Peak Exercise Intensity Research Articles

Effects of percutaneous transluminal mitral valvuloplasty on plasma catecholamine levels during exercise

Elevation of plasma catecholamine levels during exercise in patients with mitral stenosis correlated with the severity of the disease. We investigated the plasma norepinephrine changes in six patients before and after percutaneous transluminal mitral valvuloplasty (PTMV) during continuously graded ergometer exercise. Peak exercise intensity was increased from 65.8 W to 87.5 W after PTMV. Plasma norepinephrine level at 60 W workload intensity was decreased from 2308 +/- 864 pg/ml to 841 +/- 233 pg/ml after PTMV (p < 0.05). We concluded that PTMV decreased the plasma norepinephrine level during exercise in the patients with mitral stenosis. Percutaneous transluminal mitral valvuloplasty is a novel procedure for the improvement of symptoms in patients with mitral stenosis.

Locomotor-respiratory coupling develops in novice female rowers with training

The purpose of this study was to investigate the hypothesis that locomotor-respiratory coupling (LRC), or entrainment of breathing, develops in the sport of rowing as a result of training. We prospectively evaluated exercise responses over an 8 month training session (October to May) in 12 female subjects who were members of the Dartmouth College novice rowing team. Progressive, incremental exercise testing was performed on the variable-resistance rowing ergometer (Concept II, Morrisville, VT). To relate the pattern of breathing to the mechanics of rowing, the catch and finish of each rowing stroke during the last 30 s of each minute of exercise were marked on the strip chart paper that recorded inspiratory flow measured by using a heated pneumotachograph. Age was 18 +/- 1 yr (mean +/- SE); weight was 67.5 +/- 2.1 kg. Peak oxygen consumption (VO2) increased by 10% from October (40.8 +/- 0.6 ml.kg.min-1) to May (P less than 0.001). Chi-square goodness-of-fit analysis was used to assess whether the proportion of inspirations occurring in each of four quadrants of circle plots representing repetitive rowing strokes exercise intensities of 100 watts (W) and peak VO2 were random or corresponded to a regular pattern of breathing. Although 5 of 12 subjects demonstrated LRC at exercise of 100 W in October, there was no significant change at this submaximal intensity over the training season. Only 2 of 12 subjects showed LRC at peak exercise in October, but there was a significant increase (P = 0.003) in the number of subjects who entrained breathing in Jan (10/12) and May (8/12).(ABSTRACT TRUNCATED AT 250 WORDS)

A Mathematical Model of the Cardiac Chronotropic Response to Exercise

A mathematical model was developed from data collected from 410 normal subjects in order to describe the normal cardiac Chronotropic response to exercise. Subjects were examined by treadmill testing on either the Bruce protocol (189 patients) or the Chronotropic Assessment Exercise Protocol (CAEP) (221 patients), The CAEP, designed specifically for chronotropic assessment, is structured to collect heart rate data at submaximal as well as peak exercise intensities. Analysis of these subjects, without evidence of medical illness or cardiac medications, found the heart rate response to be a function of exercise intensity, age, resting heart rate, and maximal functional capacity. Heart rate reserve (HRR) was defined as the difference betii'een maximal predicted heart rate (MPHR) and resting heart (HRrest). Metabolic reserve was defined as the difference between the maximally achieved workload (METSpeak) and the workload at rest (METSrest). The Bruce and CAEP data provided a statistically linear and identical response of the form y = mx + b. The Bruce equation was %HRR = 0.95 ×%MR + 3.4 and the CAEP equation is %HRR = 0.94 ×%MR + 4.55. The following formula describes the normal predicted heart rate for an individual at some submaximal stage of exercise: HRstage= [(220 ‐ age ‐HRrest) × (METSstage ‐ 1)/(METSpeak ‐ 1)] + HRrest. We conclude that the cardiac chronotropic response can be modeled as a simple linear mathematical function of exercise intensity, age, resting heart rate, and maximal functional capacity, and is independent of type of treadmill exercise protocol in normal subjects.

Immediate effects of milrinone on metabolic and sympathetic responses to exercise in severe congestive heart failure

A randomized, double-blind, placebo-controlled protocol was used to determine whether milrinone exerts an immediate effect on exercise performance in patients with severe congestive heart failure. In each of 14 patients with New York Heart Association class III or IV congestive heart failure, intravenous milrinone (mean 57 ± 5 μg/kg) and placebo were randomly administered just before maximal progressive upright cycle ergometry. The duration of exercise was significantly longer with milrinone than with placebo treatment (placebo 11.0 ± 0.6 minutes, milrinone 12.5 ± 0.9 minutes, p = 0.01). Compared with placebo, milrinone caused a higher peak oxygen uptake (placebo 10.8 ± 0.6 ml/kg/ min, milrinone 12.4 ± 0.7 ml/kg/min, p = 0.001) and oxygen uptake at the anaerobic threshold (placebo 7.8 ± 0.4 ml/kg/min, milrinone 9.2 ± 0.4 ml/kg/min, p = 0.001). At peak exercise intensity, systolic blood pressure (placebo 119 ± 5 mm Hg, milrinone 131 ± 5 mm Hg, p = 0.001) and heart rate (placebo 114 ± 5 beats/min, milrinone 126 ± 6 beats/min, p = 0.001) were both increased with milrinone. Likewise, at matched submaximal exercise intensities, heart rate (placebo 111 ± 19 beats/min, milrinone 117 ± 20 beats/min, p < 0.05) and systolic blood pressure (placebo 116 ± 19 mm Hg, milrinone 121 ± 19 mm Hg, p = 0.04) were higher with milrinone; plasma norepinephrine (placebo 1,692 ± 208 mg/liter, milrinone 1,320 ± 216 ng/liter, p = 0.05) and blood lactate concentrations (placebo 2.2 ± 0.2 m M, milrinone 1.9 ± 0.2 m/ M, p < 0.05) were lower. These data indicate that the administration of milrinone acutely causes an improvement in maximal exercise performance and the metabolic response to submaximal exercise.