Findings from the present investigation indicate that MSM supplementation in healthy, moderately exercise-trained men may favorably influence selected markers of exercise recovery. This effect appeared to be greater with a daily dosage of 3.0 grams of MSM than a daily dosage of 1.5 grams. Although this study included a very small sample of subjects, which makes it difficult to confidently discuss the overall meaning of our findings, our data provide initial evidence that MSM may have efficacy in regards to influencing certain markers of exercise recovery. Further studies are needed, inclusive of a larger sample size (~15-20 subjects per group, if not larger), a placebo control group, and additional markers of exercise recovery and performance. In such future studies, analysis of blood MSM concentrations pre and post intervention, as opposed to simple capsule counts as done in the present design, would prove valuable as an indication of supplement compliance (as well as to provide information related to supplement absorption, etc.).
This is the first trial to note an impact of MSM on blood TEAC, suggesting increased antioxidant activity. This marker, like other “global” markers of antioxidant status (e.g., ORAC, FRAP, TRAP) provides a general measure of the sum total of antioxidants within blood and other tissues. While the observed increase in TEAC may indeed have relevance, future studies focused on MSM should ideally include additional markers of antioxidant activity, as well as markers of oxidative stress.
While TEAC was noted to be higher post-exercise with MSM, we did not observe the same finding for blood glutathione, which appeared unaffected by exercise or supplementation with MSM. Our results for glutathione oppose those of DiSilvestro et al. who noted an increase of 78% in liver glutathione when studying male mice ingesting MSM in drinking water for 5 weeks. The present study, however, was quite different in design. For example, it involved human intake of MSM, glutathione measured in whole blood, and the inclusion of a physical stressor (i.e., 18 sets of knee extension exercise). These differences may be responsible for the discrepancies in findings.
As we believe that TEAC does in fact represent an increase in antioxidant defense (independent of glutathione), it is possible that this increase may have attenuated the commonly observed rise in ROS during and following exercise, resulting in attenuation of exercise-induced oxidative stress. While oxidative stress biomarkers were not included in the present design, extant literature indicates a potential for this effect. For example, we know of at least one animal study and one human study that has focused on the role of MSM to attenuate exercise-induced oxidative stress. Marañon and colleagues studied competitive jumping horses receiving either a standard control diet, a MSM diet (8 mg/kg MSM), or a combined MSM + vitamin C diet (8 mg/kg MSM + 5 mg/kg vitamin C) for a period leading up to competition. Blood was collected before and within 15 minutes following competition and analyzed for a variety of oxidative stress markers. The competitive exercise resulted in noted increases in lipid peroxidation, nitric oxide metabolites, and carbon monoxide, with decreases in reduced glutathione and antioxidant enzyme activity. Supplementation with MSM significantly attenuated the observed changes due to competition, with a more pronounced effect noted with MSM + vitamin C treatment. Moreover, in a recently published human study, MSM supplementation at 50 mg/kg was provided to untrained healthy men for 10 days prior to performing a 14 km run. Blood was collected before and at times through 48 hours of exercise recovery and analyzed for lipid, protein, and glutathione oxidation. As expected, acute exercise resulted in an increase in oxidative stress; however, this increase was blunted significantly with MSM supplementation as compared to placebo. Collectively, the results of Marañon et al. and Nakhostin-Roohi et al. provide initial evidence that prophylactic intake of MSM prior to exercise may alleviate the oxidative stress that is often observed following strenuous bouts of exercise, in particular in those who are not accustomed to the stress of exercise. Although ROS have been linked to potential problems in muscle integrity and the generation of muscle force, the above studies did not include any measure of physical performance in the design. This is certainly a limitation and such measures should be considered in future studies investigating the impact of MSM on exercise recovery.
Aside from measures of antioxidant status (TEAC and glutathione), we included the measure of homocysteine in the current design. Homocysteine is a non-protein amino acid, with elevated levels in circulation thought to be associated with an increased risk of cardiovascular disease; although recent evidence questions this association. A study by Kim et al. reported a statistically significant lowering of homocysteine (8.0 to 7.2 μmol·L-1) in a sample of knee osteoarthritis patients following intake of MSM at a dosage of 6 grams per day for 12 weeks. Data from the present investigation somewhat corroborate the work of Kim and colleagues, as we noted a lowering of homocysteine during the post-exercise period after subjects were supplemented with MSM for four weeks (Figure3). The mechanism of action of this effect may be linked to methyl group donation by MSM, in much the same way as done by B-vitamins.
From a practical standpoint, we measured muscle performance by calculating total work performed during the final 3 sets of knee extension exercise. Despite some positive findings for our non-exercise performance measures, we failed to note any difference in exercise performance between pre and post intervention. In fact, values were actually lower following MSM supplementation as compared to before supplementation. We have no explanation for these findings other than recognizing our small sample size and the potential for day-to-day variance in knee extension “muscle endurance” performance, as has been noted for isokinetic testing. Also noteworthy, motivation is paramount when asking subjects to perform repetitions to exhaustion.
In retrospect we believe that our chosen protocol may not have been ideal to discern performance differences between groups and across time. Although subjects performed a total of 18 sets of knee extension exercise, the first 15 sets were standardized in terms of repetition number. Hence, subjects were only provided a total of 3 performance sets (16–18) to generate usable data for performance comparison. Future work may include a different exercise protocol, with the possible addition of isometric and dynamic force, as well as power data as done previously, in addition to actual volume load (reps x load). This would provide for a more complete assessment of muscle performance—as well as greater potential for observed differences in muscle soreness and oxidative stress related parameters. Moreover, the “damaging” exercise protocol may be altered to include a more robust model for inducing damage (e.g., pure eccentric loading using 1-RM values that are far greater than those used in the present design).
In addition to performance, we used two distinct questionnaires to determine the extent of either muscle soreness or fatigue, before and following exercise, both pre and post intervention. Although preliminary, MSM did provide some evidence of effect at attenuating both muscle soreness and fatigue (Figures1 and2, respectively). As with other measures, additional larger scale studies are needed to corroborate these findings. If future work agrees with these initial findings, MSM may serve a useful purpose in enhancing post-exercise recovery.