Content uploaded by Andreas Kasper
Author content
All content in this area was uploaded by Andreas Kasper on Oct 14, 2020
Content may be subject to copyright.
High Prevalence of Cannabidiol Use Within Male Professional
Rugby Union and League Players: A Quest for Pain Relief
and Enhanced Recovery
Andreas M. Kasper
Liverpool John Moores University
S. Andy Sparks
Edge Hill University
Matthew Hooks, Matthew Skeer, Benjamin Webb, Houman Nia,
James P. Morton, and Graeme L. Close
Liverpool John Moores University
Rugby is characterized by frequent high-intensity collisions, resulting in muscle soreness. Players consequently seek strategies
to reduce soreness and accelerate recovery, with an emerging method being cannabidiol (CBD), despite anti-doping risks.
The prevalence and rationale for CBD use in rugby has not been explored; therefore, we recruited professional male players to
complete a survey on CBD. Goodness of fit chi-square (χ
2
) was used to assess CBD use between codes and player position.
Effects of age on use were determined using χ
2
tests of independence. Twenty-five teams provided 517 player responses. While
the majority of players had never used CBD (p<.001, V= 0.24), 26% had either used it (18%) or were still using it (8%).
Significantly more CBD use was observed in rugby union compared with rugby league (p= .004, V= 0.13), but player position
was not a factor (p= .760, V= 0.013). CBD use increased with players’age (p<.001, V= 0.28), with mean use reaching 41% in
the players aged 28 years and older category (p<.0001). The players using CBD primarily used the Internet (73%) or another
teammate (61%) to obtain information, with only 16% consulting a nutritionist. The main reasons for CBD use were improving
recovery/pain (80%) and sleep (78%), with 68% of players reporting a perceived benefit. These data highlight the need for
immediate education on the risks of CBD, as well as the need to explore the claims regarding pain and sleep.
Keywords:CBD, cannabis, DOMS, supplement
Rugby is a high-intensity collision sport that involves low-
intensity aerobic activities (e.g., standing, walking, and jogging)
combined with frequent periods of intermittent, intensive anaerobic
activities (e.g., sprinting, side stepping, passing, and collisions;
Austin & Kelly, 2013;Twist et al., 2014). In 1895, the game of
rugby was split into two variations—“league”and “union”—and,
despite differences in laws, the two games share many common
modalities with both based around frequent high-speed collisions.
As a consequence of these repeated collisions, players from both
codes of rugby experience increased markers of inflammation
(Cunniffe et al., 2011) and muscle soreness (Twist et al., 2012).
The muscle soreness in rugby is particularly pronounced, given it is
a combination of both exercise- and impact-induced muscle dam-
age (Naughton et al., 2017). This pain is often debilitating, affect-
ing everyday function, and can last several days postgame and
remain throughout the entire season (Fletcher et al., 2016). Players
and support staff, therefore, constantly strive to improve recovery
strategies and reduce pain with an emerging method being the use
of cannabidiol (CBD).
It is important to appreciate the fundamental difference
between cannabis and CBD. The cannabis plant contains over
100 cannabinoids, with the two most well-known being CBD and
tetrahydrocannabinol (THC). Although the exact nomenclature
has been argued (Piomelli & Russo, 2016), broadly speaking, the
cannabis plant has two major strains—Cannabis indica and
Cannabis sativa.TheCannabis sativa L-strain, more commonly
referred to as hemp, must contain less than 0.2–0.3% dry weight
THC, whereas other strains can contain up to 30% dry weight
THC and are often referred to as marijuana. Many European
countries have recognized the commercial value of hemp, and
a legal limit of 0.2–0.3% Δ
9
-THC is usually applied (Pellati et al.,
2018). This difference in THC concentration is crucial, given that
THC is the major psychotropic substance in cannabis, and it is
often the primary reason why marijuana is grown, whereas hemp
is grown for a variety of reasons, including clothing, shoes, rope,
insulation, biofuel, protein supplementation, and to produce CBD
as a nutritional supplement and/or medicine. While there are
country to country variations in the legality of CBD, in the United
Kingdom, CBD can be legally sold, providing that it does not
contain more than 1 mg of the controlled drug (or 1 μg, in the case
Kasper, Hooks, Skeer, Webb, Nia, Morton, and Close are with the Research Institute
for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool,
United Kingdom. Sparks is with the Sport Nutrition and Performance Research
Group, Department of Sport and Physical Activity, Edge Hill University, Ormskirk,
United Kingdom. Close (G.L.Close@ljmu.ac.uk) is corresponding author.
