Heart Rate Variability Monitoring During Strength and High-Intensity Interval Training Overload Microcycles

Schneider C, Wiewelhove T, Raeder C, Flatt AA, Hoos O, Hottenrott L, Schumbera O, Kellmann M, Meyer T, Pfeiffer M, Ferrauti A

Question

Can daily HRV monitoring identify fatigue and recovery during strength and HIIT overload microcycles in trained athletes?

Summary

This athlete overload study tracked daily heart-rate variability during short periods of strength or HIIT overload. In the HIIT arm, performance dipped after overload and rebounded after recovery, while standing HR and HRV changed, but HRV markers were not consistent individual performance predictors.

Methodology

Trained strength athletes and team-sport athletes; HIIT arm was team-sport trained
37 participants.
Track running, shuttle runs, and sprints.
Work intervals: 4 min, 2 min, 5 sec, or 30 sec depending on session.
Recovery: 25 sec to 5 min depending on session.
Intensity: 80-90% VIFT or all-out sprints.
About 35 minutes.
Up to two sessions/day over 6 days.
6-day overload plus 4-day recovery.
Repeated-measures overload microcycle study with separate strength and HIIT arms
Heart-rate variability, Repeated sprint ability, and VIFT were tracked.

Outcomes

RSA

HIIT RSA performance decreased immediately after overload and increased after recovery.

Mean peak velocity Post1 -0.18 m/s; Post4 +0.18 m/s.

Mixed

Standing HRV

Standing HR decreased and standing Ln RMSSD increased during overload/recovery, then reversed.

Standing HR dpre about -0.50 to -0.59; Ln RMSSD dpre about 0.38 to 0.47.

Mixed

Supine HRV

Supine measures were less responsive than standing measures.

No clear change

HRV prediction

Associations between HR/HRV and performance were weak or inconsistent.

Unclear

Insights

Short overload blocks can transiently depress performance and require recovery.
Standing HRV may be more informative than supine HRV in this context, but not deterministic for individuals.

Limitations

Athlete-only overload design.
No no-overload control group.
Short study window.
HRV-influencing behaviors not fully controlled.
Adverse-event reporting limited.

Safety

Adverse events were not systematically reported.
One participant dropped out due to injury among eligible participants; the text available did not clearly attribute this to the HIIT arm.
Participants had preliminary health exams including resting and exercise ECG to exclude cardiovascular, pulmonary, and orthopedic disease.
The protocol was a dense supervised overload microcycle for trained athletes.