Impact of sodium citrate ingestion during recovery after strenuous exercise in the heat on heart rate variability: A randomized, crossover study. Issue 9 (4th May 2022)

• Record Type: Journal Article
• Authors: Fiedler, Janis; Šmite, Zane; Suvi, Silva; Timpmann, Saima; Mooses, Martin; Medijainen, Luule; Unt, Eve; Ööpik, Vahur
• Is Part Of: Physiological reports. Volume 10:Issue 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-04
• Subjects: dehydration -- endurance athlete -- exercise‐heat stress -- plasma volume; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.15280
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Changes in hydration status influence plasma volume (PV) which is associated with post‐exercise parasympathetic reactivation. The present study hypothesized that, after dehydrating cycling exercise in the heat (DE), stimulation of PV expansion with sodium citrate (CIT) supplementation would promote heart rate variability (HRV) recovery in endurance‐trained men. Twelve participants lost 4% of body mass during DE. During subsequent 16‐h recovery, participants consumed water ad libitum (CIT =5.5‐L, PLC =5.1‐L) and ate prescribed food supplemented with CIT or placebo in a randomized, double‐blind, crossover manner. Relative changes in PV were assessed across DE and 16‐h recovery. HRV was analyzed before and 16 h after DE in three conditions for altogether four 5‐min periods: supine in a thermoneutral environment, supine in the heat (32°C, 46% relative humidity; 2 periods), and standing in the heat. A larger expansion of PV across 16‐h recovery occurred in CIT compared to placebo trial ( p < 0.0001). However, no between‐trial differences appeared in HRV parameters (lnRMSSD, lnSDNN, lnLF/HF) in any 5‐min period analyzed before or 16 h after DE (in all cases p > 0.05). Increases in HR ( p < 0.001) and lnLF/HF ( p = 0.005) and decreases in lnRMSSD ( p < 0.001) and lnSDNN ( p < 0.001) occurred following DE in both trials. Larger PV expansion induced by CIT supplementation after DE does not improve recovery of HRV at rest and has no influence on HRV responsiveness in endurance‐trained men. Abstract : Enhanced plasma volume expansion by sodium citrate supplementation after strenuous exercise did not improve the recovery of any HRV indices at rest. Additionally, 16 h are not a sufficient time for the recovery of HRV and HR measures after strenuous exercise in the heat.