315
International Journal of Sport Nutrition and Exercise Metabolism, 2020, 30, 315-322
https://doi.org/10.1123/ijsnem.2020-0151
© 2020 Human Kinetics, Inc. ORIGINAL RESEARCH
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
of lysergide or any other N-alkyl derivative of lysergamide) in the
final “container,”that is, in the bottle or packet that it is sold in
(United Kingdom Government Home Office, 2020). Almost all
other cannabinoids, except CBD, remain subject to the Misuse of
Drugs Act 1971. There are a variety of forms of CBD that are
commercially available for sale, including oils, capsules, sprays,
tinctures, and gummies. From an athletic perspective, numerous
claims have been made to suggest the possible benefits for athletic
populations.
It has been reported that CBD possesses anxiolytic, anti-
inflammatory, anti-oxidative, and analgesic properties(Bergamaschi
et al., 2011;Mechoulam & Hanus, 2002), as well as suggested that it
improves sleep quality (Russo et al., 2007). Importantly, it has also
been suggested that CBD has a relative safe adverse effects profile
(Bergamaschi et al., 2011), with side effects including tiredness and
changes in appetite and weight (Iffland & Grotenhermen, 2017). The
majority ofresearch into CBD and inflammation has been performed
in rodent models (Xiong et al., 2012), and therefore the evidence
supporting its practical application with athletes, at present, remains
weak (Close et al., 2019). Moreover, CBD research is usually
performed in combination with other cannabinoids, commonly THC
(van de Donk et al., 2019), in something referred to as the entourage
effect (Russo, 2019), raising doubts over the efficacy of pure CBD
supplementation for athletes.
Although it is possible to produce synthetic CBD, in Europe,
CBD must come from an industrial hemp strain than is European
Union approved or come from outside the European Union. Given
that CBD must come from the hemp plant, it is of no surprise that
traces of THC are usually found in CBD products. While, legally,
theremustbelessthan1mgofTHCinthefinal container, recent
reports have suggested that this is not always the case, with
studies suggesting that some commercially available products
contain significantly higher amounts of THC than stated on the
label, even, in some cases, greater than the legal threshold (Gurley
et al., 2020), along with other illegal cannabinoids (Poklis et al.,
2019). From an athletic perspective, this is worrying not only
from a legal perspective but also in terms of an anti-doping viola-
tion, given that all cannabinoids, except CBD, are currently pro-
hibited substances by the world Anti-Doping Agency (WADA).
Despite CBD being removed from the WADA prohibited list in
2018 (both in and out of competition), its use in professional sport
remains highly contentious and poses a significant risk to athletes.
This is not only due to the possibility of THC being present in
excess of the legal threshold, but also, to date, there has been no
research to suggest what effects taking varying amounts of legal
CBD has on urine THC concentrations. It is for these reasons
that many sporting bodies currently advise against CBD use;
however, media reports would suggest that athletes are ignoring
this advice and using it to enhance recovery. It is, therefore,
essential that the prevalence and rationale for CBD use is studied
to guide immediate education strategies and highlight areas for
future research.
To this end, the aim of the present study was to establish the
prevalence of CBD use in a large sample (>500) of professional
rugby league and union players. Rugby was chosen as the sport to
study given that media reports have suggested that there are many
players using CBD and because the nature of the sport is one
whereby remedies to alleviate muscle soreness are frequently used.
We hypothesized that CBD use (past and present) would be high
(>20%) in professional players, with an increasing prevalence in
the older players and those players who play in the “forward”
position.
