The Effects of Cannabidiol Oil on Noninvasive Measures of Muscle Damage in Men

Kristen C. Cochrane-Snyman; Candelaria Cruz; Jacobo Morales; Michael Coles

Disclosures

Med Sci Sports Exerc. 2021;53(7):1460-1472. 

In This Article

Methods

Participants

The study protocol was reviewed and approved by the University Institutional Review Board for human subject research before any recruitment or testing. Thirteen untrained men (mean ± SD age, 21 ± 2.73 yr, body mass, 78.63 ± 15.81 kg) volunteered to participate and completed both conditions of the study as part of a double-blind crossover design. A priori power analysis for a repeated-measures design indicated that a sample size of 13 would be sufficient to demonstrate a significant result with an α level of P < 0.05, power of 0.8, and a significant effect size of 0.2 or higher based on significant effect size estimates for changes in PT after EIMD.[37] An untrained individual was defined as those who had not participated in upper body resistance training for 6 months before participating in the study. The exercise protocol for inducing DOMS and the possible risks involved were thoroughly explained to all subjects. Subjects completed an informed consent document and a health history questionnaire, and were screened for musculoskeletal injuries involving the wrists, elbow, and shoulder joint as well as for any acute infections before participating in the study. Subjects were also screened for supplement and medication use and were excluded from the study if they consumed any substances that could confound the effects of the CBD supplement. Subjects were also asked to avoid using any other therapeutic modality (massage, ice compression, NSAIDs, etc.) and upper-body exercise during the course of the study, as these could have affected the quality of data collected.

Individuals were excluded from participation if they 1) had current and/or history of any musculoskeletal diseases or conditions affecting the upper body; 2) had a body mass index exceeding 30 kg·m−2; 3) failed the urinary drug screening for traces of THC at initial screening or any point during the duration of the study (Narcotest THC (ID Pharma, Paris, France)); 4) were consuming a regular antioxidant supplement; 5) had contraindications, allergy, or sensitivity to the active ingredient in the study supplement under investigation; 6) had any self-reported significant illness or condition that could be expected to interfere with the study parameters or study conduct, or put the subject at significant risk (e.g., an abnormal ECG, bleeding disorder, high blood pressure, anemia, decreased blood clotting ability, heart disease, anxiety, history of syncope or dizziness, or history of myocardial infarction; 7) had acute conditions known to affect inflammation markers' levels (acute infection, were taking antibiotics, acute postsurgical states, or recent severe trauma); 8) had used creatine within 9 wk before screening; 9) had participated in any drug or medical trial within 30 d leading into study participation; 10) were unable to complete a 3-d food log; 11) were unable to understand English or Spanish instructions; and 12) were allergic to vegetable/canola oil (placebo).

Experimental Design

This study was a double-blinded, placebo-controlled, crossover design, and took place in the University's Human Performance Lab (Figure 1). All experimental sessions occurred at the same time of day ± 30 min. On visit 1, subjects were randomly assigned to one of the two experimental groups, 150 mg (CBD) or placebo (PLC), based on their assigned subject number and corresponding randomization code. Subjects were familiarized with the supplement administration instructions before any testing or measurements. Subjects were also instructed on how to complete a 3-d food recall log to be analyzed using myfitnesspal.com calorie analysis and were familiarized with the isokinetic dynamometer (Biodex, Corp., Shirley NY) and the Borg 6–20 RPE scale using standardized instructions.[38] During the dynamometer familiarization, subjects were asked to give different levels of effort (0%–100% maximal voluntary isometric contraction (MVIC)) and to assess their RPE to help establish anchoring cues for the RPE scale.[38] The subjects' heights (in meters) were measured using a stadiometer (Novel Products Inc., Rockton, IL), and weight and fat percentages were measured via bioelectrical impedance spectrometry (Tanita Corp., Tokyo, Japan). On all experimental visits, subjects completed a THC urinary screening test (Narcotest THC (ID Pharma)). Upon completion of the aforementioned test, the following variables were measured during the first experimental visit for each condition (CBD, PLC): resting blood pressure, perceived soreness using a visual analog scale, arm circumference of the randomized test limb (counterbalanced across conditions) using a Gulick tape measure (Mabis Healthcare, Waukegan, IL), hanging JA using a goniometer (Smith and Nephew Rolyan Inc., Menomonee Falls, WI), and PT using a calibrated isokinetic dynamometer (Biodex, Corp.). Subjects then performed a warm-up of five submaximal muscle actions involving the elbow flexors at 50% of maximal effort before conducting measurement of MVIC PT. All measurements (perceived soreness, JA, arm circumference, RPE, and PT) were taken immediately before ECC (PRE), 2 min after ECC (POST), and at 24 (visit 3), 48 (visit 4), and 72 h (visit 5) after muscle-damaging exercise protocol. The ECC protocol occurred only on the first visit of each testing cycle.

