Abstract and Introduction
Abstract
No previous study has investigated the applications of isolated cannabidiol (CBD) as a recovery aid in untrained human subjects after a bout of exercise-induced muscle damage.
Purpose: This study aimed to investigate the effect of CBD oil on perceived muscle soreness, inflammation, and strength performance after eccentric exercise (ECC) of the elbow flexors.
Methods: Thirteen untrained men (mean ± SD age, 21.85 ± 2.73 yr) performed 6 sets of 10 maximal ECC isokinetic muscle actions of the elbow flexors as part of a double-blind crossover design. Noninvasive (perceived soreness, arm circumference, hanging joint angle (JA), and peak torque (PT)) measures were taken before and after ECC, and 24, 48, and 72 h after ECC. All subjects completed both the supplement (CBD: 150 mg POST, 24 h, 48 h) and placebo (PLC: POST, 24 h, 48 h) condition separated by 2 wk. Four separate two-way repeated-measures ANOVA (condition [CBD vs PLC] × time [PRE vs POST vs 24 h vs 48 h vs 72 h]) were used to analyze perceived soreness, arm circumference, JA, and PT. One-way repeated-measures ANOVA were used to decompose significant interactions and main effects.
Results: There was no condition–time interaction or main effect of condition (P > 0.05) for perceived soreness, arm circumference, JA, or PT. There were main effects for time for perceived soreness (P = 0.000,
= 0.71) and JA (P = 0.006,
= 0.35).
Conclusions: The current dose of 150 mg CBD oil at POST, 24 h, and 48 h had no effect on noninvasive markers of muscle damage in the upper extremity. At the current dose and schedule, CBD oil may not be beneficial for untrained men as a recovery aid after exercise-induced muscle damage.
Introduction
Cannabidiol (CBD) is one of the most studied components of the Cannabis sativa plant, but unlike Δ9-tetrahydrocannabinol (THC), CBD is a nonintoxicating compound[1] that was removed from the banned substance list by the World Anti-doping agency in 2018. Although CBD has been a known derivative of C. sativa since 1940, it has recently gained popularity as a pharmaceutical intervention for epilepsy,[2] arthritis, and neuroinflammation.[3–5] In addition to its applications for clinical conditions, the interest in CBD has exponentially risen among athletes and nonathletes. For example, in a recent survey of 301 athletes’ cannabis use and behaviors, 45% reported using CBD, with the majority presenting as novice (>3 yr) users.[6] CBD products are now widely available in pharmacies, nutrition specialty, and retail stores despite limited data supporting their efficacy for nonclinical conditions, including markers of sports performance and injury recovery.
One common condition associated with a novel or high-volume exercise stimuli is delayed-onset muscle soreness (DOMS). DOMS is a sensation of discomfort often associated with inflammation that is typically felt within 24–72 h after bouts of unaccustomed exercise or high volumes of intense eccentric exercise (ECC).[7,8] Although some degree of muscle damage may be induced from any form of exercise, previous research has indicated that ECC is the most effective method of inducing damage, especially when applied to the elbow flexors.[7,9,10] The associated symptoms of DOMS, such as soreness, muscle stiffness, aching pain, tenderness to palpation, and swelling, usually subside 5–7 d after exercise.[8,11,12] One source of these symptoms is acute inflammation, which also been shown to occur as a response to the trauma seen in muscle after performing ECC.[8,13–15] ECC has been shown to result in muscle damage, this acute inflammation, and DOMS.[13,14] Thus, ECC is a well-accepted modality for investigating exercise-induced muscle damage (EIMD) and the efficacy of interventions to mitigate acute inflammation and DOMS associated with EIMD.[9,16,17]
The most common way to measure inflammation is through muscle biopsies and blood draws. However, these techniques in themselves can impose further inflammation as they cause tissue damage through the insertion of the needle.[18] Previous studies[9,18,19] have used noninvasive measures of muscle damage and inflammation such as visual pain scales,[20,21] limb circumference, joint angles (JA),[19] and changes in peak torque (PT) to determine the degree of pain, swelling, and performance declines caused by ECC exercise. These measures, when paired with blood serum biomarkers, such as creatine kinase, the inflammatory interleukins (IL-1β, IL-6), or C-reactive protein have shown to be highly correlated and as such effective analogs for EIMD.[9,20,21] Although invasive measures are the most popular method, noninvasive measures are suitable, are more affordable to measure in and outside of a laboratory setting, and do not impose further damage to tissues. Thus, the use of noninvasive measures of muscle damage does provide valuable information regarding the incidence of EIMD and DOMS and may be monitored for changes over time to determine the efficacy of a recovery intervention.
DOMS and associated inflammation have been shown to reduce athletic performance, which has fueled the development of preventable techniques in an attempt to attenuate these potential negative outcomes of unaccustomed exercise.[22] Previous studies[23–26] utilizing treatments such as massage and nonsteroidal anti-inflammatory drugs (NSAIDs) for the treatment of EIMD or DOMS have produced equivocal results. Although the use of NSAIDs and massage are the most common treatments, each may vary in effectiveness in their ability to alleviate pain, soreness, and inflammation as a result of EIMD. Inflammation plays a key role in the muscle protein synthesis pathway, but it may also result in acute performance declines that are perceived negatively by most athletes and coaches.[9,23,27] Thus, there is a need to investigate additional methods or supplement applications for the treatment of acute muscle damage after bouts of exercise.
CBD is becoming an increasingly popular medicinal treatment for pain and inflammation. CBD is said to work by binding to specific receptors (Vanilloid trpv1 and CB2R).[3,28–30] For example, CBD has been shown to be a receptor agonist for the CB2R receptor, which is located on cells associated with the immune system, cardiovascular system, and gastrointestinal tract, and plays a role in inflammatory immune responses. In addition, evidence is emerging that CBD interacts with the 5-HT1A serotonin receptor, which is a target for antidepressant medications, and has some antioxidant properties.[31] It has been used to treat various medical conditions such as arthritis, multiple sclerosis, and neuroinflammation.[3–5] For example, Malfait et al.[5] found that oral administration of CBD was able to suppress the progression of arthritis because it presented immunosuppressive and anti-inflammatory properties. In addition, CBD has been shown to modulate inflammatory processes and affect markers commonly associated with EIMD.[32] For example, CBD has been shown to reduce IL-1β, IL-6 as well as tumor necrosis factor (TNF-α), another biomarker for EIMD,[33–35] which may have applications for neuromuscular inflammation related to DOMS. Although CBD has been shown to have anti-inflammatory and antihyperalgesic properties, there has been limited research on its effect after exercise.[17,36]
The mechanisms underlying exercise-induced muscle soreness and inflammation have been studied for decades; however, limited studies have investigated the effects of a novel application for CBD and its effects on perceived muscle soreness and inflammation after exercise.[17,36] To the author’s knowledge, at the time of this study’s undertaking, no previous study had investigated the effect of isolated CBD oil on EIMD in humans. Therefore, the purpose of this study was to investigate the effects of CBD on perceived muscle soreness, inflammation, and acute performance after bouts of ECC. In accordance with the previous anti-inflammatory applications for CBD oil, it was hypothesized that CBD may reduce perceived muscle soreness and inflammation, and enhance performance recovery.