Methods
Overall Study Design
Professional male players from 30 rugby teams competing within
the English Premiership, U.K.-based Pro 14 (Rugby Union) and
Super League (Rugby League) competitions were invited to par-
ticipate in this observational study. Data were collected during the
2019–2020 season from 25 clubs (from the 30 invited), totaling 517
responses. At the time of data collection, all players were part of the
senior squad and aged 18 years and older. All English Premiership
teams and Scottish Pro 14 teams, 25% of Welsh Pro 14 teams, and
83% of Super League teams participated (Figure 1). Players were
given a short anonymous online multiple-choice survey consisting
of 15 questions surrounding CBD use products, with assumed
consent provided via a consent statement and submission of the
survey. Each team was provided a code, only known by the lead
researcher, to identify teams for relevant feedback where requested
by organizations. Survey responses were coded and entered into
Microsoft Excel prior to analysis. The study was approved by
Liverpool John Moores University Ethics Committee (M20_SPS_
966, 21/02/20).
Survey Design
The survey was designed by the research team, with extensive
experience within the elite rugby environment, to identify the
current use of CBD within elite rugby and to assess athlete under-
standing and knowledge of key areas. A copy of the survey can be
seen within Appendix. In brief, the survey was split into eight
sections: (a) demographics (age, code of rugby, and positional
group), (b) awareness of CBD, (c) use of CBD, (d) rationale for use,
(e) experience of use, (f) efficacy of use, (g) understanding of anti-
doping, and (h) further comments.
Data Analysis
Data were organized based on demographic information for age
group (18–23, 23–28, and >28 years), rugby code (league and
union), player position (forwards and backs), and team. Data are
presented as percentage of responses, but analysis was conducted
on the frequency data. Goodness of fit chi-square (χ
2
) was used to
assess CBD use in the sample population, between codes and
player position. Effect sizes were calculated using Cramer’sV,
which was interpreted as small (0.1–0.3), medium (0.3–0.5), and
large (>0.5). Chi-square tests of independence were used to deter-
mine differences between age groups. Post hoc analysis was
conducted by calculating Bonferroni adjusted pvalues from ad-
justed standardized residuals. A Kruskal–Wallis one-way analysis
of variance was used to assess differences between teams. Effect
sizes were calculated using epsilon square (ε
2
) and were interpreted
as weak (<0.04), moderate (0.04–0.16), and strong (0.64–1.0),
respectively. Statistical significance was set at p<.05, apart from
Bonferroni adjusted pvalues, which were calculated as the pvalue
from the adjusted standardized residuals divided by the degrees of
freedom. All data were analyzed using SPSS for Windows (version
25; IBM, Armonk, NY).
Results
There were a total of 18 U.K.-based teams that competed within the
English Premiership and Pro 14 rugby union competitions, along
IJSNEM Vol. 30, No. 5, 2020
316 Kasper et al.
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
with 12 teams that competed within the Super League rugby league
competition. Out of these, 517 players from 25 teams responded to
the survey (Figure 1).
Demographics
The mean age of players who responded was 25 (SD = 5, range
18–33) years. Sixty-seven percent (of the 517 respondents) came
from rugby union, with the remaining 33% from rugby league.
Of those who responded, 40% identified themselves as backs and
60% as forwards (Figure 1).
Awareness and Use of CBD
Of those responders to the survey, 91% (n= 472) indicated that
they had an awareness of CBD. Awareness came from a variety of
sources: Internet (73%), another teammate (61%), another player/
club (41%), nutritionist (16%), other staff members (4%), family/
friends (2%), the media (1%), and research (<1%; Figure 2a). Of
the 472 players that were aware of CBD (Figure 3a), significantly
more players had never used it (χ
2
= 121.9, p<.001, V= 0.24);
however a considerable proportion (26%) were either currently
(8%) or had previously (18%) used CBD. The proportion of
players either using or who had used CBD (Figure 4) varied signi-
ficantly across the teams sampled (H= 278.0, p<.001, ε
2
= 0.59).
A significantly higher number of players from rugby union
had either used or were using CBD (χ
2
= 8.29, p= .004, V=
0.13), but there were no observed differences between backs and
forwards (χ
2
= 0.09, p= .760, V= 0.013). Interestingly, CBD use
was significantly different across the age groups (χ
2
= 40.60,
p<.001, V= 0.28), with a lower number of players in the 18–
23 years age group (p<.0001) and more than expected players
using CBD in the 28 years and older age group (p<.0001). This
contrasted with the 23–28 years age group, which was not
observed to be significantly different from the expected number
of users (p= .053).
