Heart rate variability to assess ventilatory thresholds: reliable in cardiac disease?

BACKGROUND: The first (VT1) and second (VT2) ventilatory thresholds are landmarks to tailor exercise rehabilitation in coronary artery disease (CAD) or chronic heart failure (CHF). Methods allowing VT1 and VT2 determination based on heart rate variability (HRV) have been proposed but not yet evaluated in these patients. DESIGN: To determine the heart rate (HR) associated with VT1 and VT2 by three methods of HRV analyses. METHODS: Fourteen CHF and 24 CAD patients performed an exercise test on a cycle ergometer (10 -W every minute until exhaustion). VT1 and VT2 were determined with the 'respiratory equivalent' method. HR at VT1 was determined with the standard deviation (SD) of R⊟R intervals (VT(SD)) and of the instantaneous beat-to-beat variability of the Poincaré plot method (VT(Poincaré)). HR at VT1 and VT2 was determined through a time-varying HRV analysis method (VT(TV1) and VT(TV2), respectively). RESULTS: HR at VT(SD) was significantly higher than HR at VT1. No significant differences were observed between HR at VT(Poincaré), VT(TV1), and at VT1, nor between HR at VT(TV2) and VT2. HR at VT(SD), VT(Poincaré), and VT1 were significantly correlated, but with a low r (2) value and a large mean HR difference. With the time-varying method, the mean HR difference was lower than 5% and the correlation coefficients were higher (especially for VT(TV2)). CONCLUSIONS: SD and Poincaré plot methods lead to substantial inaccuracy in HR estimates. The time-varying HRV analysis led to strong correlation coefficients and low limits of agreement. Therefore, this method may be a promising, low-cost tool for non-invasive assessment of the ventilatory thresholds in cardiac disease.

Exercise rehabilitation restores physiological cardiovascular responses to short-term head-out water immersion in patients with chronic heart failure.

PURPOSE: Rehabilitation programs increasingly involve immersed exercising, including inpatients suffering from severe cardiovascular diseases such as coronary artery disease (CAD) or chronic heart failure (CHF). The hemodynamic responses to short-term head-out water immersion are not well defined in these diseases. This study was aimed at evaluating (1) the cardiac and peripheral hemodynamic responses to short-term head-out water immersion in patients with CHF (n = 12) and CAD (n = 12) and (2) the effect of a rehabilitation program on these responses. METHODS: Wrist arterial tonometry was performed in the upright posture before and during immersion (1.30-m depth) once before and once after a 3-week rehabilitation program including gymnic water exercises. RESULTS: In patients with CAD, water immersion triggered a significant increase in stroke volume, cardiac output, and pulse pressure and a significant decrease in pulse rate, diastolic blood pressure, and systemic vascular resistances, both before and after the rehabilitation program. In patients with CHF, no significant immersion-linked changes in cardiovascular variables were observed before rehabilitation. However, after completion of the rehabilitation program, it was found that water immersion caused significant increases in stroke volume, cardiac output, and pulse pressure. CONCLUSION: In patients with CHF, this 3-week rehabilitation program restored the usual central responses to head-out water immersion (increase in stroke volume and cardiac output). In both patients with CHF and CAD, acute water immersion did not change arterial compliance.

[Isokinetic profile of knee flexors and extensors in a population of rugby players]. / Profil isocinétique des muscles fléchisseurs et extenseurs du genou chez une population de rugbymen.

OBJECTIVE: We aimed to assess the isokinetic profile of the flexor and extensor muscles of the knee within a population of rugby players. METHODS AND POPULATION: This was a descriptive study. The rugby players underwent bilateral isokinetic assessment of knee flexion and extension on a CON-TREX MJ isokinetic dynamometer functioning at four angular frequencies - 90, 120, 180 and 240 degrees/s - in a concentric manner. The isokinetic parameters were peak torque, mean power, and mean work in relation to weight and femoral bicep: quadriceps ratio. The population included 16 "Federal 1" (semi-professional) rugby players with mean age 25 years (range 20-33 years). The players were divided into two groups: "forward" players (props, hookers, second line, third line) and "back" players (scrum, inside, center, wing, tail). RESULTS: The values of the isokinetic parameters did not reveal use of a preferred limb. Consequently, peak torque and mean power were higher in forward players than back players, whereas back players showed a higher relative power throughout the isokinetic test. CONCLUSION: Among rugby players, forward and back players showed differences in several isokinetic parameters. Accurate knowledge of the equilibrium between the knee's effector muscles is important for stability of the joint, to not only minimize articular accidents but also pinpoint force imbalances, thereby preventing muscular lesions during the sports season.