News & Views from the Editor-in-Chief - L. Bruce Gladden
There are many excellent articles in this month's issue, but I am directing attention to three of them. First, impairments in sweat function during passive heat stress have been identified in multiple sclerosis (MS), a demyelinating disease of the CNS that disrupts autonomic function. Accordingly, Allen et al. investigated the impact of these sweating impairments on the thermoregulatory-reflex control of body temperature during dynamic exercise in MS. They observed blunted sweating and sweating thermosensitivity responses in individuals with MS compared to matched healthy controls during moderate exercise in a thermoneutral environment, while core temperature and skin vasculature vasodilation responses were similar between groups. These impaired mechanisms of thermoregulation in persons with MS may lead to excessive increases in body temperature during exercise under more thermally challenging conditions, thus putting this clinical population at elevated risk of heat-related difficulties and decreased exercise tolerance.
Next, using a hybrid laboratory–field study design, McKay et al. implemented a 3-wk ketogenic low carbohydrate (CHO) high fat (LCHF) diet in world-class race walkers. Following a 2-h race-walk, athletes who consumed either high or periodized CHO diet, exhibited an attenuated interleukin-6 response to exercise and lower hepcidin-25 levels relative to the LCHF group. Elevated hepcidin levels may impair iron absorption in the hours following exercise with negative consequences on iron status. However, greater reductions in serum ferritin occurred in athletes adhering to a CHO-rich diet (37%) compared to the LCHF group (23%), potentially signalling a greater draw on iron stores to support a larger adaptive training response in the CHO-supported groups. This study draws attention to the complicated metabolism of iron in response to exercise and supports further investigation of its interaction with changes in CHO availability.
Finally, Jonvik et al. investigated the effects of dietary nitrate and sucrose ingestion on splanchnic perfusion and intestinal injury induced by strenuous cycling exercise. During cycling, there was a profound decline in splanchnic perfusion, which was accompanied by substantial increases in plasma intestinal fatty-acid binding protein (I-FABP) levels, indicating intestinal injury. While there was no effect of dietary nitrate, sucrose ingestion clearly attenuated the increase in plasma I-FABP levels. This study shows that ingesting small amounts of carbohydrate (2 × 20 g) shortly before and during strenuous cycling strongly attenuates exercise-induced intestinal injury. The authors propose that athletes experiencing ischemia-related gastrointestinal complaints during exercise of high-intensity and/or long duration may benefit from carbohydrate ingestion during exercise.
L. Bruce Gladden
School of Kinesiology