Rationale for Use
Of the 472 players aware of CBD, 339 had never used CBD. The
reasons surrounding this included being concerned about anti-doping
rule violations (ADRV; 64%), not aware of any benefit(37%),not
perceiving a need (29%), club advised against taking (23%), too
costly (2%), have not had the chance (1%), concerned about possible
side effects (1%), and lack of scientificevidence(<1%) (Figure 2b).
For the remaining 133 players who previously/currently used
CBD, the reasons were equally varied, including improving recov-
ery/pain (80%), sleep (78%), anxiety (32%), and for other medical
purposes (14%: help with concussion, long-term injury, and che-
motherapy; Figure 2c).
Figure 1 —Overview of recruitment for survey. CBD = cannabidiol.
IJSNEM Vol. 30, No. 5, 2020
CBD Use in Professional Rugby 317
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
Experience and Efficacy of CBD Use
Thirteen different CBD brands were being used by athletes, all
of which were oils or capsules. There was a disparity in reported
dose with athletes quoting percentages, drops, mgs, sprays, and
“rice-sized”quantities. Indeed, there was also diversity in the con-
centrations of CBD reportedly taken, ranging from 400 to 3,000 mg/
5–10% solutions in forms of drops (3–10 drops), tablets (10 mg), and
“rice-sized”quantities (“one grain”). A number of players (6%) were
either unsure of the brand they were using or mixing multiple brands,
with a further 39% unsure of the dose they were taking.
Despite the disparity in dose taken, many of the players
currently or previously taking CBD (n= 133) anecdotally perceived
abenefit (67%), including improved sleep (41%), recovery/pain
(14%), mood (6%), anxiety (3%), and other various medical pur-
poses (8%: concussion, chemotherapy, and long-term injury). No
player reported any perceived adverse effects (Figure 2d).
Understanding of Anti-Doping and Further
Comments
Of the players (n= 133) who had taken or were currently taking CBD,
52% were not concerned of committing an ADRV, with a further
79% believing the product they use to be batch tested for banned
substances and 21% unsure or aware that the product is not tested.
Of the 107 players that included additional commentary, 14%
used this space to indicate that they would try CBD in the future,
with 13% still unsure of the legality in and out of sport.
Discussion
The aim of the present study was to establish the prevalence
and reasons for CBD use in an extensive sample of elite rugby
players. To this end, we recruited 517 professional rugby players to
Figure 2 —Sources of information (a), reasons against (b), reasons for (c), and perceived benefits (d) of taking cannabidiol oil. ADRV = anti-doping
rule violations.
IJSNEM Vol. 30, No. 5, 2020
318 Kasper et al.
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
complete an online survey. We report, for the first time in elite
rugby players, that despite warnings from clubs and national
governing bodies against CBD use, >25% of all athletes surveyed
have either used or continue to use CBD. Moreover, in the older
players (>28 years old), almost 40% have or continue to use CBD,
with the major reasons cited including pain relief/recovery and to
improve sleep quality. These data suggest that many rugby players
are willing to accept the risks associated with CBD use in an
attempt to accelerate recovery and/or improve sleep. In addition
to the definitive requirement for immediate player education with
regard to the safety and risks of CBD supplementation, future
research should now also assess the efficacy of CBD supplements
on factors influencing recovery (e.g., pain, soreness, inflamma-
tion, sleep).
Rugby match play has been shown to result in both exercise-
and impact-induced muscle damage (Twist et al., 2012) that lasts
for several days postgame and persists throughout the entire
playing season (Fletcher et al., 2016). Daily muscle pain, especially
nerve pain, has been shown to have both physical (Cheung et al.,
2003) and psychological consequences that negatively affect daily
quality of life and even family life (Duenas et al., 2016). It is,
therefore, of little surprise that athletes have been shown to have
four times the use of painkillers compared with the general public
(Alaranta et al., 2006). Although research from other sports has
documented a high prevalence of painkiller use (Taioli, 2007;
Tsitsimpikou et al., 2009), data on rugby players are lacking. This
is despite the suggestion, both in academic literature (Gibbison
et al., 2014) and multiple reports in the mainstream media, that
rugby players are particularly reliant on the use of painkillers, such
as non-steroidal anti-inflammatory drugs, and opiates such as
Tramadol. The side effects associated with the chronic use of non-
steroidal anti-inflammatory drugs include gastric injury, gastric
ulceration, and kidney damage (Bertolini et al., 2001). Importantly
for rugby, increased risks also include bleeding and/or intracranial
hemorrhage post minor head injury (Sakr & Wilson, 2005).
