Feet-heating and calf-heating have opposing effects on glucose tolerance and heart rate variability: a randomized, controlled, crossover trial

• Published in: Applied physiology, nutrition, and metabolism nutrition, and metabolism, 2024-10
• Main Authors: Sanchez, Gabriele, Prince, Dena, Glasser, Shelby, Buono, Michael, Kressler, Jochen, Moore, Jeff M
• Format: Article
• Language: English
• ISSN: 1715-5312; 1715-5320; 1715-5320
• DOI: 10.1139/apnm-2024-0265

Heat exposure's effect on glucose tolerance depends on the amount of body exposed, likely relating to autonomic nervous system balance. We assessed how partial-body heat exposure at two different levels of the lower extremities affects glucose tolerance and autonomic nervous system balance, measured via heart rate variability. We hypothesized feet-heating would improve glucose tolerance without affecting heart rate variability, while calf-heating would worsen glucose tolerance and decrease heart rate variability compared to a thermoneutral control condition. In a randomized, controlled, crossover trial, healthy participants' (  = 31, 23(3) years, 45% male) glucose tolerance was measured in (A) thermoneutral; (B) feet-heating; and (C) calf-heating conditions. Every 30 min for 2 h, blood glucose, heart rate, heart rate variability, tympanic temperature, thermal comfort scores, and blood pressure were measured. There were significant interactions between condition and time for blood glucose ( (4.6,72.6) = 2.6,  = 0.036), heart rate ( (3.4, 54.5) = 3.5,  = 0.017), heart rate variability ( (4.3,63.2) = 7.5,