Prolonged, high-intensity exercise causes muscle damage and produces reactive oxygen species, provoking an inflammatory response and altering cell function (1). Whilst inflammation is a necessary part of the tissue repair process (1), this often leads to muscular discomfort and a subsequent reduction in the ability to generate force (2). Following muscle damaging exercise, limitations of the endogenous antioxidant system to remove free-radicals delays recovery and reduces subsequent exercise performance in a time-course manner often referred to as delayed onset of muscle soreness (DOMS) (2).

Professional footballers in the UK are subject to a high number of competitive matches (>50 per season) and often short intervals between matches (48–72 h), which curtails recovery time and increases the risk of injury or sub-optimal performance (3). Football match-play is known to cause a significant increase in muscle damage and soreness up to 72 h post-match (4, 5), likely due to the high magnitude eccentric muscle loading (6). Professional footballers often use non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate DOMS and restore muscle function (7). However, concerns about the long-term use of NSAIDs and reported side effects, such as reduced muscle regeneration (7), and gastrointestinal problems (8) necessitates the need for alternative solutions (7).

Supplementation of certain dietary compounds may aid recovery by reducing inflammation, alleviating DOMS and restoring muscle function (9). Curcumin, a natural polyphenol found in high concentrations in turmeric, has anti-inflammatory, antioxidant, and analgesic properties, making it a candidate to accelerate post-exercise recovery. Laboratory-based studies of cycling, running and eccentric loading protocols (e.g., downhill running, eccentric resistance exercises), have shown that curcumin supplementation before and after an exercise period can reduce subjective soreness (10, 11), attenuate haematological inflammatory markers (11), and improve subsequent exercise performance (12, 13). However, there is an absence of applied studies in elite cohorts, likely due, in part, to challenges associated with conducting research in elite cohorts. One study, in elite rugby players, found that curcumin attenuated muscle damage and limited loss of muscle function after a muscle damaging protocol (12), while one other study in youth team male footballers found that curcumin attenuated DOMS and loss of muscle function after match-play (14). However, no study has explored whether a curcumin supplement can accelerate recovery from match-play in elite-level footballers. Elite sport is unique in terms of the playing intensity and specific contextual factors such as athlete skill level, psychological pressure and playing environment (crowd, score line, etc.), which make it hard to replicate in laboratory-based studies and/or with non-elite participants (15).

Whilst early findings are encouraging (15), whether curcumin can accelerate recovery and more rapidly restore muscle function in elite athletes is not well known. The aim of this study was to assesses if regular turmeric supplementation could accelerate markers of recovery, including, haematological inflammatory markers, subjective soreness, and performance, in elite male footballers following match-play. Participants consumed a commercially available turmeric supplement, formulated to contain 35 g of raw turmeric root with an estimated curcumin content of 1,400 mg (16), twice a day throughout the course of the study.

The aim of this study was to determine if twice daily consumption of a commercially available turmeric supplement, estimated to contain 1,400 mg of curcumin, could enhance recovery in a group of elite male footballers. We found that turmeric supplementation attenuated subjective markers of muscle soreness and reduced plasma [CRP] – a haematological marker of inflammation – at 64 h post-match, compared to a control group who did not consume the supplement. The results of this pilot study provide evidence that a commercially available turmeric supplement may be an effective and convenient method of accelerating recovery in elite male footballers.

Increased plasma [CRP] was observed in the control group 64 h post-match, but was attenuated in the turmeric supplementation group, indicating significant blunting of the systemic inflammatory response in participants consuming the turmeric supplement. CRP is a major acute phase protein synthesised by the liver in response to elevations in IL-6 and correlates with systemic inflammation (23). Turmeric contains high levels of the polyphenol curcumin, which has antioxidant and anti-inflammatory properties (24). Previous studies demonstrate that curcumin downregulates various inflammatory regulators, including nuclear factor kappa beta (NF-κB) activation and production of the enzyme cyclooxygenase-2 (COX-2), which are central components of the inflammatory cascade (11). Curcumin also increases blood antioxidant capacity, reducing the inflammation caused by free radicals (25). Therefore, the reduction in [CRP] at 64 h post-match likely reflects a reduction in systematic inflammation, indicating that turmeric supplementation has attenuated exercise-induced inflammation.

In contrast to [CRP], plasma [CK] did not differ between groups. CK is a protein found in the mitochondria of the muscle and can be used as a biomarker for muscle damage (26). The results of the present study are similar to another supplementation study, which found after an acute bout of eccentric bicep exercise, that [CRP] could be reduced by an antioxidant-docohexanoic supplement, but [CK] remained unchanged (27). Differences in [CK] and [CRP] response in the present study may be related to the training status of the population studied. Previous research has shown that plasma [CK] increases less in individuals accustomed to high volumes of exercise (28, 29) and can be influenced by muscle fibre type (30). Differences may also be due to the limited amount of control we were able to apply, due to the professional-status and elite nature of the population studied. For example, acute dietary intake of certain nutrients [such as vitamin C; (31)], which we were unable to measure or control in the present study, can influence plasma [CK]. Despite no club directed training taking place, it is also possible that the 5-days of rest prior to baseline measurements were insufficient for [CK] to reach nadir, which, coupled with these other factors, may explain why we did not observe a change in [CK] in response to turmeric supplementation.

