Microcirculatory and Metabolic Responses during Voluntary Cycle Ergometer Exercise with a Whole-Body Neuromuscular Electrical Stimulation Device

Vigorous exercise increases blood viscosity and may pose a risk of cardiovascular events in patients with cardiovascular diseases. We recently reported that single-use of novel whole-body neuromuscular electrical stimulation (WB-NMES) can be safely applied in healthy subjects without adversely affecting blood fluidity. We performed a crossover study to explore the effectiveness and safety of a hybrid exercise with ergo-bicycle and WB-NMES; 15 healthy volunteers, aged 23–41 years, participated in this study. No arrhythmias were detected during the hybrid exercise and 20 min recovery, and although blood fluidity was transiently exacerbated immediately after both the exercise programs, in vivo parameters in the sublingual and nailfold microcirculation remained unchanged. There was a significant decrease in blood glucose and increase in lactic acid levels immediately after both exercise programs. Even with the same workload as the cycle ergometer exercise, the oxygen intake during the hybrid exercise remained higher than that during the cycle ergometer exercise alone (p < 0.05, r = 0.79, power = 0.81). Both the hybrid and voluntary cycle ergometer exercises transiently exacerbated blood fluidity ex vivo; however, microvascular flow was not adversely affected in vivo.

Pattern of the Heart Rate Performance Curve in Subjects with Beta-Blocker Treatment and Healthy Controls

(1): Heart rate performance curve (HRPC) in incremental exercise was shown to be not uniform, causing false intensity estimation applying percentages of maximal heart rate (HRmax). HRPC variations are mediated by β-adrenergic receptor sensitivity. The aim was to study age and sex dependent differences in HRPC patterns in adults with β-blocker treatment (BB) and healthy controls (C). (2): A total of 535 (102 female) BB individuals were matched 1:1 for age and sex (male 59 ± 11 yrs, female 61 ± 11 yrs) in C. From the maximum incremental cycle ergometer exercise a first and second heart rate (HR) threshold (Th1 and Th2) was determined. Based on the degree of the deflection (kHR), HRPCs were categorized as regular (downward deflection (kHR > 0.1)) and non-regular (upward deflection (kHR < 0.1), linear time course). (3): Logistic regression analysis revealed a higher odds ratio to present a non-regular curve in BB compared to C (females showed three times higher odds). The odds for non-regular HRPC in BB versus C decreased with older age (OR interaction = 0.97, CI = 0.94–0.99). Maximal and submaximal performance and HR variables were significantly lower in BB (p < 0.05). %HRmax was significantly lower in BB versus C at Th2 (male: 77.2 ± 7.3% vs. 80.8 ± 5.0%; female: 79.2 ± 5.1% vs. 84.0 ± 4.3%). %Pmax at Th2 was similar in BB and C. (4): The HRPC pattern in incremental cycle ergometer exercise is different in individuals receiving β-blocker treatment compared to healthy individuals. The effects were also dependent on age and sex. Relative HR values at Th2 varied substantially depending on treatment. Thus, the percentage of Pmax seems to be a stable and independent indicator for exercise intensity prescription.

Diagnostic usefulness of passive leg raising test for detection of heart failure with preserved ejection fraction compared to cycle ergometer exercise (invasive hemodynamic study)