Tramadol, which has been suggested to be widely used in rugby
players in the media, is effective in treating neuropathic pain
(Bravo et al., 2017); however, it is also not without serious side
effects, including nausea, headaches constipation, sleep distur-
bances (Walder et al., 2001), and withdrawal effects, as well as
drowsiness, which can significantly impair training and perfor-
mance. Given the muscle damage induced by rugby match play and
training (Hudson et al., 2019), combined with the side effects of
traditional pain medication, rugby players are now seeking alter-
nate pain relief strategies and ways to improve sleep.
We report that 78% and 80% of players used CBD to improve
sleep and pain/recovery, respectively. Interestingly, in the present
study, although the mean use of CBD was 26%, there was
increasing prevalence of use with increasing age, with the mean
usage reaching 39% in the players aged 28 years and older
category. Although it was not possible to assess the reason for
this, one could speculate that it is the older players who have
residual pain through a longer playing history, and that they are
more likely to be seeking pain relief medication. Of all the players
who have used CBD, 67% reported a perceived benefit of use, with
41% reporting improved sleep and 14% improved pain/recovery.
Interestingly, no athletes reported any adverse side effects,
although it must be considered that players may have taken a
negligible dose of CBD and/or taken a product with far less CBD
than stated on the label (Gurley et al., 2020), and therefore this
study should not be used as evidence that CBD does not cause side
effects. Future research should now be performed to explore the
veracity of such claims, which could have important consequences
for future advice and guidance offered to players.
Although the mean current/previous use of CBD was 26%, it
was interesting to observe that there was a significant difference
between teams with current/previous use ranging, from 5% to 70%.
Figure 3 —Varying usage (%) of CBD oil across (a) all surveyed
players, (b) different ages, (c) different codes, and (d) different playing
position. Bars represent data from those who currently (black), previously
(gray), or have never (white) taken CBD oil. CBD = cannabidiol.
Figure 4 —Individual team usage of CBD oil ranked lowest to highest
for previous/current use of CBD. Bars represent data from those who
currently (black), previously (gray), or have never (white) taken CBD oil.
CBD = cannabidiol.
IJSNEM Vol. 30, No. 5, 2020
CBD Use in Professional Rugby 319
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
Alarmingly, the players reported that the major source of CBD
information was either the Internet (73%) or a teammate (61%). It
is, therefore, possible that the interteam range could be related to
some players within a club having a major influence, although this
suggestion could not be fully explored in the present study and
should now be investigated further. This suggestion is, however,
further supported by the fact that only 16% and 4% sourced their
information from the team nutritionist or other staff member,
respectively. This low reliance on the team nutritionist could be
due to most clubs and governing bodies advising against CBD use
and, as a consequence, players not feeling comfortable to discuss
the potential use of CBD with internal staff members. Indeed, 23%
of players who did not use CBD cited their main reason not to use
was that the club had advised against it. In the free comments
section of the survey, 14% of players stated that they would like to
try CBD in the future. It is, therefore, crucial that players feel
comfortable discussing CBD with qualified staff rather than relying
on the Internet and/or other team members for their information
(Maughan et al., 2018).
Despite CBD being removed from the WADA prohibited list
in 2018, CBD use still poses a significant risk to athletes due to the
possibility of THC and other prohibited cannabinoids being present
in quantities sufficient to produce a urine sample greater than the
current threshold. Although 64% of players did not use CBD due
to fears of an ADRV, only 48% of current/previous users were
concerned about such a violation. In the free comments section,
13% of players stated that they were unsure of the legality of CBD
in rugby. The survey also asked athletes if they were aware if their
supplement was batch tested for other contaminants. Alarmingly,
21% of users did not know if their CBD supplement was batch
tested, whereas 79% claimed that the CBD product they were
consuming was tested. This belief that the product was tested was
of particular concern given that of all the CBD products listed, only
one appeared to be tested (tested by BSCG), yet just 39% of the
players reported to be using this specific product. It is, therefore,
likely that some players wrongly assumed that the CBD product
they were taking was batch tested, which could be related to the
lack of qualified advice they had received. Given that rates of
supplement contamination, which could result in an ADRV, have
been reported as high as 12–58% (Martínez-Sanz et al., 2017),
combined with the risks associated with CBD, it appears that many
rugby players are prepared to risk an ADRV and subsequent sanctions
in a quest to attenuate their pain and enhance recovery (including
promotion of sleep). This confirms the need for appropriate education
as well as greater efforts to provide appropriate pain relief for players.
