300 mg of SAF reduces resting blood pressure and HR in inactive girls during exhaustive treadmill exercise. It has been shown that SAF potently inhibits HR and contractility via the calcium channel-blocking effect [37]. SAF components could inhibit the extracellular Ca2+ influx and release of intracellular Ca2+ stores in the endoplasmic reticulum [38]. Reducing intracellular Ca2 + release may contribute to blood vessel relaxation [39].

Our results revealed no effect of acute SAF supplementation on BL. Data on SAF/quercetin intake on lactate are scarce. One study reported decreased lactic acid levels following a six-week quercetin supplementation [40]. Future work should focus on the anti-fatigue effects of acute SAF/quercetin intake in youth athletes.

SAF has been proposed as an efficacious and tolerable treatment for anxiety and depression [41, 42]. The psychological benefits of SAF and its constituents have been attributed to its anti-inflammatory, antioxidant, and antidepressant [41–44] properties. We found no significant effect of acute SAF intake on RPE and FS. Accordingly, previous studies showed no effect of prolonged quercetin supplementation on RPE during physical exercise in active subjects [22, 23, 35]. This suggests that SAF does not influence effort perception in trained individuals.

The present study has some limitations that should be mentioned. Participants’ meals before the test were not standardized, which could have influenced the results. The study didn’t explore a dose effect by using different dosages of SAF supplements. Some reports indicate a positive influence of SAF supplementation with a higher dose (400 mg) on cardio-metabolic parameters including body composition, blood pressure, homeostatic model assessment for insulin resistance, adiponectin, interleukin-6, and lipids [45, 46]. However, the studies did not report data on the physical performance effect. A dose of 300 mg SAF did not improve RSS performance. The effect of SAF would be more perceptible for higher and prolonged intake. Future trials should address the topic while using higher doses/prolonged intake of SAF in trained, untrained, and clinical populations.

Conclusions

The study results indicate that 300 mg of acute SAF supplementation did not improve the ability to repeat sprints or affect physiological and perceptual measures in healthy, physically active young males. Further investigations are necessary to investigate the effect of acute/prolonged SAF supplementation with different doses on biological, physical, physiological, and perceptual responses to acute and chronic exercise and to highlight the potential mechanisms.

Acknowledgements

The authors thank the participants who volunteered to participate in the study and for their kindness and courage.

Author contributions

NO, WA, NJ, MF and BK conceived and designed the study and revised the manuscript. NO, WA and NJ performed field and laboratory works and gathered the data. NO, WA, NJ, MF and BK analyzed the data and drafted the manuscript. AB, TR and KW helped in drafting the final version. All authors were given the opportunity to comment on and revise the manuscript. All authors read and approved the final version of the manuscript.

Funding

No external funding was received to support the current investigation.

Data availability

The datasets generated and/or analyzed during the current study are not publicly available due to data security before publication but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The experiment was fully approved by the local Ethics Committee of High Institute of Sports and Physical Education of Kef, Tunisia (ISSEP-UR22JS01) before the commencement of the assessments. All subjects were informed about the study protocol and signed an informed consent form before participating in the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Abbreviations

BL Blood lactate

FI Fatigue index

FS Feeling scale

HR Heart rate

RPE Ratings of perceived exertion

RSS Repeated-sprint sets

SAF Saffron

TT Total time

PT Peak time

PLB Placebo

Publisher’s note

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