Background Invasive diastolic stress test using cycle ergometer is gold standard for diagnosis of heart failure with preserved ejection fraction (HFpEF) by demonstrating elevation of left ventricular end diastolic pressure (LVEDP) during exercise. It is well known that passive leg raising increases preload and augments LVEDP in HFpEF patients. However correlation between passive leg raising induced increase of LVEDP and cycle ergometer exercise induced increase of LVEDP is not well established. Therefore we investigated whether passive leg raising test could substitute cycle exercise test for diagnosis of HFpEF. Method Forty-five patients with unexplained dyspnea and ejection fraction &gt;50% underwent invasive exercise test. After measuring baseline LVEDP in supine position using pigtail catheter through radial artery approach, LVEDP during passive leg raising was evaluated. Then exercise LVEDP was measured after 3 minutes of 20 watt supine cycle ergometer exercise. Patients with normal resting LVEDP &lt;16mmHg were enrolled. Patients with cycle ergometer exercise LVEDP &gt;26mmHg were classified as HFpEF and exercise LVEDP &lt;26mmHg were defined as noncardiac dyspnea. Results Among 45 patients with unexplained dyspnea with preserved EF, 30 patients with ergometer exercise LVEDP &gt;26mmHg were grouped as HFpEF and 15 patients with exercise LVEDP &lt;26mmHg grouped as noncardiac dyspnea (NCD). Resting LVEDP was higher in HFpEF than NCD (14±2mmHg vs 11±3mmHg, P=0.01) but there was substantial overlap (figure 1) showing poor differentiation power of resting LVEDP. Passive leg raising increased LVEDP in both HFpEF and NCD but this was more marked in HFpEF group than in NCD group with minimal overlap (24±4mmHg vs 17±2mmHg, P&lt;0.001) (figure 2). Passive leg raising LVEDP was well correlated with cycle ergometer exercise LVEDP (R2=0.60, P&lt;0.01). The best cutoff value for passive leg raising LVEDP to detect HFpEF was 20mmHg (sensitivity, 0.87; specificity, 1.00), giving an area under the curve of 0.93 (95% confidence interval, 0.80 to 0.99). Positive predictive value of passive leg raising LVEDP &gt;20mmHg for diagnosis of HFpEF was 96% and negative predictive value was 77%. Conclusion Passive leg raising induced augmentation of left ventricular end diastolic pressure (LVEDP) was well correlated with cycle exercise induced elevation of LVEDP in HFpEF patients. Passive leg raising test may be used for detecting HFpEF with good accuracy in substitution for cycle ergometer exercise test. Funding Acknowledgement Type of funding source: None

Skeletal muscle V̇o2 kinetics by the NIRS repeated occlusions method during the recovery from cycle ergometer exercise

Near-infrared spectroscopy (NIRS) has been utilized as a noninvasive method to evaluate skeletal muscle mitochondrial function in humans, by calculating muscle V̇o2 (V̇o2 m) recovery (off-) kinetics following short light-intensity plantar flexion exercise. The aim of the present study was to determine V̇o2 m off- kinetics following standard cycle ergometer exercise of different intensities. Fifteen young physically active healthy men performed an incremental exercise (INCR) up to exhaustion and two repetitions of constant work-rate (CWR) exercises at 80% of gas exchange threshold (GET; MODERATE) and at 40% of the difference between GET and peak pulmonary V̇o2 (V̇o2 p; HEAVY). V̇o2 p and vastus lateralis muscle fractional O2 extraction by NIRS (Δ[deoxy(Hb+Mb)]) were recorded continuously. Transient arterial occlusions were carried out at rest and during the recovery for V̇o2 m calculation. All subjects tolerated the repeated occlusions protocol without problems. The quality of the monoexponential fitting for V̇o2 m off-kinetics analysis was excellent (0.93≤ r2≤0.99). According to interclass correlation coefficient, the test-retest reliability was moderate to good. V̇o2 m values at the onset of recovery were ~27, ~38, and ~35 times higher (in MODERATE, HEAVY, and INCR, respectively) than at rest. The time constants (τ) of V̇o2 m off-kinetics were lower ( P < 0.001) following MODERATE (29.1 ± 6.8 s) vs. HEAVY (40.8 ± 10.9) or INCR (42.9 ± 10.9), suggesting an exercise intensity dependency of V̇o2 m off-kinetics. Only following MODERATE the V̇o2 m off-kinetics were faster than the V̇o2 p off-kinetics. V̇o2 m off-kinetics, determined noninvasively by the NIRS repeated occlusions technique, can be utilized as a functional evaluation tool of skeletal muscle oxidative metabolism also following conventional cycle ergometer exercise. NEW & NOTEWORTHY This is the first study in which muscle V̇o2 recovery kinetics, determined noninvasively by near-infrared spectroscopy (NIRS) by utilizing the repeated occlusions method, was applied following standard cycle ergometer exercise of different intensities. The results demonstrate that muscle V̇o2 recovery kinetics, determined noninvasively by the NIRS repeated occlusions technique, can be utilized as a functional evaluation tool of skeletal muscle oxidative metabolism also following conventional cycle ergometer exercise, overcoming significant limitations associated with the traditionally proposed protocol.