The present study is not without its limitations, most of which
are a consequence of collecting data in professional athletes along-
side the collection of data that occurred during the COVID-19 crisis.
Although we managed to recruit more than 500 players, some teams
declined to participate in the research, with reasons cited including
the furlough of players and the potential for confusion, given they
had advised their players against using CBD. It is feasible that
players who had been advised not to use CBD did not take part in the
study, and, likewise, the players who did agree to participate may
have had more of an interest in CBD than those who declined. This
potential for systemic bias could have either overestimated or
underestimated the reported prevalence, which is a common prob-
lem in survey data when the entire population is not recruited.
Nonetheless, we are confident that with 25 teams and a mean of
21 players per team, these data do reflect the genuine usage within
elite professional rugby. Moreover, due to the anonymous nature of
the data collection, it was not possible to explore in depth the
rationale for usage and the perceived benefits. It was felt that the
anonymous nature was essential, given that the advice from the
clubs was not to use CBD, and, by keeping it anonymous, it would
allow us to collect more robust data. Future research should now
consider a more qualitative approach to fully understand the deci-
sions made by rugby players when it comes to CBD use. Finally,
while players did report benefits of CBD use, this could certainly be
a placebo effect, given that, to date, there are no randomized
placebo-controlled trials on the effects of CBD on recovery and
sleep in athletes. Future research must now address this gap in the
literature as well as assess the potential for CBD use to raise THC
concentrations above the current WADA thresholds.
In conclusion, we report, for the first time, a high prevalence of
CBD use, along with the rationale for its use in elite rugby players.
The data suggest that despite the majority of clubs advising against
CBD use, many players are ignoring this advice in an attempt to
improve sleep and pain management. These data highlight the need
for immediate education for rugby players on the potential con-
sequences of CBD use, as well as highlighting the need for future
research into the efficacy of CBD and the veracity of the anecdotal
claims from the players that it does help alleviate pain, enhance
recovery, and promote sleep.
Acknowledgments
The study was designed by A.M. Kasper, M. Hooks, M. Skeer, B. Webb,
H. Nia, J.P. Morton, and G.L. Close; data were collected and analyzed by
A.M. Kasper, M. Hooks, S.A. Sparks, and G.L. Close; and data interpre-
tation and manuscript preparation were undertaken by A.M. Kasper, J.P.
Morton, S.A. Sparks, and G.L. Close. All authors approved the final
version of the article.
References
Alaranta, A., Alaranta, H., Heliovaara, M., Airasksinen, M., & Helenius, I.
(2006). Ample use of physician-prescribed medications in Finnish
athletes. International Journal of Sports Medicine, 27(11), 919–925.
Austin, D.J., & Kelly, S.J. (2013). Positional differences in professional
rugby league match play through the use of global positioning
systems. Journal of Strength and Conditioning Research, 27(1),
14–19. doi:10.1519/JSC.0b013e31824e108c
Bergamaschi, M.M., Queiroz, R.H., Zuardi, A.W., & Crippa, J.A. (2011).
Safety and side effects of cannabidiol, a Cannabis sativa constituent.
Current Drug Safety, 6(1), 237–249.
Bertolini, A., Ottani, A., & Sandrini, M. (2001). Dual acting anti-
inflammatory drugs: A reappraisal. Pharmacology Research, 44(6),
437–450. doi:10.1006/phrs.2001.0872
Bravo, L., Mico, J.A., & Berrocoso, E. (2017). Discovery and develop-
ment of tramadol for the treatment of pain. Expert Opinion on Drug
Discovery, 12(12), 1281–1291. PubMed ID: 28920461 doi:10.1080/
17460441.2017.1377697
Cheung, K., Hume, P.A., & Maxwell, L. (2003). Delayed onset muscle
soreness. Sports Medicine, 33(2), 145–164. PubMed ID: 12617692
doi:10.2165/00007256-200333020-00005
Close, G.L., Kasper, A.M., & Morton, J.P. (2019). From paper to podium:
Quantifying the translational potential of performance nutrition research.
