Heart Rate and Perceived Effort do not Regulate Pacing During a Cycling Time Trial

Abstract

It is difficult to determine why individuals vary their pacing during exercise. However there is theory to suggest that during exercise the perception of effort is maintained constant by peripheral feedback that modulates pace. PURPOSE: To determine if perceived effort or heart rate regulate pacing during a 576 kJ cycling time trial (TT). METHODS: Nine highly trained cyclists served as subjects for this investigation (VO2max 62.5±5.5 mL·Kg−1·Min−1, Height 180.4±5.0 cm, Weight 73.0±7.5 Kg). Prior to completing the TTs each subject underwent a graded exercise test to determine VO and peak aerobic power (Wmax). The TT was conducted on the Lode cycle ergometer in linear mode. The linear factor was adjusted based on the subjects Wmax to approximate 70% W at 90 rpm. Subjects then completed a 576 kJ TT as fast as possible altering PO by altering cadence. 576 kJ was chosen as it closely approximates 20 Km. Heart rate (HR), power output (PO), and ratings of perceived exertion (RPE) was measured every 28.8 kJ (∼1 Km). HR, PO, and RPE were each analyzed using a one-way ANOVA with repeated measures. Specific differences were determined using a Tukey's post hoc procedure. RESULTS: PO during the TT fell significantly at the 4th Km (277±39 Watts) from the 1st Km (321 ±75 Watts) and then did not change significantly from the PO at the 4th Km. RPE rose significantly at the 4th Km (13±3.13) from the 1st Km (10.3± 3.11), then rose significantly at the 8th Km (16±2.37) and rose significantly again at the 19th and 20th Km (19±1.12 and 19±1.22). HR rose significantly at the 3rd Km (167±15 bpm) compared to the 1st Km (159±15 bpm) and did not change significantly until the 19th and 20th Km (176±12bpm, 180±1 2 bpm respectively) CONCLUSIONS: The significant changes in RPE and HR without corresponding changes in PO suggest that RPE and HR do not regulate pacing strategy during the TT.