Insulin: To Spike or Not to Spike?

Post-exercise nutrition is critical for maximum gains
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In 2007, a group working out of Maastricht University in the Nether- lands examined the impact of adding carbohydrates on post-exercise muscle protein synthesis. 1They had 10 healthy20-somethings work out for one hour using a traditional resistance exercise protocol. The three post-workout treatment conditions were protein only (PRO), protein with a low carbohydrate dose (PRO + LCHO), or protein with a high carbohydrate dose (PRO+ HCHO). A total of 12 servings were given every 30 minutes for each treatment condition to ensure a continuous and ample supply of both glucose and amino acids during the six hours of recovery. Each subject returned seven days later to receive a different post- exercise treatment until all had been tested under each condition.

Their results indicated that, given an ample amount of easily digested high-quality protein (casein hydrolysates), added carbohydrates had no effect on post-workout protein synthesis rates regardless of the amount of carbs given.

In support of these findings, another study more recently published in Medicine and Science in Sports and Exercise utilized a similar protocol (i.e., work- outs followed by protein or protein +carbs) but this time they were more interested in the impact of creating a post-workout insulin spike. Would it affect protein synthesis rates? Would it decrease protein breakdown? Would it trigger anabolic signaling pathways more effectively? You probably knowwhere this is heading. The answer is no, it didn’t. spiking insulin didn’t reduce protein breakdown, and it didn’t enhance anabolic signaling pathways. The insulin spike didn’t even increase muscle blood flow! What appears to have happened was,because they used a protein source(whey) that has already been shown to maximally stimulate post-exercise protein synthesis as well as increase insulin levels, no further anabolic effect was possible even from an insulin spike. The insulin level triggered by whey alone was able to maximally inhibit protein breakdown, increase blood flow, and activate anabolic signaling pathways.

The take-home message is: Just make sure you are getting some high- quality, easily digested protein into your gullet immediately after your workout. Whether you ad carbs or not will not have a significant effect either way.

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