Figure 1.

Study design.

After POST measures, participants were given their blinded capsule canisters containing either experimental supplement (non-THC CBD) or PLC (vegetable oil). The primary investigator and all researchers involved were blinded to the contents of the canisters. Randomization and blinding code were created and maintained by an outside agent. The experimental group CBD consumed two doses of 75 mg (three capsules per dose; 150 mg total) of CBD orally per day separated by 8 h. Participants were instructed to take their first dose within 1 h after completing visit 2, and subsequent dosages for CBD or PLC were consumed 8 ± 1 h after the initial dosage on visit 2, visit 3, and visit 4. The PLC groups received an identical dosage (three capsules per dose) and administration of a capsule filled with non-CBD containing vegetable oil. Vegetable oil, without traces of flaxseed n-3 oil was selected as the PLC because it contained no known antioxidants or other properties that may affect anti-inflammatory pathways. Although flaxseed-rich vegetable oil has previously been shown to affect markers of inflammation,[39] specifically those with high levels of n-3 fatty acid derivatives, the vegetable oil selected as the placebo was sunflower and soybean based with no effects on inflammatory pathways in the quantities administered. On visit 5, participants returned to the laboratory and completed all POST ECC protocol measures but did not receive another dose of the supplement or placebo. After a washout period of 2 wk, participants returned to undergo either the CBD or PLC condition, whichever was not administered during the initial visits. During the crossover, the subject performed the same exercise protocol and series of measurements as in the initial visits, but all exercises and measures were performed on the contralateral arm.

Supplementation

CBD capsules: CBD (150 mg) were divided into two separate 75-mg doses to be separated by 8 h. Participants consumed three 25-mg CBD gel capsules (Green Roads, Davie, FL) for a total dose of 75 mg per 8 h. Previous research has shown efficacy for low doses of 1.5 mg·kg−1 body mass up to 10 mg·kg−1 [40] of CBD for its effects on markers of inflammation. The dosage in the current study was selected to be within this range (2.0 mg·kg−1 average), as limited information on the use of this supplement for this purpose in human subjects is available. The time course for time to maximum concentration has been reported to be between 1.5 and 3 h for CBD dosages of 150–300 mg, and terminal-half life may last as long as 17 h after supplementation.[41,42] Therefore, the absolute dose administered after each visit (150 mg) fell within this range and was expected to present in circulation up until the next testing and supplement administration session.[41,42] The hemp-derived CBD isolate used in the present study was independently shown (Kaycha Labs, Davie, FL) to have 4.097% CBD and 4.108% total cannabinoids (0% THC) in the sample tested with 25 mg of CBD per capsule. Placebo capsules were gelatin capsules filled with 25 mg of 100% certified organic vegetable oil (Spectrum Naturals, Lake Success, NY) and allocated in the same quantities (six capsules per day) as the CBD condition. Placebo capsules looked identical in appearance to the CBD capsules. Vegetable oil was selected as a safe PLC, which would not significantly affect inflammation in the quantities provided (75 mg per dose), yet appear identical in appearance and texture to the active, CBD capsules.[43] All supplement and placebo capsules were distributed in blinded containers with predetermined coding set by the independent party responsible for controlling the blind. Neither researcher nor participant knew the contents of each capsule canister. To facilitate allocation concealment, the independent party who formulated the blind maintained the blind record and black canisters, which hid the contents from the experimenters during assignment. All capsules and canisters were identical in appearance. Each black canister, filled with either CBD or PLC, as designated by the blinder, was given a 1 or 2 designation, and each subject number was randomly assigned 1 or 2 as their starting condition. Subject numbers were assigned as subjects were enrolled, and therefore, there was no bias related to allocation of condition assignment. Each participant only received the capsules associated with each visit; therefore, three separate canisters were distributed to each participant during condition 1 and condition 2 of the study. The participants did not take any of the study product or placebo during the washout period. As the terminal half-life for 250–300 mg of CBD has been shown to be 14–17 h,[41,42] the 2-wk washout was deemed sufficient to remove any trace of active supplement before completing the crossover. Compliance was assessed by having each participant log the timing of their dosages and returning the study canister at each subsequent visit. Participants who failed to consume 80% of the study drug within the 16-h supplementation window was considered not in compliance. In addition, THC urinary screenings were completed during all experimental visits to ensure participants were not consuming substances, which may confound the study results.

