POWER OUTPUT AT THE HEART RATE TURN POINT IN RELATION TO METABOLIC STEADY-STATE CONDITIONS IN PATIENTS WITH CHD

Abstract

The aim of the study was to investigate the heart rate turn point (HRTP) in the time course of the heart rate performance curve (HRPC) in patients with CHD, and the relationship between the power output at the HRTP, in relation to the power output in metabolic and respiratory steady state (STST) vs. non-STST conditions. Two cycle ergometer tests were performed in 13 male CHD patients (age 64 ± 8; body mass 74 ± 12 kg; Ht: 170 ± 5 cm) and 17 male healthy subjects (HS) (age 58 ± 5; body mass 76 ± 11 kg; Ht: 176 ± 5 cm). 1. An incremental test (10 watts (W) every 1 min). The power output (W) and HR at the HRTP were determined. 2. STST-tests were performed. During the STST-tests the workload was increased by 10 W every min until power output of HRTP was reached. During the next 20 min a STST protocol was performed (and monitored via blood lactate measurements (LA)). In case of an increase in LA (more than 0.5 mmol.l−1) we performed another test 10 W lower. If LA stayed constant or decreased we increased power output by 10 W. There was no significant difference between the power output during STST and at the HRTP in CHD (STST: 112 ± 16 W; HRTP: 113 ± 18) or in HS (STST:155 ± 24 W; 161 ± 28 W). There was no significant difference between the HR at the HRTP and during the first 5 min of STST in CHD (HRTP: 124 ± 16; STST123 ± 12 BPM) or in HS (HRTP:137 ± 13; STST 139 ± 10 BPM). However, HR between the last 5 min of STST and HRTP was different (CHD: 132 ± 14 BPM, HS: 151 ± 13 BPM. To define metabolic and respiratory steady-state intensities in CHD and HS the determination of the HRTP is a simple and valid method. Since the HR increased during STST conditions it is better to use the absolute power than the HR to describe steady-state intensities.