Increased vagal tone in soldiers with above average physical fitness serving in military special forces

Abstract

Intensive physical activity changes the sympatho-vagal balance and influences cardiovascular function by increasing vagal tone. The aim of the study was to investigate which changes in rhythm and sympatho-vagal balance can be observed in soldiers serving in military special forces (SF group) in comparison with soldiers serving in regular units (RU group). In a group of 194 soldiers (124 SF and 70 RU) the electrocardiographic assessment was based on 24-h Holter recordings and physical capacity was objectified by ergospirometry. SF group was characterized by lower 24-hours mean HR (63 ±8 bpm vs 68 ±8 bpm, p <0.0005), minimal HR (45 ±5 bpm vs 42 ±8 bpm, p <0.0005) and maximal HR (111 ±19 bpm vs 119 ±17 bpm). They also more frequently presented features of increased vagal tone: bradycardia <50 bpm (98% vs 83%) and pauses exceeding 2 sec (22% vs 9%, p =0.018). Soldiers serving in military special forces present above average physical fitness. In consequence rhythm and conjunction changes typical for the athlete’s heart phenomenon can be observed in this population. In some cases it may be advisable to perform exercise test and/or 24-hour electrocardiographic monitoring to exclude abnormalities other than related to increased vagal tone.