Journal Title (Medline/Pubmed accepted abbreviation): J. Sports Sci. Med.
Summary of background and research design
Background: Many argue that the amount of stimulation that the immune system experiences during moderate exercise is beneficial for immune function. However, most agree that too much exercise (duration and/or intensity) can be harmful to the immune system. Phlebodium decumanum (PD) is a type of fern that grows in parts of Central America that may contain active ingredients that regulate immune function.
Hypothesis: PD will attenuate immune parameters such as inflammation caused by both aerobic and high intensity anaerobic exercise.
Subjects: 31 subjects, age ~20-25 y
Experimental design: randomized, double-blind, placebo-controlled
Treatments:Experimental: 400 mg capsules containing 250 mg frond water-soluble extract and 150 mg pulverized PD root; control: 400 mg capsules of brewer’s yeast. Two capsules were taken 3 times per day to yield 6 capsules per day.
Protocol:The subjects attended tennis training 3 times/wk for 4 wks. Training included 1) practicing tennis strokes, 2) strength training with bench press, lat pull downs, and shoulder dumbbell press at an intensity of 55-60% of their 1 repetition maximum, and 3) interval training at maximal intensity, running a total of 160 m. Blood samples were acquired and analyzed for immune parameters (ex. TNFα and IL-6) before and after the 4 wk training session, though the authors did not specify if the blood was drawn fasted, after exercise, etc.
Summary of research findings
- IL-6 and TNF-α both decreased after the supplementation period for the PD group, while the control group’s levels of these parameters did not change.
- IL-1 receptor antagonist and soluble TNF-α receptor II were significantly increased with supplementation, while these metrics decreased for the control group. However, as mentioned in the Limitations section below, the statistical methods were questionable.
Interpretation of findings/Key practice applications
Root from PD may reduce levels of inflammation, even with moderate physical activity.
This article had some significant limitations. There were seemingly large differences between some of their metrics between the pre-test PD group and pre-test control group, which will greatly affect their outcome. The authors used t-tests to evaluate differences between pre- and post-tests, not an ANCOVA that would be able to take into account existing differences between groups at baseline. The authors also did an extensive evaluation of physical assessment parameters including performance on bench press, interval training, and tennis skills, though the results these tests were not mentioned in the results or discussion sections of the paper.