Sports Medicine, 49(Suppl.), 25–37. doi:10.1007/s40279-018-1005-2
Cunniffe, B., Hore, A.J., Whitcombe, D.M., Jones, K.P., Davies, B., &
Baker, J.S. (2011). Immunoendocrine responses over a three week
international rugby union series. Journal of Sports Medicine and
Physical Fitness, 51(2), 329–338.
IJSNEM Vol. 30, No. 5, 2020
320 Kasper et al.
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
Duenas, M., Ojeda, B., Salazar, A., Mico, J.A., & Falide, I. (2016). A
review of chronic pain impact on patients, their social environment
and the health care system. Journal of Pain Research, 9(1), 457–467.
PubMed ID: 27418853 doi:10.2147/JPR.S105892
Fletcher, B.D., Twist, C., Haigh, J.D., Brewer, C., Morton, J.P., & Close,
G.L. (2016). Season-long increases in perceived muscle soreness in
professional rugby league players: Role of player position, match
characteristics and playing surface. Journal of Sports Sciences,
34(11), 1067–1072. PubMed ID: 26368285 doi:10.1080/02640414.
2015.1088166
Gibbison, B., Bailey, C.R., & Klein, A.A. (2014). Tramadol—the marmite
drug. Anaesthesia, 70(2), 125–130. PubMed ID: 25491015 doi:10.
1111/anae.12972
Gurley, B.J., Murphy, T.P., Gul, W., Walker, L.A., & ElSohly, M. (2020).
Content versus label claims in cannabidiol (CBD)-containing pro-
ducts obtained from commercial outlets in the state of Mississippi.
Journal of Dietary Supplements. Advance online publication. doi:10.
1080/19390211.2020.1766634
Hudson, J., Cole, M., Morton, J.P., Stewart, C.E., & Close, G.L. (2019).
Daily changes of resting metabolic rate in elite rugby union players.
Medicine & Science in Sports & Exercise, 52(3), 637–644. doi:10.
1249/MSS.0000000000002169
Iffland, K., & Grotenhermen, F. (2017). An update on safety and side
effects of cannabidiol: A review of clinical data and relevant animal
studies. Cannabis Cannabinoid Research, 2(1), 139–154. PubMed
ID: 28861514 doi:10.1089/can.2016.0034
Martinez-Sanz, J.M., Sospedra, I., Ortiz, C.M., Baladia, E., Gil-Izquierdo,
A., & Ortiz-Moncada, R. (2017). Intended or unintended doping? A
review of the presence of doping substances in dietary supplements
used in sports. Nutrients, 9(10), 1093.
Maughan, R.J., Sherriffs, S.M., & Vernec, A. (2018). Making decisions
about supplement use. International Journal of Sport Nutrition and
Exercise Metabolism, 28(2), 212–219. PubMed ID: 29565185 doi:10.
1123/ijsnem.2018-0009
Mechoulam, R., & Hanus, L. (2002). Cannabidiol: An overview of some
chemical and pharmacological aspects. Part I: Chemical aspects.
Chemistry and Physics of Lipids, 121(1–2), 35–43. PubMed ID:
12505688 doi:10.1016/S0009-3084(02)00144-5
Naughton, M., Miller, J., & Slater, G. (2017). Impact-induced muscle
damage and contact-sport: Aetiology, effects on neuromuscular
function and recovery, and the modulating effects of adaptation
and recovery strategies. International Journal of Sports Physiology
and Performance, 13(8), 1–24.
