Montmorency cherry juice reduces muscle damage caused by intensive strength exercise

Journal Title (Medline/Pubmed accepted abbreviation): Med Sci Sports Exerc
Year: 2011
Volume: 43
Number: 8
Page numbers: 1544-1551
doi: 10.1249/MSS.0b013e31820e5adc

Summary of background and research design:

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).

Summary of research findings:
  • The MVC recovery was faster in the CA trial compared with the placebo trial (P = .04).
    • At 24 hours, levels returned to 90.9% of pre-exercise in CA trial and 84.9% in placebo trial.
    • At 48 hours, levels returned to 92.9% of pre-exercise in CA trial and 88.5% in placebo trial.
  • Pressure pain threshold was reduced from baseline at 24 and 48 hours in both groups without any statistically significant effect of trial or trial × time interaction for the overall muscle response.
  • Serum CK activity levels increased from baseline after exercising in both trials, but were not statistically different between trials at 24 and 48 hours.
    • Total CK activity and absolute increase tended to be higher in the CA trial vs the placebo trial (P interaction = .063).
  • PC content increased from baseline at 24 and 48 hours in both groups, with a significant effect of time (P = .034) and trial (P = .013; lower values in the CA trial).
  • No significant changes in hsCRP, total nitrotyrosine, and total antioxidant capacity were observed.

Interpretation of findings/Key practice applications:

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.

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