Wednesday, July 6, 2011

Can Pomegranate Juice Improve Soccer Performance?

Pomegranates have been described as the new “super fruit”. Their juice contains high levels of polyphenols, which have powerful antioxidant effects. It is also high in vitamins A, C and E, high in folic acid and potassium. Drinking pomegranate juice has been linked to several health benefits including reduced risk of cancer, lowered blood pressure and improved blood cholesterol. Given the health benefits of pomegranate juice it seems likely to ask the question, will pomegranate juice improve exercise performance? For some time, scientists have suggested that polyphenols may aid in recovery from intense exercise. Researchers at the University of Texas recently completed a pair of studies designed to determine if pomegranate juice affects muscle strength and soreness during recovery from intense exercise. Their findings suggestthat the juice may have some small effect but they also raise several questions.

The two studies, funded by the POM Wonderful company (producers of PomX), focused on the recovery of muscle strength and soreness after intense, strenuous exercise. The design was a bit different than other supplement studies. Instead of providing the treatment only after exercise, the researchers gave the pomegranate juice well in advance of the exercise bout and continued through the recovery period.

In the first study, untrained subjects drank 500 ml (~2 cups) of either pomegranate juice or a placebo drink for five days prior to the intense exercise bout. They continued consuming the juice for the remainder of the experiment (four more days). On day five, baseline measurements of strength and soreness were measured. After baseline measurements, subjects performed a series of eccentric or lengthening contractions with the elbow flexor muscles (biceps muscle). This “negative rep” protocol is traditionally used as a high-intensity exercise bout to induce both muscle fatigue and delayed onset muscle soreness. Immediately after exercise and over the next four days, strength and soreness measurements were repeated.

Under both conditions, muscle force declined by about 30% immediately after exercise. The following day, these untrained subjects regained some strength and force steadily improved over the following days. The pomegranate juice had no effects on strength after exercise but did lead to small improvements on days two and three. As for soreness, discomfort was felt after exercise but pain peaked 24-48 hours later then subsided by day four. Pomegranate juice slightly reduced the level of muscle soreness immediately after exercise but did not affect delayed-onset soreness (days 1-4). Interestingly, blood markers of muscle damage were slightly elevated in the pomegranate juice trial.

In the second study, weight trained subjects drank 250 ml (~1 cup) of either pomegranate juice or a placebo drink twice daily for 15 days. Eight days into the experiment, baseline measurements were performed and the subjects performed the eccentric contraction protocol using both the elbow flexor and the knee extensor muscles (quadriceps). Strength and soreness were again measured after exercise and for the next seven days.

In these trained subjects, arm strength was reduced immediately after exercise by about 35% in the placebo condition and about 25% in the pomegranate juice condition, a statistically significant difference. Strength recovered over the next six days but was always slightly greater when the subjects drank the pomegranate juice. At two and three days post-exercise, pomegranate juice slightly reduced the perception soreness.

Leg strength was also reduced by about 20% under both conditions and slowly recovered over the next week. Soreness also followed the same pattern as the arm, described above. However, pomegranate juice had no effect on leg strength or soreness across the duration of the study.

The results of these two studies are somewhat confusing. On the one hand, they suggest that pomegranate juice may aid in the recovery of strength and soreness after intense exercise. This appears to be the case in both trained and untrained subjects. On the other hand, the effect seems to occur only in the arm muscles but not in the leg muscles. And, the effect is variable, being greater at different times in the trained and untrained subjects. Nevertheless, there may be some important benefits to drinking pomegranate juice.

Two key issues should be pointed out before players start on pomegranate juice regimen. First, the studies show that the effects on the arms were quite small and somewhat variable. Soreness was minimally affected. In fact, on a scale of 1-10 (with 10 being “unbearable soreness”), the pain perception was improved, at most from a 4 to a 3. Many feel that while this difference may be statistically significant, it is probably too small to be noticed by athletes during training or competition. Further, strength of the arm muscles was improved by, at most, 8-10%. Again, this is a fairly small improvement in performance. One could argue that in a sport where victory may be determined by inches, a 10% gain is meaningful. One could also argue that other factors such as diet and fitness level affect performance by a greater margin. Given this, it is too early to say that the observed in the two studies would translate into noticeable improvements on the pitch.

Second, pomegranate juice did not affect recovery of the leg muscles. This is an important point. Soccer is a sport played primarily with the legs. Thus, it is quite possible that drinking the juice would have no beneficial effects on soccer skill or fitness. In other sports, say tennis or swimming where the arms are used extensively, there may be a performance advantage. Again, improvements in training or match performance are questionable.

Third, the authors of the studies suggest that there is a clear need for more research. These are the first two studies looking at pomegranate juice and exercise performance. Questions remain about the effects on other aspects and types of exercises. For example, would fitness or skill, as opposed to strength be improved? Given the lack of research, it is difficult to make firm conclusions about pomegranate juice as a supplement.

Back to the title of this post, can pomegranate juice improve soccer performance? Unfortunately, the jury is still out on this question. Research suggests that drinking it before the start of preseason training and continuing through the first week or so might help recovery between training days. However, given the small improvements in the arm muscles only, improvements on the pitch may not be noticeable.

References:

Trombold JR, Barnes JN, Critchley L, Coyle EF (2010) Ellagitannin consumption improves strength recovery 2-3 d after eccentric exercise. Medicine and Science in Sports and Exercise, 42:493-498.

Trombold JR, Reinfeld AS, Casler JR, Coyle EF (2011) the effect of pomegranate juice supplementation on strength and soreness after exercise. Journal of Strength and Conditioning Research, 25: 1782-1788.