Pellati, F., Borgonetti, V., Brighenti, V., Biagi, M., Benvenuti, S., & Corsi,
L. (2018). Cannabis sativa L. and nonpsychoactive cannabinoids:
Their chemistry and role against oxidative stress, inflammation, and
cancer. BioMed Research International, 2018, 1691428. PubMed ID:
30627539 doi:10.1155/2018/1691428
Piomelli, D., & Russo, E.B. (2016). The Cannabis sativa versus Cannabis
indica debate: An interview with Ethan Russo MD. Cannabis Can-
nabinoid Research, 1(1), 44–46. PubMed ID: 28861479 doi:10.1089/
can.2015.29003.ebr
Poklis, J.L., Mulder, H.A., & Peace, M.R. (2019). The unexpected
identification of the cannabimimetic, 5F-ADB, and dextromethorphan
in commercially available cannabidiol e-liquids. Forensic Science
International, 294, e25–e27. PubMed ID: 30442388 doi:10.1016/j.
forsciint.2018.10.019
Russo, E.B. (2019). The case for the entourage effect and conventional
breeding of clinical cannabis: No “strain,”no “gain.”Frontiers in
Plant Science, 9, 1969. PubMed ID: 30687364 doi:10.3389/fpls.
2018.01969
Russo, E.B., Guy, G.W., & Robson, P.J. (2007). Cannabis, pain, and sleep:
Lessons from therapeutic clinical trials of Sativex, a cannabis-based
medicine. Chemistry & Biodiversity, 4(8), 1729–1743. PubMed ID:
17712817 doi:10.1002/cbdv.200790150
Sakr, M., & Wilson, L. (2005). Best evidence topic report. Aspirin and the
risk of intracranial complications following head injury. Emergency
Medicine Journal, 22(12), 891–892. PubMed ID: 16299207 doi:
10.1136/emj.2005.031740
Taioli, E. (2007). Use of permitted drugs in Italian professional soccer
players. British Journal of Sports Medicine, 41(7), 439–441.
Tsitsimpikou, C., Jamurtas, T., Duncan-Fitch, K., Papalexis, P., &
Tsarouhas, K. (2009). Medication use by athletes during Athens
2004 Paralympic games. British Journal of Sports Medicine,
43(13), 1062–1066. PubMed ID: 19850571 doi:10.1136/bjsm.2009.
062521
Twist, C., Highton, J., Waldron, M., Edwards, E., Austin, D., & Gabbett, T.
(2014). Movement demands of elite rugby league players during
Australian National Rugby League and European Super League
matches. International Journal of Sports Physiology and Performance,
9(6), 925–930. PubMed ID: 24589426 doi:10.1123/ijspp.2013-0270
Twist, C., Waldron, M., Highton, J., Burt, D., & Daniels, M. (2012).
Neuromuscular, biochemical and perceptual post-match fatigue in
professional rugby league forwards and backs. Journal of Sports
Sciences, 30(4), 359–367. PubMed ID: 22176201 doi:10.1080/
02640414.2011.640707
United Kingdom Government Home Office. (2020, June). Cannabis,
CBD and other cannabinoids: Drug liscencing factsheet. UK Licens-
ing. https://www.gov.uk/government/publications/cannabis-cbd-and-
other-cannabinoids-drug-licensing-factsheet
van de Donk, T., Niesters, M., Kowal, M.A., Olofsen, E., Dahan, A., & van
Velzen, M. (2019). An experimental randomized study on analgesic
effects of pharmaceutical-grade cannabis in chronic pain patients
with fibromyalgia. Pain, 160(4), 860–869. doi:10.1097/j.pain.
0000000000001464
Walder, B., Tramer, M.R., & Blois, R. (2001). The effects of two
single doses of tramadol on sleep: A randomized, cross-over trial in
healthy volunteers. European Journal of Anaesthesiology, 18(1), 36–
42. PubMed ID: 11270008 doi:10.1097/00003643-200101000-00006
Xiong, W., Cui, T., Cheng, K., Yang, F., Chen, S.R., Willenbring, D., :::
Zhang, L. (2012). Cannabinoids suppress inflammatory and neuro-
pathic pain by targeting alpha3 glycine receptors. Journal of Experi-
mental Medicine, 209(6), 1121–1134. PubMed ID: 22585736 doi:
10.1084/jem.20120242
IJSNEM Vol. 30, No. 5, 2020
CBD Use in Professional Rugby 321
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
Appendix: Cannabidiol survey
322 IJSNEM Vol. 30, No. 5, 2020
Unauthenticated | Downloaded 10/14/20 08:35 AM UTC
