BACKGROUND: Oxidative stress and muscle damage occur during exhaustive bouts of 
exercise, and many runners report pain and soreness as major influences on 
changes or breaks in training regimens, creating a barrier to training 
persistence. Methylsulfonylmethane (MSM) is a sulfur-based nutritional 
supplement that is purported to have pain and inflammation-reducing effects. To 
investigate the effects of MSM in attenuating damage associated with physical 
exertion, this randomized, double-blind, placebo-controlled study evaluated the 
effects of MSM supplementation on exercise-induced pain, oxidative stress and 
muscle damage.
METHODS: Twenty-two healthy females (n = 17) and males (n = 5) (age 
33.7 ± 6.9 yrs.) were recruited from the 2014 Portland Half-Marathon registrant 
pool. Participants were randomized to take either MSM (OptiMSM®) (n = 11), or a 
placebo (n = 11) at 3 g/day for 21 days prior to the race and for two days after 
(23 total). Participants provided blood samples for measurement of markers of 
oxidative stress, and completed VAS surveys for pain approximately one month 
prior to the race (T0), and at 15 min (T1), 90 min (T2), 1 Day (T3), and 2 days 
(T4) after race finish. The primary outcome measure 8-hydroxy-2-deoxyguanine 
(8-OHdG) measured oxidative stress. Secondary outcomes included malondialdehyde 
(MDA) for oxidative stress, creatine kinase (CK) and lactate dehydrogenase (LDH) 
as measures of muscle damage, and muscle (MP) and joint pain (JP) recorded using 
a 100 mm Visual Analogue Scale (VAS). Data were analyzed using repeated and 
multivariate ANOVAs, and simple contrasts compared post-race time points to 
baseline, presented as mean (SD) or mean change (95% CI) where appropriate.
RESULTS: Running a half-marathon induced significant increases in all outcome 
measures (p < 0.001). From baseline, 8-OHdG increased significantly at T1 by 
1.53 ng/mL (0.86-2.20 ng/mL CI, p < 0.001) and T2 by 1.19 ng/mL (0.37-2.01 ng/mL 
CI, p < 0.01), and fell below baseline levels at T3 by -0.46 ng/mL (-1.18-0.26 
CI, p > 0.05) and T4 by -0.57 ng/mL (-1.27-0.13 CI, p > 0.05). MDA increased 
significantly at T1 by 7.3 μM (3.9-10.7 CI, p < 0.001). Muscle damage markers CK 
and LDH saw significant increases from baseline at all time-points (p < 0.01). 
Muscle and joint pain increased significantly from baseline at T1, T2, and T3 
(p < 0.01) and returned to baseline levels at T4. Time-by-treatment results did 
not reach statistical significance for any outcome measure, however, the MSM 
group saw clinically significant (Δ > 10 mm) reductions in both muscle and joint 
pain.
CONCLUSION: Participation in a half-marathon was associated with increased 
markers of oxidative stress, muscle damage, and pain. MSM supplementation was 
not associated with a decrease from pre-training levels of oxidative stress or 
muscle damage associated with an acute bout of exercise. MSM supplementation 
attenuated post-exercise muscle and joint pain at clinically, but not 
statistically significant levels.