(25-10-11) Systemic Acid Load from the Diet Affects Maximal Exercise Respiratory Exchange Ratio.

Niekamp K, et al. Show all
Affiliation
1Department of Nutrition and Dietetics, Saint Louis University, St. Louis, MO; 2Human Physiology Laboratory, Marywood University, Scranton, PA; 3The Commonwealth Medical College, Scranton, PA; 4Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO; 5Division of Nutrition and Aging, Istituto Superiore di Sanita, Rome, Italy.
Abstract
A maximal exercise respiratory exchange ratio (RERmax) ??1.10 is commonly used as a criterion to determine if a "true" maximal oxygen uptake (VO2max) has been attained during maximal-effort exercise testing. Because RERmax is heavily influenced by CO2 production from acid buffering during maximal exercise, we postulated that dietary acid load, which affects acid-base regulation, might contribute to variability in RERmax.
PURPOSE: To determine if a habitual dietary intake that promotes systemic alkalinity results in higher RERmax during VO2max testing.
METHODS: Sedentary men and women (47-63y, n=57) with no evidence of cardiovascular disease underwent maximal graded treadmill exercise tests. VO2max and RERmax were measured with indirect calorimetry. Habitual diet was assessed for its long-term effect on systemic acid-base status by performing nutrient analysis of food diaries and using this information to calculate the potential renal acid load (PRAL). Participants were grouped into tertiles based on PRAL.
RESULTS: The lowest PRAL tertile (alkaline PRAL) had higher RERmax values (1.21??0.01, p??0.05) than the middle tertile (1.17??0.01) and highest PRAL tertile (1.15??0.01). There were no significant differences (all p??0.30) among PRAL tertiles for RER at submaximal exercise intensities of 70%, 80%, or 90% VO2max. After controlling for age, sex, VO2max, and maximal heart rate (HRmax), regression analysis demonstrated that 19% of the variability in RERmax was attributed to PRAL (r=-0.43, p=0.001). Unexpectedly, HRmax was lower (p??0.05) in the low PRAL tertile (164??3 beats/min) versus the highest PRAL tertile (173??3 beats/min).
CONCLUSION: These results suggest that individuals on a diet that promotes systemic alkalinity may more easily achieve the RERmax criterion of ??1.10 which might lead to false-positive conclusions about achieving maximal effort and VO2max during graded exercise test.

Source: Med Sci Sports Exerc. 2011 Sep 9. [Epub ahead of print]

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