Abstract
The purpose of this study was to determine the effects of constant-load exercise performed above and below TH1 on the magnitude of HR drift, a component of CV drift. Data was collected from 9 trained cyclists who have been cycling 3-5 hours per week for greater than 1 year. Subjects reported to the laboratory on three occasions. The first visit consisted of a maximal exercise test and two power detection rides. These were conducted to determine the workloads for the remaining two visits. Visits 2 and 3 consisted of rides to fatigue at an exercise intensity that elicited a VO2 that was 5% below TH1 and at the midpoint of TH1 and TH2 (midTH). Fatigue was determined when subjects could no longer maintain a cadence within 5 rpms of their self-selected cadence. Heart rate was recorded every minute; VO2 was collected continuously for the first 5 minutes then every 10 minutes for 2 minutes. Blood pressure and RPE were recorded every 10 minutes. Results Subjects displayed a significant main effect for intensity. Average HR during the -5%TH was 159±13 bpm and was significantly lower than the midTH trial with a HR of 167±15 bpm (p=.002). There was also a significant main effect of duration (p=.000). Tukey’s post hoc analysis revealed a significant HR rise from 156±14 bpm at 20% TTF to 161±14 bpm at 40% TTF (p=.000). Heart rate rose again from 40% TTF to 165±15 bpm at 60% TTF (p=.002). Heart rate did not rise again until 100% TTF (170±15bpm p=.04) (see Figure 2) . The drift in HR represents a 9.1% change in HR in the -5%TH and an 8.9% in the midTH trial. Despite the statistical significance for both intensity and time, there was not a statistically significance interaction effect (p=0.645). HR was significantly different for intensity and time but there was not statistical significance for the interaction of intensity vs. time. The magnitude of HR drift above and below TH1 was nearly the same percent change. Prior CV drift studies utilizing percentage of maximal oxygen consumption as the prescription of exercise yielded similar magnitude of drift. Future CV drift studies can design methods like traditional studies.