ECC Protocol

To induce soreness, subjects performed 6 sets of 10 maximal ECC isokinetic muscle contractions of the elbow flexors at 30°·s−1 using a Biodex dynamometer (Biodex, Corp.). Subjects performed the first round of experimental exercise visits using their dominant arm (determined by handedness) and nondominant arm during the crossover portion of the study. The exercise was performed with the hand in a neutral position, and subjects were placed in a sitting position on the Biodex dynamometer with the fulcrum of the Biodex lever arm aligned on the lateral size of the subject's elbow. Subjects began each eccentric muscle action at an angle of 50° at the elbow and were instructed to give a maximal effort while resisting the lever arm until they reached an extended angle of just under 180°. Subjects were then assisted through the concentric portion of the movement range to ensure significant energy was not expended to return to the 50° starting position. To ensure maximal effort, the same tester gave verbal encouragement and subjects could view their torque production using the Biodex system monitor. One minute of rest was given between each set, and before measurements that were taken after exercise, 2 min of rest was given.[9]

Instrumentation

Muscle soreness was measured using a 10-cm visual analog scale adopted from Bobbert et al.,[44] which included verbal descriptions of pain. To indicate the level of soreness felt when the elbow and forearm were extended, the subject marked the scale corresponding to their pain. Perceived soreness was then measured in centimeters using a ruler across the scale. Arm circumference was measured at the midbelly of the bicep. The measurement was taken with the arm horizontally abducted and the forearm extended.[9] The arm utilized was randomized across both groups, with the starting arm determined by handedness based on throwing preference. Hanging JA between the forearm and arm was measured using a goniometer (Smith and Nephew Rolyan Inc., Menomonee Falls, WI). For each measurement, the axis of rotation of the elbow joint was aligned with the axis of the goniometer. The proximal arm of the goniometer was aligned with the acromion process of the scapula, and the distal arm was aligned with the styloid process of the ulna.[9] MVIC PT was measured on a Biodex dynamometer (Biodex, Corp.). The Biodex has been shown to be reliable and valid for the measurement of MVIC in both trained and untrained populations.[45,46] A random subsample of untrained subjects (n = 8) was used to calculate the coefficient of variation for MVIC rep 1 versus MVIC rep 2 and was found to have ranged from 0% to 8.0%, with most subjects ranging between 0% and 3.0%, which represents a good coefficient of variation precision of measurement value. Subjects performed a warm-up of five submaximal muscle actions at 50% of maximal effort before conducting measurement of MVIC PT. After warming up, subjects performed three, 6-s MVICs of the elbow flexors seated, with the hand in a neutral position. As with the methods of Jenkins et al.,[9] the angle between the arm and forearm was set at 115° and tension was released from the lever arm before initiation of MVICs. Subjects were instructed to give maximal efforts and contract their arm as hard and fast as possible. Each set was separated by 2 min of rest. The highest torque measurement out of the 3 was used for analysis.[9] RPE was measured immediately after each 6-s MVIC, as RPE may be used as an indicator of maximal effort.[38] The same investigator measured each dependent variable for each subject to maintain intersubject reliability.

Statistical Analyses

Five separate two-way repeated-measures ANOVA tests (condition [CBD vs PLC] × time [PRE vs POST vs 24 h vs 48 h vs 72 h]) were used to analyze perceived soreness, JA, arm circumference, RPE, and PT. Follow-up one-way repeated-measures ANOVA was used to decompose significant interactions and main effects for time, whereas one-way between-factor ANOVA was used for condition. Significant one-way ANOVA was followed by pairwise comparisons using Sidak–Bonferonni error correction for multiple comparisons. Partial η squared ( ) and Cohen's d effect sizes were calculated for each ANOVA and pairwise comparison, respectively, and presented for all significant results. The Mauchly sphericity test was used to test assumptions of homogeneity of variance. If this was violated, the Greenhouse–Geisser value was used to adjust degrees of freedom to increase the critical value of the F ratio. Normality was assessed using histogram plots with a normal distribution curve of best fit and inspection of QQ residual plots. All statistical analyses were completed using SPSS (Version 25; IBM, Armonk, NY) using an a priori α level of 0.05 to determine the threshold for significance.

processing....