Ribose and its Effect on Energy Recovery in Heart and Skeletal Muscle

by Terri L. Butler, Ph.D.
Bioenergy, Inc.

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Ribose Effects in Skeletal Muscle

Several studies have noted that while healthy skeletal muscle has a large capacity for high-energy phosphate turnover, intense exercise causes significant decreases in ATP and total adenine nucleotides (TAN) pools. One study showed that one week of high-intensity exercise significantly decreased levels of both ATP and TANs in skeletal muscle with no meaningful recovery even after 72 hours of rest.9

This decrease in ATP (23%) and TAN (24%) is reflective of the loss of nucleotides from muscle during and following high intensity exercise. Furthermore, the delayed recovery of ATP and TANs is likely explained by the lack of the availability of 5-phosphoribosyl-1-pyrophosphate (PRPP), the rate-limiting factor in adenine nucleotide synthesis and salvage. A second study found that resting ATP and TAN levels were lowered by 19% and 18% respectively after high intensity exercise training.7

These lowered levels were primarily attributed to an inability of skeletal muscle to completely restore the purines that were lost as a result of high ATP turnover during training periods. Total purines continue to decline in the first few minutes following exhaustive cycle exercise as found in a study of 8 healthy male subjects.11 An average decrease of 6.3% in total purines was seen between the time the exercise period ended and 3 minutes into recovery. This provides evidence that there are rapid changes in TAN levels due to degradation and purine efflux.

In two benchmark studies ribose administered to isolated hind limb muscle fibers in vitro led to increased adenine nucleotide de novo synthesis rates of 3.4 to 4.3-fold and adenine and hypoxanthine salvage rates of 3 to 6-fold. 10,33 Fast-twitch red gastrocnemius, fast-twitch white gastrocnemius, fast- twitch mixed plantaris, and slow-twitch red soleus muscle fiber types were studied.

The greatest increase in both de novo synthesis and adenine and hypoxanthine salvage rates were seen in the low-oxidative fast-twitch white gastrocnemius muscle, with significant increases in the other muscle types as well. The importance of ribose in skeletal muscle energy metabolism was noted, and its impact on PRPP availability thought to be most critical.10

In a follow-up study these researchers found that without added ribose adenine salvage rates were low in both resting muscle and post-contracted recovering muscle, but with the addition of 5mM ribose to the perfusion medium these rates increased 5-fold.34

They also found that increasing the adenine nucleotide salvage rates by adding ribose to the perfusion medium did not result in a larger ATP pool. Instead, they found that, in spite of increased salvage rates, ATP concentrations were controlled within narrow limits by activation of adenine nucleotide degradation.35

In a study of 16 human athletes those subjects taking supplemental ribose had a larger increase in mean power over 5 days of training (4.2% vs. 0.6%), and greater peak power output at the last sprint session (11.4 watts/kg vs. 10.4 watts/kg, p=0.05 time) than the placebo group. 36 In this study 8 subjects consumed ribose and 8 subjects consumed glucose placebo, each at a dose of 10 grams two times per day. The study consisted of three phases, a loading phase, a training phase, and a recovery phase.

During the loading phase, which was 72 hours long, the subjects did not exercise but consumed their respective supplement twice a day. The subjects then entered the training phase, which was 5 days long, during which they continued taking their supplements and began high intensity exercise bouts twice per day. The exercise bouts consisted of 15 x 10 second cycle sprints at a workload of 0.07 kg/kg body weight with a 50 second rest between each sprint. After the training phase the subjects entered a 65 hour recovery phase where they continued taking supplemental ribose or glucose placebo, but did not exercise.

Throughout the training sessions the mean power output was consistently higher in the subjects who consumed ribose than in the subjects who consumed glucose placebo. (Figure 4). Also, the percent fatigue was consistently less in the ribose group than in the placebo group (Figure 5).

Figure 4. The mean power output per kilogram body weight for athletes consuming ribose supplement or glucose placebo. For each group n = 8.

Figure 5. Percent fatigue in athletes consuming ribose supplement or glucose placebo. For each group n = 8.

Another aspect of the same study showed that ribose supplementation partially attenuated the decrease in TAN levels after the 5 days of exercise (p < 0.05).37 While the placebo and ribose groups displayed a similar pattern of recovery of TAN levels, the ribose group recovered to pre-exercise levels after the 65 hour recovery period, but the placebo group remained at 23% below pre-exercise levels (Figure 6).

Figure 6. Total adenine nucleotide levels from muscle biopsies in athletes consuming ribose supplement or glucose placebo. For each group n = 8.

The fact that ATP and TAN levels decrease during exercise and normally do not recover even after three days of rest indicates that without supplementation skeletal muscle has a limited ability to maintain peak performance during periods of repeated high-intensity exercise. However, the studies reviewed here indicate that the administration of ribose leads to an increase in the power output in athletes and improves the ability of skeletal muscles to quickly recover their energy levels after high intensity exercise.

Indeed a study of exercise performance over 4 weeks in male bodybuilders showed a significant increase in the number of total repetitions performed in bench press exercises in athletes taking ribose compared to athletes taking glucose placebo.38 The subjects were randomly divided into two groups, 5 subjects consuming ribose and 7 subjects consuming glucose placebo. The supplements were taken in divided doses, 5 grams 15 minutes prior to exercise and another 5 grams immediately post-exercise. The ribose group experienced a significant increase in the number of bench press repetitions performed to muscular failure (Figure 7, +29.8% ribose vs. +7.42% placebo, p = 0.046).

Figure 7. Increase in number of repetitions to failure in bench press exercise in male bodybuilders after 4 weeks of supplementation and exercise training (placebo n = 7, ribose n = 5).

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