Subjective muscle soreness was reduced with turmeric supplementation across all post-match time points. Previous studies have also similarly found that curcumin supplementation has reduced DOMS after exercise (10, 11), however, this finding is not consistent amongst all curcumin supplementation studies (12, 13, 32). Previous studies have ceased supplementation the day before (32) or 12 h after (13) exercise, which may explain the null findings. Tanabe et al. (33) found that curcumin supplementation for 4-days after exercise reduced muscle soreness, whereas supplementation for 7-days preceding exercise did not. These findings align with the current study and suggest that the analgesic effects of curcumin supplementation may be enhanced by continuing supplementation throughout the recovery period. This is likely explained by the pharmacokinetics of polyphenols, which typically peak a few hours after consumption before being metabolised and excreted (34).

Despite turmeric supplementation reducing CRP and subjective markers of soreness, this study found no effect of supplementation on CMJ and IMTP performance up to 48 h post-match. Previous studies have reported inconsistent findings regarding the effects of curcumin supplementation on performance, following a bout of exercise induced muscle damage. For example, curcumin supplementation can expedite recovery of some performance outcomes, such as MVC torque (13), range of motion (33) and 6 s sprint performance (12). However, other performance metrics, such at total work, mean peak torque (13) and MVC torque (33) were not different between when supplementing with curcumin. Abbott et al. (14) reported that curcumin supplementation offset the attenuation in CMJ performance observed after exercise-induced muscle damage from football match-play. These findings are directly comparable, in terms of exercise mode and performance metric, to the current study, yet present conflicting results. This may be due to the contextual differences in academy (14) compared to elite (current study) football match-play, and/or the degree of control that could be elicited around performance testing. For example, Abbott et al. (14) collected all measurements in the fasted state, whereas we were unable to control players dietary intake prior to measurements.

The supplement administered in this study was a 60 mL shot, which was well-tolerated and easy to incorporate into the nutrition plan of elite footballers. The supplement also contained piperine, an adjuvant that can greatly improve bioavailability of curcumin. High doses of curcumin (up to 12 g per day) are pharmacologically safe and well tolerated in humans (34). However, unformulated curcumin exhibits very poor bioavailability, with very low concentrations detected in serum and extracellular tissues after oral consumption, likely due to poor absorption, followed by rapid metabolism and elimination (24). Piperine slows the metabolism of curcumin by inhibiting hepatic and intestinal glucuronidation (24). Previous studies have shown that administering curcumin with piperine can increase serum concentrations of curcumin by up to 2000% (35), indicating that glucuronidation inhibition may be the major mechanism of increasing curcumin bioavailability (24). As such, the formulation of the supplement administered in the current study, which contained 35 g of raw turmeric root, (estimated to contain 1,400 mg of curcumin) and 10 mg of piperine, may have helped to increase serum concentrations of curcumin such that it could exert its biological action, whilst the mode of administration may have encouraged greater adherence. These are major strengths of this study, as these factors increase the likelihood of professional athletes utilising this supplement to expedite recovery.

Another strength of this study is the cohort of elite footballers studied, which is rare for this type of research. Whilst research in sub-elite populations can be informative, the contextual factors surrounding elite football are unique, and therefore, findings from sub-elite cannot always be readily extrapolated to elite athletes. Moreover, elite football match-play elicits a high degree of muscle damage and soreness (5), which results in many players using NSAIDs to manage pain and maintain performance amidst an intensive training and match-play schedule (36). However, chronic NSAID use has been associated with various adverse cardiovascular issues (37) and regular use is not recommended (38). As such, findings of the present study in this highly relevant population, provide evidence that a commercially available and easy to administer turmeric shot could reduce muscle soreness and expedite recovery after match-play.

This study is not without limitations. Firstly, despite the supplement being formulated to enhance bioavailability, this has not been empirically tested. Future studies should aim to measure the appearance of curcumin in blood, and the time course, to establish the optimal dosing strategy. Secondly, due to the novelty of the supplement provided and the population, we were unable to blind participants to the treatment they received. Previous research has showed that when participants perceive that they have ingested an active supplement this can distort perceptions of pain (39) and influence other outcomes, such as exercise performance (40). It’s important that future studies incorporate a suitable placebo condition to mitigate this risk. Thirdly, due to the novelty of the population studied, sample size for this study was inherently small, and turmeric and non-turmeric users could not be matched, as we could not control the match-day playing team. This resulted in a larger number of sample points for the supplementation group (60) compared to control (16).

In conclusion, this applied pilot study found that twice-daily consumption of a turmeric supplement attenuated a blood marker of inflammation and subjective muscle soreness, in elite male footballers following match-play. These findings suggest that a commercially available and easy to consume turmeric supplement may accelerate post-match recovery and this warrants further investigation.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Nottingham Trent University Human Invasive Ethics Committee (REF: 716). The patients/participants provided their written informed consent to participate in this study.

DC, RB, and IV: conceptualisation. DC, RB, PH, RJ, and IV: methodology. DC, RB, PH, RJ, CS, SG, RM, and IV: formal analysis. DC, RB, PH, RJ, CS, AC, RS, SG, RM, and IV: data curation, writing—review and editing, and project administration. DC, PH, RJ, CS, and IV: writing—original draft preparation. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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