Luetkemeier, M. J., & Bradburn, M. J. (2010). Effect of dietary protein intake on nitrogen balance during resistance exercise training. Presentation 793 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

This study determined the effect of dietary protein intake on nitrogen balance while engaged in resistance exercise training in college seniors (N = 23). Before the experiment, Ss began a 3-days per week resistance-training program (or continued one that was already initiated) consisting of 13 exercises emphasizing the arms, legs, core, back, and chest. Ss were then randomized into four groups according to four levels of dietary protein intake (0.4, 0.8, 1.2, and 1.6 grams/kg BW). Ss consumed their assigned diets for one week and then advanced to the next diet for the subsequent three weeks. A 24-hour urine sample was collected on the last day of each weekly diet to determine urea nitrogen and nitrogen balance.

There was a significantly lower nitrogen balance for the 0.4, 0.8, and 1.2- grams/kg BW groups than for the 1.6-grams/kg BW group. There was a significantly lower nitrogen balance for the 0.4-grams/kg BW group than the 0.8, and 1.2 grams/kg BW groups.

Implication. A dietary protein intake of at least 1.6 grams/kg BW is required to maintain neutral nitrogen balance while engaging in resistance exercise training. [This finding supports Stegeman's recommendation of 2 gm per kilo of BW as being the base requirement of protein intake for athletes in training.]

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