The R⁴ System is an important milestone in our understanding of exercise physiology and is the basis of a new book, Optimal Muscle Recovery by Dr. Edmund Burke (Avery Publishing). Based on leading edge science, the R⁴ System establishes a new model that explains how the interaction of key physiological and nutritional factors enable muscles to operate at peak levels. Equally important, the R⁴ System establishes four simple, practical principles that every aerobic athlete can incorporate into his/her daily training to optimize recovery and achieve full muscle potential.

To understand why the R⁴ System represents a major breakthrough, one must look at research in exercise physiology conducted over the last 30 years. The first important milestone was the finding in the late 60's that showed that fluid and electrolyte replenishment play an essential role in muscle performance before, during and after exercise. The second milestone, in the 70's, defined the role carbohydrate supplementation plays in extending endurance and speeding recovery. These studies led to the technique of carbohydrate loading.

In the 90's research conducted at leading universities has significantly advanced our understanding of muscle physiology and has identified additional factors that influence muscle performance. This research has shown that:

• Insulin stimulates the replenishment of muscle glycogen stores and prevents protein breakdown
• Insulin is so essential in the post exercise recovery process that it can be termed the "master recovery hormone"
• Protein and specific amino acids can enhance the insulin response thereby speeding muscle recovery
• Free radicals buildup (oxidative stress) is an important component of exercise induced muscle damage
• Anti-oxidants, amino acids and certain natural supplements can help reduce muscle damage and prevent oxidative and muscle stress

These scientific findings coupled with previous research on hydration and carbohydrate utilization has led to a new model of exercise physiology - the R⁴ System. The R⁴ System is based on four core principles:

1. Restore electrolytes and water.
2. Replenish glycogen stores rapidly.
3. Reduce muscle and oxidative stress.
4. Rebuild muscle protein.

The R⁴ System provides simple framework for the aerobic athlete to optimize muscle performance and speed recovery.

How the R⁴ System Enhances Aerobic Performance

By understanding the science behind the four principles of the R⁴ System and how they interrelate, the aerobic athlete can make enormous strides in improving individual performance.

1. Restore Electrolytes and Water

Fluid and electrolyte restoration is the cornerstone of the R⁴ System and should be the cornerstone of any training program. Fluid and electrolyte replenishment is crucial in maintaining cardiac output and regulating body temperature during exercise. Elevations in body temperature can sharply impair performance. Studies have shown that fluid replacement must occur both during and after exercise. Electrolytes, now usually added to sports hydration drinks, can accelerate rehydration by speeding intestinal reabsorption of fluids and improve fluid retention.

2. Replenish Glycogen Stores Rapidly

The role carbohydrate plays as a fuel source during exercise has shaped modern sports nutrition. Early studies primarily focused on replenishment of glycogen stores by consumption of a carbohydrate supplement both during and after exercise. Carbohydrate supplementation stimulates insulin, a key element in the glycogen replenishment process. Insulin has two major roles: (1) Facilitates the transport of glucose into the muscle cell; (2) Stimulates enzymes responsible for the synthesis of glycogen from glucose.

Recent studies have extended our understanding of how glycogen is replenished. A post exercise carbohydrate supplement composed of high Glycemic Index Carbohydrates (such as simple sugar) is more rapidly transported into the muscle cell in the critical post recovery period. Enzymes responsible for manufacture of muscle glycogen are maximally stimulated 0-2 hours after exercise. Therefore it is essential that a carbohydrate supplement be taken in this time frame to optimize recovery.

Even more significant are research findings showing that protein and the amino acid, arginine, when combined with a carbohydrate supplement can strongly stimulate insulin levels in a synergistic fashion. The ratio of carbohydrate to protein is extremely important to obtain this synergy. The Optimum Recovery Ratio (OR²) should be 4:1 (four grams of carbohydrate to one gram of protein.) By further stimulating insulin with protein and arginine, muscle glycogen is restored quicker. The result - improved performance and a faster recovery.

Insulin, the "Master Recovery Hormone"

Investigators have shown the importance of carbohydrate supplementation in improving performance. The regulator of glycogen replenishment is the hormone insulin which increases the transport of glucose from the blood into the muscle and stimulates the enzyme responsible for the conversion of glucose into glycogen. Recent research has shown that insulin is so important in recovery from exercise that it should be termed the "master recovery hormone". In addition to its vital role in glycogen replenishment insulin helps rebuild and maintain muscle protein. These studies demonstrate that insulin:

• stimulates the transport of amino acids into the muscle. By increasing the cell's amino acid levels insulin speeds the protein rebuilding process following exercise.

• blunts the rise in cortisol following exercise. Cortisol is the hormone responsible for protein breakdown. By decreasing cortisol levels, insulin helps maintain muscle protein.

This research also calls into doubt the usefulness of products based on the 40-30-30 formula. Since these products reduce insulin levels, they may actually slow the recovery process.

3. Reduce Oxidative/Muscle Stress

The muscle cell undergoes considerable trauma during exercise. This trauma leads to soreness and rebuilding of muscle post exercise. It is only recently that the causes of oxidative and muscle stress have been better defined. During exercise there is a buildup of free radicals. Free radicals are largely responsible for damage to the muscle cell membrane. In addition to free radical buildup, exercise stimulates cortisol; the body's stress hormone. Cortisol increases the breakdown of protein. A third consequence of hard exercise is a negative effect on the immune system.

As researchers better understood the causes of muscle stress, they have identified agents to help minimize it. Vitamin C and E are strong anti oxidants shown to reduce free radical buildup during exercise. Insulin has been shown to blunt the cortisol rise normally seen during exercise thereby helping maintain muscle protein. The amino acid glutamine has been shown to stimulate the immune system. Reducing muscle damage, bolstering the immune system and preventing soreness results in a faster recovery and the ability to maintain a higher training level.

4. Rebuild Muscle

Immediately following exercise a rebuilding process is initiated to repair muscle proteins damaged during exercise. Recent evidence suggests that insulin is a strong stimulus of the muscle rebuilding process by increasing amino acid transport into the muscle and by preventing the breakdown of protein. This interrelationship between glycogen replenishment, insulin and muscle rebuilding is a cornerstone of the R⁴ System.

A second aspect of the rebuilding process is the need for protein, glutamine and branched chain amino acids. Protein not only stimulates the replenishment of glycogen stores by activating insulin, but also provides the essential building blocks for muscle repair.

The Development of Endurox^® R^4®

In 1997, leading exercise physiologists met in Colorado Springs, Colorado to review the latest studies on exercise performance and to formulate a new sports nutrition product based on the R⁴ System. These experts speculated that such a product would offer major advantages over the wide array of sports nutrition products and drinks because it would:

• Significantly improve endurance
• Protect the muscle cell from post exercise muscle damage by preventing free radical buildup thereby accelerating muscle recovery
• Stimulate insulin response thereby speeding the replenishment of muscle glycogen stores enabling a faster recovery from exercise
• Facilitate the rebuilding of muscle tissue damaged as a consequence of exercise

Endurox R4 Formulation	Restore Electrolytes	Replenish Glycogen	Reduce Muscle Stress	Rebuild Muscle
Potassium
Sodium
Magnesium
High Glycemic Carbohydrate
Carbohydrate/Protein (OR2=4:1)
Arginine
Vitamin E
Vitamin C
Glutamine
Branched Chain AA
Whey Protein

Three trials were fielded to determine if a drink based on the R⁴ System would deliver these benefits. The results from the two trials are powerful proof that the R⁴ System can improve muscle performance and facilitate recovery following exercise. The researchers found that the Endurox R⁴ Recovery drink when compared to Gatorade: