Heart Rate Does Not Accurately Predict Metabolic Intensity During Variable-Intensity Roller Skiing or Cycling

Area of Science:

• Exercise Physiology
• Sports Science
• Biophysics

Background:

• Accurate prediction of metabolic rate (MR) and oxygen consumption (V˙O2) is crucial for training and performance monitoring in endurance sports.
• Heart rate (HR) and power output (PO) are commonly used surrogates for metabolic intensity, but their accuracy during variable-intensity exercise requires critical evaluation.

Purpose of the Study:

• To assess the predictive utility of HR and PO for MR and V˙O2 during variable-intensity roller skiing and cycling.
• To compare the accuracy and consistency of HR- and PO-based predictions across different exercise intensities.

Main Methods:

• National-level cyclists and cross-country skiers underwent a preliminary session to establish V˙O2max.
• A variable-intensity protocol involved alternating moderate (70% V˙O2max) and high (90% V˙O2max) intensity stages.
• Linear regressions (HR-MR, HR-V˙O2, PO-MR, PO-V˙O2) were derived and used to predict metabolic measures during the protocol, with mean differences and 95% limits of agreement (LOA) calculated.

Main Results:

• HR-based predictions showed minimal bias but wide LOA, overestimating MR/V˙O2 during moderate intensity and underestimating during high intensity.
• PO-based predictions exhibited tighter LOA, indicating greater consistency, despite a larger mean bias.
• These patterns were consistent for both roller skiing and cycling.

Conclusions:

• HR demonstrates limited utility for predicting metabolic intensity during variable-intensity roller skiing and cycling due to significant variability (wide LOA).
• PO provides a more consistent prediction of metabolic intensity, characterized by tighter LOA.
• PO is suggested as a superior predictor of metabolic intensity compared to HR, especially when preliminary testing includes longer exercise durations.