For individuals with type 1 diabetes (T1D), regular exercise is associated with greater life expectancy and a lower frequency of diabetic complications. However, a study by Carter et al. in this month’s journal reveals that individuals with T1D are at a thermoregulatory disadvantage during exercise. They showed that young, habitually active adults with T1D have a reduced capacity to dissipate heat during moderate intensity exercise in hot conditions, relative to healthy matched counterparts. While people with T1D should be encouraged to exercise, they should also be advised to take appropriate precautions when performing strenuous exercise, especially in the heat. In association with this article, we are making freely available a related publication from the same laboratory [Older Adults with Type 2 Diabetes Store More Heat during Exercise. Med Sci Sports Exerc. 2013;45(10):1906–14].
On a different topic, Haider and Folland found that short-term dietary nitrate supplementation with concentrated beetroot juice (approximately 9.7 mmol nitrate per day) enhanced excitation-contraction coupling of human skeletal muscle in vivo. Specifically, nitrate supplementation increased peak force at low frequencies of electrical stimulation (1–20 Hz), and explosive force production at low (1 Hz) and high (300 Hz) frequencies of stimulation during isometric contractions of the knee extensors in untrained individuals. This augmentation of excitation-contraction coupling in situations where myoplasmic calcium saturation is incomplete is in accordance with previous findings of enhanced intracellular calcium handling after nitrate supplementation in mouse skeletal muscle. However, the effects on the contractile properties observed by Haider and Folland did not translate into changes in voluntary maximum or explosive force production.
In another nitrate study, Boorsma et al. are first to test the effects of both acute (2.5 h) and chronic (8 d) beetroot juice (BR) supplementation in elite middle distance runners. BR supplementation did not affect running economy or 1500-m time trial performance, consistent with recent publications with well-trained cyclists and cross-country skiers. However, in the present study this could not be attributed to insufficient nitrate exposure as the increase in plasma nitrate was 2.2- and 3.3-fold greater for acute and chronic supplementation, respectively, compared to previous reports. Importantly, this study and previous work, identified positive responders, suggesting that BR supplementation may be effective for a small proportion of elite athletes. In connection with this month’s articles on nitrate supplement, we highlight a prior publication by Bescos et al. [Acute Administration of Inorganic Nitrate Reduces VO2peak in Endurance Athletes. Med Sci Sports Exerc. 2011; 43(10):1979–86]
L. Bruce Gladden