Journal Title (Medline/Pubmed accepted abbreviation): Med Sci Sports Exerc
Year: 2010 Epub ahead of print
Summary of Background and Research Design
Background: Exercise of sufficient intensity and duration can result in skeletal muscle damage. This is particularly true with exercise that includes unaccustomed lengthening type actions (eccentric actions) due to, in part, the greater force being exerted within the muscle with this type of movement. The greater force is believed to contribute to strain on the involved structures leading to functional impairment. Chemical changes associated with inflammatory as well as reactive oxygen/nitrogen species (RONS) have been implicated in both the initiation and progression of muscle fiber injury. Nutritional and nutraceutical substances have been purported to have antioxidant effects as well as some anti-inflammatory effects. Previous results demonstrated that a fruit, berry, and vegetable blended concentrate (FVC) supplemented for 2 weeks prior to aerobic exercise attenuated oxidative stress in both men and women with similar effects as a combined antioxidant (vitamins A and C).
Hypothesis:The FVC contains modest amounts of flavanoids, anthocyanins, and antioxidants and was hypothesized to reduce the loss of muscle function, muscle soreness, and oxidative stress in response to acute eccentric exercise (EE)
Subjects:Forty-one apparently healthy (age, 18 to 35 yr) subjects participated in the study; there were no statistical differences at baseline between the 2 treatment groups for mean age, weight, height, body mass index, percentage of body fat, or blood pressure
Experimental design: Double-blind, randomized, controlled
Treatments and protocol: Subjects were randomized to either placebo (P) or FVC treatment. They received capsules for 28 days (6 per day) before the EE and for the next 4 days. All subjects reported to the laboratory 4 weeks after initial evaluation following an overnight fast (>= 10 hours) and not having exercised strenuously for >= 2 days. Subjects completed 4 sets of 12 repetitions of eccentric elbow flexion with their nondominant arm at an angular velocity of 20°/sec with a 60-sec rest between sets, during which the investigator returned the lever arm to the initial flexed position. Range of motion (ROM) was set to 100° of flexion. Blood, muscle soreness (MS) ratings, ROM, and maximal isometric force (MIF) of the elbow flexors were obtained before, immediately after, and at 2, 6, 24, 48, 72 hours after exercise. Plasma was analyzed for creatine kinase (CK), lipid hydroperoxides (LOOH), malondialdehyde (MDA) and protein carbonyls (PC). Glutathione ratio was determined from whole blood extracts.
Summary of research findings:
- MS, ROM, MIF and plasma CK demonstrated significant time effects independent of treatment.
- MS and plasma CK increased over time while ROM and MIF decreased over time.
- There was a significant time and time by treatment effect for plasma PC and MDA. PC and MDA increased over time in the P group (P < .01) but were not significantly altered in the FVC treated group at any time.
- No significant changes were noted in LOOH.
- The glutathione ratio was elevated immediately after exercise in both groups (P < .01) and elevated 6 hours after exercise in the P vs FVC groups (P < .05).
Interpretation of findings/Key practice applications:
This study reports that 4 weeks of pretreatment with a FVC can attenuate blood oxidative stress markers induced by EE but had no significant effect on the functional changes related to pain and muscle damage. Although this study indicated that FVC acted as an effective antioxidant by attenuating the increase in several biomarkers of oxidative stress within the blood, it suggests that the primary mechanism for muscle force loss, MS, and membrane integrity damage is unrelated to blood markers of oxidative stress with EE. However, it is unclear how adequately blood markers of oxidative stress reflect what is happening within the muscles. Additionally, subsequent inflammatory-mediated factors may have contributed to the observed changes in both groups, although these factors were not assessed in this study. In other studies, antioxidant pretreatment was ineffective in preventing skeletal muscle contractile force loss, despite showing efficacy at reducing oxidative stress. Therefore, the authors speculate that blood oxidative stress is not a good indicator of muscle damage and force declines. The authors further recommend that supplementation of nutritional antioxidants not be encouraged as a means to prevent muscle damage because there have been minimal functional improvements with such treatment.