Q: I would like to know when is the best time to take supplements. I've eard two things: 2 hours before the training and 15 minutes after the training. I would like to have your input on that, and obviously why?

Mikael


A: Recovery from exercise is a complex process requiring the replenishment of the body's fuel stores, the repair of damaged muscle tissue and the initiation of training adaptations. This requires the body to switch from a predominantly catabolic state to a predominantly anabolic state. For this transition to occur efficiently and effectively requires not only that the proper nutrients be consumed, but also that they be consumed at the appropriate time.

The major source of fuel used by the skeletal muscles during prolonged aerobic exercise of a strenuous nature is muscle glycogen. The importance of muscle glycogen as a fuel source cannot be overstated. In general, it has been demonstrated that aerobic endurance is directly related to the initial muscle glycogen stores, that strenuous exercise cannot be maintained once these stores are depleted, and that perception of fatigue during prolonged intense exercise parallels the decline in muscle glycogen (Hermansen et al., 1965; Ahlborg, et al., 1967; Bergström and Hultman, 1967; Bergström et al., 1967). Because of the importance of muscle glycogen for sustaining prolonged intense exercise, there has been considerable research to establish the most efficient means for its replenishment once depleted. Early research focused on how to replenish the muscle glycogen stores on a daily basis in preparation for consecutive days of competition or exercise training. However, because many athletes may train or have to compete several times a day, more recent research has focused on how to replenishing the muscle glycogen stores within several hours after exercises. In this regard, questions that have been addressed include the most appropriate amount and frequency of carbohydrate supplementation, the most appropriate times to supplement, as well as the most appropriate supplements to use.

Also, aside from a reduction in the muscle glycogen stores, strenuous exercise will result in muscle tissue damage. This damage is due in part to the physical stress placed on the muscle, particularly during the eccentric phase of muscle contraction (Clarkson and Hubal, 2002; Evans, 2002), and hormonal changes that result in the breakdown of muscle protein, as well as fat and carbohydrate, to provide the fuel for powering muscle contraction (Walsh et al., 1998). However, muscle damage does not just occur during exercise, but can continue after exercise for many hours. This occurs as a result of a protracted exercise hormonal milieu, an increase in free radicals and acute inflammation. Not only will such tissue damage limit performance due to delayed onset muscle soreness, but it will also compromise the replenishment of muscle glycogen and limit muscle training adaptations (O'Reilly et al., 1987; Costill et al., 1990).

More recently, there has been interest in determining the effects of pre- and post-exercise carbohydrate and protein feedings on hormonal responses to exercise (Cade et al., 1992; Chandler et al., 1994; Roy and Tarnopolsky, 1998; Tarnopolsky et al., 1997; Zawadzki et al., 1992). Ingestion of protein with carbohydrate has been reported to increase insulin and/or growth hormone levels to a greater degree than ingestion of carbohydrate alone (Chandler et al., 1994; Zawadzki et al., 1992). Consequently, ingesting protein and carbohydrate prior to exercise may serve as an anti-catabolic nutritional strategy (Carli et al., 1992). Further, ingesting carbohydrate and protein following exercise may promote a more anabolic hormonal profile, glycogen resynthesis, and/or hasten recovery from intense exercise (Roy and Tarnopolsky, 1998; Roy et al., 1997). Over time these alterations may allow an athlete to tolerate training to a greater degree and/or promote greater training adaptations, but the evidence is not yet clear. A considerable amount of research has evaluated dietary protein needs of athletes. Although there is some debate, most studies indicate that in order to maintain protein balance during intense resistance and/or endurance training, athletes should ingest approximately 1.3 to 1.8 g protein per kg body mass per day (Butterfield, 1991; Lemon, 1998; Kreider et al., 1993; Kreider, 1999).

Conclusion
The restoration of muscle glycogen after depletion by exercise is a central component of the recovery process. To maximize the rate of muscle glycogen storage during short-term recovery, it is important to consume a carbohydrate supplement as soon after exercise as possible. If consuming only carbohydrate, supplementation should occur frequently, such as every 30 minutes, and provide about 1.2 to 1.5 g of carbohydrate·kg^-1 body wt·h^-1. However, the efficiency of muscle glycogen storage can be increased significantly with the addition of protein to a carbohydrate supplement. This will reduce both the amount of carbohydrate and frequency of supplementation required to maximize glycogen storage. If both carbohydrate and protein are consumed, it is recommended that 0.8 g carbohydrate·kg^-1 body wt plus 0.2 g protein·kg-1 body wt be consumed immediately and 2-hours after exercise during a 4-hour recovery period. The addition of protein to a carbohydrate supplement also has the added advantage of limiting post exercise muscle damage and promoting muscle protein accretion. Along with a rapid increase in muscle glycogen, these processes can have a significant impact on subsequent exercise performance.

Steve Prud'Homme
Fitness Director, Peak Centre Director


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