Optimization of Maximal Rate of Heart Rate Increase Assessment in Runners

ABSTRACT

Purpose: Correlations between fatigue-induced changes in exercise performance and maximal rate of heart rate (HR) increase (rHRI) may be affected by exercise intensity during assessment. This study evaluated the sensitivity of rHRI for tracking performance when assessed at varying exercise intensities. Method: Performance (time to complete a 5-km treadmill time-trial [5TTT]) and rHRI were assessed in 15 male runners following 1 week of light training, 2 weeks of heavy training (HT), and a 10-day taper (T). Maximal rate of HR increase (measured in bpm·s⁻¹) was the first derivative maximum of a sigmoidal curve fit to HR data recorded during 5 min of running at 8 km·h⁻¹ (rHRI_8km·h⁻¹), and during subsequent transition to 13 km·h⁻¹ (rHRI_{8–13km·h⁻¹}) for a further 5 min. Results: Time to complete a 5-km treadmill time-trial was likely slower following HT (effect size ± 90% confidence interval = 0.16 ± 0.06), and almost certainly faster following T (–0.34 ± 0.08). Maximal rate of HR increase during 5 min of running at 8 km·h⁻¹ and rHRI_{8–13km·h⁻¹} were unchanged following HT and likely increased following T (0.77 ± 0.45 and 0.66 ± 0.62, respectively). A moderate within-individual correlation was found between 5TTT and rHRI_8km·h⁻¹ (r value ± 90% confidence interval = –.35 ± .32). However, in a subgroup of athletes (n = 7) who were almost certainly slower to complete the 5TTT (4.22 ± 0.88), larger correlations were found between the 5TTT and rHRI_8km·h⁻¹ (r = –.84 ± .22) and rHRI_{8–13km·h⁻¹} (r = –.52 ± .41). Steady-state HR during rHRI assessment in this group was very likely greater than in the faster subgroup (≥ 1.34 ± 0.86). Conclusion(s): The 5TTT performance was tracked by both rHRI_8km·h⁻¹ and rHRI_{8–13km·h⁻¹}. Correlations between rHRI and performance were stronger in a subgroup of athletes who exhibited a slower 5TTT. Individualized workloads during rHRI assessment may be required to account for varying levels of physical conditioning.

KEYWORDS:

• Athletic performance
• autonomic nervous system
• cardiovascular control
• overreaching

Acknowledgments

The authors thank Polar Electro Oy for providing the HR monitors for the study and the South Australian Sports Institute for providing facilities for data collection.

Declaration of Interest

The University of South Australia has had a patent on the rHRI technology described in this manuscript granted in the United States (US2013/0172764/A1), and patents are pending in Australia and Europe. Researchers Davison and Buckley are employees of the university, and Thomson is an affiliate of the university.

Researcher Karavirta is an employee of Polar Electro Oy.

Additional information

Funding

This work was supported by a Linkage Grant from the Australian Research Council (LP140101013, 2013), which was not involved in the study’s design nor the collection, analysis, and interpretation of data, the writing of the report, or the decision to submit the article for publication.