ISSN:
1439-6327
Keywords:
Heart rate threshold
;
Lactate turn point
;
Constant load exercise
;
Cycle ergometer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The aim of this study was to investigate heart rate threshold (HRT) related exercise intensities by means of two endurance cycle ergometer tests using blood lactate concentration. [La], pulmonary ventilation ( $$\dot V$$ E), oxygen uptake ( $$\dot V{\text{O}}_{\text{2}} $$ ), heart rate (HR) and electromyogram (EMG) activity of working muscle. Firstly, 16 healthy female students [age, 21.4 (SD 2.8) years; height, 167.1 (SD 5.1) cm; body mass 62.7 (SD 7.1) kg] performed an incremental exercise test (10 W each minute) on an electrically braked cycle ergometer until they felt exhausted. The HRT and lactate turn point (LTP) were assessed by means of computer-aided linear regression break point analysis from the relationship of HR or [La] to power output. No significant difference was found between HRT and LTP for all the variables measured. Secondly, two endurance tests (ET) of 20 min duration were performed by 7 subjects. The first (ET I) was performed at an exercise intensity which was about 10% lower than the power output at HRT [61.2 (SD 3.1) % maximal oxygen uptake ( $$\dot V{\text{O}}_{\text{2}} $$ max)], the second (ET II) at an exercise intensity about 10% higher than the power output at HRT [79.2 (SD 3.4) % $$\dot V{\text{O}}_{\text{2}} $$ max]. The parameters measured showed a clear steady state in ET I. All mean values were lower than values at HRT [power, 138.7 (SD 18.9) W; HR, 172.1 (SD 4.7) beats·min−1; $$\dot V{\text{O}}_{\text{2}} $$ , 2.2 (SD 0.3) l·min−1; $$\dot V$$ E, 54.0 (SD 9.1) l·min−1; [La], 3.7 (SD 1.1) mmol·l−1; EMG, 81.1 (SD 24.0) μV] except HR which was the same. No parameters showed a steady state (except EMG activity) in ET II. No subject was able to maintain the exercise for the whole 20 min in ET II [mean time to cessation of the exercise was 10.4 (SD 3.7) min]. At the end of ET II all variables measured were significantly higher (P 〈 0.05) than in ET I (except EMG activity) [HR, 184.3 (SD 5.2) and 172.1 (SD 8.7) beats·min−1; $$\dot V$$ E: 75.2 (SD 11.7) and 49.6 (SD 8.4) l·min−1; $$\dot V{\text{O}}_{\text{2}} $$ , 2.9 (SD 0.7) and 2.1 (SD 0.5) l·min−1; [La], 7.0 (SD 1.8) and 3.3 (SD 2.2) mmol·l−1; EMG, 86.3 (SD 28.7) and 75.9 (SD 21.5) μV]. Although no exercise, at HRT exactly was performed, we assume that maximal steady state lay in between ET I and ET II.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00609405
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