Expert Q & A

By Steven J. Fleck, PhD

Increased protein synthesis is important because over the long term, it will result in an increase in muscle mass. It's clear that supplementation either right before or right after a weight-training session can increase muscle protein synthesis. Sports science studies involving ingestion of protein immediately prior to (Tipton et al., 2001), or within three hours after, a weight-training session (Borsheim et al., 2002; Gibala, 2000; Rasmussen et al., 2000) show increases in muscle protein synthesis. This increase appears to be related to a more favorable anabolic environment as a result of changes in hormonal concentrations, such as an increase in blood insulin or growth hormone (Hulmi et al., 2005; Volek, 2004).

Some evidence indicates protein supplementation immediately prior to exercise increases protein synthesis to a greater extent compared to supplementation at various times after exercise (Tipton et al. 2001). The increased protein synthesis with supplementation prior to exercise may be related to a boost in blood flow during exercise, which increases amino acid availability to the muscle being trained during the session (Volek, 2004; Wolfe, 2001). With an increase in blood flow, greater delivery of the amino acids from the supplement takes place. With greater delivery of amino acids to the muscle being trained, there's a possibility that more of these amino acids will be used in the protein synthesis of muscle. An alternative explanation is that protein synthesis is stimulated by both exercise due to an increase in blood flow and an increased hormonal response when a supplement is consumed before exercise. As a result, the stimulation of protein synthesis continues- not just during the exercise session- but after the session as well. When a protein supplement is taken immediately after a training session, there's little effect of increased blood flow on muscle protein synthesis, and the increase in muscle protein synthesis is more dependent on the hormonal response to the training session. However, one bottom line aspect of this evidence is that supplementation either before or after a weight-training session will increase muscle protein synthesis.

A very recent sports science project indicates that supplementation after a weight-training session increased the androgen receptor content of muscle (Kraemer et al., 2006). Although we spend a great deal of time talking about the hormonal response (such as an increase in testosterone or growth hormone in the blood) because of supplementation and weight training, we tend to forget that hormonal response is only part of what needs to happen to increase protein synthesis. One important aspect of this process is that the hormone needs a receptor within the muscle with which to bind in order to trigger increased protein synthesis. This new study shows that supplementation immediately after a weight-training session results in increased androgen receptor content of muscle. This widens the possibility that a hormone circulating in the blood will actually bind to a muscle's receptor, increasing the chance that the hormone will actually cause a rise in protein synthesis, because if the hormone doesn't bind to a receptor, nothing will happen. There was no comparison to supplementation prior to a weight-training session in this study, so we don't know if supplementation prior to the session would also increase androgen receptor content in muscle, or if there's any difference in androgen receptor content when a supplement is taken immediately before or immediately after training.

Protein supplementation immediately prior to, or right after, a weight-training session increases protein synthesis. An increase in protein synthesis over long periods of training can result in an increase in muscle mass. Therefore, taking a protein supplement right after your weight-training session should be a valuable tool in increasing muscle mass over time.

Q: I've heard that you shouldn't stretch right before a weight-training session because this will decrease your maximal strength and power. I've noticed, however, that the majority of the studies looking at the effects of stretching right before a training session have studied people with little or no stretching experience. I've been stretching for years and want to know if stretching right before a weight-training session will still decrease my maximal strength and power during a training session.

A: You've made a very astute observation. You're correct in that the majority of studies looking at the effect of stretching prior to a weight-training session on strength and power have generally looked at people with little or no training history of stretching. However, a recent sports science research project addresses the possible effect of a stretching training history on whether or not stretching right before a resistance-training session affects maximal strength and power in a training session. You've been stretching for years; this study looked at college-age males and females who had been stretching for at least 10 weeks in physical education classes. These students weren't competitive athletes, but were recreationally active in a wide variety of sports such as basketball, volleyball, soccer, swimming, tennis and weight training. So they were at least "recreationally" physically fit. They also had pretty good flexibility, with all study participants having a sit-and-reach flexibility score greater than the 60th percentile.

In order to look at the effect of stretching on maximal strength, the college students performed a stretching routine for the hamstrings and quadriceps muscle groups right before determination of their one-repetition maximum in the knee curl and knee extension. The stretching routine consisted of five different stretches for the hamstrings and quadriceps. They repeated each stretch three times, holding for 15 seconds to the point of discomfort, and then taking a 15-second rest between successive stretches. The entire stretching routine took about 20 minutes. After stretching, their one-repetition maximum in both the knee curl and knee extension significantly decreased compared to no stretching. Knee curl one-repetition maximum decreased approximately 3.4 percent, while knee extension one-repetition maximum decreased approximately 5.6 percent after stretching, compared to no stretching.

The results indicate that even in people who have a stretching training history, stretching right before a training session would decrease maximal strength and power. The people in this study had a stretching training history of 10 weeks; you've been stretching for years, so there's the possibility that with a longer stretching training history, the effect on maximal strength and power could be different. However, you can make physiological arguments either in favor of a longer stretching training history (resulting in less of a decrease in maximal strength and power) or increasing the decrease in maximal strength for power, compared to people with no or a relatively short-term stretching training history.

So, if you have a stretching training history of several years and are truly interested in expressing your maximal strength and power, you should probably err on the side of caution and not perform stretching prior to your resistance training sessions. Instead, perform your stretching routine after the training session, as the effect of stretching on maximal strength and power is an acute effect, and stretching after the training session won't have any effect on your maximal strength and power in the following day's training session.

It's also important to remember that the effect of stretching on maximal strength and power only takes place in the muscle groups that are stretched. This means you can stretch your legs right before an arm workout and there wouldn't be an effect on the maximum strength and power of your arms. I hope this gives you some guidance concerning your stretching routine.

References:

1. Borsheim E, Tipton KD, Wolf SE, and Wolfe RR. Essential amino acids and protein recovery from resistance exercise. Am J Physiol Endocrinol Metab, 283: E684-E687, 2002.
2. Gibala MJ. Nutritional supplementation and resistance exercise: What is the evidence for enhanced skeletal muscle hypertrophy? Can J Appl Physiol, 25: 524-535, 2000.
3. Hulmi JJ, Volek JS, Selanne H, and Mero AA. Protein ingestion prior to strength exercise affects blood hormones and a metabolism. Med Sci Sports Exerc, 37: 1990-1997, 2005.
4. Kraemer WJ, et al. Androgenic responses to resistance exercise: effects of feeding and l-carnitine. Med Sci Sports Exerc, 38: 1288-1296, 2006.
5. Rasmussen BB, Tipton KD, Miller SL, Wolfe SE, and Wolfe RR. An oral amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. J Appl Physiol, 88: 386-392, 2000.
6. Tipton K, Rasmussen BB, Miller SL, Wolfe SL, Wolfe SE, Owens-Stovall SK, Petrini BE, and Wolfe RR. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol, 281: E197-E206, 2001.
7. Volek JS. Influence of nutrition on responses to resistance training. Med Sci Sports Exerc, 36: 689-696, 2004.
8. Wolfe RR. Effects of amino acid intake on anabolic processes. Can J Appl Physiol, 26: S220-S 227, 2001.
9. Nelson AG, Kokkonen J, and Eldredge C. Strength inhibition following an acute stretch is not limited to novice stretchers. Res Quart Exerc Sport, 76:500-506, 2005.