Journal Title (Medline/Pubmed accepted abbreviation): Med Sci Sports Exerc
Page numbers: 1544-1551
Background: Unaccustomed intensive exercise leads to muscle damage of which the exact mechanisms are not well understood. Most likely, the initial damage is from mechanical forces to the muscle fibers and oxidative stress from reactive oxygen species (ROS) and nitric oxide (NO). Later damage may occur from inflammation, which also releases ROS and NO. Studies evaluating antioxidant supplementation for ameliorating muscle damage have reported conflicting evidence. However, fruit-derived phytochemicals that have both antioxidant and anti-inflammatory properties show promising activity.
Hypothesis: Supplementation with Montmorency cherry juice concentrate will attenuate muscle damage from intensive resistance exercise.
Subjects: Ten healthy males who regularly performed resistance training and competed in high-intensity intermittent sports participated in this study. Mean age, weight, height, and single leg 1-repetition maximum (1RM) were 27.8 ± 1.6 years, 81.3 ± 4.3 kg, 1.76 ± 0.03 m, and 73 ± 4 kg, respectively.
Experimental design: Cross-over, double-blind
Treatments and protocol: Single-leg knee extension 1RMs were determined for each volunteer, followed 1 week later by 2 single-leg knee extension sessions 2 weeks apart. At 24 and 48 hours after each session, the maximal voluntary contraction force (MVC) was determined. Volunteers consumed 30 mL of either the cherry juice concentrate (CA) or an isoenergetic fruit concentrate (placebo) twice daily for 10 days. Exercise testing was on Day 8 of each session, with a different leg for each session. A food dairy was kept and diets were repeated for the second session. Pressure pain threshold as an index of muscle soreness was assessed at baseline, immediately following, and 24 and 48 hours after the 1RM determination. Blood samples were obtained at baseline and 10 minutes, 24 hours, and 48 hours following the 1RM for creatine kinase (CK), high-sensitivity C-reactive protein (hsCRP), total nitrotyrosine and antioxidant capacity, and protein carbonyls (PC).
Knee strength recovery was faster during the consumption of Montmorency cherry juice compared with a placebo. In addition, serum PC values were lower in the CA trials, which indicate less oxidative damage. However, muscle soreness and CK activity were not affected. The results suggest that the anti-inflammatory and antioxidative properties of the cherry juice contributed to the recovery and not any protective effect on the muscle damage itself. Although hsCRP was not elevated, it is possible that the smaller muscle mass involved in this study could not increase this systemic marker. Limitations of this study include the subjective nature of measuring muscle soreness, and the rate of pressure development was not controlled.