Evidence of parasympathetic hyperactivity in functionally overreached athletes

Area of Science:

• Sports Science
• Physiology
• Autonomic Nervous System Research

Background:

• Functional overreaching (F-OR) is a state of temporary fatigue in athletes.
• Autonomic dysfunction is implicated in F-OR.
• Heart rate variability (HRV) is a non-invasive tool to assess autonomic function.

Purpose of the Study:

• To analyze heart rate variability (HRV) to detect autonomic function alterations associated with functional overreaching (F-OR) in endurance athletes.
• To compare the effectiveness of daily versus weekly averaged HRV recordings in identifying F-OR.

Main Methods:

• Twenty-one trained male triathletes were divided into intensified training (n=13) and normal training (n=8) groups for 5 weeks.
• Heart rate variability (HRV) was measured daily throughout baseline, overload, and taper phases.
• Performance in a maximal incremental running test was assessed.

Main Results:

• The intensified training group met criteria for F-OR, showing decreased performance after overload, followed by supercompensation after taper.
• Weekly averaged HRV indicated a progressive increase in parasympathetic modulation in the F-OR group.
• Isolated daily HRV recordings did not reliably detect autonomic changes related to F-OR.

Conclusions:

• Averaged weekly HRV recordings can detect increased parasympathetic modulation in endurance athletes experiencing F-OR.
• High day-to-day variability in HRV means isolated recordings may miss training-induced autonomic changes in F-OR.
• This suggests a need for consistent, averaged HRV monitoring for effective F-OR detection.