PMID 36612955

Research
All papers

High-Intensity Interval Training Combined with Different Types of Exercises on Cardiac Autonomic Function. An Analytical Cross-Sectional Study in CrossFit(R) Athletes

Morlin MT, da Cruz CJG, Guimarães FER, da Silva RAS, Porto LGG, Molina GE

Question

How do cardiac autonomic measures in CrossFit athletes compare with endurance athletes?

Summary

This observational study compared male CrossFit athletes with male triathletes. CrossFit athletes had lower resting parasympathetic and higher sympathetic modulation, less autonomic reactivity to standing, and slower heart-rate recovery at 3 and 5 minutes after maximal exercise, but the design cannot prove CrossFit caused these differences.

Methodology

  • Healthy male CrossFit and triathlon athletes.
  • 34 participants.
  • Mixed high-intensity interval training with endurance, strength, and calisthenics.
  • Intensity: High intensity; not directly prescribed by the study.
  • About 7 hours/week total training volume.
  • About 6 days/week.
  • Average 3.3 years prior exposure.
  • Analytical cross-sectional observational study
  • Resting HRV, Orthostatic HRV, Heart-rate recovery, and VO2peak were tracked.

Outcomes

Resting HRV

CrossFit athletes showed lower parasympathetic and higher sympathetic modulation than triathletes.

LF p=0.01; LFn, HFn, and LF/HF p<0.01.

Safety concern

HRV reactivity

CrossFit athletes showed lower reactivity after postural change.

Several LF/LFn/LF-HF measures p=0.01 to 0.02.

Safety concern

HR recovery

Heart-rate recovery was similar at 60 seconds but slower in CrossFit athletes at 180 and 300 seconds.

No 60-second difference; 180 and 300 seconds p<0.01.

Safety concern

Insights

  • Autonomic recovery and training load may deserve attention in frequent high-intensity mixed-modality athletes.
  • This paper should inform recovery caution, not causal claims about CrossFit.

Limitations

  • Cross-sectional observational design.
  • No sedentary control.
  • Male athlete-only convenience sample.
  • Training volume differed strongly between groups.

Safety

  • No adverse events during testing were reported.
  • All athletes received cardiologist evaluation and ECG, and none reported recent overtraining symptoms; CrossFit injury and overtraining risks were discussed but not measured as incident events.