May 23, 2014

How Many Carbs Do You Need Post-Exercise?

If a bodybuilder asked  "Do I need carbohydrates in my drink, post-exercise?" they would have said, "You probably need some carbohydrates because of the anti-catabolic actions of the insulin spike." If someone were to ask the exact amount of grams, we wouldn't have an answer. As you know, insulin is an anti-catabolic hormone that suppresses protein breakdown.

In contrast, infusion of a low dose of insulin directly into the brachial artery has been reported to achieve the maximal effect on protein breakdown. It’s interesting that diabetics or patients with insulin resistance have increased muscle protein breakdown and increased muscle atrophy, due to the defects in insulin signaling.The increased breakdown of muscle in diabetics is also due to elevated ubiquitin-proteasome pathway (UPP) levels, which create a catabolic scenario.

Carbohydrate supplements reduce muscle protein breakdown, but have no effect on muscle protein synthesis. In fact, even though carbohydrate ingestion reduces muscle tissue breakdown, the net balance of protein kinetics still remains negative. Most bodybuilders recommend incorporating periodichigh-glycemic meals, which spike insulin— especially post-workout. This is not only effective for maintaining an anabolic state, but the insulin spike that results also shuts down the UPP pathway and reduces muscle tissue breakdown.

A recent study  reports that increasing amino acids, or leucine alone, acts with insulin to downregulate muscle protein breakdown and reduce UPP. Thus, the use of l-leucine while dieting seems to be effective for reducing muscle tissue breakdown by reducing UPP. In addition to hormonal stimulators of UPP, resistance exercise also increases UPP, which is a normal adaptation to exercise. For years, bodybuilders have been told to consume a high-glycemic index shake with some added protein/BCAAs after exercise, but a new study will make you ask, do you need a ton of carbs, post-exercise?

How Much Is Enough?

A new study examined both low and high carbohydrate ingestion before resistance exercise to determine how many carbs is enough. The researchers used equivalent amounts of essential amino acids (~20 grams) but differing amounts of carbohydrates (low carbohydrates = 30 grams; high carbohydrates = 90 grams). The male research subjects ingested nutrients one hour after an acute bout of leg-resistance exercise.

30-Gram Rule

The results of the study were quite interesting. Of course, the group that consumed 90 grams of carbohydrates had larger increases in blood glucose levels, but the results in protein synthesis were similar.The researchers concluded that the findings were similar to previous studies, which found that muscle protein synthesis is not enhanced when carbohydrates exceed 30 grams. The researchers did not detect any significant differences in gene expression for markers of muscle catabolism following larger dosages of carbohydrates.7They concluded that the changes in muscle protein synthesis were due to changes in the essential amino acids, while only a moderate dose of carbohydrates (~30 grams) is needed. Furthermore, these changes occur irrespective of the carbohydrate dose or circulating insulin levels.

So when bodybuilders are using post-workout carbohydrate beverages, 30 grams are all you need— and taking more than that does not seem to provide additional benefit in terms of muscle protein breakdown.

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